Gas well liquid carrying capacity improving device and composite drainage gas recovery method

Abstract

The invention discloses a gas well liquid carrying capacity improving device which comprises a shaft gas lift device and a pressurization auxiliary device, and is characterized in that a first oil pipe is sleeved in a sleeve, a second oil pipe is sleeved in the first oil pipe, a plurality of gas lift valves are arranged on the second oil pipe, and an annular check valve is sleeved at the lower end of the second oil pipe. The invention further discloses a method for conducting composite drainage gas recovery through the lifting device. The method comprises the steps that S1, production is normally conducted through the first oil pipe, gas well accumulated liquid is prolonged, and the second oil pipe is lowered under pressure; s2, the time is prolonged, and liquid is accumulated again in the shaft; s3, the natural gas trapping frame supplies gas to the gas generator and the compressor; and S4, high-pressure gas is injected between the first oil pipe and the second oil pipe, and gas well composite drainage gas recovery is conducted till the gas well is revived. The device for improving the liquid carrying capacity of the gas well solves the technical problems that due to the fact that the pipe diameter of an existing small oil pipe is small, the starting pressure difference of gas lifting is large, lifting is difficult, or when the lifting pressure is increased, liquid in an oil sleeve annulus is easily pressed back to a stratum.

Description

Technical Field

[0001] The present invention belongs to the technical field of natural gas development, relates to a device for enhancing the liquid-carrying capacity of gas wells, and also relates to a method for draining gas and producing liquid using the enhancing device. Background Technique

[0002] During the production process of natural gas, some gas wells use production tubing with a larger diameter, and even directly use production casings with diameters of Φ114mm and Φ88.9mm as tubing to start production when completing the well. As the gas well produces and the pressure drops, liquid accumulates in the wellbore. In the initial stage of gas well production, it can carry liquid and produce continuously. As the liquid accumulation volume increases, the gas well cannot carry liquid normally. At this time, it is necessary to lower production tubing with a smaller diameter or a velocity string to reduce the critical liquid-carrying flow rate of the gas well and improve the liquid-carrying capacity of the gas well.

[0003] When small-diameter tubing is used in the initial stage of liquid accumulation in gas wells or gas wells with a small gas-water ratio, it can improve the liquid-carrying capacity of gas wells and extend the self-production time of gas wells. However, when the gas-water ratio is large in the later stage of gas well production, the liquid accumulation in the gas well may kill the gas well. In order to resume production, the common practice is to use nitrogen gas lift or compressor gas lift. At this time, due to the smaller diameter of the small tubing, for the same liquid accumulation volume, the liquid column formed in the wellbore is higher, and coupled with the greater friction of the small tubing, the starting differential pressure of gas lift is large and it is difficult to lift through. If the lifting pressure is increased, it is easy to press the liquid in the oil-casing annulus back into the formation. Summary of the Invention

[0004] The purpose of the present invention is to provide a device for enhancing the liquid-carrying capacity of gas wells, which solves the technical problems that the existing small tubing has a large starting differential pressure for gas lift and is difficult to lift through, or when the lifting pressure is increased, it is easy to press the liquid in the oil-casing annulus back into the formation due to its smaller diameter.

[0005] Another purpose of the present invention is to provide a method for composite drainage gas production using the enhancing device.

[0006] The technical solution adopted by the present invention is that the device for enhancing the liquid-carrying capacity of gas wells includes a wellbore gas lift device and a pressurization assistance device. The wellbore gas lift device includes a casing, a first tubing penetrates through the casing, a second tubing penetrates through the first tubing, several gas lift valves are provided on the second tubing, a ring-shaped check valve is sleeved at the lower end of the second tubing, and the outer wall of the ring-shaped check valve is attached to the inner wall of the first tubing;

[0007] The pressurization assistance device includes a trapping device. The trapping device is connected to the casing, the first tubing, and the second tubing respectively through gas pipes. The trapping device is connected to a gas generator through a gas pipe. The gas generator is connected to a compressor through a gas pipe. The compressor is connected to the first tubing and the second tubing respectively through gas pipes.

[0008] The characteristics of the present invention also lie in:

[0009] Several gas lift valves are on the same vertical line.

[0010] The capture device is a natural gas capture rack.

[0011] The capture device is a gas-liquid two-phase separator.

