US3136975A - Monitoring circuit for logging instruments - Google Patents

Description

June 9, 1964 R. H. KOLB MONITORING CIRCUIT RoR LoGGING INSTRUMENTS Filed July 20. 1959 l l I Pmv INVENTOR ROBERT H. KoLB BKL/1W TMW HIS ATTORNEY United States atent lice 3,136,975 MONITORING CIRCUIT FOR LOGGING INSTRUMENTS Robert H. Kolb', Houston, Tex., assignor to Shell Oil Company, a corporation of Delaware Filed July 20, 1959, Ser. No. 823,2tl8 3 Claims. (Cl. 34018) This invention pertains to a monitoring system and more particularly to a system which is designed to monitor a device and its associated circuit as it is being installed 111 an oil well or the like.

Many devices are semi-permanently installed inthe bottom of oil wells and the like for determining various physical properties. For example, pressure and temperature transmitters are installed in the bottom of oil wells and connected to surface recording equipment by a connecting cable. As these devices are being installed in oil wells they receive considerable mechanical shock and thus often times either the device or its associated In some installations the downhole tion tubing string. Normally the damage is not discovered until after installation is completed and an attempt is made to obtain information such as downhole pressure or downhole temperature from the device which has been installed. Since the damage is not discovered until after the installation is completed and the rig has been removed from the well considerable expense is involved in retrieving the device, correcting the trouble and reinstalling it. The cost involved is readily apparent when it is remembered that the average oil well in the United States is on the order of 7,000 to 10,000 feet deep lvice and its associated circuit and periodically indicate the condition'of the ldevice and its circuit as the downhole instrument is being installed.

A further object of this invention is to provide a small lcompact automatic monitoring system which audibly indicates the condition of the downhole device and its associated circuit during its installation in the wellbore without requiring either manual attention or observation.

The above objects and advantages of this invention are obtained by providing a device which will periodically interrogate the downhole device and its associated circuit yand receive a return response indicating the condition of the downhole device and its circuit. The response of the device to the interrogation is amplitied and passed through an audio speaker so that an audible sound-orringing will be obtained. Thus, if the device is interrogated at set time intervals an associated audible sound will be produced. The people associated with the installation will only be required to listen for the audible sound and not required to check or initiate any tests in order to determine Whether the device and its associated circuit is in a satisfactory operating condition.

The above objects and advantages will be more easily understood from the following detailed description of a preferred embodiment when taken in conjunction with the attached drawing showing a schematic diagram of this invention as applied to a downhole pressure transmitter.

Referring to the attached drawing, there is shown a downhole pressure transmitter 10, a pulsing circuit 11 and an amplifying circuit 12. The downhole pressure transmitter may be of any design such as the one illustrated and described in the applicants copending application, Serial No. 731,328, filed April 28, 1958 and now Patent Number 3,062,052. This typeof transmitter utilizes a vibrating string whose frequency varies with pressure. It is interrogated by drawing the string to one side by means of a coil and armature and then releasing the string, the

.vibrations of the string inducing an alternating signal in the coil. This invention is designed to periodically test the operation of the downhole pressure transmitter 10 and the cable 14 in order to ascertain that itis in a satisfactory operating condition during its installation in a well. The surface equipment generates a periodic pulse which is transmitted down the cable 14 to interrogate the transmitter 10 and then audibly reproduces the transmitter response. The surface equipment also audibly reproduces the interrogating pulse thus indicating that the surface equipment is operating satisfactorily and has actually transmitted a pulse tothe transmitter 10.

As shown on the drawing, the pulsing circuit 11 utilizes a variable resistor 20 in series withA a fixed resistor 21 and a capacitor 22 as a resistance capacitor circuit for determining theA period between individual-pulses. The variable resistor 20 and fixed resistor 21 are in'series with a second fixed resistor 27 which forms part of a second resistance capacitance circuit. The resistance capacitor circuit is coupled by means of a lead 25 to the positive side of a battery 23 whose negative side is grounded at 24. Thus, the capacitor 22 will be charged exponentially to a final voltage which is determined by the reakdown voltage of the diode 26. More particularly, the diodes 26 and 32 are four-layer, two lterminal semiconductor devices. The diodes 26 and 32 have the particular quality of acting as a switch in that they remain open and exhibit a relatively high resistance until a predetermined voltage level is exceeded at which level they break down and exhibit a relatively low resistance thus acting as a switch. In a particular circuit the resistances 20 and 21 have a value of approximately 50,000 ohms and the capacitor 22 a value of 100 microfarads, the resistance 27 having a value of approximately 80 ohms, and the diode 26 having a breakdown voltage of 30 volts. Thus, the capacitor 22 will be charged until it reaches a voltage level of 30 volts at which point the diode 26 will break down and the capacitor discharge through the remainder of the circuit to the ground 24. If the resistance 20 is provided with a suitable range one may obtain a charging time for the capacitor 22 on the order of 10-15 seconds and thus the period of the pulse may be varied between these limits. f

