A heat-washable backflow-preventing gas collection device and method for recovering casing gas within a wellbore

Abstract

This invention discloses a heat-washable anti-backflow gas gathering device and method for recovering casing gas in wellbore. Utilizing the pressure difference between the casing annulus and the tubing, when the associated gas pressure in the casing is higher than the back pressure in the tubing, the anti-backflow gas gathering check valve opens, allowing the associated gas to enter the tubing and form an oil-gas mixture. When the pressure difference decreases to a certain value, the anti-backflow gas gathering check valve closes, terminating the gas gathering process and preventing oil leakage from the tubing into the casing annulus. During heat washing, as the temperature of the heat washing fluid rises to the required level, paraffin wax expands from a solid to a liquid state, pushing the piston-integrated temperature control valve core to a two-way acting ball seat, closing the gas gathering channel connecting the device to the tubing. When the heat washing operation ends and the casing annulus temperature decreases, the paraffin wax shrinks from a liquid to a solid state. Under the pushing action of the return spring, the piston-integrated valve core of the device leaves the two-way acting valve seat, reopening the gas gathering channel connecting the device to the tubing.

Description

Technical Field

[0001] This invention belongs to the technical field of small tools and equipment for oilfield wells, and relates to a heat-washable anti-backflow gas collection device and method for recovering casing gas in the wellbore. Background Technology

[0002] Currently, associated gas recovery at oil wellheads mainly involves laying gas gathering pipelines for distribution and controlling the flow of associated gas from the wellhead through surface gas gathering valves, allowing for mixed transport of oil and gas in surface oil gathering pipelines. The vent valve is installed on the oil gathering manifold, and gas is drawn from the wellhead casing head to the inlet via a high-pressure hose quick connector. When the associated gas pressure in the casing exceeds the back pressure of the oil pipeline, the vent valve opens, allowing the associated gas to enter the oil gathering pipeline for mixed transport. However, due to low ambient temperatures in winter and the rapid heat absorption during associated gas release, problems frequently arise in winter, such as condensation blockage in the surface gas gathering pipeline, freezing of the vent valve valve, and valve failure. Although some specialized vent valves have been designed with measures such as using the transported oil temperature for "oil bath" heating and insulation, incorporating defrosting mechanisms, increasing the diameter of the inlet pipeline, and forcing a slope in the surface gas gathering pipeline installation to prevent liquid accumulation, the effectiveness has been minimal. Furthermore, due to the variations in wellhead processes, the installation of vent valves is labor-intensive, and aesthetics and standardization cannot be guaranteed. In addition, well workover operations require the removal and installation of surface gas collection pipelines, and the large number of connecting threads, sealing points, and high-pressure hoses pose risks of flammable gas leakage and safety and environmental hazards. Summary of the Invention

[0003] The purpose of this invention is to solve the problems of easy freezing and blockage in winter and the large workload of disassembling and assembling gas collection processes during well repair operations in the existing technology, which makes gas collection difficult. The invention provides a heat-washable anti-backflow gas collection device and method for recovering casing gas in the wellbore.

[0004] To achieve the above objectives, the present invention employs the following technical solution:

[0005] This invention proposes a heat-washable anti-backflow gas collecting device for recovering casing gas in a wellbore, comprising a gas collecting body vertically installed below an eccentric fixing device; an exhaust channel is provided on the upper part of the gas collecting body, a bidirectional action ball seat is embedded in the inner wall of the gas collecting body, an anti-backflow one-way valve ball is provided above the bidirectional action ball seat, a back pressure spring is vertically installed between the upper part of the anti-backflow one-way valve ball and the inner wall of the gas collecting body, the one-way valve ball, the bidirectional action ball seat and the back pressure spring constitute an anti-backflow gas collecting one-way valve, and an air inlet channel is provided on the side of the gas collecting body.

[0006] Preferably, it further includes a valve core working cylinder and a temperature control valve core. The valve core working cylinder is embedded below the inner wall of the gas collecting body. A plug is installed on the bottom surface of the valve core working cylinder. The interior of the valve core working cylinder is filled with heat-sensitive paraffin. A piston is provided on the lower end face of the valve stem of the temperature control valve core to form a piston-integrated temperature control valve core. The piston-integrated temperature control valve core is press-fitted into the valve core working cylinder and can move up and down reciprocally within the valve core working cylinder.

