Plunger gas lift and foam drainage combined water drainage and gas recovery device and method

Abstract

The invention belongs to the field of ultra-deep gas well drainage gas recovery process equipment, and relates to a plunger gas lift and foam drainage combined drainage gas recovery method, a control system controls a trapper to release a plunger, a gas well starts to enter a well shut-in pressure recovery stage, and two processes of plunger falling and pressure recovery are completed; the clamp holder is opened to release the foam discharging rod; when the casing pressure recovers to the maximum casing pressure, the valve is opened, the gas well enters a well opening gas lift stage, the plunger ascends to discharge liquid, and the liquid is discharged through the separator; when the liquid column above the plunger begins to discharge, the oil pressure begins to rise; after the liquid column above the plunger is completely discharged, the gas well enters a continuous production stage, and three processes of mass production of gas, stable follow flow and shaft liquid accumulation are completed; in the process of mass production of gas, stable follow current and wellbore liquid accumulation, monitoring is completed through a flowmeter and a pressure sensor, and monitoring data are transmitted to a control system. The combination of the plunger gas lift process and the foam drainage process can achieve a better drainage gas recovery effect.

Description

Technical Field

[0001] The present invention belongs to the field of drainage gas production process equipment for ultra-deep gas wells, and particularly relates to a drainage gas production device and method combining plunger gas lift and foam drainage. Background Art

[0002] In order to meet the drainage production requirements of ultra-deep wells, during mechanical drainage production, the pump setting depth can only be continuously increased. Since the pump setting depth directly affects the pump efficiency, when the pump setting depth increases, the production efficiency will decrease accordingly. Therefore, the difficulty of artificial lift oil production is increasing, and the production cost is getting higher and higher. In terms of the current development level of artificial lift technology, it is difficult to achieve the exploitation of deep wells over 4000m using a single artificial lift method. Therefore, an important problem faced by the artificial lift method is how to change the development direction of the process technology to make it more composite, energy-efficient, and meet the exploitation needs of ultra-deep wells.

[0003] Combining the plunger gas lift process and the foam drainage process for drainage gas production is an important drainage gas production method for ultra-deep gas wells. The plunger gas lift process forms a mechanical interface between the lifting gas and the lifted liquid using a plunger, reducing gas channeling and liquid fallback, and improving the efficiency of lifting the liquid; the foam drainage process injects a certain amount of foaming agent into the bottom of the well to generate a large amount of low-density water-containing foam, which is carried from the bottom of the well to the ground with the gas flow to achieve the purpose of removing the liquid accumulation at the bottom of the well. Combining the plunger gas lift process and the foam drainage process can, on the one hand, increase the lifting depth of the plunger gas lift process to meet the drainage gas production requirements of ultra-deep gas wells; on the other hand, it can extend the production time of the gas well when it is open, improve the production efficiency; on the other hand, it can reduce the casing-tubing pressure difference and reduce the requirement for the plunger running speed. After retrieval, the patent application "An integrated composite gas production method combining plunger gas lift and foam drainage" with the application number "201710129344.6" makes the foam drainage rod into the shape of a plunger for composite gas production. The patent application "A foam and plunger gas lift combined drainage gas production method and device" with the application number "201711052889.8" generates foam by embedding a foam drainage rod in the plunger, only using the foam generated by the foam drainage process to assist the plunger gas lift to reduce slippage and improve the lifting efficiency, but the lifting efficiency is still not high, the process lifting depth is low, and it cannot perform precise intelligent control on the gas well.

[0004] However, there is currently no effective drainage gas production process for the combined replacement lift of "plunger gas lift" and "foam drainage". Summary of the Invention

[0005] The purpose of the present invention is to provide a drainage gas production device and method combining plunger gas lift and foam, which solves the problem that the existing technology cannot perform precise intelligent control on gas wells.

