Blowout-preventing gas collecting valve and method for recovering casing associated gas in shaft

Abstract

The invention provides a gas collecting valve and method for recovering casing associated gas in an oil well shaft and having blowout prevention capacity, one end of a central pipe is connected with an upper joint, the other end of the central pipe is connected with a lower joint, and a sliding sleeve is mounted on the outer wall of the central pipe; the annular metal framework is arranged on the lower connector in a sleeving mode and fixedly connected with the lower connector, and the leather cup is arranged on the annular metal framework. The leather cup clings to the inner wall of the sliding sleeve; the rubber surface of the leather cup and the metal surface of the inner wall of the sliding sleeve form an annular contraction sealing surface, and the upper and lower spaces of the sealing surface are respectively communicated with the exhaust port and the air inlet to form a differential pressure type control switch; a sealing ring is arranged at the joint of the sliding sleeve and the central pipe; a differential pressure type sliding switch is formed among the sliding sleeve, the center pipe and the sealing ring, and therefore the problems that a ground gas collecting valve is large in installation workload, prone to freezing and blocking in winter, short in service life, small in gas collecting amount, large in sealing point number, prone to oil gas leakage and high in safety and environmental protection risk are effectively solved.

Description

Technical Field

[0001] The invention belongs to a small downhole tool in an oil field, and relates to a gas collecting valve and a method for recovering casing associated gas in an oil well bore with the ability to prevent blowout. Background Art

[0002] At present, the recovery of associated gas at the wellhead of oil wells in China mainly adopts the process of laying gas collection pipelines on the ground and installing gas collection valves at the wellhead. The ground gas collection valve is installed on the oil collection manifold, and gas is drawn from the wellhead casing head to the gas inlet of the gas collection valve through a high-pressure hose quick connector. When the casing associated gas pressure is greater than the back pressure of the oil pipeline, the vent valve opens, and the associated gas enters the oil collection pipeline, and the oil and gas are mixed. The valve core of the gas collection valve mostly adopts a steel valve ball and valve seat structure. However, due to the low external ambient temperature in winter and the rapid release and heat absorption of associated gas, the ground gas collection pipeline often freezes and freezes, and the vent valve freezes and fails in winter. At the same time, the installation workload of the ground gas collection valve is large, and the aesthetics and standardization are not guaranteed. In addition, the ground gas collection pipeline process needs to be dismantled and installed during the well repair operation, and a large number of connection threads, sealing points, and the life of high-pressure hoses pose a risk of flammable gas leakage and safety and environmental protection hazards.

[0003] Downhole gas collecting valves are rarely used in China. Most of the core components of the gas collecting valves that have been used adopt an eccentric structure and use steel valve balls and valve seats similar to those of ground gas collecting valves. Due to the narrow space of the wellbore annulus, the gas collecting diameter is small, the gas collecting volume and reliability are poor, and they do not have anti-blowout performance when put into production, so they are rarely used. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention provides a gas collecting valve and method for recovering casing associated gas in the wellbore of an oil well with the ability to prevent blowouts, thereby effectively solving the problems of large installation workload of ground gas collecting valves, easy freezing and blockage in winter, short operating life, small gas collection volume, multiple sealing points that make oil and gas easy to leak, and high safety and environmental risks.

[0005] The present invention is achieved through the following technical solutions:

[0006] A blowout prevention gas collecting valve for recovering casing associated gas in a wellbore, comprising:

[0007] Upper joint, center tube, lower joint, sliding sleeve, annular metal frame and leather cup;

[0008] One end of the central tube is connected to the upper joint, the other end of the central tube is connected to the lower joint, and the sliding sleeve is installed on the outer wall of the central tube;

[0009] The annular metal frame is sleeved on the lower joint and fixedly connected with the lower joint. A sealing ring is provided at the connection between the annular metal frame and the lower joint. An exhaust port is provided on the central tube and communicates with the oil pipe to form an exhaust channel. The leather cup is provided on the annular metal frame to serve as the valve core of the anti-blowout gas collecting valve. An air inlet is provided at the connection between the annular metal frame and the sliding sleeve and communicates with the oil pipe to form an air inlet channel.

[0010] The leather cup is tightly attached to the inner wall of the sleeve; the rubber surface of the leather cup and the metal surface of the inner wall of the sleeve form an annular contraction sealing surface, and the upper and lower spaces of the sealing surface are respectively connected to the exhaust port and the air inlet, forming a pressure differential control switch;

[0011] The connection between the sliding sleeve and the central tube is provided with a first sealing ring and a second sealing ring; the sliding sleeve, the central tube, the exhaust port, the first sealing ring, the second sealing ring and the gap therebetween form a pressure differential sliding switch.

[0012] Preferably, the leather cup is processed by rubber vulcanization process at the end of the annular valve core metal skeleton to serve as the valve core of the anti-blowout gas collecting valve.

