US3541852A

US3541852A - Electronic system for monitoring drilling conditions relating to oil and gas wells

Info

Publication number: US3541852A
Application number: US780041A
Authority: US
Inventors: James H Brown; William S Young; William M Deason
Original assignee: Dresser Industries Inc
Current assignee: Dresser Industries Inc
Priority date: 1968-11-29
Filing date: 1968-11-29
Publication date: 1970-11-24
Anticipated expiration: 1987-11-24
Also published as: CA923333A; DE1943222A1

Description

3,541,852 TIoNs NOV. 24, 1970 J, H, BROWN ETAL ELECTRONIC lSYSTEM FOR MONITORING DRILLING CONDI 'RELATING To OIL AND GAS WELLS Filed Nov. 29, 1968 5 Sheets-Sheet l wmv IIIIIIIIIIIIIIMIIIII'L Nov. 24, 1970 H BROWN ET AL 3,541,852 ELECTRONIC SYSTEM FOR MONITORING DRILLING CONDITIONS RELATING TO OIL AND GAS WELLS Filed Nov. 29, 1968 5 Sheets-Sheet z AMPLIFIER ONE SHOT 45' 47 37 gLLgR GATE RECORDER 48 W 49 r55 INTERLOCK Ccg'flTER DRIVER an- J V COUNTER 50 Iozl 5I COUNTER IO: I

/52 FIG 2 |ACCUII/IULATOR l 53 DIODE MATRIX BUFFER 54 l READOUT l INvENToRs WILLIAM M. i DEASON JAMES H. BROWN WI LLIAM S. YOUNG ATTORNEY NOV. 24, 1970 1 H, BROWN ET AL 3,541,852

ELECTRONIC SYSTEM FOR MONITORING DRILLING CONDITIONS RELATING TO OIL AND GAS WELLS Filed NOV. 29, 1968 5 Sheets-Sheet 3 +D.c. VOLTAGE JAMES H. BROWN WILLIAM S. YOUNG LLDJJIQQL F- AT ORNEY J. H. BROWN ET AL Nov. 24, 1970 ELECTRONIC SYSTEM FOR MONITORING DRILLING CONDITIONS RELATING TO OIL AND GAS WELLS 5 Sheets-Sheet 4 Filed NOV. 29, 1968 dvd+? INVENTORS WILLIAM M. DEASON JAMES H. BROWN WILLIAM S. YOUNG ATTOR EY I pm.

NOV. 24, 1.970 J, H, BROWN ETAL 3,541,852

ELECTRONIC SYSTEM FOR MONITORING DRILLING CONDITIONS RELATING To OIL AND GAS WELLS 5 Sheets-Sheet 5 Filed Nov. 29, 1968 FIG. 6

INVENTORS WILLIAM M. DEASON JAMES H- BROWN WILLIAM SfYOUNG 0.2m OWN ATTORNEY United States Patent O 3,541,852 ELECTRONIC SYSTEM FOR MONITORING DRILLING CONDITIONS RELATING TO OIL AND GAS WELLS .lames H. Brown, William S. Young, and William M. Deason, Houston, Tex., assignors to Dresser Industries, Inc., Dallas, Tex., a corporation of Delaware Filed Nov. 2.9, 1968, Ser. No. 780,041 Int. Cl. E21b 45 00 U.S. Cl. 73-151 19 Claims ABSTRACT OF THE DISCLOSURE An electronic system self-contained within a skid or trailer-mounted console provides a completely new set of well statistics once each minute or once each foot, thus giving the drilling operator a continuous picture of drilling conditions. Information recorded by the system includes drilling depth, time, penetration rate, hook load, rotary speed, pump strokes, gas chromatography, and such drilling mud information as weight-in, weight-out, viscosity and temperature and flow rates. A drilling mud pit volume totalizer sub-system includes mean for monitoring the mud volume in each of a series of drilling mud pits, means for adding the individual volumes to monitor the total mud volume in the system and also means to include the residual drilling mud located beneath the mud level sensors Within the total mud volume. Also included within the system is mechanical apparatus and associated electronics for monitoring the true depth and rate of penetration of the drill bit and associated drill pipe and also the speed of rotataion of the drill bits.