[0006] The present invention is realized through the following technical solutions:

[0007] The present invention discloses a drainage gas production device combining plunger gas lift and foam drainage, which includes a control system, a wellhead device and a downhole device;

[0008] The wellhead device includes a housing, a gas transmission pipeline and a liquid drainage pipeline; a gas flowmeter is provided on the gas transmission pipeline, a liquid flowmeter is provided on the liquid drainage pipeline, and the gas flowmeter and the liquid flowmeter are connected to the control system;

[0009] A plunger and a foam drainage rod clamped below the plunger are installed in the housing; a gate valve is provided below the housing, and the gate valve is connected to the control system;

[0010] The downhole device includes a tubing pressure sensor arranged on the tubing, a casing pressure sensor arranged on the casing, and the tubing pressure sensor and the casing pressure sensor are connected to the control system;

[0011] The control system is used to calculate the maximum casing pressure when the plunger rises to the wellhead, and control the opening time of the gas well by determining the casing pressure required for the plunger to rise to the wellhead.

[0012] Further, the wellhead device further includes a gathering and transportation pipeline and a separator. One side of the tubing is connected to the separator through the gathering and transportation pipeline via a valve. The outlets of the separator are respectively the gas transmission pipeline and the liquid drainage pipeline;

[0013] The lower end of the housing is a placement window for installing the foam drainage rod;

[0014] A catcher and a fishing head are installed above the plunger. The lower part of the plunger is connected to a gripper. The gate valve is arranged below the placement window and is connected to the tubing;

[0015] The downhole device further includes a buffer and a retainer. The retainer is fixed on the inner wall of the tubing, and the buffer is fixed above the retainer;

[0016] A tubing temperature sensor is also provided on the tubing, and a casing temperature sensor is also provided on the casing.

[0017] Further, the gate valve is used to control the pressure after the valve. After the plunger is caught by the catcher, it is controlled to be in a closed state by the control system; at this time, the foam drainage rod is installed in the placement window, and the gate valve is controlled to be in an open state by the control system during the downward movement stage of the plunger.

[0018] Further, to calculate the maximum casing pressure when the plunger rises to the wellhead, specifically: first calculate the casing pressure P required for the plunger to rise to the wellhead according to the following formula c , and then calculate the maximum casing pressure P c according to P cmax ;

[0019] P c = Pt +(P lh +P lf )W+P p +P f ;

[0020] In the formula: P t is the oil pressure;

[0021] P lh is the liquid column pressure of the liquid slug for lifting 1 m 3 ;

[0022] P lf is the frictional pressure of the liquid slug for lifting 1 m 3 ;

[0023] W is the periodic displacement;

[0024] P p is the pressure generated by the weight of the plunger;

[0025] P f is the frictional resistance of the gas below the plunger.

[0026] Furthermore, since the casing pressure P when the plunger just rises to the wellhead c is the pressure of the annular gas under the maximum casing pressure expansion, and the maximum casing pressure P cmax refers to the casing pressure that the plunger must reach to start ascending. When ignoring the influence of the gas deviation factor on gas expansion, the maximum casing pressure P cmax is:

[0027]

[0028] In the formula: A t is the tubing area; A c is the area of the casing (10), and k is the safety factor.

[0029] Furthermore, the calculation formula for the liquid column pressure P 3 of the liquid slug for lifting 1 m lh is:

[0030]

[0031] The calculation formula for the frictional pressure P 3 of the liquid slug for lifting 1 m lf is:

[0032]

[0033] Among them, f l is the frictional coefficient of the liquid column above the plunger; ρ l is the liquid density; v p is the running speed of the plunger; d tis the tubing diameter; A t is the tubing area;

[0034] The gas friction P at the lower part of the plunger f has the following expression:

[0035]

[0036] where ρ g is the gas density; f g is the gas friction coefficient; v p is the operating speed of the plunger; d t is the tubing diameter; H t is the tubing length.

[0037] Furthermore, the liquid column friction coefficient f at the upper part of the plunger l adopts the foam friction coefficient, and the expression is:

[0038]

[0039] In the formula: C F and n F are foam constants; d F is the foam hydraulic diameter; v F is the foam flow rate; μ F is the foam viscosity;

[0040] The foam viscosity is calculated by the following formula:

[0041]

[0042] In the formula: μ l is the liquid viscosity; is the gas holdup.