[0013] Preferably, the central tube is installed with a cap in a threaded manner near the upper joint and is locked with a locking screw.

[0014] Preferably, a locking ring is provided on the inner wall of the closure cap, and a locking buckle is provided on the upper part of the sliding sleeve. When the sliding sleeve is forced to slide into the closure cap, the locking buckle extends into the closure cap and engages with the locking ring to lock.

[0015] Preferably, the sleeve is in a closed state before the pump is put into production and locked with a shear pin; when the pressure difference of the pressure differential sliding switch reaches a certain value, the sleeve is forced to slide and shear the locked shear pin to move upward. After moving to the preset position, the sealing of the second sealing ring fails, and the air inlet channel of the gas collecting valve is opened.

[0016] Preferably, the locking ring, locking buckle, locking ring and shear pin are combined into a movable locking mechanism of the sliding sleeve.

[0017] Preferably, the first sealing ring is arranged close to the shear pin, and the second sealing ring is arranged close to the leather cup.

[0018] Preferably, the upper joint is connected to the oil pipe hanger via a thread, and the lower joint is connected to the oil pipe column via a thread; the center pipe is connected to the lower joint via a thread and a fourth sealing ring.

[0019] Preferably, the internal diameter of the valve body of the gas collecting valve is consistent with the inner diameter of the oil pipe and is in communication with each other.

[0020] Preferably, the annular metal frame is reliably fixed to the lower joint via threads and a third sealing ring.

[0021] A working method of a blowout prevention gas collecting valve for recovering casing associated gas in a wellbore, comprising:

[0022] After the gas collecting valve is lowered into the well, the wellhead casing is closed and the casing is vented. During the process of the casing annulus being pressurized and the associated gas pressure rising, the associated gas in the casing annulus exerts pressure on the sealing surface of the leather cup and the sleeve; when the associated gas pressure in the casing is greater than the internal pressure of the oil pipe of the gas collecting valve and the deformation stress of the leather cup, the leather cup contracts toward the center, opening the gas collection channel, and the associated gas enters the oil pipe from the exhaust port; when the associated gas pressure in the casing annulus decreases and is less than the internal pressure of the oil pipe and the deformation stress of the leather cup, the leather cup resumes the expansion state under the action of its own ductile physical and chemical properties, re-fits and seals with the inner wall of the sliding sleeve, closes the gas collection channel, and terminates the gas collection process, preventing the oil in the oil pipe from leaking into the casing annulus.

[0023] Compared with the prior art, the present invention has the following beneficial technical effects:

[0024] The invention discloses a gas collecting valve for recovering casing associated gas in the wellbore of an oil well and having the ability to prevent blowout. The cup valve core formed by vulcanized rubber on the annular metal skeleton has good contraction and deformation ability under external pressure, so that the valve core can be opened at a relatively low pressure. Through the action of the differential pressure control switch and the differential pressure sliding switch, when the associated gas in the casing annulus exerts pressure on the lower surface of the valve core cup, when the associated gas pressure in the casing is greater than the internal pressure of the oil pipe of the gas collecting valve and the deformation stress of the cup valve core, the cup contracts toward the center and separates from the inner surface of the sliding sleeve, opening the gas collecting channel, and the associated gas enters the oil pipe from the exhaust channel; when the associated gas pressure in the casing annulus decreases and is less than the internal pressure of the oil pipe and the deformation stress of the cup valve core, the cup restores the expansion state under the action of its own extension physical and chemical properties, re-seals with the inner wall of the sliding sleeve, and closes the gas collecting channel; the associated gas in the wellbore casing annulus enters the pressure holding recovery period, and the cycle process of the associated gas in the casing annulus, opening and releasing, and re-pressure holding is realized repeatedly. In addition, in view of the special situation that there may be oil spill and pressure at the wellhead during the commissioning of a new well, a differential pressure sliding sleeve switch is designed to meet the requirements of well control. The air inlet channel of the gas collecting valve is closed during the pumping operation of the new well. After normal production, the simple operation of closing the wellhead oil pipe gate to hold the pressure generates a casing pressure difference. When the pressure difference reaches the set value, the sliding sleeve moves to reopen the gas collecting valve inlet. Since the associated gas absorbs a lot of heat when it is quickly discharged from the high-pressure state to the low-pressure state, it is easy to cause low-temperature freezing. The situation is more serious when the gas volume is large and the throttling pressure difference is high. The high temperature in the wellbore of the oil well can inhibit the freezing of the gas collection process, extend the life of the gas collecting valve and improve the reliability of the gas collection process; effectively solve the problems of large installation workload of the ground gas collecting valve, easy freezing in winter, short operating life, small gas collection volume, many sealing points, easy oil and gas leakage, and high safety and environmental protection risks.

