Title:
Well bottom hole status system
United States Patent 3905010
Abstract:
A well bottom hole status system for measuring fluid reservoir pressure and temperature at the bottom of a well bore. An instrumentation unit is removably secured to the bottom of the well tubing for sensing fluid reservoir pressure and temperature and for transmitting the pressure and temperature data through the well tubing to the surface using electromagnetic radiation. Receiver and data processor means are located at the surface for receiving, processing and displaying said data. The medium for the transmission of the data may be either the fluid within the tubing using the said tubing as a wave guide, or by means of fiber optic wave guides disposed within the said tubing.


Inventors:
FITZPATRICK JOHN DOUGLAS
Application Number:
05/406858
Publication Date:
09/09/1975
Filing Date:
10/16/1973
Assignee:
Basic Sciences, Incorporated (Tulsa, OK)
Primary Class:
Other Classes:
340/854.6, 340/870.09, 340/870.28, 398/109
International Classes:
E21B47/06; E21B47/12; (IPC1-7): G01V1/40
Field of Search:
340/18NC,189 325
View Patent Images:
US Patent References:
Primary Examiner:
Wilbur, Maynard R.
Assistant Examiner:
Birmiel H. A.
Claims:
What is claimed is

1. A well bottom hole status indicator system for detecting fluid reservoir pressure and temperature at the bottom of the well bore having tubing extending from the well head to the well bottom hole fluid reservoir and comprising bottom hole instrumentation means removably installed in the well bore in the proximity of the bottom of the well tubing, said bottom hole instrumentation means comprising sensing means for sensing fluid reservoir pressure and temperature, data conversion means operably connected to the sensor means to produce data corresponding to the output of the sensing means, electromagnetic transmitting means operably connected to said data conversion for transmitting data to the well head, said transmitting means comprising a microwave transmitter having a microwave antenna operably connected thereto, said antenna being disposed within the well tubing, power supply means disposed within the bottom hole instrumentation means and operably connected to the sensing means, the data conversion means and the transmitting means; data receiving and processing means disposed at the well head for receiving and processing data from said instrumentation means; and wave guide means interposed between the bottom hole instrumentation means and the data receiving and processing means for guiding the transmitted data to the well head data receiving and processing means, said wave guide means being the tubing itself, the frequency of the microwave transmitter being tuned to an optimum frequency for transmission through the fluid in the tubing and along the inside wall of the tubing, and wherein the data receiver and processing means comprises the microwave receiver having a receiving antenna operably connected thereto, said antenna being disposed inside the tubing at the well head.

2. A well bottom hole status indicator system as set forth in claim 1 wherein the microwave transmitter comprises an oscillator which is operably connected to and keyed by the data conversion means and a harmonic multiplier for stepping up the output frequency of the oscillator to a frequency suitable for transmission through the fluid using said tubing as a wave guide.

3. A well bottom hole status indicator system as set forth in claim 1 wherein the microwave receiver comprises a sum and difference mixer operably connected to the receiving antenna, a local oscillator connected to the mixer, an intermediate frequency (IF) amplifier connected to the output of the mixer for amplifying the difference frequency whereby lower frequency well head equipment may be utilized for receiving and processing the bottom hole data.

4. A well bottom hole status indicator system as set forth in claim 1 and including alarm means disposed within the bottom hole instrumentation means and being operably connected between the sensing means and the transmitting means for keying alarm transmission signal when the fluid reservoir status exceeds predetermined conditions.

5. A well bottom hole status indicator system as set forth in claim 4 wherein said alarm means comprises at least one status limiting means, means for comparing said status limit means to the output of the sensing means, alarm generator connected to the output of the means for comparing said status limit means to the output of the sensing means and the transmitting means.

6. A well bottom hole status indicator system as set forth in claim 5, wherein a delay relay is interposed between the means for comparing said status limit means to the output of the sensing means and the alarm generator for intermittently permitting the alarm generation to conserve power.

7. A well bottom hole status indicator system as set forth in claim 5 wherein the means for comparing the status limit means to the output of the sensing means comprises an operational amplifier.

