An integrated system and method for seabed supercritical carbon dioxide separation and reinjection

Abstract

The present invention discloses an integrated system and method for the separation and reinjection of submarine supercritical carbon dioxide, which relates to the technical field of marine oil and gas exploitation. The system comprises a production well process pipeline, a temperature and pressure control pipeline, a high-pressure underwater separator, and an offshore floating production storage and offloading vessel. The production well process pipeline is used to provide an inflow of production well logistics and is connected to the temperature and pressure control pipeline. The temperature and pressure control pipeline is used to regulate 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 system can utilize the differences in the physical properties of supercritical carbon dioxide to achieve the separation and reinjection of carbon dioxide from well flow oil and gas products, thereby significantly reducing the production and processing costs of the offshore floating production storage and offloading vessel, while increasing the oil and gas field recovery rate by reinjecting 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 submarine supercritical carbon dioxide separation and reinjection integrated system and method. Background Art

[0002] Some deepwater offshore oil and gas reservoirs are characterized by high gas-to-oil ratios (GOR) and high CO2 content, often accompanied by high productivity indexes. The traditional processing solution involves pumping well streams from production wells to offshore floating production storage and offloading vessels (FPSOs). The gas is then compressed using a membrane permeation process, the CO2 is separated, and re-pumped to the reinjection wells. Fluids containing high CO2 concentrations require large production facilities and complex gas processing systems, but the limited space available on offshore FPSOs limits offshore oil and gas processing and storage capabilities.

[0003] Carbon dioxide separation and reinjection are crucial steps in the production process of deepwater offshore oil and gas fields. Existing improvements to carbon dioxide separation and reinjection primarily focus on reducing the size of separation equipment and improving separation efficiency. However, the production process still involves transporting well flow to an offshore floating production storage and offloading vessel (FPSO) for separation and reinjection. These methods fail to fundamentally increase available space or improve oil and gas processing and storage capacity, and they also consume relatively high amounts of energy. Carbon dioxide separation primarily involves three methods: membrane separation, amine separation, and supersonic separators. Membrane separation and amine separation involve a significant amount of equipment, significantly increasing the operating costs of offshore production platforms. Supersonic separators have stringent process parameter requirements, making them difficult to apply to actual offshore oil and gas field carbon dioxide separation processes, where components undergo dynamic changes. Summary of the Invention

[0004] In response to the problems existing in the existing technology, the present invention provides an integrated system and method for the separation and reinjection of subsea supercritical carbon dioxide. The system can utilize the differences in the physical properties of supercritical carbon dioxide to achieve the separation and reinjection of carbon dioxide from well flow oil and gas products, thereby significantly reducing the production and processing costs of offshore floating production storage and offloading vessels, while increasing the recovery rate of oil and gas fields by reinjecting carbon dioxide.

[0005] The technical solutions of the present invention are as follows:

[0006] In a first aspect of the present invention, a subsea supercritical carbon dioxide separation and reinjection integrated system is provided, comprising a subsea production well process pipeline, a temperature and pressure control pipeline, a high-pressure underwater separator, and an offshore floating production storage and offloading vessel;

[0007] The production well process pipeline is used to provide logistics inflow to the production well and is connected to the temperature and pressure control pipeline;

[0008] 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;

[0009] 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.

[0010] 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 provided on the production well pipeline.

[0011] 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.

[0012] 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.

[0013] 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 provided on the heat exchanger bypass pipeline.

[0014] 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.

[0015] In some embodiments of the present invention, the high-pressure underwater separator adopts a seabed horizontal gravity separator, and a diversion pipe is placed 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.

[0016] In some embodiments of the present invention, 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.

[0017] 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.

[0018] 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:

[0019] Step 1: Control the valves and adjust the flow of the well logistics to the corresponding pressure regulating and temperature regulating pipelines according to the temperature and pressure conditions of the well logistics;

[0020] 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;

[0021] 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, liquid phase process pipeline, and supercritical carbon dioxide process pipeline for separation and transportation treatment;

[0022] Step 4: Control the supercritical carbon dioxide fluid to enter the reinjection process pipeline and adjust the fluid temperature to improve pumping efficiency.

