Seabed supercritical carbon dioxide separation and reinjection integrated system and method

Abstract

The invention discloses a seabed supercritical carbon dioxide separation and reinjection integrated system and method, and relates to the technical field of offshore oil and gas exploitation, the system comprises a production well flow pipeline, a temperature and pressure control pipeline, a high-pressure underwater separator and an offshore floating type production oil storage ship; the production well flow pipeline is used for providing production well material flow inflow and is connected with the temperature and pressure control pipeline; the temperature and pressure control pipeline is used for adjusting the temperature and pressure of fluid in the production well flow pipeline, and an outlet of the temperature and pressure control pipeline is connected with the high-pressure underwater separator; the high-pressure underwater separator is used for separating well flow into a light hydrocarbon-rich gas phase, a hydrocarbon-rich liquid phase and a supercritical carbon dioxide-rich phase; the system can realize separation and reinjection of carbon dioxide in well flow oil and gas products by utilizing the physical property difference of supercritical carbon dioxide, so that the production treatment cost of an offshore floating type production oil storage ship is greatly reduced, and meanwhile, the recovery efficiency of an oil and gas field is improved by reinjection of carbon dioxide.

Description

Technical Field

[0001] The present invention relates to the technical field of marine oil and gas exploitation, and in particular to a seabed supercritical carbon dioxide separation and reinjection integrated system and method. Background Art

[0002] Some deepwater oil and gas reservoirs are characterized by high gas-oil ratio (GOR) and high CO2 content, and are usually accompanied by high productivity index. The traditional treatment solution is to pump the well flow from the production well to an offshore floating production storage and offloading vessel (FPSO), and then use a membrane permeation process to compress the gas, separate the CO2 and pump it back to the reinjection well. Fluids containing high concentrations of CO2 require large production facilities and complex gas processing systems, while the available space on offshore floating production storage and offloading vessels is limited, which limits the ability to process and store offshore oil and gas.

[0003] Carbon dioxide separation and reinjection are important links in the production process of deepwater oil and gas fields on the seabed. The existing methods for improving carbon dioxide separation and reinjection are mostly based on reducing the size of separation equipment and improving separation efficiency, but the production process is still to transport the well flow to the offshore floating production storage vessel for separation and reinjection. These methods cannot fundamentally increase the available space and improve the oil and gas processing and storage capacity, and the energy consumption is relatively high. In addition, there are three main separation methods for carbon dioxide separation: membrane separation, amine method, and supersonic separator. Among them, the membrane separation technology and amine method involve more equipment, which will greatly increase the operating cost of the offshore production platform; the supersonic separator has high requirements for process parameters and is difficult to apply to the actual offshore oil and gas field carbon dioxide separation process with dynamic component changes. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention provides an integrated system and method for seabed supercritical carbon dioxide separation and reinjection. The system can utilize the difference in physical properties of supercritical carbon dioxide to achieve carbon dioxide separation and reinjection in well flow oil and gas products, thereby greatly reducing the production and processing costs of offshore floating production storage and offloading vessels, and at the same time improving the recovery rate of oil and gas fields by reinjecting carbon dioxide.

[0005] The technical solution of the present invention is as follows: In a first aspect of the present invention, there is provided an integrated system for separation and reinjection of subsea supercritical carbon dioxide, comprising a subsea production well process pipeline, a temperature and pressure control pipeline and a high-pressure underwater separator, and an offshore floating production storage vessel; The production well process pipeline is used to provide production well logistics inflow and is connected to the temperature and pressure control pipeline; The temperature and pressure control pipeline is used to adjust the temperature and pressure of the fluid in the production well process pipeline, and its outlet is connected to the high-pressure underwater separator; The high-pressure underwater separator is used to separate the well logistics into a light hydrocarbon-rich gas phase, a hydrocarbon-rich liquid phase and a supercritical carbon dioxide-rich phase. The light hydrocarbon-rich gas phase is transported to an offshore floating production storage and offloading vessel through a gas phase process pipeline, the hydrocarbon-rich liquid phase is transported to an offshore floating production storage and offloading vessel through a liquid phase process pipeline, and the supercritical carbon dioxide-rich phase is transported to a reinjection process pipeline through a supercritical carbon dioxide process pipeline. In some embodiments of the present invention, the production well process pipeline includes a production well pipeline, and a well flow inlet valve, a first pressure sensor and a first temperature sensor are sequentially arranged on the production well pipeline.