[0007] The valve stem of the temperature control valve core is provided with an annular centering limit block. The annular valve core centering limit block is located at the lower edge of the air intake channel and is fixed to the valve core working cylinder. A return spring is provided between the piston and the annular centering limit block. The valve core working cylinder, the piston integrated temperature control valve core, and the bidirectional ball seat constitute a temperature control switch.

[0008] Preferably, a rubber insulating layer is provided on the lower end face of the piston.

[0009] Preferably, a telescopic cylinder is installed between the lower end face of the valve stem of the temperature control valve core and the piston, one end of the telescopic cylinder is fixedly connected to the piston, and the other end of the telescopic cylinder is connected to the valve stem of the temperature control valve core.

[0010] Preferably, the inner wall of the annular straightening limiting block is provided with a central hole, and a sealing ring I is provided in the central hole to contact the valve stem of the temperature control valve core.

[0011] Preferably, a sealing ring II is provided between the outer wall surface of the piston of the temperature control valve core and the inner wall surface of the valve core working cylinder.

[0012] Preferably, the lower end of the irregularly shaped valve core working cylinder is flared.

[0013] Preferably, an upper connector is installed between the eccentric fixing device and the gas collecting body, and the upper connector is connected to the eccentric fixing device by threads.

[0014] Preferably, there are at least two air intake channels.

[0015] The present invention proposes a method for a heat-washable anti-backflow gas collection device for recovering casing gas in a wellbore, comprising the following steps:

[0016] Gas is introduced into the gas collecting body through the air intake channel. When the gas pressure in the gas collecting body is greater than the gas pressure in the eccentric fixed device, the anti-backflow single-flow valve ball moves upward and opens. The introduced gas enters the oil pipe of the eccentric fixed device through the exhaust channel, realizing the closed recovery process of associated gas in the wellbore.

[0017] When the gas pressure in the gas collecting body is less than the gas pressure in the eccentric fixed device, the anti-backflow single-flow valve ball moves down to the bidirectional action ball seat, and the gas in the eccentric fixed device resumes the pressure-holding period, thus repeatedly realizing the cycle of pressure-holding, opening and releasing, and pressure-holding again in the annular space of the casing.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] This invention proposes a heat-washable anti-backflow gas gathering device for recovering associated gas in the wellbore. It eliminates the need for surface associated gas gathering and recovery process pipelines, and does not change the existing wellhead production facilities, surface gathering and transportation process technical specifications and management habits. A heat-washable well pressure differential type anti-backflow associated gas gathering device is added to the oil pipe near the wellhead in the wellbore through an eccentric fixing device, changing the surface gas gathering and recovery process mode of oil wellhead associated gas to the downhole wellbore gas gathering and recovery mode. By setting up an inlet and an outlet channel, gas can be injected into the gas gathering body through the inlet channel. When the pressure of the injected gas is greater than the pressure at the eccentric fixing device, the anti-backflow check valve ball moves upward and opens, and the introduced gas enters the tubing of the eccentric fixing device through the outlet channel, realizing the closed recovery process of associated gas in the wellbore. When the gas pressure in the gas gathering body is less than the pressure inside the eccentric fixing device, the anti-backflow check valve ball moves downward to the bidirectional action ball seat under the action of the back pressure spring, and the gas inside the eccentric fixing device returns to the pressure-holding period. This cycle of pressure-holding, opening and releasing, and re-pressure-holding of associated gas in the casing annulus is repeated. It can be seen that the gas gathering device proposed in this invention has a simple structure and is convenient for gas gathering.

[0020] Furthermore, the valve core working cylinder is filled with heat-sensitive paraffin wax. The integrated piston temperature control valve core uses heat-sensitive paraffin wax as the core driving control material for temperature control, enabling automatic temperature control to open and close the gas gathering channel, supporting the function of reverse circulation hot washing oil wells. The valve core working cylinder, temperature control valve core, and bidirectional ball seat constitute a temperature control switch, which can temporarily close the gas gathering channel and block the connection between the oil casing annulus and the tubing as the temperature changes.

[0021] Furthermore, the annular valve core centering limit block is located at the lower edge of the intake channel to prevent impurities from accumulating.

[0022] Furthermore, a rubber isolation layer is provided to isolate heat-sensitive paraffin wax, and to clean the inner wall of the valve core working cylinder as it moves with the temperature control valve core.