[0012] Another technical solution adopted by the present invention is a method for composite drainage gas production using a gas well liquid carrying capacity enhancement device, which is specifically as follows:

[0013] S1: The gas well produces normally through the first oil pipeline. As time goes by, the gas well gradually accumulates liquid, resulting in a decrease in production. The gas well is then driven into the second oil pipeline under pressure, and natural gas is produced through the second oil pipeline. The gas well continues to produce smoothly again;

[0014] S2: As time goes by, the wellbore accumulates liquid again. According to the production situation of each well, if a well shows a sudden drop in gas production or signs of drowning, the capture device is operated to separate gas from the main pipe to supply gas to the gas generator for power generation and to the compressor on the other hand;

[0015] S3: The high-pressure gas boosted by the compressor is injected into the annulus between the first oil pipe and the second oil pipe to perform gas recovery by composite drainage of the gas well until the gas well is revived and resumes continuous production by autonomously carrying liquid in the second oil pipe;

[0016] S4: Repeat S2-S3 to carry out measures of pressurization and multi-stage gas lift valve gas lift for the next liquid-filled gas well.

[0017] The present invention is also characterized in that:

[0018] The specific method of water drainage and gas production in S3 is as follows: when the injection pressure reaches the set P1, the first-level gas lift valve at the top of the second oil pipe is opened to discharge the accumulated liquid above the first-level gas lift valve in the wellbore of the second oil pipe; when the injection fracturing reaches P2, the accumulated liquid above the second-level gas lift valve is discharged; when the injection fracturing reaches P3, the accumulated liquid above the third-level gas lift valve is discharged, and so on, where P1 <P2<P3......<P n After the bottom gas lift valve is closed after lifting liquid, the gas well is completely revived, the accumulated liquid in the second oil pipe 4 is discharged, and the synchronously discharged natural gas is collected in the main pipe through the wellhead pipeline.

[0019] When the well is opened for production, all gas lift valves are in the closed state.

[0020] The beneficial effects of the present invention are:

[0021] 1. The lifting device of the present invention forms a liquid-carrying capacity improvement device for gas wells by designing a small tubing with multiple gas lift valves and an annular check valve and combining it with a wellhead surface pressurization device. Since the diameter of the production string is reduced, the critical liquid-carrying flow rate of the gas well can be significantly reduced, the liquid-carrying capacity of the gas well can be improved, and drowned gas wells can also be revived. At the same time, the annular check valve at the end of the small tubing can prevent the gas lift pressure from being too high and pressing the fluid back into the formation again.

[0022] 2. The lifting device of the present invention is applicable to gas wells that directly produce through casing completion of the original production string or gas wells that produce with large-diameter tubing. During the middle and late production stages, a small-diameter tubing with multiple gas lift valves and an annular check valve is run in. The work under pressure is mature and easy to operate.

[0023] 3. The lifting device of the present invention has a wide range of applications. It can be used for liquid-carrying in the initial stage of liquid accumulation to gas lift for production resumption. The formation pressure and production rate are not limited. It can realize drainage gas production throughout the entire life cycle of gas wells with water production and can be applied to cluster well groups. The surface part shares a set of equipment, which will greatly reduce the process operation and usage costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a schematic structural diagram of the lifting device of the present invention;

[0025] Figure 2 is a schematic structural diagram of the second tubing in the lifting device of the present invention;

[0026] Figure 3 is a top view of the first tubing and the second tubing in the lifting device of the present invention.

[0027] In the figure, 1. casing, 2. first tubing, 3. gas lift valve, 4. second tubing, 5. trapping device, 6. gas generator; 7. compressor, 8. gathering / union station, 9. annular check valve. DETAILED DESCRIPTION OF THE INVENTION

[0028] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] The gas well liquid-carrying capacity improvement device, as Figure 1As shown in the figure, it includes a wellbore gas lift device and a pressurization auxiliary device. The wellbore gas lift device includes a casing 1. Generally, the models of the casing 1 are selected as Φ114.3mm and Φ88.9mm. A first oil pipe 2 runs through the casing 1, and a second oil pipe 4 runs through the first oil pipe 2. The diameter of the second oil pipe 4 is smaller than that of the first oil pipe 2, forming an annular space between them. The small-diameter second oil pipe 4 is to increase the gas flow rate and reduce the critical liquid-carrying flow rate. The size selection depends on the existing pipe string size in the well, the critical liquid-carrying flow rate, the gas production volume, the water-gas ratio, etc. At the same time, the friction of the small-diameter oil pipe needs to be considered. Generally, small oil pipes such as Φ60.32mm, Φ50.8mm, Φ48.1mm, or Φ38.1mm are selected.