[0006] In some embodiments of the present invention, the temperature and pressure control pipeline includes a compressor pipeline, a heat exchanger pipeline, a compressor bypass pipeline and a heat exchanger bypass pipeline.

[0007] In some embodiments of the present invention, a compressor inlet valve, an underwater compressor, a second pressure sensor, a compressor outlet valve and a first control valve are sequentially arranged on the compressor pipeline; a heat exchanger pipeline is connected to the position between the compressor outlet valve and the first control valve, and a first heat exchanger inlet valve, a second temperature sensor, a first heat exchanger, a third temperature sensor and a second heat exchanger inlet valve are sequentially arranged on the heat exchanger pipeline.

[0008] In some embodiments of the present invention, the first control valve is connected to the high-pressure underwater separator through the high-pressure underwater separator inlet valve, one end of the heat exchanger bypass pipeline is connected to the second heat exchanger inlet valve, and the other end is connected between the first control valve and the high-pressure underwater separator inlet valve; a heat exchanger bypass valve is arranged on the heat exchanger bypass pipeline. In some embodiments of the present invention, one end of the compressor bypass line is connected to the front end of the compressor inlet valve, and the other end is connected between the second heat exchanger inlet valve and the heat exchanger bypass valve.

[0009] In some embodiments of the present invention, the high-pressure underwater separator adopts a seabed horizontal gravity separator, and a diversion pipe is arranged in the high-pressure underwater separator. The inlet of the diversion pipe is located at the bottom of the supercritical carbon dioxide phase layer, and the diversion pipe is connected to the supercritical carbon dioxide process pipeline. In some embodiments of the present invention, a fourth temperature sensor, a second heat exchanger, a fifth temperature sensor, a fourth control valve, an injection pump and a reinjection well are sequentially arranged on the reinjection process pipeline.

[0010] In some embodiments of the present invention, a second control valve and a fifth control valve are respectively provided on the gas phase process pipeline and the liquid phase process pipeline.

[0011] In a second aspect of the present invention, a method for separating and reinjecting subsea supercritical carbon dioxide is provided, which is implemented using the system described in the first aspect and includes the following steps: Step 1: According to the temperature and pressure conditions of the well logistics, control the valve to adjust the flow of the well logistics to the corresponding pressure regulating and temperature regulating pipelines; Step 2: regulating the temperature and pressure of the well flow in the pipeline so that the temperature and pressure of the well flow meet the requirements for separating supercritical carbon dioxide; Step 3: Use a high-pressure underwater separator to introduce the light hydrocarbon-rich gas phase, the hydrocarbon-rich liquid phase and the supercritical carbon dioxide-rich phase into the corresponding gas phase process pipeline, the liquid phase process pipeline and the supercritical carbon dioxide process pipeline for separation and transportation treatment; Step 4: Control the supercritical carbon dioxide fluid to enter the reinjection process pipeline and adjust the fluid temperature to improve pumping efficiency.

[0012] One or more technical solutions of the present invention have the following beneficial effects: 1. The integrated system for separation and reinjection of subsea supercritical carbon dioxide provided by the present invention makes full use of reservoir conditions, adjusts the temperature and pressure to the optimal value according to the temperature and pressure changes of the well flow during the production process, realizes carbon dioxide separation and reinjection through the characteristics of supercritical carbon dioxide, directly improves the recovery rate, and does not need to transport carbon dioxide to an offshore floating production storage vessel, thereby realizing integrated processing of carbon dioxide separation and reinjection. This system can reduce carbon dioxide emissions, make full use of carbon dioxide, serve marine oil and gas production, combine carbon dioxide capture and storage with underwater separation technology, provide a solution for emission reduction and carbon reduction for marine oil and gas production, and help marine oil and gas production explore new paths and methods for energy conservation and emission reduction.

