Semiclosed brayton cycle power generation and oil displacement system and method

Abstract

The present application relates to a kind of power generation and oil displacement system and method based on brayton cycle, to improve oil recovery, reduce oil displacement cost, and realize efficient power generation.The system includes combustion chamber, turbine, mechanical energy output device, water separator, carbon dioxide compression device.Fuel in the combustion chamber is efficiently combusted with the participation of oxygen, generating cycle working medium, which enters the turbine to do work;The water separator receives the cycle working medium from the outlet of the turbine and separates carbon dioxide and / or water vapor, and then performs carbon dioxide flooding and / or water flooding according to the specific conditions of the reservoir.Carbon dioxide compression device is connected with water separator, and carbon dioxide that is not discharged to oil field is compressed by carbon dioxide compression device and returned to combustion chamber for semi-closed brayton cycle.

Description

Technical Field

[0001] This invention relates to the fields of oil extraction and power generation technology, and more specifically, to a power generation and oil displacement system based on a semi-closed Brayton cycle. Background Technology

[0002] Carbon dioxide enhanced oil recovery (COLOR) technology is an important means of improving oil recovery. This technology injects carbon dioxide into the oil reservoir, utilizing the dissolving and expanding effects of carbon dioxide to reduce the viscosity and increase the fluidity of the crude oil, thereby enhancing oil recovery. However, despite its widespread use in oil extraction, traditional COLOR technology still faces a major challenge: the high cost of carbon dioxide extraction and the need for specialized production and transportation facilities.

[0003] Meanwhile, waterflooding, another common method for enhancing oil recovery, is relatively simple in principle, technologically mature, and low in cost. This technology involves continuously injecting water into the oil reservoir, using the natural pressure and driving force of the water to gradually drive the crude oil into the production well, thus achieving effective oil extraction. However, waterflooding technology has high requirements for reservoir permeability. If the reservoir permeability is poor, the injected water may bypass the crude oil and flow directly to the production well, forming a phenomenon known as water channeling, which severely affects the oil recovery efficiency.

[0004] Researchers have been seeking new methods to overcome the drawbacks of the two technologies mentioned above, aiming to reduce costs while further improving efficiency. Utilizing fuel combustion to produce carbon dioxide and water is a promising solution, but how to efficiently generate and utilize these combustion products, avoid resource waste, and reduce negative environmental impacts remains a crucial research challenge. Summary of the Invention

[0005] To address the above problems, this invention provides a power generation and oil recovery system based on a semi-closed Brayton cycle. This system uses carbon dioxide and water vapor generated from fuel combustion for power generation and oil recovery operations. This not only significantly improves oil recovery rates and reduces the costs of carbon dioxide and water-driven oil recovery, but also achieves high-efficiency power generation, enhancing the overall economic and environmental benefits of the system.

[0006] The semi-closed Brayton cycle power generation and oil displacement system provided by this invention includes:

[0007] The combustion chamber is used to burn fuel and produce a circulating working fluid, which is a mixture including carbon dioxide and water vapor.

[0008] The turbine is connected to the outlet of the combustion chamber, receives the circulating working fluid from the outlet of the combustion chamber and performs work;

[0009] A mechanical energy output device, connected to the output end of a turbine, and uses the turbine to generate energy by doing work.

[0010] The water separator receives the circulating working fluid from the turbine outlet. The circulating working fluid is separated into carbon dioxide, liquid water and / or water vapor by the water separator. The carbon dioxide, liquid water and / or water vapor are discharged to the external oil field through the outlet of the water separator.

[0011] The carbon dioxide compression unit is connected to the water separator. The carbon dioxide compression unit is used to compress carbon dioxide that is not discharged to the oil field. The carbon dioxide compressed by the carbon dioxide compression unit is returned to the combustion chamber for a semi-closed Brayton cycle.

[0012] This technical solution, by combining a semi-closed Brayton cycle power generation and oil displacement system, provides a highly efficient and flexible integrated solution for oil displacement and power generation, deepening the scope and depth of energy utilization. Both carbon dioxide and water vapor possess excellent dissolving and diffusing capabilities, enabling them to penetrate the oil reservoir and effectively dissolve and displace crude oil, thereby improving oil displacement efficiency and oil recovery. The water separator can be flexibly adjusted and selected based on the specific reservoir conditions, employing either "carbon dioxide flooding," "water flooding," or a "synergistic effect of both." This flexibility ensures the system can be integrated with various complex reservoirs, significantly improving its applicability, greatly optimizing economic costs, and enhancing oil recovery. More importantly, this technical solution generates carbon dioxide through fuel combustion, which can be used for both power generation and oil displacement, eliminating the need for dedicated carbon dioxide production and transportation equipment. It allows for "on-demand" generation and is therefore more flexible and practical.

[0013] Preferably, the carbon dioxide in the circulating working fluid at the combustion chamber outlet of the semi-closed Brayton cycle power generation and oil displacement system provided by the present invention is supercritical carbon dioxide.

[0014] According to this technical solution, when the carbon dioxide emitted from the combustion chamber is in a supercritical state, it can reduce the turbine inlet temperature to a certain extent, thereby reducing the design difficulty and manufacturing cost of the turbine. This not only extends the turbine's service life but also improves the overall reliability of the system. Due to its unique physical properties, such as low viscosity, good fluidity, and strong diffusivity, supercritical carbon dioxide penetrates and diffuses more easily in oil reservoirs than ordinary carbon dioxide, thus more effectively displacing crude oil from the formation. Simultaneously, the miscibility pressure between supercritical carbon dioxide and crude oil is lower, meaning that miscible displacement can be achieved at lower pressures. The miscible crude oil has lower viscosity and higher fluidity, making it easier to displace, thereby improving oil displacement efficiency. Supercritical carbon dioxide flooding technology is not only applicable to conventional reservoirs but also to low-permeability and ultra-low-permeability reservoirs. These reservoirs are typically difficult to exploit using traditional methods, while supercritical carbon dioxide flooding technology can significantly improve their recovery rates.

