NL8004599A - SYSTEMS AND METHODS FOR MEASURING DRAWING IN A BOREHOLE. - Google Patents

Description

.> *

Systems and methods for measuring in a borehole during drilling.

The invention generally relates to measurements while drilling a borehole into the ground, and more particularly to systems, devices and methods using hydraulic shock waves in the mud column for transmitting signals to the earth's surface. , which represent one or more downhole parameters. The invention also relates to systems and methods for detecting these signals in the presence of disturbing noise.

The invention relates to systems for transferring data from the bottom of a well bore to the surface during well drilling.

It has long been recognized in the petroleum industry that downhole data acquisition during well drilling provides valuable information that may be of interest to the drill master. Information such as the pure weight on the bit, the slope and course of the borehole, the end face of the tool, the fluid pressure and temperature at the bottom of the hole, and the radioactivity of substances surrounding the drill bit or by the drill bit are found, all of the quantities of interest are provided to the drill master. A number of known proposals for measuring these quantities during drilling and transferring these quantities to the ground surface have been made. Various transfer systems have been proposed in the prior art to perform these. For a description of the prior art, reference is made, for example, to the i 800 45 99 Λ * * 2

U.S. Patents 2,787,795, 2,887,298, 4,078,620, 4,001,773, 3,964,556, 3,983,948, and 3,791,043. Perhaps the most promising in a practical sense of these known proposals is that of signaling by pressure pulses in the coil. Various methods have been proposed in the prior art to produce such flushing pulses by controlled restriction of the flushing flow cycle through a flow restricting valve, which is suitably located in the main flushing flow or by a bypass valve, fitted between the inside of the drill string (high pressure side) and the annulus around the drill string (low pressure side).

It has been proposed in the prior art to produce mud pressure pulses by valves that limit mud flow in the drill string or divert a portion of the flow to the low pressure area in the annulus around the drill string. Such valves are necessarily slow, because when used in the drill string, the valve must control very large flushing volumes, and when used to control a circulation, the valve due to the very large pressure differences, necessarily also a slow motor-operated valve is. Such a motor-operated valve, which is arranged, for example, between the inside of the drilling column and the annular space, produces, in response pp, a well measurement, slow decreases and slow increases in the flushing pressure. These are then observed on the ground surface.

In order to better understand the operation of a slow-acting, motor-operated valve, as proposed in the prior art, reference is made to Figure 1A which illustrates the opening and closing of such a valve as a function of time. Referring now more particularly to FIG. 1A, the X axis therein represents time t, the Y axis representing the degree of opening of the valve R.

R = g— (1) o where Sq is the total area of the opening, and S (t) is the area, 800 4 5 99 _ t. ('* p · 3 which is open at the moment t during the opening or closing of the valve. So when R = 0 the valve is closed, when when R = 1 the valve is fully opened. The moments related to the operation of the valve are as follows: (v) 5 t = OA, the moment when the valve starts to open, 5L Jl t ^ V ^ = OB ^, the moment when the valve is fully open, - OCj, the moment when the valve starts to close, and 10 t ^ = OD ^, when the valve is completely closed.

The time course: 15 T (V) = t / V) - t (v) = tjv) - t (v) (2) a o a d c (v) T & is referred to as the "moment of opening or closing the valve".

The time course: 20 - "W -, 3, T ^ V) is referred to as the" open flow moment ". The total duration of valve operation is therefore:, e T <V) = 2T (V) + T ™ (4) 25 tab

In the foregoing proposals, = 1s, = 2s, so that a (v) therefore the total time of valve actuation T = 4s.

This relatively slow opening and closing of the valve accordingly produces 2q slow decreases and increases in soil flushing pressure (see Fig. 1B).

It can be seen that the purge pressure decreases from the usual value of, for example, 6.9 MPa (when the valve is closed) to the lowest value of 5.2 MPa (when the valve is opened). The moments 8004599 • Η- 4 related to these observed pressure changes are as follows: (s) t ^ = OE ^, the moment when the flushing pressure begins to decrease from the usual level of 6.9 MPa, (s) t „ , = OR ,, the moment when the flushing pressure reaches the lowest lb 1 level of 5.2 MPa, and is held at this level (s) until the moment of t. = 0G ,, (s) 1C 1 t ^ c = OG ^, the moment when the flushing pressure starts to increase 10, and (s) tj ^ = OH ^, the moment when the flushing pressure is at the usual 6,9 MPa level reached.

(s) (g) (s)

Thus, the pressure decreases during the time course = t ^ - t ^ a, then remains the same during the time course (s) _ (s) (s) T2 Zlc "Clb 611 15 then increases from the reduced value to the usual level ( s) (s) (s) over the time course = t ^ - t ^. The total duration of the purge flow through the bypass valve for a single actuation of the valve is thus τω. t (s, + t's) + t's) (si 20 t 1 2 3

The quantities in Figure 1A are provided with the top letter "v" to indicate that these quantities refer to the operation of the valve located below the surface of the ground. In contrast, the magnitudes in FIG. 1B are provided with the top "s" to indicate that these magnitudes relate to measurements on the surface of the soil. This distinction between the quantities labeled "v" and those marked "s" is essential in order to fully understand some of the particular features of the invention. It is essential in this specification to distinguish between the cause and the effect or, in other words, between the "downhole" phenomena near the valve and those at the detector on the surface of the ground.

An essential feature of the already proposed device is based on the relations: 35 800 4 5 99 5 t ί if- T (S) = T (V) (6) 1 Sl T, (s) = T <v) (7 )

Δ D

5 T <S, = T <V) (8) J d

These relations show that the time of the decrease or increase of the pressure on the surface of the soil is the same as the corresponding time of the opening and closing of the valve, and that the time during which the pressure is essentially constant (at a reduced level) is the same as the length of time during which the valve is fully open. In other words, the decrease and subsequent increase of the flushing pressure at the ground surface is precisely in accordance with the opening and closing of the valve. This state, as expressed by relations (6), (7) and (8) is referred to in the description as relating to a "slow pressure change regime".

The slow pressure change regime, as proposed in the prior art, is not suitable for distance measurement during drilling, especially when measuring a number of "downhole" parameters. Once a first parameter has been measured, coded, transferred to the surface, and then decoded, the wellbore may be deepened, and the second parameter may no longer be available for measurement. Relatively long periods of time are required to convert the measured data into a form suitable for sensing and recording. Obtaining a profile of the well as a whole is lengthy and time consuming. Furthermore, various interfering effects, such as pulses from the mud pump and interference associated with different drilling operations, create additional difficulties. A slow-acting, motor-operated valve, as proposed in the prior art, is believed to be insufficient to meet present practice requirements.

Part of the objects of the invention are accomplished by using hydraulic shock waves 80 0 4 5 99 6 * 2 Μ ~ to measure well profile information remotely during drilling. These shock waves are produced by a very fast-acting (practically instantaneous for all practical purposes) bypass valve, placed between the inside of the drill string and the annulus around the drill string. When the bypass valve opens suddenly, the pressure falls in the immediate vicinity of the valve, which pressure then returns to normal almost instantly, and a strong negative impulse is generated, and when the bypass valve closes suddenly, a strong positive impulse is generated. The spring force of the wash column is used to assist in generating and transmitting such shock waves. The phenomenon is analogous to the well-known water hammer already experienced in hydraulic transmission systems. See, for example, John Parmakian on "Water Hammer Analysis", Prentice Hall, Inc., New York, N.Y.

15 1955 or V.L. Streeter and E.B. Wylie on "Hydraulic Transients"

McGraw-Hill Book Co., New York, N.Y.).

Important features of the invention, such as generating and sensing hydraulic shock waves, are shown schematically in Figures 2A and 2B. The graph in Fig. 2A shows the opening and closing of a fast acting shock wave producing valve, the graph of Fig. 2B showing pressure changes observed at the ground surface, which pressure changes are due to the operation of the valve, as in Fig. 2A. The symbols in fig. 2A

have a similar meaning to the corresponding symbols in Fig. 1A. However, the time scales in Figures 1A, 1B, 2A and 2B have been significantly distorted to facilitate description and clarity of explanation.

The first thing to note when looking closely at FIG. 2A is that the opening and closing times of the present valve by a number of orders of magnitude are shorter than the corresponding times obtained by the motor-operated valve as discussed in conjunction with Figure 1A. In the (v) construction already proposed (as in Fig. 1A), T = 1 s, a (v) where according to the invention, as in Fig. 2a, t = 5 ms.

9.

A similar situation applies for the time lapse during which 800 45 99 7 t * "& a valve remains open. In the construction already proposed (such as (v) (v) in fig. 1A) = 2 s, wherein in fig. 2A, = 100 ms For all purposes, the opening and closing of the valve in Figure 2A can be considered instantaneous or near instantaneous.

5 The rapid or near instantaneous opening and closing of the valve has a significant and far-reaching impact on the behavior of distance measuring systems when measuring during drilling. The pressure changes observed on the soil surface according to the invention (fig. 2B) show no resemblance to the 10 pressure changes obtained by means of a slow-acting valve (fig. IB). Reference has already been made to the presence of equations (6), (7) and (8), which represent relations between those shown in FIG.

1A shows events, and those shown in FIG. 1B. Analogous relations do not exist between the events 15 in Figures 2A and 2B.

As shown in Figs. 1A and 1B, opening the valve produces a corresponding decrease in soil surface flushing pressure, conversely closing the valve produces a corresponding increase in pressure.

It is emphasized that the opening of the valve in the prior art produces a single event, viz. A reduction in pressure, the subsequent closing of the valve producing another single event, viz. An increase in the pressure. According to the invention, on the other hand, the rapid opening of the valve, as in Figure 2A, produces two events: a rapid decrease and then an increase in pressure (negative pulse M, as in Figure 2B). This is in contrast to the case shown in Figures 1A and 1B, where the opening and subsequent closing of the valve is required to produce a decrease and a subsequent increase in pressure.

Furthermore, the rapid closing of the valve, as in Figure 2A, produces an increase and a subsequent decrease in the purge pressure (positive pulse N, as in Figure 2B). Such an increase and subsequent pressure drop does not occur with the devices proposed in the prior art. According to the invention 800 4 5 99 8 * 1 τ, two shock waves are produced by a single actuation of the valve. A waveform, as shown in Fig. 2B, which includes both a negative and a positive pulse, is referred to in the description as a "valve wave." Valve pulses associated with a valve wave have an initial velocity of a few tens of MPa / s and a short duration.

It is important to note the speed of the phenomena associated with the observed valve waves. The one shown in Fig. 2B

related moments are as follows: (s) 10 t ^ = OK, the moment the negative pulse M appears, (s) t ^ = OL, the moment the negative pulse M decays, (g) t ^ = OM , the moment of appearance of the positive pulse N, (s) t. = ON, the moment when the positive pulse N decays.

4 (s)

The time course, which represents the "length" of the negative pulse M (or the positive pulse N) is 100 ms, the time (s) from the appearance of the negative pulse M to the appearance of the positive pulse N , equals 110 ms. The total duration of the flow, as shown in Fig. 2B, that is: T (s) _ T (s) + T (s) (9) unm is thus 210 ms, the total duration of the flow, as (s) 25 is shown in Fig. 1B (see equation 5), T = 4 s.

The graphs in Figures 1A, 1B, 2A and 2B are simplified and idealized by eliminating wrinkles and other external effects. It should also be noted (see Fig. 2b) that the bypass valve is at least partially open during the time course (s) (s) from t ^ to t ^. During this period of time, a slow pressure drop takes place, which is lifted at the observation point by an appropriate screen. Such a pressure drop is shown in the graph of FIG.

2B not shown.

It should also be noted that the numerical values calculated on FIGS. 2A and 2B are only given as an example.

800 45 99 9 τ * 'if

These values should not be construed as limiting the invention to any given example.

The operation as set forth in connection with Figures 2A and 2B is indicated as relating to a "hydraulic shock wave regime". Thus, a distinction is made between the regime of hydraulic shock waves, such as in Figs. 2A and 2B, and the regime of slow pressure changes, such as in Figs. 1A and 1B.

By providing a regime of hydraulic shock waves, a distance measurement system is obtained, by means of which large amounts of information can be transferred per unit time. Such a system is considerably better adapted to satisfy the current practical requirements than the system, which is based on the regime of slow pressure changes.

The present valve is operated by the output of one or more sensing means for sensing one or more "downhole" parameters in the substrate near the drill bit. A single measurement of each parameter is represented by a sequence of valve waves. Each valve wave corresponds to a single opening and closing of the valve.

The sequence of valve waves (representing the useful signal) is usually mixed with various interfering signals, such as the signals produced by the operation of the pump and other drilling operations, when observed at the ground surface. In a conventional drilling rig, a large pump located on the surface 25 is used to pump mud through the drill string down through the bit and back to the surface through the annulus between the drill string and the well bore. According to the invention, the disturbing consequences resulting from the pump are eliminated by processing, taking into account the intermittent occurrence of these consequences. Other consequences associated with drilling operations usually appear as a noise signal, which includes a relatively wide frequency spectrum. In some cases, this noise signal is white noise and in other cases it deviates significantly from white noise. A 35 digital screen system, which has a leveling screen or an impulse forming 800 4 5 99 10 - »Λ.

* sieve or a silent sieve may be used to widen the noise signal. The equalizing sieve maximizes the signal-to-noise ratio at the receiving point, with a pulse-forming sieve minimizing the mean difference between a desired output and the actual output, and a silent sieve transforming the useful signal by contracting it into a signal of sufficient magnitude to distinguish it against a background noise. A special technique is used for adapting these screens to the purposes of the invention. Such a technique requires storing and then displaying two comparison signals. The first comparison signal is a wavelet produced by opening and closing the valve, the second comparison signal representing noise due to the drilling operations. Observation and storage of the first comparison signal is obtained by removing weight on the bit and stopping the actual drilling (but keeping the mud pumps in normal operation). Thus, a signal is obtained which is free from the ambient noise. Observation and storage of the second comparison signal is obtained during drilling for a period of time that the valve is closed. An adapted digital computing system is configured to receive the data representing one or both of the comparison signals, and derives a memory operation from the data for the equalizing screen, for the pulse-forming screen or for the silent screen.

One aspect of the invention relates to improvements in bi-stable operation of the valve assembly 40 of the special distance measuring tool 50. Another aspect of the invention relates to the provision of a special hydraulic actuable mechanical device which intermittently moves the valve 40 positively to the closed position. In addition, an electrical system is provided which excludes the operation of the valve 40 in the event of an electrical fault in the downhole device.

8 0 0 4 5 99 11 r. *

<P

Further aspects of the invention pertain to improvements in connection with the power source 95 and power control 104 of the special distance measurement tool 50. These improvements serve to significantly increase the number of satisfactory valve actions that can be achieved without recharging or replacing a downhole battery.

Another aspect of the invention relates to improvements in pulse time codes, in which only short pulses of substantially equal duration are transmitted, and the time elapses between successive pulses are the measurements of the magnitude of the parameter concerned. In addition, a system is described for improving the accuracy and accuracy in transmitting and sensing flush pressure pulses generated in the "downhole" equipment, which system includes generating in the "downhole" equipment, as well as transmitting a group of at least three dissimilarly spaced flushing pressure pulses for each information carrying single impulse, and providing the appropriate equipment on the surface for sensing and translating the transmitted impulse groups.

The invention is further elucidated with reference to the drawing, in which: Fig. 1A schematically shows the operation of a known slow-acting valve, Fig. 1B schematically shows pressure changes which are observed on the ground surface and which are the result of the operation of the valve shown in Figure 1A, Figure 2A schematically shows the operation of the present fast-acting valve, Figure 2B shows schematically pressure changes observed on the ground surface and the effect of the action of the valve shown in Figure 2A, Fig. 3 schematically and generally depicts a well drilling assembly equipped for simultaneously drilling and performing measurements in accordance with certain aspects of the invention, Fig. 4A schematically shows a portion of the well equipment, 800 45 99 12 - * 1 ï The particular present tool for distance measurement, Fig. 4 schematically shows part of the equipment of Fig. 4A, Fig. 5 schematically and in more detail. electronic 5 processing assembly comprised by the broken rectangle in FIG. 4A, FIG. 5B schematically shows an energy source including a device for charging and discharging a capacitor to provide the energy required to operate the valve 10 from the special distance measuring tool, Fig. 5C schematically shows an electronic circuit, which can be used to automatically cut off the power control for the valve of the special distance measuring tool, Fig. 5D and 5E are graphs to help when disabling the automatic cutting of the power control of the signaling valve, Figs. 6A, 6B and 6C schematically illustrate the operation of the hydraulic "automatic closing" of the signaling valve, Fig. 6D shows the construction of the 6A, 6B and 6C show apparatus, Fig. 6E schematically shows an electronic "fail-safe" apparatus which can be used with the signaling class ep, fig. 7A schematically shows the housing construction for the special distance measuring tool, fig. 7B schematically shows the cross-sectional shape of centering members which can be used with the construction according to fig. 7A, fig. 7C schematically shows special connecting means. are used to connect the parts of the housing part according to Fig. 7A, Fig. 8A-8E show graphs showing pressure changes, as measured on the ground surface and corresponding (v) (v) with different values of T and of T Fig. 8F shows an accurate representation of the pressure signal 800 4 5 99 13 r * * t sewing, which depicts a valve wave, as received on the surface from the depth of 2940 meters in a practice drilled petroleum product. pit.

Fig. 9 schematically shows a conventional overhead equipment 5 to be used in conjunction with a downhole pressure pulse signal device, which equipment includes a leveling screen for removing background noise when it is white.

Fig. 10A contains three graphs showing three components of a signal sensed at the top of the borehole, the 10 components representing an information carrying signal, pump noise or, in the case of a number of pumps used in tandem, the noise of the group pumps, and represent background noise, Fig. 10B contains three graphs, which respectively represent the delayed information carrying signal, the delayed pump noise and the delayed background noise, Fig. 10C contains two graphs, respectively, showing the differences of the corresponding graphs in Figs. 10A and 10B FIG. 10D shows a function representing the output of a digital screen or reciprocal means, which function is substantially similar to that representing the information carrying signal in FIG. 10C, FIG. 10E depicts a function similar to that of FIG. 10D, but with an appropriate time lag in time Figure 10F shows a function like that in Figure 10E, but reversed in time, Figure 10G results from a comparison of the graphs of Figures 10D and 10F, and shows moments corresponding to impulses. , which coincide in these graphs, Fig. 11 schematically shows certain operations performed by a digital screen, Fig. 12 schematically shows a device for storing an information-carrying signal or storing a noise signal, Fig. 13 schematically a part of the overhead equipment, which includes a noise canceling correlator, 800 4 5 99 14 - * * i 'Fig. 14 schematically shows a portion of the overhead equipment, which includes a leveling noise canceling screen when it is not white, Fig. 15 schematically shows a portion of the overhead equipment containing an impulse-forming screen, Fig. 16 schematically shows certain operations performed by the impulse-forming screen, Fig. 17 schematically a portion of the overhead equipment, which includes a sharpening screen used to transform a double wavelet into an associated pair of sharp contractions, Figs. 18A-18F show six possible choices for a contraction overrun for a pair of contractions, as produced by means of the device of Fig. 17, Fig. 19 schematically shows a portion of the overhead equipment, which includes an astringent screen used to transform a single valve wave into an associated single contraction, Figs. 20A-20F six showing possible choices for a single-contraction contracting run, as produced by the apparatus of FIG. 19, FIGS. 21A-21C schematically show certain operations associated with an astringent screen for different time delays, FIG. 21A corresponds to a desired contraction at time index 0, FIG. 21B corresponds to a desired contraction at the time index 1 and FIG. 21C with a desired contraction at the time index 2, FIG. 22 schematically shows an apparatus for determining the operating parameter P of an astringent screen, FIG. 23 is a graph showing the manner in which the operation of the sieve P with contraction overrun can change for a sieve with a fixed duration, Fig. 24 is a graph showing how the operating parameter P of an astringent sieve can change by the sieve length (or memory duration) for a fixed contraction - 800 4 5 99 15 t * * ί trailing, Fig. 25 contains graphs showing how the operating parameter P of an astringent sieve can change with daffer length and the sieve follow-up time, Fig. 26A schematically shows a known pulse time coding system, Fig. 26B schematically illustrates the present pulse time coding system, the magnitude of the parameter being transferred being represented by the time lag between o peen-10 following a few short pulses with an essentially constant duration,

Fig. 26C further schematically the system according to Fig. 26B

Fig. 26D schematically shows the pulse time coding system of the type shown in Figs. 26B and 26C using "three-group" pulses, Fig. 27 schematically shows a block diagram of a code translator which can be used in order to enable a system to receive signals which are in the "three group" pulse time code-20, FIG. 28A schematically shows a block diagram of the circuit of the selector of FIG. 27, FIG. 28B, 28C 28D and 28e are graphs to help explain and understand the operation of the circuit 25 of Fig. 28A, Fig. 29 schematically shows a block diagram of the "downhole" circuit for generating the "three-group" shown in Fig. 26D. pulses, and Fig. 30 schematically shows a diagram of the circuit principles with which the present pulse time code can be established.