[0013] 2. The integrated seabed supercritical carbon dioxide separation and reinjection system provided by the present invention places equipment such as production well process pipelines, temperature and pressure control pipelines and high-pressure underwater separators underwater, and performs carbon dioxide separation on the seabed. There is no need to pump the carbon dioxide-containing fluid to an offshore floating production platform for treatment, which reduces energy consumption and realizes integrated treatment of carbon dioxide separation and reinjection.

[0014] 3. The integrated system for separation and reinjection of subsea supercritical carbon dioxide provided by the present invention fully utilizes reservoir energy and accurately regulates the temperature and pressure of the fluid by controlling the underwater compressor, heat exchanger and valves, so as to meet the requirements for efficient separation of supercritical carbon dioxide. At the same time, the stratification of the fluid in the separator can be calculated according to the fluid components, and the supercritical carbon dioxide diversion pipeline can be adjusted to obtain the best separation conditions and achieve the best separation effect.

[0015] 4. Based on the physical properties of supercritical carbon dioxide, the present invention fully utilizes the density difference between supercritical carbon dioxide and light hydrocarbons through a gravity separator to promote the separation of carbon dioxide, thereby reducing the processing burden of offshore floating production storage and offloading vessels and improving production efficiency; in addition, the present invention fully utilizes the properties of supercritical carbon dioxide after separation, uses a heat exchanger to adjust the fluid density to meet the reinjection conditions, improves pumping efficiency, and realizes the reinjection of carbon dioxide through an injection pump, thereby improving the recovery rate. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 It is a schematic diagram of the integrated system for separation and reinjection of subsea supercritical carbon dioxide of the present invention.

[0016] In the figure: 1, production well pipeline; 2, well flow inlet valve; 3, first pressure sensor; 4, first temperature sensor; 5, compressor inlet valve; 6, underwater compressor; 7, second pressure sensor; 8, compressor outlet valve; 9, first control valve; 10, first heat exchanger inlet valve; 11, second temperature sensor; 12, first heat exchanger; 13, third temperature sensor; 14, second heat exchanger inlet valve; 15, compressor bypass valve; 16, heat exchanger bypass valve; 17, high-pressure underwater separator inlet valve; 18, high-pressure underwater separator device; 19, supercritical carbon dioxide diversion pipeline; 20, liquid phase process pipeline; 21, supercritical carbon dioxide process pipeline; 22, gas phase process pipeline; 23, second control valve; 24, third control valve; 25, fourth control valve; 26, fourth temperature sensor; 27, second heat exchanger; 28, fifth temperature sensor; 29, fifth control valve; 30, injection pump; 31, reinjection well; 32, offshore floating production storage and offloading vessel; I, compressor pipeline; II, heat exchanger pipeline; III, compressor bypass pipeline; IV, heat exchanger bypass pipeline. DETAILED DESCRIPTION

[0017] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0018] Example 1 When separating carbon dioxide from an offshore floating production storage and offloading vessel, high-cost processing equipment and a large amount of energy consumption are required. In addition, when reinjecting carbon dioxide into the seabed, the carbon dioxide needs to be transported from the sea surface to the seabed, a process that also requires huge energy consumption and costs.

[0019] The inventors found that under appropriate pressure and temperature conditions, the hydrocarbon mixture system containing carbon dioxide exhibits complex phase behavior, and usually there is at least one two-phase region: a hydrocarbon-rich liquid phase and a carbon dioxide-rich light hydrocarbon phase. When the temperature exceeds the critical temperature (31.1 ° C) and the pressure exceeds the critical pressure (7.38 MPa), carbon dioxide is in a supercritical state, showing the dual physical properties of gas and liquid, with a density close to that of liquid and a viscosity similar to that of gas. Changes in temperature and pressure will cause density differences, so phase separation occurs under the action of gravity, so a high-pressure underwater gravity separator can be used for separation.

