Bottom bottom pressure control check valve applied to gas lift of shale oil and gas well

Abstract

The invention relates to the technical field of oil production engineering equipment, in particular to a shaft bottom pressure control check valve applied to gas lift of a shale oil and gas well. The shaft bottom pressure control check valve applied to gas lift of the shale oil and gas well comprises an upper valve body and a lower valve body which are connected end to end, a double-valve-plug type check valve structure is arranged in the upper valve body and comprises a fixed piston, and an upper valve plug and a lower valve plug are arranged at the two ends of the fixed piston respectively. The opening pressure of the check valve is controlled and adjusted through the pre-tightening spring and the compression spring; and a bottom sealing ring made of a wear-resistant and corrosion-resistant material is clamped and fixed between the upper valve body and the lower valve body and is matched with the lower valve plug. According to the shaft bottom pressure control check valve applied to gas lift of the shale oil and gas well, the technical problem that opening force is affected by back pressure is solved through a double-valve-plug type check valve structure; the opening force of the device is controlled and adjusted through the pre-tightening spring and the compression spring; and the erosion resistance and the scale prevention performance of the device are improved through the bottom sealing ring made of wear-resistant and corrosion-resistant materials, and the service life of the device is prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of oil production engineering equipment, and particularly to a bottom-hole pressure-controlled check valve applied to gas lift in shale oil and gas wells. Background Art

[0002] During the exploitation of oilfield shale oil and gas, the gas lift method is used for the exploration and development of conventional shale oil and gas wells. High-pressure gas is injected into the annulus between the casing and the tubing or into the tubing through the ground, so that it is mixed with the formation fluid. A check valve is generally used at the bottom of the well to ensure the one-way flow of the downhole medium. In the prior art, the commonly used check valve fixes the valve plug or steel ball in the valve body on the spring support. After pushing the valve plug or steel ball to compress the spring, the gas and liquid pass through, and then rely on the spring force to return to the sealing surface to achieve effective sealing. However, its opening and closing require a certain pressure difference at both ends of the check valve, and the opening and closing of the check valve are not smooth; it cannot achieve precise control of the bottom-hole pressure, and its opening and closing pressures cannot be adjusted; at the same time, since its core sealing element mainly adopts the form of metal vulcanized rubber, its sealing performance and corrosion resistance are unreliable, and the service life of the device is low. Therefore, in view of the above deficiencies, a bottom-hole pressure-controlled check valve applied to gas lift in shale oil and gas wells is proposed. Summary of the Invention

[0003] (I) Technical Problems to be Solved Aiming at the deficiencies of the prior art, the present invention provides a bottom-hole pressure-controlled check valve applied to gas lift in shale oil and gas wells, whose opening and closing are only controlled by the pressure on one side and it opens at a fixed pressure; it can precisely adjust the opening pressure of the check valve to meet the needs of various working environments; at the same time, it can effectively improve the erosion resistance and scale prevention performance of the device and extend the service life of the device.

[0004] (II) Technical Solutions To solve the above problems, the present invention provides a bottom-hole pressure-controlled check valve applied to gas lift in shale oil and gas wells, comprising: an upper valve body and a lower valve body, the lower part of the upper valve body is fixedly connected to the lower valve body by threads, and a double-valve-plug type one-way valve structure is arranged in the upper valve body; The double-valve-plug type one-way valve structure includes a fixed piston installed in the upper valve body. The outer diameter of the top end of the fixed piston matches the inner diameter of the upper valve body, and the outer diameter of the lower end is smaller than that of the top end; an upper valve plug and a lower valve plug that can move up and down are respectively arranged at the upper and lower ends of the fixed piston. The outer diameters of the top end of the upper valve plug and the bottom end of the lower valve plug both match the inner diameter of the upper valve body, and the contact surfaces are chamfer structures with diameters shrinking downward to respectively form an upper one-way valve and a lower one-way valve; there is a gap between the bottom end of the upper valve plug and the top end of the lower valve plug inside the fixed piston; a number of flow holes are arranged at the top end of the fixed piston, and the liquid pushes the upper valve plug upward through the flow holes; A bottom sealing ring is provided between the upper valve body and the lower valve body. The bottom sealing ring is made of wear-resistant and corrosion-resistant material and is embedded in the upper valve body, contacting the lower valve plug, and its inner wall is in high-precision grinding fit with the bottom end of the lower valve plug. Inside the fixed piston, a pre-tightening spring is provided at the lower end of the upper valve plug to press the upper valve plug downward. Outside the fixed piston, a compression spring is provided at the upper end of the lower valve plug to press the lower valve plug downward. By adjusting the pre-tightening spring and the compression spring respectively, the opening pressures of the upper one-way valve and the lower one-way valve can be adjusted.