[0025] The present invention discloses a gas collecting valve for recovering casing associated gas in the wellbore of an oil well and having the ability to prevent blowouts. The working method is designed to recover the crude oil associated gas separated from the bottom of the well in the wellbore during the normal production process of the oil well, re-enter the oil collection process, and mix and transport it to the downstream site. The gas collecting valve meets the technical requirements of the strength, pressure bearing requirements, backflow prevention, blowout prevention of downhole tool accessories, and the minimum inner diameter, maximum outer diameter and service life of the oil wellbore for the tool. When the associated gas pressure in the casing annulus is higher than the back pressure pressure in the oil pipe to form a pressure difference, the gas collecting valve can work and recover the associated gas to the maximum extent. The present invention can better solve the leakage risks of ground gas collecting valves and gas collecting pipeline connections, the hidden dangers of freezing and blocking in winter, the construction difficulties of disassembling and assembling gas collecting pipelines in well repair operations, and the technical requirements of well control for new well production operations.

[0026] Furthermore, the rubber cup valve core is installed on the oil pipe hanging near the wellhead in the wellbore, changing the current common ground gas collection and recovery process mode of oil wellhead associated gas to the underground wellbore gas collection and recovery mode. Its core component, the rubber cup valve core, has the technical characteristics of corrosion resistance, large ventilation volume, high reliability of one-way flow sealing performance, and low opening pressure.

[0027] Furthermore, the present invention has a reasonable design, compact structure, high integration, small size, few sealing points, reliable sealing process and long service life. By changing the associated gas recovery process from the ground to the wellbore, the favorable conditions of the high temperature environment of the wellbore can be fully utilized, and the problem of valve body and pipeline freezing in the associated gas recovery process in winter can be better solved. At the same time, the annular metal skeleton leather cup valve core designed by drawing on the technical concept of the downhole leather cup packer has the characteristics of large gas collection flux, low starting pressure, corrosion resistance, anti-scaling and long service life. The pressure-controlled sliding sleeve valve designed specifically for the technical requirements of the pump down link to prevent blowout has a simple structure, reliable performance and low manufacturing cost, which can meet the daily production and operation well control needs of oil wells. Compared with the general ground gas collection valve, the present invention eliminates the complex ground gas collection pipeline, is installed with the inspection pump operation, has no additional installation costs and manual work workload, and is maintenance-free on a daily basis; has fewer wearing parts, and its service life can be increased by more than 2 times compared with the existing ground gas collection valve, and the gas collection capacity can be increased by 5-10 times, with good comprehensive economic performance, high technical superiority and high safety and environmental protection.

[0028] Furthermore, the gas collecting valve is designed with a pressure-controlled sleeve to prevent blowouts. Before the pump is put into production, the gas collecting valve is first closed mechanically, and the sleeve is reliably locked by a countersunk shear pin, the air inlet channel is closed, and the pressure transmission from the casing annulus to the oil pipe through the valve body is blocked. When the oil well is in normal production after the operation is completed, the pressure difference between the oil pipe and the casing annulus can be generated by closing the wellhead oil pipe gate to hold the pressure. When the pressure difference reaches a certain value, the pressure-controlled sleeve slides under force and cuts off the shear pin to move. After moving to the preset position, the sealing ring fails, the air inlet channel of the gas collecting valve is opened, and the sleeve slides until it is locked by the pre-set ring valve in the cap and cannot be retracted. At this time, the gas collecting valve enters a normal working state, realizing the anti-blowout function of the gas collecting valve during the operation of the new well. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The present invention is a schematic diagram of the structure of a blowout prevention gas collecting valve used for recovering casing associated gas in an oil field wellbore.

[0030] In the figure, 1. upper joint; 2. lower joint; 3. sliding sleeve; 4. cap; 5. center tube; 6. locking ring; 7. locking buckle; 8. annular metal frame; 9. leather cup; 10. air inlet; 11. exhaust port; 12. locking screw; 13. first sealing ring; 14. shear pin; 15. second sealing ring; 16. third sealing ring; 17. fourth sealing ring. DETAILED DESCRIPTION

[0031] The present invention is further described in detail below in conjunction with specific embodiments, which are intended to explain the present invention rather than to limit it.

[0032] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0033] The present invention provides a gas collecting valve used for recovering casing associated gas in the wellbore of an oil well and having the ability to prevent blowouts during the process of pumping down the wellbore after production. The main components include a gas collecting valve body and a blowout prevention pressure control sliding sleeve valve. The upper joint of the gas collecting valve is fixedly connected to the oil pipe hanger in the wellbore through a thread; the lower joint of the valve body is connected to the oil well production tubing string, and the overall inner and outer diameters meet the requirements of the wellbore and tubing string size of the oil well. The air inlet channel of the gas collecting valve is connected to the oil casing annulus, and the exhaust channel is connected to the oil pipe. The gas collecting valve is installed on the oil pipe hanger and in the annular space of the oil casing near the wellhead.