After the diode 26 breaks down and permits the capacitor 22 to discharge through the remainder of the circuit, the capacitor 31 will be charged to the breakdown voltage of the diode 32. The capacitor 31 is in series with the resistance 27 and thus forms a second resistance capacitance circuit. The capacitance 31.is connected to the ground 24 by means of leads 44 and 45. The diode 32 is selected so as to have a lower breakduration. This pulse is coupled to the center conductor' 40 of the logging cable 14 by means of a current limiting resistor 30, the lead 34, diode 35 and lead 36. The

pull stage being` coupledto a speaker lfthrough an outputtransformer 60. `As shown, the transistors of the audio amplifier may be suppliedwith power from a single diode 35 should be selected Vto have al certain threshold v voltage on the order of one volt or the like.

Theshield or outer conductor r41 of the'logging cable .14 is connected to the ground 44 by means of lead 42.V

A second diode 43 is disposed in the opposite direction to and parallel Vwith diode 35 in order to provide al path to ground for the decreasing portion of the pulse as will be'explained below. i y Y When the above-described pulsing circuit is operated by closing the switch 37 on the battery 23 the capacitor 22 will charge as described above until the breakdown Y voltage of the VVdiode 26 is reached. This voltage. level is approximately 30 -volts for the example given above and'is reached in approximately 10-15v seconds depend-V I ing Vonthe setting of the resistance 20. This voltage of when the diode 26 breaks down. When the diodev 26 breaks down it permits the capacitor l2,2 todischarge Vthrough the remainderY of the pulsing circuit to the ground- 24, thus charging Vthe capacitor 31. As capacitor 31 charges it will generate an exponentially increasing volt-v age pulse at the point 33 having a substantial instantaneous return to zero when the breakdown voltage level of the diode 32y is reached; This pulse kwill be transmitted :25 course will have an exponential form well known in their. Tcharging of acapacitor and a sharp decrease to'zero through the diode 35 in a substantially unaltered form to the downhole pressure transmitter 10., Itis desirable to use a pulsewhich has an` exponential wave form on its forward side and a steep wave form 1on its back side,-

in contrast to a square wave pulse for actuatingthe downhole pressure transmitterrlt). This results from 'Y' coupling the device to the surface ofthe Well, a pulsing the fact that the pressure transmitter 10 utilizesa vibratf ing string and if the string was Vpulled sharply to-one side through rthel use of a pulse having a square Ywave shape the string would vibrate in the displaced position and in case it was released by the square wave pulse on the inward half cycle/of its vibration the subsequent signal would have a greatly diminished amplitude.

ing Voltage pulse since the string is slowly pulled towards the magnet thus preventing its vibration until-'it is released by the breakdown of the voltage pulse. t

The voltage pulse transmittedfover the cable 1.4 rises to a maximum value and then falls to zero. The diode 35 blocks the path to ground for the falling pulse and thus the pulse tends to charge the cable 14,due to its capacitance. path to ground is provided by inserting' diodel43 Vvin parallel with and in opposite direction to the diode 35. This path through the Vdio'desg43 and 32 will permit the fallingv signal from the cable 14 to be bypassed tothe ground 24 and 'thus maintain the cable relatively free of any charge. to ground it isolates thisV ground'path for the low amplitudel return signals from the'trarismitter because of its threshold voltage and, thus the two diodes 35 and 43 act as a switch to couple thev pulsing circuit to the vcable 14V during'theY pulsing period and disconnect. it vduring the receiving period. f l Y The signal from the transmitter v10 is coupled tothe audio amplifier 12 through a blocking capacitor l50. The'r audio amplifier. 12 is providedwith three single stages This dificulty is avoided by using thel exponentially increasf Even though the diode 43 provides 'aV path To prevent this buildup of a charge a battery 5'7k if so desired. v

`jFrom the above description it can-be' appreciated that Y this invention has provided a simple pulsing circuit which.'Y utilizes all solid ystate elements to generatef periodic pulses for interrogating the pressure transmitter V10 and for connec'ting cable 14, as the pressure transmitter is installed in a well. The kuse'fofisolidV state elements'r'esults in aV very reliablefdevicewhich has relatively low power re-VA Y quirements. Furthermore, theperiod ofthe pulse may be varied over VaY relatively-Wide range through the use Vof the variable're'sistance 20. Also. the `pulse supplied for interrogating the pressure transmitter :10 hasan exponentially increasing forward side whichinsures thatV the audio signal ygenerated bythe vibratingA string of the pressure transmitter will have a uniform amplitude.y Finally, the audio amplilier V12 will audibly reproduce both the Vinterrogating pulse rsupplied to thep'ressure transmitter as well as ltheau'dio signahfrom the pre`sV sure transmitter. Thus, the personinstalling th'efpres.-