[0005] Preferably, the bottom end of the upper valve plug is fixedly connected to the nut. The top end of the pre-tightening spring contacts the fixed piston upward, and the bottom end contacts the top edge of the nut to apply force to the upper valve plug. An adjusting ring is provided outside the fixed piston, and an upper adjusting ring is provided above the adjusting ring. One end of the compression spring contacts the adjusting ring, and the other end applies force to the upper surface of the bottom end of the lower valve plug.

[0006] Preferably, the upper adjusting ring and the adjusting ring are connected to the fixed piston by threads.

[0007] Preferably, a plurality of circumferentially arranged upper sealing rings are provided on the outer wall of the bottom end of the upper valve plug, and a plurality of circumferentially arranged lower sealing rings are provided on the outer wall of the top end of the lower valve plug.

[0008] Preferably, the bottom sealing ring is clamped and fixed by the upper valve body and the lower valve body, and the material is polytetrafluoroethylene.

[0009] Preferably, a secondary sealing ring is provided between the bottom sealing ring and the inner wall of the upper valve body.

[0010] Preferably, anti-rotation pins are provided at the lower part of the upper valve body, and the anti-rotation pins are connected to the upper valve body and the lower valve body by threads.

[0011] (III) Beneficial Effects The bottom-hole pressure-control check valve applied to gas lift in shale oil and gas wells provided by the present invention enables the opening of the check valve to be affected only by the pressure on one side through the double-valve-plug one-way valve structure, realizes fixed-pressure opening, and solves the technical problem of the back pressure affecting the opening force. The opening force of the check valve is controlled by using the pre-tightening spring and the compression spring. By adjusting the pre-tightening spring and the compression spring, the opening force of the device can be adjusted, and precise control of the opening force can be achieved. By optimizing the material and innovatively designing the structure of the core sealing parts, the erosion resistance and scale prevention performance of the device are improved, and the service life of the device is prolonged. Description of the Drawings

[0012] Figure 1 It is a schematic structural diagram of the bottom-hole pressure-control check valve applied to gas lift in shale oil and gas wells of the present invention.

[0013] Among them, 1. upper valve body; 2. upper valve plug; 3. preloading spring; 4. fixed piston; 5. upper sealing ring; 6. nut; 7. upper adjusting ring; 8. lower adjusting ring; 9. lower sealing ring; 10. compression spring; 11. lower valve plug; 12. bottom sealing ring; 13. anti-rotation pin; 14. lower valve body; 15. secondary sealing ring. Detailed implementation mode

[0014] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0015] In the description of the present invention, it is necessary to understand that the orientation or positional relationship indicated by "upper", "lower", "inner", "outer", "top", "bottom", etc. is based on the orientation or positional relationship shown in the accompanying drawings. The purpose is only to facilitate the description of the present invention and simplify the description, rather than indicating or implying that the components referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present invention.

[0016] As Figure 1 shown, the present invention provides a bottomhole pressure control check valve applied to gas lift in shale oil and gas wells, specifically including: an upper valve body 1 and a lower valve body 2. The lower part of the upper valve body 1 is fixedly connected to the lower valve body 2 by threads, and a double-valve-plug type one-way valve structure is arranged in the upper valve body 1; the double-valve-plug type one-way valve structure includes an upper one-way valve and a lower one-way valve, and the opening directions of the upper and lower one-way valves are the same.

[0017] Among them, the double-valve-plug type one-way valve structure includes a fixed piston 4 installed in the upper valve body 1. The outer diameter of the top end of the fixed piston 4 matches the inner diameter of the upper valve body 1, and the outer diameter of the lower end is smaller than that of the top end. The fixed piston 4 is installed in the upper valve body 1 by threads. The valve plugs of the upper one-way valve and the lower one-way valve are installed in the fixed piston 4. During operation, the liquid flows in the space between the fixed piston 4 and the upper valve body 1. An anti-rotation pin 13 is arranged at the lower part of the upper valve body 1. The anti-rotation pin penetrates inward through the upper valve body 1 and is connected to the lower valve body 14, fixing the positions of the upper valve body 1 and the lower valve body 14, preventing the lower valve body 14 from rotating relative to the upper valve body 1 under the action of force during downhole operation, resulting in the disassembly of the device, and improving the stability and safety of the device. Generally, the anti-rotation pin 13 is connected to the upper valve body 1 and the lower valve body 14 by threads, which is simple to install and reusable, improving the economy of the device.