Fig. 3 shows a conventional system layout scheme in which the present principles have been implemented. Reference numeral 20 denotes a conventional petroleum well derrick with a turntable 21, a take-up rod 22, a hose 23 and standpipe 24, 800 4 5 99 16

-> L

* a drill bit 25 and heavy rod 26. A flush pump or punch 27 and soil hopper 28 are conventionally connected and provide drilling fluid under pressure to the standpipe. The high pressure mud is pumped down the drill string through the drill pipe 25 and the usual heavy rods 26 and then through the special distance measuring tool 50 and to the drill bit 31. The drill bit 31 is provided with the usual drill jets, shown schematically by 33. The diameters of the weight rods 26 and of the distance measuring tool 50 are shown in large and out of proportion to those of the drill pipe 25 to show the mechanisms more clearly. The drilling mud circulates down through the drill string, as shown by the arrows, and then up through the annulus between the drill pipe and the well bore wall. Upon reaching the surface, the mud (through pipes not shown) is drained back into the soil bin, where rock debris and other well debris can settle and is further filtered before the mud is taken up and recirculated by the mud pump.

The special tool 50 for distance measurement is arranged between the chisel 33 and the heavy bar 26. This particular distance measurement transmission assembly 50 includes a housing 250, which includes a valve assembly or simply a valve 40, further an electronic treatment assembly 96 and sensing members 101. The valve 40 is designed to temporarily divert a portion of the flush from the interior of the heavy rod in the annulus 60. Usually (when valve 40 is closed) all drilling mud must be driven through jets 33 so that there is significant mud pressure (on the order of 13.8 to 20.7 MPa). at the standpipe 24. When the valve 40 is opened by the instruction of a sensing member 101 and the electronic treatment assembly 96, a portion of the mud is diverted, the total flow resistance is temporarily decreased, and a pressure change can be observed at the standpipe 24 The electronic treatment assembly 96 generates an encoded series of electrical pulses, which series represents the parameter gt, which is measured by a selected 800 4 5 99 I 1 * '<17 detector 101, producing the associated opening and closing of the valve 40 with consequent associated pressure pulses at the standpipe 24.

Reference numeral 51 designates a pressure transducer 5 which generates an electrical voltage representing the pressure changes in the standpipe 24. The signal representing these pressure changes is processed by the electronic assembly 53, which generates signals which can be recorded on the recording device 54 or any other display device. The graph of the recorder 54 is controlled by well known means (not shown) by a control signal representing the depth of the bit.

Fig. 4A shows certain details of the particular distance measurement transmitter 50. Since FIG. 4A is schematic in nature, in a real tool, the housing 250 containing the valve 40, the electronic handling assembly 96, and the sensing members 101 is divided into two sections. 250a and 250 b. The top portion 250a (above the broken line 249) contains the valve assembly 40 and associated mechanisms, and, as described below, has a significantly larger diameter than the portion 250b. The lower portion 250b (below the broken line 249) contains the electronic treatment assembly 96, the sensing members 101 and associated mechanisms, and, as explained below, has a considerably smaller diameter than the upper portion 250a. As shown in Fig. 4a, the drilling fluid circulates along the special tool 250a, 250b downward (as shown by arrows 65) through the bit nozzle 33 and then back (as shown by arrows 66) to the surface in the ring space 60 and to the bottom tray 28 by pipe means (not shown). The valve assembly 40 includes a valve stem 68 and a valve seat 69. The valve stem and seat are configured so that the cross-sectional area of the seal A is slightly larger than the cross-sectional area B of the equalizing piston 70. Thus, when the pressure in the chamber 77 is larger than that in the chamber 78, the valve stem 68 is pressed downward, and the valve 40 tends to close more securely because an increased differential pressure becomes 800 4 5 99 18

X I

X τ exercised.

The fluid (flush) pressure in the chamber 77 is at all times substantially equal to the fluid (flush) pressure in the heavy rod, designated 26 in FIG. 23 and 50 in FIG. 4A, due to the orifice 77a in the wall of the assembly 250. A fluid filter 77b is disposed in the passage 77a to prevent the entry into the chamber 77 of solid particles and debris. When the valve 40 is closed, the fluid (flush) pressure in the chamber 78 is equal to the fluid (flush) pressure in the annulus 60. When the valve 40 is open 10 and the pumps are running, a flush flow occurs from the chamber 77 to the chamber 78 and through the opening 81 to the annulus 60 with associated pressure drops.

A double acting electromagnetic solenoid 79 is provided for opening and closing the valve 40 in response 15 to an electrical current supplied by electrical wire leads 90.

It is assumed that Pcn indicates the flushing pressure in the

oU

ring space 60, P _ the pressure in the chamber 77 and P the pressure in the chamber / / 7 o 78. When the valve 40 is then closed: P 0 = P. When the pumps 27 are running and the valve 40 is "closed" or substantially closed and the valve stem 68 is pressed toward the valve seat 69. When valve 40 is in the "open" position (ie, moved upward in the drawing), the result is a flow of mud from chamber 77 to annulus 60, due to the flow resistance of the orifice C (Fig. 4B), the relationship consists of P>> P ^ pm pm kamers chambers 83 and 84 are filled with 7/6060 an oil of very low viscosity (preferably a viscosity -2 of 5 x 10 m / s or less) and interconnected by a passage 86. A freely movable piston 82 makes the pressure Pgg in the oil-filled chamber 83 equal to P at all times. At all times

/O

so is P__ = PQ, = P. Therefore, when the valve 40 is "open", since P ^ g = Pg ^ and ρηη'7 pg ^ /, the valve 40 is pushed to the "open" position by a force F = (area B) (P - P_. ). The valve 40 can therefore be called 77 Ö4 bi-stable, that is, when the valve is "open" 35 it tends to remain "open" and that when the valve is 800 4 5 99 19 r r

1 I

"closed" it tends to remain "closed". Furthermore, when the valve is substantially open, it tends to move to the open position, and when it is substantially closed, to move to the closed position. Therefore, valve 40 can be "popped" from one state to another with relatively little energy. The valve action can be considered the mechanism equivalent to the electric bi-stable rocker switch well known in the electronics field.

Fig. 4B shows the valve 40 in the open position, the valve in FIG. 4A being closed.

Referring again to FIG. 4A, reference numeral 91 designates an electrical "pressure switch" that is electrically conductive when p7?> P ^ g (pump is running), and electrically non-conductive when P_ = P (pumps stopped, not running). A wire 7/92 92, which runs from the pressure switch 91 to a power source 93, can therefore switch the energy on and off. Also, by means of an electronic counter 94 and an electromagnetic program switch 95, one of the four sensing members 101 can be operatively connected to the electronic treatment assembly 96 by stopping and running the purge pumps 27 in sequence or by stopping and then running the pumps according to a predetermined code, which can be interpreted by the circuit in element 94.

Heretofore, the operation of the bi-stable valve 40 and the program switch 95 which establishes the selected electrical connection of the various sensing members 101 to the electronic treatment assembly 96 has been described.

For further details of the electronic treatment assembly 96, reference is made to Figure 5A, where like reference numerals designate like parts as in Figure 4A.

Various types of sensing devices that generate electrical signals representing a downhole parameter are well known. Examples include gamma ray sensing means, teraperature sensing means, pressure sensing means, gas content sensing means, magnetic compasses, strain gauge inclinometers, magnetic meters, giro compasses, and many others. For the example shown in Figure 5A, a gamma ray sensing means such as an ionization chamber or geiger counter or scintillation counter (with appropriate electronic circuitry) has been selected. All of these can be done by generating a direct current voltage proportional to the gamma ray flux intercepted by the sensing means.

Obviously, switching from one type of sensing means to another, as accomplished by the switching mechanism 95 of FIG. 4A, is within the reach of one skilled in the art (electronic switching rather than the mechanical circuit shown is to be most cases preferred). For the sake of clarity, therefore, only one single sensing member 101 is shown in FIG. 5A. The power source 93 and the purge pressure-operated switch 91 of FIG. 4A are also not shown in FIG. 5A.

In Fig. 5A, the sensing member 101 is connected in series with an A / D converter 101, a processor 103 and an energy controller 104. The energy controller 104 is connected to windings 105 and 106 of the double-acting solenoid 79. The operation is as follows. The sensing means 101 generates an electrical analog output signal, as represented by the curve 101a, shown in the graph directly above the sensing means rectangle 101. The curve shows the sensing means output as a function of the depth of the distance meter 50 iii of the borehole. The A / D converter converts the analog signal of 101 into digital form by sequentially measuring the magnitude of many ordinates of the curve 101a and translating each individual ordinate into a binary number, represented by a binary word . This treatment is well known in the art and requires no explanation. It is important to realize, however, that while graph 101a can represent the change in signal from the transmitter in hours, graph 102a represents a single ordinate (eg, A / B of curve 101by. The time scale of the X- axis of graph 102a is thus in seconds, the whole graph 102a representing a twelve bit binary word, and in fact the decimal number 2649. Thus, each 12 bit word on graph 102a represents a single ordinate, such as the ordinate AB on graph 101a The usual binary 8 0 0 4 5 99 t * * it 21 encloses time delays between each binary word.After the rest time, a trigger or leading pulse is transmitted to indicate the beginning of the time course, assigned for the binary word.

This leading pulse is not part of the binary word, but serves to indicate that a binary word is about to begin. The binary word is then transferred, which is an indication of the value of an ordinate on graph 101a, then a rest period, followed by the next binary word, representing the magnitude of the next ordinate, and so on, in a rapid sequence. Thus, the continuous curve of graph 101a is represented by a series of binary numbers or words, which numbers or words represent a single point or graph 101a. It is important to understand that there is always a rest between each binary word. This rest period (during which no signals are transmitted) is often several binary words long, the rest period being used for an important purpose, which is described below. In order to allow surface decoding, the clock No. 1 must remain strictly the same (and in synchronization with the associated clock 212 or 309, which is located on the surface), the clock being a series of mutually equal distances generates impulses in a manner well known in the electronics field.

The graph 103a represents a single bit of the binary word 102a, the X axis again being completely different from the previous graphs. The time on graph 103a is expressed in ms because the graph represents only a single bit.

Each single bit is translated into two electrical pulses, each with the duration of t ^ and separated by a time course t ^. The graph 104a is a copy of 103a, which is very strongly amplified by the energy controller 104. The electrical impulse 104b is applied to the solenoid winding 105 (which is the winding for the valve to be "open"), with the electrical impulse 104c is applied to the solenoid winding 106 (which is the winding for the valve to be "closed"). The valve 40 of Fig. 4A is thus opened by the pulse 104b and closed by the pulse 104c, so that the valve 40 remains in the "open" position for about 800 hours. The times are set to be correct for appropriate operation of the solenoid windings, the time t being measured for opening the valve 40 for the correct length of time. Both these times are determined and controlled by the clock 5 102.

When transferring information from sensing means to the ground surface, appropriate gaps are provided between transferring consecutive binary words. Due to these rest periods, it is possible to store the noise caused by drilling only (without the wavelet) in an appropriate electronic memory 10 with the surface equipment. The devices and operations required to accomplish this are described below.

As already noted, the valve 40 of FIG. 4A must be very fast acting, its rapid actuation requiring significant energy. As a result of proper testing, it has been found that such a valve requires about 0.37 to 0.56 kW to operate at the required speed.

Although this energy is very considerable, it is applied only for a very short time, and therefore requires only little energy per operation.

Actual operation during tests showed that 0.37 kW applied for about 40 ms provided the energy required to produce a satisfactory single valve actuation. This energy can be calculated at about 15 J.

A battery pack sufficiently small to be received in the housing 250b of Fig. 7A can provide about 4 MJ without the need for recharging or replacement. The system can therefore generate 130,000 full valve actuations (open plus close).

30 In reality, the energy consumption is less than 15 J per operation. The inductance, Q and motion impedance of the solenoid winding make the current build relatively slow and according to a curved rise, as shown in curve 272A of FIG.

5C, and 300, 301 of Figure 6E. Thus, the total energy per pulse is significantly less than 15J, and is measured at 9J, thus providing an 800 45 99 \ 1 23 capability of 216,000 full valve controls.

An even greater possibility is achieved by using the circuit described below in conjunction with Fig. 5C. From the foregoing, it is clear that providing the required "downhole" energy from batteries is quite possible for a practical distance measuring tool. However, providing the required very high energy (0.37 kW) presents serious difficulties.

Obviously, the solution to such a difficulty involves storing energy in a mechanism which can be forced to release it suddenly (in a short time) and thus provide the necessary short bursts of high energy. One such mechanism is "hammer impact", which has been used but has sometimes proved inadequate. Other mechanisms already considered are the use of compressed air, compression springs and others. Capacitor-15 energy storage systems require high capacitance values. The energy stored in a capacitor is variable as the first power of the capacitance and as the square of the stored voltage, since since solenoid drive windings with low inductance and fast operation are needed, the need for low voltage devices becomes apparent, and a first calculation has shown that excessively large capacitors would be needed.

After further investigation it has become apparent that an effective system could be possible. It has been determined by a mathematical analysis and by investigations and tests that a set of optimum 25 chain parameters must be as follows: 1. Inductance of the solenoid winding: 0.1 H in the actuated position, and 0.07 H in the non-actuated position ( i.e. a solenoid with a tapered anchor).

30 2. Resistance of the solenoid winding: 4.5 Ω.

3. Voltage under which energy is stored: 50 V.

4. Size of the storage capacitor: 10 F.

5. Power output of the energy controller: 10 Amp.

It has been determined that to have a fast solenoid operation, low inductance windings are desirable.

800 4 5 99 * i t * 24

It has also been determined that current powers of electronic control circuits can be increased far beyond 10 Amps. However, a low voltage requires excessively large capacitance values.

Recent improvements in so-called molten salt batts have produced energy sources with very good squat. The same recent technology has also developed capacitors with extraordinarily high values, 10 F in a space of no more than 15.6 cnf *. These are unacceptable due to the requirement to heat to a high temperature (500 ° C) which is considered impractical, the costs being far too high. As a result, further efforts were needed. After a thorough and lengthy investigation, it was finally found that a capacitor with a piece of tantalum, manufactured according to the latest developments, meets the requirements if the other parameters and factors, as outlined above, are brought to an optimum for adaptation to the properties of such capacitors.

From the foregoing, it is clear that at least 216,000 full valve operations can be realized from one battery charge. Assuming that the distance measuring system can provide sufficient continuous data by transmitting 5 pulses per minute, the system can operate continuously in a borehole for a period of 440 hours. It should be noted, however, that continuous operation is often not necessary. The tool can only be used intermittently when instructed by the circuit, controlled by the switch 91 and elements 94 and 95 of Fig. 4A.

Furthermore, when taking advantage of the improved circuitry of Fig. 5C as explained below, an even greater number of valve actuations can be achieved. An operation with a speed of one pulse per second is considered practical.

30 There is another parameter to be determined: the correct charging of the capacitor after discharge. The capacitor can be charged by a resistor connected to the battery (or other energy source), but this sometimes proves too slow because when the capacitor becomes partially charged, the current through the resistor 35 decreases, with the charging current at the end of the loading cycle, 80 0 4 5 99

Jt * * i 25 zero approaches. If the resistive ohmic valve is made small, the batteries must carry an excessive instantaneous current, because the first current surge during the charging cycle exceeds the value for maximum battery life. The best method 5 consists of charging the capacitor through an organ with a constant current. The capacitor is then charged at an optimum charging current, corresponding to the optimum discharge current for the particular type of battery for maximum energy storage.

By correctly determining the charging current, a significant increase (sometimes a factor of 2 or 3) in the amount of energy available from a particular battery type can be achieved. Steady current organs are well known and readily available electronic integrated circuits, and are available for a wide range of current values.

15 Fog. 5 schematically shows an energy source, which may be included in the energy controller 104 of FIG. 4A, which includes a capacitor charging and discharging device for providing the required energy for the windings of the solenoids 79. In FIG. 5B 450 designates a battery or turbo generator 20 or other source with a DC electric potential, 451 the constant current means and 452 the capacitor.

The capacitor is charged by constant current member 451 and discharged through line 453. Line 454 provides the regular, constant energy required for the rest of the electronic downhole equipment.

Also provided is a device operative in the event of a malfunction which can occur when the valve is "stuck" in an open position for a long period of time. A device for automatically closing the valve in the event of such an erroneous operation (indicated by reference numeral 269 in Fig. 4A) is shown schematically in conjunction with Figs. 6A, 6B and 6C.

As noted earlier in the description, the valve is designed to have a hydraulic detent or bi-stable action 35, that is, after opening it by an impulse from 800 45 99 I 1 t * 26 the solenoid winding 105 , the valve tends to remain open, and later when closed by an impulse from the solenoid winding 106, the valve tends to remain closed. It is possible that, due to an electrical or mechanical malfunction, the valve will "jam" in the open position. It is to be noted that if such an incorrect operation takes place, drilling can continue. Some wear will occur at the opening 81 of Fig. 4A. However, disturbing the hydraulics of the spool system by having the valve open for long periods of time is not desirable, although although drilling can continue, it is very advantageous to Have the valve closed for most of the time and have it open only to produce the short pulses needed to generate the hydraulic shock wave.

In the schematic Figs. 6A, 6B and 6C, the rod 100 is used to press the valve closed by applying a force downward on the rod 80 of Fig. 4B (the axis of the solenoid armature).

Referring now to Figures 6A, 6B, 6C, and 6D, the upper end of the mechanism is exposed to "drill pipe mud", that is, spooling under the hydrostatic pressure plus the differential pressure across the bit, i.e. the pressure difference between the interior of the tool 50 and the annulus 60. When the punches are not operating, the pressure at the region 111 is hydrostatic only, where when the punches are operating, the pressure is hydrostatic plus differential pressure. Since the pressure differential is on the order of 6.9 to 13.8 MPa, a large pressure change occurs at the region 111 when the punches are turned on (i.e., an increase from 6.9 to 13.8 MPa). In Fig. 6A, when the pumps are not operating, the regions 112, 113 are on ring space pressure because the tube 114 is connected to the chamber 84, which contains oil under ring space pressure (see Fig. 4A) and because the opening 115 is areas 112 and 113.

It is now believed that the pumps are turned on. The pressure in the region 111 then increases significantly (ie, from 6.9 to 13.8 MPa), the piston 116 is pushed down, compressing the spring 107 (not shown in Fig. 6B), and the 800 High pressure oil in region 112 presses piston 108 down and compresses spring 110 (not shown). Thus, when the pumps are turned on, the components of FIG. 6A change to the arrangement of FIG. 6B, with both pistons 116 and 108 being in the down position, and the rod 100 being depressed as shown.

Due to the opening 115 and the action of the spring 110, the piston 68 is then pushed upward at a speed determined by the size of the opening 115, the spring constant of the spring 110, and the viscosity of the oil in the areas 112,113. This speed can be easily controlled and made equal to any desired value, such as, for example, such a speed that the piston 108 returns to its original up position in about 1 minute. Therefore, after one minute, the device assumes the arrangement of Figure 6C. When the pump is stopped, for the same reasons, the operation of the spring 107 and the opening 115 causes the piston 116 to return to the original state of Fig. 6A.

It is therefore understood that each time the rinse pump is turned on, the rod 100 moves down the distance 20d, as shown in Fig. 6B, and then returns to the usual retracted position. Since in conventional drilling the pump is stopped every time a drill pipe (usually 9 meters long) is added, the rod 100 makes a single downward stroke and then returns to the original upward position.

