DK157213B - PROCEDURE AND APPARATUS FOR TRANSFER OF MEASUREMENT VALUES FROM A BOREHOLE TO THE EARTH SURFACE - Google Patents

Description

DK 157213B

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The present invention relates to a method for transmitting borehole measurement values of the kind specified in the preamble of claim 1.

It has long been the practice of monitoring boreholes, ie. sensing various underground conditions in a borehole and transmitting the acquired data to the surface. In the known monitoring operations, as performed by service companies, methods of wiring or cable connections are used. To perform the measurement, the bore is stopped and the drilling equipment is removed from the bore. However, it is expensive to stop drilling operations for measurement. The advantage of being able to measure or monitor during the drilling itself is immediately obvious, but so far the lack of an acceptable distance measurement method has been a serious obstacle to the satisfactory exercise of such a process.

Various distance measurement methods have been proposed for use in drilling measurement. For example, it has been proposed to electrically transmit the recorded data to the surface. Such methods have so far proved impractical because it is necessary to provide the drill pipe with a particularly insulated conduit and means for forming appropriate connections for the conductor at the joints of the drill pipe. André's proposed method is to transmit acoustic signals through the drill pipe.

Examples of such remote sensing systems are described in the descriptions of ü.S.A. Patents Nos. 3 015 801 and 3 205 477. In these systems, an acoustic signal is introduced into the drill pipe and the signal is frequency modulated in accordance with an underground condition found. Frequency shift pulse is used to 2

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transmit the recorded data in digital form. Other methods of remote measurement proposed for use during drilling operations use the borehole fluid as the transmission medium as described in U.S. Patent No. 3,309,656. In the method described herein, a signal with acoustic waves is generated. in the drilling fluid while circulating through the borehole. This signal is frequency modulated to transmit the desired information to the surface. At the surface, the acoustic signal is detected and demodulated to provide the desired reading information.

The object of the invention is to provide a method of the kind mentioned above for remotely transmitting data on the conditions in a borehole using a flowing drilling fluid, and at the same time drilling the hole.

This object is achieved by the method being carried out as specified in the characterizing part of claim 1. The encoded signal is received at the station above and is modulated or decoded there to produce readout functions corresponding to the phase conditions and hence the measured conditions or states.

The invention also relates to an apparatus of the kind specified in the preamble of claim 8 for transmitting data through a flowing drilling fluid between separate points during the drilling of a borehole, and according to the invention this property is characterized by the characterizing part of claim 8. design.

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The invention will be further explained by the following description of some embodiments, with reference to the drawing, in which fig. 1 shows schematically, partly in section, a drilling system with equipment according to the invention; FIG. 2 is a section through a transmitting apparatus immersed in a borehole; FIG. 3 is a block diagram of the coding and transmitting equipment of this apparatus; FIG. 4 and 5 show various curves occurring in connection with the one shown in FIG. 3; FIG. 6 is a block diagram of the above-ground receiving equipment, while FIG. 7 and 8 show various curves occurring during operation of this equipment.

In the preferred embodiments described below, an acoustic signal is transmitted through the drilling fluid used in normal drilling operations. In connection with the drilling, at least one state in the drill bit is decomposed and a signal is generated, in most cases an analog signal representing the decomposed state. An analog signal is converted to a digital serial signal. The acoustic signal generated in the drilling fluid is modulated corresponding to the digital signal in that the phase of the acoustic signal during sequential periods corresponding to the digit intervals of the digital signal is correlated with different phase states representing the different digit values of the digital signal. The acoustic signal is received at a station above the ground and demodulated to produce

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providing output signals corresponding to the respective phase states. These output signals can then be fed to appropriate application equipment, such as recording instruments, or data processing systems, such as computers, from which the requested information can be extracted.

In FIG. 1, a drill bit 10 is shown which is guided down through the crust by a rotating shank. In the drilling, a drill bit 12 attached to the lower end of a drill spindle H. is used. The drill spindle is terminated above in a sliding piece 16, which is of polygonal cross-section, and which passes through pivot 18 at the foot of the drill bar. By means of a bushing not shown, torque can be transmitted between the slider 16 and pivot 18. The pivot drill is driven by a motor 20 through an appropriate drive mechanism, such as a chain pull 21 in the usual manner. The drill spindle H is suspended in the drill bar by means of a hook 23 on a waist block 24. This is at a lobe 26 in connection with a fixed block not shown at the top of the drill bar. The slider 16 is connected to the hook through a swivel coupling 28 which allows rotation of the drill spindle in the hook to the hook. Drilling fluid from a hopper 30, usually referred to as mud pit, is fed through a pump 31 through a conduit 32 into the coupling 28 and thence downward through an inner passage in the drill bit to the cutter 12. The drilling fluid then flows outwardly into the borehole through ports in the drill bit and flows up to the surface through the annular space between the drill bit and the borehole walls. At the surface, the sludge is taken out of gaps through a conduit 33 and fed back to the sludge pit 30. The conduit 32 is provided with a vibration damper 34 which acts to suppress unwanted noise in the drilling fluid resulting from pulsations from the pump 31.