[0034] The core component of the present invention adopts a leather cup formed by vulcanized oil-resistant rubber with an annular metal skeleton as the valve core, and uses the pressure difference between the casing annulus and the oil pipe as the driving force. When the pressure of the casing associated gas is higher than the back pressure in the oil pipe, the exhaust valve opens, and the associated gas enters the oil pipe to form an oil-gas mixed fluid with the oil flow; when the pressure difference value decreases to a certain value, the exhaust valve closes, and the gas collection process is terminated to prevent the oil in the oil pipe from leaking into the casing annulus.

[0035] At the same time, in view of the special conditions of oil overflow and pressure at the wellhead during the commissioning of new wells, a blowout prevention mechanism is designed. During the commissioning of new wells, a blowout preventer is installed on the oil pipe string. Before the completion operation, the pressure transmission between the oil casing annulus and the oil pipe is closed. The oil pipe is connected to the atmosphere and is at normal pressure. At this time, the oil casing annulus is connected to the oil layer, and the oil and gas overflow to generate casing pressure. The gas collecting valve installed on the near-wellhead pipe string will open the gas collecting valve inlet and outlet channels under the pressure difference of the oil casing annulus, causing oil and gas leakage into the oil pipe, causing oil and gas leakage safety risks to the wellhead operation, and even a blowout accident, endangering the safe construction of the oil well.

[0036] Therefore, in response to this situation, a pressure-controlled anti-blowout sliding sleeve is designed on the gas-collecting valve. When the gas-collecting valve is put into production and lowered into the well, the gas-collecting valve is first closed mechanically, and the shear pin is used to reliably lock the sliding valve, close the air inlet channel, and seal the pressure transmission from the oil-casing annulus to the oil pipe through the gas-collecting valve body. When the operation is completed and the oil well is in normal production, the pressure difference between the oil pipe and the oil-casing annulus is generated by holding the pressure at the wellhead. When the pressure difference reaches a certain value, the anti-blowout sliding sleeve of the gas-collecting valve slides under force and cuts off the shear pin to move, the air inlet channel of the gas-collecting valve is opened, and the sliding sleeve slides until it is locked by the pre-set annular valve and cannot be retracted. At this time, the gas-collecting valve enters a normal working state.

[0037] like Figure 1As shown, it is vertically installed on the oil pipe hanging near the wellhead and in the annular space of the oil casing. The main body is connected to the oil pipe hanging thread in the wellbore through the upper joint 1; the valve body center pipe 5 is connected to the lower joint 2 through the thread and the sealing ring 13; the center pipe 5 is opened with an exhaust hole 11 connected to the oil pipe to form an exhaust channel; the valve body lower joint 2 is connected to the oil well production oil pipe string, and the overall inner and outer diameters meet the requirements of the oil wellbore and pipe string size. The air inlet 10 of the gas collecting valve is connected to the oil casing annulus. The leather cup 9 formed by vulcanized oil-resistant rubber of the annular metal skeleton 8 serves as the valve core of the gas collecting valve; the annular metal skeleton 8 is reliably fixed to the lower joint 2 by threads and the third sealing ring 16; the sleeve 3 is installed on the outer wall of the central tube 5 by two sets of first sealing rings 13 and second sealing rings 15, and the first sealing ring 13 plays a sealing and straightening role. The sleeve 3 is provided with a mechanical anchor and can slide upward relying on the central tube 5 under pressure; a cap 4 is installed in the form of threads on the outside of the central tube 5 near the upper joint 1 and is locked with a locking screw 12; a locking ring 6 is provided on the inner wall of the cap 4, and when the sleeve 3 is subjected to force When sliding into the cap 4, the upper lock buckle 7 of the sleeve 3 extends into the cap 4 and engages and locks with the lock ring 6 provided on the cap 4; the valve core of the leather cup 9 is processed by rubber vulcanization process at the end of the annular valve core metal frame 8, and the shape is like an open "trumpet", which is tightly attached to the inner wall of the sleeve 3 in an "interference" manner; the rubber surface of the leather cup 9 and the metal surface of the inner wall of the sleeve 3 produce an annular contraction sealing surface, and the upper and lower spaces of the sealing surface are respectively connected to the air inlet 10 and the exhaust port 11, forming a pressure differential opening and closing control switch; the sleeve 3 is in a closed state before the pump is put into production, and is locked by a countersunk shear pin 14. The sleeve 3, the center pipe 5, the exhaust port 11 and the two sets of first sealing rings 13 and second sealing rings 15 form a pressure-controlled sliding switch. When the pressure difference reaches a certain value, the sleeve 3 slides under force and cuts off the locking shear pin 14 to move upward. After moving to the preset position, the second sealing ring 15 fails to seal, and the air intake channel of the gas collecting valve is opened. The valve core of the gas collecting valve is a leather cup 9 formed by vulcanizing oil-resistant rubber with an annular metal skeleton 8. The shape is like an open "trumpet", which is tightly attached to the annular contraction sealing surface on the inner wall of the sliding sleeve 3 in an "interference" manner to form a differential pressure opening and closing check valve; different from the traditional metal valve ball check valve whose gas passage is in the center hole of the valve seat, the rubber surface of the leather cup 9 of the gas collecting valve and the metal surface of the inner wall of the sliding sleeve 3 that can slide generate an annular sealing surface as the gas passage.