As already noted, the rod 100 is mounted so that when it is downwardly depressed it depresses the solenoid armature shaft 80 of FIG. 4A and closes the valve. Thus, the member of FIGS. 6A, 6B, 6C, and 6D is a "safety" member, that is, if the valve gets stuck in the open position due to an electrical or mechanical malfunction, the valve is forced to close after drill a maximum of 9 meters.

Pig. 6D shows the construction of the member schematically shown in FIGS. 6A, 6B and 6C. In the actual tool, the member shown in Fig. 6D is placed in position 269 of Fig. 4A. Similar reference numerals in Fig. 6D

800 4 5 99 28 t t 1 1 represent similar elements in Figs. 6A, 6B, 6C and 4A.

The hydraulic "auto-closing" system described in conjunction with FIGS. 6A, 6B, 6C, and 6D automatically closes the valve every time the purge pumps are stopped and turned on again, so that a mechanical jamming of the valve can thus be eliminated. However, there is a case that needs further attention. If the electrical "close" circuit 103, 109 of FIG. 5A failed for some reason (eg, a burned out solenoid winding), the valve would reopen electrically shortly after the hydraulic "auto-close" member closed the valve .

Fig. 6E shows an electrical system that prevents valve operation in the event of an electrical failure in the downhole device. indicates the winding of the solenoid "closing" the valve, and the winding of the solenoid "opening" the valve. The resistor Rc is connected in series with the portion of the solenoid controller 104, which portion operates the "open" solenoid winding S2. These resistors have a very low ohmic value (about 0.05 to 0.2 Ω). It is clear that the operation of the system 20 described in detail with respect to Fig. 5A is as follows. The electrical "open" current pulse is generated first and is schematically shown in FIG. 6E as the pulse 300, the electrical "closed" current pulse being generated later (after a time t) and schematically shown as 301 in FIG. 6E. It should be noted that these electrical pulses 300 and 301 represent the current drawn by the solenoid windings and not the applied voltage (the resistors Rj and Ej generate voltage drops Rl and where the currents indicate due to the solenoid windings involved), so that if one of the winding lines S and S is burned out or opened, no current 1 2 30 is running and no associated pulse is produced (similarly, any other electrical error makes no current through one or both resistors R1, R2 goes).

The magnitude of the time t ^ of Fig. 6E and the length of the time t has already been explained and determined in connection with Fig. 5A.

The delay of the delay element 302 is equal to 800 4 5 99 4 'Ί 29 to t ^. In other words, the block 302 produces an impulse at its output, equal to the input impulse but delayed with time t. Such delay systems are well known and need no description at present.

Since the delay of the element 302 is equal to ty, the pulse, as represented by 303, is time coincident with the pulse 301.

304 is a coincident circuit (also known as an OP gate) and produces an electrical signal at its output 305 only when one of pulses 301, 303 is pressed thereon, but produces no output when both pulses 301 and 303 present. 306 is a relay operated by the signal on line 305 and configured to disconnect the energy from the downhole tool. So if only a "close" impulse is present (without the "open" impulse) or if only an "open" impulse is present (without the "close" impulse), the energy is switched off to the "downhole" control and the valve is closed mechanically by the "automatically closing" hydraulic systems described in conjunction with FIG. 6D.

As another embodiment in Fig. 6E, relay 306 (which may, of course, be an electronic switch comprising transistors), may be configured to turn off the power to only the "opening" solenoid circuit. This has certain advantages because the "closing" circuit continues to operate, and one of the purposes is to ensure the "closing" of the valve. Furthermore, an electronic counter 314 may be provided between the OR circuit and the relay circuit 306, so that a single electrical fault operation does not turn off the energy, the enargy is then only turned off after, for example, 2.4 or 8 consecutive false operations.

As already noted, very fast operation of the valve 40 of Figure 4A is important. The required shock wave is not produced if the valve action is slow. Since the valve and its actuating mechanism contain a substantial mass, a considerable amount of energy is required to open and close the valve 800 45 99 30 1 1 X * in time which is considered desirable. This energy is on the order of 0.37 to 0.56 kW and can be provided by an energy source described above. As with all designs of this nature, an energy margin is required to ensure that the valve always opens and closes on instruction. The various electronic "logic circuits" and "power control circuits" shown in FIG. 5A are designed to provide rectangular voltage pulses 104b and 104c, which have a duration of about 40 to 50 ms to ensure that the solenoid windings 105 and 106 are energized for a sufficiently long time to ensure operation of the valve. Fig. 5E shows the voltage pulse 104b of FIG. 5A in more detail. At the instant 0, the voltage is applied suddenly by the power controller 104, which voltage rises almost instantaneously to the value, represented by the reference numeral 270, remains at this voltage value for 50ms, and then turns off and falls (again almost instantaneously) to the value zero. It is very informative to study the movement of the valve by taking measurements of the electrical current in the solenoid control winding and making a graph (see fig. 5D). From such a graph, the behavior of the valve can be studied quantitatively. Fig. 5D shows such a graph in the form of an oscillogram of the current versus time. This current is measured, for example, by the voltage across the resistor or R2 of Figure 6Ξ.

It is important to understand that it is the current through the solenoid winding that determines the force on the valve stem 68 of FIG. 4A because ampere windings determine the electromagnetic draft. Since the windings have the solenoid inductance, the current is not built up instantaneously when a sudden voltage is applied, as in Fig. 5E. If the solenoid were a simple choke, the current would be built up according to the simple exponential curve 271 of FIG. 5D, as shown by the broken curve. In reality, something completely different takes place. When the valve is actuated, 35 (open or closed), a sudden movement of 80 0 4 5 99 1 ► * "l 31 the armature of the solenoid 79 of FIG. 4B takes place, turning a counter-electro-motor force This counter-electromotive force is caused by the speed of the armature, which rapidly changes (increases) the inductance of the involved winding of the solenoid 79. In Fig. 5D, 271 shows the approximate current against time curve. the solenoid winding when the armature of the solenoid 79 and valve stem 68 are "blocked" in the "open" or "closed" state.

The drawn curve 272 in Fig. 5D shows the actual build-up of current when the valve is not blocked, that is, in the actual operating state (opening or closing). The opening and closing curves 272 are very similar. It can be seen that the curves 272 gradually rise after application of the voltage (because the solenoid winding 105, 106 has inductance) until it reaches the value of 4 Amp at the instant T in the example shown, which is 20 ms. . Then there is a sudden drop in the current, reaching the lower value of 2.2 Amp at the time, which is 25 ms. After the T ^ = 25 ms, the current increases again according to the usual "exponential" until the current 20 asymphototically reaches the value of about 10 Amp at the time of about 60 ms (this value is determined by the resistance of the solenoid winding , which in the example given is about 4.7 Ω).

An examination of the curve 272 in Figure 5D shows that the valve 40 begins to open or close at the time Tq = 20 ms and the movement completed at the time = 25 ms.

As already noted, a substantially similar condition occurs during the "opening" or "closing" of the valve, the curve 272 indicating that at the instant T ^ = 20 ms, the valve starts its movement, and at the moment = 25 ms, the movement is completed.

It is important to note that the moment = 25 ms in Figure 5D is given as a useful example, which depends on a number of factors. Therefore, at large pressure differences, Tj is greater than 25 ms, and can be as high as 30, 35 or 40 ms. Suffice it to say that the moment in Fig. 5D indicates the moment at which 800 4 5 99 32

4 X

τ. 1 operation of the valve is completed, with the current between the moments and 50 ms actually being "lost" because the operation of the valve has already been completed. This extra time is a "safety factor" to ensure that even under the harshest conditions, the valve is always operated when the voltage pulse is applied.

In accordance with the invention, use is made of the signal at the time to turn off further power to the solenoid 79. As a result, all power is saved between the 10 moment and 50 ms (thus the total amount of energy required to operate the valve 40 is greatly reduced). It should be noted that the full "safety factor" indicated above is maintained, with the current applied until the valve has completed its operation (opening or closing). The electronic circuitry used to accomplish the foregoing purpose is shown in Fig. 5C, where 104 indicates the power control of Fig. 4A. A resistor (R ^ or R ^) with a low value (compared to the resistance of the 20 solenoid), for example 0.2 Ω, is provided between the energy controller 104 and ground. The voltage across this resistor is therefore proportional to the current supplied to the determined solenoid winding 104.106. Two circuits, as shown in Fig. 5C, are needed, namely one for opening the solenoid power controller and a second for closing the solenoid power controller, however only one circuit is shown for simplification. 5C. 273 is a conventional amplifier, at its output the voltage curve 272a of FIG. 5C is a copy of the curve 272 of FIG. 5D. 274 is a diverter (well known in the electronics field) that generates an output voltage proportional to the first time derivative of its input voltage.

Curve 275 shows this derivative voltage. By considering the curve 272 or 272a, it can be seen that the derivative (slope) of the curve is always positive, except during the times between T ^ and T ^, during which time the slope (derivative) is negative.

On the curve 275, only the pulse 276 is negative. 277 is a 800 4 5 99 33 * conventional rectifier configured to pass pulse 276 only, as shown in graph 278. 279 is an electronic delay circuit (also well known in the art), which has an output pulse 276b which is a copy of the 5 input pulse but slows down with time - T ^. Thus, the pulse 276b, as shown in graph 280, occurs a little later than the instant T ^. This impulse 276b is applied to an electronic switch 281 configured to turn off the power to the power controller 104, causing the electric current 10 to be stopped almost immediately after the valve 40 has completed (opened or closed) its operation. The electronic switch 281 is configured to restore the operation of the power controller 104 after an appropriate period of time. The operation is repeated when the next pulse 104a (or 104b) occurs.

It is important to note that the energy savings that can be achieved by applying this aspect of the invention can be very substantial. Since very large amounts of energy are required to operate the valve ni40 at the required high speed, this saving is very significant, and in the example shown it can extend the battery life by up to 5 times.

An important feature of the present apparatus for measuring during drilling is its practicality, ie the advantage and ease of adaptability to existing petroleum well drills and tools, and drill columns. In known attempts, large, special steel houses with a length of 9 meters or more and a diameter of 20 cm are required to accommodate the complicated instrumentation, the transport of which from place to place requires specially constructed vehicles. Since there is no valve mechanism in the main rinse flow in the present apparatus, it is possible to eliminate the heavy, very long, expensive, special housing (about 9 meters long), requiring only a short piece of heavy rod (called "transition piece") In the practical embodiment of the invention, this transition piece is only 90 centimeters long and 800 4 5 99 34

A T

* p 16.9 centimeters in diameter (instead of the 9 meters previously required).

Therefore, one of the main features of the invention is that no heavy, tall, special houses are required. This is advantageous, especially when magnetic "downhole" measurements are to be performed, such as congestion indicia (for example, directing a different hole drilling), which measurements require the use of non-magnetic rods. Non-magnetic heavy bars are not only heavy (2-3 tons) but also very expensive, because they must be made of genuine non-magnetic material, such as a metal alloy, which mainly contains nickel and copper. Standardized API heavy bars with external diameters from 15 centimeters to 22.5 centimeters (which are the most common dimensions) are used in the construction of the present device. All normalized API heavy bars have an inner diameter of 7.14 centimeters + 1.6 mm - Omm. The simplicity, the small size and the coaxial construction of the present valve system with the associated components make it possible to provide a special feature. The entire energy controller 20 and associated equipment of interest may be contained in a pressure-resistant tube sufficiently small in diameter to insert it into the inner bore (7.14 centimeters) of a normalized API-weight rod without unduly obstructing the purge flow. Certain detectors should be placed as close to the drill bit as possible.

In particular, a "downhole" gamma ray detector must be able to detect penetration of the bit into a particular lithological formation as soon as it occurs. Furthermore, certain sensing means, such as a "downhole" compass inclinometer, require accurate positioning with respect to the "tool end face" used in directional drilling. In addition, a compass inclinometer must be placed at a considerable distance from magnetic or paramagnetic material. Further, when using a compass tilt gauge, the housings 250a and 250b in Fig. 7A must be precisely angled with respect to the transition piece 253, which in turn is positioned with respect to the "bent transition piece", 800 4 5 99 1 * *> 35 used for directional drilling.

The "bent transition piece" is equipped with a placement mark 253a, the angle of this placement mark must have a constant and measured angular relationship with the placement mark 254a, which is applied to the transition piece 254. This known angle (representing the angle between the placement marks 253a and 254a) is then calculated to determine the direction and angle with respect to a vertical plane of the "bent transition piece".

FIG. 7A schematically shows the special spacing measuring tool 50, showing the embodiment with the "particularly long tool" eliminated, and only a short length of heavy bar transition piece required as previously stated. In Fig. 7A, a housing 250 consists of an upper portion 250a and a lower portion 250b, as described above with reference to Fig. 4A. The top portion 250a is contained in a short transition piece 254 (which is only about 90 centimeters long). This short transition is particularly designed to provide an inner diameter (eg 11.4 cm) sufficient to accommodate the valve assembly 40 and also to allow unobstructed flow of drilling fluid along the top portion 250a through the passages 61, which are also indicated by reference numeral 61 in Fig. 4A. The housing 250a has a small diameter, preferably an outside diameter of 6.83 cm or less. A heavy-duty 255, provided by the user (the petroleum company or the borehole contractor) is usually 9 m long with a high weight and cost. The inner diameter of a normalized API heavy position, as already noted, is 7.14 cm - 0 cm + 1.6 mm. Centering members 256 are provided for the lower housing 250b. These 30 are slightly smaller in diameter than the inner diameter of the normalized API heavy bar, for example with an outer diameter of 6.99 cm. A small play is very important to prevent "vibration" when the tool is vibrated during drilling.

A drain passage 85 is the same as shown in Fig. 4A. The housing 250b is suspended in the transition piece 254 by securing means (not shown). The cross-sectional shape of the center members 256, 800 4 5 99 36 1 shown in Fig. 7B is such that they provide slots or passages 258 to allow free flow of the drilling fluid.

The lower housing part 250b actually consists of a number of intermediate parts, which are connected to each other by special connecting means, shown in Fig. 7C. As shown in Fig. 7C, each intermediate portion is provided at its upper end with a slot 260, and at its lower end with a projection or tooth 261. A projection 261 of one intermediate portion co-operates in a slot 260 of the adjacent intermediate section. The adjacent intermediate portions are held by a connecting sleeve 262, which is received together by the end portions of the intermediate portions. Circular openings 263 in the intermediate portions are aligned with associated screw openings 264 in the connecting sleeve 262, the parts being secured by screws 265.

The particular connecting means of Fig. 7C provide precise angular positioning when the transition piece 253 is a "curved transition piece".

As already noted, the angle between the placement marks 253a and 254a must be known to calculate the angle with respect to the vertical of the "bent transition piece". It is also necessary that the angular displacement between the axes of a magnetometer inclinometer and the mark 254a be known and unchangeable during drilling (it is preferred, although not necessarily, that the angle between one of the horizontal axes of the magnetometer inclinometer and the placement mark 254a equals zero). For this purpose, the portion 250b is equipped with a corner placement position 261, as shown in Figs. 7C and 7A.

30 In order to design an effective distance measuring system, two conditions have to be considered. One of these relates to optimal conditions for obtaining the hydraulic shock wave regime. The other condition relates to obtaining shock waves of sufficient strength to dominate foreign noise effects.

800 45 99 37 i * * i

A series of investigations has been conducted to determine the optimal conditions for the high-shock wave regime.

The occurrence of a hydraulic shock wave is analogous to that of the water hammer action. Suddenly stopping the flow in a local area in the flow line suddenly increases the pressure in that area. This initially local pressure increase propagates along the flow line as a "water hammer". It is well known that a sudden and local change (decrease or increase) in speed produces an associated local change (increase or decrease) in pressure, and conversely, a sudden and local change in pressure produces a sudden and local change in speed produces. Due to the resilience and inertia of the fluid, the change is further transferred from the volume element where it originated to neighboring volume elements at a velocity which is the propagation velocity of pressure waves.

The problem of propagating shock waves is extremely complex. In order to meet practical requirements, a parameter 20 must be established, which is most clearly representative from the viewpoint of obtaining a clearly defined shock wave. Two parameters are considered, which are referred to as parameter and parameter l ^. When one of these parameters exceeds an appropriate value, a clearly defined shock wave 25 is produced.

The parameter is the average rate of change of the velocity of the purge flow through the bypass valve over the time of valve opening (or closing).

It is assumed that V (t) is the velocity of the purge flow through the bypass valve as it changes over time (in cm / s). At the time t = 0, when the valve starts to open, the speed is 0, i.e. V (0) = 0. At the time t = T ^, 9.

when the valve is fully open, the speed of the valve reaches a certain value Vf, which is the circulation speed during the period of full flow.

800 45 99 (v) 4 l 38

So: v or ') = v (ίο)

cl X

Accordingly, the parameter K, which is the mean change

* / V

5 speed is of the speed during the period Τ ': 3.

κ = vf (ID

τ (ν) a, 2 10 is measured in cm / s.

It is believed that when an appropriate threshold value exceeds, that is, when Κχ M1 (12) 15 a clearly defined shock wave is obtained. The investigations carried out established that: M = 2 x 105 cm / s2 (13)

The parameter represents the average scraping speed of the area of the valve opening over the time 20 T (V).

a S (t) has already been determined (see equation (1)) as the area of the valve, which area is open at time t. So at t = 0, S (0) = 0 and at t = (v) ^ s (rVJ) = s0 (14) is 25 where the total opening of the valve is. The parameter K2 is: S0 2 K2 = --- cm / s (15)

T

a

It is believed that when an appropriate threshold value exceeds, i.e. when K2 M2 (16) a clearly defined shock wave is obtained. In the 2 investigations carried out it was established that M - 100 cm / s.

Generally speaking, it is proportional to K2> The parameter K2 may be more useful, because it directly indicates the method of valve design and operation.

800 4 5 99 * <39

There is also a parameter (see B, C., Fig. 2A), that D11 is to be considered when discussing Figs. 8A to 8E. Each of these figures corresponds to a set of numerical values of and T <v) or K and T <v). b 2 b 5 Figs. 8A to 8E show the consequence of changing K. and or K. and T, in the transition of the regime from a slow pressure change to the regime of hydraulic shock waves. More specifically, each of these figures shows the manner in which the perceived pressure and the ground surface (ordinate) are variable with time t (X axis). The size of the opening in these studies was 0.5 cm. Experimental data was obtained from a number of wells. In addition, some of the experiments were performed on an "experimental well", which was drilled exclusively to perform distance measurement studies.

In the conduct of the previous investigations, the wide variety of existing flushing pump installations and various disturbing consequences were taken into account. There are many types of flushing pumps: single two-piece, double two-piece, 20 single three-piece, double three-piece, where the pump pressure changes for a given average flushing pressure are highly variable from installation to installation. Eliminating the strong interfering rinse pressure signals is complicated. The pump pressure signals of a single two-member system can be ten or even twenty times greater than that of a precisely adjusted double three-part. To determine the optimal values of K ((or f \ **) and of ', drilling was stopped and a very good (uniform) three-part pump was used. Thus, the graphs in Figs. 8A to 8E are not representative of a typical state, but represent a state where the various types of tuis (from the ponps and other sources) were minimized and then averaged by calculation and design to obtain optimal values for the parameters (or K ^) and.

The corresponding values of (or K ^) and for each of Fig. 8A

35 to 8E are given in the following table.

800 4 5 99 r * 40

TABLE

K „(in cm2 / s) (in s.)

2 D

FIG. 8A 0.5 2

Fig. 8B 2.5 1

Fig. 8C 8.5 0.5

Fig. 8D 2.5 0.25

Fig. 8E 100 0.1 10

The graphs of Figures 8A to 8E represent average numbers obtained in a large number of experiments. In these tests, the usual standpipe pressure was equal to 20.7 MPa, with pressure changes in the range of 0.7 MPa. The preliminary tests were performed using different types of valves: motor driven, rotary, stem valves, etc.

Fig. 8F is an accurate copy of the standpipe pressure recorder graph obtained from tests, performed at 2940 meters with a standpipe pressure of 19.3 MPa, and performed in practice drilling a petroleum well.

The graph in Figure 8A was obtained using a slow acting valve. The number values of the important parameters in Fig. 8A are = 0.5 cm / s and = 2 s, that is, they were similar to those proposed in the prior art, as in Fig. 1A and 1B. As a result, both Fig. 8A and Fig. 1B represent the regime of slow pressure pulses. In contrast, Figure 8E was obtained using a fast acting valve, for which K 1 = 100 cm / s and = 10 * s. As a result, Figure 8E represents the regime of hydraulic shock waves, the valve wave in Figure 8Ξ being very similar to the valve wave in Figure 2B.

