Water injection, polymer injection, self-checking and sealing type anti-backflow wellhead device and use method

Abstract

The application discloses a water injection and poly-well self-checking sealing type anti-backflow wellhead device and a use method, and relates to the technical field of oil and gas field exploitation. The device comprises an inner pipe and an outer pipe, the inner pipe is arranged in the outer pipe, and a backflow prevention mechanism is arranged in the inner pipe. The device is characterized in that a sealing detection mechanism is further arranged. The sealing detection mechanism is arranged between the inner pipe and the outer pipe. The device guarantees that the backflow prevention mechanism is in a good state during the whole injection process. The sealing performance of the backflow prevention mechanism is guaranteed through regular or irregular detection of the sealing detection mechanism arranged in the device.

Description

Technical Field

[0001] This invention relates to the field of oil and gas field development technology, specifically to a water injection, well self-sealing anti-backflow wellhead device and its usage method. Background Technology

[0002] The quality of the wellhead anti-backflow mechanism is a key wellhead component affecting the stability and effectiveness of water injection wells. A survey of wellhead anti-backflow mechanisms in 10 directly affiliated units of the oilfield company revealed that the average effective lifespan of currently used gravity-type and spring-type anti-backflow mechanisms is approximately 521 days. After the device fails, it requires shutting down the well to release pressure, removing the plug, and taking out the valve ball for inspection, which is time-consuming, labor-intensive, and prone to environmental pollution. If the failure of the wellhead anti-backflow mechanism is not detected in time, and a sudden malfunction in the injection system causes the injected solution to backflow, it can lead to sand production in the formation, resulting in a decrease in injection volume. In severe cases, sand can bury the oil layer, and even require well workover operations. Each directly affiliated unit performs 3-10 sand-producing well workover operations annually, which not only wastes operational costs but also seriously affects the timeliness and efficiency of water injection wells and the improvement of formation qualification rates.

[0003] Announcement No. CN219864957U discloses a single-layer injection process string for preventing backflow. This technology is mainly aimed at process strings that are run downhole due to backflow during the operation and construction process.

[0004] The shortcomings and deficiencies of this existing technology are that it can only be applied to temporary construction to prevent backflow during construction, and cannot solve the backflow problem of conventional injection wells due to formation pressure and high wellhead pressure.

[0005] Announcement No. CN217783463U discloses a steady-flow water injection check valve, which relates to the technical field of steady-flow water injection check valves. The check valve includes a check valve body, a shoulder disposed in the channel of the check valve body, a sealing ring disposed at the shoulder of the channel of the check valve body, an independent ball seat disposed at the shoulder of the channel of the check valve body and in contact with the sealing ring, a steel ball disposed in the independent ball seat and enabling unidirectional conduction with the independent ball seat, and a ball seat pressure sleeve disposed in the channel of the check valve body to achieve sealing between the independent ball seat and the check valve body.

[0006] The shortcomings of this existing technology are as follows: its main body is a one-way valve structure. During the water injection process, the one-way valve and valve body are constantly eroded by the injected water. This erosion will damage the roundness of the one-way valve, resulting in poor sealing between it and the valve body. At the same time, the injected water has a certain degree of corrosiveness. When the corrosion-resistant layer is damaged by long-term erosion, the valve body and valve ball will both deteriorate in sealing due to corrosion.

[0007] Announcement No. CN201071703Y discloses a high-pressure water injection single-flow valve, which consists of a plug, a "U"-shaped limit and centering ring, a connector, a valve core, a sealing seat, a connecting pipe, a filter pipe, and an outlet connector.

[0008] The shortcomings of this existing technology are as follows: While the conical gravity sealing method converts line sealing to surface sealing, resulting in a better sealing effect than the ball valve type, it still suffers from the same problem: the sealing part is constantly subjected to scouring. If a leak occurs in the sealing part, it can lead to incomplete closure. Furthermore, none of the above patents allow for real-time inspection of the sealing performance during the production process.

[0009] In summary, the technical solutions, technical problems to be solved, and beneficial effects of the above-disclosed technologies are all different from those of the present invention. Regarding the more technical features, technical problems to be solved, and beneficial effects of the present invention, the above-disclosed technical documents do not provide any technical inspiration. Summary of the Invention

[0010] In view of the above-mentioned defects in the existing technology, the purpose of this invention is to provide a water injection, well filling, self-sealing anti-backflow wellhead device and its usage method.