BACKGROUND OF THE INVENTION This invention relates to a system for providing a continuous indication of drilling conditions relating to the drilling of oil and gas wells. In particular, the invention relates to an electronic system wherein the drilling operator is provided a complete prole of up-to-date well statistics, thus giving the operator a continuous picture of drilling conditions.

In the art of drilling oil and gas wells, the drilling operator frequently drills at less than peak penetration rates because of the ever constant danger of blow-outs. Such blowouts are commonly caused by the existence of a formation pressure a the bottom of the drilled hole which exceeds the hydrostatic pressure of the drilling mud column within the hole, thus creating a condition whereby formation uids are caused to flow into the well bore. These formation fluids, which commonly may be gas, oil, water, or combinations thereof, have low densities and the pressure difference which caused their ilow becomes even greater as these extraneous fluids rise in the well bore, thus displacing drilling mud out of the top of the casing. Whenever this occurs, a blowout is imminent unless the pressure difference which caused the formation fluid to ilow into the well bore is controlled, as for example, by closing a blowout preventer such as is usually provided at the top of the well. Because of the fact that blowouts are extremely dangerous and quite expensive,

many devices have been built and are used in the drilling art in an attempt to control and eliminate blowouts. For example, a system for killing oil and gas wells whenever a blowout is imminent is described in co-pending application U.S. Ser. No. 692,458, led Dec. 21, 1967, assigned to the assignee of the present invention. However, while such a system as is described in said co-pending application has been successful in the automatic control of an oil and gas well, there remains the ever present need for a system with improved monitoring and recording capability.

It is therefore the primary object of this invention to provide a system having improved monitoring capability relating to the drilling of oil and gas wells;

It is another object of this invention which provides a new and improved profile of the conditions relating to the drilling of an oil and gas well;

It is also an object of this invention to provide a system having improved capability for monitoring the total drill mud volume within the pits used in the drilling of an oil and gas well;

It is still another object of the invention to provide a new and improved system for monitoring the rate of penetration of a drill bit used in drilling an oil and gas well; and

It is another object of the invention to provide a new and improved system for monitoring the speed of revolution of a drill bit used in drilling an oil and gas well.

The objects of the invention are accomplished, generally, by a system wherein the drilling parameters and mud information parameters are continuously monitored to provide a continuous profile of the drilling conditions. An electronics sub-system provides a continuous monitoring of total drill mud volume which is corrected for the residual mud volume within the drill mud pits. There is also provided a mechanical and electronic sub-system for continuously monitoring the rate of penetration and also the total amount of penetration of the drill bit and associated drilling pipe, as well as the speed of rotation of the drill bit.

Other objects, advantages, and features of the invention will be evident hereinafter in the more detailed description of the invention.

In the drawing, which illustrates the preferred embodiments and modes of operation of the invention and in which like reference characters designate the same or similar parts throughout the several views:

FIG. l is a schematic block diagram of the system according to the invention;

FIG. 2 is a schematic diagram of the apparatus and associated electronics for monitoring the total depth and rate of penetration of the drill bit according to the invention;

FIG. 3 schematically illustrates the switch closure mechanism and associated electronics for monitoring the speed of rotataion of the drill bit;

FIG. 4 illustrates schematically a circuit according to the invention for monitoring the total mud volume within the pits;

FIG. 5 illustrates schematically in more detail one of the balanced ampliers shown in block diagram in FIG. 1; and

FIG. 6 illustrates schematically the apparatus used for determining the rate of rotation of the drill bit and also the apparatus used for measuring the total depth and rate of penetration of the drill bit.