Description:
BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to improvements in both method and means for monitoring the reservoir pressure and temperature at the bottom of a well bore and more particularly, but not by way of limitation, to a well bottom hole status monitoring system wherein an instrumentation sensing unit having electromagnetic radiation transmission means is installed at the bottom of a well bore at the lower end of the well tubing for sensing pressure and temperature and transmitting data to the well head.

2. Description of Prior Art

This invention is related to the means for measuring pressure and temperature disclosed in the patent to Fitzpatrick U.S. Pat. No. 3,732,728, issued on May 15, 1973, and entitled BOTTOM HOLE PRESSURE AND TEMPERATURE INDICATOR. As set forth in the patent to Fitzpatrick (U.S. Pat. No. 3,732,728), for effective management of producing oil wells, gas wells and the like, it is necessary that the fluid reservoir pressure and temperature at the bottom of the borehole be monitored on a regular basis in order to determine dangerous pressure build-ups, temperature fluctuations, or the need for treating said wells to increase production therefrom. Heretofore, the monitoring of these oil and gas wells has been accomplished by lowering temperature and pressure sensing apparatus down through the tubing after completely shutting the said well down which is a time consuming and very expensive process.

The patent to Fitzpatrick (U.S. Pat. No. 3,732,728) addressed this problem by installing a bottom hole pressure and temperature instrumentation system within the reservoir and transmitting said information to the surface by sonic means and magnetic flux means using the well tubing as an information conductor for the data. Certain inherent disadvantages are present when using sonic transmission along the well tubing, the primary one being the introduction of false or erroneous signals caused from extraneous sound sources either within the well or within the well head machinery in contact therewith. The flux method is found to be inefficient due to flux leakage between the well tubing and the casing.

SUMMARY OF THE INVENTION

The present invention contemplates a novel method and means for monitoring the reservoir pressure and temperature at the bottom of a well bore which is particularly designed and constructed for overcoming the above disadvantages. The present invention is particularly suited to free flow wells wherein the pressure within the reservoir is sufficient to allow flowing of the product to the well head without the installation of sucker rods or pumps located within the well tubing. The present invention comprises temperature and pressure sensing means substantially permanently located at the bottom of the well tubing within the fluid reservoir, data conversion means for converting the sensor information into intelligent signals for keying electromagnetic transmitters also located in the bottom hole instrumentation unit.

Two basic types of transmission are disclosed herein, one of which is a microwave transmission which utilizes the fluid within the tubing as the medium of transmission and is also tuned to a frequency to permit the use of the inside of the well tubing itself to act as a wave guide for transmission of the electromagnetic signal to the surface. A second means for transmitting the said information to the surface by electromagnetic means is that of the use of fiber optic strands connecting the bottom hole instrumentation unit to a well head receiver system. In the case of the use of fiber optics as a wave guide for the signal, it has been found that laser transmission is most adaptable. For use with either means of transmission, a well head receiver, data processor and an optional alarm system is located at the well head for receiving and processing the data from the bottom hole instrumentation unit.

By the use of electromagnetic radiation transmission, the chances of interference or extraneous signals being introduced into the data information is greatly lessened and as a result thereof the information received at the well head is highly reliable.

A bottom hole pressure and temperature alarm system is also contemplated as an optional part of this invention whereby both the upper and lower pressure and temperature bounds may be monitored so that if the pressure or temperature goes outside these bounds, an alarm signal is transmitted to the surface of the well. This is desirable so that preventive measures may be taken to prevent reservoir wall cracking, the pumping of a dry hole which burns out pumping equipment, and the like.

DESCRIPTION OF THE DRAWINGS

Other and further advantageous features of the present invention will hereinafter more fully appear in connection with a detailed description of the drawing in which:

FIG. 1 is an elevational sectional view of a well bore having an instrumentation unit installed at the bottom thereof and a receiver and data processing unit installed at the upper end thereof.

FIG. 2 is an elevational section view of the bottom hole instrumentation unit having microwave transmission equipment installed therein.

FIG. 3 is an electrical schematic of the microwave transmitter of FIG. 2.

FIG. 4 is a block diagram schematic of the well head receiver and data processing unit of FIG. 1.

FIG. 5 is a sectional elevational view of a well bore depicting an instrumentation unit located at the bottom thereof and a receiver and data processing unit located at the upper end thereof.