The drilling fluid usually took the form of a sludge, ie. a liquid with slurry solid parts. The solid parts act to impart theological properties to the drilling fluid and also to increase its density to such a value as to provide an appropriate bydrostatic pressure attached to the borehole. In some cases, a colloidal liquid may be used, containing little or no accumulated materials. The main component of the drilling fluid can

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either water or oil.

The drill spindle 14 includes near the drill bit 12 a transmitting apparatus 36 containing one or more target transducers for sensing different states of the borehole and an acoustic generator which feeds an acoustic signal into the drilling fluid. The transmitting apparatus 36 will usually be equipped with transducers for measuring a number of different states, such as the weight of the cutter, torque t at the cutter, pressure drop across the cutter, borehole pressure, soil formation pressure, vibration, drilling mud temperature, and the value of natural gammastrâling. The acoustic generator used will be of any suitable type, which will transmit a pressure-bellows signal to the drilling fluid of such amplitude that it can be transmitted to a station above 3 degrees. A particularly suitable generator for use in the practice of the present invention is a rotary valve transmitter of the kind disclosed in the aforementioned patent.

In the case of swelling of the method according to the invention, an acoustic signal is transmitted to the drilling fluid by means of the acoustic generator in the transmitting apparatus 36, which signal is transmitted upwardly through the drilling fluid. Better signal is modulated in dependence on a condition detected by a measurement transducer by varying the phase of the acoustic signal. At the surface, the acoustic signal is extracted from the drilling fluid by means of one or more receiving transducers and converted into an electrical output signal. For example, as shown in FIG. 1, a transistor 38 is mounted on the heaviest part of the rotary coupling 28. The signal from the transducer 38 is rapidly transmitted to receiving apparatus 40 where it is demodulated to produce output signals representing the measured states of the borehole.

Preferably, according to the invention, an m-close pulse code format is used, where m is equal to 2, 4 or 8, in which the acoustic signal produced in the borehole undergoes phase switching to transmit the individual information in a serial digital format. the invention will be applicable to any suitable phase shift technique in which the phase of the acoustic signal is correlated with a number of different phase states corresponding to digit values in a suitable code. Berries can be used for-

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different coding methods. For example, the phase states surviving to transmit information to the acoustic bellows could be the phase state of the signal, namely, the phase angle of the signal relative to a reference bellows or reference curve. Thus, with a binary code (m = 2), the state of phase variability (phase angle equal to zero) can be used for one bit value and one with phase inversion (phase angle equal to 180 °) for the other bit value. For a code with base or radix four (m = 4), the phase states corresponding to the respective digit values can be the phase states at 0 °, 90 ° 9 180 ° and 270 °. Alternatively, a non-return form can be used, at which the phase states corresponding to the different digit values constitute several phase states of the signal relative to the phase state of the signal during a preceding digit range. For example, for a binary coding system, sixteen phases in a digit range - and the following - could denote a digit value of "0", while switching the phase from one digit range to the next could indicate a digit value "1". System, the numerical values can be specified at a constant phase ratio from one digit range to the next for one digit value, a phase change of 120 ° for another digit value and a phase shift of 240 ° for the third digit value. This code relay without return to zero should be preferred for The reliability of decoding, since a bit value is indicated by phase change, the invention will be described below in connection with a binary code of this kind.

The transmitting apparatus 36 is shown in more detail in FIG. 2. It has an inner housing 42 and an outer housing 44 defining an annular space 45 through which the drilling fluid passes. The outer housing has threads at both ends for connection to the drill spindle. The apparatus is as shown in three sections 46, 48 and 50. The first section 46 is connected to an acoustic generator consisting of a toothed stator 52 and a similarly toothed rotary valve 54 operated in relation to to the stator. The rotor is shown in an open position in which a slot 54a in the rotor and a slot 52a in the stator are connected. The rotor 54 is driven through a reduction gear 57 by a drive motor 56. As will be seen from FIG. 2, drilling fluid will pass through the slots in the rotor and stator. As the rotor rotates, driven by the motor, the fluid stream intermittently is interrupted, thereby transmitting the desired acoustic signal to the drilling fluid. The diameter of the rotor 54 is slightly smaller

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than the inner diameter of the housing 44. Therefore, a certain amount of drilling fluid will pass around the rotor and the germline slots in the stator one when the rotor is in a closed position.

On the lower end of the shaft of the motor is mounted a tachometer 58 which serves to produce a signal representing the motor speed and thus the rotational speed of the valve 54. The tachometer signal is used as described later in a feedback circuit to control the frequency and phase of the motor. acoustic signal. The tachometer 58 consists of a coil 59 and a rotor 60 fixed to the motor shaft. By rotating the rotor 60 relative to the coil 59, an alternating voltage is induced therein at a frequency which is proportional to the orbital speed of the motor 56. The signal from the coil 59 is fed to usual, not shown, circuit 10b for pulse forming and frequency division to produce an impulse signal used to control the motor speed.

The middle section 48 is blocked from the other two sections by cross walls 62 and 65 through which electrical wires pass. This section contains the later discussed electronic components associated with the transmitting apparatus, including those for receiving the output signals from the various transducers used to measure or sense different states of the drill housing. The housing 44 is surrounded by a ring 64 which defines an outer space 65 for positioning target transducers.