Figures 8B, 8C and 8D, as determined in the previous table, show the transition from the slow pressure change regime to the hydraulic shock wave regime.

In the tests shown in Figures 8B, 8C and 8D, the conditions were kept the same as much as possible. The tool was located near the bottom of boreholes with a depth of about 2400 meters, with the mud viscosity about 40 funnel and weight 1.4 kg per liter. In the "open" position, the valve had a working open area of 0.7 cm. The usual standpipe pressure was 20.7 MPa, with the valve used in these tests being similar to valve 40, although modified to allow slower operation (without bi-stable operation), i.e. the valve has a simple pressure relief valve, the flow rate being controlled by a throttle at the inlet passage. It should be noted that the valve action responsible for Fig. 8B was relatively fast, but did not produce the desired hydraulic shock wave regime. However, the sharp onsets indicated that faster action is desired. The discharge rate 2 was on the order of 19 l / s.

By adjusting the inlet throttle and exhaust nut, and the electrical energy supplied to the steering solenoids, different valve operating speeds were achieved.

From the foregoing, it is clear that no shock waves 2 are produced when K 2 = 0.5 cm / s, and a near-ideal Δ 2 shock wave is produced when = 100 cm / s.

Another parameter is now introduced, which expresses a condition regarding the strength of the shock wave.

Two different approaches are considered. One of these is based on a parameter KL, which represents the amount of rinse

3 J

(measured in cm or in 1) passing through the valve during the time period T ^. (This amount is known as "flow"), English fluence.

cl

The other approach is based on a parameter K ^, which represents the average flow of the purge current over time (v) 30 · DuS '(v) K = k ° variable purge during T ^ 4- a

The duration of the opening of the valve, i.e. the duration T ^ is considered. To simplify the question, it is assumed that the rate of increase of the velocity (v) of the flow during the time T is constant and d 800 45 99 42 X is equal to K ^. So, V (t) = t in cm / s. (18)

It is also assumed that the rate of increase of the valve opening is constant and equal to K 1. So, 2 1 5 S (t) = in cm / s. (19)

Consequently, the volume that passes through the valve during the (v) time T is equal to: a T (v) / a, (KKT (v) 3 3 K = / KK t2dt = ......... ..2 a} - Cm (20) J 0 W 3 10 3

Thus, the parameter K, is the amount in cm of the fluid that 6 (v) passes through the valve during the time T. This is the amount of flow for the duration of one single opening and closing of the valve. Another possibility is to take a parameter K instead of the parameter 15 K, which represents the flow during 4 (v) during the time T, i.e. 3.

K4 * “JJTt) (21) a 2q Now the general procedure for decoding signals from the pressure transmitter 51 is considered. 9 shows the device construction, with FIGS. 10A to 10G showing certain waveforms and pulses related to the decoding of signals by the construction of FIG. 9.

The signal obtained from the pressure transducer 51 includes a useful information carrying signal along with interfering signals, which tend to blur or mask the useful signal.

The useful information carrying signal represents the coded message obtained by means of the valve 40 in response qp 2Q a sensing means. There are several disruptive signals. One of these, produced by the pump 27, contains a strong, constant component of the flushing pressure produced by the pump. This component is responsible for the circulation of the mud through the boox pipe and back through the annulus between the drill pipe and the borehole wall. It is superimposed on this

OD

800 4 5 99 43 t 1 '> component, produced by the periodic movement of the reciprocating pistons in the pump.

To improve reception, it is desirable to remove the constant component in the pressure generated by the pump 27 from the output of the transmitter 51. Accordingly, a frequency selective screen 140 is connected to the transmitter 51 to transmit frequencies in a range from 0.1 to 10 Hz, and attenuation of frequencies outside this range. The frequencies contained in the constant pressure component are below 0.1 Hz.

In the terminology used for the applicant, a distinction is made between the term "screen", as used for the frequency selective screen 150, and the term "digital screen", which is used hereinafter in the description. In a "sieve", such as the sieve 150, a conventional sieving is performed by means of 15 analog electronic circuits, the behavior of which is usually treated in the frequency range. The term "sieve" can be used to designate what is called a "wave sieve", a "Shea sieve" (see, for example, "Transmission Networks and Wave Filters", by T. Shea, D. VanNostrand Co ., New York, NY 1929) 20 and other seven, such as Tchebyshev and Butterworth seven. A digital sieve, on the other hand, such as an equalizing sieve, an impulse-forming sieve or an astringent sieve, can be treated more fruitfully in the time region. The output of a digital screen is obtained by processing the digital input track with the weighting coefficients of the screen. A digital sieve is a computer.

The signal produced at the output terminal 151 of the screen 150 is expressed by a function F (t) as follows: F (t) - B (t) + P (t) + U (t) (22) where B (t) is the useful information carrying signal is, P (t) is the disturbing signal caused by the intermittent pressure change of the pump (pore noise), and represents U (t) background noise. The background noise is produced by various effects, such as the action of teeth of a cutting bit (such as a serrated core bit) during drilling, by the gears in the mechanical drill string and by other organs, related 800 4 5 99 * X 1 '44 having on rotary drilling operations. In some cases, U (t) approaches white noise, although the deviation of U (t) from white noise may be significant in other cases.

The encoded message expressed by the information carrying signal B (t) is a series of binary words, each of which contains a sequence of bits. A single bit in a binary word is produced by a single "actuation" (ie by a single opening and closing) of the valve 40. Such a single actuation generates a hydraulic shock wave which extends at the surface of the ground as a single valve wave, such as the valve wave in Fig. 2B. Consequently, the message expressed by B (t) is in the form of an encoded sequence of valve waves, each of the valve waves being of the type shown in Fig. 2B. Figs. 10A to 10G show various steps to be accomplished to separate the information carrying signal B (t) from the interfering signals. To facilitate explanation, B (t) in Fig. 10A is expressed by a single valve wave rather than an encoded sequence of valve waves. Thus, the valve wave in Figure 10A is of the same type as a single valve wave in Figure 2B. However, there is a slight change in designation. In FIG. 10A, the top "s" omitted in FIG. 2B is omitted. Thus, in Figs. 10A to 10G, the different times are denoted as t ^, .......... t ^, t ^ g without "s" above. The various graphs in FIGS. 10A to 10G are appropriately labeled in these figures. For the sake of clarity and to facilitate explanation, the time scales corresponding to these graphs have been distorted.

To eliminate the disturbing noise signals (pump noise and background noise) and to produce a signal representing the encoded message, three consecutive treatment steps are provided, which can be identified as follows.

In step 1, a three component signal as shown in Fig. 10A is transformed into a two component signal as shown in Fig. 10C. The 800 4 5 99 45 s "* l goal of this step is to eliminate the pump noise P (t). As a result of this step, a "valve wave" of the type shown in FIG. 10A is transformed into a "double wave". Such a double wave is shown in Fig. IOC.

5 The purpose of step 2 is to cancel the rear ground noise signal.

In step 3, each double wave, as shown in Fig. 10D, is transformed into a single pulse, as shown in Fig. 10G. As a result, a coded sequence 10 of single pulses is obtained, which in digital format represents the parameter measured by the sensing means 101 at an appropriate depth in the borehole.

Fig. 10A is now considered. This figure shows the three components of the signal F (t), as expressed by the equation (22). These are: valve wave B (t), pump noise P (t) and background noise U (t). As already noted, the signal F (t) is obtained by the sieve 150. This sieve is connected to a delay element 152, which acts to delay the input signal F (t) by the amount of T, which is one period is

P

20 in the oscillation produced by the pump 27. The signal obtained at the output line 153 of the delay element 152 can thus be expressed as F (t) -T. The three components of the signal

P

F (t - T) are shown in Fig. 10B. These are: the delayed P

valve wave B (t - T), the delayed pump noise P (t - T) and the P P

25 delayed background noise U (t-T). The time course T is dependent on

P P

of the rotational speed of the pump, where because the rotational speed of the pump is not constant, the deceleration T has a variable

P

delay. Thus, appropriate control for the delay element 152 must be made in response to the rotational speed 30 of the pump 27. Accordingly, the delay element 52 is configured to receive control pulses from line 154 obtained from a pulse generator 155 which is driven mechanically by the pump to produce an appropriate number of pulses per revolution of the pump. A chain drive 156 is provided for this purpose.

800 45 99 46 * l t

The pump is believed to produce 27 strokes per second. So T = 1 / N ^. The pulse generator 155 produces control pulses at a relatively high speed N ^ which is a multiple of N ^. So = KN ^, where K is a constant, which is chosen 5 to 512. Thus, if the pump's strokes consist of one per second, this requires the signal generator to produce 512 pulses per second. It is understood that the rate of impact of the rinse pump 27 is variable with time, and is accordingly variable to ensure that the delay produced by the delay element 152 is always equal to one period of the rinse pressure oscillations produced by the flushing pump 27.

The signal F (t-T ^) obtained from the delay element 152 is applied to an input line 153 of the subtractor 160.

The subtractor 160 also receives on its input line 161 the signal F (t) obtained from the screen 150, and produces a signal difference on its output line 162 equal to: x (t) = F (t) - F (tT)

P

= B (t) -B (tT) + P (t) -P (t-'Tj + U (t) -U (tT) (23) pbp 20 Because P (t) is periodic and has a period of T , is: P (t) - P (t - T) = 0 (24)

P

Hence, due to the periodicity of pulses produced by the rinse pump 27, the noise from the pump is eliminated, the signal obtained at the output line 162 of the subtractor 160 now being able to be expressed: x (t) = b ( t) + u (t) (25) where: b (t) = B (t) - B (t - T) (26)

P

the information carrying signal is, and 30 u (t) = U (t) - U (t - T) (27)

P

is a background noise signal.

Both the information carrying signal b (t) and the noise signal u (t) are shown in Fig. 10C. It can now be seen that by performing step 1, as outlined above, the in formation bearing signal B (t), as shown in Fig. 10A and 800 4 5 99 r »47 in the form of a valve wave , is transformed into another information carrier signal bit), as shown in Fig. 10c. The signal b (t) is referred to as a "double wave" as opposed to the signal B (t), which represents a "valve wave." A double wave comprises two valve waves, such as valve waves A and B in fig. IOC. These valve waves are separated from each other by the time course T. The valve ball A is similar to that of Fig. 10A,

P

wherein valve wave B represents the inverted shape of valve wave A.

The signal x (t), equation (25) m is further applied to the input line 162 of an analog-to-digital (A / D) converter 163, which is controlled by a clock 178. To the output line 164 of the A / D converter, a signal is obtained, expressed as: x = b + u (28) ttt 15 in which according to the symbol gen used x ^ _, b ^ _ and u ^ are digital versions of the analog signals x (t), b respectively (t) and u (t). The signals xfc and u ^ are in the form of time series, such as: xt = (... X_2, x_1 xQ, x1?..., Xg,...) (29) 20 and u - (· · · u 2 / uj, u ^, / · · · r, ...) (30) where, the signal bt is a wave of finite length: bt = (V bl 'b2' '"V (31)

The mixing of a double wave bfc and the noise signal 25 µl is then applied to a digital sieve 170 with a length of (n + 1), provided with a memory operation: a. = (A_, a., A,... ., a) (32) t 0 1 2 n

In this embodiment, a digital screen is selected, known as an equalizing screen, with the memory operation afc selected to optimize the operation of the screen. Optimal conditions are achieved when the ratio of the signal to the noise at the output of the screen 170 has its maximum value.

For a description of equalizing sieves, see, for example, a publication by Sven Treitel and E.A. Robinson on "Optimum 35 Digital Filters for Signal-to-Noise Ratio Enhancement", Geophysical 8004599 48

Prospecting Vol. 17, no. 3, 1969, pp. 248-293, or a publication by E.A. Robinson on "Statustucal Communication and Detection with Special Reference to Digital Data Processing of Radar and Seismic Signals", Hafner Publishing Company, New York, N.Y. 1967, biz. 250-269). The memory operation afc of the equalizing screen 170 is arranged to be adjustable so as to ensure optimal conditions in the operation of the screen at all times during the measurement operations. The control of the screen is accomplished by means of a computer 172 which receives appropriate data from a storage and recall element 173 in a manner to be described below.

A signal y obtained at the output line 174 of the equalizing screen 1'70 can be expressed as a mixture of the input operation xfc and the memory operation afc. So: 15 yt + xt \ = aQxt + + - + Vt- „(33) in which the asterisk indicates a mixture. By substitution in (33) of x + b + u:. t t t yt = ct + \ (34) where: 20 c = b * a (35) t t t is the sieve response on a pure signal input, and v = u * a (36) y t t is the noise output. A block diagram indicating these relationships is shown in Figure 11.

In order to ensure the optimal conditions in the operation of the equalizing screen 170, a certain moment, for example the moment t = t ^, is selected, in which it is necessary that the instantaneous energy in the screen output, which contains a signal at the moment t = t ^, is as large as possible with respect to the average energy in the screened noise at that time. Therefore, in order to detect the signal c in the screened output ufc, the ratio of the signal to the noise is used, as determined by: 2 ^ _ (Value of the signal at time t ^) (37)

Screened noise energy.

800 4 5 99 49 if the signal (b0, b ,, ...... b) with the length (n + 1), 0 1 n is mixed with the sieve with the length (n + 1), an output series ( c_, c ,, ..... c, ....., c „., c„) with a length of (2n + 1) ver U 1 η 2n-1 2n, where Cn is the mean value of this output sequence. At the 5 moment t. = t, therefore becomes: 3 On 2 2 c (anb + a.b. + ... + a b.) u. n. ° n 1 _n ° (38) {Ev ^} E {v ^} 2 η n where E {v} is the mean value of the noise output energy. n

It is hereby assumed that the background noise is ufc white noise. Then it can be demonstrated (see, for example, a publication by Sven Treitel and E.A. Robinson "Optimum Digital Filters for

Signal to Noise Ratio Enhancement ”, Geoph. Prosp., Vol. XVII, No. 3, 1969, biz. 240-293), that the maximum value of the μ ratio of 1 ζ signal to noise can be obtained when: (a_, a.,. ··, a) = (kb, kb., ·. ·, Kb-) (39) 0 1 η η η-1 u in which k is chosen on one. In the presence of a noise-dipped signal, thus, when the noise is white, the optimum conditions are obtained when the screen of the sieve is given by the inverted signal, namely by the coefficient series (b, b b_) .

n n-l u

The memory of the sieve 170 is always determined by means of the memory 172, which is connected to the sieve by a channel 175. The term "channel" refers to appropriate conductors, connectors or transfer means, as may be necessary in a particular case. A storage and recall element 173 is provided for storing the function b ^ for a subsequent transfer of b ^ through the channel 176 to the computer 172. The operation of the computer consists of inverting the input data expressed by a sequence (b ^, b ^, ..., bn) for providing a sequence 0t> n, _____ feg) to its output channel 175, which in turn is applied to the equalizing screen through channel 175 and therein is stored as a memory of the sieve according to the equation (39).

The screened output y ^, obtained at the output line 800 4 5 99 κ τ 50 174 of the equalizing screen 170 is passed to a digital-to-analog (D / A) converter 181. Because y represents a signal in digitized form, the corresponding analog function, obtained at the output line 182 of the D / A converter 5 181, is expressed as y (t) according to the symbols used.

It should be noted that maximizing the ratio of the signal to the noise in the screened output y is equivalent to minimizing the noise signal v (or its analog equivalent v (t)) at comparison. 10 with the information carrying signahl c (or its analog equivalent c (t)). So: v (t) ζζ c (t) (40) and y (t) sy, c (t), - <b (t) (41) 15 The output function y (t) of the equalizing sieve, as is thus shown in Fig. 10D is very similar to the function b (t) shown in Fig. 10C.

An important feature of the invention includes storing (for a subsequent displaying) the function b by the storage and recall element 173. The required operation for storing b is now discussed in connection with Fig. 12. The operation consists of a number of steps.

Step (a). Drilling is stopped, ie the bit 31 is lifted a short distance above the bottom, the rotary valve is kept unloaded and the turntable 21 is stopped.

Step (b). The pump 27 continues to operate as during conventional drilling, ie, at a regular pumping speed and pumping pressure, representative of those used during actual measurement during drilling. All other sources of interference, such as electric alternating current consumption of generators, operation of cranes, etc., are stopped. "Heavy" and other sources of noise are eliminated as much as possible in the case of offshore activities (for example, by choosing a foggy day).

800 4 5 99 '* 51 l.

Step (c). As already described and shown in connection with Fig. 5A, the underground coding is determined by a "clock", which is in absolute synchronization with the "whirl" in the surface equipment, therefore, it is possible to determine the surface. making the moment that a single impulse is generated in the subsurface, for example the precursor impulse, and by knowing the transmission speed through the purge column also knowing the exact moment at which the hydraulic impulse is received at the surface, so it is possible receive a single "wave" 10 at the surface and know in advance when the wave will appear in time, although it may be blurred by noise.

In many cases, the single wave jumps out above the noise, making visual observation on an oscilloscope practical. Thus, the current hydraulic condition generated by valve 40 is received by transducer 51 at a known time.

Step (d). The signal, obtained by the transducer 51, is transferred through the screen 150 to selectively transmit frequencies in the range of 0.1 to 10 Hz. Since the drilling is stopped (as outlined in step (a) above), the back ground U (t) is negligible, as a result of which the signal obtained at the output of the sieve 150 is in the form of F ( t) = B (t) + P (t).

Step (e). The signal F (t), obtained from the screen 150, is passed through the delay element 152, the subtractor 160 and the A / D converter 163 in the manner set forth above. During drilling, the signal obtained at the output of the A / D converter 163 is usually in the form of x ^ = + u ^, where u ^ is responsible for the noise resulting from the drilling. Since the drilling is again stopped here, the background noise signal ufc 30 is negligible. Under these circumstances. The signal xfc represents as much as practicable a "noiseless signal" corresponding to a wave representing the information-carrying signal.

Step (f). The function x. ^ b ^ is saved.

tt 35 The steps (a), (b), (c), (d), (e), and (f), 800 45 99 52 * * J (as outlined above) are performed using the control device, such as is shown in Fig. 12. In this arrangement, the output of the A / D converter 163 is applied to the input of the storage and recall element 173, for recording x.rs/b.

t t

It should be noted that in the frequency range the memory function of the equalizing screen 170 can be expressed as: A (f) = e “2irvfn B * (f) (42) 10 where f is the frequency and B (f) is the complex- is conjugated from the Fourier transform of the signal bfc.

Background noise elimination when the noise is white can in some cases be accomplished by an automatic correlator rather than by an equalizing screen, such as the equalizing screen 170 in FIG.

9. To accomplish this, the scheme of FIG. 9 must be modified by removing the equalizing screen 174, the computer 172, and the storage and recall element 173. An automatic correlator is used instead. The input terminals of the automatic correlator are connected to the output lines 164 of the A / D converter 163. At the same time, the output lines of the automatic correlator are connected to the input lines 174 of the D / A converter 181. The output of the D / A converter can be treated by means of delay element 190, polarity reversal element 192, AND gate 193, etc., as shown in FIG. 9. In some cases, the output of D / A converter, however, should be placed directly on a recorder.

Reference is again made to the operating device of FIG. 9. Now, a signal is represented at the output line 182 of the D / A converter 181, represented by a function y (t) shown in FIG. 10D, which shape which is equal to that of the double wave b (t), i.e. y (t) yb (t).

The function y (t)> ^ b (t) represents a single bit in the digitized signal, which bit operates the valve 40. It is clear that such a function is not very easy to display a very short time lapse, corresponding to a single opening and closing of the valve 40. It is therefore, as in step no. 3 set out, needed to transform a double wave in a single short impulse coinciding with the actuation of the valve. This purpose is accomplished by means of a delay element 190 controlled by a clock 191 in conjunction with the polarity reversing element 192 and the AND gate 193 (coincidence circuit) arranged as shown in FIG. 9.

