Rubber ring plunger device for underground drainage of natural gas well and drainage method

Abstract

The rubber ring plunger device comprises a main body seat, the main body seat is a circular pipe body, an inner through hole is axially formed in the main body seat, the upper end of the inner through hole is a horn mouth, a steel ball is arranged in the horn mouth, a rubber ring mechanism is arranged below the outer portion of the main body seat, and an upper connector is connected to the upper portion of the main body seat. A connecting ring, a lower seat and a lower connector are sequentially connected below the main body seat, righting mechanisms are arranged on the upper portion of the main body seat and the lower seat in the circumferential direction, it is guaranteed that the rubber ring plunger always runs in the middle of an oil pipe, the annular space between a rubber ring and the inner diameter of the oil pipe is 0-0.5 mm all the time, more than 95% of the inner diameter of the oil pipe can be sealed, and efficient drainage can be achieved. The invention further discloses a natural gas underground drainage method, and the problem that an existing drainage plunger placed in an underground oil pipe is low in drainage efficiency is solved.

Description

Technical Field

[0001] This invention belongs to the field of natural gas extraction technology in oilfields, specifically relating to a rubber ring plunger device for drainage of natural gas wells, and also to a method for drainage of natural gas wells. Background Technology

[0002] During natural gas extraction, the reservoir pressure forces water and natural gas from the downhole reservoir into the tubing simultaneously. In the early stages, the high reservoir pressure can lift water to the surface. In the middle and later stages, the reservoir pressure decreases, and not all the water can be lifted to the surface. Some water remains in the tubing, causing the liquid column in the tubing to rise continuously. The increased hydraulic pressure prevents natural gas from entering the well tubing, greatly affecting natural gas production.

[0003] The existing technology uses a natural gas well drainage device that involves placing a drainage plunger in the well. When the well is automatically opened, the gas layer pressure is released, pushing the plunger upwards and lifting the water on top of the plunger to the surface. When the well is automatically shut off, there is no gas flow down the well, and the plunger will fall onto the locking device by its own weight. After the pressure builds up down the well, the well is automatically opened, and the gas flow down the well pushes the plunger upwards to achieve the purpose of drainage.

[0004] Currently, the drainage plungers placed in downhole tubing in various gas fields are mostly steel rods. To reduce weight, a series of grooves are set in the radial direction of the outer circle of the steel rod. The annular gap between the outer diameter of the plunger and the inner diameter of the tubing is 1.5mm. If the plunger is offset to the side, the gap between it and the tubing is a crescent shape with a diameter of no more than 3mm. The large gap between the outer diameter of the plunger and the inner diameter of the tubing results in a large amount of leakage. Most of the water on the plunger flows back downhole, requiring a large airflow to flush the drainage plunger to the wellhead. Only a small amount of water is discharged, resulting in very low drainage efficiency. Furthermore, since the tubing wall is prone to scaling and bulging, the brushes installed on the outer circle of the steel rod are prone to falling off and failing due to the high friction inside the tubing wall, which affects the operation of the drainage plunger and reduces the overall working efficiency. Summary of the Invention

[0005] The purpose of this invention is to provide a rubber ring plunger device for drainage of natural gas wells, which solves the problem of low drainage efficiency of existing drainage plungers placed in downhole tubing.

[0006] Another object of the present invention is to provide a drainage method for a rubber ring plunger device for drainage of natural gas wells.

[0007] The technical solution adopted in this invention is a rubber ring plunger device for drainage in natural gas wells, comprising a main body seat, the main body seat being a circular tube, an axially through hole being opened inside the main body seat, the upper end of the through hole being a bell mouth, a steel ball being placed inside the bell mouth, a rubber ring mechanism being provided on the lower part of the main body seat, an upper connector being connected above the main body seat, and a connecting ring, a lower seat, and a lower connector being connected in sequence below the main body seat, with a straightening mechanism provided on the upper part of the main body seat and the circumference of the lower seat.

