Plunger drainage gas recovery device and method

Abstract

According to the plunger drainage and gas production device and method, a plunger is arranged in an oil gas well oil pipe and located above a buffer, liquid located above the plunger and gas located below the plunger are contained in the oil gas well oil pipe, and the plunger can move between a clamping device and a blowout prevention pipe; the ground pipeline is connected with an oil-gas well oil pipe through a wellhead Christmas tree; the oil-gas well switch is pneumatically arranged between the surface pipeline and the blowout prevention pipe to control a wellhead Christmas tree; the liquid level sensor is arranged on a ground pipeline to measure the liquid level in real time; the plunger controller is connected with the liquid level sensor and the pneumatic valve, and when the liquid level height reaches a limit value, the plunger controller controls the pneumatic valve to open a wellhead Christmas tree oil-gas well switch; the portion, above the plunger, of the oil pipe is communicated with a ground pipeline so that pressure difference can be formed on the upper portion and the lower portion of the plunger to push the plunger and liquid on the plunger to move towards a wellhead and be discharged to the ground pipeline, and the pressure difference is decreased until the liquid level rises again. According to the device, the lifting opportunity and the liquid lifting amount are optimized.

Description

Technical Field

[0001] The present invention relates to the technical field of downhole plunger gas lift liquid drainage, and particularly relates to a plunger drainage gas production device and method. Background Art

[0002] As the development of tight gas reservoir blocks enters the middle and late stages, the pressure of old wells continuously decreases, the number of low-production and low-efficiency wells increases year by year, the average casing pressure of gas wells in the block shows a downward trend, the proportion of low-production and low-efficiency wells in the total number of wells in the block continuously increases. Along with the reduction of the liquid-carrying capacity of old wells, the water-gas ratio in the production process increases year by year. Generally, a single well shows the characteristics of an increased oil-casing pressure difference, large production fluctuations, and rapid decline. Wellbore liquid accumulation has seriously affected the normal production of gas wells and restricted the sustainable and efficient development of gas fields. At present, the drainage and production process no longer meets the drainage requirements of gas wells in the middle and late stages of high-water-cut gas well production. There is an urgent need to carry out technical research on high-water-cut gas well treatment technology to help old wells resume production and new wells achieve high production.

[0003] The plunger gas lift liquid drainage process uses the plunger as the mechanical interface between gas and liquid, and utilizes the gas produced by the gas well to push the plunger to move up and down periodically in the tubing, thereby lifting the liquid produced from the formation to the ground and producing gas. This method can effectively reduce the "slip" effect in the process of liquid running from the bottom of the well to the wellhead, and greatly improve the efficiency of lifting liquid. Although the existing plunger gas lift can lift the wellbore liquid accumulation and improve the gas well production, the remote control rate is low, the workload of manual parameter adjustment and analysis management is large, and the accuracy is relatively low.

[0004] The above information disclosed in the background art is only used to enhance the understanding of the background of the present invention, and therefore may include information that does not constitute the prior art known to those of ordinary skill in the art. Summary of the Invention

[0005] The purpose of the present invention is to provide a plunger drainage gas production device and method, which are convenient and stable to install, can monitor and track the position of the dynamic liquid level in the wellbore in real time, and realize the autonomous and quantitative drainage of the plunger and the continuous gas production of the gas well without shutting down the well, thereby improving the control level of the plunger gas lift process and reducing the labor cost.

[0006] In order to achieve the above purpose, the present invention provides the following technical solutions:

[0007] A plunger drainage gas production device of the present invention includes:

[0008] An oil and gas well tubing, which is sleeved in a casing,

[0009] A retainer, which is fixed in the oil and gas well tubing;

[0010] A buffer, which is arranged in the oil and gas well tubing and located on the retainer,

[0011] Wellhead production tree, which is sleeved on the casing and connected to the oil and gas well tubing. The wellhead production tree includes an oil and gas well switch that can be switched on and off to connect to the oil and gas well tubing.