sure transmitterwill iirst hear the iiterrogating pulse and` an instant later the'pulse of theV pressure transmitter. If the interrogating pulse is not heardV i t indicates thatfthe n Y pulsing circuit is'malfunctioning: whi1e`if the int'er'ro-Vy gating pulse is heard butnotthe audible signal fromthe pressure transmitter, it would indicate that the cable Ycir-` cuit 14 or the pressure transmitterrlO is malfunctioning. i Therefore, the invention audiblyV indicates both the functioning ofthe pulsing circuit and the(Y pressure transmit- ,ter and associated circuit. 1 Y ,Y Y While but a single embodiment of this invention has been .shown and described-'in detailV it shouldnot beV limited to the details described but only tov its'broad spirit 1 and scope;

jI claim asV my invention: Y Y

1. A system yfor monitoring the installation in .a-wellboreV o'f a vibrating string device ycapable of'measuring a physical characteristic, said system comprising: a cable age; said second capacitance'resistance-circuit having a .n relativelyshort'rtime constant Vand coupled to ground throughk a secondA static device having a predetermined breakdown voltage; saidsecond capacitanceresistance circuit being coupled to said cable througha diode totransmitv the pulse produced by'said second capacitance resistance circuit; to energizethe device saidk cable in additionV beingcoupled to an amplifier andk audioV reproducing means located at the Vsu'rfacefto reproducebo'th Y said ypulseand the responseof the device.

2.L A system for monitoring thef installation in a Wellbore `of a vibrating string device capable of measuring a physical quantity; saidl system comprising: a-cable coupling the device toV the surface of the well,`"arpulsing I circuit locatedat the lsurface and having a lfirst capaci-- V,tance "resistance circuit having an adjustable time Icon-VV stant, ysaidy capacitance resistance circuitbeing coupled .to a secondV capacitance resistancecircuit through a :iirst static device having apredetermined breakdown voltage; said second capacitance resistance ,circuit having a relative short time constant and coupledto ground ,through a second static device Vhaving afpredetermined breakformed by transistors 51, 52 and 53 anda push-pull out- I put stage-formed by transistors 55 and 56.' The output of transistor 53 is coupled to the push-pull output stage n through a transformer54 with the outputfrom the pushsistance circuit to energias its device; saidl cable inadj dition: being coupleditolanaudio amplifieriandspeaker system located at the'` surface to reproduce both ksaid pulse and the response of the deviceiand a secondV dioder Y disposed in parallel with but opposite to said lirst diode to provide a path to ground.

3. A system for monitoring the installation of a de vice in a Wellbore comprising: a cable coupling the device to the surface of the Well, said device supplying an audio frequency signal when interrogated by a pulse of sucient magnitude; a pulsing circuit including a first means for generating a periodic pulse having a preset repetition rate, a second means energized by the pulse of said first means for generating a second pulse capable of interrogating the device; unidirectional circuit means for coupling the second pulse to said cable and another circuit means coupling the response of the device to an amplier means whereby the device is interrogated and both the second pulse and audio frequency signal from the device are audibly reproduced.

References Cited in the le of this patent UNITED STATES PATENTS Kinley Ian. 3, OBrien May 27, Schultz Nov. 16, Martin Nov. 14, Thomas Aug. 17, Atkinson Nov. 30, Curtis Jan. 10, Summers Mar. 6, Aigrain July l5, Rumble Dec. 1, Mason Apr. 18, Ruehlemann Sept. 5,

Claims (1)

1. A SYSTEM FOR MONITORING THE INSTALLATION IN A WELLBORE OF A VIBRATING STRING DEVICE CAPABLE OF MEASURING A PHYSICAL CHARACTERISTIC, SAID SYSTEM COMPRISING: A CABLE COUPLING THE DEVICE TO THE SURFACE OF THE WELL, A PULSING CIRCUIT LOCATED AT THE SURFACE AND HAVING A FIRST CAPACITANCE RESISTANCE CIRCUIT HAVING AN ADJUSTABLE TIME CONSTANT, SAID CAPACITANCE RESISTANCE CIRCUIT BEING COUPLED TO A SECOND CAPACITANCE RESISTANCE CIRCUIT THROUGH A FIRST STATIC DEVICE HAVING A PREDETERMINED BREAKDOWN VOLTAGE; SAID SECOND CAPACITANCE RESISTANCE CIRCUIT HAVING A RELATIVELY SHORT TIME CONSTANT AND COUPLED TO GROUND THROUGH A SECOND STATIC DEVICE HAVING A PREDETERMINED BREAKDOWN VOLTAGE; SAID SECOND CAPACITANCE RESISTANCE CIRCUIT BEING COUPLED TO SAID CABLE THROUGH A DIODE TO TRANSMIT THE PULSE PRODUCED BY SAID SECOND CAPACITANCE RESISTANCE CIRCUIT; TO ENERGIZE THE DEVICE SAID CABLE IN ADDITION BEING COUPLED TO AN AMPLIFIER AND AUDIO REPRODUCING MEANS LOCATED AT THE SURFACE TO REPRODUCE BOTH SAID PULSE AND THE RESPONSE OF THE DEVICE.

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