[0011] To achieve the above objectives, the present invention adopts the following technical solution:

[0012] On one hand, the present invention provides a water injection and well filling self-sealing anti-backflow wellhead device, including an inner pipe and an outer pipe, wherein the inner pipe is disposed inside the outer pipe and an anti-backflow mechanism is disposed inside the inner pipe, and also includes a sealing detection mechanism; the sealing detection mechanism is disposed between the inner pipe and the outer pipe.

[0013] Furthermore, the anti-backflow mechanism includes an inner tube, a sealing element, and an elastic element;

[0014] The lower end of the inner tube is provided with a sealing plate, and the inner tube wall is provided with flow holes;

[0015] The sealing element and the elastic element are disposed in the inner tube. The elastic element is located between the sealing element and the sealing plate. The elastic element positions the sealing element above the flow hole, so that the sealing element seals the inner tube and prevents backflow.

[0016] Furthermore, the seal inspection mechanism includes an inner tube, an outer tube, a detection piston, and a detection spring;

[0017] The inner tube and the upper end of the outer tube are connected by a sealing ring. The outer tube wall is provided with a detection hole, which is located above the flow hole.

[0018] The detection piston is disposed between the inner tube and the outer tube, and the detection piston can slide back and forth in the annular space formed by the outer tube and the inner tube; the upper end of the detection spring is fixedly connected to the sealing ring, and the lower end of the detection spring is fixedly connected to the detection piston.

[0019] The detection piston is normally located between the detection hole and the flow hole, and the detection piston is sealed to the inner wall of the outer tube and the inner wall of the inner tube.

[0020] An axial limiting block is provided on the inner wall of the outer tube above the detection piston. The lower end face of the axial limiting block is located below the detection hole. The axial limiting block is used to limit the position of the detection piston.

[0021] Furthermore, the sealing element is a sealing piston, the elastic element is a starting spring, and the anti-backflow mechanism also includes a starting rod;

[0022] An upper sealing ring is provided on the inner wall of the inner tube above the flow hole, and a lower sealing ring is provided on the inner wall of the inner tube below the flow hole. The sealing piston is disposed between the upper sealing ring and the lower sealing ring. A sealing piston sealing ring is embedded on the top of the sealing piston, and the sealing piston sealing ring can seal with the upper sealing ring.

[0023] The starting rod is connected to the lower end of the sealing piston. The starting rod passes through the lower sealing ring. A limiting ring is set below the lower sealing ring on the starting rod. The starting spring is set between the limiting ring and the sealing plate of the inner tube. The starting spring pushes against the limiting ring, so that the sealing piston is located between the upper sealing ring and the flow hole.

[0024] Furthermore, the inner tube wall has a balance hole between the flow hole and the lower sealing ring.

[0025] Furthermore, the inner tube is an axially unequal diameter body, and the inner tube is divided into a flow pipe section with a flow hole, a balance pipe section with a balance hole, and a power pipe section with a lower sealing ring.

[0026] The inner diameter of the balancing pipe section is larger than that of the flow pipe section.

[0027] Furthermore, the power pipe section contains lubricating oil and air, and the lower sealing ring seals against the outer wall of the starter rod.

[0028] Furthermore, the outer tube and the inner tube are arranged concentrically, the sealing ring is an upper connector, the upper inner wall of the outer tube is threadedly connected to the outer wall of the upper connector, the upper outer wall of the inner tube is threadedly connected to the inner wall of the upper connector, and the lower end of the outer tube is threadedly connected to the lower connector.

[0029] Secondly, this invention provides a detection method for a self-sealing anti-backflow wellhead device for water injection and well filling, using the self-sealing anti-backflow wellhead device for water injection and well filling described in one aspect, comprising the following steps:

[0030] When testing the sealing performance of the piston, the seal moves upward to above the flow hole under the action of the elastic element; the testing equipment is connected to the testing hole, and testing fluid is injected into the annulus between the inner and outer tubes. The testing piston moves downward under the action of fluid pressure. When it moves downward to below the flow hole, the testing fluid enters the inner tube and pushes up the seal.

[0031] The sealing performance of a seal can be determined by detecting changes in fluid pressure. A stable increase in pressure indicates a good seal, while stagnant pressure indicates a poor seal.

