Downhole fluid two-way control valve and downhole accumulated liquid cleaning method

Abstract

The invention belongs to the technical field of oil and gas development, and particularly relates to an underground fluid two-way control valve. The downhole fluid two-way control valve comprises a connecting sleeve; the first check valve is arranged in the connecting sleeve, and the first check valve is configured to allow fluid to flow from top to bottom; the sliding sleeve is arranged in the connecting sleeve through a pin, and an overflowing channel is arranged along the central axis of the sliding sleeve; in the first state, the sliding sleeve is located above the first check valve. And in the second state, the sliding sleeve extends into the first check valve, so that the fluid can flow through the first check valve without being limited.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas development technology, specifically relating to a downhole fluid bidirectional control valve and a method for cleaning up accumulated fluid at the bottom of the well. Background Technology

[0002] Oil and gas development is a systematic project covering geology, drilling, well completion, production enhancement, extraction, and transportation. With rapid economic development, energy demand is rising sharply, and oil and gas development has shifted from conventional oil and gas resources to unconventional oil and gas such as tight oil and gas, shale oil and gas, and coalbed methane. Horizontal well fracturing technology has become the mainstream technology.

[0003] Unconventional oil and gas resources are buried deep and have low porosity, often requiring hydraulic fracturing to establish oil and gas channels in the formation. As oil and gas well development enters the middle and late stages, formation energy gradually decreases, fluid accumulates in the well, and oil and gas production declines rapidly.

[0004] To address these issues, high-pressure gases such as compressed natural gas and nitrogen are typically injected into the well. The compressed gas is injected through the annulus or tubing and enters through a gas lift valve on the tubing string. This reduces the liquid density and, through fluid circulation, lifts the liquid in the oil and gas well to the surface, reducing the resistance of the accumulated liquid to the natural gas in the formation and thus releasing production capacity.

[0005] Because unconventional oil and gas wells are deep and have a lot of fluid accumulation in the horizontal section, conventional drainage and gas production technologies cannot fully drain the fluid in the horizontal section, affecting natural gas production capacity. In order to achieve efficient drainage and gas production in the horizontal section of oil and gas wells, this invention provides a downhole fluid bidirectional control valve and a method for cleaning fluid accumulation at the bottom of the well. Summary of the Invention

[0006] To address the technical problems described above, this invention aims to provide a downhole fluid bidirectional control valve that can prevent gas leakage during pressurized tubing operations in gas wells and enable the well bottom fluid cleaning method provided by this invention.

[0007] The present invention also provides a method for cleaning up accumulated liquid at the bottom of a well, which can achieve efficient drainage and gas production in the horizontal section of an oil and gas well.

[0008] According to the present invention, a downhole fluid bidirectional control valve is provided, comprising:

[0009] Connecting sleeve;

[0010] Two one-way valves with opposite directions are disposed within the connecting sleeve. The upper one-way valve is configured to allow fluid to flow unidirectionally from bottom to top, and the lower one-way valve is configured to allow fluid to flow unidirectionally from top to bottom.

[0011] A sliding sleeve, which is set in the connecting sleeve by a pin, has a flow channel along the central axis of the sliding sleeve;

[0012] In the first state, the sliding sleeve is located inside the upper check valve, so that the upper check valve cannot restrict the flow direction of the fluid;

[0013] In the second state, the sliding sleeve is located inside the lower check valve, so that the lower check valve cannot restrict the flow direction of the fluid.

[0014] In a preferred embodiment, the one-way valve includes:

[0015] A valve seat coaxially disposed within the connecting sleeve, and a valve hole is provided at the central axis of the valve seat; and

[0016] A valve plate hinged to the valve seat seals the valve orifice when no external force is applied.

[0017] In a preferred embodiment, the edge of the valve plate is hinged to the valve seat by a pin, and a torsion spring is provided on the pin. The torsion spring provides a preload to the valve plate, thereby sealing the valve hole.