[0020] To this end, in a typical embodiment of the present invention, a subsea supercritical carbon dioxide separation and reinjection integrated system is provided, such as Figure 1 As shown, it includes the production well process pipeline, temperature and pressure control pipeline and high-pressure underwater separator 18 on the seabed, and the offshore floating production storage vessel 32; The production well process pipeline is used to provide production well logistics inflow and is connected to the temperature and pressure control pipeline; The temperature and pressure control pipeline is used to adjust the temperature and pressure of the fluid in the production well process pipeline, and its outlet is connected to the high-pressure underwater separator; The high-pressure underwater separator 18 is used to separate the well logistics into a light hydrocarbon-rich gas phase, a hydrocarbon-rich liquid phase and a supercritical carbon dioxide-rich phase. The light hydrocarbon-rich gas phase is transported to an offshore floating production storage and offloading vessel 32 via a gas phase process pipeline 22, the hydrocarbon-rich liquid phase is transported to an offshore floating production storage and offloading vessel 32 via a liquid phase process pipeline 20, and the supercritical carbon dioxide-rich phase is transported to a reinjection process pipeline via a supercritical carbon dioxide process pipeline 21.

[0021] The above system places the separation process of carbon dioxide on the seabed, avoiding the transportation of large amounts of carbon dioxide to the offshore floating production storage and offloading vessel, reducing the problems involved in pipeline flow assurance, while reducing the scale of the gas processing plant of the production storage and offloading vessel and enhancing the oil and gas storage capacity. In addition, utilizing the energy of the reservoir can reduce the energy consumption of controlling pressure and temperature. Since the outlet of the separated carbon dioxide is still in a high-pressure state, the injection pump during reinjection can smoothly complete the reinjection of carbon dioxide.

[0022] The above system improves the separation efficiency of supercritical carbon dioxide by adjusting the pressure and temperature of the well flow from the production well. The separated light hydrocarbon gas phase and hydrocarbon-rich liquid phase are transported to the offshore floating production storage vessel. The supercritical carbon dioxide is sent to the reinjection well by the injection pump after the fluid temperature is adjusted by the heat exchanger, thereby improving the recovery rate. After obtaining the produced fluid components, the system uses the difference in the physical properties of supercritical carbon dioxide to achieve the separation and reinjection of carbon dioxide in the well flow products. The system makes full use of the reservoir pressure, significantly reduces energy consumption, reduces the processing cost of the offshore floating platform, and increases production.

[0023] In this embodiment, the production well process pipeline includes a production well pipeline 1, on which a well flow inlet valve 2, a first pressure sensor 3 and a first temperature sensor 4 are sequentially arranged. The first pressure sensor 3 and the first temperature sensor 4 are respectively used to detect the pressure and temperature of the fluid in the production well process pipeline.

[0024] In this embodiment, the temperature and pressure control pipeline includes a compressor pipeline I, a heat exchanger pipeline II, a compressor bypass pipeline III and a heat exchanger bypass pipeline IV.

[0025] Furthermore, the compressor pipeline I is sequentially provided with a compressor inlet valve 5, an underwater compressor 6, a second pressure sensor 7, a compressor outlet valve 8 and a first control valve 9; the position between the compressor outlet valve 8 and the first control valve 9 is connected to the heat exchanger pipeline II, and the heat exchanger pipeline II is sequentially provided with a first heat exchanger inlet valve 10, a second temperature sensor 11, a first heat exchanger 12, a third temperature sensor 13 and a second heat exchanger inlet valve 14.

[0026] Furthermore, the first control valve 9 is connected to the high-pressure underwater separator 18 through the high-pressure underwater separator inlet valve 17, one end of the heat exchanger bypass pipe IV is connected to the second heat exchanger inlet valve 14, and the other end is connected between the first control valve 9 and the high-pressure underwater separator inlet valve 17; a heat exchanger bypass valve 16 is provided on the heat exchanger bypass pipe IV.

[0027] Furthermore, one end of the compressor bypass pipeline is connected to the front end of the compressor inlet valve 5 , and the other end is connected between the second heat exchanger inlet valve 14 and the heat exchanger bypass valve 16 .