The lower section 50 contains a generator 68 which provides electrical power to the motor 56. The electric generator 68 is driven by a turbine 70. The turbine 70 is driven by drilling fluid flowing down through the apparatus through the space 45 between the two housings 42 and 44. A more detailed description of the mechanical properties of the one shown in FIG. 2 can be found in the above-mentioned U.S.A. patent specification.

FIG. 3 shows a block diagram of the main parts of the transmitting apparatus 36. This System contains a generator 74 for synchronization words and a number of target transducers D ^, Dg ... D ^ for detecting states as described above and for producing corresponding ones. output signals. The output signals from these transducers, usually analog voltage signals, are fed through a multiplexer 80

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to the encoder 82. The multiplexer acts to feed the analog signals to the encoder 82 in a suitable sequence. In addition, the multiplexer 80 carried a channel S belonging to a synchronization word inserted in the second part of the system from the generator 74. If desired, the multiplexer may be provided with so many channels that more frequent exemplification of one or the other is possible. several of the signals from the trans eme. For example, signal t from transor 1 can be fed to two input channels to the multiplexer so that the size will be transmitted twice during each cycle of the multiplexer.

Encoder 82 is an analog-to-digital converter that will generate a digital word in dependence on each analog signal from the transducers. The output of converter 82 is fed to an encoder 84 through a ten element open circuit 75 and the output of generator 74 is fed to encoder 84 through a ten element open circuit 76. Encoder 84 is a parallel series switch register which acts to convert the parallel signal from circuit 82 and from generator 74 to a serial digital signal which is then fed to a motor control circuit 85. The motor control circuit, multiplexer, converter and encoder are controlled in synchronous fashion. function at a clock circuit 86.

Generator 74 is a component unit which, at the command of clock circuit 86 and counter 87, provides output signals in the form of one or more determined words used to denote the beginning of a block of data words.

Preferably, the system also incorporates a parity generator 88 which acts to add a parity bit to the output of the circuit 84 so that parity check is obtained for each transmitted word. The parity generator produces a parity bit with one state in dependence on an odd number of bits of a particular state in a word, and a parity bit of another state in dependence on an equal number of bits of said state in the word. For example, if odd parity checks are used for bit values on "I", the parity generator 88 will count the number of "1" in the word and output the 11th bit soin "I" if the number of "1" is in the first ten bits is equal, and an "O", if the number of "1" in the first ten bits is odd. Thus, every word transmitted will imply one

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odd number of "1" ones that provide a check for transmission or reception errors.

The motor control unit 85 acts to maintain phase-locking transmission by comparing a feedback signal from the tachometer with the primary clock signal from the clock circuit 86. Furthermore, the control unit 85 acts to effect a phase change of the acoustic signal at each signal "1" from the circuit. 84. In both cases, control voltages are supplied from single-bed 85 to a voltage-controlled unit 90 which delivers power to a two-phase induction motor 56. The motor 56 is as described in connection with FIG. 2 mechanically connected to drive the rotor 54.

The operation of the control circuit 85 and its associated circuits in carrying out the aforementioned functions will be described in connection with the functions of FIG. 4 and 5. The various curves of FIG. 4 and 5 are provided with reference numerals which indicate the points at which they appear in the circuits of FIG. 5. In the following, it is assumed that the rotor 54 is a rotary valve with ten slots of the type described above, operated at an acuity bearing frequency of 25 Hertz, corresponding to an orbital number of 150 rpm. In an embodiment in which the reduction gear 57 bore a turnover example of 25: 1, the motor 56 was driven with a speed bed of 3750 rpm, so that the rotor 54 gave an output of 25 Hz. Further, the circuit 84 was arranged to generate binary words with electric live bits, namely ten bits of information plus one parity bit.

The clock circuit 86 and the counter 87 provide clock signals a, b, c, d and g, fig. 5, to the leg ball multiplexer, transducer, encoder, motor control unit and synchronization generator. In addition, the pulse generator 58a produces a series of signal pulses e which are supplied to the motor controller 85. The pulse frequency of the pulses e is a measure of the bypass bed of the motor 56. The generator 58a incorporates the tachometer 58; 2, and the impulse-forming pulse circuits. The pulse frequency of the primary clock signal d is 50 pulses per second. second. The signal e will also emit a frequency of 50 pulses per second. second when the valve or transmitter 54 is operating at 25 Hz.

The different signals or pulses a, b, c, d, e and g are obtained with pulse frequencies linked in the following manner: 10

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a ** * = s! "Fs O = y- d = e = 2fs g _ fs S - SW 'where fg = acoustic frequency = 25 Hertz B = number of" bits per word = 11 P = periods or cycles per bit = 25 ¥ s number of words per block = 16.

The OmXob speed of motor 56 is determined by the amplitude of the output of the control unit 85. This output is again a function of the sum of four voltages, whose value is determined by the phase relationship between pulses d and e, Y2> a constant voltage constant amplitude set to a value intended to produce an acoustic signal of 25 Hertz, V ^, a constant amplitude DC voltage (a negative bias, i.e., value equal to the positive when pulses d and e is in the counter phase, as well as Y 1, a phase reversing voltage produced to change the orbital speed of the motor 56. to switch the phase of the signal produced by the transmitter 54.