[0018] In a preferred embodiment, the one-way valve further includes a valve body coaxially disposed within the connecting sleeve, the valve body being located at one end of the valve seat where a valve plate is provided, and a receiving cavity for accommodating the valve plate is provided on the side of the valve body.

[0019] In a preferred embodiment, the connecting sleeve includes a first sleeve and a second sleeve arranged coaxially from top to bottom. The inner diameter of the first sleeve is smaller than the inner diameter of the second sleeve. A one-way valve located at the bottom is disposed in the second sleeve, and a one-way valve located at the top is disposed in the first sleeve.

[0020] In a preferred embodiment, a lower connector is provided at the lower end of the connecting sleeve, and the upper end of the lower connector extends into the interior of the connecting sleeve.

[0021] In a preferred embodiment, an upper connector is provided at the upper end of the connecting sleeve.

[0022] In a preferred embodiment, a ball seat for throwing is provided inside the sliding sleeve.

[0023] In a preferred embodiment, a sealing ring is provided between the valve seat and the connecting sleeve, and a sealing ring for sealing with the valve plate is provided on the end face of the valve seat.

[0024] According to the present invention, a method for cleaning up fluid accumulation at the bottom of a well is also provided, using a downhole fluid bidirectional control valve provided according to the present invention, comprising the following steps:

[0025] Connect the downhole fluid bidirectional control valve, which is in the first state, to the tubing and lower it to the designed well depth.

[0026] Set the downhole fluid bidirectional control valve to the second state and lower the pipeline into the tubing;

[0027] Gas is injected into the annulus of the pipeline and the oil pipe or into the pipeline to drain the accumulated liquid in the oil pipe.

[0028] Compared with the prior art, the advantages of this application are as follows.

[0029] The downhole fluid bidirectional control valve can be installed on the tubing. During the tubing insertion process, the downhole fluid bidirectional control valve is in its first state, allowing fluid to flow unidirectionally from top to bottom. In other words, the fluid below the downhole fluid bidirectional control valve cannot flow upward. With this setting, the downhole fluid bidirectional control valve can prevent gas channeling of the downhole fluid during the insertion process.

[0030] After the downhole fluid bidirectional control valve is in place, the sealing ball is placed into the ball seat of the sliding sleeve, and then pressure is applied. Under pressure, the sliding sleeve moves downward relative to the connecting sleeve, thereby moving the sliding sleeve from the upper check valve to the lower check valve. At this time, the downhole fluid bidirectional control valve changes to the second state. In the second state, the downhole fluid bidirectional control valve allows fluid to flow unidirectionally from bottom to top. That is, the fluid above the downhole fluid bidirectional control valve cannot flow downward. Under this setting, the well bottom fluid cleaning method provided by this invention can be implemented by pumping gas into the annulus between the pipeline and the tubing or into the pipeline to lift the fluid above the downhole fluid bidirectional control valve to the surface, thereby enabling the natural gas to be extracted smoothly. Attached Figure Description

[0031] The present invention will now be described with reference to the accompanying drawings.

[0032] Figure 1 A schematic diagram of a first state of an embodiment of the downhole fluid bidirectional control valve according to the present invention is shown;

[0033] Figure 2 Showing Figure 1 A schematic diagram of the first and second check valves in the diagram;

[0034] Figure 3 A schematic diagram of a second state of an embodiment of the downhole fluid bidirectional control valve according to the present invention is shown;

[0035] Figure 4 Showing Figure 3 A schematic diagram of the first and second check valves in the diagram;

[0036] Figure 5 A schematic diagram showing the connection of the downhole fluid bidirectional control valve according to the present invention to the tubing for well insertion is shown;

[0037] Figure 6 A schematic diagram of the drainage gas extraction process according to the present invention is shown;

[0038] Figure 7 The diagram shows the flow of downhole fluid after the downhole fluid bidirectional control valve according to the present invention is connected to the tubing and inserted into the well.