[0008] The invention is further characterized in that, The straightening mechanism includes several upper and lower straightening plates. Several longitudinal grooves a are evenly distributed around the upper circumference of the outer wall of the main body, and an upper straightening plate is installed in each longitudinal groove a. Several lower straightening plates are evenly distributed around the circumference of the outer wall of the lower body, and several longitudinal grooves b are evenly distributed around the circumference of the outer wall of the lower body, and a lower straightening plate is installed in each longitudinal groove b. Each upper and lower straightening plate has the same structure, which is an arc-shaped plate. Both ends of the arc-shaped plate are provided with a contraction step. The upper and lower ends of the contraction step are flat. Several notches are vertically opened on the straight end faces of the arc-shaped plate with opposite arcs. A top spring is connected in each notch. A connecting hole is opened in each longitudinal groove a and longitudinal groove b, and the connecting hole connects to the other end of the top spring.

[0009] The rubber ring mechanism includes several rubber rings. The middle and lower parts of the outer wall of the main body are provided with extended external threads. The rubber rings are fitted one by one from the lower end of the extended external threads upward. Each rubber ring is threaded with a spacer ring below it. The spacer rings separate two adjacent rubber rings to form a series of evenly spaced rubber rings. A connecting ring is threaded below the spacer ring at the bottom. The connecting ring locks the rubber ring mechanism.

[0010] The inner diameter of the rubber ring is the same as the outer diameter of the extended external thread. The rubber ring is a sheet-shaped rubber ring, and the gap between the outer diameter of the rubber ring and the inner diameter of the oil pipe is 0-0.5mm.

[0011] The upper part of the upper connector is the retrieval neck, which adopts a small-diameter cylindrical structure. The upper part of the retrieval neck has a boss, and the bottom is connected to a large-diameter cylindrical structure. The small-diameter cylindrical structure and the large-diameter cylindrical structure are integrally formed. The lower end of the large-diameter cylinder has an inner hole, and the lower end of the inner hole is an enlarged hole structure a. The upper end of the enlarged hole structure a has an internal thread a. The upper outer wall of the main body has an external thread a. The external thread a connects to the internal thread a of the upper connector, connecting the main body and the upper connector. The upper part of the internal thread a has a cavity, which connects to the upper flared mouth of the main body. The inner diameter of the cavity is larger than that of the flared mouth. Symmetrical through holes are opened on the side of the cavity.

[0012] The upper part of the main body, along with the shrinkage step above the upper centralizer that is constricted within the longitudinal groove a, extends into the expansion structure a of the upper connector. A retaining ring is fitted onto the main body, with an expansion structure b at the upper end and an internal thread b below it. The shrinkage step below the upper centralizer extends into the expansion structure b at the upper end of the retaining ring, and an external thread b is correspondingly provided on the outer wall of the main body. The internal thread b below the retaining ring connects to the external thread b of the main body. The expansion hole at the upper end of the retaining ring catches the lower shrinkage step of the upper centralizer. Each upper centralizer is lifted by a top spring, so that the shrinkage steps at both ends of the upper centralizer simultaneously fit with the expansion structure a at the lower end of the upper connector and the expansion structure b at the upper end of the retaining ring, ensuring that the outer circle of the upper centralizer matches the inner diameter of the oil pipe.

[0013] The upper internal thread c of the connecting ring is connected to the lower end of the external thread b of the main body. The lower end of the connecting ring has an enlarged hole structure c, and the inner wall of the enlarged hole structure c is provided with an internal thread c. The lower body is a cylindrical structure, and the upper outer wall of the lower body is provided with an external thread c. The internal thread c at the lower end of the connecting ring is connected to the external thread c at the upper part of the lower body. The upper part of the lower body, together with the stepped structure at the upper end of the lower support plate that is constricted in the longitudinal groove b, extends into the enlarged hole structure c at the lower end of the connecting ring.