[0012] Blowout preventer pipe, which communicates the wellhead production tree and the oil and gas well tubing.

[0013] Plunger, which is arranged inside the oil and gas well tubing and above the buffer. There is liquid above the plunger and gas below the plunger inside the oil and gas well tubing. The plunger is movable between the catcher and the blowout preventer pipe.

[0014] Surface pipeline, which can be connected to and disconnected from the oil and gas well tubing via the wellhead production tree.

[0015] Pneumatic valve, which is arranged between the surface pipeline and the blowout preventer pipe to control the oil and gas well switch of the wellhead production tree.

[0016] Liquid level sensor, which is arranged on the surface pipeline to measure the liquid level height in real time.

[0017] Plunger controller, which is connected to the liquid level sensor and the pneumatic valve. When the liquid level height reaches the limit value, the plunger controller controls the pneumatic valve to open the oil and gas well switch of the wellhead production tree. The tubing above the plunger is connected to the surface pipeline, so that a pressure difference is formed between the upper and lower parts of the plunger to push the plunger and the liquid above it towards the wellhead and discharge them into the surface pipeline. The pressure difference then decreases until the liquid level rises again.

[0018] In the described plunger drainage gas production device, the plunger controller controls the liquid level height value for closing the oil and gas well. The liquid level height value is the rising amplitude of the liquid level after it changes from decreasing to rising after the oil and gas well is opened.

[0019] In the described plunger drainage gas production device, the plunger drainage gas production device is provided with a pressure sensor for measuring the casing pressure of the oil and gas well tubing. The pressure differential rise value P of the casing pressure is equal to ρgh, where ρ represents the density of the liquid accumulation in the wellbore, g is a constant, and h is the height of the liquid accumulation in the wellbore as the liquid level height value.

[0020] In the described plunger drainage gas production device, the blowout preventer pipe is provided with a plunger capture device for capturing the plunger.

[0021] In the described plunger drainage gas production device, the blowout preventer pipe is provided with a blowout preventer cap.

[0022] In the described plunger drainage gas production device, the wellhead production tree includes a gas-liquid separator.

[0023] In the described plunger drainage gas production device, the pneumatic valve is a pneumatic diaphragm valve.

[0024] In the described plunger drainage gas production device, the pneumatic diaphragm valve is connected to the plunger controller by an electric wire.

[0025] In the described plunger drainage and gas production device, the retainer is clamped in the oil and gas well tubing in a concave-convex fit manner.

[0026] The control method of the plunger drainage and gas production device includes

[0027] Step 1: Lower a retainer, a buffer, and a plunger into the oil and gas well tubing in sequence. Connect a blowout preventer pipe to the top of the wellhead Christmas tree. The plunger moves between the retainer and the blowout preventer pipe. At the same time, install a pneumatic valve for controlling the opening and closing of the oil and gas well between the surface pipeline and the blowout preventer pipe. The pneumatic valve is connected to the plunger controller by an electric wire, and the plunger controller realizes the opening and closing operations of the oil and gas well by controlling the opening and closing of the pneumatic valve.

[0028] Step 2: Install a liquid level sensor in the surface pipeline to measure the liquid level height in real time. When it is detected that the liquid level height reaches the preset value, the liquid level sensor sends the preset value to the plunger controller. The plunger controller controls the pneumatic valve to open the oil and gas well switch of the wellhead Christmas tree, and the tubing above the plunger is connected to the surface pipeline, so that a pressure difference is formed between the upper and lower parts of the plunger to push the plunger and the liquid above it towards the wellhead and discharge them into the surface pipeline. The pressure difference then decreases until the liquid level rises again. If it is the first production cycle to control the opening of the well, the preset value is any arbitrarily set value; if it is other production cycles to control the opening of the well, the preset value is the liquid level height corresponding to 1.5 times the surface pipeline pressure during the well closure period of the previous production cycle.