The voltages Y2 and Y ^ are obtained as shown in FIG. 5 from batteries 91 and 93. The voltage is obtained as follows: The signal d from the clock circuit is fed to a bistable multivibrator 92 and to a linear integrator 94. The signal e is also fed to the multivibrator 92 and to a holding circuit 96. The clock signal d acts switching the multivibrator to the indoor state, where it carries a DC constant voltage Vj to the integrator 94. The signal e from the pulse generator 58a acts to return the multivibrator to disconnected position. The output of the multivibrator 92 is thus a train of pulses of constant amplitude and variable duration, the pulse length being proportional to the interval between the pulse d and the pulse e. This pulse train is fed to the integrator 95 which produces a voltage signal whose amplitude is proportional to lasting-

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of the respective impulses applied. The integrator will hold the integral value until it is reset to zero by the next pulse d, upon which it is conditioned to respond to the subsequent pulse from the multivibrator 92. Each final integral value in the integrator is exemplified and maintained by the holding circuit 96 dependence on the pulse e. Thus, from one pulse e to the next, a voltage representing the phase difference between pulses d and e will be established. This voltage, the voltage Yj and the voltages Y2 ° S Ÿj, will quickly become a summing amplifier 98.

The output signal of amplifier 98 is fed to a motor supply circuit 90 to change the frequency of its output signal, and thus the orbital speed of the induction motor 56 is controlled. the DC voltage to the AC voltage at a frequency corresponding to the signal from the oscillator 104, which frequency is determined by the output of the amplifier 98.

As previously described, the motor control circuits will drive the motor 56 and thus the acoustic transmitter 54 with phase locking, so that the clock pulses d are phase shifted 180 ° relative to the pulses e from pulse generator 58a. In this form, the positive voltage T1 from the holding circuit 96 in amplitude is equal to the negative voltage Y1, and the motor speed is determined by the voltage Y2. A change in motor speed will change the phase relationship between pulses d and e and again vary the amplitude of voltage V-j. The change in voltage Y ^ is a deviation signal that will act to steer the system and bring the motor back to its proper speed And selected phase.

Then, the function of the transmitting system must be described in providing phase switching of the acoustic signal. The frequency of the signal a fed to multiplexer 80 from counter 87 is one pulse per second. eleven seconds. By supplying the signal pulse a, the multiplexer proceeds from one channel to the next and transmits a selected analog value to the converter 82. The frequency of the signal b to this circuit is also one pulse per second. eleven seconds. This signal is slightly delayed relative to the signal a for recording

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the advance time of the multiplexer and the turnover time of the transducer. Converter 82 converts the analog value into a ten-bit binary word representing the input analog value. The frequency of signal c supplied to encoder 84 is one pulse per second. customer, and this signal is also phase-shifted relative to signal b to provide a suitable delay. The encoder responds to each pulse transmitted by generating a command signal j, either a "1" or a "0M. The motor controller 85 responds to each" 1 "signal by switching the phase of the acoustic signal and at each" 0 "signal. with continuing the acoustic signal in the same phase.

The bit interval A is a "1n bit. The encoder 84 will therefore respond by producing the pulse jj fed to a generator 100, FIG. 3 generating a square voltage k1. The output of the summing amplifier 98 now grows and operates across the circuit 90 increasing the speed of the motor 56 to advance the phase of the acoustic signal.The motor speed and the corresponding acoustic signal are shown by the curves 1 and iii of Figure 4. As shown, the motor speed bed substantially increases linearly as the voltage of the amplifier 98 increases. k is suddenly slowed down, the motor will decelerate until it returns to normal speed, corresponding to the carrier frequency of 25 hertz. At this point, the signal is approximately 180 ° phase shifted relative to the previous phase state, and the motor control circuit will operate depending on the current. the backing signal from the pulse generator 58 to provide an accurate phase-locked state.

The amplitude of the square bolts k is large in comparison with the defmaximum output of the integrator 94, and this will eliminate the effect of the feedback control obtained by the impulse e so that the motor 56 can run up and change phase. Generator 100 may here be considered as part of the motor control circuit 85, although it is shown outside its line of dashed lines. Although the output of generator 100 was shown and described as a square bolt, it could be of any shape suitable for changing the speed of the motor 56.

When the bit value as shown in interval B is "0", the command signal from encoder 84 will simply be a missing pulse and the acoustic generator will continue to produce an acoustic signal of 13

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the same phase state as in the previous bit interval A. The bit value in the interval C is "1", so the encoder 84 responds to the pulse c to produce pulse j1, is received in the generator 100. An output signal kg is generated, and motor 56 is again accelerated and decelerated as shown to switch the phase of the acoustic signal.