Referring now to the drawing in more detail, especially to FIG. l, there is illustrated in block diagram a system according to the present invention, A drilling platform 10, through which an earth borehole has been drilled, denoted generally by the reference numeral 11, has an R.O.P. (rate of penetration) and depth unit 12 mounted thereon. A pair of

mud pumps

13 and 14 are used to pump conventional drilling mud into and out of the well bore, all as is known in the art. The

mud pumps

13 and 14 first pump the mud into the standpipe line 18, where it is then pumped into the earth borehole. In returning from the earth borehole, the mud returns through the fiow line 19 into the shaker pit 17, and thereafter into the mud pit 16 and the suction pit 15. The mud is then returned into the

mud pumps

13 and 14, In the system according to the preferred embodiment of the invention, there is provided in the standpipe line 18 a conventional pressure sensor 20 which is used to monitor the mud pump standpipe pressure. There is also provided a sensor 21, for example, either a buoyant ball or a beam balance, which is used to monitor the weight of the mud in the fiow line 19. Each of the mud pits 15, 16 and 17 has a sensor, respectively identified as

sensor

22, 23, and 24, which is used to monitor the amount or volume of mud within the pits, all as is described hereinafter in more detail with respect to FIG. 4. Such a sensor is preferably of the resistance type, for example, a Metritape sensor available from Metritape Controls, Inc. of West Concord, Massachusetts, wherein a change in resistance is indicative of a change in the mud level. Associated with the

mud pumps

13 and 14 are a pair of

sensors

25 and 26, for example, a micro-switch responsive to the pump, which provide electrical indications of mud pump strokes per minute. A sensor 27, described in more detail with respect to FIGS. 3 and 6 hereinafter, provides an indication of the rotary speed of the drill bit associated with the system. A sensor 28 provides an indication of the hook load within the system, for example, the conventional hook load indicator available from Bell Engineering in Odessa, Tex. A conventional sensor 29 within the suction pit 15 provides an indication of the mud weight within the suction pit.

As is better described with respect to FIG. 4, the electrical outputs of the

sensors

22, 23 and 24 are combined within the circuitry identified generally as mud volume 30 in FIG. 1 to provide an indication of total mud volume.

The electrical outputs from the

sensors

20, 21, 22, 23, 24, 25, 26, 27, 28 and from the depth unit 12 are cornbined at the junction box 31. It should be appreciated that all of the circuitry and apparatus thus far described are generally associated with the drilling rig platform and mud pits.

The portion of the system shown within the dotted lines 32 in FIG. 1 is preferably mounted within a skid or trailer-mounted unit which can be transported to the site of the drilling platform. Within the dotted lines 32 is found a distribution panel 33 into which the connections are made from the junction box 31. It should be appreciated that there would normally be a cable approximately two hundred feet in length joining the junction box 31 and the distribution panel 33. Coupled to the output of the distribution panel 33 is a group of balanced amplifiers within the box generally identified as balance amplifier panel 34. A typical balance amplifier as is found within the panel 34 is illustrated in more detail with respect to FIG. 5 hereinafter. An R.O.P. and depth conversion unit 35, described in detail with respect to FIG. 2, is coupled into the distribution panel 33 and also into an analog-to-digital converter section 36 which preferably has a multiplex input. Although not illustrated in detail,

the system according to the invention has a clock built into the circuitry allowing time to be entered into the print-out, for example, on the

recorders

37 and 38. Further, the multiplexing and monitoring operations are timed for print-out once each minute. The gas chromatography section, not illustrated, makes use of a five point gas chromatograph on a two minute cycle, the output of which is recorded on a time drive chart, the time and depth markers on the chart being keyed to the time and depth on the automatic typewriter report from the rccorder 38.

A conventional analog recorder 37, for example, a Strip chart recorder, is coupled into the output of the balance amplifier panel section 34. A digital recorder 38, for example, a digital typewriter, is coupled to the output of the analog-to-digital converter 36.