FIG. 6 is a sectional elevational view of the instrumentation unit of FIG. 5 depicting a laser, receiver and transmission system located therein a fiber optic means located within the tubing thereof.

FIG. 7 is an electrical schematic diagram of the laser and receiver system located in the bottom hole instrumentation unit of FIG. 6.

FIG. 8 is an electrical and block diagram schematic of the well head receiver data processing and transmission system of FIG. 5.

FIG. 9 is an electrical and block diagram schematic of an optional temperature or pressure alarm system which may be disposed within the bottom hole instrumentation units.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawings in detail, reference character 10 generally indicates a well bore in the earth 12 connecting the surface thereof with a fluid reservoir 14 of oil, gas and the like. Normally, the well bore is lined with a casing 16 which extends from the surface of the earth 12 down to and into the reservoir 14. The area between the casing and the rough borehole 10 is normally filled with a concrete or the like substance 18 to support the said casing. Disposed within the said casing is an elongated vertically disposed tubing 20 which extends from the surface of the well into the reservoir pool 14 at the bottom of the oil well bore. Reference character 22 generally indicates a bottom hole instrumentation unit which is secured to the bottom of the tubing 20 by means of a threaded or sealed attachment means 24 as depicted in FIG. 2. The lower end of the tubing itself is provided with a plurality of spaced holes, not shown, therearound to allow the fluid from the reservoir to enter the tubing and rise to the surface of the well. An information receiver means 26 is disposed at the well head and is operably connected to a data process means 28 connected thereto. The output of the data processing means 28 may also be connected to an optional alarm means 30.

The bottom hole instrumentation unit 22 generally comprises an elongated vertically disposed housing 32 which is secured to the bottom of the tubing 20 by the attachment means 24. The housing 32 comprises a lower compartment 34 having a pressure transducer 36 and a temperature transducer 38 disposed therein, the sensing elements 40 and 42 of the pressure transducer and the temperature transducer, respectively, being exposed to the reservoir 14 through the bottom of the housing 22. Another compartment 44 is provided for housing a power supply 46 which may be a battery operated supply or even a long life nuclear power supply. The unit 22 also comprises a third electronics bay compartment 48 which is surrounded by insulation 50 and houses a data conversion means 52 and transmitter means 54. The data conversion means 52 is operably connected to the output of the pressure and temperature transducers 36 and 38 and to the power supply 46. The output of the data conversion is operably connected to the input of the transmitter means 54. The data conversion means may be any electronic means for converting the pressure and temperature outputs of the transducers 36 and 38 into either a frequency or amplitude modulated signal which is proportional to the pressure and temperature sensed by the transducers 36 and 38 or to a binary coded signal or the like.

An antenna 56 is disposed within the lower end of the tubing 20 and is operably connected to the output of the transmitter 54 by means of a coax cable 58 which is sealingly disposed through the housing attach means 24 and the insulation means 50.

Assuming that the output of the data conversion means 52 is in the form of serial square wave pulses, FIG. 3 represents a schematic diagram of a microwave transmitter means suitable for transmitting the serial information from the data conversion means to the well head.

Referring now to FIG. 3, reference character 54, generally indicates the transmitter means and comprises an oscillator circuit 60, the output of which is connected to a harmonic tripler circuit 62. The power supply unit 46 is generally indicated by a battery symbol in the circuit.

The oscillator circuit 60 generally comprises a transistor Q1 having the base thereof connected to the output of the data conversion means 52 through a resistor R1. The emitter of the transmitter Q1 is connected to ground or the negative output terminal of the power supply 46 and the collector thereof is operably connected to the emitter of a second transistor Q2 through an inductor L1 in series therewith. The collector of the transistor Q1 is also connected to ground through a resistor R2 and the emitter of the transistor Q2 is connected to ground through a variable capacitor C1. The base of the transistor Q2 is connected to ground through a resistor R3 and a fixed capacitor C2 in parallel therewith. The base of the transistor Q2 is also connected to the positive output terminal of the voltage power supply 46 through a resistor R4 and the collector of the transistor Q2 is connected to the positive output of the terminal of the power supply 46 through an inductor L2.

