US3430696A - Shut-off control for an in-situ combustion production well - Google Patents

Description

March 4, 1969 w. w. CUMMINGS SHUT-OFF CONTROL FOR AN IN-SI TU COMBUSTION PRODUCTION WELL Filed Dec; 2, 1966 moGmEum o 92 93 mwh 02 I000 WAL TER W CUMMINGS ATTORNEY United States Patent 3,430,696 SHUT-(EFF CUNTROL FOR AN lN-SITU COMP-USTIQN PRDDUCTION WELL Walter W. Cummings, Bakersfield, Calih, assignor to Mobil ()il Corporation, a corporation of New York Filed Dec. 2, 1966, Ser. No. 598,848 US. Cl. 16653 2 Claims Int. Cl. E21!) 43/12, 43/24 ABSTRACT OF 'I'fl-IE DESCLOSURE This specification discloses the closing of a production well leading from a subterranean formation undergoing in-situ combustion for the recovery of a hydrocarbon from the formation upon the failure while the well is producing of a cooling water supply for maintaining the well at a desired temperature. A signal is created upon failure of the cooling Water supply. In response to the signal, steps are taken to close the product line from the well. Closing of the well may be effected after a predetermined time following the failure of the cooling water supply. If the cooling water supply is resumed during the predetermined time, the steps taken to close the Well are cancelled. Closing of the well may also be effected substantially immediately upon failure of the cooling water supply. If the cooling water supply is resumed within a predetermined time, steps may be taken to reopen the Well. Means for creating the signal include a switch responsive to pressure in the cooling water line and means for closing the well in response to the signal include a valve in the product line from the Well, a motor which controls the position of the valve, and timer means for operating the motor for a predetermined time after operation of the switch.

This invention relates to the production of hydrocarbons from a. subterranean formation by the procedure involving in-situ combustion and relates more particularly to a method and system for shutting off a production well from a subterranean formation undergoing in-situ combustion in the event of a failure of the supply of cooling water to the well.

Hydrocarbon liquid, more particularly oil, in many instances can be recovered from a subterranean formation through a Well penetrating the formation by utilizing the natural energy within the formation. However, as the natural energy within the formation declines, or where the natural energy originally is insufiicient to effect recovery of the hydrocarbon liquid, recovery methods involving addition of extrinsic energy to the formation can be employed. One of these methods, called the in-situ combustion method, involves supplying an oxidizing medium to the formation and effecting combustion in place within the formation or" a portion of the hydrocarbon liquid or of a carbonaceous residue formed from a portion of the hydrocarbon liquid. A combustion front migrates through the formation and the remainder of the hydrocarbon liquid, along with gaseous effluent, passes from the formation to a production well. The heat produced by the combustion reduces the viscosity of the hydrocarbon liquid and this, along with the increase in pressure within the formation, the driving force provided by the supply of the oxidizing medium, and the generation of steam from any water within the formation, effects recovery of a greater portion of the hydrocarbon liquid within the formation than would be obtained in the absence of the combustion method.

While the in-situ combustion method is effective from the standpoint of the additional recovery of hydrocarbon liquid obtained, it is not without its difficulties. One of 3,430,696 Patented Mar. 4, 1969 these arises from the high temperatures encountered in the wells. With supply of the oxidizing medium to the formation, and ignition of the hydrocarbon liquid or carbonaceous residue, a combustion zone is created within the formation. This combustion zone will have a temperature between 600 F. and 1200 F. and can be even higher. In the indirect combustion method, where the oxidizing medium is supplied to the formation through an injection well and ignition is eifected in the formation at a production well, the combustion zone migrates from the production well to the injection well. As a result of the creation of the combustion zone in the formation at the production well, the production well immediately becomes hot and approaches the temperature of the combustion front. However, with migration of the combustion front to the injection well, the temperature at the production Well can decrease. In the direct combustion process, where the oxidizing medium is also supplied to the formation through an injection well but ignition is effected at the injection well rather than at a production well, the combustion zone migrates from the injection well to a production well. With the eventual approach of the combustion zone to the production well, the production well becomes hot and approaches the temperature of the combustion front.