[0018] It should be noted that an upper valve plug 2 and a lower valve plug 11 capable of moving up and down are respectively provided at the upper and lower ends of the fixed piston 4. The outer diameters of the top end of the upper valve plug 2 and the bottom end of the lower valve plug 11 are both matched with the inner diameter of the upper valve body 1, and the contact surfaces are chamfer structures with diameters shrinking downward, respectively forming an upper one-way valve and a lower one-way valve. Since the chamfer directions are the same, the opening directions of the upper one-way valve and the lower one-way valve are the same. There is a gap between the upper valve plug 2 and the lower valve plug 11 in the fixed piston 4, enabling the upper valve plug and the lower valve plug to be opened separately.

[0019] In addition, a number of vertical flow holes are provided at the top end of the fixed piston 4. During the opening process of the device, the liquid pushes the upper valve plug 2 upward through the flow holes. Generally, there is a gap between the top end of the fixed piston 4 in the upper valve body 1 and the top end of the upper valve plug 2 in the closed state, increasing the contact area of the liquid below with the upper valve plug during the opening process and improving the opening efficiency of the device.

[0020] In the present invention, inside the fixed piston 4, a pre-tightening spring 3 is provided at the lower end of the upper valve plug 2 to press the upper valve plug 2 downward. The force exerted by the pre-tightening spring 3 on the upper valve plug 2 is the opening pressure of the upper one-way valve; outside the fixed piston 4, a compression spring 10 is provided at the upper end of the lower valve plug 11 to press the lower valve plug 11 downward. The force exerted by the compression spring 10 on the lower valve plug 11 is the opening force of the lower one-way valve. In the initial stage of the actual working process, when the thrust of the liquid below on the lower valve plug 11 is greater than the opening force of the lower valve plug 11, due to the gap between the upper valve plug 2 and the lower valve plug 11 in the fixed piston 4, the lower valve plug 11 can move upward to open without affecting the upper valve plug 2. Then, the lower valve plug 11 contacts the upper valve plug 2 and transmits the force received upward to the upper valve plug 2. At the same time, the liquid pushes the upper valve plug 2 upward through the lower one-way valve and the flow holes of the fixed piston 4. When the resultant force is greater than the starting force of the upper valve plug 2, the upper one-way valve opens. In this process, the opening of the double-valve-plug one-way valve structure is only affected by the liquid pressure below, avoiding the interference of the back pressure above on the opening of the device and solving the technical problem of the back pressure affecting the opening force. During normal operation, when the pressure above the one-way valve is greater than the pressure below, the liquid pushes both the upper valve plug 2 and the lower valve plug 11 simultaneously, and the upper valve plug 2 transmits the pressure received to the lower valve plug 11. At this time, the upper valve plug 2 and the lower valve plug 11 move downward to close the double-valve-plug one-way valve structure.

[0021] Generally, in order to ensure the smooth opening of the one-way valve, the set value of the opening pressure of the upper one-way valve is less than that of the lower one-way valve. After the lower valve plug 11 moves upward to contact the upper valve plug 2, it can smoothly push the upper valve plug 2 upward to open the upper one-way valve.

[0022] To meet the working requirements of different oil and gas well conditions, the opening forces of the upper check valve and the lower check valve in the double-valve-plug one-way valve structure can be adjusted by replacing the preloading spring 3 and the compression spring 10. Generally, the preloading spring 3 and the compression spring 10 are in the form of disc springs or round wire springs. Among them, the disc spring has a short stroke and a large force value, and the provided force is more stable; there are many types of round wire springs and their structures are simple and easy to install, and it is easier to purchase round wire springs of suitable models for the working requirements. By reasonably selecting the models and forms of the preloading spring 3 and the compression spring 10, the opening force of the double-valve-plug one-way valve structure can meet the working requirements of various conditions, and at the same time, the closing pressure of the double-valve-plug one-way valve structure can also be adjusted. When the pressure above the check valve or the pressure difference between both sides reaches the set value, the device closes under the action of the preloading spring 3 and the compression spring 10, and while controlling the opening pressure of the control device, it can also control the closing pressure of the device.