[0023] One or more technical solutions of the present invention have the following beneficial effects:

[0024] 1. The integrated subsea supercritical carbon dioxide separation and reinjection system provided by the present invention fully utilizes reservoir conditions, adjusts the temperature and pressure to optimal values ​​according to the temperature and pressure changes of the well flow during the production process, and realizes carbon dioxide separation and reinjection through the characteristics of supercritical carbon dioxide, directly improving the recovery rate without the need to transport carbon dioxide to an offshore floating production storage and offloading vessel, thereby realizing integrated carbon dioxide separation and reinjection processing. This system can reduce carbon dioxide emissions, fully utilize carbon dioxide, serve marine oil and gas production, and combine carbon dioxide capture and storage with underwater separation technology to provide a solution for marine oil and gas production to reduce emissions and carbon dioxide, helping marine oil and gas production explore new paths and methods for energy conservation and emission reduction.

[0025] 2. The integrated subsea 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 processing, which reduces energy consumption while achieving integrated carbon dioxide separation and reinjection processing.

[0026] 3. The integrated submarine supercritical carbon dioxide separation and reinjection system 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 that it can meet the requirements of efficient separation of supercritical carbon dioxide. At the same time, the stratification of the fluid in the separator can be calculated based on 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.

[0027] 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 reinjection conditions, improves pumping efficiency, and realizes the reinjection of carbon dioxide through an injection pump, thereby increasing the recovery rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic diagram of the integrated system for separation and reinjection of subsea supercritical carbon dioxide according to the present invention.

[0029] 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. Subsea 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 1. Second control valve; 2. Third control valve; 2. Fourth control valve; 2. Fourth temperature sensor; 2. Second heat exchanger; 2. Fifth temperature sensor; 2. Fifth control valve; 3. Injection pump; 3. Reinjection well; 3. Offshore floating production storage and offloading vessel; Ⅰ. Compressor piping; Ⅱ. Heat exchanger piping; Ⅲ. Compressor bypass piping; Ⅳ. Heat exchanger bypass piping. DETAILED DESCRIPTION

[0030] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0031] Example 1

[0032] Separating carbon dioxide from an offshore floating production storage and offloading vessel requires high-cost processing equipment and a large amount of energy consumption. 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.

[0033] The inventors discovered that under appropriate pressure and temperature conditions, hydrocarbon mixtures containing carbon dioxide exhibit complex phase behavior, typically consisting of 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 enters a supercritical state, exhibiting dual physical properties of gas and liquid, with a density close to that of a liquid and a viscosity similar to that of a gas. Temperature and pressure changes cause density differences, leading to phase separation under the action of gravity. Therefore, high-pressure underwater gravity separators can be used for separation.

[0034] To this end, in a typical embodiment of the present invention, a submarine 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, as well as the offshore floating production storage and offloading vessel 32;

[0035] The production well process pipeline is used to provide logistics inflow to the production well and is connected to the temperature and pressure control pipeline;

[0036] 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;

[0037] 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 the offshore floating production storage and offloading vessel 32 through the gas phase process pipeline 22, the hydrocarbon-rich liquid phase is transported to the offshore floating production storage and offloading vessel 32 through the liquid phase process pipeline 20, and the supercritical carbon dioxide-rich phase is transported to the reinjection process pipeline through the supercritical carbon dioxide process pipeline 21.

[0038] This system places the CO2 separation process on the seafloor, avoiding the need to transport large quantities of CO2 to an offshore floating production storage and offloading vessel (FPSO). This reduces pipeline flow assurance issues, reduces the size of the FPSO's gas processing plant, and enhances oil and gas storage capacity. Furthermore, utilizing reservoir energy reduces the energy consumption associated with controlling pressure and temperature. Since the outlet of the separated CO2 remains at high pressure, the injection pump can smoothly reinject the CO2 during re-injection.

[0039] The system regulates the pressure and temperature of the well stream from the production well to improve the efficiency of supercritical CO2 separation. The separated light hydrocarbon gas phase and hydrocarbon-rich liquid phase are transported to an offshore floating production storage and offloading vessel. The supercritical CO2 is then regulated in a heat exchanger before being pumped into the reinjection well by an injection pump, thereby increasing oil recovery. After obtaining the components of the produced fluid, the system utilizes the differences in the physical properties of supercritical CO2 to separate and reinject CO2 from the well stream product. This system fully utilizes reservoir pressure, significantly reducing energy consumption, lowering processing costs on offshore floating platforms, and increasing production.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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 .