[0039] In the picture:

[0040] 1. Connecting sleeve; 11. First sleeve; 12. Second sleeve; 13. Third sleeve; 2. First check valve; 21. First valve seat; 22. First valve hole; 23. First valve plate; 24. First pin; 25. First torsion spring; 26. First valve body; 27. First receiving cavity; 3. Pin; 4. Sliding sleeve; 41. Flow passage; 42. Ball seat; 5. Lower connector; 61. First sealing ring; 62. Second sealing ring; 63. Third sealing ring; 64. Fourth sealing ring 65. Fifth sealing ring; 66. Sixth sealing ring; 67. Seventh sealing ring; 68. Eighth sealing ring; 69. Ninth sealing ring; 7. Upper connector; 8. Sealing ball; 9. Second check valve; 91. Second valve seat; 92. Second valve hole; 93. Second valve plate; 94. Second pin; 95. Second torsion spring; 96. Second valve body; 97. Second receiving cavity; 100. Downhole fluid bidirectional control valve; 101. Wellbore; 102. Tubing; 103. Pipeline.

[0041] In this application, all drawings are schematic and are used only to illustrate the principles of the invention, and are not drawn to scale. Detailed Implementation

[0042] The invention will now be described with reference to the accompanying drawings.

[0043] It should be noted that in this application, the direction near the wellhead after the invention is inserted into the well is described as "up" or a similar term, i.e. Figure 1 Above; the direction away from the wellhead after the well is entered according to the present invention is described as "below" or similar terms, i.e. Figure 1 Below.

[0044] Figure 1 The structure of a downhole fluid bidirectional control valve 100 according to the present invention is shown. Figure 1 As shown, the downhole fluid bidirectional control valve 100 includes a connecting sleeve 1, a first check valve 2, a second check valve 9, and a sliding sleeve 4.

[0045] The connecting sleeve 1 is constructed in a roughly cylindrical shape, and the upper and lower ends of the connecting sleeve 1 are configured to connect with other downhole tools or tubing.

[0046] The second check valve 9 is coaxially sealed inside the cavity of the connecting sleeve 1. The second check valve 9 is configured to allow fluid to flow from bottom to top. In other words, fluid inside the connecting sleeve 1 above the second check valve 9 cannot pass down through the second check valve 9.

[0047] The first check valve 2 is coaxially sealed inside the cavity of the connecting sleeve 1. The first check valve 2 is configured to allow fluid to flow from top to bottom. That is, fluid inside the connecting sleeve 1 located below the first check valve 2 cannot pass upward through the first check valve 2.

[0048] The sliding sleeve 4 is constructed in a roughly cylindrical shape, and a flow channel 41 is provided along the central axis of the sliding sleeve 4.

[0049] In the first state, the sliding sleeve 4 is coaxially mounted inside the connecting sleeve 1 via the pin 3. The sliding sleeve 4 passes through the second check valve 9 and is located above the first check valve 2. At this time, the flow passage 41 of the sliding sleeve 4 connects the inner cavities of the connecting sleeve 1 at both ends of the second check valve 9. That is to say, the sliding sleeve 4 prevents the second check valve 9 from performing a one-way flow restriction function, and the fluid can flow freely through the second check valve 9. At the same time, since the first check valve 2 can perform a one-way flow restriction function, the downhole fluid bidirectional control valve 100 in the first state allows the fluid to flow from top to bottom, but the fluid cannot flow from bottom to top.

[0050] In the second state, such as Figure 3 As shown, the sliding sleeve 4 cuts off the pin 3 and moves downward relative to the connecting sleeve 1. Finally, the sliding sleeve 4 extends into the first check valve 2 and moves below the second check valve 9. At this time, the flow passage 41 of the sliding sleeve 4 connects the inner cavities of the connecting sleeve 1 located on the upper and lower sides of the first check valve 2. That is, the first check valve 2 cannot function as a unidirectional flow restrictor, and the fluid can flow through the first check valve 2 without directional restrictions. Simultaneously, since the second check valve 9 can function as a unidirectional flow restrictor, the downhole fluid bidirectional control valve 100 in the second state allows fluid to flow from bottom to top, but fluid cannot flow from top to bottom.