[0014] The upper end of the lower connector has an enlarged hole structure d, the inner wall of which has an internal thread d, and the outer wall of the lower part of the lower seat has an external thread d. The internal thread d at the upper end of the lower connector is connected to the external thread d at the lower part of the lower seat. The lower part of the lower seat, together with the contraction step at the lower end of the lower stabilizer, extends into the enlarged hole structure d at the upper end of the lower connector. The enlarged hole at the lower end of the connecting ring holds the contraction step at the upper end of the lower stabilizer, and the enlarged hole at the upper end of the lower connector holds the contraction step at the lower end of the lower stabilizer. Each lower stabilizer is lifted by a top spring, so that the contraction steps at both ends of the lower stabilizer are in contact with the enlarged hole structure c at the lower end of the connecting ring and the enlarged hole structure d at the upper end of the lower connector, ensuring that the outer circle of the lower stabilizer matches the inner diameter of the oil pipe. Several blind holes a are opened opposite to the internal thread a and tapped. Several blind holes b are opened opposite to the internal thread c and tapped. Several blind holes c are opened opposite to the internal thread d and tapped. Pins are inserted into the blind holes a, b, and c.

[0015] Another technical solution adopted in this invention is an automatic drainage method for natural gas wells, which uses a rubber ring plunger device for drainage of natural gas wells, and is implemented according to the following steps: Step 1: Connect the plunger tool string to the rubber ring plunger device used for drainage of natural gas wells, and use a crane to put the connected plunger tool string into the blowout preventer; the plunger tool string consists of a rope cap, a weight bar, a shock absorber, a delivery device, and a rubber ring plunger connected in sequence, with the rope cap connected to the wire end; Step 2: Seal and install the blowout preventer onto the blowout preventer; Step 3: Lower the rubber ring plunger device into the downhole tubing. When it is in any position in the tubing, quickly disengage it. The rubber ring plunger device falls by its own weight. By opening and closing the well at the wellhead, the formation energy is released to push the plunger upward, so that the water above the plunger is lifted to the surface.

[0016] A further feature of this invention is that step 3 specifically involves, Step 3.1: Close the blowout preventer pressure relief cock, slowly open the test valve, and after filling it, fully open the test valve. After confirming that the main valve is fully open, you can smoothly lower the wire tool string. Lower the plunger to 50m-100m below the large four-way valve. After quickly lowering the wire, brake suddenly. The plunger will disengage from the tool string under the action of inertial force and then fall by itself. Step 3.2: Raise the plunger tool string into the blowout preventer, then close the test valve and remove the plunger tool string; Step 3.3: Install the wellhead shock absorber and blowout preventer; Step 3.4: Set the automatic well opening and closing time, and then set the gas tree production valve to automatically perform periodic drainage operations.

[0017] The beneficial effects of this invention are as follows: The rubber ring plunger device for downhole drainage of natural gas wells provided by this invention can center the steel body inside the tubing through the centering mechanism, and the central axis of the tubing and the central axis of the rubber ring plunger are aligned. The outer circle of the rubber ring and the inner circle of the tubing maintain a very small annular gap, so that water leakage is minimal. It can easily lift the water on the plunger to the surface, and the plunger falls by its own weight. Due to the small gap of the rubber ring, the check valve opens when the plunger falls, allowing water to rise quickly, which facilitates the rapid fall of the plunger and improves drainage efficiency. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the rubber ring plunger device for drainage of natural gas wells according to the present invention; Figure 2 yes Figure 1 Radial cross-section of the upper straightening plate in the AA direction; Figure 3 yes Figure 1 Radial cross-section of the lower centralizer in the BB direction; Figure 4 This is a field experimental comparison diagram of the rubber ring plunger device in well #1 and the polished rod drainage plunger in Embodiment 6 of the present invention; Figure 5 This is a field experiment comparison diagram of the rubber ring plunger device in well #2 and the smooth rod drainage plunger in Embodiment 6 of the present invention.

[0019] In the diagram, 1. Upper connector, 2. Steel ball, 3. Pin, 4. Upper straightening plate, 5. Top spring, 6. Retaining ring, 7. Main body seat, 8. Spacer ring, 9. Rubber ring, 10. Connecting ring, 11. Lower seat, 12. Lower straightening plate, 13. Lower connector. Detailed Implementation

[0020] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0021] Example 1 The rubber ring plunger device for natural gas well drainage provided by this invention has the following structure: Figure 1 As shown, it includes a main body 7, which is a cylindrical tube. An inner through hole is opened axially inside the main body 7. The upper end of the inner through hole is a flared mouth, and a steel ball 2 is placed inside the flared mouth. A rubber ring mechanism is set on the lower part of the main body 7. An upper connector 1 is connected to the upper part of the main body 7. A connecting ring 10, a lower seat 11, and a lower connector 13 are connected in sequence below the main body 7. A straightening mechanism is set on the upper part of the main body 7 and the lower seat 11 around the circumference.