[0032] In three aspects, the present invention provides a water injection and aggregation method using a self-sealing anti-backflow wellhead device for water injection and aggregation, comprising the following steps:

[0033] Connect the lower connector to the wellhead and the upper connector to the water injection pipeline. The water injection and pre-filling seal is located above the flow hole of the inner tube. The downhole high-pressure fluid supports the seal. Since the seal closes the channel between the upper and lower parts of the inner tube, the downhole fluid cannot rise, thus avoiding formation backflow. At this time, the detection piston is located between the flow hole and the detection hole. The downhole fluid supports the detection piston, and the upper end face of the detection piston rests on the lower end face of the axial limit block. The detection piston closes the annular channel between the upper and lower parts of the detection piston.

[0034] During water injection, the seal descends to below the flow hole under the pressure of the injected fluid. At this time, the detection piston is located between the flow hole and the detection hole. The downhole fluid supports the detection piston, and the injected fluid enters the annulus between the outer and inner pipes through the flow hole and then descends to inject into the formation.

[0035] Compared with the prior art, the present invention has the following advantages:

[0036] 1. This invention significantly extends the service life of the wellhead anti-backflow mechanism. It adopts a cylinder-liner piston structure, and only one piston component is needed to meet the anti-backflow function of the injection well. During injection, the piston component is located below the drain hole, which prevents the liquid from scouring the seal during the injection process and causing damage.

[0037] 2. This invention ensures that the anti-backflow mechanism is in good condition throughout the injection process. A sealing inspection mechanism is set in the device to ensure the sealing performance of the anti-backflow mechanism through regular or irregular inspections. Attached Figure Description

[0038] Figure 1 This is a schematic diagram showing the state of each component of the water injection and pre-aggregation device of the present invention;

[0039] Figure 2 This is a schematic diagram showing the state of each component of the water injection and agglomeration device of the present invention;

[0040] Figure 3 This is a schematic diagram of the state of each component of the device used to measure the sealing performance of the present invention.

[0041] In the diagram: 1. Upper connector; 2. Upper sealing ring; 3. Detection spring; 4. Detection hole; 5. Inner sealing ring; 6. Outer sealing ring; 7. Detection piston; 8. Sealing piston sealing ring; 9. Sealing piston; 10. Inner tube; 11. Outer tube; 12. Flow hole; 13. Balance hole; 14. Lower sealing ring; 15. Starting rod; 16. Starting spring; 17. Lower connector; 18. Limiting ring. Detailed Implementation

[0042] 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. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] This invention primarily addresses two issues. First, it solves the problem of the short effective period of wellhead anti-backflow mechanisms. Currently, anti-backflow is mainly achieved through the line sealing structure of two components: the ball seat and the ball valve. If either component malfunctions, it will lead to incomplete closure and backflow. Therefore, it is necessary to solve the problem of multiple components and the sealing components being in a state of constant erosion. Second, it solves the problem of routine sealing verification of anti-backflow mechanisms. Because the sealing cannot be verified, it is impossible to inspect even if the anti-backflow mechanism malfunctions.

[0044] Example 1:

[0045] Please see Figures 1 to 3 The present invention provides a water injection and a wellhead device for self-sealing and anti-backflow prevention, comprising an inner pipe 10 and an outer pipe 11. The inner pipe 10 is disposed inside the outer pipe 11, and an anti-backflow mechanism is provided inside the inner pipe 10. A sealing detection mechanism is provided between the inner pipe 10 and the outer pipe 11.

[0046] The anti-backflow mechanism includes an inner tube 10, a sealing piston 9, a starting rod 15, and a starting spring 16. The lower end of the inner tube 10 is a closed structure. The inner tube 10 wall is provided with a flow hole 12. An upper sealing ring 2 is provided above the flow hole 12 on the inner wall of the inner tube 10, and a lower sealing ring 14 is provided below the flow hole 12 on the inner wall of the inner tube 10. The sealing piston 9 is located between the upper sealing ring 2 and the lower sealing ring 14. A sealing piston sealing ring 8 is embedded on the top of the sealing piston 9. The sealing piston sealing ring 8 can seal with the upper sealing ring 2. The starting rod 15 is connected to the lower end of the sealing piston 9. The starting rod 15 passes through the lower sealing ring 14. A limiting ring 18 is provided below the lower sealing ring 14 on the starting rod 15. The starting spring 16 is located between the limiting ring 18 and the lower end sealing plate of the inner tube 10. The starting spring 16 pushes against the limiting ring 18, so that the sealing piston 9 is located between the upper sealing ring 2 and the flow hole 12.