With the production well becoming hot, various deleterious results are encountered. For example, the temperatures may become so high as to effect destruction of the liner, tubing, and other equipment in the well with possible consequent loss of the well. Further, where bypassing of the combustion zone by a portion of the oxidizing medium occurs, which is quite common, combustion within the well of the hydrocarbons, both liquid and gas, produced from the formation ensues with resulting loss of these hydrocarbons along with the attainment of still higher temperatures which practically insure destruction of the Well.

In order to avoid the difficulties arising from the high temperatures encountered in the production wells in the in-situ combustion process, cooling water is introduced into these wells. The cooling water is effective from the standpoint of preventing combustion and maintaining a desired low temperature in the Wells. However, in the operation of production wells with introduction of cooling water, the danger always exists of combustion of the hydrocarbons and attainment of high temperatures destructive to the well equipment upon failure of the cooling water supply for any significant period of time during which the Wells are producing.

It is an object of this invention to provide a system for preventing combustion of hydrocarbons and attainment of high temperatures destructive to well equipment upon failure of the cooling Water supply for any significant period of time to a production well leading to a formation undergoing in-situ combustion while the well is producing.

This and other objects of the invention will 'become apparent from the following detailed description.

Summary 0' the invention In accordance with the invention, there is provided a system in which a signal is developed upon a failure of the cooling water supply to a production well leading to a subterranean formation undergoing in-situ com-bustion while the well is producing. In response to the signal, steps are initiated to close the well. These steps may be to close the well after a predetermined period of time following failure of the cooling water supply, which predetermined period of time is not significant from the standpoint of combustion of the hydrocarbons and attainment of high temperatures destructive to the well equipment. These steps may also be to close the well substan tially immediately upon failure of the cooling water supply. In a specific embodiment of the invention, where the steps initiated are to close the well after a predetermined period of time following failure of the cooling water supply, steps may be taken to cancel the steps previously initiated to close the well in the event the cooling water supply is resumed within the predetermined period of time. In still another embodiment of the invention, where the steps initiated are to close the well substantially immediately upon failure of the cooling water supply, steps may be taken to reopen the well in the event the cooling water supply is resumed within a predetermined period of time following its failure.

In a specific embodiment of the invention, the signal is developed when the pressure within a line supplying cooling water to a production well leading to a subterranean formation undergoing in-situ combustion drops as a result of failure of the cooling water supply while the well is producing. The signal developed is then employed to initiate steps to close the product line leading from the well which conveys the gaseous and liquid efiluent produced from the formation undergoing in-situ combustion to a gas and oil separator or otherwise to gathering or storage. These steps include control of the operation of a motor which in turn operates a valve in the product line.

Brief description of the drawing The single figure is a schematic illustration of one embodiment of the invention.

Description of specific embodiments Reference will now be had to the figure which illustrates a specific embodiment of the invention, Well leads to the surface of the earth 11 from formation 12. The well 10 is provided with casing 13 and with production tubing 14. The production tubing 14 extends to a point near the bottom of the well. The well is also provided with line 15.

Well 10 is a production well. It will be assumed, for purposes of description, that the formation 12 is undergoing in-situ combustion by the direct combustion method for the recovery of hydrocarbons from the formation. In this method, the combustion front migrates through the formation 12 from an injection well (not shown) to the well 10 and gaseous and liquid hydrocarbons displaced from the formation by the combustion procedure, along with combustion products and unused oxidizing medium, enter the well through perforations (not shown) in the casing 13. These materials pass upwardly through the well through the production tubing 14. The arrows indicate the direction of fiow of materials from the formation into the well and into the production tubing.

Production tubing 14 is connected to product, or gathering, line which leads to gas and oil separator 21. Gas and oil separator 21 is preferably a ball trap. In this type of separator, the gas and liquid efiluent from the Well passing through the product line 20 enters the separator at a point substantially midway between the top and bottom portions. The gases separate from the liquids in the separator and the gases pass from the separator through line 22 leading from the upper portion of the separator to an exhaust stack (not shown) while the liquids pass from the separator through line 23 from the bottom portion of the separator to storage. The liquids leaving the separator 21 through the line 23 will contain water in addition to hydrocarbons and the water can be separated from the hydrocarbons upon leaving the separator.