[0022] Example 2 The straightening mechanism includes several upper straightening pieces 4 and lower straightening pieces 12, such as Figure 2 As shown, several longitudinal grooves a are evenly distributed around the upper circumference of the outer wall of the main body 7, and an upper straightening piece 4 is correspondingly arranged in each longitudinal groove a; as shown Figure 3 As shown, several lower centralizing plates 12 are evenly arranged around the outer wall of the lower seat 11, and several longitudinal grooves b are evenly opened around the outer wall of the lower seat 11. Each longitudinal groove b contains a corresponding lower centralizing plate 12. Each upper centralizing plate 4 and lower centralizing plate 12 has the same structure, which is an arc plate. Both ends of the arc plate are provided with contraction steps in the arc extension direction. The upper and lower ends of the contraction steps are flat. Several notches are vertically opened on the straight end face of the arc plate with opposite arcs. The notches are rectangular. Each notch is connected to a top spring 5. Each longitudinal groove a and longitudinal groove b are respectively opened with a connecting hole. The other end of the top spring 5 is installed in the connecting hole. The diameter of the outer arc of the arc surface is consistent with the inner diameter of the oil pipe. The top spring 5 lifts up the upper centralizing plate 4 and the lower centralizing plate 12. The arc surface of the arc plate contacts and fits with the inner surface of the oil pipe to ensure that the plunger runs in the center of the oil pipe.

[0023] Example 3 The rubber ring mechanism includes several rubber rings 9. The middle and lower parts of the outer wall of the main body 7 are provided with extended external threads. The rubber rings 9 are fitted one by one from the lower end of the extended external threads upward. Each rubber ring 9 is threaded with a spacer ring 8 below it. The spacer ring 8 separates two adjacent rubber rings 9 to form a series of evenly spaced rubber rings 9. The spacer ring 8 at the bottom is threaded with a connecting ring 10 below it. The connecting ring 10 locks the rubber ring mechanism.

[0024] The inner diameter of the rubber ring 9 is the same as the outer diameter of the extended external thread. The rubber ring 9 is a sheet-shaped rubber ring. The gap between the outer diameter of the rubber ring 9 and the inner diameter of the oil pipe is 0-0.5mm. The upper and lower sides of the inner circle of the rubber ring 9 are clamped by spacer rings 8 to ensure the seal at the root of the plunger. The outer diameter of the rubber ring 9 is suspended and maintains the minimum gap with the inner diameter of the oil pipe. Because a single rubber ring 9 is thin, easily deformable and has low friction, when it encounters scale or bulges on the inner wall of the oil pipe, it can deform and pass through one by one, and then quickly rebound to continue to maintain the minimum size with the inner wall of the oil pipe.

[0025] Example 4 The upper part of the upper connector 1 is a retrieval neck, which adopts a small-diameter cylindrical structure. The upper part of the retrieval neck has a boss at the bottom that connects to a large-diameter cylindrical structure. The small-diameter cylindrical structure and the large-diameter cylindrical structure are integrally formed. The lower end of the large-diameter cylinder has an inner hole, and the lower end of the inner hole is an enlarged hole structure a. The upper end of the enlarged hole structure a has an internal thread a. The upper outer wall of the main body seat 7 has an external thread a. The external thread a connects to the internal thread a of the upper connector 1, thus threading the main body seat 7 and the upper connector 1 together. A cavity is opened at the upper part of the internal thread a. The cavity connects to the upper flared mouth of the main body seat 7. The inner diameter of the cavity is larger than that of the flared mouth. Two symmetrical radial side holes are opened on the side of the cavity. The steel ball 2 can move upward in the cavity. The outer ring of the steel ball 2 is a water flow space. The water flows out through the two radial side holes.

