An apparatus and method for underwater gas production

Abstract

This invention provides an underwater gas extraction device and method, relating to the technical field of gas extraction devices. It includes a separation pipe with a spiral separation plate fixedly installed on its inner wall. The spiral separation plate has a spiral-shaped plate structure, and a separation fan is provided on its side. The separation fan has a liquid accumulation tank, and a heating column is provided on its side, connected to a heating device. A gas-liquid separation mechanism is provided inside the separation pipe to separate and collect the liquid in the collected gas-liquid mixture. In this invention, a structure combining an expanded-diameter transition pipe and a spiral separation plate is used. The expanded-diameter transition pipe has a small radius at its connection to the gas extraction pipe and a large radius at its connection to the separation pipe. This allows the gas-liquid mixture, pressurized by the pressurization and transport device, to release some pressure and slow down its flow rate before entering the separation pipe, preventing insufficient separation due to excessive flow rate or pressure.

Description

Technical Field

[0001] This invention belongs to the technical field of gas extraction devices, specifically relating to an extraction device and method for underwater gas extraction. Background Technology

[0002] Subsea natural gas extraction begins with locating the subsea natural gas reservoir using marine seismic exploration and underwater detection equipment. Then, specialized equipment such as semi-submersible drilling platforms are used to drill subsea production wells, and the wellbore is sealed to prevent natural gas leakage or seawater intrusion. In the initial stage of extraction, the natural gas enters the subsea gathering and transmission pipeline network based on the reservoir's own pressure. If the pressure is insufficient, underwater pressurization equipment is used to assist in increasing production. Subsequently, the natural gas is transported to floating production storage and offloading (FPSO) facilities or offshore fixed platforms to complete preliminary treatments such as dehydration, desalination, and impurity removal. Finally, it is transported to onshore processing plants through subsea gas pipelines, thus realizing the entire process of subsea natural gas from exploration and extraction to onshore utilization.

[0003] Current underwater gas extraction devices have been found to have at least the following technical problems:

[0004] First, in subsea gas production operations, the fluid extracted from the gas reservoir often exists in the form of a gas-liquid mixture. This mixture mainly contains natural gas, formation water, and trace amounts of condensate oil. During the transportation of the mixture to the separation stage through the gas production pipeline, in order to ensure that the mixture can overcome underwater resistance and be transported smoothly, a pressurization and transportation device is usually used to pressurize the gas-liquid mixture in the gas production pipeline. This results in the mixture being under high pressure and flowing at a high speed throughout the transportation process. If the high-pressure, high-speed gas-liquid mixture directly enters the subsequent processing pipeline, it will rapidly impact the separation components due to the lack of buffering and regulation. Larger droplets in the mixture that are not separated in advance will continue to be transported with the gas flow, which may cause impact wear on the inner wall of the gas production pipeline and the subsequent gas flow processing components, shortening the service life of the equipment.

[0005] Secondly, in underwater gas production operations, the natural gas extracted from underwater gas reservoirs is naturally accompanied by formation water and trace amounts of condensate oil, forming a gas-liquid mixture. When the natural gas is transported along the pipeline, the pressure inside the pipeline gradually decreases due to the special underwater environment, and the temperature of the underwater environment itself remains at a low level, forming a low-temperature and low-pressure transportation condition. Under this condition, the trace amounts of heavy hydrocarbons remaining in the natural gas are prone to loss of stability and condense on the inner wall of the transportation pipeline to form deposits. Since the operation and maintenance of underwater pipelines need to cope with the complex underwater environment, the maintenance operation is more difficult. If the condensate continues to accumulate, it will affect the effective flow cross section of the pipeline, which may reduce the transportation efficiency of natural gas and pose a challenge to the stable development of underwater gas production operations. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides an extraction apparatus and method for underwater gas extraction.