Cooling water is provided to well 10 through the line 15. The line 15 is connected to a tank 24 or other reservoir of cooling water. The cooling water in tank 24 may be partly, or entirely, water separated from the hydrocarbons upon leaving the separator 21, and treated,

if necessary. The line 15 is provided with pump 25 which serves to pump the water from the tank 24 to the well. The water entering the well through the line 15 mingles with the gases and liquids entering the well from the formation 12. The water being introduced into the well in sufiicient amount and mingling with the gases and liquids cools them to a point below their ignition temperature to prevent combustion in the well and below a temperature to prevent destruction of the casing and other equipment that may be in the well. While the line 15 is shown as being provided with a pump, the pump may not be required where other means for effecting flow of cooling water through the line 15 may be available. For example, the pump may not be required where the tank 24 is sufiiciently high in elevation with respect to the well it) that a satisfactory rate of flow of the cooling water may be effected by gravity. The pump may be electrically operated or may be operated by other means such as steam or an internal combustion engine.

The line 20 is provided with shut-off valve 30. The valve controls the fiow of gas and liquid efiluent from the well in line 20 and closing of valve imposes a back pressure on the well which prevents gas and liquid from entering the well from formation 12. With gas and liquid no longer entering the well upon closure of valve 30, combustion within the well and the attainment otherwise of destructively high temperatures do not occur. The well thus will have attained a static condition.

Upon failure of the cooling water Supply to well 10 while the well is on production, valve 30 closes within a predetermined period of time or substantially immediately thereafter. Failure of the cooling water supply may arise from various causes. For example, the pump 25 may cease operation as a result of a power failure or mechanical ditficulty. Further, the tank 24 may become exhausted of cooling water. Alternatively, a leak or an obstruction may occur in the line 15 between the tank and the well to prevent the cooling water from entering the well.

Switch 31 is connected by means of pipeline 32 to water line 15. The switch 31 is a pressure operated switch and operates in response to a decrease in pressure imposed upon the switch through the line 32. For example, the switch may be provided with a diaphragm whose position is dependent upon the pressure imposed upon the diaphragm. With decrease in the pressure, the position of the diaphragm will change and the change will effect the breaking of an electrical circuit. Upon a cessation of flow of water through the line 15 to the well 10, the pressure of the water in the line 15 will decrease and this decrease in pressure will be transmitted through the line 32 to the switch.

Switch 31 is connected electrically to timer 33 and motor 34. The timer 33 comprises a cylinder 34a and a piston 35. The piston 35 is composed of a material which is electrically conducting and electromagnetic. The cylinder 34a is provided with a metering jet 36. It is also provided with a spring 37 which is connected to the piston 35. In the position of the piston as shown, the spring 37 is under tension and serves to maintain a force upon the piston to pull it to the bottom portion of the cylinder.

The switch 31, timer 33, and motor 34 are connected to a source 38 of electrical current. The current flows from the source 38 through line 39 to contact 40. The contact 40 is positioned interiorly of the cylinder 34a and touches piston 35. Contact 41 is also positioned interiorly of the cylinder 34a and touches piston 35. The piston 35 being composed of electrically conducting material and the contacts 40 and 41 touching the piston, current can flow through the piston from the contact 40 to the contact 41. Line 42 is connected to the contact 41 and leads through switch 43 to motor 34. Line 44 connected to the motor 34 leads to ground. Thus, with the piston in the position shown, electrical current is supplied to the motor 34.

The electrical current supplied to the motor 34 serves to operate the motor and operation of the motor keeps valve 30 in line open. The motor 34 operating through any suitable mechanism such as a mechanical or fluid clutch, or hydraulic means, imposes a turning moment on arm 51 to maintain the arm in its position as shown. The arm 51 is connected through pivot joint 52 to arm 53 and the arm 53 is connected through pivot joint 54 with arm 55. Valve 30, as illustrated, is a butterfly valve having a flapper 59. The arm 55 is rigidly connected to the flapper 59 of valve and with continued operation of the motor, the arms 51, 53, and 55 maintain their positions as shown and the flapper 59 of the valve 30 remains in its position as shown keeping the valve open. Spring 60 is connected to arm 51 and in the position of arm 51 as shown the spring is in tension and opposes the turning moment on the arm applied to the motor. With the valve 30 continuing to be open, the Well 10 is also open and effluent from the well continues to pass through the line 20 to the seperator 21.

Line 61 is connected to the line 42 and leads to the switch 31. Line 62 leads from the switch 31 to coil 63 positioned about the upper portion of cylinder 34a. Line 64 is connected to the other end of the coil 63 and leads through switch 65 to line 44 and thus to ground.