[0026] The upper part of the main body 7, together with the shrinkage step above the upper centralizer 4 which shrinks in the longitudinal groove a, extends into the expansion structure a of the upper connector 1; a retaining ring 6 is sleeved on the main body 7, the upper end of the retaining ring 6 is an expansion structure b, and an internal thread b is opened below the retaining ring 6. The shrinkage step below the upper centralizer 4 extends into the expansion structure b at the upper end of the retaining ring 6. The outer wall of the main body 7 is correspondingly opened with an external thread b. The internal thread b below the retaining ring 6 is connected to the external thread b of the main body 7. The expansion hole at the upper end of the retaining ring 6 holds the lower shrinkage step of the upper centralizer 4. Each upper centralizer 4 is lifted by the top spring 5, so that the shrinkage steps at both ends of the upper centralizer 4 simultaneously fit with the expansion structure a at the lower end of the upper connector 1 and the expansion structure b at the upper end of the retaining ring 6; ensuring that the outer circle of the upper centralizer 4 matches the inner diameter of the oil pipe.

[0027] Several blind holes a are made opposite to the external thread a and tapped. Pins 3 are inserted into the blind holes a to lock and fix the main body 7 and the upper connector 1 on the basis of the threaded connection.

[0028] Example 5 The lower end of the connecting ring 10 has an enlarged hole structure c, and the inner wall of the enlarged hole structure c is provided with an internal thread c. The lower seat 11 is a cylindrical structure, and the upper outer wall of the lower seat 11 is provided with an external thread c. The internal thread c at the lower end of the connecting ring 10 is connected to the external thread c at the upper part of the lower seat 11. The upper part of the lower seat 11, together with the stepped structure at the upper end of the lower support plate 12 which is contracted in the longitudinal groove b, extends into the enlarged hole structure c at the lower end of the connecting ring 10.

[0029] The upper end of the lower connector 13 has an enlarged hole structure d, and the inner wall of the enlarged hole structure d is provided with an internal thread d. The lower outer wall of the lower seat 11 is provided with an external thread d. The internal thread d at the upper end of the lower connector 13 is connected to the external thread d at the lower part of the lower seat 11. The lower part of the lower seat 11, together with the contraction step at the lower end of the lower stabilizer 12, extends into the enlarged hole structure d at the upper end of the lower connector 13. The enlarged hole at the lower end of the connecting ring 10 holds the contraction step at the upper end of the lower stabilizer 12, and the enlarged hole at the upper end of the lower connector 13 holds the contraction step at the lower end of the lower stabilizer 12. Each lower stabilizer 12 is lifted by the top spring 5, so that the contraction steps at both ends of the lower stabilizer 12 are in contact with the enlarged hole structure c at the lower end of the connecting ring 10 and the enlarged hole structure d at the upper end of the lower connector 13, ensuring that the outer circle of the lower stabilizer 12 matches the inner diameter of the oil pipe.

[0030] Several blind holes b are opened opposite to the internal thread c and tapped. Several blind holes c are opened opposite to the internal thread d and tapped. Pins 3 are inserted into the blind holes b and c and reinforced by the pins 3, so that the main body 7 and the connecting ring 10, and the connecting ring 10 and the lower seat 11 are locked and fixed on the basis of the threaded connection.

[0031] The working principle of the rubber ring plunger device for downhole drainage of natural gas provided by this invention is as follows: A steel ball 2 blocks the upper end of the inner through-hole, forming a one-way valve mechanism. When the main body seat 7 moves downwards, the steel ball 2 moves upwards, opening the one-way valve mechanism. When the main body seat 7 moves upwards, the steel ball 2 moves downwards due to gravity, closing the one-way valve mechanism. A centralizing mechanism, through several upper centralizing plates 4 and lower centralizing plates 12, centers the main body seat 7. Several rubber rings 9 are installed on the main body seat 7, with spacers 8 between them, allowing for convenient up-and-down movement in the downhole tubing. This is suitable for wells with high water content and large gas volume. It utilizes automatic shut-in to store energy by pressurizing the gas layer, and then automatically opens the well to release energy, pushing the plunger to the wellhead, causing most of the water above the plunger to rise to the surface.

[0032] Example 6 The present invention relates to a natural gas well downhole drainage method, which uses a rubber ring plunger device for natural gas well downhole drainage, and is implemented according to the following steps: Step 1: Connect the plunger tool string to the rubber ring plunger device used for drainage of natural gas wells, and use a crane to put the connected plunger tool string into the blowout preventer; the plunger tool string consists of a rope cap, a weight bar, a shock absorber, a delivery device, and a rubber ring plunger connected in sequence, with the rope cap connected to the wire end.