Referring now to FIG. 2, there is illustrated a wheel 40 which rotates in response to the movement of the kelly and traveling block illustrated in FIG. 6. For purposes of FIG. 2, however, the Wheel 40 is caused to rotate in response to the movement of the cable 41. The wheel 40 has a circumference of two feet. `Coupled to the wheel 40 is another wheel 42 which creates a mechanical step-up of 20 rotations for the Wheel 42 for every rotation of the wheel 40. Through the belt 43, the wheel 42 causes the shaft 44 to rotate and thus drive the rotational encoder mechanism 45. Although there are various means known in the art for converting rotational movement into electrical pulses, the mechanism 45 can be, for example, an encoder such as is described in the co-pending application U.S. Ser. No. 577,345, filed Sept. 6, 1966 now U.S. Pat. 3,426,303 and assigned to the assignee of the present invention. The output of the mechanism 45 produces one hundred electrical pulses, each preferably having a square wave output, for each revolution of the shaft 44. The output of the apparatus 45 is coupled into a conventional filter and buffer section 46 and then into a gate circuit 47. Also coupled into the gate 47 is an interlock circuit 48, which may be, if desired, merely a manual switch which may be operated by the operator to close the gate 47 Whenever the cable 41 reverses direction. Such an interlock is desirable to thus provide an electrical indication of travel only whenever the traveling block and kelly assembly, illustrated in FIG. 6, is moving in the downward direction. If desired, however, the interlock circuitry 48 can be automatically responsive to the movement of the kelly in a downward direction and also act to close the gate 47 whenever the kelly 1s moving in the upward direction, as, for example, through a one-way clutch. If desired, the interlock circuit 48 could be made automatically responsive to a given speed of the drill bit, to Weight on the bit, or mud pump pressure, to name but a few examples. The output of the gate 47 is seen to travel in two directions. In the one direction, the output of the gate 47 drives a series of

electronic counters

49, 50 and 51, each of said counters preferably having a 10:1 ratio. Thus, for each of the counters having such a ratio, for each ten pulses into the counter, only one pulse is seen on its output. The output of the counter 51 is then coupled into a conventional accumulator circuit 52 which drives a diode matrix and buffer circuit 53 which in turn drives the readout section 54. It should be appreciated that the readout section 54 is not a recorder, but merely the point at which the circuit output appears.

In the operation of the circuit of FIG. 2 thus far described, it is seen that since the wheel 40 has a circumference two feet and because the wheel 42 bears a 1:20 ratio to the wheel 40, the shaft 44 makes 20 revolutions for each two feet of travel of the cable 41. For each one foot of travel, the shaft 44 makes ten revolutions. Since the device 45 creates one hundred pulses per revolution, the output of the device 45 is thus seen to be one thousand pulses per one foot of travel of the cable 41. Since the series of

counters

49, and 51 create a reduction of one output for each one thousand pulses in from the gate 47, it should be appreciated that the output of counter 51 therefore causes there to be one pulse per each foot of travel of cable 41. The output of the accumulator 52, as represented by five decades of BCD readout having 21 lines, is then coupled into the diode matrix 53 to drive the readout circuit 54.

The output of counter 49, having an electrical output of one hundred pulses for each foot of travel of the cable 41, is coupled into the driver circuit 55 which drives the recorder 37, for example, a pulse driven recorder commercially available from Texas Instruments, Incorporated of Dallas, Texas, such a recorder thus being driven as a function of movement of the cable 41, and hence depth of the drill bit. Such a recorder conventionally has a vertical scale wherein five inches is representative of 100 feet of travel. Since the output of the counter 49 is 100 pulses per foot of travel, the driver circuit 55 converts the 100 cycle per foot information into that necessary to cause one inch of travel by the recorder paper in the recorder 37 for every 20 feet of travel by the cable 41.

The output of gate 47 is also connected into a one shot multivibrator 60, the output of which is coupled into a filter 61 to drive an operational amplifier 62. The output of the amplifier 62 is coupled into an attenuator 63 to drive the recorder 37. Since the output of the amplifier 62 is indicative of the rate at which the one shot multivibrator fires, the output of the amplifier 62 is indicative of the rate at which the cable 41 is moving and hence the rate of penetration of the drill bit used in conjunction with the system. The output of the amplifier 62 is preferably set from 0 to 5 volts D.C., the

amplitude of which is directly proportional to the rateof penetration of the drill bit. Since the recorder 37 is driven in conjunction with the total depth at which the drill bit is found, it should be appreciated that the rate of penetration of the drill bit is recorded as a function of depth of the drill bit on the recorder 37.