[0043] The present invention also discloses a method for gas lift combined drainage gas production using the drainage gas production device. The downhole device further includes a buffer. A catcher is installed above the plunger. The lower part of the plunger is connected to a gripper, and the foam drainage rod is clamped at the lower end of the gripper;

[0044] The method for gas lift combined drainage gas production includes three stages: shut-in pressure recovery, open-well gas lift, and continuous production. The specific process is as follows:

[0045] The control system controls the catcher to release the plunger, and the gas well starts to enter the shut-in pressure recovery stage, completing two processes of plunger falling and pressure recovery. When the plunger falls to the buffer, the gripper opens to release the foam drainage rod;

[0046] When the casing pressure recovers to the maximum casing pressure, the control system controls the valve to open, and the gas well enters the open-well gas lift stage. The plunger moves upward to drain the liquid, which is discharged from the gas transmission pipeline and the liquid drainage pipeline respectively; when the liquid column above the plunger starts to be discharged, the oil pressure starts to rise;

[0047] After all the liquid column above the plunger is discharged, the gas well enters the continuous production stage, completing three processes: a large amount of gas production, stable continuous flow, and wellbore liquid accumulation.

[0048] During the processes of a large amount of gas production, stable continuous flow, and wellbore liquid accumulation, production monitoring is completed through a gas flowmeter and a liquid flowmeter, and casing pressure and tubing pressure monitoring are completed through a tubing pressure sensor and a casing pressure sensor. The monitoring data is transmitted to the control system, and the control system remotely controls the gas well.

[0049] Furthermore, the three processes of a large amount of gas production, stable continuous flow, and wellbore liquid accumulation are specifically as follows:

[0050] During the stage of a large amount of gas production, the tubing pressure and the casing pressure rapidly decrease, and the gas production volume also continuously decreases. The duration of this stage is determined by the energy accumulated near the wellbore.

[0051] When the pressure drops to a certain extent, the gas well enters the stable continuous flow stage. The casing pressure gradually rises, the tubing pressure is basically stable, the gas flow velocity is lower than the critical liquid-carrying velocity, and liquid begins to accumulate slowly in the wellbore.

[0052] When the production time of the gas well exceeds the stable continuous flow stage, the tubing-casing pressure difference increases, the gas production volume decreases, and the time required to shut in the well and restore the pressure increases exponentially. A large amount of liquid begins to accumulate in the gas well, affecting the next cycle. Therefore, the well shut-in time should be selected within the stable continuous flow stage, specifically: the period when the casing pressure rises and the gas production volume decreases by 8% - 10%.

[0053] Furthermore, the lower end of the housing is a delivery window, and the delivery window is used to install the foam drainage rod.

[0054] The method for replacing the foam drainage rod is as follows:

[0055] When the plunger moves up to the wellhead, close the gate valve, open the delivery window, install the foam drainage rod on the gripper, close the delivery window, and open the gate valve.

[0056] The method for delivering the foam drainage rod is as follows: The control system controls the catcher to release the plunger. The plunger drives the gripper to hold the foam drainage rod and fall together. When the plunger runs down to the bottom of the well, it hits the buffer, the gripper opens to release the foam drainage rod, and the foam drainage rod freely falls and is fully mixed with the liquid accumulated in the gas well to generate a large amount of low-density water-containing foam.

[0057] Compared with the prior art, the present invention has the following beneficial technical effects:

[0058] The present invention discloses a drainage gas production device combining plunger gas lift and foam drainage. At the wellhead part, a gas flowmeter is added to the gas transmission pipeline, and a liquid flowmeter is added to the liquid drainage pipeline. The production is monitored through the gas flowmeter and the liquid flowmeter. On the downhole tubing and casing, the casing pressure and tubing pressure are monitored through a tubing pressure sensor and a casing pressure sensor, and the monitored data is transmitted to the control system. The control system realizes the remote control and automatic management of the gas well according to the above process, achieving the purpose of cost saving and production efficiency improvement. The present invention designs a calculation formula for the casing pressure when the plunger just rises to the wellhead in the control system, which can accurately calculate the casing pressure result, determine the opening time of the gas well, and realize the intelligent control of the gas well.

[0059] Furthermore, a gripper is added under the plunger. The gripper holds the foam drainage rod, and the foam drainage rod is installed from the placement window, which is convenient for installation and disassembly.