[0029] Step 3: Set the liquid level height value used by the plunger controller to control the well closure of the oil and gas well. This liquid level height value is the rising amplitude of the liquid level after it changes from decreasing to rising after the oil and gas well is opened. The plunger controller receives the liquid level height value for controlling the well closure of the oil and gas well measured by the liquid level sensor, and the oil and gas well is closed.

[0030] In the above technical solution, the plunger drainage and gas production device provided by the present invention has the following beneficial effects: controlling the opening or closing of the oil and gas well according to the change of the liquid level height of the liquid accumulation in the gas well casing, closely combining with the liquid accumulation situation of the oil and gas well, ensuring the best liquid lifting volume, and realizing the automatic control management of the plunger gas lift drainage and gas production process. It can ensure the best lifting timing and the optimal liquid lifting volume of the gas well, and provides an effective way for the automatic plunger drainage and production of the gas well. Description of the Drawings

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required to be used in the embodiments. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings.

[0032] Figure 1The front view schematic diagram of a plunger drainage gas production device provided by an embodiment of the present invention.

[0033] Figure 2 The drainage and production schematic diagram of a control method for a plunger drainage gas production device provided by an embodiment of the present invention. Specific embodiments

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0035] Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed present invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0036] It should be noted that similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0037] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be construed as a limitation of the present invention.

[0038] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "a plurality" means two or more unless otherwise specifically defined.

[0039] In the present invention, unless otherwise clearly defined and limited, terms such as "installed", "connected", "joined", "fixed", etc. shall be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be directly connected, or indirectly connected through an intermediate medium, and it may be the communication inside two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0040] In the present invention, unless otherwise clearly defined and limited, the first feature being "on" or "under" the second feature may include the direct contact between the first and second features, or may include the situation where the first and second features are not in direct contact but in contact through additional features therebetween. Moreover, the first feature being "above", "over" and "on top of" the second feature includes that the first feature is directly above and obliquely above the second feature, or simply means that the horizontal height of the first feature is higher than that of the second feature. The first feature being "under", "beneath" and "underneath" the second feature includes that the first feature is directly below and obliquely below the second feature, or simply means that the horizontal height of the first feature is lower than that of the second feature.

[0041] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0042] See Figure 1-2 As shown, in one embodiment, a plunger drainage gas production device of the present invention includes

[0043] An oil and gas well tubing 2, which is sleeved inside a casing 3,

[0044] A retainer 1, which is fixed inside the oil and gas well tubing 2;

[0045] A buffer 4, which is arranged inside the oil and gas well tubing 2 and located on the retainer 1,

[0046] A wellhead Christmas tree 5, which is sleeved on the casing 3 and connected to the oil and gas well tubing 2. The wellhead Christmas tree 5 includes a wellhead switch that can be switched on and off to connect to the oil and gas well tubing 2,

[0047] A blowout preventer pipe 6, which communicates the wellhead Christmas tree 5 and the oil and gas well tubing 2,

[0048] A plunger 7, which is arranged inside the oil and gas well tubing 2 and located above the buffer 4. There is liquid above the plunger 7 and gas below the plunger 7 inside the oil and gas well tubing 2. The plunger 7 can move between the retainer 1 and the blowout preventer pipe 6,

[0049] A surface pipeline 8, which can be connected to and disconnected from the oil and gas well tubing 2 via the wellhead Christmas tree 5,

[0050] A pneumatic valve 9 is provided between the surface pipeline 8 and the blowout preventer pipe 6 to control the opening and closing of the oil and gas well of the wellhead Christmas tree 5.

[0051] A liquid level sensor 10 is provided on the surface pipeline 8 to measure the liquid level height in real time.

[0052] A plunger controller 11 is connected to the liquid level sensor 10 and the pneumatic valve 9. When the liquid level height reaches a limit value, the plunger controller 11 controls the pneumatic valve 9 to open the oil and gas well switch of the wellhead Christmas tree 5, and the tubing above the plunger is connected to the surface pipeline 8, so that a pressure difference is formed between the upper and lower parts of the plunger to push the plunger and the liquid above it towards the wellhead and discharge it to the surface pipeline 8, and the pressure difference then decreases until the liquid level rises again.