[0023] Furthermore, the installation of a telescopic cylinder can control the relative sliding displacement distance between the piston and the temperature control valve core in the longitudinal direction, as well as the sealing force between the temperature control valve core and the lower seat cover of the double-acting ball seat. This ensures effective sealing of the temperature control valve core while preventing excessive piston stroke displacement from causing deformation and damage to the valve stem of the temperature control valve core.

[0024] Furthermore, installing sealing rings I and II ensures good airtightness.

[0025] Furthermore, the lower end of the valve core working cylinder is flared, which can expand the volume expansion range of the heat-sensitive paraffin when it changes from solid to liquid, and increase the effective longitudinal movement stroke of the integrated temperature control valve core that drives the piston in the valve core working cylinder.

[0026] Furthermore, there are at least two air intake channels to ensure that the gas is smoothly introduced into the gas collection body and to prevent the air intake channels from becoming blocked.

[0027] This invention proposes a gas collection method for a heat-washable anti-backflow gas collection device for recovering associated gas inside a wellbore. The gas is introduced into the gas collection body through the gas inlet channel, and the associated gas is recovered in a closed manner inside the wellbore by comparing the pressure difference. The operation is simple. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a schematic diagram of the structure of the heat-washable anti-backflow gas collection device for recovering casing gas inside a wellbore, according to the present invention.

[0030] The components are as follows: 1-Gas collecting body; 2-Exhaust channel; 3-Intake channel; 4-Anti-backflow single-flow valve ball; 5-Two-way action ball seat; 6-Back pressure spring; 7-Upper connector; 8-Temperature control valve core; 9-Annular straightening limit block; 10-Reset spring; 11-Heat-sensitive paraffin wax; 12-1-Sealing ring I; 12-2-Sealing ring II; 13-Valve core working cylinder; 14-Rubber isolation layer; 15-Plug; 16-Telescopic cylinder. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0032] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0033] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0034] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper," "lower," "horizontal," or "inner" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. Furthermore, terms such as "first" and "second" are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0035] Furthermore, the use of the term "horizontal" does not imply that the component must be absolutely horizontal, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0036] In the description of the embodiments of the present invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.

[0037] The present invention will now be described in further detail with reference to the accompanying drawings:

[0038] This invention proposes a heat-washable anti-backflow gas collection device for recovering casing gas inside a wellbore, such as... Figure 1 As shown, the gas collecting body 1 is vertically installed below the eccentric fixing device. The upper part of the gas collecting body 1 is provided with an exhaust channel 2. A bidirectional ball seat 5 is embedded in the inner wall of the gas collecting body 1. An anti-backflow check valve ball 4 is provided above the bidirectional ball seat 5. A back pressure spring 6 is vertically installed between the upper part of the anti-backflow check valve ball 4 and the inner wall of the gas collecting body 1. One end of the back pressure spring 6 is fixed to the lower end of the exhaust channel 2. The check valve ball 4, the bidirectional ball seat 5 and the back pressure spring 6 constitute an anti-backflow gas collecting check valve. An air inlet channel 3 is provided on the side of the gas collecting body 1.