Bet format, according to which the data is arranged for transmission from the transmitting apparatus to the surface for detection, is shown in FIG. 5. Each block begins with a synchronization word, followed by data words No. 1 to No. N. In the embodiment described above, there are fifteen data words: N = 15. In the various data words, examples show that the value of the parity bit * one can be either "0" as in data word # 1 or "1" as in data word # 2, so that each data word will contain an odd number of M1 bits. The figure further shows the impulses a and b at the beginning of each word.

However, the pulse g arrives only once for each block and is used to control the synchronization words and, furthermore, to control the forward-opening aperture circuits for feeding the synchronization word to the encoder 84. The control pulse g is generated by the counter 87 and fed to the generator 74. simultaneously to a generator 77 which can take the form of a monostable multivibrator which will output as an output signal h as well as an aperture signal h 'not shown, which is complementary to signal h. The signal h is fed to the aperture circuit 76 to open it, while signal h1 is applied to aperture circuit 75 to close it. When the opening circuit 76 is open (conductive) and the opening circuit 75 is closed (blocking), the output of the generator 74 is fed directly to the encoder 84, 0 <3 the output of the converter 82 is blocked from the encoder. After a time interval determined corresponding to the length of one word, generator 77 returns to steady state and signal h is changed in negative direction to block opening circuit 76, while complementary signal h 'moving in positive direction , seems to make the opening circuit 75 conductive.

Another feature of the present System is the use of two mutually complementary synchronization words. Bit synchronization words are generated alternately by the synchronization generator 74. In other words, the first synchronization word is used.

ΤΤΛίΛ Λ 4 * λΙα 4 · ηνΊ / »1 ^ 1« »A A λ · Μ Vn« i «t ΜΛ 4ΑΜΜΜΛ Λ Λ * 4“ 1> * AW> T \ I A

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number. The synchronization word is shown in FIG. 5 within block 1 and its Complément is shown at the beginning of block 2.

The baud length for each bit fcan is varied by setting the counter 87j for example. by turning a knob 87a, FIG. 3, for offsetting or reducing the number of periods representing bver bit When the signal-to-noise bit is bent, which may occur during the initial part of the drilling program, the bit length may be one second or less. As the borehole becomes deeper, the signal-to-noise ratio decreases, and it will be desirable to increase the number of periods for each bit or in other words to increase the baud length. A change in the baud length will, of course, necessitate changing the frequencies of the different pulses, such as pulses a, b, c, etc., in accordance with the equations given above.

As previously discussed, the transmitted acoustic signal is received at the surface of a transducer 38 which acts to convert the acoustic signal into one form suitable for demodulation. The transistor 38 may be of any suitable type responsive to the acoustic signal to produce an output signal representing the phase of the acoustic signal. The transducer 58 may, for example, be a piezoelectric crystal which produces an alternating voltage signal at the same frequency as the acoustic signal.

The output signal from transducer 38 is fed to a receiving system which produces, from the output signal, a control signal that remains in synchronism with the one phase state of the received acoustic signal. The received signal is demodulated, compared to the control signal to detect phase changes in the received signal, and corresponding readout functions are produced corresponding to different phase differences between the received signal and the control signal.

Eig. 6 shows a block diagram of a preferred embodiment of the receiving system used in the present invention. The signals appearing in connection with its operation are shown in FIG. 7 and 8 are labeled with the corresponding points in FIG. 6, where the various signals occur. For the sake of simplicity this system assumes the same parameter conditions as

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was provided by the above described SendSystem. Thus, the carrier frequency of the received acoustic signal is 25 Hertz, and a signal form with binary signals without return to zero is used. However, it is to be understood that the receiver can be used with other suitable modes of transmission as well.

The received signal is fed from transducer 38 to a low noise amplifier 110 to prevent noise distortion from being introduced into the signal.

The amplified signal from amplifier 110 is fed to a filter 112 whose passband is the reciprocal value of the baud length used to attenuate noise outside the frequency band used, when the baud length is one second, the passband will be a period, for example, between 24.5 and 25.5 hertz. The good filter 112 passes the signal through an ACG amplifier 114 to eliminate larger amplitude fluctuations in the signal and to produce a signal of relatively uniform amplitude p.

The signal p from the amplifier 114 is fed both to a synchronous phase detector 116 and to a phase locking circuit 117, in which a control signal z is derived to the detector 116 as described below. The base detector 116 acts to compare the phase of the signal p with the control signal z to produce a signal r representing the phase relationship between the two signals. For example, the base detector 116 may be a switching type unit in which the control signal z will act to switch the signal p between positive and negative inputs to the detector. During the positive directional fluctuations of the control signal, the output signal r of the phase detector is switched to polarity relative to the signal p. During negative fluctuations of the control signal z, the output signal of the detector 116 has the same polarity as the signal p. phase as indicated in FIG. 7 at sections of the portion designated phase I, the output signal r from detector 116 will be positive. When the signal p and the control signal z are mutually in phase as shown in the part designated phase II, the output of the unit 116 will be a signal with negative balloon bulbs as indicated by section r2.

In the phase-locking circuit 117, the control signal z for the detector 116 is input to a voltage controlled oscillator 120. This oscillator is initially adjusted by supplying appropriate

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1 f voltage values for generating pulses t at a pulse frequency four times the pulse of the received acoustic signal p. In the embodiment described, the pulses t have a pulse frequency of 100 hertz.