[0053] In a preferred embodiment of the described plunger drainage gas production device, the plunger controller 11 controls the liquid level height value for closing the oil and gas well, and the liquid level height value is the rising amplitude of the liquid level after it changes from decreasing to rising after the oil and gas well is opened.

[0054] In a preferred embodiment of the described plunger drainage gas production device, the plunger drainage gas production device is provided with a pressure sensor for measuring the casing pressure of the oil and gas well tubing 2. The pressure micro-increase value P of the rising casing pressure is equal to ρgh, where ρ represents the density of the liquid accumulation in the wellbore, g is a constant, and h is the height of the liquid accumulation in the wellbore as the liquid level height value.

[0055] In a preferred embodiment of the described plunger drainage gas production device, the blowout preventer pipe 6 is provided with a plunger capture device 12 for capturing the plunger.

[0056] In a preferred embodiment of the described plunger drainage gas production device, the blowout preventer pipe 6 is provided with a blowout preventer cap 13.

[0057] In a preferred embodiment of the described plunger drainage gas production device, the wellhead Christmas tree 5 includes a gas-liquid separator 14.

[0058] In a preferred embodiment of the described plunger drainage gas production device, the pneumatic valve 9 is a pneumatic diaphragm valve.

[0059] In a preferred embodiment of the described plunger drainage gas production device, the pneumatic diaphragm valve is connected to the plunger controller 11 by an electric wire.

[0060] In a preferred embodiment of the described plunger drainage gas production device, the retainer 1 is snap-fitted into the oil and gas well tubing 2.

[0061] In one embodiment, when lowering the oil and gas well tubing 2, it is necessary to avoid excessive deformation of the oil and gas well tubing 2, which may cause the retainer 1 to fall off from the inside of the oil and gas well tubing 2 and drop to the bottom of the casing 3. Therefore, an anti-drop structure is provided inside the oil and gas well tubing 2. The anti-drop structure is located below the retainer 1 to prevent the retainer from falling off, and the anti-drop structure is a dissolvable structure.

[0062] In one embodiment, a control method for a plunger drainage gas production device includes,

[0063] Step 1: Lower the retainer 1, the buffer 4, and the plunger into the oil and gas well tubing 2 in sequence. Connect the top of the wellhead production tree 5 to the blowout preventer pipe 6. The plunger 7 moves between the retainer 1 and the blowout preventer pipe 6. At the same time, a pneumatic valve 9 for controlling the opening and closing of the oil and gas well is provided between the surface pipeline 8 and the blowout preventer pipe 6. The pneumatic valve 9 is connected to the plunger controller 11 by an electric wire. The plunger controller 11 realizes the opening and closing operation of the oil and gas well by controlling the opening and closing of the pneumatic valve 9.

[0064] Step 2: A liquid level sensor 10 is provided in the surface pipeline 8 to measure the liquid level height in real time. When it is detected that the liquid level height reaches a preset value, the liquid level sensor 10 sends the preset value to the plunger controller 11. The plunger controller 11 controls the pneumatic valve 9 to open the oil and gas well switch of the wellhead production tree 5, and the tubing above the plunger is connected to the surface pipeline 8, so that a pressure difference is formed between the upper and lower parts of the plunger to push the plunger and the liquid above it towards the wellhead and discharge it to the surface pipeline 8. The pressure difference then decreases until the liquid level rises. If it is the first production cycle to control the opening of the well, the preset value is any arbitrarily set value; if it is other production cycles to control the opening of the well, the preset value is the liquid level height corresponding to 1.5 times the pressure of the surface pipeline 8 during the well closure period of the previous production cycle.