[0060] The present invention also discloses a method for gas lift combined drainage gas production using the above-mentioned drainage gas production device combining plunger gas lift and foam drainage. The foam drainage process is used to assist the plunger gas lift, extending the open well production time and improving the production efficiency; reducing the tubing-casing pressure difference, reducing liquid slippage, and reducing the requirement for the plunger running speed; optimizing the opening and closing times of the gas well to realize the intelligent control of the gas well; scientifically maintaining the production of ultra-deep gas wells. The combination of the plunger gas lift process and the foam drainage process can achieve a better drainage gas production effect, giving full play to the advantages of the plunger gas lift process in improving the lifting efficiency and the foam drainage in reducing the liquid accumulation density, and can be applied to ultra-deep gas wells through the combined lifting method to increase the lifting depth and improve the production.

[0061] Furthermore, through optimization design, it is obtained that the well closing time should be selected within the stable continuous flow stage, that is, when the casing pressure rises steeply and the gas production rate drops by 8% - 10%. Description of the Drawings

[0062] Figure 1 It is a schematic diagram of the wellhead part structure of a drainage gas production device combining plunger gas lift and foam drainage according to the present invention;

[0063] Figure 2 It is a schematic diagram of the downhole part structure of a drainage gas production device combining plunger gas lift and foam drainage according to the present invention;

[0064] Figure 3 It is the change curve of the tubing pressure and the casing pressure during the operation of this process.

[0065] Among them, 1. Trapper; 2. Fishing head; 3. Plunger; 4. Clamp; 5. Foam drainage rod; 6. Delivery window; 7. Gate valve; 8. Gathering and transportation pipeline; 9. Oil pipe; 10. Casing; 11. Valve; 12. Separator; 13. Gas flowmeter; 14. Gas transmission pipeline; 15. Liquid flowmeter; 16. Liquid drainage pipeline; 17. Oil pipe temperature sensor; 18. Oil pipe pressure sensor; 19. Casing temperature sensor; 20. Casing pressure sensor; 21. Control system; 22. Buffer; 23. Fixator. Detailed implementation mode

[0066] In order to make the objectives, technical solutions and advantages of the present invention clearer, the following further detailed description is provided in conjunction with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention, that is, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments.

[0067] The components described and shown in the drawings and embodiments of the present invention can be arranged and designed in various different configurations. Therefore, the detailed description of the embodiments of the present invention provided in the following drawings is not intended to limit the scope of the present invention to be protected, but only represents a selected embodiment of the present invention. Based on the drawings and embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts belong to the protection scope of the present invention.

[0068] It should be noted that: the term "comprising", "including" or any other variant is intended to cover non-exclusive inclusion, so that a process, element, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or also includes elements inherent to the process, element, method, article or device.

[0069] The features and performance of the present invention are further described in detail below in conjunction with embodiments.

[0070] As Figure 1 shown, the present invention discloses a drainage gas production device combining plunger gas lift and foam drainage, including two parts: a wellhead device and a downhole device. The wellhead device includes a housing, a gathering and transportation pipeline 8, a valve 11, a separator 12, a gas transmission pipeline 14, a liquid drainage pipeline 16, and a control system 21; a trapper 1, a fishing head 2, a plunger 3, a clamp 4, and a foam drainage rod 5 are installed in the housing, and the lower end of the housing is a delivery window 6;

[0071] As Figure 2 shown, the downhole device includes a casing 10, an oil pipe 9, a buffer 22, and a fixator 23. The fixator 23 is fixed on the inner wall of the oil pipe 9, and the buffer 22 is fixed above the fixator 23.

[0072] The catcher 1 of the wellhead device is controlled by the control system 21. It can capture the fishing head 2 through the electromagnet below the catcher 1. The fishing head 2 is connected to the plunger 3. There is a gripper 4 at the lower part of the plunger 3. The gripper 4 clamps the foam drainage rod 5. The foam drainage rod 5 is installed through the placement window 6. A gate valve 7 is provided below the placement window 6. The gate valve 7 is connected to the oil pipe 9. One side of the oil pipe 9 is connected to the separator 12 through the gathering pipeline 8 via the valve 11. At the outlet of the separator 12 are the gas transmission pipeline 14 and the liquid drainage pipeline 16 respectively. A gas flowmeter 13 is provided on the gas transmission pipeline 14, and a liquid flowmeter 15 is provided on the liquid drainage pipeline 16. The gas flowmeter 13 and the liquid flowmeter 15 are connected to the control system 21 through wires;