[0007] An underwater gas extraction device includes a gas extraction pipeline, a pressurization and transportation device, a separation pipeline, a transportation pipeline, a recovery pipeline, a liquid collection tank, and a liquid sedimentation tank; the gas extraction pipeline, the separation pipeline, and the transportation pipeline are connected sequentially; a pressurization and transportation device (a device that provides pressure to the extracted gas and transports it within the pipeline, containing a booster pump) is fixedly installed through the gas extraction pipeline; a liquid sedimentation tank is located below the separation pipeline, and the liquid sedimentation tank is connected to the liquid collection tank via the recovery pipeline;

[0008] A gas-liquid separation mechanism is installed inside the separation pipeline. The gas-liquid separation mechanism is used to separate and collect the liquid in the collected gas-liquid mixture. An airflow processing mechanism is installed inside the transport pipeline. The airflow processing mechanism is used to heat the separated airflow and clean the pipe wall to prevent blockage.

[0009] The gas-liquid separation mechanism includes a mounting shaft, a separation fan, and a spiral separation plate; the airflow processing mechanism includes an airflow plate and a heating column; a spiral separation plate is fixedly installed on the inner wall of the separation pipe, a separation fan is provided on the side of the spiral separation plate, and a liquid accumulation tank is provided on the separation fan; the separation fan is connected to the airflow plate through the mounting shaft; a heating column is provided on the airflow plate.

[0010] Furthermore, a one-way valve is installed inside the gas extraction pipeline; the spiral separator plate is a spiral-shaped plate structure.

[0011] Furthermore, an expansion transition pipe is fixedly installed at one end of the gas extraction pipeline, and the expansion transition pipe is fixedly installed with the separation pipeline; a reduction transition pipe is fixedly installed at one end of the transport pipeline, and the reduction transition pipe is fixedly installed with the separation pipeline.

[0012] Furthermore, the separation fan is provided with a liquid guide channel.

[0013] Furthermore, the separation pipe has an opening at its bottom, through which it is connected to a liquid sedimentation tank; the liquid sedimentation tank has an outlet on its side wall, which is connected to a liquid collection tank via a recovery pipe.

[0014] Furthermore, flexible scrapers are fixedly installed on both sides of the airflow plate.

[0015] Furthermore, the airflow plate and the flexible scraper are connected by an elastic material.

[0016] Furthermore, the airflow plate has a window, and the heating column is fixedly installed inside the window on the airflow plate.

[0017] Furthermore, the transport pipeline and the gas extraction tree are equipped with multiple throttling valves.

[0018] A method of using an underwater gas extraction device includes the following steps:

[0019] S1: Start the gas production device. The gas-liquid mixture containing natural gas, formation water and trace amounts of condensate oil begins to be transported through the gas production pipeline. The pressurization and transportation device pressurizes the gas-liquid mixture in the pipeline to provide continuous transportation power. The pressurized gas-liquid mixture enters the separation pipeline through the expansion transition pipe. The radius of the connection end between the expansion transition pipe and the gas production pipeline is small, while the radius of the connection end between the expansion transition pipe and the separation pipeline is large.

[0020] S2: The gas-liquid mixture entering the separation pipe impacts the spiral separation plate and rotates along the plate under the guidance of the spiral plate. Because the liquid density is greater than that of the gas, the liquid is subjected to stronger centrifugal force when rotating. Larger droplets are thrown towards the side wall of the separation pipe and then flow along the pipe wall. They enter the liquid sedimentation tank below through the bottom opening of the separation pipe. The remaining gas flow containing smaller droplets continues to be transported forward. When it flows through the separation fan, the gas flow drives the mixture to rotate further. The smaller droplets are thrown towards the edge of the fan blade or the pipe wall through the liquid guide groove on the separation fan under the action of centrifugal force, and finally also flow into the liquid sedimentation tank.