[0023] Among them, inside the fixed piston 4, the bottom end of the upper valve plug 2 is provided with a nut 6 and is connected to the nut 6 by a thread. One end of the preloading spring 3 contacts the fixed piston 4, and the other end presses the upper valve plug 2 downward by contacting the outer edge of the nut 6. At the same time, by rotating the nut 6, the height of the preloading spring 3 can be changed; the lower adjusting ring 8 is provided outside the fixed piston 4 by a thread. One end of the compression spring 10 contacts the lower adjusting ring 8, and the other end contacts the upper surface of the bottom end of the lower valve plug 11 and presses the lower valve plug 11 downward. An upper adjusting ring 7 is provided above the lower adjusting ring 8. The upper adjusting ring 7 is connected to the fixed piston 4 by a thread and plays a role in supporting and strengthening the lower adjusting ring 8 to prevent the lower adjusting ring 8 from detaching from the fixed piston 4 under force during the working process. By rotating the nut 6 and the lower adjusting ring 8, their respective heights can be changed, thereby changing the initial compression states of the preloading spring 3 and the compression spring 10, changing their initial pressures, and precisely adjusting the opening forces of the upper and lower check valves, improving the accuracy and working efficiency of the device.

[0024] It should be noted that several circumferentially arranged upper sealing rings 5 are provided on the outer wall of the bottom end of the upper valve plug 2, and several circumferentially arranged lower sealing rings 9 are provided on the outer wall of the top end of the lower valve plug 11. The upper sealing rings 5 and the lower sealing rings 9 cooperate to maintain the sealing inside the fixed piston 4, prevent liquid from flowing into the fixed piston 4 during the working process and affecting the normal operation of the device, and improve the stability of the device.

[0025] Such as Figure 1As shown, a bottom sealing ring 12 is provided between the upper valve body 1 and the lower valve body 14. The bottom sealing ring 12 is embedded in the upper valve body 1 to contact the lower valve plug 11 and is in chamfer sealing fit with the bottom end of the lower valve plug 11. The bottom sealing ring 12 is made of wear-resistant and anti-corrosion materials, which not only ensures the stable sealing performance of the device but also has good corrosion resistance and anti-scaling performance. Generally, the material of the bottom sealing ring 12 is polytetrafluoroethylene. According to the experimental results, polytetrafluoroethylene is the material with the best comprehensive performance in terms of corrosion resistance, elasticity, and economy. When economy is not considered, it can be replaced with other materials with better performance.

[0026] Among them, the bottom sealing ring 12 is installed between the upper valve body 1 and the lower valve body 14. When the upper valve body 1 and the lower valve body 14 are installed, the bottom sealing ring 12 is clamped and fixed. After clamping, the position of the bottom sealing ring 12 is stable. Under the clamping action, its volume is compressed and it is extruded towards the inner ring, increasing the contact area between it and the lower valve plug 11, greatly improving the sealing, corrosion resistance, and anti-scaling performance of the device.

[0027] It should be noted that a secondary sealing ring 15 is provided between the outer ring of the bottom sealing ring 12 and the upper valve body 1. The secondary sealing ring 15 seals the bottom sealing ring 12 and the upper valve body 1, further improving the sealing performance of the device.

[0028] The bottom hole pressure control check valve applied to gas lift in shale oil and gas wells provided by the present invention can solve the technical problem that the back pressure of the bottom hole pressure control check valve affects the opening force, finely control the opening and closing pressures of the check valve, and greatly improve the corrosion resistance and anti-scaling ability of the device. The specific working process of the device is as follows: First, according to the working environment and requirements, select appropriate pre-tightening springs and compression springs, and adjust the nuts and upper and lower adjusting rings to appropriate positions, and assemble the device according to the requirements. In this process, by selecting the models and specifications of the pre-tightening springs and compression springs and adjusting the positions of the nuts and upper and lower adjusting rings, the opening pressure of the check valve meets the working environment requirements of the target well.

[0029] Then, lower the device into the working well for gas lift operation. During the gas lift operation, when the pressure of the liquid below the device on the lower valve plug is greater than the opening force of the lower valve plug, the lower valve plug opens and the liquid flows upward. The lower valve plug moves upward to contact the upper valve plug and cooperates with the liquid to push the upper valve plug upward to open, and the device is in a flowing state.