[0039] An upper connector 7 is installed between the eccentric fixing device and the gas collecting body 1, and the upper connector 7 is connected to the eccentric fixing device by threads. The valve core working cylinder 13 is embedded in the lower part of the inner wall of the gas collecting body 1. A plug 15 is installed on the bottom surface of the valve core working cylinder 13. The inside of the valve core working cylinder 13 is filled with heat-sensitive paraffin wax 11. A piston is provided on the lower end face of the valve stem of the temperature control valve core 8 to form a piston-integrated temperature control valve core. The piston-integrated temperature control valve core has a compact structure. The piston-integrated temperature control valve core is press-fitted into the valve core working cylinder 13 and can move up and down within the valve core working cylinder 13. An annular straightening limit block 9 is provided on the valve stem of the temperature control valve core 8. The annular valve core straightening limit block 9 is located at the lower edge of the air inlet channel 3 and is fixed to the valve core working cylinder 13 to prevent impurities from depositing during the gas collecting process. A return spring 10 is provided between the piston and the annular straightening limit block 9. One end of the return spring 10 is fixed to the annular straightening limit block 9. A rubber isolation layer 14 is provided on the lower end face of the piston. The valve core working cylinder 13, the piston-integrated temperature control valve core, and the bidirectional ball seat 5 constitute a temperature control switch. This switch can temporarily close the gas gathering channel as the temperature of the hot washing fluid rises during hot washing operations, blocking the connection between the annulus and tubing. After the well washing ends and the temperature drops, the gas gathering channel can be reopened, re-establishing the connection between the annulus and tubing. The valve core working cylinder 13 is filled with heat-sensitive paraffin wax 11, with a designed phase change temperature of 75℃. The rubber isolation layer 14 is installed on the lower piston end face of the piston-integrated temperature control valve core using a rubber "interference fit" method, isolating the temperature control valve core 8 from the heat-sensitive paraffin wax 11 within the valve core working cylinder 13. The longitudinal movement of the temperature control valve core 8 cleans the inner wall of the valve core working cylinder 13. The heat-sensitive paraffin wax 11, as the core driving control material for temperature control, expands and contracts in volume due to phase change as the temperature rises and falls, pushing the piston-integrated valve core to produce relative longitudinal displacement within the valve core working cylinder 13.

[0040] Preferably, a telescopic cylinder 16 is installed between the lower end face of the valve stem of the temperature control valve core 8 and the piston. One end of the telescopic cylinder 16 is fixedly connected to the piston, and the other end of the telescopic cylinder 16 is connected to the valve stem of the temperature control valve core 8, allowing the valve stem of the temperature control valve core 8 to slide and extend within the telescopic cylinder 16. The structure of the telescopic cylinder 16 is similar to a common radio telescopic antenna, controlling the relative sliding displacement distance between the piston and the temperature control valve core 8 in the longitudinal direction, as well as the sealing force between the temperature control valve core 8 and the lower seat surface of the double-acting ball seat 5. Since the volume expansion of the thermosensitive paraffin 11 during phase change is difficult to precisely control with temperature, this design avoids excessive volume expansion of the thermosensitive paraffin 11 during phase change, which could cause excessive stress and deformation damage to the valve stem of the temperature control valve core 8. Therefore, the structural design of the telescopic cylinder 16 ensures effective sealing of the temperature control valve core 8 while preventing excessive piston stroke displacement that could cause deformation and damage to the valve stem of the temperature control valve core 8. The upper and lower seat covers of the bidirectional ball seat 5 are the seat covers of the anti-backflow single-flow valve ball 4 and the front hemispherical valve core head of the temperature control valve core 8, respectively. The structure is compact, which can save costs and reduce the body volume. During well cleaning, in addition to the upward longitudinal thrust generated by the increase in volume of the heat-sensitive paraffin 11 as the temperature rises from a solid phase to a liquid phase, the large pressure difference generated by the annulus and tubing on the temperature control valve core 8 produces a large longitudinal sealing force, which is beneficial to the closing and sealing of the temperature control valve core 8.

[0041] The inner wall of the annular centering limit block 9 has a central hole, and a sealing ring I12-1 that contacts the valve stem of the temperature control valve core 8 is installed in the central hole. A sealing ring II12-2 is installed between the outer wall of the piston of the temperature control valve core 8 and the inner wall of the valve core working cylinder 13.

[0042] The back pressure spring 6 uses a high-performance square spring. The anti-backflow check valve ball 4 is seated on the bidirectional action ball seat 5 by its own weight and the preset elastic force of the back pressure spring 6. The pressure difference between the upper and lower parts of the anti-backflow check valve ball 4 is the power for the anti-backflow check valve ball 4 to open and close.

[0043] The lower part of the valve core working cylinder 13 adopts an irregularly shaped, trumpet-shaped design, which can expand the longitudinal expansion range of the heat-sensitive paraffin 11 during its phase change from solid to liquid, thereby increasing the effective longitudinal movement stroke of the integrated temperature control valve core that drives the piston within the valve core working cylinder 13. Simultaneously, it can reduce the amount of heat-sensitive paraffin 11 added, thus reducing the size of the device.