Feedback control of the oscillator 120 is derived from the signal p. This signal is fed to a frequency multiplier in which the frequency is doubled to produce a signal s of 50 hertz. In doubling the frequency, the phase state of the signal s will remain the same regardless of the phase switching that might occur. signal p.

The signal t from oscillator 120 is fed to a square wave generator 121, which may be a bi-stable multivibrator, to produce a pulse train of the same frequency as signal s. Signals u and s are fed to a synchronous phase detector 126 operating in the same manner as the above described phase detector 116. The exit signal from detector 126 is a bolt train v, whose average DC component will be zero when circuit 117 is in phase lock. During these conditions, the pulses will be phase shifted 90 ° relative to the signal s.

The signal v is used to control the frequency and phase of the oscillator 120. The signal is fed over an amplifier 150 and a filter 152 to the oscillator. the cross amplifier 150 has a fixed gain which is set according to the parameters of the circuit 117 to provide the current control from the signal v. 3, the filter 152 has a long time constant, so that the substantially the voltage component of the signal v, the deviation signal w is fed to the oscillator 120. This feedback arrangement will ensure that the output signal u from the generator 121 will be held in a predetermined phase position relative to the signal s, i.e. that it will be 90 ° phase shifted relative to the signal s.

The operation of the "feedback control" is shown in Fig. 7 by an initial deviation and a change in the phase of the signal p. If there is a phase difference different from 90 ° between signals s and u, a negative component will be produced as shown by curve w. For the sake of clarity, the deviation is greatly exaggerated in the figure. When the negative signal w is fed to the oscillator 120,

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it will correct the output signal so that the signals s and u are brought into the desired phase relation * When the generator in the drill bit t changes phase, a deviation signal is first developed which goes first in the negative direction and then in the positive direction * Around at the time when the phase change for signal p is completed, the signals will again and again bounce the decreased phase difference.

The pulse train is transmitted to a pulse generator 155 9 that will only respond to the leading edge of the pulses u to produce pulses x. The frequency of the pulses x is twice the frequency of the signal p, in this case 50 Hz.

Since the purpose of the circuit is to produce signals z, if the phase state will be constant and correspond to one of the phase states of the signal p, it will be necessary to change the phase for

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the impulses x. The actual input phase change will be such that the switched pulse will appear at a time corresponding to the zero throughput of the signal p. The switching is applied by a delay circuit 156, if the output signal is a series of pulses γ.

The pulses γ are rapidly transformed into a square bulb generator 158, a bi-stable multivibrator, to generate square pulses z. The impulse train z is advanced to the phase detector 116, and in the manner described above, the summation signal r, the detected output signal, is generated, in which one phase with a state in the signal p will be represented by positively directed signals r, and one phase of another state in signal p will be represented by negatively directed signals r.

As mentioned, the 150 amp earphone has fixed gain. In order to ensure the proper functioning of the circuit 117, the amplitude of the signal p fed to the circuit is essentially biased constantly »The amplitude adjustment is provided by the amplifier 114 and an associated circuit for automatic gain control. The detected signals r are whole-wave rectified in a rectifier 140 and are filtered in a low-pass filter 142 to produce a representation of the amplitude of the signal p. This function, which can be monitored on a measuring instrument 144, is fed to a differential amplifier 146. which compares the value of the function with the value of a neferennesnîpnd-injo · ¥ from a s-nswn rH n o-elril Λ e 1Æ. Change in *

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18 the value of the function about the value of is applied to the amplifier 114 to control its gain 0g to keep the amplitude of the signal p substantially constant. X> an amplitude level at which the signal p is maintained is determined by setting the voltage by means of a setting button 149 at the voltage source 148.

At this stage, usable data is generated in the form of signals r. This signal should only be decoded using the principle that a change in phase (polarity) is a bit "1" and no change in phase ( polarity) is a bit "0". The signal r may be recorded in visible form on a recording instrument not shown and decoded by an operating number. However, in automatic mode, automatic decoding is used, in particular for a format that can be read mechanically. for this purpose, a bit synchronization system is used.

As a first step for bit detection, the signal z with a frequency f (the frequency of the signal p) is fed to a sub-circuit 150 which produces an impulse train aa with an impulse frequency equal to the bit frequency. In the present system, the bit period is one second and the length of the transverse pulse aa is a balv period or 1/2 second. The onset of the pulses must coincide with the beginning of each bit period. Since the pulses z are independent of the bit period and its beginning, it is serged to adjust the initiation of the pulses aa to coincide with the beginning of each bit period. This adaptation is provided by an adjustable delay circuit 152, the output of which is an impulse train bb which, as shown in FIG. 8 is phase-shifted 180 ° with respect to the pulses aa and whose beginnings coincide with the beginning of bit periods, shown as the signal r.

When the pulses bb are properly matched, bit detection can be performed by starting the integration of the signal r at a time corresponding to the beginning of each pulse bb and terminating the integration at a time corresponding to the end of each bit period. The exemplary value of each integration will indicate the value of the bit signal r, and thus each bit will be correctly identified.