[0065] Step 3: Set the liquid level height value for the plunger controller 11 to control the closure of the oil and gas well. This liquid level height value is the rising amplitude of the liquid level after it changes from decreasing to rising after the oil and gas well is opened. The plunger controller 11 receives the liquid level height value for controlling the closure of the oil and gas well measured by the liquid level sensor 10, and the oil and gas well is closed.

[0066] In one embodiment, a control method for a plunger drainage gas production device includes,

[0067] Step 1: Circulate the well. Lower the buffer retainer 1 and the plunger into the oil and gas well tubing 2 in sequence. Connect the top of the wellhead gas production tree or the wellhead production tree 5 to the blowout preventer pipe 6. The plunger 7 moves between the buffer retainer 1 and the blowout preventer pipe 6. At the same time, a pneumatic diaphragm valve for controlling the opening and closing of the oil and gas well is provided between the surface pipeline 8 and the blowout preventer pipe 6. The pneumatic diaphragm valve is connected to the plunger controller 11 by an electric wire. The plunger controller 11 realizes the opening and closing operation of the oil and gas well by controlling the opening and closing of the pneumatic diaphragm valve. The buffer retainer 1 is a retainer 1 with a buffer spring.

[0068] Step 2: Set a liquid level sensor 10 at the wellhead to measure the liquid level height and transmit this value to the plunger controller 11.

[0069] Step 3: Set the liquid level height value for the plunger controller 11 to control the well shut-in. This value is the liquid level rise amplitude value after the casing pressure changes from decreasing to increasing after the oil and gas well is opened.

[0070] Step 4: The plunger controller 11 receives the liquid level signal measured by the liquid level sensor 10, and then controls the opening and closing of the oil and gas well according to the set opening and closing conditions of the oil and gas well.

[0071] In one embodiment, the control method of the plunger drainage gas production device includes

[0072] Step 1: Run a drift to the tubing 2 of the oil and gas well, successively lower a buffer catcher 1 and a plunger into the tubing, connect a blowout preventer pipe 6 to the top of the wellhead gas production tree or wellhead oil production tree 5, and the plunger moves between the buffer catcher 1 and the blowout preventer pipe 6; at the same time, set a pneumatic diaphragm valve for controlling the opening and closing of the oil and gas well between the surface pipeline 8 and the blowout preventer pipe 6. This pneumatic diaphragm valve is connected to the plunger controller 11 by an electric wire, and the plunger controller 11 realizes the opening and closing operation of the oil and gas well by controlling the opening and closing of the pneumatic diaphragm valve.

[0073] Step 2: Set a liquid level sensor 10 in the surface pipeline 8 to accurately measure the liquid level height. This sensor can monitor the change of the liquid level in real time. Once the detected liquid level height reaches the preset value, the sensor will immediately transmit this value to the plunger controller 11.

[0074] Step 3: Set the liquid level height value for the plunger controller 11 to control the opening of the oil and gas well. If it is to control the opening in the first production cycle, the opening liquid level height value is any set value; if it is to control the opening in other production cycles, the opening liquid level height value is the liquid level height value corresponding to 1.5 times the pressure of the surface pipeline 8 during the well shut-in period of the previous production cycle.

[0075] Step 4: Set the liquid level height value for the plunger controller 11 to control the well shut-in of the oil and gas well. This liquid level height value is the rise amplitude after the liquid level changes from decreasing to increasing after the oil and gas well is opened. This rise amplitude is calculated by the formula ρgh, where ρ represents the density of the liquid accumulation in the wellbore, g is a constant, and h is the liquid accumulation height in the wellbore.

[0076] Step 5: The plunger controller 11 receives the liquid level height value signal measured by the liquid level sensor 10, and then controls the opening and closing of the oil and gas well according to the preset opening and closing conditions of the oil and gas well. The opening and closing conditions of the present invention are set according to the change trend of the liquid level of the oil and gas well. At the same time, the opening time and the closing time are restricted by the maximum opening and closing time and the minimum opening and closing time.