[0047] The sealing and testing mechanism includes an inner tube 10, an outer tube 11, a testing piston 7, and a testing spring 3. The upper ends of the inner tube 10 and the outer tube 11 are connected by a sealing ring. The outer tube 11 has a testing hole 4 on its wall, which is located above the flow hole 12. The testing piston 7 is located between the inner tube 10 and the outer tube 11 and can slide back and forth within the annular space formed by the outer tube 11 and the inner tube 10. The upper end of the testing spring 3 is fixedly connected to the sealing ring, and the lower end of the testing spring is fixedly connected to the testing piston 7. Under normal conditions, the testing piston 7 is located between the testing hole 4 and the flow hole 12. The testing piston 7 is sealed to the inner wall of the outer tube 11 and the inner wall of the inner tube 10. An axial limiting block is provided on the inner wall of the outer tube 11 above the testing piston. The lower end face of the axial limiting block is located below the testing hole 4, and the axial limiting block is used to limit the position of the testing piston 7.

[0048] When the upper sealing ring 2 and the sealing piston sealing ring 8 are sealed together, the space below the upper sealing ring 2 can be effectively separated from the space above it.

[0049] Furthermore, the outer tube and the inner tube 10 are arranged concentrically, the sealing ring is the upper connector 1, the upper inner wall of the outer tube 11 is threadedly connected to the outer wall of the upper connector 1, the upper outer wall of the inner tube 10 is threadedly connected to the inner wall of the upper connector 1, and the lower end of the outer tube 10 is threadedly connected to the lower connector 17.

[0050] Furthermore, the inner tube 10 has a balance hole 13 between the flow hole 12 and the lower sealing ring 14 on its wall. The balance hole 13 allows the sealing piston 9 to move down smoothly.

[0051] Furthermore, the inner tube 10 is an axially unequal diameter body. The inner tube 10 is divided into a flow section with a flow hole 12, a balance section with a balance hole 13, and a power section with a lower sealing ring 14. The inner diameter of the balance section is larger than that of the flow section, so that when the sealing piston 9 moves below the balance hole 13, there is a gap between the sealing piston 9 and the balance section to transmit pressure. The lower sealing ring 14 can prevent the sealing piston 9 from entering the power section.

[0052] Specifically, the upper end of the balance pipe section, i.e. the upper end of the balance hole 13, changes the diameter of the inner pipe 10 at the upper end of the balance hole 13.

[0053] Specifically, the sealing piston 9 and the starting rod 15 are connected by threads, the power pipe section and the balance pipe section are connected by threads, the upper sealing ring 2 is integrally manufactured with the flow pipe section, the flow pipe section and the balance pipe section are integrally manufactured, and the starting rod 15 is integrally manufactured with the limiting ring, making the device easy to assemble.

[0054] Specifically, the lower sealing ring 14 is located 0.3m below the balance hole 13, the limiting ring 18 is at a distance from the lower end face of the starter rod 15, the starter spring 16 is sleeved on the outer wall of the starter rod 15, and grease of 1 / 3 height is added to the power pipe section to lubricate and protect the starter spring 16 and the starter rod 15; the lower sealing ring 14 is sealed to the outer wall of the starter rod 15 by a sealing ring, and air is present in the power pipe section, so that the starter rod 15 moves up and down by compressed air.

[0055] Specifically, the inner wall of the flow passage section is precision ground and treated with anti-corrosion measures. The gap between the flow passage section and the outer wall of the sealing piston 9 is 0.02mm, forming a gap seal, which further improves the sealing performance of the sealing piston 9 during the injection stop period.

[0056] Specifically, the flow passage 12 is composed of two symmetrical circular holes, and the diameter of the flow passage 12 is greater than 10cm; the balance hole 13 is composed of two symmetrical circular holes, and the diameter of the balance hole 13 is 10cm.

[0057] Specifically, the starting spring 16 has a starting pressure of less than 1 MPa; the starting spring 16 has undergone chemical anti-corrosion treatment.

[0058] Specifically, the detection piston 7 is annular. In one embodiment, the detection piston 7 is made of metal, with two outer sealing rings 6 on the outer wall and two inner sealing rings 5 ​​on the inner wall, achieving an annular seal between the inner tube 10 and the outer tube 11. The inner sealing rings 5 ​​are vulcanized rubber rings. In another embodiment, the detection piston 7 is a vulcanized rubber ring, which seals the detection hole 4 during normal water injection. The vulcanized rubber is wear-resistant and can pass through the lateral flow hole 12 and balance hole 13 multiple times.

[0059] Specifically, the detection hole 4 is provided with a test thread, which is used to connect with the matching hydraulic gun.