[0051] In one specific embodiment, a ball seat 42 is provided at the upper end of the sliding sleeve 4. When it is necessary to move the sliding sleeve 4 downward relative to the connecting sleeve 1, a sealing ball 8 is dropped from the ground along the oil pipe into the connecting sleeve 1, so that the sealing ball 8 falls into the ball seat 42, thereby sealing the flow passage 41 of the sliding sleeve 4. Then, pressure is applied from the ground into the connecting sleeve 1 to apply downward pressure to the sliding sleeve 4, so that the sliding sleeve 4 moves downward relative to the connecting sleeve 1.

[0052] In a preferred embodiment, the upper end of the inner cavity of the connecting sleeve 1 is provided as a conical surface, which can guide the sealing ball 8.

[0053] In a preferred embodiment, the lower end outer surface of the sliding sleeve 4 is provided as a tapered surface, which enables it to act as a guide when it extends into the first valve hole 22.

[0054] According to the present invention, in this embodiment, the first check valve 2 and the second check valve 9 have the same structure, the difference being that the first check valve 2 and the second check valve 9 are installed in opposite directions in the connecting sleeve 1.

[0055] In this embodiment, the second one-way valve 9 includes a second valve seat 91 and a second valve plate 93.

[0056] like Figure 1 and Figure 2 As shown, the second valve seat 91 is generally cylindrical in shape, and a second valve hole 92 is provided along the central axis of the second valve seat 91. The second valve seat 91 is coaxially fixed in the inner cavity of the connecting sleeve 1. The second valve hole 92 of the second valve seat 91 can connect the inner cavities of the connecting sleeve 1 located on the upper and lower sides of the second valve seat 91. Furthermore, the size of the second valve hole 92 is larger than the outer diameter of the sliding sleeve 4, so that the sliding sleeve 4 can be disposed in the second valve hole 92.

[0057] The second valve plate 93 is located above the second valve seat 91, and the second valve plate 93 is hinged to the second valve seat 91, with the hinge axis of the second valve plate 93 perpendicular to the central axis of the second valve seat 91. In the first state, as... Figure 1 and Figure 2 As shown, the sliding sleeve 4 is coaxially disposed inside the second check valve 9. Specifically, the upper end of the sliding sleeve 4 is fixedly connected to the connecting sleeve 1 by a pin 3, the middle part of the sliding sleeve 4 passes through the second valve hole 92 of the second valve seat 91, and the lower part of the sliding sleeve 4 extends to the bottom of the second valve seat 91. In this configuration, the second valve plate 93 is in a flipped state, that is, the end face of the second valve plate 93 does not abut against the end face of the second valve seat 91, and the second valve hole 92 of the second valve seat 91 is in an open state.

[0058] In a specific embodiment, such as Figure 2 and Figure 4 As shown, the radial edge of the second valve plate 93 is hinged to the second valve seat 91 via a second pin 94. The second pin 94 is the hinge axis of the second valve plate 93, and it is perpendicular to the central axis of the second valve plate 93, meaning it is parallel to the end face of the second valve plate 93. A second torsion spring 95 is fitted onto the second pin 94, providing preload to the second valve plate 93. This allows the second valve plate 93 to remain in contact with the end face of the second valve seat 91 in the second state, thereby sealing the second valve hole 92.

[0059] Furthermore, such as Figure 2 and Figure 4 As shown, in the second state, the sliding sleeve 4 moves downward relative to the connecting sleeve 1. After the sliding sleeve 4 moves below the second valve plate 93, the second valve plate 93, under the action of the second torsion spring 95, moves from... Figure 2 The displayed state is flipped counterclockwise to Figure 4 In the state shown, the second valve plate 93 can abut against the end face of the second valve seat 91 in parallel. The size of the second valve plate 93 is larger than the size of the second valve hole 92. Therefore, in the second state, the second valve plate 93 can seal the second valve hole 92.