[0044] The working principle and process of the gas collection method of the heat-washable anti-backflow gas collection device for recovering casing gas in the wellbore proposed in this invention are as follows: After the device is run into the well, the wellhead casing venting process can be completely closed. During the process of rising pressure of the associated gas in the casing annulus, the associated gas acts on the anti-backflow check valve ball 4, which is set with a certain back pressure, through the gas inlet channel 3. When the pressure of the associated gas in the casing is greater than the back pressure in the tubing of the device and the back pressure set by the anti-backflow check valve ball 4, the anti-backflow check valve ball 4 moves upward and opens, and the associated gas enters the tubing through the exhaust channel 2, realizing the closed-loop recovery of associated gas in the wellbore. Specifically: The associated gas in the casing annulus acts on the anti-backflow check valve ball 4, which is set with a certain back pressure. When the associated gas pressure inside the casing exceeds the back pressure in the tubing and the back pressure set by the anti-backflow check valve ball 4, the anti-backflow check valve ball 4 moves upward and opens, allowing the associated gas to enter the tubing through the venting channel 2, thus achieving a closed-loop recovery process for the associated gas within the wellbore. When the associated gas pressure in the casing annulus decreases and falls below the back pressure set by the tubing back pressure and the anti-backflow check valve ball 4, the anti-backflow check valve ball 4 moves downward and closes. The associated gas pressure in the wellbore casing annulus recovers, entering a pressure-holding period, and this cycle of pressure-holding, opening and releasing, and then pressure-holding again is repeated, achieving the recovery process of associated gas pressure-holding, opening and releasing, and then pressure-holding again in the casing annulus. The entire process is completed within the wellbore, with no change to the surface process flow. The device requires no additional operation or maintenance during the entire operation.

[0045] The working process of this recovery device in hot washing and dewaxing operations is as follows: As the temperature of the hot washing liquid rises to 75°C, the thermosensitive paraffin 11 expands in volume as it changes from a solid phase to a liquid phase. This pushes the piston-integrated valve core to the double-acting ball seat 5, closing the connection between the device and the oil pipe, thus achieving a temporary and reliable seal between the annulus and the oil pipe. When the hot washing operation ends and the casing temperature decreases, the thermosensitive paraffin 11 shrinks in volume as it changes from a liquid phase back to a solid phase. Under the pushing action of the return spring 10, the piston-integrated valve core of the device leaves the double-acting valve seat 5, reopening the process of the device connecting the device to the oil pipe gas collection channel. Specifically: When the hot washing liquid enters the casing annulus, as the temperature rises to 75°C, the thermosensitive paraffin 11 expands in volume (15%-20%) as it changes from a solid phase to a liquid phase. This pushes the piston-integrated valve core to the double-acting ball seat 5, closing the connection between the device and the oil pipe, thus achieving a temporary and reliable seal between the annulus and the oil pipe. At this time, due to the large discharge during well washing, a large working pressure difference will be generated in the annulus and tubing, which will also act on the temperature control valve core. Combined with the longitudinal thrust generated by the volume expansion of the heat-sensitive paraffin 11 during phase change, a large longitudinal sealing force will be generated, and the temperature control valve core 8 will close and be seated. When the hot washing operation is completed, the working pressure difference between the annulus and tubing disappears. After the casing temperature drops, the heat-sensitive paraffin 11 shrinks in volume when it changes from liquid to solid. Under the pushing action of the return spring 10, the piston-integrated valve core of the device leaves the double-acting valve seat 5 and reopens the gas collection channel of the device connected to the tubing.