[0038] The central tube 5 and the pressurized sliding sleeve 3 form a pressure-controlled sliding switch through two groups of four sealing rings, the first sealing ring 13 and the second sealing ring 15. The sliding sleeve 3 can slide upwards on the central tube 5 under pressure to open the air inlet 10 of the air collecting valve.

[0039] An anti-retraction lock buckle 7 is processed at the contact surface between the top of the sliding sleeve 3 and the cap 4; a locking ring 6 is designed inside the cap 4, and the lock buckle 7, the locking ring 6, and the shear pin 14 are combined to form a sliding sleeve 3 movement locking mechanism.

[0040] The associated gas is recovered by using the contraction and expansion of the rubber cup 9 valve core as an opening and closing switch. The associated gas in the casing annulus exerts pressure on the sealing surface of the cup 9 valve core and the sleeve 3. When the associated gas pressure in the casing is greater than the internal pressure of the gas collecting valve oil pipe and the deformation stress of the cup 9 valve core, the cup 9 contracts toward the center, opens the gas collection channel, and the associated gas enters the oil pipe from the exhaust port 11; when the associated gas pressure in the casing annulus decreases and is less than the internal pressure of the oil pipe and the deformation stress of the cup 9 valve core, the cup 9 restores the expansion state under the action of its own ductile physical and chemical properties, re-seals with the inner wall of the sleeve 3, closes the gas collection channel, and terminates the gas collection process to prevent the oil in the oil pipe from leaking into the casing annulus; the associated gas in the casing annulus of the wellbore enters the pressure holding recovery period, and the cycle process of the associated gas in the casing annulus is realized repeatedly, including the pressure holding, opening and releasing, and re-pressure holding.

[0041] Before the pump is put into production, the pressure-controlled sleeve 3 is first mechanically closed and reliably locked with the countersunk shear pin 14. At this time, the center pipe 5 and the sleeve 3 close the air inlet channel through two groups of four sealing rings, and the closed casing annulus transmits the pressure in the oil pipe through the gas collecting valve body. When the oil well is in normal production, the pressure difference between the oil pipe and the casing annulus can be generated by closing the wellhead tubing gate to hold the pressure. When the pressure difference reaches a certain value, the pressure-controlled sleeve 3 is forced to slide upward and cut off the shear pin 14 to move. After moving to the preset position, the sealing ring fails to seal, the air inlet channel of the gas collecting valve is opened, and the sleeve 3 slides until it is locked by the pre-set ring valve 6 in the cap 4 and cannot retreat. At this time, the gas collecting valve enters a normal working state, realizing the anti-blowout pressure control opening function of the gas collecting valve during the new well production operation;

[0042] The internal diameter of the leather cup valve core formed by the metal skeleton vulcanized rubber is consistent with the oil pipe, and the air passage is the annular inner contact surface of the rubber and the sleeve, which has the characteristics of large ventilation. The open "trumpet" leather cup installed in the "interference" mode fits the inner wall of the sleeve with a large area to form an annular surface seal, which has a large unidirectional ability to withstand the internal pressure of the oil pipe. When the internal pressure of the oil pipe acts on the upper surface of the leather cup valve core, the leather cup rubber is tightly attached to the metal inner wall surface. The higher the pressure, the tighter the seal between the leather cup valve core and the inner wall of the sleeve, and has good pressure bearing and single flow performance.

[0043] The cup valve core formed by the metal skeleton vulcanized rubber has good contraction and deformation ability under external pressure, and the valve core can be opened at a relatively low pressure. When the associated gas in the casing annulus exerts pressure on the lower surface of the valve core cup, when the associated gas pressure in the casing is greater than the internal pressure of the gas collecting valve oil pipe and the deformation stress of the cup valve core, the cup contracts toward the center and separates from the inner surface of the sleeve, opening the gas collecting channel, and the associated gas enters the oil pipe from the exhaust channel; when the associated gas pressure in the casing annulus decreases and is less than the internal pressure of the oil pipe and the deformation stress of the cup valve core, the cup restores the expansion state under the action of its own extension physical and chemical properties, re-seals with the inner wall of the sleeve, and closes the gas collecting channel; the associated gas in the wellbore casing annulus enters the pressure holding recovery period, and the cycle process of the associated gas in the casing annulus, pressure holding, opening and releasing, and re-pressure holding is realized repeatedly.