[0060] like Figure 4 As shown, in the second state, the second valve plate 93 of the second flow valve 9 can only rotate clockwise relative to the second valve seat 91. Therefore, when the pressure at the lower part of the second valve plate 93 is greater than the pressure at the upper part, the second valve plate 93 can be opened, and the fluid at the lower part of the second valve plate 93 can flow upward; when the pressure at the upper part of the second valve plate 93 is greater than the pressure at the lower part, the second valve plate 93 cannot be opened, and the fluid at the upper part of the second valve plate 93 cannot flow downward.

[0061] In a preferred embodiment, the second one-way valve 9 further includes a second valve body 96 coaxially disposed within the connecting sleeve 1. For example... Figure 2 and Figure 4 As shown, the second valve body 96 is configured in a generally cylindrical shape. The second valve body 96 is located at the end of the second valve seat 91 where the second valve plate 93 is located; that is, the second valve body 96 is positioned at the upper end of the second valve seat 91. A second receiving cavity 97 is provided on the side of the second valve body 96, and the second receiving cavity 97 is configured to accommodate the second valve plate 93 in the first state. Figure 2 As shown, in the first state, after the second valve plate 93 is flipped upward relative to the second valve seat 91 under the action of the sliding sleeve 4, the second valve plate 93 can enter the second receiving cavity 97.

[0062] In one specific embodiment, the first one-way valve 2 includes a first valve seat 21 and a first valve plate 23.

[0063] like Figure 1 and Figure 2 As shown, the first valve seat 21 is generally cylindrical in shape, and a first valve hole 22 is provided along the central axis of the first valve seat 21. The first valve seat 21 is coaxially fixed in the inner cavity of the connecting sleeve 1. The first valve hole 22 of the first valve seat 21 can connect the inner cavities of the connecting sleeve 1 located on the upper and lower sides of the first valve seat 21. Furthermore, the size of the first valve hole 22 is larger than the outer diameter of the sliding sleeve 4, so that the sliding sleeve 4 can extend into the first valve hole 22 during the downward movement relative to the connecting sleeve 1.

[0064] The first valve plate 23 is located below the first valve seat 21, and the first valve plate 23 is hinged to the first valve seat 21, with the hinge axis of the first valve plate 23 perpendicular to the central axis of the first valve seat 21. In the first state, as... Figure 1 and Figure 2 As shown, the first valve plate 23 can abut parallel to the end face of the first valve seat 21. The size of the first valve plate 23 is larger than the size of the first valve hole 22. Therefore, in the first state, the first valve plate 23 can seal the first valve hole 22. In the second state, as... Figure 3 and Figure 4 As shown, the sliding sleeve 4 extends into the first valve hole 22 and pushes the first valve plate 23 to flip downward relative to the first valve seat 21, thereby releasing the seal of the first valve plate 23 on the first valve hole 22. The flow passage 41 of the sliding sleeve 4 can connect the inner cavity of the connecting sleeve 1 located on the upper and lower sides of the first valve seat 21, so that the fluid below the first valve seat 21 can flow upward through the flow passage 41 through the first valve seat 21, thereby implementing the gas sampling process.

[0065] like Figure 1 As shown, in the first state, the first valve plate 23 of the first one-way valve 2 can only rotate counterclockwise relative to the first valve seat 21. Therefore, when the pressure at the lower part of the first valve plate 23 is greater than the pressure at the upper part, the first valve plate 23 cannot open, and the fluid at the lower part of the first valve plate 23 cannot flow upward. After the first valve plate 23 is pushed downward by the sliding sleeve 4, the one-way flow restriction of the first one-way valve 2 fails, thereby enabling the gas production process. During this process, the first valve plate 23 always remains connected to the first valve seat 21, preventing downhole debris from falling into the well and thus avoiding risks to the safe production of the gas well.