The delay element receives the signal y (t) from the D / A converter 181 via the line 182. This delay element is controlled by the clock 191 so as to obtain a delay equal to the time course T on the output line 195. ^. The delayed function b (t - T), as shown in Fig. 10E, m 15 is continued through line 195 to polarity reversing element 192 to produce an inverted, delayed at output line 197 of element 192, double wave, expressed as -b (t - T), and shown in Fig. 10F. m

The signal -b (t - T) is applied to the AND gate 193 via line 197. At the same time, the signal b (t) is obtained from the D / A converter 181, through the lines 182 and 200 to the AND gate 193. Each of the signals b (t) and -b (t - T) contains pulses which have a positive and negative polarity. By comparing the signal b (t), as in Fig. 10D, with the signal -b (t -T), m 25 as in Fig. 10F, it can be seen that there is only one pulse in Fig.

10D, which coincides in time with the pulse in FIG. 10F. This pulse occurs in the time course from tg to t4 in Fig. 10D and from tg to tjg in Fig. 10F. It should be noted that the moments tg and tg coincide because t_ = t, + T and t_ = t, + T. At similar 3 l m alm

In this way the moments t ^ and t ^ coincide, because t ^ = t ^ + Tn + T

and t, n = t, + T + T. As a result, a single coincident 10 1 n m impulse is obtained from the double wave b (t) shown in FIG.

10G. Accordingly, AND gate 193, which receives signals at its input lines 200 and 197, representing functions b (t) and -b (t - T ^), respectively, generates at its output line 800 4 5 99

i. I

54 210 a single pulse as shown in Fig. 10G.

It is recalled that for the sake of simplicity, in this embodiment, a single pulse is shown, which is produced and substantially coincides with a single opening and closing of the valve. It should be borne in mind that in the actual drilling and simultaneous measurement, an encoded sequence of single pulses is obtained on the output line 210, which sequence represents a measurement performed by a selected sensing means of a selected parameter.

The coded sequence of single pulses obtained at the output line 210 of the AND gate 193 is applied to a D / A converter 211, which is controlled by a clock 212. At the output line 214 of the D / A converter 211, obtained in analog form a signal representing the measurement of the selected parameter. This signal is recorded by means of the recording device 54.

In another embodiment, a cross-correlator may be used in place of an equalizing sieve to eliminate noise. There is a strong analogy between mixing two functions, as shown by equation (20a) and cross-correlation. Cross-correlating one function with another produces the same result as would be produced from one function with another produces the same result as would be produced by passing the first function through a sieve (equalizing sieve), the memory operation of which is the reverse of the second function. (See, for example, a publication by NA Anstey, "Correlation Techniques —A Review," Geoph. Prosp. Vol. 12, 1964, biz. 355-382, or a publication by 30 YW Lee on "Statistical Theory of Communucation, "John Wiley and Sons., New York, NY 1960, biz. 45.).

Fig. 13 shows how the operations, which can be performed by a leveling screen, can also be performed by a cross-correlator 200. The cross-correlator 200 is provided with two input connections 800 4 5 99 55 f 4.

1 201 and 202, and from an input terminal 203. The signal x ^, obtained from the A / D converter 163, is applied to the input terminal 201, the signal b ^, obtained from the storage and recall element 173 is applied to the input terminal 202. Thus, a signal representing the cross-correlation of and b ^ is obtained at the output line 203. It is readily apparent that the cross-correlation signal obtained at the output line 203 is equal to the mix signal y as expressed by equation (33) and produced in FIG. 9 by the equalizing screen 170. The cross-correlation signal is further processed as shown in FIG. 13 in the same manner as the signal obtained by the leveling screen 170 was treated in the apparatus of Fig. 9.

When the background noise is white noise, the automatic 1 ζ 13 correlation q of the noise function is equal to zero for t φ 0. Now, it is considered that the unwanted noise u has a known automatically correlating function q ^, where the coefficients tq not necessarily be zero for t φ 0. This is the case of "auto-correlated noise" as opposed to pure white noise, the only one of which disappears auto-correlation coefficient qQ. A suitable form of an equalizing screen with associated parts is shown in Fig. 14. In this case, it is necessary to store not only the information-carrying signal bfc (for example by means of the element 173) but also the noise signal ^. Accordingly, the arrangement of FIG. 14 includes two storage and recall elements 173 and 224. The storage and recall element 173 performs an operation similar to that of the element denoted by the same reference numerals in FIGS. 9 and 12. It serves to store and then generate function b ^. On the other hand, the operation of the storage and recall element 224 consists of storing and subsequently reproducing the noise function u ^. The data, representing the functions b ^ and ufc, obtained from the storage elements 173 and 224, respectively, is applied through a respective channel 225 and 226 to a computer 228. The operation of the computer 228 is transforming finn k5 99

* J

56 of the input, received from the input channels 225 and 226, in data necessary to determine the memory operation of the equalizing screen 220. The latter data is applied to the equalizing screen 220 through channel 230.

5 The designation is the same as before, except that it should be borne in mind that the noise is no longer white noise. The equalizing sieves discussed here are indeterminate in the sense of an arbitrary gain factor k, which is conveniently set to unity.

10 The same μ definition of the signal-to-noise ratio is used. So: 2 c μ --V (43)

Egg} n

It is desirable to increase μ to a maximum assuming that the input noise u ^ is of the automatically correlated type. It is easy to enter a matrix designation at this point. Let a = (a, a, ..., a) (44) ui η 2Q denote the (η + 1) row vector, which characterizes the memory of the equalizing screen 220. Let further, b = (b, b. .., bj (45) n n-1 0 are the (n + 1) row vector, which determine the time inverse of the signal bfc and let 25 p0 * '* qn • • • q = • • • * q · ·. ΣτΛ _ / n ^ o_ are the (n + 1) at (n + 1) automatic correlation matrix of the noise. Then it can be written: 30 (ab *) (ba ') μ = - (46) aqa' where the accent denotes the matrix transmission.

To maximize a μ, the quantity (46) must be differentiated with respect to the sieve vector a, 800 4 5 99 * 1 57 with the result set to zero.

A relationship is obtained: qa '= b' (47) which can be written out in the form: 5 p0 · · · ζ- ^ o "Ά ~ h Vi. =. (48) • · · 10 q qn; bn hi * 0 n! 0

_ "J L J L J

This is the array formula of a set of (n + 1) linear simultaneous equation in the (n + 1) unknown sieve coefficients (a, a ,, ..., a). The solution of this gives the desired optimally 15 µl equalized sieve in the presence of automatically correlated noise. The equation (48) can be solved by the Wiener-Levinson repetition technique (see N. Levinson "Thë Wiener RMS error criterion in Filter Design and Prediction," Jour. Of Mat. And Phys., 1947, vol. 25, p. 261. -278 and S. Treitel and E-A. Robinson, "Seismic Wave 20

Propagation in Terms of Communication Theory ", Geophysics, 1966,

Full. 31, pp. 17-32). This repetition method is very efficient, so that it is thus possible to calculate equalizing sieves of great length by means of the computer 228. The known quantities in this calculation are the automatic correlation matrix of the noise q 25 and the time inverse of the signal wave b ^ the unknown quantities are the sieve coefficients a ^ _. These sieve quantities represent the memory operation of the equalizing sieve 220. The calculations required to determine the memory operation of the equalizing sieve 220 are performed by the computer 228. The computer receives data from the storage and recall elements 173 and 224 with regarding functions b ^ and u ^, respectively.

Upon receipt of q. the automatic correlation matrix of the noise is calculated, the time inverse of this signal being determined upon receipt of b ^. Then the unknown sieve coefficients afc are calculated and then transferred via the output channel 230 800 4 5 99 58 * Λ Τ ν to the equalizing sieve 220.

The output of the screen 220 is applied to the D / A converter 181 and further treated in the same manner as the output of the equalizing screen 170 was treated in the device of Fig. 59. In the frequency range, the memory operation of the equalizing sieve 220 are expressed as A (f) = e -2 ï ï n n n (49 (49) Q (f) where B (f) is the Fourier transform of the time inverse of the signal b = (b ^, b ^,. .., b ^) and Q (f) the energy spectrum of the noise over time (f + df). The physical meaning of the expression (49) is simple. The larger the amplitude spectrum | B (f) | of the signal and the smaller the energy density spectrum Q (f) of the time course noise (f, f + df), the more the equalizing screen transmits frequencies in that time course. Thus, if the energy spectrum density Q (f) of the noise is small in a time course of the frequency band occupied by the signal, the equalizing screen is substantially transmissive (attenuates 2Q very little) in this time course.

Signal storage and recall elements 173 and 224 are now considered. The operations required to store the signal b by means of the element 173 have been previously described in connection with steps (a) to (f) as performed by the arrangement of Fig. 12.

Another approach is needed to store the noise signal ^ by means of element 224. As noted above in connection with Fig. 12, it is possible to receive and store a "noiseless signal". Due to the synchronization between the subterranean and surface "clocks", it is similarly possible to receive and store "signalless noise", i.e. the signal received by the transducer 51 during the usual drilling (which signal all types noise coincident with this drilling, but no information carrying signal). In this case, the device of Fig. 12 can also be used to clarify the required operations. The steps for obtaining a registration of the function u (t) 800 4 5 99 59 * * * l can be set as follows.

Step (a). Weight is placed on the chisel and the usual drilling is performed.

5 Step (g). A moment is chosen when no information carrying signal is present, i.e. a rest between binary words.

Step (γ). A signal is obtained at the transducer 51, which represents a pressure change of the drilling fluid. This signal is transmitted through the sieve 150. Due to the moment selected in the previous step (β), the signal b (t) does not exist, so that the signal obtained from the output of the screen 150 is in the form F (t) = P (t) + U ( t).

Step (5). Pump noise signal P (t) is eliminated. This is accomplished by means of the delay element 152 and the subtractor 160. Then the obtained signal is applied to the A / D converter 163. Since no information carrying signal is present, bt = 0, and consequently it has the output. signal obtained from the A / D converter 163 has the form = ufc.

20 Step (ε). A recording of the function x = ufc is obtained by using the storage and recall element 224 at the output of the A / D converter 163, as shown in Fig. 12.

Summarizing the above, it is clear that if the noise is white, the equalizing screen 170 and related parts, as shown in Fig. 9, then guarantee the optimal value of the μ signal to noise ratio. If the noise is not white but has a known automatic correlation effect, the equalizing screen 220 and associated components, as shown in Fig. 14, then guarantee the optimum value of μ.

Fig. 15 shows a portion of the surface equipment including a screen operating on a principle different from that of the leveling screen of FIG. 9 or in FIG. 14. The leveling screen in FIG. 9 or FIG. 14 is optimal in the sense that it is a linear screen which optimizes the signal to noise ratio 8004599 * 60. On the other hand, the sieve 240 in Fig. 15, referred to as an impulse sieve or Wiener sieve, is optimal in that it is a linear sieve, making the mean difference between a desired output and an actual output to a miniature -5 mum limited. For a description of such a sieve, see, for example, the publication by E.A. Robinson and Sven Treitel on "Principals of Digital Wiener Filtering", Geophysical Prospecting 15, 1967, biz. 312-333 or a publication by Sven Treitel and E.A. Robinson on "The Design of High-Resolution Digital Filters", 10 IEEE Transactions on Geoscience Electronics, Vol. GE-4, No. 1, 1966, biz. 25-38.

The pulse-forming screen 240 in Fig. 15 receives data via its input channel regarding the function xfc = b ^ + ufc obtained from the A / D converter 163. The pulse-forming screen is a screen 15 of (m + 1) length , provided with a memory: f = (f, f ,, ..., f) (50) toim representing the (n + 1) length input - (x ^, x ^, ..., xn) in the energy sense of the smallest error turnover in a (m + n + 1) length output z = (z „. z ,, ..., z). A model for such a screen is shown in fig. 16. In this model three signals are present, namely (1) the input signal xfc, (2) the actual output signal z and (3) the desired output signal b. The signal b is a double wave, as in Fig. 10C.

The output signal z ^ is a mixture of the screen memory-25 function ft with the input function xfc, that is: zt ft * xt (51)

The difficulty is to determine the memory function f ^ such that the actual output z ^ _ (in the energy sense of the smallest error) is as close as possible to the desired output b ^ _. To select the memory function, the following quantity is minimized: I = sum of the squares of the errors between the desired output and the sieved signal wave + μ (energy of the sieved noise), 35 where y is a predetermined weighing parameter .

The calculations required to limit I to a minimum of 800 45 99 61 1 are performed by computer 245, which is provided with three input channels 246, 247 and 248, respectively. A storage and recall element 173 transmits channel 246 to computer 245 has data related to function b ^. Similarly, the storage and recall element 224 through the channel 247 transmits to the computer 245 data relating to the function u ^. The channel 248 is used to transmit to the computer 245 data relating to the function x ^, which data is also applied to the input line 241 of the pulse-forming screen 240.

Upon receiving the input signals bfc, u ^ _ and x ^ _, which are applied through channels 246, 247 and 248, respectively, the computer 245 can perform certain calculations described below and through the output channel 251 to the pulse The forming screen 249 transmits the required data regarding the memory function of the screen 240. The actual sieve output z ^ is therefore as close as possible to the desired output b ^ in the energy sense of the smallest error. In other words, 8t bt (52) 20 as shown in Fig. 10D.

Now, in more detail, the operations performed by means of the computer 245 are considered. In symbols, the quantity I, which must be kept to a minimum, is equal to: 25 m + n I = y (bfc - zt> 2 + v E {v2} (53) t = o in which the notation E {} denotes the assembly mean, and m _ 30 Tt = 4rr Vs represents the screened noise. By simplifying the expression for I, we obtain: β Λ Λ L c no 35 1 '»62

Jfcfcn-. , m v 2 m m 1V ibt - /. fsxt-s) + v T_ y fsqt-sft (54> t = Q s-0 / s5> èö

Where 5 q = E {u u} (55) 3 t-s τ-s τ-t where τ is an apparent time index, and q is the automatic correlation

w S

is of the received noise. Differentiating the expression for I with respect to each of the sieving coefficients and setting the derivatives equal to zero has a set of simultaneous equations, which are -JB-f r + v q. = g. (56) / _ s t-s t-s 3t s = 0 are for t = 1,2, ..., m. In the previous equations, the 15 quantities r, q and g are known, the quantities f unknown

t * "S u S

to be. Calculations performed by computer 245 serve to determine the parameters r, q and g of the input functions, * t S u S w applied to channels 248, 247 and 246, respectively, and then solve the equations (56 ) for the unknown quantities 20 f · The parameters r, q,, v, and g are determined as follows.

S t ** S u ™ S t

The parameter r1 is the automatic correlation of the input sig-t-s sew xfc, which is applied by the channel 248 to the computer 245.

The parameter q is the automatic correlation of the noise signal u> * s

Uj_, which is applied to the computer 245 through the channel 247. The parameters gfc are determined as the cross product coefficients between the desired output b and the input x. So, g. = / bx (57) 3t f_ s st s = 0 30 for t = 0, 1, 2, m. In the expression for gfc, the desired output b is applied through channel 246 to computer 245, 5 where the input x ^ is applied through channel 248. The parameter v is a weight parameter, to which an appropriate value is assigned, as discussed below.

The parameters r ^ g, qt_g and gfc are thus determined by 800 45 99 63

t I

((the computer 245, after which the computer solves the equations to produce the quantities f) at the output signal 251. These quantities are applied to the memory of the pulse-forming screen 240. The actual output z of the screen 240 is in the 5 energy sense of the smallest error as close as possible to the desired output b ^.

Because the matrix of the equation, namely the matrix fr, + vq ^ 1, is in the form of an automatic correlation matrix,

t t-s ^ t-sJ

these equations can be effectively solved by the repeating method. This repetition method is described in the following two publications: N. Levinson, "The Wiener RMS (root mean square criterion) in Filter Design and Prediction", Appendix B of N. Wiener, "Extrapolation, Interpolation, and Smoothing of Stationary Time Series" , John Wiley, New York, NY 1949, and Enders A. Robinson 15 on "Statistical Communication and Detection with Special Reference on Digital Data Processing of Radar and Seismic Signals", biz. 274-279, Hafner Publishing Company, New York, N.Y. 1967.

It should be noted that the time it takes for the apparatus to solve the foregoing simultaneous equations for a sieve with m coefficients is proportional to 2.3 m for the repeat method compared to m for the conventional method of solving simultaneous comparisons.

Another advantage of using this repeating method is that it requires only one computer storage space which is proportional to m instead of m, as in the case of conventional methods.

Two conditions must be considered when designing an impulse-forming screen, namely (a) to form the function zfc as close as possible into the desired function b ^ _, and (b) to produce as little output energy as possible when the undesired solid noise is the only input to that.

In many practical circumstances, a screen is required to perform both of the aforementioned conditions simultaneously, so that the problem of finding some suitable ennlς Q9 64 * 1 * compromise between these two conditions is present. Therefore, an appropriate value is chosen for the parameter v, which determines the mutual weighing between these two conditions.

There are circumstances where the value zero is assigned to v. In such a case, the expression (53) takes on a simpler form, namely m + n I 0> t-zt) 2 (58) t = 0 10 wherein the computer 245 does not need the data that you represent. In such a case, the storage and recall element 224 shown in Fig. 15 is removed, so that the computer 245 has only two input channels, namely channel 246 and channel 248.

It should now be noted that the operation of an impulse-forming screen and that of a leveling screen are not exactly the same, that is, the outputs of these screens are not the same for a given input. The expression that applies to a leveling screen has been used above to indicate that the signal expressed by y (representing the output of a leveling screen) is close to the double wave b. Accordingly, it has been noted that the same graph in Fig. 10D represents the functions y (t) as well as the functions b (t). It should also be noted that the expression z ^ / v- * b ^, which applies to an impulse-forming screen, has been used above to indicate that the signal expressed by zfc (representing the output of an impulse-forming screen) close to the double wave b ^. Accordingly, it has been noted that the same graph in Fig. 10D represents the function z (t) as well as the function b (t).

Strictly speaking, the same graph in Fig. 10D should not be used to represent functions b (t), y (t) and z (t). However, since both y (t) and z (t) are close to b (t), it is considered correct for the explanation to be the same graph of FIG.

10D to discuss the operation of a similar sieve and that of an impulse-forming sieve.

800 4 5 99 1 7 l 65

The operating device shown in Fig. 17 will now be considered. Both the information carrying signal b (t) and the noise signal u (t) are obtained at the output line 162 of the subtractor 160. The signal b (t) is the double wave, as shown in Fig. 10C. The mixing of the signals b (t) and u (t) is applied to the A / D converter 163, producing digitized signals bfc and ufc on the output line 164 of the converter, which signals correspond to the analog signals bfc, respectively. and you ^. The mixing of these two signals bfc and uj is in turn applied to the input line 300 of a contraction sieve 351.

The contraction sieve is a special case of a Wiener impulse-forming sieve where the desired shape is simply a contraction. For a description of a contraction sieve, see, for example, the publication by S. Treiel and E.A. Robinson on "The Design of 15 High-Resolution Digital Filter", IEEE Transactions on Geoscience Electrnics, Vol. ¢ $ -4, no. 1, 1966 pp. 25-38.

It should now be remembered that a double wave b (t) as shown in Fig. IOC consists of two valve waves, ie a valve wave A and a valve wave B. The valve wave 20 B follows the valve wave A after a time T. The functioning of the

P

drawing screen to be used in the embodiment of Fig. 17 consists of transforming valve wave A as well as valve wave B into an associated clearly resolved contraction. Thus, a double valve wave bfc is converted into a pair of contractions by means of the compression screen 351.

18A to 18F show six possible locations of a pair of contractions (such as and N ^) with respect to the double wavelet, respectively, applied to the input terminal 300 of the contraction screen 351. It is assumed that T is the time

JC

30 is between the contractions and, which time course is the same in all Figures 18A to 18F. It is assumed that H ^ is the intersection of the X axis contraction (expressed in ms). Thus, the distance OH ^ (in ms) represents the time delay of the double wave contractions. Accordingly, for the time delay in FIG. 18A, OH ^ = 800, 5, 99, 66 t, i.e., that the first contraction is placed at the very beginning of the double wave. The five cases shown in Figures 18B to 18F correspond to increasing values of the time delay OH ^. One of these figures represents the optimal value of the time delay, for which the contraction sieve solution is highest. For such an optimal time delay, the output signal obtained from the contraction screen is remarkably sharper than for any other time delay. One way of obtaining the optimum value of the time delay, the optimal length of the sieve memory and the optimal value of the time course T ^ is described below.