[0028] By setting up the temperature and pressure control pipeline, the heat exchanger and the underwater compressor can be selectively used to adjust the temperature and pressure of the fluid according to the temperature and pressure of the well flow, so as to achieve the best conditions for separating supercritical carbon dioxide.

[0029] Specifically, when the fluid temperature and pressure meet the requirements for efficient separation of supercritical carbon dioxide, the fluid temperature is greater than the critical temperature of 31.1°C and the pressure is greater than the critical pressure of 7.38 MPa, all valves in the compressor pipeline I and the heat exchanger pipeline II are closed, and the compressor bypass valve 15 and the heat exchanger bypass valve 16 are opened, allowing the well flow to flow to the high-pressure underwater separator 18 through the high-pressure underwater separator inlet valve 17.

[0030] When the fluid pressure alone does not meet the requirements for efficient separation of supercritical carbon dioxide, all valves in the heat exchanger pipeline II are closed, the compressor inlet valve 5 is opened, the well flow is pressurized by the underwater compressor 6, and meets the requirements after being detected by the second pressure sensor 7. Subsequently, the compressor outlet valve 8 and the first control valve 9 are opened, allowing the well flow to flow into the high-pressure underwater separator 18 through the high-pressure underwater separator inlet valve 17.

[0031] When only the temperature of the fluid does not meet the requirements for efficient separation of supercritical carbon dioxide, all valves in the compressor pipeline I are closed, the second heat exchanger inlet valve 14 and the compressor bypass valve 15 are opened, the well flow is adjusted in temperature by the first heat exchanger 12, and meets the requirements after being detected by the second temperature sensor 11. The first control valve 9 and the first heat exchanger inlet valve 10 are opened, allowing the well flow to flow to the high-pressure underwater separator 18 through the high-pressure underwater separator inlet valve 17.

[0032] Specifically, when the fluid pressure and temperature do not meet the requirements for high-efficiency separation of supercritical carbon dioxide, the compressor inlet valve 5 is opened, the well flow is pressurized by the underwater compressor 6, and the pressure requirement is met after detection by the second pressure sensor 7. Subsequently, the compressor outlet valve 8 and the first heat exchanger inlet valve 10 are opened, the well flow is adjusted in temperature through the first heat exchanger 12, and the temperature requirement is met after detection by the third temperature sensor 13. Finally, the second heat exchanger inlet valve 14 and the heat exchanger bypass valve 16 are opened, so that the well flow flows to the high-pressure underwater separator 18 through the high-pressure underwater separator inlet valve 17.

[0033] Furthermore, the high-pressure underwater separator 18 adopts a seabed horizontal gravity separator, and a shunt pipe is arranged in the high-pressure underwater separator 18, the inlet of the shunt pipe is located at the bottom of the supercritical carbon dioxide phase layer, and the shunt pipe is connected to the supercritical carbon dioxide process pipeline 21. Supercritical carbon dioxide has the characteristics of high density, but its density is usually less than that of the oil phase and the water phase, so the supercritical carbon dioxide is separated from the gas phase, but floats on the liquid phase. The fluid in the high-pressure underwater separator 18 is divided into a light hydrocarbon-rich gas phase, a hydrocarbon-rich liquid phase, and a supercritical carbon dioxide-rich phase, and is discharged from the high-pressure underwater separator 18 from the corresponding process pipelines respectively. By arranging a supercritical carbon dioxide shunt pipe 19 in the high-pressure underwater separator 18, when the fluid pressure is too high, the content of light hydrocarbons in the liquid phase in the fluid will increase, but because its density is low and less than that of supercritical carbon dioxide, it will float on the supercritical carbon dioxide phase layer. The shunt pipe is pre-placed in the separator, and the inlet of the shunt pipe is highly arranged at the bottom of the supercritical carbon dioxide phase layer, thereby achieving efficient separation.