[0033] Step 2: Seal and install the blowout preventer onto the blowout preventer; Step 3: Lower the rubber ring plunger device into the downhole tubing. When it is in any position in the tubing, quickly disengage it. The rubber ring plunger device falls by its own weight. By opening and closing the well at the wellhead, the formation energy is released to push the plunger upward, so that the water above the plunger is lifted to the surface.

[0034] Step 3 specifically involves: Step 3.1: Close the blowout preventer pressure relief cock, slowly open the test valve, and after filling it, fully open the test valve. After confirming that the main valve is fully open, you can smoothly lower the steel wire. Lower the plunger 50m-100m below the large four-way connector. After quickly lowering the steel wire, brake suddenly. The plunger will disengage from the tool string under the action of inertial force and then fall by itself.

[0035] Step 3.2: Raise the plunger tool string into the blowout preventer, then close the test valve and remove the plunger tool string; Step 3.3: Install the wellhead shock absorber and blowout preventer; Step 3.4: Set the automatic well opening and closing time, and then set the gas tree production valve to automatically perform periodic drainage operations.

[0036] When retrieving the rubber ring plunger from the well, manual capture and retrieval at the wellhead can be used, or a wireline from a well test vehicle can be used for retrieval.

[0037] The rubber ring plunger device of this invention for drainage in natural gas wells was compared with the field test results of a polished rod drainage plunger, as follows: Figure 4 As shown, before August 24th, well #1 used a smooth rod drainage plunger, resulting in a gas production of less than 1000 cubic meters per day, indicating that it could not effectively carry fluid and the fluid accumulation in the wellbore was not improved. On August 24th, a rubber ring drainage plunger was installed, with a working cycle of 3 hours on and 9 hours off. Not only did the casing pressure decrease slowly, but the gas production increased to 3500 cubic meters per day, proving that the rubber ring plunger effectively carried fluid through gas lift and that the fluid accumulation in the wellbore was significantly improved.

[0038] like Figure 5 As shown, before July 10th, Well #2 used a smooth rod drainage plunger, with a gas production of approximately 1500 cubic meters per day, indicating a generally average fluid carrying capacity and limited improvement in wellbore fluid accumulation. On July 10th, a rubber ring drainage plunger was installed, with a working cycle of 4 hours open and 11 hours closed. The casing pressure decreased, and the gas production increased to 5000 cubic meters per day, proving that the rubber ring plunger effectively carried fluid through gas lift, and the wellbore fluid accumulation was significantly improved.

[0039] This invention relates to a rubber ring plunger device for downhole drainage of natural gas wells. The upper centralizer 4 and lower centralizer 12 are both fitted against the inner wall of the tubing, ensuring the steel body operates in a centered position. Multiple sheet-like rubber rings form a series. When the main body seat 7 encounters scale or bulges on the tubing wall during its up-and-down movement, the rubber rings 9 easily deform to pass through and immediately rebound, maintaining efficient drainage. Installation into the well is easy, operation is convenient, and drainage is highly efficient. It can seal the tubing at 95% and can easily move up and down within the tubing. In this natural gas well downhole drainage method, the shut-in plunger falls onto the locking device by its own weight, while the opening plunger is pushed upwards by the release of gas layer energy. The rubber rings seal more than 95% of the tubing, resulting in excellent drainage. Combined with an intelligent well-opening and closing system, it provides fully automatic and efficient drainage. It is suitable for all high water-cut wells and natural gas wells with large gas layer energy, capable of withstanding high downhole temperatures and pressures, and applicable to deep well drainage and gas production operations.

Claims

1. A rubber ring piston device for drainage of natural gas wells, characterized in that, The application relates to a centralizer for a coiled tubing, which comprises a main body seat (7) in the shape of a circular tube, an inner through hole is axially arranged in the main body seat (7), the upper end of the inner through hole is a horn mouth, a steel ball (2) is arranged in the horn mouth, a rubber ring mechanism is arranged at the lower part of the outer part of the main body seat (7), an upper connector (1) is connected to the upper part of the main body seat (7), a connecting ring (10), a lower seat (11) and a lower connector (13) are sequentially connected to the lower part of the main body seat (7), and a centralizer mechanism is arranged on the upper part of the main body seat (7) and the lower seat (11).