A double contraction, obtained at the output terminal of the contraction sieve 351, represents a single 15 bit in the digitized signal operating the valve 40. As noted in conjunction with Fig. 9, it is desirable to transform a double contraction into a single contraction or pulse. Here, a treatment system similar to that in Fig. 9. is applied. Accordingly, a delay element 303 is provided, controlled by a clock 304 in conjunction with a polarity reversal element 306 and an AND gate (coincidence circuit) 307. These are on a arranged similarly as shown in Fig. 9. However, the amount of delay in Fig. 17 differs from that of Fig. 9.

Specifically, the delay element 303 in FIG. 17 must produce an output 25 which is delayed to the extent with respect to the input signal, in FIG. 9 being the delay T produced by the corresponding delay element 193.

An encoded sequence of single pulses, obtained at the output line of AND gate 307, is applied to a D / A converter 308, controlled by a clock 309. At the output line of the D / A converter 308, obtained in analog form a signal representing the measurement of a selected parameter in the borehole. This signal is recorded by means of the recording device 54.

It should be noted that in certain cases depending on the particular electronic circuit selected for the various blocks shown in FIG. 17, the polarity reversing element 306 may not be necessary because the operation thereof can be performed by an appropriate design of the EN -5 gate.

Fig. 19 shows another embodiment for eliminating noise by means of a contraction screen. In Fig. 17, a special means is provided for eliminating the pump noise (i.e. the retarding element 152 in conjunction with the subtractor 160). In Figure 19, on the other hand, the noise cancellation treatment is simplified. Thus, the signal processing using a delay element 152 and a subtractor 160 is canceled. Accordingly, the signal F (t) obtained at the output terminal 151 of the screen 150 in FIG. 19 is digitized by means of an A / D converter 350 and then applied to a contraction screen 351a. The contraction sieve 351a is designed differently from the contraction sieve 351 of Fig. 17. In Fig. 17, the contraction sieve 351 is designed to convert a double wave, as shown in Figs. ISA to 18F, in a pair of contractions, 20 of separated by a time course T ^. In contrast, the contraction sieve 351a in Fig. 19 is designed to convert a single valve wave into a single contraction. Different locations of a single contraction with respect to a single valve wave are shown in Figs. 20A to 2OP.

It should now be recalled that each single valve wave applied to the input terminal of the screen 351a and each single contraction obtained from the output terminal of the screen 351a represents a single bit in the digitized signals operating the valve 40 . The coded sequence of the contractions in the digitized format, obtained from the output terminal of the contraction screen 351a, is then applied to a D / A converter 352, where it is transformed into a coded sequence of contractions, each contracting a represents only bit of the information encoded with the underground measuring instruments. The sequence 800 4 5 99 68 t t t * of these bits represents in a digital format the measurement of the selected parameter. However, it is necessary for recording and / or reproducing purposes to represent this measurement in an analog form. Accordingly, the signal obtained from D / A converter 352 is applied to a D / A converter 362 to produce a signal at the output of converter 362 having a magnitude representing the measurement of the selected parameter . This signal is recorded by means of the registration key 54.

It should be noted that converting a double wave into two contractions by means of the contraction sieve 351, as in Fig. 17, or converting a single valve wave into a single contraction by means of the contraction sieve 351a, as in Fig. 17. 19, can only be accessed. A pure contraction, ie a delta function, cannot be obtained. However, the object of the invention is to increase the solution, i.e. to obtain an output signal which is considerably sharper than the input signal.

The manner in which a contraction sieve must be designed is now considered. In theory, this object can be accurately achieved if a screen could be used whose memory function can be infinitely long. Generally, for accurate sieving action, it is also necessary to delay the desired contractions by an infinite amount of time with respect to the input wave. See the publication by J.C. Claerbout and E.A. Robinson on "The Error in Least Squares Inverse Filtering", Geophysics, Vol. 29, 1964, pp. 118-120. In practice it is necessary to design a digital screen, the memory function of which has a finite duration, so that at best the purpose can only be achieved by approximation.

It is believed that for practical reasons it is desirable to consider a screen having a memory function on the order of the duration of an input wave. It is believed that the desired contraction can be freely positioned at any location 35. For example, FIGS. 18A through 18F show six possible locations of contractions for a contraction sieve 301 of FIG. 17. Similarly, FIGS. 20A through 20F show six possible locations of contractions. for the compression screen 351 of Fig. 19. The optimal location of contractions 5 has been determined for each of these cases. It should be noted that the location of the contraction is an important factor controlling the fidelity with which the actual output resembles the desired contraction.

A contraction sieve is a special case of a Wiener impulse-forming sieve, as described above. As a result, the operations required to design such a screen are analogous to those described above. It is important to determine the least error energy for a sieve, the output of which is a contraction.

In order to determine the optimal value of the time delay and the optimal length of the memory function for the contraction sieve 301 in Fig. 17, it is necessary to obtain a registration of a double wave b ^ (which is a digital version of b (t)) . The necessary steps for obtaining such a registration, ie steps (a), (b), (c), (d), (e) and (f) have already been described with reference to fig. 12. Recording ban bfc is thus stored in the element 173 in the device of Fig. 12. In order to determine the optimal value of the time delay and the optimal length of the memory function for the contraction sieve 351a, it is similarly necessary to obtain registration of a single valve wave (which is a digital version of B (t)).

The contraction sieve 351a is now considered in Fig. 19. Different locations of a contraction corresponding to different delays (Fig. 20A to 20F) can be expressed as (1.0.0, ...... 0.0): Zero index contraction or zero delay contraction sieve.

(0,1,0, ...... 1,0): Contraction on time index (m + n-1) or contraction sieve with (m + n-1) delay.

«NfU599>" 70 (0.0, ......... 0.1): Contraction on time index (m + n) or contraction sieve with (m + n) delay.

The operation of a contraction sieve, corresponding to the different delays, is schematically shown in Figs. 21A, 21B and 21C. In all these figures, the input wave is the same, i.e. the valve wave Bt, which has been recorded and stored in the manner set out above. The desired output in Fig. 21A is a contraction (1,0,0,) that is, a contraction with a zero delay. The corresponding memory function for a zero delay contraction sieve is F ° = F °, F °, F °, ....... F °) where the actual output is „o / r, o„ o o.

t 1 2 n

A similar notation applicable to Figures 21B and 21C is shown in these Figures. An energy error E corresponds to each place of the contraction. The normalized minimum energy error E represents a very convenient way of measuring the performance of a Wiener pulse-forming screen, and more particularly of a contraction screen. When the screen is fully operational, E = 0, which means that the desired and actual screen outputs for all values of time match. On the other hand, the case E = 1 corresponds to the worst case, ie there is absolutely no agreement between the desired and actual outputs. Instead of the quantity E, it is desirable to consider the complement of E to 1, which is called the sieving parameter P.

25 P = 1 - E (46)

Perfect sieving occurs when P = 1, the worst possible condition occurs when P = 0.

Fig. 22 schematically shows the method for measuring the operating parameter P. A computer 400 includes three input channels 401, 402 and 404. The input channel 4ol receives from the storage and recall element 403 data representing a valve wave, wherein the input channel 402 of the time delay control 405, receives data regarding contractions for different time delays, and the input channel 404 receives data from the memory duration control 406 regarding 800 4 5 99 tt 71 to contractions for different memory durations. The output at 410 of the computer 400 provides a measurement of the operating parameter P by means of a meter 411.

For a constant sieving time it could be expected that at least one value of the delay time should be present, P being as large as possible. In Fig. 23, a graph of P is plotted versus the delay time of starting contractions for a family of seven of a fixed duration. It can be observed that the highest point of the curve (point M ^) 10 corresponds to a time delay ON ^, the choice of this time leading to a screen with an optimal time delay. It must be remembered that the curve in Figure 23 refers to a screen with a fixed duration.

It also shows what happens when the screen memory duration 15 is extended with a constant time delay. Fig. 24 shows a graph of P plotted against the screen length for a desired and a fixed contraction time delay. It can be observed that this curve is monotone, and asymptotically approaches the greatest value of P as the sieve length increases. The graphs 20 as shown in FIGS. 23 and 24 are obtained by the schematic shown in FIG. 22.

The two main design criteria discussed are screen time delay and screen memory duration. Operation can always be improved by extending the memory function duration, however, physical considerations prevent making this duration indefinitely long. On the other hand, the desired exit time delay can be searched, leading to the highest P value for a given selected sieve duration. This time delay in the screen output does not in any way impair the screen output and can drastically improve it.

The sieving parameter P as a function of the time delay and constant duration (Fig. 23) or the parameter P as a function of the sieve memory duration for a constant time delay (Fig. 24) are useful but do not tell the whole story. Ideally, the dependence of 800 4 5 99 72 · * Λ i 'Ρ should be explored on the time delay and memory duration for all physically reasonable values of these variables.

One way to do this is to plot P by taking the sieve delay as ordinates and the sieve memory duration as X axis. The series of P values can then be provided with contour lines, so that it is possible to see at a glance which combination of time delay and memory duration gives an optimal sieving effect. Such a contour line map is shown in Fig. 25. The map only shows the contour for P ^, P ^ and P ^. Of course, the greatest interest is in the larger P values, because it is in that range that the best sieving effect is obtained. This representation allows research to choose the best combination of screen time delay and memory duration.

Although in the examples shown, distance measurement set 15 has been described using a binary code system, other codes are sometimes more suitable. For example, for a gamma ray sensing means or an electronic compass inclinometer, an impulse time code may be preferred. In certain cases, especially when sequential transfer of a plurality of numbers is required, an impulse time code has advantages.

For certain electronic compass devices, it is necessary to transmit five numbers sequentially in order to measure magnetic stretch. By using a distance measuring system based on an impulse time code, significant savings can be achieved in both the energy required by the battery and the time required to transfer the data.

A conventional impulse time code transmission system is shown in Fig. 26A (for example, to transfer the values of three parameters). A series of voltage-30 pulses are transmitted, the duration (t, t, t) of 1 j each pulse a, b, c representative (e.g. proportional or inversely proportional) for the size of the parameter being transmitted. It should be noted that a rest period is required between each pulse to separate the end of one pulse from the beginning of the next. Thus, in Fig. 26A, the pulses a, b, c 800 4 5 99 73 * * * »* are somewhat analogous to three binary" words ", each separated from the next by a time course T. These rest periods are of course a disadvantage for the fast transfer of data, because the rest period itself carries no information. Furthermore, pulses of long duration conflict with the present distance measuring system.

The pulse time code is shown as shown in Fig. 26B. In this system, it is not the duration of the pulse, which is a measure of the parameter, but the time between successive very short pulses. Instead of transmitting long pulses of variable duration, only short pulses of substantially constant duration (in the present distance measuring system, pulses lasting several ms) are transmitted, the time between the pulses being the measure of magnitude of the parameter. Thus, no time is required to separate one time course (representing a para-15 meters) from the next. In Fig. 26B, parameter No. 1 represented by the time (t ^) between the pulse PQ and the pulse P ^. The parameter No. 2 is represented by the time (t ^) between pulse P ^ and pulse P ^ and parameter No. 3 by the time (t3) between the pulse P ^ and the pulse P ^. It can be seen that in the previous example the pulse P ^ represents the end of the time course t ^ and also the beginning of the time course t ^ r and the pulse P3 represents the end of the time course t ^ and also the start of the time course t ^ r. time lapse t1, etc. Thus, no time is lost between any significant time lapse (ie T: of Fig. 26A is zero).

It is clear that by applying the pulses P, P2 /? 3 for both indicating the end of one time lapse and the start of the next time lapse, the lost time (unused time) is zero, with all time, used for data transfer (ie identification of the time courses t ^, t ^, t ^) is useful time. Expressed in a binary code, each "word" (identifying a number) is followed immediately by the following * "word", etc. Only at the end of a series of transmissions is a rest T, and the sequence is repeated. In the following series, the time courses between Pq, P ^, P ^ t 800 4 5 99 1 · 74 P3 are, of course, slightly different, because the data represented by times t ^, t ^, t ^ is usually variable with time with each new transferred data load representing, for example, a new state in the borehole.

Pig. 30 shows the principles of circuitry which the present impuks time code can accomplish. Naturally, modern electronic integrated circuits are used in the borehole tool used in practice (see also fig. 29).

For simplicity, a simple mechanical step switch 10 and a simple mechanical relay are described so that the principles of system logic can be easily clarified.

In Fig. 30, sensors are connected to terminals 1, 2, 3 of the step switch 285, which has an electromagnetic control winding 286, as shown. It is assumed that the sequence is started with the step switch in the "0" position, as shown in FIG. 30. The battery 288 generates a DC comparison voltage. This DC voltage appears across the resistor 289 and leaves the capacitor 290 at a predetermined speed, determined by the value of the resistor 289, the size of the capacitor 290, and the voltage of the battery 288.291 is a trigger circuit, which is one generates some sharp electrical pulse when the voltage applied to its input exceeds a predetermined value (trigger voltage). The output of the trigger circuit 291 activates the winding 286, the arm 287 of the step switch 285 moving to the next contact (No. 1 in this case). Simultaneously, the trigger circuit 291 currently operates the relay 292, which discharges capacitor 290 to ground.

When the arm 287 is moved from the "0" position to the "1" position, the operations are repeated except that the voltage output of the sensing member No. 1 is connected to the circuit instead of the comparative voltage of the battery 288 the pulse being generated the moment the capacitor returns to the trigger voltage of the trigger circuit 291. This moment is also

RC

relative to the value (-) where R is the ohmic value of the resistor 289, C the capacitance of the capacitor 290 and Vg the output 800 4 5 99 '75 i>

I

voltage of the observer. Thus, the time is inversely proportional to the output voltage of the detector.

After activation of the trigger circuit 291 by the voltage of the detector No. 1, the operation is repeated, again with the voltage on the capacitor 290 reaching the trigger voltage again, the trigger circuit 291 generates a sharp pulse which actuates the relay 292, the capacitor 290 discharges and the step switch 285 is energized and the arm 287 moves to the next contact.

Thus, the step switch 285 steps in sequence and connects the sensing members 1, 2, 3 one after the other to the resistor 289. The impulse generated by the trigger circuit 291 when the arm 287 is in the "0" position corresponds to the imouls P ^ (of Fig. 26B), wherein the pulses generated by the trigger chain when the arm 287 is in the respective positions "1", "2", "3" correspond to the respective pulses P ^, and P3 ( of Fig. 26B). The corresponding time courses t ^, tg are representative (inversely proportional) to the voltage outputs of the sensing means No. 1, No. 2, No. 3.

The foregoing paragraphs describe the principle of the pulse time encoder that can be used in the downhole equipment in place of the A / D converter 102 in Figure 4A. Surface decoding can be accomplished by a conventional pulse time decoding circuit and need not be discussed in detail here.

In Fig. 26C, TPQ, TP ^ TP2, TPg etc, ° P ~ represent subsequent pulses received at the surface serving point.

These pulses take place at times T ^,,

Tg, etc. In the pulse time code, as described in connection with Fig. 26B, the time between successive pulses is used to indicate the size of a parameter. Thus, if three parameters are to be measured remotely, the code may be as shown in Fig. 26c, where - Tq is a time course representing parameter No. 1.

35 800 4 5 99 76 Τ2 ~ T1 is a time course representing the parameter No. 2, T3 - is a time course representing the parameter No. 3.

5 When measuring pulses in the mud during drilling, it is in certain cases necessary that the measurements are carried out with great accuracy. Since the sound velocities in the purge column are not always equal, and noise and thawing conditions are variable, the time course between impulse received at the surface is not always accurate in accordance with the time course between the corresponding pulses generated at the " downhole equipment. In other words, there is often uncertainty on the surface as to the exact moment when a certain impulse arrives.

It is assumed that the absolute uncertainty of the arrival time of each pulse is plus or minus 0.2 s, or a total of 0.4 s. To achieve an accuracy of + 1% for with a total absolute error of 0.4 s, the time between pulses should be at least 0.4 x 100 or 40 s. Furthermore, because the device can sometimes fail to develop a clear, sharp pulse, at least two observations (time bases) are required. If both time bases give the same answer, the data is (verified). Therefore, to achieve the desired accuracy and certainty (+ 1% accuracy in a practical case), approximately 80 to 120 s are required per measured parameter (i.e., about 2 min per parameter).

In the improved pulse time code, an addition is proposed, which in many cases can result in much greater accuracy. It is proposed not to use a single flush pressure pulse for each im-30 pulse Ρ ^, P ^, $ 2 'P3 transmitted but a group of at least three mutually unevenly spaced flush pressure pulses, as shown in Fig. 26D (hereinafter referred to as a three-prong group).

The time distances in each tripartite group are set at 35 The time from the first impulse to the second = t ^.

800 4 5 99 1 '* 77

The time from the second impulse to the third = t ^.

The time from the first impulse to the third = t ^.

In this state, again the arrival time of the three-member group TP ^, the arrival time of the three-member group TP ^, the arrival time of the three-member group TP2, and T3 arrival time of the three-member group where - Tq is a time course, that the parameter no. 1 represents.

T2 - T1 is a time course representing the parameter No. 2 10 and a time course representing the parameter No. 3.

The advantage of this system is that in the case of a current failure, as a result of which one pulse in the group is not received, the failure can be immediately recognized, because a tripartite group contains two pulses instead of three. Furthermore, because the times t ^,, t ^ are uneven and known, it is possible to determine which impulse is missing in the group, and because t ^, t2, t ^ are also known, the correct correction can be made and the times - T ^, 20 - T2, T2 - can be determined with the same accuracy as in the case where all pulses are present in the three-prong group. The tripartite system has a further advantage.

Because it is difficult to determine the accurate arrival time of a given impulse, the three-pronged group allows considerably more accurate determination of the arrival time. For example, the arithmetic average of the arrival times of each impulse in the three-prong group can be obtained or even greater accuracy of the arrival time can be obtained using modern computer techniques.

FIG. 29 shows a block diagram of an electronic downhole logic system generating the three-prong group pulses shown in FIG. 26D.

Reference numeral 101 is a sensing means (see FIG.

4A), which generates an electrical voltage indicative of the size of a "downhole" parameter. 601, 602 and 603 are 800 4 5 99% I 78, respectively, a voltage controlled oscillator, a scale member and a trigger circuit which generates in a well known manner a series of electrical pulses separated by time courses indicative of the magnitude of the voltage output 5 of the sensing means 101 and hence of the "downhole" parameter being measured. The time course between the pulses and, as shown in Fig. 26B, is therefore a measure of one parameter measured by one of the sensing members 101 of Fig. 4A.

The portion of Figure 29 enclosed in the broken rectangle shows the circuit details for generating the aforementioned three-prong group pulses. 607, 608 and 609 are electronic "one-shot" univibrators, which, in response to the pulse of the trigger circuit 603, each produce a single output pulse of durations of D1, D1, D1, respectively, as shown in FIG. 29. Blocks 610 are electronic diverters, that is to say they each produce at the output a signal proportional to the first time derivative of the input signal (such electronic devices are well known in the art).

The outputs thereof are thus, as shown in Fig. 29, as 20 G, Η, I, i.e. two pulses of opposite polarity, separated by the respective time courses D 1, D 1 and D 1. The blocks 611 are rectifiers and transmit only the positive pulses appearing at the outputs of the diverters 610. The outputs of the rectifiers 611 are connected in parallel at 612 and produce the signal J, which is the desired signal (also shown in Fig. 26D). Thus, each simple pulse generated by the trigger circuit 603 generates three pulses separated by known and uneven time courses (three-prong group), as shown by J. In practice, the time course is very small compared to D1 and D ^, and only a few ms, where D ^ and D ^ are time courses from a few ms to several hundred ms. It can therefore be assumed in the analysis of the effect that D. = 0.

Thus, in the output shown as J in Fig. 29, the pulse indicates the end of the output pulse of 607 (which, as noted above, is also the beginning of the output pulse for all practical purposes, because its length is assumed to be zero), the pulse p2 is the end of the output pulse of 608 and the pulse p2 is the end of the output pulse of 609.

Therefore (since D ^ is assumed to be zero), the time course t1 = d2 'is the time course t ^ = and the time course t2 = D ^ -D2 · Thus, the portion of Fig. 29 within the broken rectangle creates the three-prong group at its output at 612 on (shown as J in Fig. 29) in response to one single pulse, pressed at its input.