[0034] In this embodiment, the reinjection process pipeline is sequentially provided with a third control valve 24, a fourth temperature sensor 26, a second heat exchanger 27, a fifth temperature sensor 28, a fifth control valve 29, an injection pump 30 and a reinjection well 31. The fourth temperature sensor 26 is used to detect the temperature of the fluid. After the fluid passes through the second heat exchanger 27 to adjust the temperature, the fifth temperature sensor 28 detects the temperature of the fluid again. When the temperature meets the optimal reinjection condition, that is, when the temperature is lower than the critical temperature (31.1 ° C), the density of carbon dioxide further increases and is in a dense phase state. At this time, the pumping efficiency increases. When the efficiency reaches the optimum, the fifth control valve 29 is opened, and the fluid enters the reinjection well 31 through the injection pump 30. The reinjection process pipeline adjusts the fluid temperature by controlling the second heat exchanger 27, thereby changing the density of supercritical carbon dioxide, so that it can be re-injected into the reinjection well through the injection pump with higher pumping efficiency, thereby improving the recovery rate.

[0035] In this embodiment, the gas phase process pipeline 22 and the liquid phase process pipeline 20 are respectively provided with a second control valve 23 and a fourth control valve 25. The gas phase process pipeline 22 is connected to the offshore floating production storage and offloading vessel 32 to transport the light hydrocarbon gas phase separated by the separator, so as to realize the recovery of the light hydrocarbon gas phase and reduce the processing burden of the offshore floating production storage and offloading vessel on the gas phase; the liquid phase process pipeline 20 is connected to the offshore floating production storage and offloading vessel 32 to transport the liquid phase separated by the separator and the possible solid phase sand particles, so as to realize the recovery of the hydrocarbon-rich liquid phase and reduce the processing burden of the offshore floating production storage and offloading vessel on the liquid phase.

[0036] Example 2 In a typical embodiment of the present invention, a method for separating and reinjecting subsea supercritical carbon dioxide is provided, comprising the following steps: Step 1: According to the temperature and pressure conditions of the well logistics, control the valve to adjust the flow of the well logistics to the corresponding pressure regulating and temperature regulating pipelines; Step 2: regulating the temperature and pressure of the well flow in the pipeline so that the temperature and pressure of the well flow meet the requirements for separating supercritical carbon dioxide; Step 3: Use a high-pressure underwater separator to introduce the light hydrocarbon-rich gas phase, the hydrocarbon-rich liquid phase and the supercritical carbon dioxide-rich phase into the corresponding gas phase process pipeline, the liquid phase process pipeline and the supercritical carbon dioxide process pipeline for separation and transportation treatment; Step 4: Control the supercritical carbon dioxide fluid to enter the reinjection process pipeline and adjust the fluid temperature to improve pumping efficiency.

[0037] The above method adjusts the temperature and pressure to the optimal value according to the temperature and pressure changes of the well flow during the production process, realizes the separation and reinjection of carbon dioxide through the characteristics of supercritical carbon dioxide, directly improves the recovery rate, and does not need to transport carbon dioxide to the offshore floating production platform, thereby realizing the integrated treatment of carbon dioxide separation and reinjection. It can reduce carbon dioxide emissions, make full use of carbon dioxide, serve marine oil and gas production, provide a solution for emission reduction and carbon reduction for marine oil and gas production, and help marine oil and gas production explore new paths and methods for energy conservation and emission reduction.

[0038] Although the above describes the specific implementation mode of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art on the basis of the technical solution of the present invention without creative work are still within the scope of protection of the present invention.

Claims

1. A submarine supercritical carbon dioxide separation and reinjection integrated system, characterized in that: Including the production well process pipelines, temperature and pressure control pipelines and high-pressure underwater separators on the seabed, as well as offshore floating production storage vessels; The production well process pipeline is used to provide production well logistics inflow and is connected to the temperature and pressure control pipeline; The temperature and pressure control pipeline is used to adjust the temperature and pressure of the fluid in the production well process pipeline, and its outlet is connected to the high-pressure underwater separator; The high-pressure underwater separator is used to separate the well logistics into a light hydrocarbon-rich gas phase, a hydrocarbon-rich liquid phase and a supercritical carbon dioxide-rich phase. The light hydrocarbon-rich gas phase is transported to an offshore floating production storage and offloading vessel through a gas phase process pipeline, the hydrocarbon-rich liquid phase is transported to an offshore floating production storage and offloading vessel through a liquid phase process pipeline, and the supercritical carbon dioxide-rich phase is transported to a reinjection process pipeline through a supercritical carbon dioxide process pipeline.