2. The rubber ring and plunger device for natural gas wellbore drainage according to claim (1), characterized in that, The centralizer mechanism comprises a plurality of upper centralizer pieces (4) and lower centralizer pieces (12), a plurality of longitudinal grooves a are uniformly arranged on the upper part of the outer wall of the main body seat (7) in a circumferential direction, and each upper centralizer piece (4) is arranged in each longitudinal groove a; a plurality of lower centralizer pieces (12) are uniformly arranged on the outer wall of the lower seat (11) in a circumferential direction, a plurality of longitudinal grooves b are uniformly arranged on the outer wall of the lower seat (11) in a circumferential direction, and each lower centralizer piece (12) is arranged in each longitudinal groove b; each upper centralizer piece (4) and each lower centralizer piece (12) are in the same structure and are in the shape of an arc plate, the two ends of the arc plate in the extending direction of the arc are provided with contraction steps, the upper end and the lower end of the contraction step are in the shape of a plane, a plurality of notches are vertically arranged on the straight line end face of the arc plate, a top spring (5) is connected in each notch, a connecting hole is arranged in each longitudinal groove a and each longitudinal groove b, and the other end of the top spring (5) is connected to the connecting hole.

3. The rubber ring and plunger device for natural gas wellbore drainage of claim 2, wherein, The rubber ring mechanism comprises a plurality of rubber rings (9), the middle part and the lower part of the outer wall of the main body seat (7) are provided with lengthened external threads, the rubber rings (9) are sequentially sleeved from the lower end of the lengthened external threads, one spacer ring (8) is threadedly connected below each rubber ring (9), the spacer ring (8) separates the adjacent two rubber rings (9) to form a plurality of uniformly spaced rubber rings (9), and one connecting ring (10) is threadedly connected below the lowermost spacer ring (8) to lock the rubber ring mechanism.

4. The rubber ring and plunger device for natural gas wellbore drainage of claim 3, wherein, The inner diameter of the rubber ring (9) is the same as the outer diameter of the lengthened external thread, the rubber ring (9) is in the shape of a sheet, and the gap between the outer diameter of the rubber ring (9) and the inner diameter of the oil pipe is 0-0.5 mm.

5. The rubber ring and plunger device for natural gas wellbore drainage of claim 4, wherein, The upper part of the upper connector (1) is a fishing neck, the fishing neck is in the structure of a small-diameter cylinder, a boss is arranged on the upper part of the fishing neck to connect a large-diameter cylinder structure, the small-diameter cylinder structure and the large-diameter cylinder structure are integrally formed, an inner hole is arranged at the lower end of the large-diameter cylinder, the lower end of the inner hole is in the structure of an expansion hole a, an inner thread a is arranged at the upper end of the expansion hole a, an outer thread a is arranged on the outer wall of the upper part of the main body seat (7), the outer thread a is connected to the inner thread a of the upper connector (1), the main body seat (7) and the upper connector (1) are threadedly connected, a cavity is arranged at the upper part of the inner thread a, the cavity is communicated with the horn mouth at the upper end of the main body seat (7), the inner diameter of the cavity is larger than that of the horn mouth, and two symmetrical side holes are arranged on the side of the cavity.

6. The rubber ring and plunger device for natural gas wellbore drainage of claim 5, wherein, The upper part of the main seat (7) and the contraction step above the upper centralizer (4) contracted in the longitudinal groove a all extend into the counterbore structure a of the upper joint (1); the main seat (7) is sleeved with a retaining ring (6), the upper end of the retaining ring (6) is a counterbore structure b, an internal thread b is arranged below the retaining ring (6), the contraction step below the upper centralizer (4) extends into the counterbore structure b of the upper end of the retaining ring (6), an external thread b is arranged on the outer wall of the main seat (7) correspondingly, the internal thread b below the retaining ring (6) is connected to the external thread b of the main seat (7), the counterbore structure b of the upper end of the retaining ring (6) holds the contraction step of the lower end of the upper centralizer (4), each upper centralizer (4) is lifted by a top spring (5), so that the contraction steps at the upper and lower ends of the upper centralizer (4) are in contact with the counterbore structure a of the lower end of the upper joint (1) and the counterbore structure b of the upper end of the retaining ring (6) at the same time, and the outer circle of the upper centralizer (4) is matched with the inner diameter of the oil pipe.