To perform the integration detection, the impulse train bb is used to trigger a pulse generator 154 * which responds to the positive

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going part of each pulse b to produce a train of short-lived pulses ce. The pulses cc are rapidly transformed into an integrator 156, also referred to as an in-phase integrator, which is reset depending on the trailing edge of each pulse cc * A holding circuit 158 responds to the leading edge of each pulse cc to sample the output of the integrator 156 This output signal is the integrated value σc of the signal r fed to the input of the integrator * The output of the holding circuit 158 is shown by the fearven ff.

A bit "1W is represented at each zero throughput of the curve ff. If, as lying, a zero throughput detector is used to generate the bits" 1 "and" O ", then the curve ff is modified to have uniform maximum values and minimum values, since the signal ff then becomes a bit polarity detector 160, a saturation amplifier driven to saturation for each positive or negative value of the signal ffe The result is the signal shown by the curve gg a bit value generator 162, a zero-through detector whose output signal is an impulse train, etc. consisting of! 1 "is represented by pulses and" 0 "is represented by missing pulses."

The impulse train etc. is fed to a utilization apparatus 165 which could be a recording instrument or a digital computer, either with the wired program or of the ordinary programmable type. In both cases it is desirable to provide information when the information in the impulse train etc. is to be read, namely information on the times when to look for a bit "O" or a bit "1", This information is provided by pulses from a readout generator 164. This generator is a device to which the pulse train cc is fed. predetermined time periods so that they occur during the expected times of the bit pulses, etc., and the result is the pulse train nn.

All the necessary information is provided by the pulse trains mm and nn for decoding the data and specifying measurement values for the borehole condition. Using a programmable data machine, the state-of-the-art software for identifying the synchronization words may be provided to indicate the start of each 20

DK 157213 B

The delay to be applied to the pulses aa is such that the integrator 156 will integrate signals representing the In bit access and thus avoiding duplication of the preceding or subsequent bit information is determined by an arrangement using an out of phase integrator 170. At its input, the integrator 170 receives the bit information as represented by the signal r and has an output signal when the system is properly set, as represented by the initial portion of the bellows train hh. The integrator 170 begins its function at a time approximately 90 ° later than the integrator 156. The integrator 170 is set to integrate over a period of in bit length.

Therefore, the output of the leg at the end of an integration period must be zero. The delay unit 152 is therefore set until the output of the integrator 170 is zero at the end of each integration period. The adjustment is made by passing the pulses bb to the input of a pulse generator 172 which responds to the negatively directed impact or the trailing edge of the pulses bb to produce a series of short duration pulses dd. The integrator 170 is reset at the rear portion or the negative portion of each pulse dd and begins the integration of the input signal r to produce the bellows train hh. The pavement train hh, together with the bit information, pavilion train gg, passes to a synchronous phase detector 174 which operates in the same manner as the phase detectors 116 and 126 described above, and which produces an output signal in the form of a pavement train ii. The belay train ii is guided through a normally conductive opening circuit 176 to a holding circuit 178 which responds to the leading edge of the pulses dd by momentarily sampling and then holding the signal ii at a time corresponding to the end of the integration period in the integrator 170. When the system is correctly set, the holding circuit 178 will read each time the bellows train ii is exemplified and its output signal can be represented as shown by signal 11. If the system does not work or track properly, at the output of the holding circuit 178 an error signal will be generated which will be detected by the measuring instrument 180. Bette instrument will show the magnitude and direction of an error that can be corrected by setting the delay unit 152 by means of a setting button 152a.

In examining the curve r, fig. 8, it will be seen that there are conditions under which the output signal hh from integrator 170 will

DK 157213 B

be different from zero at the time it is to be exemplified, even if the system is set correctly, These conditions exist when sending and receiving nOw bits. This condition is shown by the curve hh assuming full negative value as soon as one or a number of such occurs. An operator who makes the settings while observing the measuring instrument 180 will find that large fluctuations of the instrument must be ignored as they simply represents the presence of an "O" bit. In practice, the maximum error expected or readable on the instrument 180 will be approximately half of the full integral value of a received bit. Any reading on the instrument 180 with a value less than half of the integral value of a bit is treated as an error, while outputs more than half the value can be ignored, * 3

The logic mentioned above in interpreting the reading of the instrument 180 can be performed with computer components, whereby the settings can be made automatically. This is implemented by means of a discriminator 182 which at its one input receives the reference voltage? 0 with an amplitude equal to half of the integrated bit value, the Belge train ii is fed to the other input to the discriminator. As soon as the amplitude of the signal ii exceeds the half-value, the discriminator will output a control pulse which will block the opening circuit 176, the end result will be the belge train kk, where a blocking of the opening circuit is represented by portions of the belay train kk is delimited by small arrows where the signal k k has been reduced to zero * When the discriminator operates as described above, the holding circuit 178 will include a zero signal at each sample interval unless the system is in fact out of setting. It can be assumed that the impulse train dd has been delayed for a period of time σ. In this case, the function of the holding circuit 178 will be delayed and it will perceive an output signal from the integrator. This output signal, denoted by curve 11, denoted 190, will be fed over a low-pass filter 192 to the delay unit 152 for changing impedances therein to effect the later correction of the delay introduced in the pulse train aa, if the error is in the other right. as shown by one of the pulses d being advanced for a period of time -a, the holding circuit 178 will again receive an output signal from the integrator 170, this output signal shown as a negative rectifier.