[0030] As Figure 2 shown in the figure, several gas lift valves 3 are provided on the second oil pipe 4. The several gas lift valves 3 are on the same vertical line. The design of the multi-stage gas lift valves 3 is to reduce the lifting pressure, shorten the lifting time, and avoid secondary pollution of the formation. The wellbore liquid is discharged section by section from top to bottom. The design of the gas lift valves mainly depends on the highest pressure at the outlet of the compressor 7, the depth of the static liquid level in the wellbore, and the specific gravity of the liquid mixture column. It can be 2 stages, or 3 stages, 4 stages, 5 stages, etc. According to the order from top to bottom, they can be defined as the first-stage gas lift valve, the second-stage gas lift valve, and the third-stage gas lift valve.

[0031] As Figure 3 shown in the figure, an annular check valve 9 is sleeved at the lower end of the second oil pipe 4. The outer wall of the annular check valve 9 fits with the inner wall of the first oil pipe 2. The annular check valve 9 attached to the end of the second oil pipe 4 only allows the fluid to flow from bottom to top and does not allow the fluid to flow from top to bottom. This design avoids the fluid being pressed back into the formation due to excessive pressure during high-pressure gas lift in the annulus between the first oil pipe 2 and the second oil pipe 4.

[0032] As Figure 1 shown in the figure, the pressurization auxiliary device includes a trapping device 5. Among them, the trapping device 5 is a natural gas trapping rack or a gas-liquid two-phase separator. The trapping device 5 is connected to the casing 1, the first oil pipe 2, and the second oil pipe 4 through gas pipes respectively. The specific structure is as follows: at the outlet of the wellhead at the upper ends of the casing 1, the first oil pipe 2, and the second oil pipe 4, the same gas pipe is connected, and the casing 1, the first oil pipe 2, and the second oil pipe 4 are all connected to the gas pipe. The free end of the gas pipe is connected to the well factory main pipe. The trapping device 5 is connected to the well factory main pipe. The trapping device 5 is connected to a gas generator 6 through a gas pipe. The gas generator 6 is connected to a compressor 7 through a gas pipe. The compressor 7 is connected to the first oil pipe 2 and the second oil pipe 4 through gas pipes respectively. The specific method is the same as the way the trapping device 5 is connected to the casing 1, the first oil pipe 2, and the second oil pipe 4 respectively.

[0033] The capture device 5 or the gas-liquid two-phase separator realizes gas-water separation to ensure that a qualified gas source is provided for the generator 6 and the compressor 7. A suitable gas-liquid separation device can be selected according to the gas production and water production. The gas generator 6 provides power for the compressor 7, pipeline insulation and other electricity consumption in the well site. The selection depends on the total power consumption and has a certain surplus. The gas is taken from the wellhead dry pipe gas to achieve convenience, greenness and environmental protection. The compressor 7 realizes ground pressurization and provides a high-pressure gas source for gas lift drainage. The selection depends on the maximum lifting pressure, the maximum daily injection volume, and takes into account a certain surplus. The capture device 5 or the gas-liquid two-phase separator transports the collected natural gas to the gathering / transmission / combination station 8 through a gas pipeline.

[0034] The method for compound drainage gas production by using a gas well liquid carrying capacity enhancement device is as follows:

[0035] S1: The gas well is normally produced through the first oil pipe 2. As time goes by, the gas well gradually accumulates liquid, resulting in a decrease in production. The second oil pipe 4 is lowered under pressure, and natural gas is produced through the second oil pipe 4, which improves the liquid carrying capacity of the gas well. The gas well is continuously and stably produced again. After the small-diameter oil pipe is lowered here, compared with the previous large-diameter oil pipe, the critical liquid carrying flow rate of the gas well can be significantly reduced due to the reduction in the diameter of the production pipe string, thereby improving the liquid carrying capacity of the gas well, and the gas well is continuously and stably produced again.

[0036] S2: As time goes by, the wellbore accumulates liquid again. According to the production situation of each well, if a well shows a sudden drop in gas production or signs of drowning, the capture device 5 is operated to separate gas from the dry pipe to supply gas to the gas generator for power generation and to supply gas to the compressor.