The output of the oscillator circuit 60 or more specifically the output at the collector of the transistor Q2 is connected to the harmonic tripler circuit 62 which comprises a pair of parallel connected inductors L3 and L4 connected between the collector of the transistor Q2 and the negative output terminal of the power supply 46 through variable capacitors C3 and C4, respectively, in series therewith. The output of the oscillator 60 is also connected to the antenna 56 through an inductor L5 and a variable capacitor C5 connected in series therewith.

In operation, data from the data conversion means 52, in serial form, is applied to the input or base of the transistor Q1 through the resistor R1 thereby saturating the transistor Q1 which places the emitter of the microwave transistor Q2 near DC ground. This allows oscillation at the fundamental oscillator frequency determined by the values of capacitors C1 and C2. The oscillator at fundamental frequency then feeds the harmonic tripler network 62 which is tuned to pass the third harmonic of the oscillator. The tripler 62 then feeds a coax to wave guide antenna 56, the wave guide being formed by the tube or pipe string 20 which is continuous from the bottom hole of the well to the well head.

The optimum frequency of radiation for utilizing the well string or pipe string 20 as a wave guide is found by the equation: ##EQU1## where f is the frequency, c is the speed of light in the medium, which in this case would be the reservoir product, and d is the inside diameter of the pipe string 20. The speed of light in the medium is found by: ##EQU2## where Co is the speed of light in a vacuum (3.0 × 1010 cm/sec) and N is the index of refraction of the medium or reservoir product which yields ##EQU3## For example in the case of a 2 inch ID pipe string 20 (5.08 cm) and a medium such as Benzene having index of refraction N = 1.5 the output frequency from the tripler 62 would be ##EQU4## Therefore the frequency of the oscillation 60 would be 1/3f or 8.75 × 108 Hz.

Referring now to FIG. 4, reference character 64 generally indicates a microwave receiver antenna which is located near the well head but still disposed in the fluid medium. The antenna 64 extends into the pipe string 20 through an aperture 66 therein, the aperture 66 having an insulated plug 68 therein with suitable seals 70 for maintaining a fluid seal around the antenna 64. The antenna 64 is coax connected by means of a coax cable 72 to the receiver means generally indicated by reference character 26.

An ordinary microwave receiver may be used to receive the signal but since high frequency receivers are relatively expensive, lower cost components as indicated by the block diagram (FIG. 4) may be used to reduce the effective frequency of the signal without degrading the quality thereof. The receiver 26 generally comprises a doubly balanced mixer 74, one input of which is operably connected to the antenna 64 through the coax cable 72, a local oscillator 76 being operably connected to the other input of the doubly balanced mixer 74. The output of the mixer 74 may be either tha sum of the signal frequency from the bottom hole and the local oscillator frequency or may be the difference therebetween. By utilizing the difference output, a substantially reduced frequency may be utilized. The output of the mixer is then fed into an intermediate frequency (IF) amplifier 78 which in turn is operably connected to a detector 80. The output of the detector 80 is fed into a data processing unit for converting the data into a readable quantity which is proportional to either the pressure or temperature of the bottom hole reservoir fluid 14. This data processing unit may also be provided with a display means for displaying said temperature or pressure indication and/or may be provided with recording means for recording such information if the well head unit is not attended.

It is readily apparent that the microwave system or instrumentation unit at the bottom hole may be varied such as by the adoption of a clock (not shown) for periodically operating the transmitter system for conserving power in the power supply unit 46.

Referring now to FIGS. 5, 6, 7 and 8, FIG. 5 depicts an oil well bore which is substantially identical to that of FIG. 1 and for ease of description will carry the same reference character numbers as that in the description of the borehole of FIG. 1.

The data instrumentation unit of the embodiment described in FIGS. 5, 6, 7 and 8 may be substantially identical to that hereinbefore described and contains a power supply 46, pressure and temperature transducers 36 and 38, which have elements 40 and 42, respectively, exposed to the reservoir fluid 14. The electronics compartment 48 which is insulated by insulation material 50 also contains a data conversion means 82 for providing a modulation signal which is proportional to the pressure or temperature sensed by the transducers 36 and 38. The output of the data conversion means 82 is operably connected to the input of a laser means 84. The output of the laser is directed into one end of a fiber optic strand 86. The instrumentation compartment also is provided with a light sensitive or laser receiving means 88 which is likewise connected to the end of a fiber optic strand 90. The fiber optic strands 86 and 90 extend through the bottom hole unit attach means 24 and the insulation material 50.