[0045] By setting up a temperature and pressure control pipeline, the heat exchanger and underwater compressor can be selectively used to adjust the temperature and pressure of the fluid according to the temperature and pressure conditions of the well flow, so as to achieve the optimal conditions for separating supercritical carbon dioxide.

[0046] 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.

[0047] When the fluid pressure alone fails to meet the requirements for efficient supercritical carbon dioxide separation, all valves in heat exchanger line II are closed, compressor inlet valve 5 is opened, and the well stream is pressurized by subsea compressor 6. After being tested by second pressure sensor 7, it meets the requirements. Subsequently, compressor outlet valve 8 and first control valve 9 are opened, allowing the well stream to flow through high-pressure subsea separator inlet valve 17 into high-pressure subsea separator 18.

[0048] When only the fluid temperature fails to meet the requirements for efficient supercritical carbon dioxide separation, all valves in compressor line I close, second heat exchanger inlet valve 14 and compressor bypass valve 15 open, and the well stream is adjusted in temperature by first heat exchanger 12. After being tested by second temperature sensor 11, it meets the requirements. First control valve 9 and first heat exchanger inlet valve 10 open, allowing the well stream to flow through high-pressure subsea separator inlet valve 17 to high-pressure subsea separator 18.

[0049] Specifically, when neither the fluid pressure nor the temperature meet the requirements for efficient supercritical carbon dioxide separation, the compressor inlet valve 5 opens, and the well stream is pressurized by the subsea compressor 6. The pressure is then measured by the second pressure sensor 7 to meet the required pressure. Subsequently, the compressor outlet valve 8 and the first heat exchanger inlet valve 10 open, and the well stream is temperature-adjusted by the first heat exchanger 12. The temperature is then measured by the third temperature sensor 13 to meet the required temperature. Finally, the second heat exchanger inlet valve 14 and the heat exchanger bypass valve 16 open, allowing the well stream to flow through the high-pressure subsea separator inlet valve 17 to the high-pressure subsea separator 18.

[0050] Furthermore, the high-pressure underwater separator 18 utilizes a seabed horizontal gravity separator. A diversion pipe is installed within the high-pressure underwater separator 18, the inlet of which is located at the bottom of the supercritical carbon dioxide phase layer. The diversion pipe is connected to the supercritical carbon dioxide process pipeline 21. Supercritical carbon dioxide has a high density, but its density is generally less than that of the oil phase and the water phase. Therefore, the supercritical carbon dioxide is separated from the gas phase but floats on the liquid phase. Within the high-pressure underwater separator 18, the fluid is divided into a light hydrocarbon-rich gas phase, a hydrocarbon-rich liquid phase, and a supercritical carbon dioxide-rich phase, and each is discharged from the high-pressure underwater separator 18 through the corresponding process pipeline. By installing a supercritical carbon dioxide diversion pipe 19 within the high-pressure underwater separator 18, when the fluid pressure is too high, the content of light hydrocarbons in the liquid phase of the fluid increases. However, due to its low density and less than that of supercritical carbon dioxide, it will float above the supercritical carbon dioxide phase layer. The diversion pipe is pre-installed within the separator, and the inlet of the diversion pipe is placed at a high altitude at the bottom of the supercritical carbon dioxide phase layer, thereby achieving efficient separation.

[0051] In this embodiment, the reinjection process pipeline is sequentially equipped 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 fluid temperature. After the fluid passes through the second heat exchanger 27 to adjust the temperature, the fifth temperature sensor 28 again detects the fluid temperature. When the temperature meets the optimal reinjection conditions, that is, when the temperature is below the critical temperature (31.1°C), the carbon dioxide density further increases and enters a dense phase state, increasing pumping efficiency. When the efficiency reaches the optimal level, the fifth control valve 29 opens, 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 the supercritical carbon dioxide, allowing it to be re-injected into the reinjection well through the injection pump at a higher pumping efficiency, thereby improving the recovery factor.

[0052] In this embodiment, a second control valve 23 and a fourth control valve 25 are provided on the gas-phase process pipeline 22 and the liquid-phase process pipeline 20, respectively. The gas-phase process pipeline 22 is connected to an offshore floating production storage and offloading vessel 32 to transport the light hydrocarbon gas phase separated by the separator, thereby recovering the light hydrocarbon gas phase and reducing the gas phase processing burden on the offshore floating production storage and offloading vessel. 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 any solid sand particles present, thereby recovering the hydrocarbon-rich liquid phase and reducing the liquid phase processing burden on the offshore floating production storage and offloading vessel.