With maintenance of the cooling water supply to the well 10, switch 31 will remain closed. With the switch 31 closed, current can flow from the source 38 through the line 39, through the piston between the contacts and 41 to the line 42, through the line 61 via the switch 31 to the line 62, through the coil 63 and thence through the line 64 and switch 65 to ground through line 44. The coil 63 acts as a solenoid and with current flowing through it maintains the piston 35, which is electromagnetic, in its position as shown in the upper portion of the cylinder.

Steps will now be described to close the well after a predetermined period of time following failure of the cooling water supply. Upon failure of the cooling water supply to the well 10, the pressure in line 15, as previously mentioned, decreases and the decrease in pressure is transmitted through the line 32 to the switch 31. With this decrease in pressure, the switch 31 is opened whereby current no longer flows from the line 61 through the switch 31 to the line 62, through the piston 35 and the coil 63 to the line 64, and through the switch 65 to ground through line 44. With the current no longer flowing through the coil 63, there is no force holding the piston in the upper portion of the cylinder and, because of the tension of the spring 37, the piston is pulled downwardly through the cylinder.

The lower portion of the cylinder 34a will be filled with air and the rate at which the piston Will be pulled downwardly through the cylinder will depend upon the rate at which the air can leave the cylinder through the metering jet 36. Thus, by adjustment of the metering jet, the time that will be required for the piston to be pulled to the bottom portion of the cylinder can be controlled. When the piston has been pulled to the bottom portion of the cylinder, the cylinder will no longer provide a flow path for electrical current between the contacts 40 and 41 and when this occurs current is no longer supplied to the motor 34. However, during the time that the piston is moving downwardly through the cylinder, the flow path for electrical current is maintained and the motor continues to operate until the piston has moved sufficiently down in the cylinder to break the flow path. Accordingly, the time that the motor 34 will operate after the supply of cooling water has failed is controlled by the timer 33.

Upon the motor 34 shutting oif, the turning moment on arm 51 is no longer applied. With the turning moment no longer being applied on the arm 51, the spring pulls the arm in a clockwise direction and maintains it in a position clockwise to that shown. Movement of the arm 51 in a clockwise direction moves the arm 55 in a counterclockwise direction and this moves the flapper 59 in the same direction to close the valve. Accordingly, the well will remain open for a predetermined time after the supply of cooling water has failed and this predetermined time is controlled by the timer 33.

In accordance with a specific embodiment of the invention, as mentioned previously, in the event that the cooling water supply is reinstated within the predetermined period of time following its failure, steps are taken to keep the well open. Where the cooling water supply is reinstated prior to the time that the timer times out, i.e., before the piston is moved down within the cylinder to break the connection between the contacts 40 and 41, the motor 34 is not shut off and the well remains open. Upon reinstatement of the water supply, the switch 31 is closed and current flows through the coil 63 to pull the piston 35 back to the upper portion of the cylinder. Thus, the motor remains in operation and the well does not close.

If the cooling water supply is reinstated after the timer times out, the motor will not start again to open the valve since the electrical connection between the contacts 4t) and 41 will have been broken. The motor, however, can be started manually with the piston at the bottom portion of the cylinder after the switch 31 has been closed. Line containing manual switch 71 is connected between lines 39 and 42 and upon closing of switch 71 current will flow through line 61, the switch 31, and the line 62 through the coil 63 to bring the piston to the upper portion of the cylinder and restore the connection between the contacts 40 and 41. When the piston reaches the upper portion of the cylinder, the switch 71 is manually opened.

As mentioned, the metering jet 36 can be set so that the time that will be required for the piston to be pulled to the bottom portion of the cylinder can be controlled. Since this time is the time required before the valve 30 is closed, the time that the valve 30 will remain open for any desired period of time after the supply of cooling water has failed can be controlled. This time will be the time that the well 10 may continue to produce after failure of the supply of cooling water without, to B significant extent, combustion of hydrocarbons or attainment of high temperatures destructive to the well equipment. Ordinarily, this time should not be more than about three minutes.

In accordance with another embodiment of the invention, steps can be taken to close the well 10 substantially immediately upon failure of the cooling water supply. Line 72 provided with switch 73 is connected between line 64 and line 42. With closing of switch 73 and opening of switches 43 and 65, motor 34 is placed in series with switch 31 and coil 63. Thus, with opening of switch 31 upon failure of the cooling water supply, the motor 34 stops and the valve 30 closes within the time required for the switch 31 to open, the motor 34 to stop, and the spring 60 to pull the arm 51, and the arms 53 and 55, to the position in which the valve is closed.