[0066] In a specific embodiment, such as Figure 2 and Figure 4 As shown, the radial edge of the first valve plate 23 is hinged to the first valve seat 21 via a first pin 24. The first pin 24 is the hinge axis of the first valve plate 23. The first pin 24 is perpendicular to the central axis of the first valve plate 23, that is, the first pin 24 is parallel to the end face of the first valve plate 23. A first torsion spring 25 is sleeved on the first pin 24. The first torsion spring 25 provides a preload to the first valve plate 23, so that the first valve plate 23 can remain in contact with the end face of the first valve seat 21 in the first state, thereby sealing the first valve hole 22.

[0067] In a preferred embodiment, the first one-way valve 2 further includes a first valve body 26 coaxially disposed within the connecting sleeve 1. For example... Figure 2As shown, the first valve body 26 is configured in a generally cylindrical shape. The first valve body 26 is located at the end of the first valve seat 21 where the first valve plate 23 is provided, that is, the first valve body 26 is located at the lower end of the first valve seat 21. A first receiving cavity 27 is provided on the side of the first valve body 26, and the first receiving cavity 27 is configured to accommodate the first valve plate 23 in the second state. Figure 3 and Figure 4 As shown, in the second state, after the first valve body 26 is pushed downward relative to the first valve seat 21 by the sliding sleeve 4, the first valve body 26 can enter the first receiving cavity 27.

[0068] According to a specific embodiment of the present invention, the connecting sleeve 1 includes a first sleeve 11 and a second sleeve 12 arranged coaxially from top to bottom. The inner diameter of the first sleeve 11 is smaller than the inner diameter of the second sleeve 12, thereby forming a step at the connection between the first sleeve 11 and the second sleeve 12.

[0069] The second check valve 9 is embedded inside the first sleeve 11. Specifically, an upper connector 7 is provided at the upper end of the connecting sleeve 1. The upper end of the upper connector 7 is used to connect with other downhole tools or tubing. The lower end of the upper connector 7 is sleeved on the outer side of the upper end of the first sleeve 11, and the outer walls of the second valve seat 91 and the second valve body 96 are in contact with the inner wall of the upper connector 7.

[0070] The first one-way valve 2 is disposed inside the second sleeve 12, and the end of the first one-way valve 2 is in contact with the end of the first sleeve 11. Specifically, the upper end face of the first valve seat 21 is in contact with the lower end face of the first sleeve 11.

[0071] According to a specific embodiment of the present invention, a lower connector 5 is provided at the lower end of the connecting sleeve 1. The lower end of the lower connector 5 is used for connection with other downhole tools or tubing. Further, the upper end of the lower connector 5 extends into the interior of the connecting sleeve 1, and the upper end of the lower connector 5 contacts the end of the first check valve 2. Specifically, the lower end face of the first valve body 26 contacts the upper end face of the lower connector 5. The upper and lower ends of the first check valve 2 contact the lower end face of the first sleeve 11 and the upper end face of the lower connector 5, respectively, thereby preventing the first check valve 2 from moving axially relative to the connecting sleeve 1.

[0072] In one specific embodiment, the connecting sleeve 1 further includes a third sleeve 13 coaxially disposed at the upper end of the first sleeve 11, the inner diameter of the third sleeve 13 being smaller than the inner diameter of the first sleeve 11. In the first state, as... Figure 1 As shown, the sliding sleeve 4 is disposed inside the first sleeve 11 by a pin 3, and the upper end face of the sliding sleeve 4 abuts against the lower end face of the third sleeve 13. The pin 3 is located above the second check valve 9.

[0073] In a specific embodiment, such as Figure 2 and Figure 4 As shown, a first sealing ring 61 is provided between the first valve seat 21 and the connecting sleeve 1. A second sealing ring 62 for sealing with the first valve plate 23 is provided on the end face of the first valve seat 21. An eighth sealing ring 68 is provided between the second valve seat 91 and the connecting sleeve 1. A ninth sealing ring 69 for sealing with the second valve plate 93 is provided on the end face of the second valve seat 91.