[0044] The leather cup valve core formed by the metal skeleton vulcanized rubber adopts oil-resistant and heat-resistant rubber, which can meet the daily production, hot washing and corrosion resistance requirements of oil wells and has a long service life.

[0045] The leather cup valve core is made of vulcanized rubber with a metal frame and has a strong pressure bearing capacity, and can meet the pressure bearing technical requirements of downhole tools in oil wells.

[0046] The gas collecting valve is designed with a blowout-proof pressure-controlled sliding sleeve valve. Before the pump is put into production, the gas collecting valve is first closed mechanically, and the sliding sleeve is reliably locked by a countersunk shear pin, the air inlet channel is closed, and the pressure transmission from the casing annulus to the oil pipe through the valve body is blocked. When the oil well is in normal production after the operation is completed, the pressure difference between the oil pipe and the casing annulus can be generated by closing the wellhead oil pipe gate to hold the pressure. When the pressure difference reaches a certain value, the pressure-controlled sliding sleeve is forced to slide and cut the shear pin to move. After moving to the preset position, the sealing ring fails, the air inlet channel of the gas collecting valve is opened, and the sliding sleeve slides until it is locked by the pre-set ring valve in the cap and cannot be retreated. At this time, the gas collecting valve enters a normal working state, realizing the blowout-proof function of the gas collecting valve during the operation of the new well.

[0047] Example 1

[0048] The present invention overcomes the risk of leakage between the ground gas collecting valve and the gas collecting pipeline, the hidden danger of freezing and blocking in winter, and the difficulty of disassembling and assembling the gas collecting pipeline during well repair, and at the same time solves the requirements for blowout prevention and well control when a new well is put into production. Figure 1The gas collecting valve and method shown are used for recovering casing associated gas in the wellbore of an oil well and meet the well control requirements and have the ability to prevent blowouts during the pumping operation after being put into production. The present invention simplifies the current common ground associated gas collection and recovery process, does not change the existing wellhead production facilities and ground gathering and transportation process technical specifications and management habits, installs an associated gas recovery gas collecting valve on the oil pipe hanger in the wellbore, and changes the common wellhead ground gas collection and recovery mode to an oil wellbore gas collection and recovery mode. The opening and closing of the gas collecting valve of the present invention adopts a pressure difference design; in order to obtain a large air flow and reliable anti-backflow performance, the traditional valve ball and valve seat single-flow mode is not adopted, and an annular metal skeleton leather cup valve core structure is designed, using the contraction and expansion of the rubber leather cup as the opening and closing switch, which has the advantages of large gas collection flux, low starting pressure, corrosion resistance, anti-scaling, and long service life.

[0049] A gas collecting valve used for recovering casing associated gas in the wellbore of an oil well and having the ability to prevent blowouts, comprising: a main body connected to a tubing hanger in the wellbore through an upper joint 1 with a threaded connection; a valve body center pipe 5 connected to a lower joint 2 through a threaded connection and a fourth sealing ring 17, and vertically installed on the tubing hanger close to the wellhead and in the annular space of the casing; an exhaust port 11 is opened in the center pipe 5 and communicates with the inside of the tubing to form an exhaust passage; and a valve body lower joint 2 is connected to the oil well production tubing string. The leather cup 9 formed by vulcanized oil-resistant rubber of the annular metal skeleton 8 is reliably fixed to the lower joint 2 through threads and the third sealing ring 16 as the valve core of the gas collecting valve; the sleeve 3 is installed on the outer wall of the central tube 5 through two groups of first sealing rings 13 and second sealing rings 15, and can slide upward relying on the central tube 5 under pressure; the upper joint 1 is installed with a cap 4 in the form of threads and locked with a locking screw 12; a locking ring 6 is arranged on the inner wall of the cap 4, and when the sleeve 3 is forced to slide into the cap 4, the locking buckle 7 on the sleeve 3 is engaged and locked with the locking ring 6 of the cap 4; the valve core of the leather cup 9 is shaped like an open "trumpet" and is tightly attached to the inner wall of the sleeve 3 in an "interference" manner; the upper and lower spaces of the sealing surface are respectively connected to the air inlet 10 and the exhaust port 11 to form a pressure differential opening and closing control switch; the sleeve 3 is in a closed state before the pump is put into production and is locked with a countersunk shear pin 14. When the oil-casing pressure difference reaches a certain value, the sleeve 3 slides under force and cuts off the locking shear pin 14 and moves upward. After moving to the preset position, the second sealing ring 15 fails to seal, and the air collecting valve intake channel is opened, entering a normal working state.