[0037] S3: The high-pressure gas boosted by the compressor 7 is injected into the annulus between the first oil pipe 2 and the second oil pipe 4 to perform composite drainage and gas production of the gas well until the gas well is revived and the gas well resumes the state of autonomous liquid-carrying continuous production by the second oil pipe 4. The specific method of drainage and gas production is as follows: when the well is opened for production, all gas lift valves 3 are in a closed state. When the injection pressure reaches the set P1, the top first-level gas lift valve of the second oil pipe 4 is opened to discharge the accumulated liquid above the first-level gas lift valve of the wellbore of the second oil pipe 4; when the injection fracturing reaches P2, the accumulated liquid above the second-level gas lift valve is discharged; when the injection fracturing reaches P3, the accumulated liquid above the third-level gas lift valve is discharged, and so on, wherein P1 <P2<P3......<P n After the bottom gas lift valve is closed after lifting liquid, the gas well is completely revived, the accumulated liquid in the second oil pipe 4 is discharged, and the synchronously discharged natural gas is collected in the main pipe through the wellhead pipeline.

[0038] S4: Repeat S2-S3 to carry out measures of pressurization and multi-stage gas lift valve gas lift for the next liquid-filled gas well.

[0039] Example 1

[0040] Gas well liquid-carrying capacity improvement device, including a wellbore gas lift device and a pressurization assistance device. The wellbore gas lift device includes a casing 1, a first oil pipe 2 runs through the casing 1, a second oil pipe 4 runs through the first oil pipe 2, several gas lift valves 3 are provided on the second oil pipe 4, and an annular check valve 9 is sleeved at the lower end of the second oil pipe 4. The outer wall of the annular check valve 9 fits against the inner wall of the first oil pipe 2.

[0041] The pressurization assistance device includes a natural gas capture rack. The natural gas capture rack is connected to the casing 1, the first oil pipe 2, and the second oil pipe 4 through gas pipes respectively. Specifically: a gas pipe is jointly connected to the upper ends of the casing 1, the first oil pipe 2, and the second oil pipe 4, and the casing 1, the first oil pipe 2, and the second oil pipe 4 are all connected to the gas pipe. The free end of the gas pipe is connected to the well factory main pipe. The natural gas capture rack is connected to the well factory main pipe. The natural gas capture rack is connected to a gas generator 6 through a gas pipe. The gas generator 6 is connected to a compressor 7 through a gas pipe. The compressor 7 is connected to the first oil pipe 2 and the second oil pipe 4 through gas pipes respectively.

[0042] The method for the gas well liquid-carrying capacity improvement device to perform compound drainage gas production on a single gas well is as follows:

[0043] S1: A gas well normally produces through the first oil pipe 2. As time goes by, the gas well gradually accumulates liquid, resulting in a decrease in production. The second oil pipe 4 is lowered under pressure, and natural gas is produced through the second oil pipe 4, improving the liquid-carrying capacity of the gas well, and the gas well resumes continuous and stable production.

[0044] S2: As time goes by, when the wellbore accumulates liquid again, causing the production to gradually decrease or the well to be drowned, operate the capture device 5 to take gas from the main pipe for separation. On the one hand, supply gas to the gas generator for power generation, and on the other hand, supply gas to the compressor.

[0045] S4: The high-pressure gas pressurized by the compressor 7 is injected into the annulus between the first oil pipe 2 and the second oil pipe 4 for compound drainage gas production of the gas well until the gas well revives, and the gas well resumes the state of continuous production by relying on the second oil pipe 4 to carry liquid independently.

[0046] Embodiment 2

[0047] Gas well liquid-carrying capacity improvement device, including a wellbore gas lift device and a pressurization assistance device. The wellbore gas lift device includes a casing 1, a first oil pipe 2 runs through the casing 1, a second oil pipe 4 runs through the first oil pipe 2, several gas lift valves 3 are provided on the second oil pipe 4, and an annular check valve 9 is sleeved at the lower end of the second oil pipe 4. The outer wall of the annular check valve 9 fits against the inner wall of the first oil pipe 2.

[0048] The pressure boosting auxiliary device includes a gas-liquid two-phase separator. The gas-liquid two-phase separator is connected to the casing 1, the first tubing 2, and the second tubing 4 through gas pipes respectively. Specifically, the upper ends of the casing 1, the first tubing 2, and the second tubing 4 are jointly connected to a gas pipe, and the casing 1, the first tubing 2, and the second tubing 4 are all connected to the gas pipe. The free end of the gas pipe is connected to the well factory main pipe. The gas-liquid two-phase separator is connected to the well factory main pipe. The gas-liquid two-phase separator is connected to a gas generator 6 through a gas pipe. The gas generator 6 is connected to a compressor 7 through a gas pipe. The compressor 7 is connected to the first tubing 2 and the second tubing 4 through gas pipes respectively.