[0046] This invention proposes a heat-washable anti-backflow gas gathering device and method for recovering casing gas in a wellbore. The upper end of the gas gathering body 1 is fixedly connected to the tubing inside the wellbore in an eccentric manner via a threaded connection in a "H" shape (the eccentric fixing device is not covered in this patent). After the device is connected to the tubing string, the overall outer diameter meets the inner diameter requirements of the oil wellbore. The exhaust channel 2 of the device's exhaust valve is connected to the tubing via the eccentric fixing device, and the air intake channel 3 of the device is connected to the annulus of the casing. The device is installed in the annular space of the casing on the tubing near the wellhead. The gas gathering body 1 contains an anti-backflow gas gathering one-way valve and a temperature control switch, and the air intake channel 3 is opened on the side of the gas gathering body 1. This invention utilizes the pressure difference between the casing annulus and the tubing as a driving force. When the associated gas pressure in the casing is higher than the back pressure in the tubing, the anti-backflow gas gathering check valve opens, allowing the associated gas to enter the tubing and form an oil-gas mixture with the oil flow. When the pressure difference decreases to a certain value, the anti-backflow gas gathering check valve closes, terminating the gas gathering process and preventing oil leakage from the tubing into the casing annulus. Additionally, reverse circulation hot washing for paraffin removal is a very frequent routine operation in oil wells during winter. During hot washing, as the temperature of the hot washing fluid rises to the set 75°C, the heat-sensitive paraffin 11 expands in volume as it changes from a solid to a liquid state, pushing the piston-integrated valve core to the bidirectional ball seat 5, which closes the gas gathering channel connecting the device to the tubing. When the hot washing operation ends and the casing annulus temperature decreases, the heat-sensitive paraffin 11 contracts in volume as it changes from a liquid to a solid state. Under the pushing action of the return spring 10, the piston-integrated valve core of the device leaves the bidirectional ball seat 5, reopening the gas gathering channel connecting the device to the tubing. In addition, since associated gas absorbs a lot of heat when it is rapidly released from a high-pressure state to a low-pressure state, it is prone to low-temperature freezing. Due to the high temperature inside the wellbore, freezing during the gas gathering process can be suppressed, extending the life of the device and ensuring the reliability of the gas gathering process.

[0047] This invention overcomes the risks of leakage at the connection between the surface gas gathering valve and the gas gathering pipeline, the hidden dangers of freezing in winter, and the difficulties of disassembling and assembling the gas gathering pipeline during well workover operations. It also solves the operational requirement of reverse circulation hot washing and wax removal for the wellbore gas gathering device. This invention simplifies the currently common surface associated gas gathering and recovery process, without changing existing wellhead production facilities, surface gathering and transportation process specifications, and management habits. A hot-washable, differential pressure anti-backflow associated gas recovery and collection device is added inside the wellbore near the wellhead tubing via an eccentric tubing fixing device. This changes the common wellhead surface gas gathering and recovery mode to an in-wellbore gas gathering and recovery mode, while also providing a temperature-controlled hot washing function for the wellbore. The anti-backflow gas gathering single-flow valve of this invention adopts a differential pressure design for opening and closing; it uses heat-sensitive paraffin 11 as the core driving control material for temperature control; the temperature control valve core 8 adopts an integrated piston structure, with a telescopic cylinder connecting the middle valve stem to the integrated push piston at the tail. The structure is compact, small in size, and the temperature control opening and closing is sensitive, with a long service life and reliable technical performance.

[0048] The device disclosed in this invention is designed to recover associated gas separated from crude oil at the bottom of the well during normal oil well production, allowing it to re-enter the oil gathering process and be mixed and transported to downstream sites. The device meets the strength, pressure-bearing requirements, backflow prevention, hot washing operations, and the technical requirements of the wellbore for tools regarding minimum inner diameter, maximum outer diameter, and service life. The device operates when the associated gas pressure in the annulus exceeds the back pressure in the tubing, creating a pressure differential, thus maximizing the recovery of associated gas. This invention effectively addresses the risks of leakage from surface venting valves and gas gathering pipeline connections, the potential for freezing in winter, the difficulties in disassembling and assembling gas gathering pipelines during well workover operations, and the technical requirements of hot washing and dewaxing operations in oil wells. The device features high integration, a small size, a simple and reasonable structural design, fewer sealing points, reliable sealing technology, and a low risk of leakage. It fully utilizes the favorable conditions of the high-temperature environment (15℃) in the wellbore to effectively solve the problem of freezing blockage of gas gathering valves. Simultaneously, it integrates heat-sensitive paraffin as the temperature control drive material, enabling automatic opening and closing of the gas gathering channel based on temperature control (design phase change temperature 75℃). This supports reverse circulation hot washing of oil wells and meets the needs of daily oil well production operations. Compared to surface gas gathering valves, it requires no routine maintenance, is installed during pump inspection, and reduces the number of disassemblies, eliminating surface gas gathering pipelines, reducing sealing points and vulnerable parts. Its lifespan is 1-2 times longer than existing surface gas gathering valves, and the overall cost can be reduced by 10%. It boasts excellent economic performance, superior technology, and high safety and environmental friendliness.