7. The rubber ring and plunger device for natural gas wellbore drainage of claim 6, wherein, The lower end of the connecting ring (10) is provided with a counterbore structure c, an internal thread c is arranged on the inner wall of the counterbore structure c, the lower seat (11) is a circular tubular structure, an external thread c is arranged on the outer wall of the upper part of the lower seat (11), the internal thread c of the upper end of the connecting ring 10 is connected to the external thread b arranged on the outer wall of the main seat (7), and the internal thread c of the lower end of the connecting ring 10 is connected to the external thread c of the upper part of the lower seat (11), the upper part of the lower seat (11) and the step structure of the upper end of the lower centralizer (12) contracted in the longitudinal groove b all extend into the counterbore structure c of the lower end of the connecting ring (10).

8. The rubber ring and plunger device for natural gas wellbore drainage of claim 7, wherein, The upper end of the lower joint (13) is provided with a counterbore structure d, an internal thread d is arranged on the inner wall of the counterbore structure d, an external thread d is arranged on the outer wall of the lower part of the lower seat (11), the internal thread d of the upper end of the lower joint (13) is connected to the external thread d of the lower part of the lower seat (11), the lower part of the lower seat (11) and the contraction step of the lower end of the lower centralizer (12) all extend into the counterbore structure d of the upper end of the lower joint (13), the counterbore structure of the lower end of the lower centralizer (12) holds the contraction step of the upper end of the lower centralizer (12), the counterbore structure of the lower end of the lower centralizer (12) holds the contraction step of the lower end of the lower centralizer (12), each lower centralizer (12) is lifted by a top spring (5), so that the contraction steps at the upper and lower ends of the lower centralizer (12) are in contact with the counterbore structure c of the lower end of the connecting ring (10) and the counterbore structure d of the upper end of the lower joint (13) at the same time, and the outer circle of the lower centralizer (12) is matched with the inner diameter of the oil pipe; the external thread a and the internal thread a are oppositely provided with a plurality of blind holes a and are tapped, the internal thread c and the external thread c are oppositely provided with a plurality of blind holes b and are tapped, and the internal thread d and the external thread d are oppositely provided with a plurality of blind holes c and are tapped, and the blind holes a, the blind holes b and the blind holes c are all inserted with the pins (3).

9. A method for automatic water drainage in a natural gas well, characterized in that, The rubber ring plunger device for natural gas downhole drainage is used, and the following steps are specifically implemented: Step 1, connect the rubber ring plunger device for natural gas downhole drainage with the plunger tool string, and put the connected plunger tool string into the blowout preventer pipe by using a crane; the plunger tool string is connected by a rope cap, a weighted rod, a jar, a launcher and a rubber ring plunger in sequence; Step 2, seal and install the blowout preventer pipe to the blowout preventer; Step 3, the rubber ring plunger device is lowered into the downhole tubing, and is quickly separated at any position in the tubing, the rubber ring plunger device falls by gravity, the wellhead is closed to release the formation energy to push the plunger to move upward, and the water above the plunger is lifted to the ground.

10. The method of claim 9, wherein, Step 3 is specifically, Step 3.1, close the blowout pipe pressure relief cock, slowly open the test valve, flush, fully open the test valve, and confirm that the total valve is fully open, then smoothly lower the steel wire, lower the plunger to 50-100 m below the large four-way joint, quickly lower the steel wire and brake, the plunger separates from the tool string under the action of inertial force, and then falls by itself; Step 3.2, raise the plunger tool string into the blowout pipe, then close the test valve, and lift the plunger tool string; Step 3.3, install the wellhead shock absorption blowout pipe; Step 3.4, set the automatic well opening and closing time, then open the gas tree production valve, and automatically perform periodic drainage operation.

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