[0021] S3: After separation, the natural gas enters the transportation pipeline through the reduced-diameter transition pipe on the side wall of the separation pipeline. The radius of the connection end between the reduced-diameter transition pipe and the separation pipeline is larger than that of the transportation pipeline. During this process, the natural gas pressure increases. When the gas flow passes through the spiral guide plate at the front end of the gas flow plate in the transportation pipeline, it drives the gas flow plate to rotate around the fixed installation axis. The flexible scrapers on both sides of the gas flow plate rotate synchronously through the elastic material, scraping off the heavy hydrocarbons condensed on the pipe wall of the transportation pipeline. When the gas flow passes through the window on the gas flow plate, it is heated by the heating column connected to the heating device in the window. The processed natural gas is transported to the gas production tree above the fixed installation axis. After the extraction rate is adjusted by the throttle valve in the gas production tree, it enters the subsequent production stage. The liquid collected in the liquid sedimentation tank is filtered for impurities through the liquid outlet and transported to the liquid collection tank through the recovery pipeline for temporary storage, awaiting subsequent centralized processing.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] In this invention, a combined structure of an expanded-diameter transition pipe and a spiral separation plate is used. The expanded-diameter transition pipe has a small radius at the connection end with the gas sampling pipe and a large radius at the connection end with the separation pipe. This allows the gas-liquid mixture, after being pressurized by the pressurization and transportation device, to release some pressure and slow down its flow rate before entering the separation pipe, thus avoiding insufficient separation due to excessive flow rate and pressure. The spiral separation plate is a spiral plate structure that guides the gas-liquid mixture, after its flow rate has slowed down, to rotate along the plate. By utilizing the centrifugal force generated by the density difference between the liquid and the gas, larger droplets in the mixture are thrown towards the side wall of the separation pipe, achieving preliminary gas-liquid separation.

[0024] In this invention, a separation fan with a liquid guide channel is provided. This separation fan is located inside the separation pipe and can receive the gas-liquid mixture after preliminary separation by the spiral separation plate. When the gas flow containing smaller droplets flows through the separation fan, it will drive the mixture to rotate further. Because the density of the small droplets is greater than that of the gas, they are subjected to stronger centrifugal force when rotating. The liquid guide channel can accurately guide these small droplets, causing them to be quickly thrown towards the edge of the fan blade or the wall of the separation pipe, preventing the small droplets from being transported with the gas flow. The separated small droplets can flow smoothly into the liquid sedimentation tank below, effectively reducing the trace amount of liquid remaining in the natural gas and achieving deep gas-liquid separation.

[0025] In this invention, an airflow plate with a spiral guide plate at the front end and a flexible scraper connected to the airflow plate by an elastic material are used. When the separated natural gas flows through the airflow plate, the airflow can naturally push the airflow plate to rotate around the fixed installation axis by the structural characteristics of the spiral guide plate, thereby driving the flexible scraper to rotate synchronously. The connection method of the elastic material allows the flexible scraper to fit tightly against the inner wall of the transportation pipeline. Even if there is a slight curvature in the inner wall of the pipeline, it can thoroughly scrape off the deposits formed by the condensation of heavy hydrocarbons, preventing pipeline blockage from the source. This can ensure that the natural gas transportation channel is always smooth, avoiding problems such as sudden increase in transportation pressure and interruption of the extraction process caused by blockage. It provides a stable guarantee for the subsequent natural gas transportation to the gas tree and maintains the overall extraction efficiency.