The circuit shown in FIG. 29 may be arranged in FIG. 4A between a selected sensing means 101 and the power controller 104. In other words, when the impulse time code system of FIG. 29 is employed, the A / D converter 102 and eliminated processor 15 (because they are adapted for binary coding), power control 104 being controlled directly by the output of amplifier 613 of FIG. 29.

When the three-part group pulse time code is used in place of the binary code, it is necessary to decode the three-part group signals at the surface. In Figs. 9, 12, 13, 17 and 19, the signals representing the downhole parameter are assumed to be in binary code form. To change the system for receiving signals in the three-prong group pulse time code form, as described in connection with FIG.

29 and 26D, it is necessary to provide a special code translation means between the sieve 150 and the subsequent surface direction, as shown in FIG. 27. For this purpose, the wire 151 in FIGS. 9, 12, 13, 17 and 19 are interrupted and the code translation means is placed therebetween. In some instances, it is more desirable to arrange the code translation means between the subtractor 160 and the A / D converter 163 at the lead 162 of FIGS. 9, 12, 13, 17, the preferred location for those skilled in the art is clear.

Referring to Fig. 27, 316 is a selector 35 designed to generate a single output pulse 800 4 5 99 80

i I

t I

in response to the three-prong group, described in conjunction with Fig. 29. Reference numeral 317 designates a time-to-amplitude converter, that is, an electronic circuit which generates a DC voltage output on wire 319, which output a 5 is predetermined function of the time between two input pulses pressed on its input by wire 318. Such devices are well known in the electronics field and need not be described in detail here. 320 is an analog-to-digital converter and is also well known.

FIG. 28A shows selector 316 in more detail. 321, 322, 323 are one-shot vibrators designed to generate a single output pulse with a selected predetermined period of time responsive to an input pulse. 321 generates a long pulse with a duration of 1 ^, 322 generating a shorter pulse with a duration of 15 I2 and 323 an even shorter output pulse with a duration of 1 ^, as shown above each block 321, 322 and 323. The blocks 324 are deflectors, i.e. electronic circuits, which generate an output proportional to the first time derivative of a signal printed on the input. Such units are also well known and generate output signals, as shown by the curve above each diverter block. The blocks 325 are inverters, that is, they generate an output signal which is a copy of the input signal but inverted in sign, as shown by the curve directly above each inverter.

The blocks 326 each contain a rectifier and generate a single positive electrical pulse at the output, 326a, 326b, 326c, as shown. The blocks 327 are coincidence chains or AND gates, generally known. Each block 327 produces an output pulse at its terminal c only when there is a pulse at input a, and a pulse at input b, which pulses coincide in time. The outputs of all three coincidence circuits 327 are connected in parallel at wire 329 and are applied to the input of the time-to-amplitude converter 317. The time-to-amplitude converter 317 produces a DC output, which is a predetermined function of the time between two successive inputs 800 45 99 81 ί ι '»impulses. The output of the time-to-amplitude converter 317 is connected to the A / D converter 320, which then translates the DC input into binary coded pulses in a manner well known in the art.

The circuit of FIGS. 27 and 28A consists of conventional electronic integrated circuit components which are generally coated. The general operation of the selector needs a more detailed description.

The pulses P ^, P ^, Py generated by the amplifier 613 10 of Figure 29 are pressed on the power controller 104 of Figure 4A. and are transmitted to the surface as rinse pressure pulses by the valve 40. At the surface, these rinse pressure pulses are taken up, for example, by the elements of Fig. 9, which comprise the transducer 51, the screen 150, the retarding element 152, and the subtractor 160. The pulses appearing on lead 162 of Figure 9 (or Figure 12, Figure 13 or Figure 17) are referred to as TP ^, TP ^ e * 1 (and correspond to pulses P ^, P £ and P ^ generated by the "downhole" circuit of FIG. 29.

Figs. 28b, 28C, 28D, 28E show the response of the circuit of Fig. 28 to the pulses TP ^, TP ^ / TP ^. When the pulse TP ^ arrives and is pressed on the wire 152 (or wire 162) of Fig. 28A, all three one-tone vibrators 321, 322, and 323 are activated, each generating a related output pulse, each with its own characteristic and predetermined and fixed lengths of 1 ^, ^ and 1 ^, respectively. Thus, when the pulse TP ^ activates the univibrators, they generate the output voltages (pulses) Aj, B ^, as shown in Fig. 28B.

When the pulse TP ^ arrives, it cannot activate the univibrator 321 because it is already in the ON state.

However, the pulse TP ^ activates the univibrators 322 and 323 because they have returned to the OFF state generating output pulses B1 and as shown in FIG. 28B.

When the pulse TP ^ arrives, it cannot activate the univibrator 321 or 322 because it is already in the ON state. However, the pulse TP3 35 activates the univibrator 323 because it has returned 80 0 4 5 99 * 1 1 82 to the OFF state, generating an output pulse, as shown in Fig. 28B.

The time courses 1 ^, ^ and 1 ^ of the univibrators 321, 322 and 323 in Fig. 28A are sized to correspond to the time delays caused by the operation of the Univibrators 609, 608, 607 of Fig. 29 so that the ends of the group of uni-vibrator pulses of FIG. 28B coincide and the AND gates of FIG.

Activate 28A.

Fig. 28B shows the operating states when all im-1 n pulses TP ^, TP ^ / are present.

Fig. 28C shows the same states as in Fig. 28B, but one of the pulses (e.g. TP ^) is missing.

Fig. 28D shows the same states with one pulse missing TP2, FIG. 28E showing the states when the pulse ^ TP3 is missing. It should be noted that no matter which pulse (TP ^, TP ^ or TP ^) is missing, two univibrator output pulses always terminate at time T. This property of the circuit of Fig. 28A is used to always generate at least two coincident in time. pulses at the moment T miss whatever pulse TP ^, TP ^ or TP ^ 20. As long as at least two of the group of pulses are observed, the moment of occurrence of the output pulse at 329 of Fig. 28A is the same. The single pulse 328a in Fig. 28A is generated when a group of pulses has been received by the surface device, the pulse 328a being present when any two pulses in the group on the surface are sensed.

Referring again to FIG. 28A, block 317 is a conventional time-to-amplitude converter that generates a DC output which has a predetermined function relationship with the time between successive pulses 328 a. 320 is a typical 30 Ω. D converter, and translates the size of this DC voltage output into a binary word. The binary words follow in rapid succession, as determined by the properties of 320 and its corresponding clock.

It is therefore evident that the device of Fig. 28A 35 translates the pulse time code using the three-prong 800 45 99 '' 83 group into a binary code, with the device shown on wires 151 or 162 of the Figures 9, 12, 13 and 17 operate in exactly the same manner as if the data had initially been transferred from the subsurface in binary code form.

In order to obtain the shock waves discussed earlier in the description, certain limits have been set on K. (mean 1 (v) mean rate of change of valve opening) and a (moment of open flow). Investigations have shown that K2 should be at least 5 cm / s and preferably should be in the range of 20 cm / s and 150 cm / s. may not exceed 500 ms and is preferably in the range of 50 ms to 150 ms.

It should be noted that while the synchronization pulses (clock 155) in the examples shown are generated by the generator connected to the pump shaft or by a phase-locked loop, other means may be provided to provide the clock frequency, which is synchronous with the pumping action. For example, the well known pump stroke counter commonly used on the pump connecting rod can be used to generate one electrical impulse per pump stroke. The time between each of such successive pulses can be divided into an appropriate number (eg 512 or 1024) with equal time courses by a microprocessor or by a phase locked loop or by others well known in the field of computers and electronics resources. In such an arrangement, no access is required to the pump drive shaft, the clock frequency, equal to that of the generator 155, being generated by the microprocessor and the pump stroke counter.

The first part of the present description describes in detail the conditions for the occurrence of hydraulic shock waves and associated valve waves. At certain depths, for example shallow depth, conditions may occur that the valve wave, as described above, is not properly formed.

Such a valve wave requires a sufficient volume of mud to flow into the drill pipe and sufficient hydrostatic pressure to be present at the tool end. It is emphasized, 800 4 5 99 84

«I

1 * that the invention is not limited to the particular wave shown and may be applied to other forms of pressure pulses which can be observed at the surface of the soil as a result of the operation of the valve 40.

Various digital sieves, such as equalizing sieves, pulse-forming sieves and contraction sieves have been described in detail above. In particular, the operation of each digital screen is clearly explained by providing a detailed sequence of operations to be performed. These operations 10 are set out and specified by appropriate mathematical formulas. It is clear that by applying modern computer techniques, one skilled in the art can provide the necessary programs on the basis of the teachings provided in the description, wherein in connection with FIGS. 9, 12, 13, 14, 16, 17, 19 , 21 described operations can be performed by an appropriate software.

Various digital screens, as described, can also be used in other forms of transferring measurements by flushing pulses by means other than the bypass valve of the type described. These other forms may include the process by virtue of a controlled restriction of the purge flow cycle through a flow-limiting valve properly located in the main purge flow, as described in U.S. Pat. No. 2,787,795. Generally, the disclosed digital sieve systems can be used in any of the forms of a distance measuring system in measuring during drilling and other forms of measuring, with the drilling equipment removed to lower the measuring equipment into the borehole. The sieve systems can be used in distance measuring systems using pulses representing arbitrary forms of energy, such as electric, electromagnetic, acoustic and other impulses.

The impulse time code, using the three-prong impulse group as described above, can also be used in acoustic well measurement to facilitate the handling of acoustic well measurement signals, and a very 800 effective 5, 85 effective method which allows automatic correction of errors due to pulse skipping when measuring the transit time of acoustic waves. Well acoustic measuring methods and devices are usually designed to measure the transit time of an acoustic wave between a first and a second pulse. In U.S. Pat. No. 3,900,824, it has been proposed to prevent a pulse skip by the measurement performed during a sequence N-1 stored in an auxiliary memory and comparing this measurement with the next measurement (sequence N). The other present method proposed based on the impulse time code is more effective and reliable in correcting measurement errors due to cycle skip.

The three-part impulse group timecode has a very wide field of applications beyond measuring while drilling. This code can be used in any communication system for transferring messages from a sending station to a receiving station, as well as for various types of well measurements (not necessarily when measuring during drilling), such as acoustic measurements.

Obviously, in order to capture and store a wavelet for later use in the digital seven described, on-site steps must be taken, as described. It is sometimes desirable to capture a single wavelet (instead of a double 25). wavelet), as required in the embodiment of Fig. 19, which includes the contraction sieve 351A. For the capture of a single wave, it is advantageous to generate the signal produced by synchronizing the underground equipment with the observation equipment on the surface. This can be done by replacing one of the sensing members 1, 2, 3 and 4 in the underground equipment in Fig. 4A with one, such as a clock or a signal generator controlled at a constant time, which is mutually establishes regularly spaced actuations of the valve 40 of FIG. 4A. Operation is as follows: 35 (a) By stopping and turning on the speoling pumps on the surface in an appropriate order, the switch 91 800 4 5 99 86 * * »(γ of fig. 4A can be forced to change the sensing device ( that is to say, the generator of pulses spaced at regular intervals), so that a sequence of pulses is generated by the valve at known moments, (correction of the path must be made for the travel time of the impulse from the substrate to the surface which is predetermined by well known methods).

(b) The surface equipment is controlled by its own clock, which is synchronized in time and phase with the underground signal transmitter.

(c) Due to the appropriate switchum on the surface, the capture and storage of the double wave can be interrupted, so that the storage chain is connected only during the time of one wave, and is automatically turned off during the occurrence of the second wave. .

Of course, the same operation can be done by hand (by the drill master). This can be easily done when the wavelet is clear and the noise clearly dominates. When the wavelet is immersed in noise, the automatically operating system, 20 as described, is used.

There are two disturbing noise signals, which tend to blur the reception of the useful signal B (t) (see equation 22). One of these represents the pump noise P (t), the other representing the noise U (t) associated with various drilling operations other than the operation of the pump. In order to eliminate these interfering signals, according to the application, three sieve systems are designated, sieve systems No. 1, No. 2 and No. 3.

Screen system No. 1 is the analog screen 150. The purpose of this screen is to suppress the constant component of the transducer output, which component represents the pressure generated by the pump 27 and other frequencies outside the range of interest.

Screen system No. 2 includes the retarding element 152 and the pull-off member 160. The purpose of this system is to suppress or eliminate the pump noise P (t).

800 45 99 87 i * t

Screen No. 3 includes a correlator or a digital screen, which may consist of an equalizing screen, an impulse-forming screen or a contraction screen, and also includes various related elements, such as storage and recall elements, and 5 computers for determining the optimal values of the memory elements for the associated digital sieves (see fig. 9, 12, 13, 14 and 15). The purpose of system No. 3 is to eliminate or suppress the noise U (t).

The screening systems No. 1, No. 2 and No. 3 are connected in series. In the above-described embodiments, the screening system No. 1 is connected to the pressure transmitter 51, the system No. 2 is connected to the output conduit 151 and the system No. 3 to the output conduit 164 of the system No. 2.

Each of the previous sieve systems is a linear system.

The operation of these systems can therefore be interchanged or vice versa. First the sieve system No. 1 can be used, after which the order of the sieve systems No. 2 and No. 3 is reversed.

Also, in certain cases it may not be necessary to use all three screening systems. Any two may suffice, 20 and in some cases only one. Also, the system between wire 182 and wire 210 may sometimes be omitted, and D / A converter 211 may be configured to receive double waves.

When the signal produced by the method described in steps (a) to (f) is captured and stored, it can be correlated with the raw signal generated by the transducer 51 or with the preconditioned signal on the wire 162 of the fig. 9-19. In the case of cross-correlation with the raw signal at the transducer 51, the second wave in the double wave must be eliminated by appropriate means well known in the art so as to allow cross-correlation with the single wave at the transfer of the transferor 51.

800 45 99

Claims (50)