[0049] In order to further reduce costs and increase efficiency, the liquid-carrying capacity improvement device for gas wells can be used in a cluster well group. The specific method for using this improvement device for combined drainage gas production in a cluster well group is as follows:

[0050] S1: The gas well normally produces through the first tubing 2. As time goes by, the gas well gradually accumulates liquid, resulting in a decrease in production. The second tubing 4 is lowered under pressure, and natural gas is produced through the second tubing 4, improving the liquid-carrying capacity of the gas well. The gas well resumes continuous and stable production again. After the small-diameter tubing is lowered here, compared with the previous large-diameter tubing, due to the reduction of the production string diameter, the critical liquid-carrying flow rate of the gas well can be significantly reduced, improving the liquid-carrying capacity of the gas well, and the gas well resumes continuous and stable production again.

[0051] S2: As time goes by, the wellbore accumulates liquid again. According to the production situation of each well, if the gas production of a certain well suddenly decreases, or there are signs of drowning, operate the trapping device 5 to take gas from the main pipe for separation. On the one hand, it supplies gas to the gas generator for power generation, and on the other hand, it supplies gas to the compressor.

[0052] S3: The high-pressure gas boosted by the compressor 7 is injected into the annulus between the first tubing 2 and the second tubing 4 for combined drainage gas production of the gas well until the gas well revives, and the gas well resumes the state of continuous production by relying on the second tubing 4 to carry liquid independently.

[0053] S4: Repeat S2 - S3 to carry out the measures of boosting pressure and multi-stage gas lift valve gas lift for the next liquid-accumulating gas well.

[0054] Embodiment 3

[0055] The liquid-carrying capacity improvement device for gas wells includes a wellbore gas lift device and a pressure boosting auxiliary device. The wellbore gas lift device includes a casing 1. A first tubing 2 passes through the casing 1. A second tubing 4 passes through the first tubing 2. A number of gas lift valves 3 are provided on the second tubing 4. A ring-shaped check valve 9 is sleeved at the lower end of the second tubing 4. The outer wall of the ring-shaped check valve 9 is in contact with the inner wall of the first tubing 2.

[0056] The boost auxiliary device includes a gas-liquid two-phase separator, which is connected to the casing 1, the first oil pipe 2 and the second oil pipe 4 through an air pipe, specifically: the upper ends of the casing 1, the first oil pipe 2 and the second oil pipe 4 are connected to a common air pipe, and the casing 1, the first oil pipe 2 and the second oil pipe 4 are all connected to the air pipe, the free end of the air pipe is connected to the well plant main pipe, the gas-liquid two-phase separator is connected to the well plant main pipe, the gas-liquid two-phase separator is connected to the gas generator 6 through the air pipe, the gas generator 6 is connected to the compressor 7 through the air pipe, and the compressor 7 is connected to the first oil pipe 2 and the second oil pipe 4 through the air pipe.

[0057] Example 4

[0058] The method for compound drainage gas production by using a gas well liquid carrying capacity enhancement device is as follows:

[0059] S1: The gas well is normally produced through the first oil pipe 2. As time goes by, the gas well gradually accumulates liquid, resulting in a decrease in production. The second oil pipe 4 is lowered under pressure, and natural gas is produced through the second oil pipe 4, which improves the liquid carrying capacity of the gas well. The gas well is continuously and stably produced again. After the small-diameter oil pipe is lowered here, compared with the previous large-diameter oil pipe, the critical liquid carrying flow rate of the gas well can be significantly reduced due to the reduction in the diameter of the production pipe string, thereby improving the liquid carrying capacity of the gas well, and the gas well is continuously and stably produced again.

[0060] S2: As time goes by, the wellbore accumulates liquid again. According to the production situation of each well, if a well shows a sudden drop in gas production or signs of drowning, the capture device 5 is operated to separate gas from the dry pipe to supply gas to the gas generator for power generation and to supply gas to the compressor.