Referring now to FIG. 3, there is illustrated circuitry which converts the rotation of the drill bit into a DJC. voltage which is linear with respect to the rotary speed of the drill bit. Within the dotted line area 27 there is illustrated a switch 71 which may be used to indicate that the kelly and drill pipe stem as illustrated in FIG. 6 are rotating at a determinable speed. In the preferred embodiment, the switch 71 is caused to be closed once per each revolution, as is explained in more detail with respect to IFIG. 6. As further illustrated in FIG. 3, the closure of the switch 71 causes the positive D.C. voltage on the line 72, for example, 15 volts, to be applied through the capacitor 73 into the inverting input 74 of the amplifier section 75. It should be appreciated that the amplifier section 75 and its associated

electronic components

73, 76, 77, 78, 79, 80, 81, 82, 83, 84 and 85 comprise a one shot oscillator and trigger section responsive to the closure of the switch 71 which causes a single voltage pulse to be delivered through the diode and resistor 91 into the base of the transistor 92 for each closure of the switch 71. The transistor 92 and the

circuit elements

93, 94, 95, 96, 97 and 93 together comprise an interstage coupling inverter section. The output of the transistor stage 92 is coupled from the collector element of the transistor 92 through the resistor 97 and the resistor 99 into the non-inverting input of the amplifier 101. The amplifier section 101 along with the

component parts

102, 103, 104, 105, 106, 107, 108, 109 and 110 together comprise a signal output and filter section, the output of which is a D.C. voltage which is linear with respect to the number of contact closures per unit time of the switch 71.

6 The following table (Table One) lists the values of the component parts corresponding to those illustrated in FIG. 3:

It should be appreciated that the operational amplifiers identified as 709cs are available from Fairchild Semiconductor in Mountain View, California. Since all the 709cs are identical, and have pins numbered 1-8, inelusive, the pins are so numbered in the drawing.

FIG. 4 illustrates schematically in more detail the R.O.P. and depth conversion circuit 35 of FIG. l. Since there are three substantially identical circuits connected to the output of the

sensors

22, 23, and 24 in FIG. 4, only one such circuit will be described in detail. The sensor 22, being a resistance type device inserted within the mud in the suction pit 35, is coupled into a balanced bridge circuit comprising the additional resistors 120, 121, and 122. A trimming potentiometer 162 is connected across resistor 122. The junction between resistors 121 and 122 is connected through resistor 12.3 into the inverting input of the amplifier 124. The other end of the resistor is coupled into the noninverting input of the amplifier 124. The amplifier 124 is connected as a differential amplifier to detect the difference between the voltages occurring at the two inputs. The output of the differential amplifier 124 is coupled through the potentiometer 125 and resistor 126 into the summing junction 127. In a similar manner, the other two circuits, being indicative of the electrical signals from the

sensors

23 and 24, are coupled through potentiometers 128 and 129, respectively and through the

resistors

130 and 131, respectively, to the summing junction 127. Also connected into the summing junction 127 is a voltage from the potentiometer 132 which is indicative of the residual mud within the pits, such an indication being necessitated by the fact that the sensors within the mud pits normally do not extend all the way to the bottom of the pit. Thus, by setting the potentiometer 132 and coupling the voltage from that potentiometer through the resistor 133 to the summing junction 127, the voltage appearing at junction 127 is the sum of the signals from the

sensors

22, 23, 24 and from the potentiometer 132. The amplifier 150 is connected as a summing amplifier to be responsive to the voltage appearing at the terminal 127. The voltage thus appearing at the output terminal 151 of the summing amplifier 150 is a linear D.C. voltage which is proportional to the total volume in the mud pits 15, 16 and 17 of FIG. l. The potentiometer 152 is used to adjust the balance of the summing amplifier 150.

The value of the components enumerated in FIG. 4 are set forth in the following table:

TABLE TWO Component: Value 2.7K ohm. 121 2 7K ohm. 122 330 ohm. 123 47K ohm. 124 709C. 125 100K ohm potentiometer. 126 100K ohm. 128 100K ohm potentiometer. 129 100K ohm potentiometer. 130 100K ohm. 131 100K ohm. 132 5 0() ohm potentiometer. 133 100K ohm. 134 100K ohm. 135 1.5K ohm. 1.36 .()1 pf., 200 volt. 137 47 ohm. `138 .001 pf., 200 volt. 139 47 ohm. 140 10() pf., 30 volt. 141 0.1 ttf., 200 volt. 142 .01 ttf., 200 volt. 143 100 pf., 30 volt. 144 47 ohm. 145 .01 af., 200 volt. 146 100 af., 30 volt. 147 470K ohm. 148 1.5K ohm. 149 .01 pf., 200 volt. 150 709e. 152 `100K ohm potentiometer. `153 100K ohm potentiometer. 154 .001 1,200 volt. 155 100 pf., 30 volt. 156 .01 pf., 200 volt. 157 47 ohm. 158 15K ohm. 159 4.7K ohm. 160 IN751, 5.1 volt Zener. 161 1.8K ohm. 162 500 ohm potentiometer.