[0073] At the top of the oil pipe 9, there are an oil pipe temperature sensor 17 and an oil pipe pressure sensor 18. At the top of the casing 10, there are a casing temperature sensor 19 and a casing pressure sensor 20. The four sensors are connected to the control system 21 through wires;

[0074] The catcher 1 captures the plunger 3 under the control of the control system 21 to control the timing of opening and closing the well; when the plunger 3 starts to fall from the wellhead, it enters the closed well state, and when the plunger 3 reaches the topmost position, it is the open well state.

[0075] The gripper 4 is connected to the plunger 3 and is used to fix the foam drainage rod 5 during the downward movement of the plunger 3 and release the foam drainage rod 5 after the plunger 3 impacts the buffer 22;

[0076] The placement window 6 is used to install the foam drainage rod 5 and can be opened after the gate valve 7 is closed;

[0077] The gate valve 7 is used to control the pressure behind the gate valve 7. After the plunger 3 is captured by the catcher 1, it is automatically closed by the control system 21. At this time, the foam drainage rod 5 is installed in the placement window 6 and is automatically opened by the control system 21 during the downward movement of the plunger 3;

[0078] The gas flowmeter 13 and the liquid flowmeter 15 are respectively used to measure the gas production and liquid production of the gas well and transmit the results to the control system 21;

[0079] The oil pipe temperature sensor 17, the oil pipe pressure sensor 18, the casing temperature sensor 19, and the casing pressure sensor 20 are respectively used to monitor the temperature and pressure of the oil pipe 9 and the temperature and pressure of the casing 10 and transmit the results to the control system 21;

[0080] The separator 12 is used to separate the fluid produced by the gas well into gas and liquid parts, which are discharged from the gas transmission pipeline 14 and the liquid drainage pipeline 16 respectively.

[0081] Such as Figure 1 、 Figure 3As shown in the figure, the production of the gas well controlled by the present invention mainly goes through three stages: shut-in pressure build-up, open-hole gas lift, and continuous production. The control system 21 controls the catcher 1 to release the plunger 3, and the gas well starts to enter the shut-in pressure build-up stage, completing two processes of the plunger 3 falling and pressure build-up. When the plunger 3 falls to the buffer 22, the gripper 4 opens to release the foam drainage rod 5;

[0082] When the casing pressure recovers to the maximum casing pressure, the control system 21 controls the valve 11 to open, and the gas well enters the open-hole gas lift stage. The plunger 3 moves upward to drain the liquid. When the liquid column above the plunger 3 starts to be discharged, the oil pressure starts to rise;

[0083] After all the liquid column above the plunger 3 is discharged, the gas well enters the continuous production stage, completing three processes of a large amount of gas production, stable continuous flow, and wellbore liquid accumulation;

[0084] In the stage of a large amount of gas production, the oil pressure and casing pressure drop rapidly, and the gas production volume also continuously decreases. The length of this stage is determined by the energy accumulated near the wellbore and is uncontrollable;

[0085] When the pressure drops to a certain extent, the gas well enters the stable continuous flow stage, which is characterized by the casing pressure gradually rising, the oil pressure being basically stable, the gas flow rate being lower than the critical liquid-carrying flow rate, and the wellbore starting to slowly accumulate liquid; when the production time of the gas well exceeds the stable continuous flow stage, the oil-casing pressure difference suddenly increases, the gas production volume decreases, and the time required to shut in and recover the pressure doubles. The gas well starts to accumulate a large amount of liquid, affecting the next cycle. Therefore, the shut-in time should be selected within the stable continuous flow stage, that is, when the casing pressure suddenly rises and the gas production volume decreases by 8% - 10%;

[0086] The present invention completes the output monitoring of the above processes through the gas flowmeter 13 and the liquid flowmeter 15, completes the monitoring of the casing pressure and oil pressure through the tubing pressure sensor 18 and the casing pressure sensor 20, and transmits the monitoring data to the control system 21. The control system 21 realizes the remote control and automatic management of the gas well according to the above processes, achieving the purpose of saving costs and improving production efficiency.