[0050] The present invention discloses a gas collecting valve capable of recovering casing associated gas in the wellbore of an oil well and having the ability to prevent blowouts. The gas collecting valve is designed to recover the crude oil associated gas separated from the bottom of the well in the wellbore during the normal production process of the oil well, re-enter the oil collecting process, and mix and transport it to the downstream site. The gas collecting valve meets the technical requirements of the strength, pressure bearing requirements, backflow prevention, blowout prevention of downhole tool accessories, and the minimum inner diameter, maximum outer diameter and service life of the oil wellbore for the tool. When the associated gas pressure in the casing annulus is higher than the back pressure in the oil pipe to form a pressure difference, the gas collecting valve can work and recover the associated gas to the maximum extent. The present invention can better solve the leakage risks of the ground vent valve and gas collecting pipeline connection, the hidden dangers of freezing and blocking in winter, the construction difficulties of disassembling and assembling the gas collecting pipeline in well repair operations, and the technical requirements of well control for new well production operations.

[0051] The working process of the gas collecting valve is as follows:

[0052] like Figure 1 As shown, after the gas collecting valve is lowered into the well, the wellhead casing venting process can be completely closed. During the process of the casing annulus holding pressure and the associated gas pressure rising in the casing, the associated gas in the casing annulus exerts pressure on the sealing surface of the leather cup 9 and the sliding sleeve 3. When the associated gas pressure in the casing is greater than the internal pressure of the oil pipe of the gas collecting valve and the deformation stress of the leather cup 9, the leather cup 9 shrinks toward the center, opens the gas collection channel, and the associated gas enters the oil pipe from the exhaust port 11; when the associated gas pressure in the casing annulus decreases and is less than the internal pressure of the oil pipe and the deformation stress of the leather cup 9, the leather cup 9 restores the expansion state under the action of its own ductile physical and chemical properties, and seals with the inner wall of the sliding sleeve 3 again, closes the gas collection channel, and the gas collection process is terminated to prevent the oil in the oil pipe from leaking into the casing annulus; the associated gas in the casing annulus of the wellbore enters the holding pressure recovery period, and the cycle process of holding pressure of the associated gas in the casing annulus, opening the discharge, and holding pressure again is realized repeatedly. The whole process is completed in the wellbore of the oil well, and there is no change in the surface process of the oil well. The gas collecting valve does not require any additional operation and maintenance during the entire working process.

[0053] The working process of the gas collecting valve blowout prevention mechanism is as follows:

[0054] like Figure 1 As shown, the anti-blowout pressure-controlled sliding sleeve valve, the gas collecting valve first mechanically closes the gas collecting valve air inlet 10 before the pump is put into production, and uses the countersunk shear pin 14 to reliably lock the sliding sleeve 3, closing the oil casing annulus to transmit the pressure in the oil pipe through the gas collecting valve body. When the oil well is in normal production after the operation is completed, the pressure difference between the oil pipe and the oil casing annulus can be generated by closing the wellhead oil pipe gate to hold the pressure. When the pressure difference reaches a certain value, the sliding sleeve 3 is forced to slide and cut the shear pin 14 and move upward. After moving to the preset position, the sealing ring fails, the gas collecting valve air inlet 10 is opened, and the sliding sleeve 3 continues to slide until the front lock buckle 7 enters the cap 4 and is locked by the lock ring 6, and cannot be retreated. At this time, the gas collecting valve enters a normal working state, realizing the anti-blowout function of the gas collecting valve during the operation of the new well.

[0055] It should be noted that when a component is referred to as being "fixed to" another component, it may be directly on the other component or there may be a central component. When a component is considered to be "connected to" another component, it may be directly connected to the other component or there may be a central component at the same time. When a component is considered to be "set on" another component, it may be directly set on the other component or there may be a central component at the same time.

[0056] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by technicians in the technical field of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all of the above descriptions of one or more related listed items, which are only preferred embodiments of the present invention and are not intended to limit the present invention in any form; any ordinary technician in this industry can smoothly implement the present invention as shown in the drawings of the specification and described above; however, any technician familiar with this profession, without departing from the scope of the technical solution of the present invention, makes some changes, modifications and equivalent changes made by using the technical content disclosed above, which are equivalent embodiments of the present invention; at the same time, any changes, modifications and evolutions of any equivalent changes made to the above embodiments based on the essential technology of the present invention are still within the protection scope of the technical solution of the present invention.