[0074] In a specific embodiment, such as Figure 1 As shown, a third sealing ring 63 is provided between the lower connector 5 and the connecting sleeve 1. A fourth sealing ring 64, a fifth sealing ring 65, and a sixth sealing ring 66 are provided between the upper connector 7 and the connecting sleeve 1, wherein the fourth sealing ring 64 is located below the second check valve 9, the fifth sealing ring 65 is located above the pin 3, and the sixth sealing ring 66 is located between the pin 3 and the second check valve 9. A seventh sealing ring 67 is provided between the sliding sleeve 4 and the connecting sleeve 1, and the seventh sealing ring 67 is located above the pin 3.

[0075] According to the present invention, a method for cleaning up bottom fluid is also provided, using a downhole fluid bidirectional control valve 100 provided according to the present invention, comprising the following steps: connecting the downhole fluid bidirectional control valve 100 in a first state to an oil tubing 102 and lowering it to the designed well depth; setting the downhole fluid bidirectional control valve 100 in a second state and lowering a pipe 103 into the oil tubing 102; injecting gas into the annulus of the pipe 103 and the oil tubing 102 or into the pipe 103 to discharge the fluid accumulated in the oil tubing 102.

[0076] In one specific embodiment, the steps of the well bottom fluid cleaning method are as follows.

[0077] like Figure 5 As shown, during the pressurized tubing run-in process, the downhole fluid bidirectional control valve 100 is first installed at the bottom of the tubing 102 and lowered into the wellbore 101 until the designed well depth is reached. During the run-in process, the downhole fluid bidirectional control valve 100 is in its first state, and the first check valve 2 is in a one-way shut-off state. That is, the first check valve 2 only allows fluid to flow from top to bottom, but not from bottom to top. The first check valve 2 prevents downhole fluid from flowing upwards from the tubing, thereby ensuring well control safety during tubing run-in. After the tubing is in place, as... Figure 6As shown, a sealing ball 8 is inserted into the oil pipe 102. The sealing ball 8 is preferably a soluble sealing ball, and the material can be soluble magnesium-aluminum alloy, soluble aluminum alloy, soluble resin, etc. The sealing ball 8 is pumped to the ball seat 42 at the upper end of the sliding sleeve 4. Under the action of hydraulic force, the sliding sleeve 4 shears the pin 3 and moves downward. Finally, the sliding sleeve 4 moves to the bottom of the second check valve 9 and extends into the first valve hole 22 and pushes open the first valve plate 23, so that the first check valve 2 loses its one-way flow restriction function and puts the second check valve 9 in a one-way shut-off state, that is, the second check valve 9 only allows the fluid to flow from bottom to top, but does not allow the fluid to flow from top to bottom.

[0078] Then, pipe 103 is lowered into oil pipe 102 until the lower end of pipe 103 reaches above the second check valve 9.

[0079] When the accumulated fluid in tubing 102 reaches above the second check valve 9, high-pressure gas, such as nitrogen, natural gas, or compressed air, is pumped from the ground into the annulus between pipe 103 and tubing 102 (or into pipe 103) using a pump truck or other tools. Under the pressure of the high-pressure gas, the pressure above the second check valve 9 is greater than the pressure below, thus the second check valve 9 is closed. The accumulated fluid at the bottom of the well above the second check valve 9 moves towards the wellhead through the inner cavity of pipe 103 (or the annulus between pipe 103 and tubing), continuously bringing it to the surface, thereby achieving the effect of drainage and gas production. In this way, the second check valve 9 remains closed during the gas injection process, preventing the gas injection pressure from being transmitted to the formation and affecting formation production.

[0080] Once the fluid at the bottom of the well has been drained to a certain extent, gas injection is stopped. Under formation pressure, formation natural gas and formation water begin to flow upwards along tubing 102. Figure 7 As shown, when formation natural gas and formation water flow to the second one-way valve 9, they can push the second valve plate 93, thereby opening the second valve orifice 92. Formation natural gas and formation water flow to the top of the second one-way valve 9. If the natural gas production does not reach the expected level at this time and there is still a lot of liquid at the bottom of the well, gas can be injected repeatedly to continuously discharge the liquid until the natural gas can be successfully extracted.