Referring now to FIG. 7, the power supply 46 is operably connected to the data conversion means and to the receiver 88. The receiver 88 may comprise any well known photo sensitive device having a switching means 92 therein so that when a signal is received through the fiber optic strand 90 into the receiver 88, the switch 92 will close thereby providing power through the receiver to the laser 84. The laser 84 comprises a data input transistor Q3 and a diode laser D1. The base of the transistor Q3 is connected to the output of the data conversion means 82 and the collector thereof is connected to the power output of the receiver 88. The base of the transistor Q3 is operably connected to the input of the diode laser D1 whereby upon the receipt of a signal or serial data from the data conversion means 82, the transistor Q3 will saturate thereby applying power from the receiver means 88 through the said transistor Q3 to the diode laser D1. A collimating lens 94 is connected to the end of the fiber optic strand 86 so that the photo emission from the diode laser D1 is collimated to be directed into the fiber optic strand 86 for subsequent travel therealong to the well head.

Referring now to FIG. 8, reference character 96 indicates a well head laser which may consist of a laser diode similar to that used in the bottom hole instrumentation unit but which is used for sending a signal into the upper end of the fiber optic strand 90 to be directed to the bottom hole receiver means 88. The upper end of the fiber optic strand 90 extends through the pipe string 20 utilizing appropriate sealing means 92, the end of the said fiber optic strand being provided with a colliminator lens 98 for collimating the photo emission therefrom and directing said emission into the fiber optic strand 90. The well head instrumentation system is provided with a receiver 100 which comprises a photo sensitive switching transistor 102, the sensitivity of which is controlled by a resistor R2 and a potentiometer R3 which is connected to a negative output power supply (not shown). The output of the photo sensitive transistor switch 102 is operably connected to the emitter of a transistor Q4. The transistor Q4 has the base thereof connected to ground and the collector thereof operably connected to the positive output terminal power supply (not shown) and thereby acts as a current amplifier. The collector of the transistor Q4 is also connected into a preamplifier 104 through a capacitor C6. The output of the preamplifier 104 is then fed into a data processing unit 106 for processing the temperature and pressure data and reconverting the same back into a readable form which is proportional to the actual pressure and temperature of the fluid reservoir. The photo sensitive transistor switching means 102 of the receiver 100 is positioned in alignment with the upper end of the fiber optic strand for receiving the signal from the bottom hole laser 84. The fiber optic strand 86 is also passed through the pipe string 20 and is provided with a suitable sealing device 108.

In operation, when it is desirable to obtain pressure and temperature readings from the bottom hole indicator unit, the laser 96 is turned on and photo emission therefrom is transmitted through the fiber optic strand 90 to the bottom hole unit and into the receiver means 88 therein. So long as the photo emission is present at the receiver 88, the switch 92 thereof will be closed, thereby applying power to the laser means 84 therein. Information from the pressure and temperature transducers through the data conversion means is applied to the laser 84, thereby modulating the said signal or by creating coded pulses from the laser 84. The signal is transmitted through the fiber optic strand 86 to the well head where it is received by the receiver unit 100. There are obvious modifications apart from those shown herein, such as by utilizing a latching type switch in the receiver means 88 which would allow the keying signal and the data information signal to utilize the same fiber optic strand thereby eliminating one of the strands thereof.

Referring now to FIG. 9, reference character 110 generally indicates a pressure or temperature alarm system which may be located with the bottom hole instrumentation unit 22 for providing an alarm signal whenever the pressure or the temperature of the product reservoir 14 either becomes too high or too low. The alarm system 110 derives its power from the power source 46 and generally comprises a status limit means or voltage divider type transducer 112 which is substantially identical to and represents either the transducer 36 or the transducer 38 hereinbefore described. There will normally be two alarm systems 110, which are exactly identical and, hence, only one such system is described herein. Stated another way, the alarm system 110 may be a pressure alarm system and, if so, the transducer 112 would be one and the same transducer as that of 36 having the voltage divider pressure sensitive element 40 exposed to the reservoir 14.