[0053] Example 2

[0054] In a typical embodiment of the present invention, a method for separating and reinjecting subsea supercritical carbon dioxide is provided, comprising the following steps:

[0055] Step 1: Control the valves and adjust the flow of the well logistics to the corresponding pressure regulating and temperature regulating pipelines according to the temperature and pressure conditions of the well logistics;

[0056] 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;

[0057] 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, liquid phase process pipeline, and supercritical carbon dioxide process pipeline for separation and transportation treatment;

[0058] Step 4: Control the supercritical carbon dioxide fluid to enter the reinjection process pipeline and adjust the fluid temperature to improve pumping efficiency.

[0059] This method adjusts the temperature and pressure of the well stream to optimal values ​​based on changes in temperature and pressure during the production process. It then leverages the properties of supercritical carbon dioxide to separate and reinject carbon dioxide, directly improving oil recovery without the need to transport the carbon dioxide to an offshore floating production platform. This integrated process of separation and reinjection can reduce carbon dioxide emissions, fully utilize carbon dioxide, and serve marine oil and gas production, providing a solution for emissions reduction and carbon reduction in marine oil and gas production and helping marine oil and gas production explore new paths and methods for energy conservation and emission reduction.

[0060] Although the above describes the specific embodiments 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 any 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 seabed production well process pipelines, temperature and pressure control pipelines and high-pressure underwater separators, as well as offshore floating production storage and offloading vessels; The production well process pipeline is used to provide logistics inflow to the production well 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 via a gas phase process pipeline, the hydrocarbon-rich liquid phase is transported to an offshore floating production storage and offloading vessel via a liquid phase process pipeline, and the supercritical carbon dioxide-rich phase is transported to a reinjection process pipeline via a supercritical carbon dioxide process pipeline. The production well process pipeline includes a production well pipeline, and the production well pipeline is sequentially provided with a well flow inlet valve, a first pressure sensor and a first temperature sensor; The temperature and pressure control pipeline includes a compressor pipeline, a heat exchanger pipeline, a compressor bypass pipeline and a heat exchanger bypass pipeline; The compressor pipeline is sequentially provided with a compressor inlet valve, an underwater compressor, a second pressure sensor, a compressor outlet valve and a first control valve; 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 sequentially provided with a first heat exchanger inlet valve, a second temperature sensor, the first heat exchanger, a third temperature sensor and a second heat exchanger inlet valve; The control process of the temperature and pressure control pipeline includes: When the fluid pressure alone does not meet the requirements for efficient separation of supercritical carbon dioxide, all valves in the heat exchanger pipeline are closed, the compressor inlet valve is opened, the well flow is pressurized by the underwater compressor, and is tested by the second pressure sensor to meet the requirements; 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 are closed, the second heat exchanger inlet valve and the compressor bypass valve are opened, and the well flow is adjusted in temperature by the first heat exchanger and tested by the second temperature sensor to meet the requirements; When the fluid pressure and temperature do not meet the requirements for high-efficiency separation of supercritical carbon dioxide, the compressor inlet valve opens, the well flow is pressurized by the underwater compressor, and meets the pressure requirement after being detected by the second pressure sensor; then, the compressor outlet valve and the first heat exchanger inlet valve are opened, the well flow is temperature-adjusted through the first heat exchanger, and meets the temperature requirement after being detected by the third temperature sensor.

2. The integrated system for separation and reinjection of subsea supercritical carbon dioxide according to claim 1, 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 provided on the heat exchanger bypass pipeline.

3. The integrated system for separation and reinjection of subsea supercritical carbon dioxide according to claim 1, 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.

4. 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 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. The diversion pipe is connected to the supercritical carbon dioxide process pipeline.

5. 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.

6. 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.

7. A method for separating and reinjecting submarine supercritical carbon dioxide, implemented using the system according to any one of claims 1 to 6, characterized in that: The following steps are involved: Step 1: Control the valves and adjust the flow of the well logistics to the corresponding pressure regulating and temperature regulating pipelines according to the temperature and pressure conditions of the well logistics; 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, liquid phase process pipeline, and 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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