FIG. 5 schematically illustrates one of the balanced amplifier sections within the balance amplifier panel 34 of FIG. 1. As illustrated in FIG. 5, either a D.C. or an A.C. input can be coupled through the terminals and 171, respectively, the A.C. input then being coupled through a capacitor 172. The signal or signals are then coupled through resistor 173 and may then be coupled into either the inverting input through the resistor 174 or directly into the non-inverting input. The switch 175 is used merely to indicate that one has a choice of input, inverting or non-inverting, to the amplifier 176. It should be appreciated that the potentiometer 177 and resistor 178 provide D.C. balance for the amplier. Likewise, the potentiometer 179 is used to control the gain of the balance amplifier. Thus, the output appearing at the F terminal 180 is a D.C. voltage which tends to facilitate the use of the information from the various sensors throughout the system for the conversion from analog voltages to digital voltages as accomplished Within the analog-to-digital converter 36 of FIG. 1. The circuit in FIG. S serves several functions within the system accordto the invention. It first of all provides a constant input impedance into the analog-to-digital converter 36. The circuit also provides a means for adjusting the gain or amplitude of the signals from the individual sensors. The circuit also provides a means for nulling out any noise within its associated signal channel. However, perhaps the most important feature of the circuit resides in its ability to match the calibration slope of a given sensor. The sensors themselves each have linear responses. The output output of the illustrated balance amplifier is a linear D.C. voltage. By the use of the gain control 179 and the balance control 177, the slope of the output curve appearing at junction 180 can be made to closely match the calibration slope of the given sensor.

It should be appreciated with this particular type of' operational amplifier 176, as Well as with the amplifiers used in the circuits of FIGS. 3 and 4, that the preferred positive D.C. voltage is l5 volts.

The values for the components of FIG. 5 are enumerated in the following table:

TABLE THREE Component: Value 172 5 af., l5 volt. 173 47K ohm. 174 5.1K ohm. 176 709e. 177 100K ohm potentiometer. 178 10M ohm. 179 100K ohm potentiometer. 181 47 ohm. 182 .0l af., 200 volt. 183 100 pf., 30 volt. 184 .U01/tf. 185 1.5K ohm. 186 .0l af. 187 150K ohm. 188 10K ohm. 189 10K ohm. 190 30K ohm. 191 47 ohm. 192 100 af., 30 volt. 193 .0l pf., 200 volt.

FIG. 6 illustrates schematically a pair of the sensors connected to the drilling rig apparatus. In FIG. 6, there is shown a borehole 200 (the lower portion of borehole 11 in FIG. l) penetrating the earth and in which is arranged a drill string 201, to the lower end of which is attached a drill bit (not illustrated). At the earths surface is arranged surface drilling equipment including a derrick 202. The hose 203 is connected to a mud standpipe (not illustrated), the hose 203 being connected to the swivel assembly 204. The kelly 205 is connected through the well head 206 to the drill pipe 201 in the conventional manner. Attached to the kelly 20S is a block of metal 207 capable of affecting an adjacent magnetic field which is caused to rotate as the kelly member rotates. Attached to the swivel member 204 is a non-rotating detector 27 having a built-in permanent magnetic field having contacts 71 which may be, for example, a read relay, which is caused to be actuated by the passing of the metal block 207 as the kelly rotates. It should be appreciated that the switch closure means 71 within the detector 27 corresponds to the switch 71 in FIG. 3. It should be appreciated further, that as the kelly 205 rotates, the drill pipe 201 also rotates with the drill bit, and hence the closure of the switch 71 is indicative of the rate of revolution of the drill bit.