Claims

1. A blowout prevention gas collecting valve for recovering casing associated gas in a wellbore, characterized in that: include, An upper joint (1), a central tube (5), a lower joint (2), a sliding sleeve (3), an annular metal frame (8) and a leather cup (9); One end of the central tube (5) is connected to the upper joint (1), the other end of the central tube (5) is connected to the lower joint (2), and the sliding sleeve (3) is installed on the outer wall of the central tube (5); The annular metal frame (8) is sleeved on the lower joint (2) and fixedly connected to the lower joint (2); a plurality of exhaust ports (11) are provided on the central pipe (5) and are connected to the oil pipe to form an exhaust channel; The leather cup (9) is arranged on the annular metal frame (8) to serve as a valve core of the anti-blowout gas collecting valve; an air inlet (10) is arranged at the connection between the annular metal frame (8) and the sliding sleeve (3), and is communicated with the oil pipe to form an air inlet channel; The leather cup (9) is tightly attached to the inner wall of the sliding sleeve (3); the rubber surface of the leather cup (9) and the metal surface of the inner wall of the sliding sleeve (3) generate an annular contraction sealing surface, and the upper and lower spaces of the sealing surface are respectively connected to the exhaust port (11) and the air inlet (10), forming a pressure differential control switch; A first sealing ring (13) and a second sealing ring (15) are provided at the contact surface between the sliding sleeve (3) and the central tube (5); the sliding sleeve (3), the central tube (5), the exhaust port (11), the first sealing ring (13), the second sealing ring (15) and the gaps therebetween form a differential pressure sliding switch.

2. The anti-blowout gas collecting valve for recovering casing associated gas in a wellbore according to claim 1, characterized in that: The leather cup (9) is processed on the end of the annular metal frame (8) by a rubber vulcanization process.

3. The anti-blowout gas collecting valve for recovering casing associated gas in a wellbore according to claim 1, characterized in that: The central tube (5) is provided with a cap (4) in a threaded manner near the upper joint (1) and is locked with a locking screw (12).

4. A blowout prevention gas collecting valve for recovering casing associated gas in a wellbore according to claim 3, characterized in that: A locking ring (6) is arranged on the inner wall of the closure cap (4), and a locking buckle (7) is arranged on the upper part of the sliding sleeve (3). When the sliding sleeve (3) is forced to slide into the closure cap (4), the locking buckle (7) extends into the closure cap (4) and engages with the locking ring (6) to lock.

5. The anti-blowout gas collecting valve for recovering casing associated gas in a wellbore according to claim 4, characterized in that: The sliding sleeve (3) is in a closed state before the pump is put into production and locked by a shear pin (14); when the pressure difference of the pressure differential sliding switch reaches a certain value, the sliding sleeve (3) is forced to slide and shear off the locked shear pin (14) to move upward, and after moving to a preset position, the sealing of the second sealing ring (15) fails, and the air inlet channel of the air collecting valve is opened.

6. A blowout prevention gas collecting valve for recovering casing associated gas in a wellbore according to claim 5, characterized in that: The locking ring (6), the locking buckle (7), the locking ring (6) and the shear pin (14) are combined to form a movable locking mechanism of the sliding sleeve (3).

7. The anti-blowout gas collecting valve for recovering casing associated gas in a wellbore according to claim 5, characterized in that: The first sealing ring (13) is arranged close to the shear pin (14), and the second sealing ring (15) is arranged close to the leather cup (9).

8. The anti-blowout gas collecting valve for recovering casing associated gas in a wellbore according to claim 1, characterized in that: The upper joint (1) is connected to the oil pipe hanger via a thread, and the lower joint (2) is connected to the oil pipe column via a thread; the center pipe (5) is connected to the lower joint (2) via a thread and a fourth sealing ring (17).

9. The anti-blowout gas collecting valve for recovering casing associated gas in a wellbore according to claim 1, characterized in that: A third sealing ring (16) is provided at the connection between the annular metal frame (8) and the lower joint (2); the annular metal frame (8) is reliably fixed to the lower joint (2) via threads and the third sealing ring (16).

10. A method for operating a blowout prevention gas collection valve for recovering casing associated gas in a wellbore, based on the blowout prevention gas collection valve according to any one of claims 1 to 9, characterized in that: include, After the gas collecting valve is lowered into the well, the wellhead casing is closed to vent the process. During the process of the casing annulus being pressurized and the casing associated gas pressure rising, the associated gas in the casing annulus exerts pressure on the sealing surface of the leather cup (9) and the sleeve (3); when the associated gas pressure in the casing is greater than the pressure in the oil pipe of the gas collecting valve and the deformation stress of the leather cup (9), the leather cup (9) contracts toward the center, the gas collecting channel is opened, and the associated gas enters the oil pipe from the exhaust port (11); when the associated gas pressure in the casing annulus decreases and is less than the pressure in the oil pipe and the deformation stress of the leather cup (9), the leather cup (9) recovers the expansion state under the action of its own ductile physical and chemical properties, and is sealed with the inner wall of the sleeve (3) again, the gas collecting channel is closed, the gas collecting process is terminated, and the oil in the oil pipe is prevented from leaking into the casing annulus.

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