[0077] In one embodiment, as Figure 2As shown, when the liquid level height measured by the liquid level sensor 10 reaches the limit value, the plunger controller 11 receives the signal and completes the automatic well opening operation. After the well is opened, the tubing above the plunger is connected to the gas well's external transmission pipeline. A pressure difference is formed above and below the plunger, and this pressure difference provides the power to push the plunger and the liquid above it towards the wellhead, lifting the bottom-hole liquid accumulation to the ground and discharging it from the wellbore. At the same time, the gas accumulated downhole during this reciprocating motion cycle also enters the gas well's external transmission pipeline. After the well is opened, the initial casing pressure will rapidly drop, the liquid level will drop, and later there will be a gradual and slight rise. The specific reason is that as the well-opening time lengthens, new liquid accumulation will be generated in the tubing under the action of the pressure difference. After the pressure difference drops to zero, the liquid level stabilizes, the casing pressure stops dropping, and starts to rise slightly. The liquid level reaches the highest, and the afterflow in the wellbore is completed.

[0078] Combined with the actual production situation of the gas well, taking the maximum gas production rate and the most effective liquid-lifting volume as the premise, for the slight rise state of the casing pressure, calculate the specific pressure micro-rise value; generally in the well-opening state, when the rise amplitude value of the casing pressure reaches 0.1 Mpa, start to close the well for recovery. According to P = ρgh, where ρ is the density of the liquid accumulation in the wellbore, g is a constant, and h is the height of the liquid accumulation in the wellbore, that is, when the pressure rises slightly by 0.1 MPa and the height of the liquid accumulation in the wellbore is 10 m, close the well. When the rise amplitude of the liquid accumulation in the wellbore exceeds the micro-rise value of the liquid accumulation in the wellbore set in this mode, the plunger controller 11 controls the gas well to close until the next production cycle to control the well opening again.

[0079] In one embodiment, by observing the micro-rise value of the liquid level after closing the well, set the well-opening and well-closing timing. The well-opening casing pressure of this well is set at 1.5 times the pressure of the surface pipeline 8, that is, 2.7 MPa, and the micro-rise value of the liquid level is set at 1.5 m. After the setting is completed, start to run. After the plunger gas lift system runs for 72 hours, export the production data, as shown in Table 1.

[0080] As can be seen from Table 1, the casing pressure at the well-opening moment is 2.7 MPa, meeting the preset well-opening conditions; the micro-rise value of the liquid level at the well-closing moment is 1.5 m, meeting the preset well-closing conditions. In this mode, the plunger controller 11 automatically adjusts the well opening and closing according to the liquid level change situation, and the production system is in an automatically optimized state.

[0081] Table 1:

[0082]

[0083]

[0084] In summary, the present invention is closely combined with the liquid accumulation situation of the gas well, can ensure the best lifting timing and the optimal liquid-lifting volume of the gas well, and provides effective management measures and ways for the automatic plunger drainage of the gas well.

[0085] Finally, it should be noted that the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of protection of the present application.

[0086] Only some exemplary embodiments of the present invention have been described above by way of illustration. Without doubt, for those of ordinary skill in the art, the described embodiments can be modified in various different ways without departing from the spirit and scope of the present invention. Therefore, the above drawings and description are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A plunger drainage gas production device, characterized in that, It includes, an oil and gas well tubing, which is sleeved inside a casing; a retainer, which is clamped inside the oil and gas well tubing; a buffer, which is arranged inside the oil and gas well tubing and located on the retainer; a wellhead production tree, which is sleeved on the casing and connected to the oil and gas well tubing, and the wellhead production tree includes an oil and gas well switch that can be connected and disconnected from the oil and gas well tubing; a blowout preventer pipe, which communicates the wellhead production tree and the oil and gas well tubing; a plunger, which is arranged inside the oil and gas well tubing and above the buffer, there is liquid above the plunger and gas below the plunger inside the oil and gas well tubing, and the plunger is movable between the retainer and the blowout preventer pipe; a surface pipeline, which can be connected and disconnected from the oil and gas well tubing via the wellhead production tree; a pneumatic valve, which is arranged between the surface pipeline and the blowout preventer pipe to control the oil and gas well switch of the wellhead production tree; a liquid level sensor, which is arranged on the surface pipeline to measure the liquid level height in real time; a plunger controller, which is connected to the liquid level sensor and the pneumatic valve. When the liquid level height reaches a limit value, the plunger controller controls the pneumatic valve to open the oil and gas well switch of the wellhead production tree, and the tubing above the plunger is connected to the surface pipeline, so that a pressure difference is formed between the upper and lower parts of the plunger to push the plunger and the liquid above it towards the wellhead and discharge them into the surface pipeline, and the pressure difference then decreases until the liquid level rises.