[0049] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A heat-washable anti-backflow gas collection device for recovering casing gas inside a wellbore, characterized in that, The system includes a gas collecting body (1) vertically installed below an eccentric fixing device; an exhaust channel (2) is provided on the upper part of the gas collecting body (1); a bidirectional action ball seat (5) is embedded in the inner wall of the gas collecting body (1); an anti-backflow single-flow valve ball (4) is provided above the bidirectional action ball seat (5); a back pressure spring (6) is vertically installed between the upper part of the anti-backflow single-flow valve ball (4) and the inner wall of the gas collecting body (1); the anti-backflow single-flow valve ball (4), the bidirectional action ball seat (5), and the back pressure spring (6) constitute an anti-backflow gas collecting single-flow valve; and an air inlet channel (3) is provided on the side of the gas collecting body (1). It also includes a valve core working cylinder (13) and a temperature control valve core (8). The valve core working cylinder (13) is embedded below the inner wall of the gas collecting body (1). A plug (15) is installed on the bottom surface of the valve core working cylinder (13). The inside of the valve core working cylinder (13) is filled with heat-sensitive temperature paraffin (11). A piston is provided on the lower end face of the valve stem of the temperature control valve core (8) to form a piston-integrated temperature control valve core. The piston-integrated temperature control valve core is pressed into the valve core working cylinder (13) and can move up and down reciprocally inside the valve core working cylinder (13). The valve stem of the temperature control valve core (8) is provided with an annular straightening limit block (9). The annular straightening limit block (9) is located at the lower edge of the air intake channel (3) and is fixed to the valve core working cylinder (13). A reset spring (10) is provided between the piston and the annular straightening limit block (9). The valve core working cylinder (13), the piston integrated temperature control valve core and the bidirectional ball seat (5) constitute a temperature control switch.

2. The heat-washable anti-backflow gas collecting device for recovering casing gas inside a wellbore according to claim 1, characterized in that, A rubber isolation layer (14) is provided on the lower end face of the piston.

3. The heat-washable anti-backflow gas collecting device for recovering casing gas inside a wellbore according to claim 2, characterized in that, A telescopic cylinder (16) is installed between the lower end face of the valve stem of the temperature control valve core (8) and the piston. One end of the telescopic cylinder (16) is fixedly connected to the piston, and the other end of the telescopic cylinder (16) is connected to the valve stem of the temperature control valve core (8).

4. The heat-washable anti-backflow gas collecting device for recovering casing gas inside a wellbore according to claim 1, characterized in that, The inner wall of the annular straightening limiting block (9) has a central hole, and a sealing ring I (12-1) is provided in the central hole to contact the valve stem of the temperature control valve core (8).

5. The heat-washable anti-backflow gas collecting device for recovering casing gas inside a wellbore according to claim 1, characterized in that, A sealing ring II (12-2) is provided between the outer wall of the piston of the temperature control valve core (8) and the inner wall of the valve core working cylinder (13).

6. The heat-washable anti-backflow gas collecting device for recovering casing gas inside a wellbore according to claim 1, characterized in that, The lower end of the valve core working cylinder (13) is flared.

7. The heat-washable anti-backflow gas collecting device for recovering casing gas inside a wellbore according to claim 1, characterized in that, An upper connector (7) is installed between the eccentric fixing device and the gas collecting body (1), and the upper connector (7) is connected to the eccentric fixing device by a thread.

8. The heat-washable anti-backflow gas collecting device for recovering casing gas inside a wellbore according to claim 1, characterized in that, The air intake channel (3) has at least two.

9. A method for using the heat-washable anti-backflow gas collecting device for recovering casing gas inside a wellbore as described in any one of claims 1 to 8, characterized in that, Includes the following steps: Gas is introduced into the gas collecting body (1) through the gas inlet channel (3). When the gas pressure in the gas collecting body (1) is greater than the gas pressure in the eccentric fixed device, the anti-backflow single-flow valve ball (4) moves upward and opens. The introduced gas enters the oil pipe of the eccentric fixed device through the exhaust channel (2), realizing the closed recovery process of associated gas in the wellbore. When the gas pressure in the gas collecting body (1) is less than the gas pressure in the eccentric fixed device, the anti-backflow single-flow valve ball (4) moves down to the bidirectional action ball seat (5), and the gas in the eccentric fixed device resumes the pressure-holding period, thus repeatedly realizing the cycle of pressure-holding, opening and releasing, and pressure-holding again in the annular space of the casing.

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