[0060] Example 2:

[0061] Based on Example 1, combined with Figure 2 This embodiment provides a water injection and polymerization method for a self-sealing anti-backflow wellhead device for water injection and polymerization, including the following steps:

[0062] S1. Connect the lower connector 17 of the water injection and polymer well self-sealing anti-backflow wellhead device to the wellhead, and connect the upper connector 1 to the water injection pipeline. The water injection and polymer pre-sealing piston 9 is located above the flow hole 12 of the inner tube 10. The downhole high-pressure fluid supports the sealing piston 9. Since the sealing piston 9 closes the channel between the upper and lower parts of the inner tube 10, the downhole fluid cannot rise, thus avoiding formation backflow. At this time, the detection piston 7 is located between the flow hole 12 and the detection hole 4. The downhole fluid supports the detection piston 7. The upper end face of the detection piston 7 is against the lower end face of the axial limit block. Since the detection piston 7 closes the annular channel between the upper and lower parts of the detection piston 7, the downhole fluid cannot flow out from the outer tube side to the hole.

[0063] S2. During water injection, the sealing piston 9 descends below the flow hole 12 under the pressure of the injected fluid. At this time, the detection piston 7 is located between the flow hole 12 and the detection hole 4. The downhole fluid supports the detection piston 7. The injected fluid passes through the flow hole 12 and enters the annulus between the outer and inner pipes 10 before descending and injecting into the formation. At this time, the state of the parts of the water injection and well filling self-testing sealing anti-backflow wellhead device is as follows: Figure 2 As shown;

[0064] Example 3:

[0065] Based on Example 1, combined with Figure 3 This embodiment provides a testing method for a self-sealing anti-backflow wellhead device for water injection and polymer wells, including the following steps:

[0066] When testing the sealing performance of the sealing piston 9, stop water injection and polymerization. Under the action of the starting spring 16, the sealing piston 9 moves upward to above the flow hole 12. Connect the testing equipment to the testing hole 4 and inject testing fluid into the annulus between the inner tube 10 and the outer tube 11. The testing piston 7 moves downward under the action of fluid pressure. When it moves downward to below the balance hole 13, the testing fluid enters the inner tube 10. The fluid pushes up the sealing piston 9, and the sealing piston 9 contacts the upper sealing ring 2 to seal. The inner tube 10 and the outer tube are completely sealed. The sealing performance of the sealing piston 9 can be determined by detecting whether the fluid pressure changes. If the pressure rises steadily, the seal is good; if the pressure does not rise, the seal is poor. At this time, the condition of the parts of the water injection and polymerization well self-testing anti-backflow wellhead device is as follows: Figure 3 As shown.

[0067] All components not discussed in detail in this application, as well as the connection methods of these components, are well-known technologies in this field. They can be directly applied and will not be elaborated further.

[0068] In this invention, the term "multiple" refers to two or more unless otherwise explicitly defined. The terms "install," "connect," "link," and "fix" should be interpreted broadly. For example, "connect" can be a fixed connection, a detachable connection, or an integral connection; "link" can be a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0069] In the description of this invention, it should be understood that the terms "upper," "lower," "left," "right," "front," "rear," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or unit referred to must have a specific orientation or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0070] In the description of this specification, the terms "one embodiment," "some embodiments," "specific embodiment," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the present 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.

[0071] The above description is merely a preferred embodiment of the present invention and is not intended to limit the 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 self-sealing anti-backflow wellhead device for water injection and well filling, comprising an inner pipe and an outer pipe, wherein the inner pipe is disposed inside the outer pipe, and an anti-backflow mechanism is disposed inside the inner pipe, characterized in that, This also includes inspection and testing agencies; The sealing and testing mechanism is located between the inner and outer tubes.

2. The water injection and wellhead self-sealing anti-backflow wellhead device according to claim 1, characterized in that, The anti-backflow mechanism includes an inner tube, a sealing element, and an elastic element; The lower end of the inner tube is provided with a sealing plate, and the inner tube wall is provided with flow holes; The sealing element and the elastic element are disposed in the inner tube. The elastic element is located between the sealing element and the sealing plate. The elastic element positions the sealing element above the flow hole, so that the sealing element seals the inner tube and prevents backflow.