[0026] In this invention, a heating column connected to a heating device is used. When the separated natural gas passes through the airflow plate window, the heating column can release heat instantly to simultaneously heat the airflow. Considering the characteristics of pressure and temperature drop in underwater gas extraction environments, this design can specifically prevent trace amounts of heavy hydrocarbons in the airflow from condensing into precipitated oil due to environmental changes. This avoids precipitated oil from mixing with natural gas and affecting subsequent processing or use, ensuring the purity of natural gas. It also prevents precipitated oil from adhering to the inner wall of the transport pipeline, reducing the frequency of cleaning and maintenance due to the accumulation of deposits on the pipe wall, lowering equipment operation and maintenance costs. At the same time, it forms a synergistic protection with the flexible scraper, further ensuring the long-term smooth operation of the transport pipeline. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0028] Figure 2 This is a schematic diagram of the transportation pipeline structure of the present invention;

[0029] Figure 3 This is a schematic diagram of the pressurized transport device of the present invention;

[0030] Figure 4 This is a schematic diagram of the split-fan structure of the present invention;

[0031] Figure 5 This is a schematic diagram of the airflow plate structure of the present invention;

[0032] Figure 6 This is a schematic diagram of the liquid collection tank structure of the present invention;

[0033] Figure 7 This is a schematic diagram of the gas extraction pipeline structure of the present invention;

[0034] Figure 8 This is a schematic diagram of the separation pipe structure of the present invention.

[0035] The components in the diagram are as follows: 1. Gas extraction pipeline; 2. Pressurization and transportation device; 3. Expansion transition pipe; 4. Separation pipeline; 5. Reduction transition pipe; 6. Transportation pipeline; 7. Recovery pipeline; 8. Liquid collection tank; 9. Liquid sedimentation tank; 10. Mounting and fixing shaft; 11. Gas extraction tree; 12. Separation fan; 13. Liquid guide channel; 14. Airflow plate; 15. Heating column; 16. Flexible scraper; 17. Spiral separation plate; 18. Liquid outlet. Detailed Implementation

[0036] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and should not be construed as limiting the scope of the invention.

[0037] like Figures 1-8 As shown in the figure, this embodiment of an underwater gas extraction device includes a gas extraction pipeline 1, a pressurization and transportation device 2, a separation pipeline 4, a transportation pipeline 6, a recovery pipeline 7, a liquid collection tank 8, and a liquid sedimentation tank 9. The gas extraction pipeline 1, the separation pipeline 4, and the transportation pipeline 6 are connected sequentially. The transportation pipeline 6 is connected to a gas extraction tree 11, and the gas extraction tree 11 is equipped with multiple throttling valves. The pressurization and transportation device 2 is fixedly installed through the gas extraction pipeline 1. A liquid sedimentation tank 9 is located below the separation pipeline 4, and the liquid sedimentation tank 9 is connected to the liquid collection tank 8 through the recovery pipeline 7. Figure 3 , Figure 4 , Figure 6 , Figure 7 and Figure 8 As shown, in this embodiment, one end of the gas sampling pipeline 1 is connected to the gas sampling device. A one-way valve is fixedly installed inside the gas sampling pipeline 1. The one-way valve inside the gas sampling pipeline 1 is used to prevent gas backflow and "gas lock" and to prevent fluid backflow and impact on the equipment when the transmission stops. A pressurized transport device 2 is fixedly installed through the gas sampling pipeline 1. The pressurized transport device 2 is used to provide power to the gas-liquid mixture or the separated gas-liquid mixture.

[0038] A gas-liquid separation mechanism is installed inside the separation pipe 4. The gas-liquid separation mechanism is used to separate and collect the liquid in the collected gas-liquid mixture. An airflow processing mechanism is installed inside the transport pipe 6. The airflow processing mechanism is used to heat the separated airflow and clean the pipe wall to prevent blockage.