[0087] As Figure 1 , Figure 2 shown, the method for replacing the foam drainage rod 5 in the present invention is that when the plunger 3 moves upward to the wellhead, the gate valve 7 is closed, the delivery window 6 is opened, the foam drainage rod 5 is installed on the gripper 4, the delivery window 6 is closed, and the gate valve 7 is opened; the method for delivering the foam drainage rod in the present invention is that the control system 21 controls the catcher 1 to release the plunger 3. The lower part of the plunger 3 is connected to the gripper 4, and the gripper 4 holds the foam drainage rod 5 and falls together. When the plunger 3 runs downward to the bottom of the well, it hits the buffer 22, and the gripper 4 opens to release the foam drainage rod 5. The foam drainage rod 5 falls freely and is fully mixed with the liquid accumulation in the gas well, generating a large amount of low-density water-containing foam, changing the gas-liquid flow pattern in the wellbore, reducing the liquid slippage loss during the lifting process, and improving the liquid-carrying capacity of the gas.

[0088] As Figure 1 , Figure 2 shown, in order to scientifically maintain the production of ultra-deep gas wells and achieve intelligent control of gas wells, it is necessary to determine the opening time of gas wells. The present invention controls the opening of gas wells by determining the casing pressure required for the plunger 3 to rise to the wellhead; the casing pressure P when the plunger 3 just rises to the wellhead c is:

[0089] P c = P t +(P lh + P lf )W + P p + P f (1)

[0090] In the formula: P t is the oil pressure, MPa;

[0091] P lh is the liquid column pressure of lifting a 1m 3 liquid slug,

[0092] P lf is the frictional pressure of lifting a 1m 3 liquid slug,

[0093] W is the periodic drainage volume, m 3 ;

[0094] P p is the pressure generated by the weight of the plunger 3, MPa;

[0095] P f is the gas friction at the lower part of the plunger 3,

[0096] f l is the liquid column friction coefficient at the upper part of the plunger 3;

[0097] f g is the gas friction coefficient;

[0098] ρ l is the liquid density, kg / m 3 ;

[0099] ρ g is the gas density, kg / m 3 ;

[0100] v p is the running speed of the plunger 3, m / s;

[0101] d t is the diameter of the tubing 9, m;

[0102] Ht is the length of tubing 9, m;

[0103] For the gas-lift - foam drainage gas production process of "plunger 3", since the liquid column above the plunger 3 presents a foam form after reacting with the foam drainage rod 5, the friction coefficient of the liquid column above the plunger 3 should adopt the foam friction coefficient:

[0104]

[0105] In the formula: C F and n F are foam constants, taking 18.36 and 0.97 respectively;

[0106] d F is the hydraulic diameter of the foam, m;

[0107] v F is the foam flow velocity, approximately equal to the velocity of the plunger 3, m / s;

[0108] μ F is the foam viscosity, Pa·s;

[0109] The foam viscosity is calculated by the following formula:

[0110]

[0111] In the formula: μ l is the liquid viscosity, Pa·s;

[0112] is the gas holdup, decimal.

[0113] Since the casing pressure P when the plunger 3 just rises to the wellhead c is the pressure of the annular gas under the maximum casing pressure expansion, and the maximum casing pressure P cmax refers to the casing pressure that the plunger 3 must reach when starting to move upward. Ignoring the influence of the gas deviation factor on gas expansion, the maximum casing pressure P cmax is:

[0114]

[0115] To ensure that the plunger 3 has sufficient energy to reach the wellhead, a safety factor of 1.05 needs to be multiplied, then:

[0116]

[0117] In the formula: A t is the area of the tubing 9, m 2 ; A c is the area of the casing 10, m 2 .

[0118] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: modifications or equivalent substitutions can still be made to the specific embodiments of the present invention, and any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention shall be covered by the protection scope of the claims of the present invention.