[0081] To prevent formation sand and gravel from entering the tubing string, a sand screen (not shown) can be installed at the bottom of the tubing string.

[0082] Finally, after the bottom fluid is drained and the natural gas reaches the expected production, gas injection is stopped. When the natural gas passes through the downhole fluid bidirectional control valve 100, it can push open the second valve plate 93 of the second single-flow valve 9 and flow into the tubing 102, flowing along the tubing 102 towards the wellhead.

[0083] In the description of this invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0084] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., 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 this invention according to the specific circumstances.

[0085] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0086] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A downhole fluid bidirectional control valve, characterized in that, include: Connecting sleeve (1); Two one-way valves with opposite directions are provided in the connecting sleeve (1). The one-way valve located above is configured to allow fluid to flow unidirectionally from bottom to top, and the one-way valve located below is configured to allow fluid to flow unidirectionally from top to bottom. as well as A sliding sleeve (4) is provided in the connecting sleeve (1) by means of a pin (3), and an overflow channel (41) is provided along the central axis of the sliding sleeve (4); In the first state, the sliding sleeve (4) is located inside the upper check valve, so that the upper check valve cannot restrict the flow direction of the fluid; In the second state, the sliding sleeve (4) is located inside the lower check valve, so that the lower check valve cannot restrict the flow direction of the fluid.

2. The downhole fluid bidirectional control valve according to claim 1, characterized in that, The one-way valve includes: A valve seat is coaxially disposed within the connecting sleeve (1), and a valve hole is provided at the central axis of the valve seat; and A valve plate hinged to the valve seat seals the valve orifice when no external force is applied.

3. The downhole fluid bidirectional control valve according to claim 2, characterized in that, The edge of the valve plate is hinged to the valve seat by a pin, and a torsion spring is provided on the pin. The torsion spring provides a preload force to the valve plate, thereby sealing the valve hole.

4. The downhole fluid bidirectional control valve according to claim 2, characterized in that, The single-flow valve also includes a valve body coaxially disposed within the connecting sleeve (1). The valve body is located at one end of the valve seat where a valve plate is provided, and a receiving cavity for accommodating the valve plate is provided on the side of the valve body.

5. The downhole fluid bidirectional control valve according to any one of claims 1 to 4, characterized in that, The connecting sleeve (1) includes a first sleeve (11) and a second sleeve (12) arranged coaxially from top to bottom. The inner diameter of the first sleeve (11) is smaller than the inner diameter of the second sleeve (12). A one-way valve located at the bottom is disposed in the second sleeve (12), and a one-way valve located at the top is disposed in the first sleeve (11).

6. The downhole fluid bidirectional control valve according to any one of claims 1 to 4, characterized in that, A lower connector (5) is provided at the lower end of the connecting sleeve (1), and the upper end of the lower connector (5) extends into the interior of the connecting sleeve (1).

7. The downhole fluid bidirectional control valve according to any one of claims 1 to 4, characterized in that, An upper connector (7) is provided at the upper end of the connecting sleeve (1).

8. The downhole fluid bidirectional control valve according to any one of claims 1 to 4, characterized in that, A ball seat (42) for throwing the ball is provided inside the sliding sleeve (4).

9. The downhole fluid bidirectional control valve according to any one of claims 2 to 4, characterized in that, A sealing ring is provided between the valve seat and the connecting sleeve (1), and a sealing ring for sealing with the valve plate is provided on the end face of the valve seat.

10. A method for cleaning accumulated fluid at the bottom of a well, characterized in that, Using the downhole fluid bidirectional control valve according to any one of claims 1 to 9, the following steps are included: Connect the downhole fluid bidirectional control valve in its first state to the oil-bearing tubing (102) and run it to the designed well depth. Set the downhole fluid bidirectional control valve to the second state and lower the pipe (103) into the tubing (102); Gas is injected into the annulus of the pipe (103) and the oil pipe (102) or into the pipe (103) to drain the accumulated liquid in the oil pipe (102).

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