Also illustrated in FIG. 6 is an apparatus for measuring the total depth and rate of penetration of the drill bit. Attached to the swivel member 204 is a cable 41 which passes over a wheel 210 attached to the frame of the derrick 202. The cable 41 also passes over the wheel 40 to cause the wheel 40 to turn directly proportional to the amount of travel of the cable 41. After passing over the Wheel 40, the cable 41 is wound upon a drum 211, the drum 211 being preferably provided with a suitable mechanism such as a spring motor (not illustrated) which is normally biased to rotate the. drum in a direction to wind the cable 41 thereon but yet is yieldably responsive to the pull of the cable 41 to permit unwinding of the cable from the drum 211. The cable 41 is thus fully capable of closely following the movement of the drill string. It should be appreciated that the wheel 40 as the cable 41 is caused to move by the kelly being moved downward, that the electronic circuitry described herein provides a measure of the depth and rate of penetration of the drill bit.

It should thus be appreciated that there has been described herein a new and improved system for continuously monitoring important parameters relating to the drilling of oil and gas Wells, such a system providing a continuous readout to the drilling operator. Although the preferred embodiments of the invention have been illustrated and described in detail, modifications of the embodiments illustrated herein will occur to those skilled in the art and it is contemplated that such modifications and changes as are within the spirit of the invention are to be Covered by the scope of the appended claims.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In an earth borehole drilling system having a drill rig and a drill mud pit associated therewith, a mud volume sub-system comprising:

a mud-sensitive sensor mounted in said mud pit;

first electrical circuit means responsive to said sensor producing a rst electrical signal functionally related to the mud level in said pit;

second electrical circuit means for producing a second electrical signal indicative of a residual amount of mud in said pit undetected by said sensor; and

means to combine said lirst and second electrical signals to provide an indication of the mud volume in said pit.

2. In an earth borehole drilling system having a drill rig and a drill mud pit associated therewith, a mud volume sub-system comprising:

a mud-sensitive sensor mounted at a given level in said mud pit;

first electrical circuit means responsive to said sensor producing a iirst electrical signal functionally related to the mud level in said pit;

second electrical circuit means for producing a second electrical signal indicative of a volume of mud in said pit beneath said given level; and

means to combine said first and second electrical signals to provide an indication of the mud volume in said pit.

3. In an earth borehole drilling system having a drill rig and a plurality of drill mud pits associated therewith, a mud volume sub-system comprising:

a plurality of mud-sensitive sensors, one of said plurality of sensors being mounted in each of said mud pits;

a plurality of electrical circuit means respectively responsive to said plurality of sensors, whereby a plurality of electrical signals are produced functionally related, respectively, to the mud level in each of said pits;

an additional electrical circuit means for producing an additional electrical signal indicative of a combined residual volume of niud in said pits undetected by said sensors; and

means to combine said plurality of electrical signals with said additional electrical signal to provide an indication of the combined mud volume in said plurality of pits.

4. In an earth borehole drilling system having a drilling rig wherein drill pipe and associated drill bit penetrate the l f earths surface, a total depth of penetration sub-system comprising:

means to translate the linear motion of the drill pipe into rotary motion; means to translate said rotary motion into a series of electrical pulses; means to count said electrical pulses, whereby said count provides an indication of the depth of penetration; and

means to gate said electrical pulses whereby said pulses are counted only wherever said linear motion is in one direction.

5. In an earth borehole drilling system having a drilling rig wherein drill pipe and associated drill bit penetrate the earths surface, a rate of penetration sub-system comprising:

means to translate the linear motion of the drill pipe into rotary motion;

means to translate said rotary motion into a series of time-spaced electrical pulses;

a single shot multivibrator responsive to said electrical pulses;

an operational amplifier responsive to the output pulses from said multivibrator, whereby the voltage output from said amplifier is proportional to the frequency of said electrical pulses, said voltage output providing an indication of rate of penetration.

6. The sub-system according to claim 5 including, in addition thereto, means for recording said indication of rate of peneration as a function of the depth of penetration.

7. In an earth borehole drilling system having a drilling rig wherein drill pipe and associated drill bit pentrate the earths surface, a combined rate of penetration and depth of penetration sub-system, comprising:

means to translate the linear motion of the drill pipe into rotary motion;

means to translate said rotary motion into a series of time-spaced electrical pulses; amplifier meansresponsive to said time-spaced electrical pulses, the voltage output of said amplifier providing an indication of the rate of penetration; and

means to count said time-spaced electrical pulses, whereby said count provides an indication of the depth of penetration.