Claims

1. A gas drainage and production device combining plunger gas lift and foam drainage, characterized in that, It includes a control system (21), a wellhead device and a downhole device; The wellhead device includes a housing, a gas transmission pipeline (14) and a liquid drainage pipeline (16); a gas flowmeter (13) is provided on the gas transmission pipeline (14), a liquid flowmeter (15) is provided on the liquid drainage pipeline (16), and the gas flowmeter (13) and the liquid flowmeter (15) are connected to the control system (21); A plunger (3) and a foam drainage rod (5) clamped below the plunger (3) are installed inside the housing; a gate valve (7) is provided below the housing, and the gate valve (7) is connected to the control system (21); The downhole device includes a tubing pressure sensor (18) provided on the tubing (9), a casing pressure sensor (20) provided on the casing (10), and the tubing pressure sensor (18) and the casing pressure sensor (20) are connected to the control system (21); The control system (21) is used to calculate the maximum casing pressure when the plunger (3) rises to the wellhead, and control the opening time of the gas well by determining the casing pressure required for the plunger (3) to rise to the wellhead.

2. The gas drainage and production device combining plunger gas lift and foam drainage according to claim 1, characterized in that The wellhead device further includes a gathering and transportation pipeline (8) and a separator (12). One side of the tubing (9) is connected to the separator (12) through the gathering and transportation pipeline (8) via a valve (11), and the outlets of the separator (12) are respectively the gas transmission pipeline (14) and the liquid drainage pipeline (16); The lower end of the housing is a dropping window (6), and the dropping window (6) is used to install the foam drainage rod (5); A catcher (1) and a fishing head (2) are installed above the plunger (3), the lower part of the plunger (3) is connected to a gripper (4), the gate valve (7) is arranged below the dropping window (6), and the gate valve (7) is connected to the tubing (9); The downhole device further includes a buffer (22) and a retainer (23), the retainer (23) is fixed on the inner wall of the tubing (9), and the buffer (22) is fixed above the retainer (23); A tubing temperature sensor (17) is also provided on the tubing (9), and a casing temperature sensor (19) is also provided on the casing (10).

3. The gas drainage and production device combining plunger gas lift and foam drainage according to claim 2, characterized in that, The gate valve (7) is used to control the pressure after the valve (11). After the plunger (3) is caught by the catcher (1), it is controlled to be in a closed state by the control system (21); at this time, the dropping window (6) installs the foam drainage rod (5), and the gate valve (7) is controlled to be in an open state by the control system (21) during the downward movement stage of the plunger (3).

4. The gas drainage and production device combining plunger gas lift and foam drainage according to claim 1, characterized in that, Calculate the maximum casing pressure when the computing plunger (3) rises to the wellhead. Specifically: First, calculate the casing pressure P required for the plunger (3) to rise to the wellhead according to the following formula c , and then calculate the maximum casing pressure P c based on P cmax ; P c = P t +(P lh + P lf )W + P p + P f ; Where: P t is the oil pressure; P lh For lifting by 1 m 3 The liquid column pressure of the liquid slug; P lf For lifting by 1 m 3 Frictional pressure of the liquid slug; W is the periodic drainage volume; P p is the pressure generated by the weight of the plunger (3); P f is the gas friction at the lower part of the plunger (3).

5. The gas drainage and production device combining plunger gas lift and foam drainage according to claim 4, characterized in that, The casing pressure P when the plunger (3) just rises to the wellhead c is the pressure of the annular gas under the maximum casing pressure expansion. The maximum casing pressure P cmax refers to the casing pressure that the plunger (3) must reach to start moving upward. Ignoring the influence of the gas deviation factor on gas expansion, the maximum casing pressure P cmax is as follows: Where: A t is the area of the tubing (9); A c is the area of the casing (10), and k is the safety factor.

6. The gas drainage and production device combining plunger gas lift and foam drainage according to claim 4, characterized in that, Lift by 1 m 3 The liquid column pressure P of the liquid slug lh The calculation formula is as follows: Lift by 1 m 3 Frictional pressure P of the liquid slug lf The calculation formula is as follows: where, f l is the friction coefficient of the liquid column above the plunger (3); ρ l is the liquid density; v p is the running speed of the plunger (3); d t is the diameter of the tubing (9); A t is the area of the tubing (9); Gas friction P at the lower part of the plunger (3) f The expression is as follows: Among them, ρ g is the gas density; f g is the gas friction coefficient; v p is the operating speed of the plunger (3); d t is the diameter of the tubing (9); H t is the length of the tubing (9).