2. The integrated system for separation and reinjection of subsea supercritical carbon dioxide according to claim 1, characterized in that: The production well process pipeline comprises a production well pipeline, on which a well flow inlet valve, a first pressure sensor and a first temperature sensor are sequentially arranged.

3. The integrated system for separation and reinjection of subsea supercritical carbon dioxide according to claim 1, characterized in that: The temperature and pressure control pipeline includes a compressor pipeline, a heat exchanger pipeline, a compressor bypass pipeline and a heat exchanger bypass pipeline.

4. The integrated system for separation and reinjection of subsea supercritical carbon dioxide according to claim 3, characterized in that: The compressor pipeline is provided with a compressor inlet valve, an underwater compressor, a second pressure sensor, a compressor outlet valve and a first control valve in sequence; the position between the compressor outlet valve and the first control valve is connected to the heat exchanger pipeline, and the heat exchanger pipeline is provided with a first heat exchanger inlet valve, a second temperature sensor, a first heat exchanger, a third temperature sensor and a second heat exchanger inlet valve in sequence.

5. The integrated system for separation and reinjection of subsea supercritical carbon dioxide according to claim 4, characterized in that: The first control valve is connected to the high-pressure underwater separator through the high-pressure underwater separator inlet valve, one end of the heat exchanger bypass pipeline is connected to the second heat exchanger inlet valve, and the other end is connected between the first control valve and the high-pressure underwater separator inlet valve; a heat exchanger bypass valve is arranged on the heat exchanger bypass pipeline.

6. The integrated system for separation and reinjection of subsea supercritical carbon dioxide according to claim 5, characterized in that: One end of the compressor bypass pipeline is connected to the front end of the compressor inlet valve, and the other end is connected between the second heat exchanger inlet valve and the heat exchanger bypass valve.

7. The integrated system for separation and reinjection of subsea supercritical carbon dioxide according to claim 1, characterized in that: The high-pressure underwater separator adopts a seabed horizontal gravity separator. A diversion pipeline is arranged in the high-pressure underwater separator. The inlet of the diversion pipeline is located at the bottom of the supercritical carbon dioxide phase layer. The diversion pipeline is connected to the supercritical carbon dioxide process pipeline.

8. The integrated system for separation and reinjection of subsea supercritical carbon dioxide according to claim 1, characterized in that: The reinjection process pipeline is sequentially provided with a fourth temperature sensor, a second heat exchanger, a fifth temperature sensor, a fourth control valve, an injection pump and a reinjection well.

9. The integrated system for separation and reinjection of subsea supercritical carbon dioxide according to claim 1, characterized in that: The gas phase process pipeline and the liquid phase process pipeline are respectively provided with a second control valve and a fifth control valve.

10. A method for separation and reinjection of subsea supercritical carbon dioxide, implemented by the system according to any one of claims 1 to 9, characterized in that: The following steps are involved: Step 1: According to the temperature and pressure conditions of the well logistics, control the valve to adjust the flow of the well logistics to the corresponding pressure regulating and temperature regulating pipelines; Step 2: regulating the temperature and pressure of the well flow in the pipeline so that the temperature and pressure of the well flow meet the requirements for separating supercritical carbon dioxide; Step 3: Use a high-pressure underwater separator to introduce the light hydrocarbon-rich gas phase, the hydrocarbon-rich liquid phase and the supercritical carbon dioxide-rich phase into the corresponding gas phase process pipeline, the liquid phase process pipeline and the supercritical carbon dioxide process pipeline for separation and transportation treatment; Step 4: Control the supercritical carbon dioxide fluid to enter the reinjection process pipeline and adjust the fluid temperature to improve pumping efficiency.

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