[0039] In this embodiment, the gas-liquid separation mechanism includes a mounting shaft 10, a separation fan 12, and a spiral separation plate 17; the gas flow processing mechanism includes an airflow plate 14 and a heating column 15; a spiral separation plate 17 is fixedly installed on the inner wall of the separation pipe 4. In this embodiment, the spiral separation plate 17 is a spiral plate structure. Since gas extraction is carried out underwater, the subsea gas reservoir naturally contains associated formation water and a small amount of condensate oil. During gas extraction, these liquids are extracted along with the natural gas, forming a gas-liquid mixture containing natural gas, formation water, and trace amounts of condensate oil. The spiral separation plate 17 is used to initially separate larger droplets, such as formation water, from the extracted gas-liquid mixture. The spiral separation plate 17 has a separation fan 12 on its side, and a liquid guide channel 13 on the separation fan 12. In this embodiment, the separation fan 12 is used to separate smaller droplets, such as condensate oil, from the pre-treated mixture; the separation fan 12 is connected to the airflow plate 14 through the mounting shaft 10, and flexible scrapers 16 are fixedly installed on both sides of the airflow plate 14. The airflow plate 14 and the flexible scrapers 16 are connected by an elastic material. The airflow plate 14 has a window, and the heating column 15 is fixedly installed in the window on the airflow plate 14. In this embodiment, the heating column 15 is used to heat the separated airflow to prevent trace amounts of heavy hydrocarbons in the natural gas from condensing into precipitated oil due to pressure and temperature drop.

[0040] like Figure 7 As shown, an expansion transition pipe 3 is fixedly installed at one end of the gas extraction pipeline 1, and the expansion transition pipe 3 is fixedly installed with the separation pipeline 4; a reduction transition pipe 5 is fixedly installed at one end of the transport pipeline 6, and the reduction transition pipe 5 is fixedly installed with the separation pipeline 4. An opening is provided at the bottom of the separation pipeline 4, and the separation pipeline 4 is connected to the liquid sedimentation tank 9 through the opening; a liquid outlet 18 is provided on the side wall of the liquid sedimentation tank 9, and the liquid outlet 18 is connected to the liquid collection tank 8 through a recovery pipeline 7.

[0041] It should be noted that an expansion transition pipe 3 is fixedly installed at one end of the gas sampling pipeline 1. The expansion transition pipe 3 is fixedly installed with the separation pipeline 4, and the separation fan 12 is located inside the separation pipeline 4. The radius of the expansion transition pipe 3 connecting to the gas sampling pipeline 1 is small, while the radius of its connection to the separation pipeline 4 is large. This design of the expansion transition pipe 3 allows the gas-liquid mixture to release some pressure and slow down its flow rate when it enters the separation pipeline 4 through the expansion transition pipe 3 after being pressurized by the pressurization and transport device 2 through the gas sampling pipeline 1. This allows for better subsequent separation. When the gas flow enters the separation pipeline 4, it impacts the spiral separation plate 17 and is guided by the spiral plate to rotate along the plate. Because the liquid density is greater than that of the gas, the centrifugal force during rotation is stronger, and larger droplets are thrown towards the side wall of the separation pipeline 4, while the gas remains in the center. Afterward, the liquid is discharged through the liquid accumulation groove on the liquid outlet 18, and the gas continues to be transported forward. This achieves preliminary separation. A liquid guide channel 13 is provided on the separator fan 12. Airflow through the separator fan 12 causes the gas-liquid mixture to rotate faster. Small droplets, being denser than gas, experience stronger centrifugal force during rotation and are thrown towards the edge of the fan blades or the pipe wall through the liquid guide channel 13, thus separating the droplets. An opening is provided at the bottom of the separator pipe 4, and a liquid sedimentation tank 9 is fixedly installed below the separator pipe 4. The liquid sedimentation tank 9 collects droplets from the side wall through the opening at the bottom of the separator pipe 4. An opening is also provided on the side wall of the liquid sedimentation tank 9, and a liquid outlet 18 is fixedly installed on this opening. The liquid outlet 18 filters impurities from the liquid. A recovery pipe 7 is fixedly installed on the side of the liquid sedimentation tank 9, and a liquid collection tank 8 is fixedly installed at the side end of the recovery pipe 7. The separated liquid mixes in the liquid sedimentation tank 9 and is transported through the recovery pipe 7 to the liquid collection tank 8 for temporary storage, awaiting further processing. Figure 1 , Figure 2 , Figure 4 , Figure 5 and Figure 7As shown, the airflow processing mechanism also includes a reduced-diameter transition pipe 5, which is fixedly installed on the side wall of the separation pipe 4. A transport pipe 6 is fixedly installed on the side wall of the reduced-diameter transition pipe 5. Since the radius of the connection between the reduced-diameter transition pipe 5 and the separation pipe 4 is larger, while the radius of the connection between the reduced-diameter transition pipe 5 and the transport pipe 6 is smaller, when the separated natural gas enters the transport pipe 6 from the separation pipe 4 through the reduced-diameter transition pipe 5, the gas pressure will increase. A mounting and fixing shaft 10 is rotatably installed on the transport pipe 6. The separation fan 12 is rotatably installed on the mounting and fixing shaft 10. An airflow plate 14 is rotatably installed on the mounting and fixing shaft 10. The front end of the airflow plate 14 is a spiral guide plate. When the airflow passes through the front end of the airflow plate 14, it can drive the entire airflow plate 14 to rotate. Flexible scrapers 16 are fixedly installed on both sides of the airflow plate 14. The airflow plate 14 and the flexible scrapers 16 are connected by a spring. The natural gas flow contains heavy hydrocarbons from the subsea gas reservoir, which easily condense on the side wall of the transport pipeline 6. The airflow drives the airflow plate 14 to rotate. The flexible scraper 16 installed on the side wall of the airflow plate 14 can scrape off the condensate on the pipe wall of the transport pipeline 6. The airflow plate 14 has windows for airflow to pass through. The heating column 15 is fixedly installed in the window on the airflow plate 14. When the airflow passes through the window on the airflow plate 14, it will be heated by the heating column 15 to prevent the trace heavy hydrocarbons in the airflow from condensing into precipitated oil due to the decrease in pressure and temperature. A gas production tree 11 is installed above the mounting and fixing shaft 10. The gas production tree 11 is equipped with multiple throttle valves. The gas production tree 11 can adjust the extraction rate of the gas-liquid mixture through the throttle valves. The separated natural gas will be transported to the gas production tree 11 through the transport pipeline 6, and then transported to the subsequent working steps.