1. Method for performing measuring work in a borehole simultaneously with the work of drilling the hole, which measuring work is carried out by observing a selected parameter at an appropriate depth in the hole, and comprising the step of passing through a transmission channel to the top of the borehole transmitting a valuable measurement consequence having at least two features, the first of which is an indication of the value of the parameter, and the second is independent of the value of the parameter, characterized by producing a first signal representing a superimposing of the valuable measurement consequence and a disturbing measurement consequence generated in the channel and associated with at least certain drilling operations further producing a second signal representing the second property or the interfering measurement consequence, and using this second signal to derive a d from the first signal resulting signal, which represents the valuable measurement consequence. 2. Method for performing measuring work in a borehole simultaneously with the work of drilling the hole, which measuring work is performed by observing a selected parameter at an appropriate depth in the hole, and comprising the step of passing through a transmission channel to the top of the borehole transmitting a valuable measurement consequence for thus producing in the channel a superimposing of the valuable measurement consequence and a disturbing measurement consequence, which disturbing measurement consequence is associated with at least certain drilling operations, characterized by producing a first signal, that represents the superimposing of the valuable measurement consequence and the interfering measurement effect, which interfering measurement consequence is associated with at least certain drilling operations, further producing a second signal representing the interfering effect, and applying the second signal to it from the derive first signal from an erui The resulting signal that represents the valuable measurement consequence. 800 45 99 k> 4 * 3. Method for performing measurement work in a borehole simultaneously with the work for drilling the hole, which measurement work is performed by observing a selected parameter at an appropriate depth in the hole, and comprising the step of passing through a transmission channel to the top of the borehole transmitting a valuable measuring consequence having at least two properties, the first of which is indicative of the value of the parameter, and the second of which is independent of the value of the parameter, characterized by producing a first 10 signal representing a superimposing of the valuable measurement consequence and a disturbing measurement consequence generated in the channel and associated with at least certain drilling operations, further producing the second signal representing the second property and using the second signal for deriving a resultant signal from the first signal already, that it represents valuable measurement consequence. 4. Method for performing drilling operations in a borehole by means of a mud circulating system simultaneously with performing measurements in the hole by observing parameters at different depths in the hole at selected moments and in the system at the selected moments generating mud pressure fluctuations to indicate the magnitudes of the parameters, characterized by producing first signals at times when the drilling operations coincide with measurements in the hole, which first signals superimpose the mud pressure fluctuations and disturbing pressure shocks resulting from at least certain drilling operations, further producing second signals, which represent the disturbing pressure fluctuations, at intervals which do not contain the selected moments, and using the second signals to output from the derive first signals from the result and the signals, which are indicative of the sizes of the parameters. 5. A method for performing drilling operations in a borehole by means of a mud circulation system simultaneously with performing measurements in the hole by observing 800 4 5 99 Γ '1 a selected parameter at an appropriate depth in the hole and generating a wobble pressure fluctuation in the system, said wobble having two properties, the first of which is an indication of the value of the parameter, and the second of which is independent of the value of the parameter, characterized by producing a first signal, which represents a superimposing of the fluctuation of the mud pressure and of disturbing changes of the mud pressure, which disturbing changes are associated with at least certain drilling operations, further producing a second signal representing the second property, and using from the second signal for deriving a resultant signal from the first signal, d at is an indication of the size of the parameter. 6. Method for performing drilling operations in a borehole by means of a mud circulation system simultaneously with measurements in the hole by observing selected parameters at different depths in the hole and generating a sequence in the system at selected moments pressure pulses in accordance with a pattern, which indicates the values of the parameters, characterized by producing first signals at times when the drilling operations coincide with the measuring work, which first signals represent a superimposition of the sequence of pressure pulses and disturbing pressure churns resulting from at least certain drilling operations, further producing second signals, which do not contain the chosen moments, representing the disturbing pressure fluctuations, and using the second signals to extract from the first signals to derive the resulting signal n, which are an indication of the sizes of the parameters. A method of performing well drilling in a borehole by means of a mud circulating system simultaneously with performing measurements in the hole by observing selected parameters at different depths in the hole and generating a sequence of pressure pulses in the system with a pattern indicative of the magnitudes of the parameters, 800 4 5 99 * t 91 characterized by producing a first signal representing a superimposing when the drilling operations coincide with the hole measurement operations of the sequence pulses and disruptive pressure fluctuations resulting from at least certain drilling operations, further producing a second signal representing at least one of the pressure pulses, and using the second signal to derive from the first signal resulting signals indicating the magnitudes of the parameters. 8. Method for performing measurement work simultaneously with drilling work, wherein the drilling work is carried out by using a drilling assembly comprising a drill string having a mud passage, further a pump for drilling mud through the passage, and a drill bit 15 for crushing rock in the borehole, producing pressure fluctuations in the drilling mud due to the work of the drilling assembly, and measuring operations are performed by observing downhole parameters near the bottom of the column and generating a sequence of pressure pulses. 20 according to a pattern representing the magnitudes of the parameters, characterized by producing first signals at times when the drilling operations coincide with the measurement operations, the first signals representing a superimposition of the sequence of pressure pulses and the pressure fluctuations, with the selected between interrupting at least certain drilling operations at intervals, producing second signals at selected intervals representing at least one of the pressure pulses, and combining the first signals with the second signals to obtain resulting signals representing the sequence of pressure pulses . 9. Method for performing measurement work simultaneously with drilling work, which drilling work is performed by means of a drill string, comprising a mud passage, a pump for forcing mud through the passage and back to the surface through an annular space, thereby creating a substantial A mud flush pressure drop is produced between the interior of the 800 4 5 99 -1 i column and the annulus, and a drill bit for crushing rock in the borehole, the measurement work including detecting downhole parameters near the bottom of selected holes at selected times. the column and generating sequences of electrical pulses, which sequences represent the magnitudes of the parameters, characterized by the steps of diverting a portion of the flush from the interior of the column to the annulus in response to the electrical pulses for thus producing sequences at the chosen moments pressure pulses, which represent the magnitudes of the parameters, further produce first signals at times when the drilling operations coincide with the measurement operations, which first signals represent a superimposition of the sequences of mud pressure pulses and of disturbing pressure fluctuations resulting from at least certain drilling operations, producing second signals intermittently, which do not include the selected moments, representing a disturbing pressure fluctuation, and combining first signals with the second signals to obtain resulting signals of the order represent purge pressure pulses. 20 10. Method for performing measurement work simultaneously with drilling work, which drilling work is carried out by means of a drill string, comprising a mud passage, a pump for forcing mud through the passage and back to the surface through an annular space, thereby significant spooling pressure drop is produced between the interior of the column and the annulus, and a drill bit for crushing rock in the borehole, the measurement work comprising sensing downhole parameters near the bottom of the column and generating electrical sequences pulses, which represent the magnitudes of the parameters, characterized by diverting a portion of the mud from the interior of the column to the annulus in response to the electrical pulses, thus producing sequences of mud pressure pulses, representing the magnitudes of the parameters, further h producing first signals representing a superimposing of the sequences flushing pressure pulses and disturbing pressure fluctuations resulting from at least certain drilling operations, producing second signals representing at least one of the pressure pulses, and combining the first signals with the second signals to obtain resulting signals representing the sequence of pulses. 11. Method for performing measurement work simultaneously with drilling work, which drilling work is carried out by means of a drill string, comprising a mud passage, a pump for forcing mud through the passage and back to the surface through an annular space, whereby a significant mud pressure drop is produced between the interior of the column and the annulus, and a drill bit for crushing rock in the borehole, the measurement operations including sensing downhole parameters near the bottom of the column and generating sequences of electrical impulses which represent the magnitude of the parameters characterized by diverting a portion of the mud from the interior of the column to the annulus in response to the electrical pulses to thereby produce mud pressure pulses representing the magnitudes of the parameters, further producing first signals at times when the drilling operations coincide with the measuring operations, the first signals representing a superimposition of the sequences of mud pressure pulses and of disturbing pressure fluctuations resulting from at least certain drilling operations, interrupting at least certain drilling operations at selected intervals , producing second signals, representing at least one of the pressure pulses, at these intervals, and combining the first signals with the second signals to obtain resultant signals, which represent the next flush pressure pulses. 12. System for carrying out measurement work simultaneously with drilling work, which drilling work is carried out by means of a drilling assembly comprising a drill string, comprising a mud passage, forcing drill mud to flow down into a mud circulation system, 80045 99 1 and a drill bit for the crushing of rock in the borehole, the measuring work being carried out by means of a measuring assembly, comprising a probe, arranged near the bottom of the column for generating electrical signals, representing the magnitude of downhole parameters, a controllable means for producing pressure changes in the purge circulation system, and a control element which responds to the electrical signals for applying a sequence of energizing pulses to the controllable means in accordance with an order representing the magnitude of the parameters for it thus in the circulation system at the top of the borehole producing a sequence of pressure pulses corresponding to the energizing pulses, the sequence of pressure pulses representing the values of the parameters, characterized in that a first means is provided for producing first signals representing a superimposing of the pressure pulses and of disturbing pressure fluctuations resulting from at least certain drilling operations, as well as a second means of producing second signals, representing at least one of the pressure pulses, and a third means of combining the first and second signals to produce third signals representing the sequence of pressure pulses. System according to claim 12, characterized in that the third means is a correlator, wherein combining the first and second signals means correlating these signals. System according to claim 12, characterized in that the third means is a screen with an adjustable selectivity, which selectivity is controlled by the second signals. System according to claim 13, characterized in that the screen consists of an impulse-forming screen. A system for performing measurement operations simultaneously with drilling operations, which drilling operations are performed by a drilling assembly comprising a drill string having a mud passage, through which mud drilling is forced to flow downward in a mud circulation system, and a drill bit for crushing rock in the 800 45 99 r borehole, the measuring work being carried out by means of a measuring assembly, comprising a probe, arranged near the bottom of the column for generating electrical signals, representing the magnitude of downhole parameters, a controllable means for producing pressure changes in the flush circulation system, and a control element responsive to the electrical signals for applying a sequence of energizing pulses to the controllable according to an order of magnitude represents the parameters v thus producing in the circulation system at the top of the borehole a succession of pulses of pressure with a short duration corresponding to the energizing pulses, the sequence of pulses of pressure representing the value of the parameter, characterized in that a first means is provided to produce first signals representing a superimposing of the short time pressure pulses and disturbing pressure fluctuations, as well as a peak-forming screen for subtracting the short time pressure pulses from the first signal. 17. A method of taking measurements in a drill hole during drilling using a drill string, comprising a mud passage, forcing drill mud to flow down under pressure, and a constriction causing a pressure drop in which the flow is throttled to produce a pressure drop and consequently generate a high pressure area and a low pressure area with a resulting pressure difference therebetween, a valve being provided between these areas to produce and control a flow of the drilling mud from the high pressure area to the low pressure area, the method comprising the steps of sensing a downhole parameter 30 near the bottom of the column, and controlling the valve to control increasing and decreasing the flow in accordance with a pattern, representing the size of the parameter, characterized in that the degree of each increment of str is set to exceed an appropriate value for producing a drop 800 4 5 99 µl * and a subsequent increase in pressure following the increase in flow rate at the top of the borehole, thereby increasing the rate of each decrease in flow is set to exceed an appropriate value to produce an increase at the top of the borehole and a subsequent decrease in pressure following the decrease in flow rate. 18. Method for taking measurements in a borehole during drilling using a drill string, comprising a mud passage, forcing drilling mud to flow down under pressure, and a constriction causing a pressure drop into which the flow is throttled to produce a pressure drop and consequently generate a high pressure area and a low pressure area with a resulting pressure difference therebetween, a valve being provided between these areas to produce and control a flow of the drilling fluid from the high pressure area to the low pressure area, the method comprising the steps of sensing a downhole parameter near the bottom of the column, and regularly operating the valve to regularly increase and decrease the flow according to a pattern, that represents the size of the parameter, characterized in that the magnitude of each increment also the degree of each decrease in flow is set to exceed an absolute magnitude of an appropriate value thereby producing a shock wave near the bottom of the column for each increase in flow and a shock wave is produced for each decrease in flow , observing successive shock waves produced by the controlled increases and decreases in flow at the surface of the soil. 19. A method of taking measurements in a borehole during drilling using a drill string, comprising a mud passage, forcing drill mud to flow down under pressure, and a constriction causing a pressure drop, in which the flow is throttled to produce a pressure drop and consequently generate a high pressure area 35 and a low pressure area with a resultant pressure difference 800 4 5 99 '' 1 97 between them, a valve being provided between these areas producing and controlling a flow of the drilling fluid from the high pressure area to the low pressure area, the method comprising the steps of sensing a downhole parameter 5 near the bottom of the column, and controlling the valve regularly to control the flow increase and decrease regularly according to a pattern representing the size of the parameter, characterized in that the degree of each increase as well as the extent of each decrease in flow is set to exceed 2 x 10 cm / s in absolute size. 20. Flush circulation system when performing measurements during drilling, generating flush pressure pulses by opening and closing a valve, characterized by a sensor for sensing the value of a parameter in a borehole, further by a first means for measuring holding the valve in an open or closed condition within relatively long periods of time, and by a second means which is responsive to the valve for regularly opening the valve within a relatively short period of time and closing the valve within a relatively short period of time thus producing strong pressure pulses in an order representing the value of the parameter. System according to claim 20, characterized in that the degree K of each opening of the valve, as well as the degree K of each closing 2 (v) of the valve, exceeds the value of 100 cm / s, where K = ST, O 3, 25. is the area of the valve opening in the fully open position, expressed in cm, and T is the time of opening or closing the valve, expressed in sec. System according to claim 20, characterized in that the first means is designed for maintaining the stability of the valve in an open or closed condition. System according to claim 22, characterized in that the valve is an electrically controllable valve, the second means being a means for generating an electric current and producing short current pulses for opening and closing the valve. System according to claim 20, characterized in that the time of opening the valve is sufficiently short to produce a decrease and subsequent increase in pressure at the 800 4 5 99 4 1 'top of the borehole. on opening the valve, the time of closing the valve being short enough to produce an increase at the top of the borehole and subsequent reduction in pressure following valve closure. 25. System according to claim 20, characterized in that the time of opening the valve or the time of closing the valve is sufficiently short for producing a hydraulic shock wave in the rinse circulation system following opening of the valve. the valve, and a hydraulic shock wave following the closing of the valve. 26. System according to claim 21, characterized in that the time of opening the valve is short enough to produce a decrease at the top of the borehole and a subsequent increase in pressure following the opening of the valve wherein the time of closing the valve is sufficiently short to produce an increase at the top of the borehole and subsequent decrease in pressure following the closing of the valve. 27. System according to claim 21, characterized in that the time of opening the valve or the time of closing the valve is short enough to produce a hydraulic shock wave in the mud circulation system following the opening of the valve , and a hydraulic shock wave following the closing of the valve. 28. System according to claim 20, characterized in that the speed of opening the valve as well as the speed of closing the valve is set to produce an increase or a decrease in the flushing circulation system. - 5 2 went from the purge flow, which in absolute size exceeds 2 x 10 cm / s. System according to claim 20, characterized in that the (v) / relatively short duration T = 20 ms. ct A method according to claim 20, characterized in that the 800 4 5 99 (v) ✓ relatively short duration T = 5 = 5 ms. cl System according to claim 20, characterized in that the (v) y relatively long duration = 0.25 s. System according to claim 20, characterized in that the (v) y 5 has a relatively long duration - 0.1 s. System according to claim 20, characterized in that the total time of actuation of the valve T - 270 ms. 34. System according to claim 20, characterized in that the total duration of actuation of the valve = 110 ms. 35. System for taking measurements in a borehole during drilling using a drill string, comprising a mud passage, forcing drilling mud to flow down under pressure, and a constriction causing a pressure drop in which the flow is throttled for producing a pressure drop and consequently generating a high pressure area and a low pressure area with a resultant pressure difference therebetween, a valve arranged between these areas for producing and controlling a flow of the drilling fluid from the high pressure area to the low pressure area, first means for generating a force to open the valve, means for generating a force for holding the valve in the open position, second means for generating a force for closing the valve, means for generating a force for holding the valve in the closed position valve, and means for sensing a downhole parameter near the bottom of the column and regularly operating the valve to regularly increase and decrease flow according to a pattern representing the size of the parameter, characterized by applying means for applying a force in the closing direction of the valve to thereby push the valve towards the closed position despite failure of the second means. 36. System for performing measurements in a borehole during drilling using a drill string, comprising a mud passage, forcing drill mud to flow down under pressure, and a constriction, which causes a pressure drop of 800 4 5 99 t X J) in which the flow is throttled to produce a pressure drop and consequently generate a high pressure area and a low pressure area with a resultant pressure difference therebetween, with a valve arranged between the areas for producing and controlling a flow of the drilling mud from the high pressure region to the low pressure region, and means for sensing a downhole parameter near the bottom of the column, characterized by means for generating an order of electrical signals at an interval, representing the magnitude of the parameter, and actuating the valve according to these signals. 37. System for performing measurements in a borehole during drilling using a drill string, comprising a mud passage, forcing drilling mud to flow down under pressure, and a constriction causing a pressure drop into which the flow is throttled to produce a pressure drop and consequently generate a high pressure area and a low pressure area with a resultant pressure difference therebetween, with a valve arranged between the areas to produce and control a flow of the drilling fluid from the high pressure area to the low pressure area, and means for sensing a number of downhole parameters near the bottom of the column, characterized by means for generating an order of electrical signals at intervals, each representing the magnitude of a parameters, and operating the valve according to these signals. 38. Distance measurement system using a series of discrete pulses, appropriately encoded for transferring data from a transmitting station to a receiving station, characterized by translating each individual pulse into a group of three component pulses at the transmitting station at mutually unequal time distances, further expressing the time distances of the component pulses in each group as three different numbers, transmitting the groups to the receiving station, corresponding to the individual pulses, and transmitting them to the receiving station in 800 4 5 99 1 sensing groups of pulses, corresponding to each of the transferred groups, each comprising component pulses at appropriate time intervals, expressing the time distances of the component pulses in the sensed groups as numbers, and comparing the numbers, corresponding to the sensed groups, with the numbers corresponding to the transferred groups to thereby improve the operation of the distance measuring system. 39. A method of performing measurements while drilling a well in the ground, characterized by pumping drilling fluid through a drill string with a pump producing pressure fluctuations in the drilling mud, further detecting a near the bottom of the column downhole parameter and generating signals representing the magnitude of this parameter, producing pressure change pulses in the drilling mud according to a program having a predetermined relationship with the signals, which pressure change pulses are superimposed on the pressure fluctuations, on the surface of producing the ground of first electrical signals, representing the superimposed pressure fluctuations and pressure change pulses, and comprising a signal carrying useful information, and various interfering signals containing a component of constant strength of the flushing pressure caused by the pump, further a varied The component, produced by the return movement of parts of the pump, and random noise, applying the first signal 25 to the input of an appropriate frequency selective screen to remove the component of constant strength from the first signal and feeding it to the output of the screen producing the second signal containing the signal carrying the useful information, further the alternating component and the random noise, applying the second signal to a delay element to produce at the output of the delay element a third signal, equal to the second signal, but delayed by a time equal to one time duration of the alternating component, applying the second and third signals to a subtractor for extracting the I 1 'I remove third signal from the alternating component and produce a fourth signal at the output of the subtractor t contains the information carrying signal and the random noise, applying the fourth signal to an analog-to-5 digital converter to obtain a fifth signal, which is the digital form of the fourth signal, the fifth signal as an input on a modified screen, provided with a memory operation with control means therefor, comprising computer means adapted to receive data from a storage and recall element, produce and store in the storage and recall element a " noiseless signal ", which is obtained by operating the pump when the drilling operations as well as other sources of interference are stopped, and represents a portion of the signal carrying information produced by a single pressure change pulse, and output it from obtain the matched screen of a sixth signal predominantly the information carrying signal, the random The noise has essentially been eliminated. 40. System for performing measurements in a well drilled in the ground, characterized by a drill string suspended in the borehole, further by a mud pump connected to the top end of the column for circulating drilling mud therethrough, by a flow restrictor, which is located near the bottom of the column and causes a pressure drop and as a result generates a high pressure area and a low pressure area with a resultant pressure difference therebetween, by sensing means near the bottom of the column to generate electrical signals, representing the magnitude of a downhole parameter, by ramming means for producing pressure pulse fluctuations in the drilling fluid in response to the electrical signals, and by a particular transition piece of relatively short length included in the drill string, which transition piece housing which contains the ram means, which housing includes means for downwardly suspending a tubular member containing the sensing means, as well as instrumentation means 800 4 5 99 <4, 103 and power source means, said tubular member having an outer diameter sized to permit mounting in a conventional heavy-duty rod without noticeably affecting the usual flushing flow. 41. System as claimed in claim 40, characterized in that the tubular part is provided with center means for preventing lateral movement of the tubular part relative to the heavy bar. 42. System for performing measurements in a well, which is drilled in the ground, characterized by a drilling column suspended in the borehole, by a mud pump connected to the upper end of the column for circulating drilling mud through it, by a flow restrictor, which is located near the bottom of the column and causes a pressure drop and, as a result, generates a high pressure area and a low pressure area with a resultant pressure difference therebetween, through an electrically operated valve located between the areas and can periodically allow and freeze the purge flow between these areas, by means for applying and maintaining a predominant magnitude of a predetermined magnitude in the "open" direction when the valve is within the range of substantially open to fully open, by means for exerting and maintaining a predominant force of a predetermined magnitude in the "s shutter direction when the valve is within the range of substantially closed to fully closed, by probe means near the bottom of the column for generating electrical signals representing the magnitude of a downhole parameter, by electrical means for operating the valve responsive to the electrical signals, the electrically operable valve 30 including an "open" solenoid winding and a "closing" sole-winding, the electrical means for actuating the valve including means for applying the " open "or the" close "solenoid winding applying an operating voltage, by means for obtaining a control pulse from the occurrence of a temporary reduction in the current drawn by the affected 800 45 99% solenoid winding and immediately following completion of actuation of the valve, and by means responsive to the application of the control pulse for the off switching the supply of energy to the relevant solenoid winding. 43. Flush circulation system when performing measurements during drilling, with flush pressure pulses generated by the return actuation of a valve, which system includes a sensor for sensing a value of a parameter in a borehole, and means that address the sensor. for providing an electric current for operating the valve, characterized by means for controlling the current by addressing the movement of the valve resulting from the operation. 44. System for performing measurements in a well being drilled in the ground, characterized by a drill string suspended in the borehole, further by a mud pump connected to the top end of the string for circulating through it drilling mud, by a flow constriction fluid, which is located near the bottom of the column and causes a pressure drop and as a result generates a high pressure area and a low pressure area 20 with a resulting pressure difference therebetween, by an electrically operated valve, arranged between these areas and configured to sequentially allow or stop a flush flow between the areas by means for applying and maintaining a predominant magnitude in the "open" direction when the valve is within the range of substantially open to fully open, by means of applying and maintaining a dominant force with a predetermined size in the "close" direction when the valve is in the range from substantially closed to fully closed, by hydraulically actuable means movable in response to each switching on of the rinse pump to apply a temporary mechanical force to the valve for closing it, by sensing means near the bottom of the column for generating electrical signals representing the magnitude of a downhole parameter, and by electrical means for actuating 800 4 5 99 '*'. the valve in response to the electrical signals. 45. System according to claim 44, characterized in that the hydraulically actuable means are constituted by a first cylinder, comprising a free piston, which on its outer surface is exposed to drilling mud pressure and is under spring tension to a rest position when it is only under static drilling mud pressure when the mud pumps are not running, and is rapidly movable inwardly against the spring force to a second position, is indicative of an increase in drilling mud pressure as a result of turning on the mud pumps to remain in this second position until the mud pumps are stopped , at which time the free piston is returned by the spring force to the rest position, by a second cylinder, which contains a second piston, which on its outer surface is exposed to the free flow of hydraulic fluid from the first cylinder and usually by spring force to a rest position is pressed but forced to move in n A second position in response to a rapid inward movement of the free piston, by first flow-opening means in the second piston, which enable its return to resume before its resilience to its rest position after the free piston has reached its second position, by second flow through means in communication from the inward end portion of the second cylinder with a volume controllable hydraulic fluid source, which is maintained at the annulus flushing pressure, and by mechanical means, connected to the second piston to apply the temporary mechanical force to the closing valve thereof when the second piston moves from its rest position to its second position. 46. System for performing measurements in a well being drilled in the ground, characterized by a drill string suspended in the borehole, by a mud pump connected to the top end of the column for circulating drilling mud through it, by a flow constriction means which is located near the bottom of the column and causes a pressure drop and as a result generates a high pressure area and a low pressure area 800 45 99. ··, <a 'with a resulting differential pressure therebetween, by an electrically actuated valve, disposed between these regions and configured to sequentially enable and shutdown the purge flow between the regions, by means for applying and maintaining a predominant force of a predetermined size in the "open" direction when the valve is in the region of substantially open to fully open, by means for applying and maintaining a predominant magnitude in the "close" direction when the valve is located in the range from substantially closed to fully closed, by probe means near the bottom of the column for generating electrical signals representing the size of a downhole parameter, by electrical means for actuating the valve in response to the electrical signals, which electrically operated valve has an "open" solenoid coil ng and has a "close" sole-no winding, by means for generating a first pulse responsive to energizing the "open" solenoid winding, by means for generating a second pulse responsive to energizing the "close" solenoid winding, 20 by means for delaying the first pulse so that it coincides with the second pulse in time, by means for applying the delayed first pulse to the inputs of a coincident or OR gate member and by switching means acting in response to an output from the OR gate to interrupt the supply of energy to the "open" solenoid winding so that the valve is not operated to the open position when an electrical fault operation has occurred as evidenced by the absence of coinciding pulses at the inputs to the OR gate. 30 System according to claim 46, characterized in that the switching means are also effective for interrupting the supply of energy to the "closing" solenoid winding. 48. System as claimed in claim 46 or 47, characterized in that an electronic counter is arranged between the output of the OR gate member and the switching means, so that the switching means 800 45 99 * * * 4 * only operate when a predetermined number of consecutive electrical faults has occurred. 49. Flush circulation system when performing measurements during drilling, generating flush pressure pulses by opening and closing a tilt, characterized by a probe for measuring the value of a parameter in a borehole, further by solenoid means for operating the valve, by an adjustable second means, comprising capacitor means, an energy source for generating an electric current for charging the capacitor means and resistive means disposed between the source and the capacitor means, which resistive means are designed to maintain a substantially constant value of the current during the charging of the capacitor means, by a third means, which is responsive to the sensor for controlling the second means for effecting controlled discharges of the capacitor means and applying current pulses , which are the result of these discharges, at the first mid parts for regularly operating the valve to thereby produce pressure pulses in an order representing the value of the parameter. System according to claim 21, characterized in that the first means is adapted to maintain the stability of the valve in an open or closed condition. 800 4 5 99