[0061] S3: The high-pressure gas boosted by the compressor 7 is injected into the annulus between the first oil pipe 2 and the second oil pipe 4 to perform composite drainage and gas production of the gas well until the gas well is revived and the gas well resumes the state of autonomous liquid-carrying continuous production by the second oil pipe 4. The specific method of drainage and gas production is as follows: when the well is opened for production, all gas lift valves 3 are in a closed state. When the injection pressure reaches the set P1, the top first-level gas lift valve of the second oil pipe 4 is opened to discharge the accumulated liquid above the first-level gas lift valve of the wellbore of the second oil pipe 4; when the injection fracturing reaches P2, the accumulated liquid above the second-level gas lift valve is discharged; when the injection fracturing reaches P3, the accumulated liquid above the third-level gas lift valve is discharged, and so on, wherein P1 <P2<P3......<P n After the bottom gas lift valve is closed after lifting liquid, the gas well is completely revived, the accumulated liquid in the second oil pipe 4 is discharged, and the synchronously discharged natural gas is collected in the main pipe through the wellhead pipeline.

[0062] S4: Repeat S2-S3 to carry out measures of pressurization and multi-stage gas lift valve gas lift for the next liquid-filled gas well.

Claims

1. Device for enhancing liquid - carrying capacity of gas well, Characterized in that, It includes a wellbore gas - lift device and a pressurization assistance device. The wellbore gas - lift device includes a casing (1), a first tubing (2) runs through the casing (1), a second tubing (4) runs through the first tubing (2). A number of gas - lift valves (3) are provided on the second tubing (4). An annular check valve (9) is sleeved at the lower end of the second tubing (4), and the outer wall of the annular check valve (9) fits with the inner wall of the first tubing (2); The pressurization assistance device includes a trapping device (5). The trapping device (5) is connected to the casing (1), the first tubing (2) and the second tubing (4) respectively through gas pipes. The trapping device (5) is connected to a gas - fired generator (6) through a gas pipe. The gas - fired generator (6) is connected to a compressor (7) through a gas pipe. The compressor (7) is connected to the first tubing (2) and the second tubing (4) respectively through gas pipes.

2. The device for enhancing liquid - carrying capacity of gas well according to claim 1, Characterized in that, A number of the gas - lift valves (3) are on the same vertical line.

3. The device for enhancing liquid - carrying capacity of gas well according to claim 1, Characterized in that, The trapping device (5) is a natural gas trapping rack.

4. The device for enhancing liquid - carrying capacity of gas well according to claim 1, Characterized in that, The trapping device (5) is a gas - liquid two - phase separator.

5. Method for combined drainage and gas production using the lifting device according to any one of claims 1 - 4, Characterized in that, Specifically as follows: S1: The gas well normally produces through the first tubing (2). As time goes by, the gas well gradually accumulates liquid, resulting in a decrease in production. Therefore, the second tubing (4) is pressured - lowered into the gas well, and natural gas produces through the second tubing (4), and the gas well produces continuously and stably again; S2: As time goes by, the wellbore accumulates liquid again. According to the production situation of each well, if the gas production of a certain well suddenly decreases, or there are signs of drowning, operate the trapping device (5) to take gas from the main pipe for separation. On the one hand, supply gas to the gas - fired generator for power generation, and on the other hand, supply gas to the compressor; S3: The high - pressure gas pressurized by the compressor (7) is injected into the annulus between the first tubing (2) and the second tubing (4) for combined drainage and gas production of the gas well until the gas well revives, and the gas well resumes the state of continuous production by self - carrying liquid relying on the second tubing (4); S4: Repeat S2 - S3 to carry out the measures of pressurization and multi - stage gas - lift valve gas - lift for the next liquid - accumulating gas well.

6. The method for combined drainage and gas production using the lifting device according to claim 5, Characterized in that, The specific method of water drainage and gas production in S3 is as follows: when the injection pressure reaches the set P1, the first-level gas lift valve at the top of the second oil pipe (4) is opened to discharge the accumulated liquid above the first-level gas lift valve in the wellbore of the second oil pipe (4); when the injection fracturing reaches P2, the accumulated liquid above the second-level gas lift valve is discharged; when the injection fracturing reaches P3, the accumulated liquid above the third-level gas lift valve is discharged, and so on, wherein P1 <P2<P3......<P n After the bottom gas lift valve is closed after lifting liquid, the gas well is completely revived, the liquid in the second oil pipe (4) is discharged, and the natural gas discharged synchronously is collected in the main pipe through the wellhead pipeline.

7. The method for combined drainage and gas production using the lifting device according to claim 5 or 6, Characterized in that, When the well is opened for production, all the gas - lift valves (3) are in the closed state.

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