[0042] Working principle:

[0043] The first step is to start the gas production unit. The gas-liquid mixture containing natural gas, formation water, and trace amounts of condensate oil is transported through the gas production pipeline 1. The one-way valve in the gas production pipeline 1 can prevent gas backflow and "gas lock" and avoid fluid backflow impacting the equipment when the transport stops. The pressurization and transport device 2 pressurizes the gas-liquid mixture in the pipeline to provide continuous transport power. The pressurized gas-liquid mixture enters the separation pipeline 4 through the expansion transition pipe 3. The radius of the connection between the expansion transition pipe 3 and the gas production pipeline 1 is small, while the radius of the connection between the expansion transition pipe 3 and the separation pipeline 4 is large. During this process, the mixture releases some pressure and slows down the flow rate, creating conditions for the subsequent gas-liquid separation process.

[0044] In the second step, the gas-liquid mixture entering the separation pipe 4 impacts the spiral separation plate 17 and rotates along the plate under the guidance of the spiral plate. Because the liquid density is greater than that of the gas, the liquid is subjected to stronger centrifugal force when rotating. Larger droplets are thrown towards the side wall of the separation pipe 4 and then flow along the pipe wall. They enter the liquid sedimentation tank 9 below through the bottom opening of the separation pipe 4. The remaining gas flow containing smaller droplets continues to be transported forward. When it flows through the separation fan 12, the gas flow drives the mixture to rotate further. The smaller droplets are thrown towards the edge of the fan blade or the pipe wall through the liquid guide groove 13 on the separation fan 12 under the action of centrifugal force, and finally also flow into the liquid sedimentation tank 9, completing the deep separation of gas and liquid.