In accordance with still another specific embodiment of the invention, with the well being closed substantially immediately upon failure of the cooling water supply, steps are taken to reopen the well if the cooling water supply is reinstated within a predetermined period of time. Upon opening of switch 31, the supply of electrical current through the coil 63 is discontinued and the piston 35 begins to move downwardly through the cylinder 34a. If the cooling water supply is reinstated before the piston 35 moves sufficiently downwardly within the cylinder 34a to break the electrical connection between contacts 40 and 41, closing of switch 31 will supply current from line 39 through the piston between the contacts 40 and 41, the line 42 to the line 61 and the switch 31. From the switch 31, the current will flow through the line 62,

the coil 63, the line 64, and the line 72 and the switch 73 to the motor 34. With supply of current to the motor 34, the motor will begin operation and the valve 30 will open. If the cooling water supply is reinstated after the piston 35 moves sufficiently downwardly within the cylinder 34a to break the electrical connection between contacts 40 and 41, reinstatement of the cooling water supply and closing of switch 31 will not result in operation of the motor 34 and opening of valve 30. However, in this event, the motor can be started by operation of manual switch 71 as previously described.

The predetermined period of time following failure of the cooling water supply during which the well may be opened if the cooling water supply is reinstated can be controlled by the metering jet 36 as described above for the time that the well will remain open following failure of the cooling water supply. The failure of the cooling water supply may be only temporary. If the failure is only of short duration, for example, not more than about three minutes, the well may be considered to be safely 1 opened upon resumption of the cooling water supply. However, where the failure is of longer duration, it may be preferred that the well remain closed until an inspection of the system can be made.

The invention may be employed in connection with the production of hydrocarbons by in-situ combustion from any type of subterranean formation. Thus, the invention may be employed in connection with the in-situ combustion for the production of petroleum. Further, the invention may be employed in connection with the production of hydrocarbon material by combustion within a shale oil formation or within a tar sand.

Having thus described my invention, it will be understood that such description has been given by way of illustration and example and not by way of limitation, reference for the latter purpose being had to the appended claims.

I claim:

1. A system for closing a production well leading from a subterranean formation undergoing in-situ combustion for recovery of a hydrocarbon therefrom through a product line upon a failure while said well is producing of a cooling water supply provided to said well for maintaining said well at a desired temperature comprising:

means for creating a signal upon failure of said cooling water supply to said W611 including a switch responsive to pressure in said cooling water line, and means for elfecting closing of said well in response to said signal including a valve in said product line, a motor which controls the position of said valve and whose operation is controlled by said switch, and

timer means for operating said motor for a predetermined time after said switch has operated to stop said motor. 2. A system for closing a production well leading from a subterranean formation undergoing in-situ combustion for recovery of a hydrocarbon therefrom through a product line upon a failure while said well is producing of a cooling water supply provided to said well through a cooling Water line for maintaining said well at a desired temperature comprising:

means for creating a signal upon failure of said cooling water supply to said well including a pressure switch responsive to the pressure of cooling water in said cooling water line, means for effecting closing of said well in response to said signal including timer means and valve means in said product line operated by a motor, and switching means,

said timer means including means operative through said switching means:

to close said valve means substantially immediately upon failure of said cooling water supply, and alternatively, within a predetermined time after failure of said cooling water supply, to open said valve means after reinstatement of said cooling water supply Within a predetermined time following closing substantially immediately upon failure of said cooling Water supply, and to keep open said valve means after reinstatement of said cooling water supply within said first mentioned predetermined time.

References Cited UNITED STATES PATENTS 2,718,218 9/1955 Gray 122-504 X 3,240,270 3/1966 Marx 166-4 3,357,490 12/1967 Holmes 166-53 OTHER REFERENCES McNeil, James S., et al.: Oil Recovery by In-Situ Combustion, in the Petroleum Engineer, July 1958, pp. B-29 to 13-32, B-36, B-4l and B42.

JAMES A. LEPPINK, Primary Examiner.

IAN A. CALVERT, Assistant Examiner.

- US. Cl. X.R. 166-65, 256, 302

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