3. The water injection, well filling, self-sealing anti-backflow wellhead device according to claim 2, characterized in that, The seal inspection and testing mechanism includes an inner tube, an outer tube, a testing piston, and a testing spring; The inner tube and the upper end of the outer tube are connected by a sealing ring. The outer tube wall is provided with a detection hole, which is located above the flow hole. The detection piston is disposed between the inner tube and the outer tube, and the detection piston can slide back and forth in the annular space formed by the outer tube and the inner tube; the upper end of the detection spring is fixedly connected to the sealing ring, and the lower end of the detection spring is fixedly connected to the detection piston. The detection piston is normally located between the detection hole and the flow hole, and the detection piston is sealed to the inner wall of the outer tube and the inner wall of the inner tube. An axial limiting block is provided on the inner wall of the outer tube above the detection piston. The lower end face of the axial limiting block is located below the detection hole. The axial limiting block is used to limit the position of the detection piston.

4. The water injection, well filling, self-sealing anti-backflow wellhead device according to claim 3, characterized in that, The sealing element is a sealing piston, the elastic element is a starting spring, and the anti-backflow mechanism also includes a starting rod; An upper sealing ring is provided on the inner wall of the inner tube above the flow hole, and a lower sealing ring is provided on the inner wall of the inner tube below the flow hole. The sealing piston is disposed between the upper sealing ring and the lower sealing ring. A sealing piston sealing ring is embedded on the top of the sealing piston, and the sealing piston sealing ring can seal with the upper sealing ring. The starting rod is connected to the lower end of the sealing piston. The starting rod passes through the lower sealing ring. A limiting ring is set below the lower sealing ring on the starting rod. The starting spring is set between the limiting ring and the sealing plate of the inner tube. The starting spring pushes against the limiting ring, so that the sealing piston is located between the upper sealing ring and the flow hole.

5. The water injection, well-sealing, anti-backflow wellhead device according to claim 4, characterized in that, The inner tube wall has a balance hole between the flow hole and the lower sealing ring.

6. A water injection, well-sealing, anti-backflow wellhead device according to claim 5, characterized in that, The inner tube is an axially unequal diameter body, and the inner tube is divided into a flow pipe section with a flow hole, a balance pipe section with a balance hole, and a power pipe section with a lower sealing ring. The inner diameter of the balancing pipe section is larger than that of the flow pipe section.

7. A water injection, well-sealing, anti-backflow wellhead device according to claim 6, characterized in that, The power pipe section contains lubricating oil and air, and the lower sealing ring seals against the outer wall of the starter rod.

8. A water injection, well-sealing, anti-backflow wellhead device according to claim 4, characterized in that, The outer tube and the inner tube are arranged concentrically. The sealing ring is an upper connector. The upper inner wall of the outer tube is threadedly connected to the outer wall of the upper connector. The upper outer wall of the inner tube is threadedly connected to the inner wall of the upper connector. The lower end of the outer tube is threadedly connected to the lower connector.

9. A testing method for a water injection, well-sealing, anti-backflow wellhead device, characterized in that, Using the water injection, well filling, self-sealing anti-backflow wellhead device according to any one of claims 3-7 includes the following steps: When testing the sealing performance of the piston, the seal moves upward to above the flow hole under the action of the elastic element; the testing equipment is connected to the testing hole, and testing fluid is injected into the annulus between the inner and outer tubes. The testing piston moves downward under the action of fluid pressure. When it moves downward to below the flow hole, the testing fluid enters the inner tube and pushes up the seal. The sealing performance of a seal can be determined by detecting changes in fluid pressure. A stable increase in pressure indicates a good seal, while stagnant pressure indicates a poor seal.

10. A water injection and accumulation method for a self-sealing anti-backflow wellhead device for water injection and accumulation, characterized in that, Using the water injection, well filling, self-sealing anti-backflow wellhead device as described in claim 8 includes the following steps: Connect the lower connector to the wellhead and the upper connector to the water injection pipeline. The water injection and pre-filling seal is located above the flow hole of the inner tube. The downhole high-pressure fluid supports the seal. Since the seal closes the channel between the upper and lower parts of the inner tube, the downhole fluid cannot rise, thus avoiding formation backflow. At this time, the detection piston is located between the flow hole and the detection hole. The downhole fluid supports the detection piston. The upper end face of the detection piston is against the lower end face of the axial limit block. The detection piston closes the annular channel between the upper and lower parts of the detection piston. During water injection, the seal descends to below the flow hole under the pressure of the injected fluid. At this time, the detection piston is located between the flow hole and the detection hole. The downhole fluid supports the detection piston, and the injected fluid enters the annulus between the outer and inner pipes through the flow hole and then descends to inject into the formation.

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