[0045] In the third step, the separated natural gas enters the transport pipeline 6 through the narrowing transition pipe 5 on the side wall of the separation pipeline 4. The radius of the connection end between the narrowing transition pipe 5 and the separation pipeline 4 is larger than that of the connection end between the narrowing transition pipe 5 and the transport pipeline 6. During this process, the natural gas pressure increases. When the gas flow passes through the spiral guide plate at the front end of the gas flow plate 14 in the transport pipeline 6, it drives the gas flow plate 14 to rotate around the mounting fixed shaft 10. The flexible scrapers 16 connected by elastic material on both sides of the gas flow plate 14 rotate synchronously to scrape off the heavy hydrocarbons condensed on the pipe wall of the transport pipeline 6 to prevent the pipeline from being blocked. At the same time, when the gas flow passes through the window on the gas flow plate 14, it is heated by the heating column 15 connected to the heating device in the window to prevent the trace heavy hydrocarbons in the gas flow from condensing into precipitated oil due to the decrease in pressure and temperature. The processed natural gas is transported to the gas extraction tree 11 above the mounting fixed shaft 10. After the extraction rate is adjusted by the throttle valve in the gas extraction tree 11, it enters the subsequent production stage. The liquid collected in the liquid sedimentation tank 9 is filtered for impurities through the liquid outlet 18 and transported to the liquid collection tank 8 through the recovery pipeline 7 for temporary storage, waiting for subsequent centralized processing.

[0046] The embodiments of the present invention are given for illustrative and descriptive purposes only, and are not intended to be exhaustive or to limit the invention to the forms disclosed. Many modifications and variations will be apparent to those skilled in the art. The embodiments were chosen and described in order to better illustrate the principles and practical application of the invention, and to enable those skilled in the art to understand the invention and to design various embodiments with various modifications suitable for a particular purpose.

Claims

1. A gas extraction device for underwater gas extraction, characterized in that, It includes a gas extraction pipeline (1), a pressurized transport device (2), a separation pipeline (4), a transport pipeline (6), a recovery pipeline (7), a liquid collection tank (8), and a liquid sedimentation tank (9); the gas extraction pipeline (1), the separation pipeline (4), and the transport pipeline (6) are connected in sequence; the pressurized transport device (2) is fixedly installed through the gas extraction pipeline (1); a liquid sedimentation tank (9) is set below the separation pipeline (4), and the liquid sedimentation tank (9) is connected to the liquid collection tank (8) through the recovery pipeline (7); A gas-liquid separation mechanism is provided inside the separation pipe (4). The gas-liquid separation mechanism is used to separate and collect the liquid in the collected gas-liquid mixture. An airflow processing mechanism is provided inside the transport pipe (6). The airflow processing mechanism is used to heat the separated airflow and clean the pipe wall to prevent blockage. The gas-liquid separation mechanism includes a mounting shaft (10), a separation fan (12), and a spiral separation plate (17); the airflow processing mechanism includes an airflow plate (14) and a heating column (15); a spiral separation plate (17) is fixedly installed on the inner wall of the separation pipe (4), and a separation fan (12) is provided on the side of the spiral separation plate (17), and a liquid accumulation tank is provided on the separation fan (12); the separation fan (12) is connected to the airflow plate (14) through the mounting shaft (10); a heating column (15) is provided on the airflow plate (14); An expansion transition pipe (3) is fixedly installed at one end of the gas extraction pipeline (1), and the expansion transition pipe (3) is fixedly installed with the separation pipeline (4); The radius of the connection between the expanded diameter transition pipe and the gas production pipeline is small, while the radius of the connection between the pipe and the separation pipeline is large. The front end of the airflow plate is a spiral guide plate; The separation fan (12) is provided with a liquid guide channel (13); Flexible scrapers (16) are fixedly installed on both sides of the airflow plate (14).

2. The extraction apparatus for underwater gas extraction as described in claim 1, characterized in that, A one-way valve is installed inside the gas extraction pipeline (1); the spiral separation plate (17) is a spiral plate structure.