8. The sub-system according to claim 7 including, in addition thereto, means for recording said indication of the rate of penetration as a function of the depth of penetration.

9. In an earth borehole drilling system having a drilling rig wherein drill pipe and associated drill bit penetrate the earths surface, a total depth of penetration sub-system comprising:

means to translate the linear motion of the drill pipe into a series of electrical pulses;

means to count said electrical pulses, whereby said count provides an indication of the depth of penetration; and

10. In an earth borehole drilling system having a drilling rig wherein drill pipe and associated drill bit penetrate the earths surface, a rate of penetration sub-system coinprising:

a single shot multivibrator responsive to said electrical pulses;

11. The sub-system according to claim including, in addition thereto, means for recording said indication of rate of penetration as a function of the depth of penetration.

12. In an earth borehole drilling system having a drilling rig wherein drill pipe and associated drill bit penetrate the earths surface, a combined rate of penetration and depth of penetration sub-system, comprising;

means to translate the linear motion of the drill pipe into a series of time-spaced electrical pulses;

amplifier means responsive to said time-spaced electrical pulses, the voltage output of said amplifier providing an indication of the rate of penetration; and

13. The sub-system according to claim 12 including, in addition thereto, means for recording said indication of the rate of penetration as a function of the depth of penetration.

14. In an earth borehole drilling system having a drilling rig wherein drill pipe and associated drill bit penetrate the earths surface, a drill pipe rate of rotation sub-system, comprising:

a traveling block and kelly assembly, wherein said kelly rotates at the same rate of rotation as said drill pipe during a drilling operation;

a non-rotating swivel assembly attached to said kelly assembly;

switch means mounted on said swivel assembly;

means mounted on said kelly for activating said switch means as said kelly rotates; and

electrical circuit means responsive to the closure of said switch means to provide an indication of the rate of rotation of said drill pipe.

15. The sub-system according to claim 14 wherein said means mounted on said kelly comprises a sensor with a permanent magnetic field and said switch means is responsive to interruption of the magnetic field by a rotating metallic block.

16. ln an earth borehole drilling system having a drilling rig and at least one mud pit associated therewith, wherein the drill pipe and associated drill bit in the system penetrate the earths surface, comprising:

means for producing a first linear electrical signal indicative of the total mud volume in said at least one mud pit, said means having an output following a first given calibration slope;

means for producing a second linear electrical signal indicative of the rate of revolution of said drill bit,

said means having an output following a second given calibration slope;

means for producing a third linear electrical signal indicative of the rate of penetration of said drill bit, said means having an output following a third given calibration slope;

first, second and third amplifier means responsive, re-

spectively, to said first, second and third electrical signals, each of said amplifier means having adjustment means for matching the slope of the output voltage of the amplifier with the given calibration slope of its respective electrical signal producing means; and

means for providing a correlative indication of the output voltages of said amplifies.

17. The system according to claim 16 including, in addition thereto, means for converting the output voltages from said amplifiers into digital signals.

18. The system according to claim 17 including, in addition thereto, means for recording said digital signals.

19. In an earth borehole drilling system having a drilling rig and at least one mud pit associated therewith, wherein the drill pipe and associated drill bit in the system penetrate the earths surface, comprising:

means for producing a first electrical signal indicative of the total mud volume in said at least one mud pit;

means for producing a second electrical signal indicative of the rate of revolutions of said drill bit;

means for producing a third electrical signal indicative of the rate of penetration of said drill bit; multiplexer means connected to said first, second and third electrical signals;

means connected to said multiplexer means for converting said electrical signals into-digital signals; and means for providing a correlative indication of said digital signals.

References Cited UNITED STATES PATENTS 2,287,819 6/1942 Nichols 73-151.5 X 2,539,758 1/1951 Silveman et al. 73--151.5 2,807,678 9/1957 Rapp 330-96 X 3,445,767 5/1969 Beard.

JERRY W. MYRACLE, Primary Examiner U.S. C1. XR. 73-149, 151.5