7. The gas drainage and production device combining plunger gas lift and foam drainage according to claim 6, characterized in that, Friction coefficient f of the liquid column above the plunger (3) l Adopt the foam friction coefficient, and the expression is: Where: C F and n F are foam constants; d F is the hydraulic diameter of the foam; v F is the foam flow rate; μ F is the foam viscosity; The foam viscosity calculation is calculated by the following formula: where: μ l is the liquid viscosity; is the gas holdup.

8. A method for gas lift combined drainage gas production using the drainage gas production device according to any one of claims 1-7, characterized in that, The downhole device further includes a buffer (22), a catcher (1) is installed above the plunger (3), the lower part of the plunger (3) is connected to a gripper (4), and the foam drainage rod (5) is clamped at the lower end of the gripper (4); The gas lift combined drainage and gas production method includes three stages: shut-in pressure recovery, open-well gas lift and continuous production, and the specific process is as follows: The control system (21) controls the catcher (1) to release the plunger (3), and the gas well starts to enter the shut-in pressure recovery stage, completing two processes of the plunger (3) falling and pressure recovery. When the plunger (3) falls to the buffer (22), the gripper (4) opens to release the foam drainage rod (5); After the casing pressure returns to the maximum casing pressure, the control system (21) controls the opening of the valve (11), and the gas well enters the open well gas lift stage. The plunger (3) moves upward to drain the liquid, which is discharged from the gas transmission pipeline (14) and the liquid drainage pipeline (16) respectively. When the liquid column above the plunger (3) starts to be discharged, the oil pressure begins to rise. After all the liquid column above the plunger (3) is discharged, the gas well enters the continuous production stage, completing three processes: a large amount of gas production, stable continuous flow, and wellbore liquid accumulation. During the processes of a large amount of gas production, stable continuous flow, and wellbore liquid accumulation, the output is monitored by the gas flowmeter (13) and the liquid flowmeter (15), and the casing pressure and oil pressure are monitored by the tubing pressure sensor (18) and the casing pressure sensor (20). The monitoring data is transmitted to the control system (21), and the control system (21) remotely controls the gas well.

9. The method for gas lift combined drainage gas production according to claim 8, characterized in that, The three processes of a large amount of gas production, stable continuous flow, and wellbore liquid accumulation are specifically as follows: During the stage of a large amount of gas production, the oil pressure and casing pressure drop rapidly, and the gas production volume also continuously decreases. The length of this stage is determined by the energy accumulated near the wellbore. When the pressure drops to a certain extent, the gas well enters the stable continuous flow stage. The casing pressure gradually rises, the oil pressure is basically stable, the gas flow velocity is lower than the critical liquid-carrying flow velocity, and the wellbore begins to accumulate liquid slowly. When the production time of the gas well exceeds the stable continuous flow stage, the oil-casing pressure difference increases, the gas production volume decreases, and the time required to shut in the well to restore pressure increases exponentially. The gas well begins to accumulate a large amount of liquid, affecting the next cycle. Therefore, the well shut-in time should be selected within the stable continuous flow stage, specifically: the time period when the casing pressure rises and the gas production volume decreases by 8% - 10%.

10. The gas lift combined drainage gas production method according to claim 8, wherein, The lower end of the housing is a delivery window (6), and the delivery window (6) is used to install the foam drainage rod (5). The method for replacing the foam drainage rod (5) is as follows: When the plunger (3) moves upward to the wellhead, close the gate valve (7), open the delivery window (6), install the foam drainage rod (5) on the gripper (4), close the delivery window (6), and open the gate valve (7). The method for delivering the foam drainage rod (5) is: the control system (21) controls the catcher (1) to release the plunger (3). The plunger (3) drives the gripper (4) to hold the foam drainage rod (5) and they fall together. When the plunger (3) runs downward to the bottom of the well, it hits the buffer (22), and the gripper (4) opens to release the foam drainage rod (5). The foam drainage rod (5) falls freely and is fully mixed with the liquid accumulated in the gas well to generate a large amount of low-density water-containing foam.

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