The transducer 112 is connected across the power source 46 in parallel with a potentiometer R4 and a second potentiometer R5 is connected in parallel therewith. The output of the transducer 112 is connected to the positive terminal of an operational amplifier A1 and is likewise connected to the negative terminal of an operational amplifier A2. The output or wiper element of the potentiometer R4 is connected to the negative input terminal of the operational amplifier A1 and the output or wiper element of the potentiometer R5 is connected to the positive input terminal of the operational amplifier A2. A delay action relay 114 is connected to the power source 46 and a substantially identical delay action relay 116 is likewise connected to the power source 46. The output of the operational amplifier A1 acts as the actuator of the delay action relay 114 while the output of the operational amplifier A2 acts as the actuator for the delay action relay 116. The delay action relays 114 and 116 are for the purpose of conserving electrical power during the alarm phase of operation. The relays will energize the alarm generators 118 and 120 for a brief period and then lock out further transmission for another period. The delay time periods may be preselected by the user.

An upper limit alarm generator 118 is operably connected to the delay action relay 114 so that whenever a signal is applied from the delay action relay 114 to the high alarm generator thereby causing an alarm signal to be generated thereby. A lower limit alarm generator 120 is likewise connected to the delay action relay 116 so that power is applied thereto whenever an actuator signal is generated by the operational amplifier A2. The output of the high alarm generator 118 and the low alarm generator 120 are applied as inputs to a transmitter 122 which may constitute the microwave transmitter 54 of the first embodiment herein described or the laser transmitter 84 of the second embodiment herein described.

An example of operation for the alarm system 110, operational amplifiers A1 and A2 are selected which will provide a switching signal to the delay relays 114 and 116 only if the voltage at the negative input terminals thereof exceeds the voltage at the positive input terminals thereof. Under this theory of operation, the potentiometer R4 is set at a point which is representative of the highest reservoir pressure desired in the working well, so that the voltage drop across that portion of the potentiometer R4 between the positive output terminal of the power supply 46 and the wiper arm of the potentiometer R4 is always less than the potential drop across that respective portion of the resistive element of the transducer 112 so long as the pressure within the reservoir is less than the prescribed upper limit. When the pressure within the reservoir exceeds the upper limit, the wiper arm of the transducer 112 will move toward the positive power terminal thereof thereby reducing the voltage at the positive input terminal of the operational amplifier A1. When this pressure exceeds the upper limit, the voltage applied at the positive input of the operational amplifier A1 will be less than that at the negative input terminal thereof which will cause the amp. A1 to generate an output signal to the delayed relay mechanism 114 which will in turn after a predetermined delay, close the switch therein and apply power to the high alarm generator. This alarm generator will then key the transmitter 122 to send an alarm signal to the well head, either by microwave signal or by fiber optics, whichever embodiment is being used.

Likewise, the lowest desired pressure limit may be set into the potentiometer R5 so that so long as the pressure in the reservoir 114 is greater than the lower limit prescribed by the setting of the potentiometer R5 no signal will be produced from the operational amplifier A2. However, when the pressure of the reservoir 14 becomes too low, the voltage level at the negative input terminal of the operational amplifier A2 will become higher than the voltage present at the positive input terminal thereof which causes an actuator signal to be transmitted to the delay relay mechanism 116 thereby applying power to the low alarm generator, said alarm signal being transmitted by the transmitter 122 to the well head.

As hereinbefore stated, it is readily apparent that the same identical alarm circuit may be used for a temperature alarm system which could work in parallel with the system hereinbefore described and the alarm system could be easily connected to work with the microwave and laser measuring system hereinbefore described.

From the foregoing, it is apparent that the present invention provides a novel well bottom hole status system for measuring fluid reservoir pressure and temperature at the bottom of a well bore. This measuring system may also embody a unique alarm system for providing an alarm at the well head whenever the fluid reservoir exceeds the prescribed temperature or pressure levels.

Whereas, the present invention has been described with particular relation to the drawings attached hereto, it is readily apparent that other and further modifications apart from those shown or suggested herein, may be made within the spirit and scope of this invention.