22 DK 157213 B

curve 194, will also effect the corrections in filter unit 152 over filter 192,

The above description of automatic feedback for initiating and maintaining bit phase synchronization is based on an analog feedback signal which is in amplitude proportional to the phase error σ, and so by its sign shows the direction of the phase error. Other feedback mechanisms may be used.

For example, a purely digital system with the insertion of extra pulses or the omission of pulses at the input of the circuit 150 will work to shift the phase of the bit integrators. In this embodiment, the delay circuit 152 is used for the initial setting of the circuits to give exact phase conditions.

Claims (10)

A method of transmitting measured values therefrom to the ground surface during drilling a well using a flowing drilling fluid and a generator having a movable member which, when operated at a constant speed, produces a continuous acoustic signal in the liquid of constant phase and at a frequency proportional to the rate of movement of the member, propellants for said member and a transducer arranged in the borehole, characterized by a short-term change in the rate of movement of said member depending upon the output of the transducer, and then the speed is returned to the constant value, whereby the phase of the acoustic signal is changed from one phase state to another phase state. Method according to claim 1, characterized in that the acoustic signal is encoded in m-near coded baud, where m is any integer greater than 1, said baud signals being output at a predetermined rate which is varied so that the time period for the generation of the acoustic signal representing each sound is varied. Method according to claim 2, characterized in that m is equal to 2.4 or 8. Method according to any one of the preceding claims, characterized in that the movable means for generating the acoustic signal comprises a rotary valve for interrupting the liquid flow, means for generating impulses at a predetermined repetition free number for controlling the circuit number of said means for producing a signal representing the rotation of the valve, means for comparing said impulse and said signal for generating a deviation signal when said valve operates at a phase different from that of said valve. pre-selected phase, as well as means for adjusting the rotation of said valve to restore said preselected phase and return said deviation signal to zero, depending on the deviation signal. Method according to any one of the preceding claims, characterized in that a number of borehole transducers are used for sensing conditions therein and for generating analogue signals representing these states, cyclic means for multiplexing the signals, an analog-to-digital converter for translating said analog signals into digital words represented by two states "0" and "1", an encoder which serves to produce, depending on said digital words, an output signal when only one of the the two states occur, means for introducing a synchronization signal into said System at the beginning of each period of said means for multiplexing, wherein said means for briefly changing the turnover number of said body responds to each output signal of said codes for switching or reversing the phase of said acoustic signal. Method according to claim 5, characterized in that the means for introducing the synchronization signal alternatively introduce two synchronization signals, one of which is complementary to the other. DK 157213 B Method according to any one of the preceding claims, characterized in that said states are generated at a selected tempo, whereby means are provided for varying this tempo for varying the period of time in which said acoustic signal representing each state, being generated. 8. Apparatus for transmitting data by means of a flowing drilling fluid between separate points during the drilling of a borehole by means of the method according to claims 1-7, which comprises an acoustic generator for generating a continuous wave signal and having a moving means which, when driven at a constant speed, produces a continuous wave phase with a constant phase and a frequency proportional to the speed of the moving element, as well as a signal source, characterized in that it additionally comprises means for temporarily changing the velocity of said organ depending on said output of said signal source and then restoring said constant velocity such that the phase of the acoustic signal changes from one phase state to another phase state. Apparatus according to claim 8, characterized in that the signal source comprises a plurality of transducers for producing analog signals representing sensed states in the borehole, the apparatus further comprising means for converting said analog signals to digital serial signals, multiplexing means for supplying said signals in series from said transducers to said transducers, as well as means for the short-term change of said velocity of said organ and thereafter to restore said constant velocity so that the phase of the acoustic signal changes according to the digital signals mentioned in DK 157213 B. Apparatus according to claim 9, characterized in that it comprises means for controlling the operation of said generator, which comprises clock means for producing a primary time function representing said selected frequency, pulse generating means associated with said generator and service. for generating a secondary time function representing the actual operating frequency of the generator, means for comparing said primary and secondary time functions, and means for adjusting the working frequency of said generator according to the deviation between said secondary time function and said primary time function. Apparatus according to claim 9 or 10, characterized in that it is constructed and arranged to be capable of operating in conjunction with a grounded transducer which is acoustically coupled to said drilling fluid to produce an output signal of the same frequency as the frequency in said acoustic output signal, an oscillator for generating a reference frequency, means containing a phase detector for adapting said oscillator to establish a fixed phase relationship between said phase of said reference frequency and said phase acoustic output, means for depending on each of said transducers in said transmitting apparatus, supplying said driving motor with a series of control pulses of such magnitude and duration as to produce transient changes in said orbital speed such that the phase of the acoustic signal is changed by a predetermined size with respect to the phase of the reference frequency, as well as means containing a phase detector for in-dependence to produce output pulses corresponding to the said control pulses, due to said phase changes due to the transient speed changes.