2. The plunger drainage gas production device according to claim 1, characterized in that The liquid level height value at which the plunger controller controls the oil and gas well to shut in is the rising amplitude of the liquid level after the liquid level drops and then rises after the oil and gas well is opened.

3. The plunger drainage gas production device according to claim 2, characterized in that, The plunger drainage gas production device is provided with a pressure sensor for measuring the casing pressure of the oil and gas well tubing. The pressure micro-increase value P of the rising casing pressure is equal to ρgh, where ρ represents the density of the liquid accumulation in the wellbore, g is a constant, and h is the height of the liquid accumulation in the wellbore as the liquid level height value.

4. A plunger drainage gas production device according to claim 1, characterized in that The blowout preventer pipe is provided with a plunger capture device for capturing the plunger.

5. A plunger drainage gas production device according to claim 1, characterized in that, The blowout preventer pipe is provided with a blowout preventer cap.

6. A plunger drainage gas production device according to claim 1, characterized in that, The wellhead production tree includes a gas-liquid separator.

7. The plunger drainage gas production device according to claim 1, characterized in that, The pneumatic valve is a pneumatic diaphragm valve.

8. The plunger drainage gas production device according to claim 1, characterized in that, The pneumatic diaphragm valve is connected to the plunger controller by an electric wire.

9. A plunger drainage gas production device according to claim 1, characterized in that, The retainer is clamped inside the oil and gas well tubing in an engaging and disengaging manner.

10. A control method for a plunger drainage gas production device according to any one of claims 1-9, characterized in that, It includes, Step 1: Lower a retainer, a buffer, and a plunger into the oil and gas well tubing in sequence. The top of the wellhead production tree is connected to the blowout preventer pipe, and the plunger moves between the retainer and the blowout preventer pipe; at the same time, a pneumatic valve for controlling the oil and gas well switch is arranged between the surface pipeline and the blowout preventer pipe, and the pneumatic valve is connected to the plunger controller by an electric wire. The plunger controller realizes the opening and closing operation of the oil and gas well switch by controlling the opening and closing of the pneumatic valve; Step 2: A liquid level sensor is arranged in the surface pipeline to measure the liquid level height in real time. When it is detected that the liquid level height reaches a preset value, the liquid level sensor sends the preset value to the plunger controller. The plunger controller controls the pneumatic valve to open the oil and gas well switch of the wellhead production tree, and the tubing above the plunger is connected to the surface pipeline, so that a pressure difference is formed between the upper and lower parts of the plunger to push the plunger and the liquid above it towards the wellhead and discharge them into the surface pipeline, and the pressure difference then decreases until the liquid level rises. If it is the first production cycle to control the well opening, the preset value is any arbitrarily set value; if it is other production cycles to control the well opening, the preset value is the liquid level height corresponding to 1.5 times the surface pipeline pressure during the well shut-in period of the previous production cycle. Step 3: Set the liquid level height value for the plunger controller to control the shut-in of the oil and gas well. This liquid level height value is the recovery amplitude after the liquid level rises after the oil and gas well is opened. The plunger controller receives the liquid level height value for controlling the shut-in of the oil and gas well measured by the liquid level sensor, and the oil and gas well is shut in.

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