3. The extraction apparatus for underwater gas extraction as described in claim 1, characterized in that, A reduced diameter transition pipe (5) is fixedly installed at one end of the transport pipeline (6), and the reduced diameter transition pipe (5) is fixedly installed with the separation pipeline (4).

4. The extraction apparatus for underwater gas extraction as described in claim 1, characterized in that, The separation pipe (4) has an opening at the bottom, and the separation pipe (4) is connected to the liquid sedimentation tank (9) through the opening; the liquid sedimentation tank (9) has an outlet (18) on its side wall, and the outlet (18) is connected to the liquid collection tank (8) through the recovery pipe (7).

5. The extraction apparatus for underwater gas extraction as described in claim 1, characterized in that, The airflow plate (14) and the flexible scraper (16) are connected by an elastic material.

6. The extraction apparatus for underwater gas extraction as described in claim 1, characterized in that, A window is provided on the airflow plate (14), and the heating column (15) is fixedly installed in the window on the airflow plate (14).

7. The extraction apparatus for subsea gas extraction as described in claim 1, characterized in that, The transport pipeline (6) and the gas extraction tree (11) are provided with multiple throttling valves.

8. The method of using the extraction apparatus for subsea gas extraction according to any one of claims 1 to 7, characterized in that, Includes the following steps: S1: Start the gas production device. The gas-liquid mixture containing natural gas, formation water and trace amounts of condensate oil is transported through the gas production pipeline (1). The pressurization and transportation device (2) pressurizes the gas-liquid mixture in the pipeline to provide continuous transportation power. The pressurized gas-liquid mixture enters the separation pipeline (4) through the expansion transition pipe (3). The radius of the connection between the expansion transition pipe (3) and the gas production pipeline (1) is small, and the radius of the connection between the expansion transition pipe (3) and the separation pipeline (4) is large. S2: The gas-liquid mixture entering the separation pipe (4) impacts the spiral separation plate (17) and rotates along the plate under the guidance of the spiral plate. Because the liquid density is greater than that of the gas, the liquid is subjected to stronger centrifugal force when rotating. Larger droplets are thrown towards the side wall of the separation pipe (4) and then flow along the pipe wall. They enter the liquid sedimentation tank (9) below through the bottom opening of the separation pipe (4). The remaining gas flow containing smaller droplets continues to be transported forward. When it flows through the separation fan (12), the gas flow drives the mixture to rotate further. Smaller droplets are thrown towards the edge of the fan blade or the pipe wall through the liquid guide groove (13) on the separation fan (12) under the action of centrifugal force, and finally also flow into the liquid sedimentation tank (9). S3: After separation, the natural gas enters the transport pipeline (6) through the reduced-diameter transition pipe (5) on the side wall of the separation pipeline (4). The radius of the connection end between the reduced-diameter transition pipe (5) and the separation pipeline (4) is large, while the radius of the connection end with the transport pipeline (6) is small. During this process, the natural gas pressure increases. When the gas flow passes through the spiral guide plate at the front end of the airflow plate (14) in the transport pipeline (6), it drives the airflow plate (14) to rotate around the fixed mounting axis (10). The flexible scrapers (16) on both sides of the airflow plate (14) connected by elastic material rotate synchronously to scrape off the gas. The heavy hydrocarbons condensed on the pipe wall of the pipeline (6) are heated by the heating column (15) connected to the heating device in the window when the gas flows through the airflow plate (14). The treated natural gas is transported to the gas production tree (11) above the fixed shaft (10). After the extraction volume is adjusted by the throttle valve in the gas production tree (11), it enters the subsequent production stage. The liquid collected in the liquid sedimentation tank (9) is filtered for impurities through the liquid outlet (18) and then transported to the liquid collection tank (8) through the recovery pipeline (7) for temporary storage, waiting for subsequent centralized processing.

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