[0030] Sometimes, the pressures at both ends of the check valve at the bottom of the well will fluctuate. When the pressure above the check valve gradually becomes higher than the pressure below, the liquid squeezes the upper valve plug downward. The upper valve plug and the liquid simultaneously push the lower valve plug downward to close it, and then the liquid continues to push the upper valve plug to the closed state. At this time, the check valve is in a closed state.

[0031] During the whole working process, the bottom sealing ring cooperates with the lower valve plug when it is closed to seal the whole device. At the same time, when the device is opened, due to its own corrosion resistance, it can achieve good erosion resistance and scale prevention effects.

[0032] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A bottomhole pressure control check valve applied to gas lift in shale oil and gas wells, characterized in that Comprising: An upper valve body (1) and a lower valve body (14), the upper valve body (1) and the lower valve body (14) are fixedly connected by threads, and a double-valve-plug type one-way valve structure is provided inside the upper valve body (1); The double-valve-plug type one-way valve structure includes a fixed piston (4) installed inside the upper valve body (1). The outer diameter of the top end of the fixed piston (4) matches the inner diameter of the upper valve body (1), and the outer diameter of the lower end is smaller than that of the top end. An upper valve plug (2) and a lower valve plug (11) that can move up and down are respectively provided at the upper and lower ends of the fixed piston (4). The outer diameters of the top end of the upper valve plug (2) and the bottom end of the lower valve plug (11) both match the inner diameter of the upper valve body (1), and the contact surfaces are chamfer structures that contract downward in diameter, respectively forming an upper one-way valve and a lower one-way valve. There is a gap between the bottom end of the upper valve plug (2) and the top end of the lower valve plug (11) inside the fixed piston (4). A number of flow holes are provided at the top end of the fixed piston (4), and the liquid pushes the upper valve plug (2) upward through the flow holes; A bottom sealing ring (12) is provided between the upper valve body (1) and the lower valve body (14). The bottom sealing ring (12) is made of wear-resistant and anti-corrosion material. The bottom sealing ring (12) is embedded inside the upper valve body (1), contacts the lower valve plug (11), and the inner wall is in high-precision grinding fit with the bottom end of the lower valve plug (11); Inside the fixed piston (4), a pre-tightening spring (3) is provided at the lower end of the upper valve plug (2) to squeeze the upper valve plug (2) downward. Outside the fixed piston (4), a compression spring (10) is provided at the upper end of the lower valve plug (11) to squeeze the lower valve plug (11) downward. By adjusting the pre-tightening spring (3) and the compression spring (10) respectively, the opening pressures of the upper one-way valve and the lower one-way valve can be adjusted.

2. The bottomhole pressure control check valve applied to gas lift in shale oil and gas wells according to claim 1, wherein The bottom end of the upper valve plug (2) is fixedly connected to a nut (6). The top end of the pre-tightening spring (3) contacts the fixed piston (4) upward, and the bottom end contacts the top edge of the outside of the nut (6) to apply force to the upper valve plug (2) upward. A lower adjusting ring (8) is provided outside the fixed piston (4), and an upper adjusting ring (7) is provided above the lower adjusting ring (8). One end of the compression spring (10) contacts the lower adjusting ring (8), and the other end applies force to the upper surface of the bottom end of the lower valve plug (11).

3. The bottomhole pressure control check valve applied to gas lift of shale oil and gas wells according to claim 2, wherein, The upper adjusting ring (7) and the lower adjusting ring (8) are connected to the fixed piston (4) by threads.

4. The bottomhole pressure control check valve applied to gas lift of shale oil and gas wells according to claim 1, wherein, A number of circumferentially arranged upper sealing rings (5) are provided on the outer wall of the bottom end of the upper valve plug (2), and a number of circumferentially arranged lower sealing rings (9) are provided on the outer wall of the top end of the lower valve plug (11).

5. The bottomhole pressure control check valve applied to gas lift of shale oil and gas wells according to claim 1, wherein The bottom sealing ring (12) is clamped and fixed by the upper valve body (1) and the lower valve body (14), and the material is polytetrafluoroethylene.

6. The bottom-hole pressure control check valve applied to gas lift of shale oil and gas wells according to claim 5, wherein, A secondary sealing ring (15) is provided between the bottom sealing ring (12) and the inner wall of the upper valve body (1).

7. The bottomhole pressure control check valve applied to gas lift in shale oil and gas wells according to claim 1, characterized in that, An anti-rotation pin (13) is provided at the lower part of the upper valve body (1), and the anti-rotation pin (13) is connected to the upper valve body (1) and the lower valve body (14) by threads.

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