[0015] Preferably, the semi-closed Brayton cycle power generation and oil displacement system provided by the present invention further includes an air separator connected to the inlet of the combustion chamber, wherein the air separator separates oxygen from the air and provides it to the combustion chamber.

[0016] According to this technical solution, the high-purity oxygen separated by the air separator is transported to the combustion chamber through the oxygen outlet, providing an oxygen-rich environment for fuel combustion in the combustion chamber and further improving fuel combustion efficiency.

[0017] Preferably, the semi-closed Brayton cycle power generation and oil displacement system provided by the present invention further includes an oil displacement pretreatment device. The inlet of the oil displacement pretreatment device is connected to a water separator, and the outlet is connected to an oil field. It is used to regulate the pressure, temperature, and chemical content of carbon dioxide, liquid water, and / or water vapor entering the oil field.

[0018] According to this technical solution, the carbon dioxide, liquid water, and / or water vapor separated by the water separator pass through an oil displacement pretreatment unit before being sent to the oilfield. The pretreatment unit regulates the pressure and temperature of the carbon dioxide, liquid water, and water vapor entering the oilfield, and adds chemical agents to ensure that the process parameters for oil displacement are met, achieving efficient oil displacement. This unit can store a certain amount of carbon dioxide and water, and can select from various oil displacement methods, such as carbon dioxide flooding, water flooding, or a synergistic effect of both, depending on geological conditions, process parameters, and other on-site conditions.

[0019] Preferably, the semi-closed Brayton cycle power generation and oil displacement system provided by the present invention further includes a regenerator. The circulating working fluid output by the turbine exchanges heat with the oxygen separated by the air separator and the carbon dioxide returned to the combustion chamber in the regenerator, and then the oxygen and carbon dioxide enter the combustion chamber.

[0020] According to this technical solution, after preheating through heat exchange within the regenerator, oxygen and carbon dioxide can reach and maintain a high temperature more quickly in subsequent combustion steps, reducing heat loss caused by temperature gradients. The efficient combustion process reduces temperature fluctuations within the combustion chamber, resulting in a more uniform heat distribution and further improving the system's thermal efficiency and energy utilization. Simultaneously, the introduction of the regenerator to recover heat allows for flexible adjustment of the temperature of the circulating working fluid used in oil displacement, enhancing the oil displacement effect.

[0021] Preferably, the semi-closed Brayton cycle power generation and oil displacement system provided by the present invention further includes a multi-way valve, which has a first port, a second port, a third port and a fourth port;

[0022] The water separator includes:

[0023] The first water separator separates water vapor and carbon dioxide from the circulating working fluid from the regenerator. The water vapor is discharged to the external oil field through the water outlet of the first water separator, and the carbon dioxide outlet of the first water separator is connected to the first port of the multi-way valve.

[0024] The second water separator cools the circulating working fluid from the regenerator and separates liquid water and carbon dioxide. The carbon dioxide outlet of the second water separator is connected to the second port of the multi-way valve.

[0025] The third and fourth ports of the multi-way valve are connected to the carbon dioxide compression unit and the oil field, respectively.

[0026] According to the technical solution, carbon dioxide from the first water separator and the second water separator is either compressed by a multi-way valve and sent to a carbon dioxide compression device and finally returned to the combustion chamber to participate in the circulation, or sent to the gas injection well of the oil field to participate in the oil displacement process.

[0027] Preferably, the multi-directional valve switches according to the reservoir conditions of the oilfield to control the carbon dioxide flow rate at the third and fourth ports.

[0028] According to this technical solution, the multi-way valve regulates the flow direction of carbon dioxide. Depending on the specific conditions of the oilfield, it can selectively divert carbon dioxide from the first and second water separators through the third and fourth ports and send it in different directions. Through the cooperation of the multi-way valve and the two water separators, various oil displacement methods can be selected based on the field conditions, such as carbon dioxide flooding, water flooding, or a synergistic effect of both.

[0029] Preferably, the semi-closed Brayton cycle power generation and oil displacement system provided by the present invention is provided with a gas splitter in the pipe section from the carbon dioxide compression device to the combustion chamber to return carbon dioxide, which is connected to the outlet of the carbon dioxide compression device. The gas splitter diverts a portion of the carbon dioxide compressed by the carbon dioxide compression device out of the semi-closed Brayton cycle to regulate the amount of carbon dioxide in the semi-closed Brayton cycle.

[0030] According to this technical solution, the system can utilize compressed carbon dioxide more effectively through a gas splitter. When it is necessary to increase power generation or improve oil displacement efficiency, the system can increase the amount of carbon dioxide in the cycle by reducing the amount of carbon dioxide diverted, thereby enhancing the system's flexibility and reliability. The carbon dioxide diverted from the semi-closed Brayton cycle by the gas splitter has high purity, making it very suitable for carbon capture technology, thus improving the overall utilization efficiency of carbon dioxide while optimizing cycle performance.

[0031] Furthermore, a gas mixer is installed in the pipe section that returns carbon dioxide from the carbon dioxide compression unit to the combustion chamber. The gas mixer is connected to the outlet of the gas distributor and the outlet of the air separator. The carbon dioxide sent out by the gas distributor and the oxygen separated by the air separator are first mixed in the gas mixer and then introduced into the combustion chamber through the regenerator.

[0032] According to this technical solution, the mixture of carbon dioxide and oxygen forms a combustion-supporting stream (ensuring that the oxygen concentration is within the combustible range), which can further improve the combustion efficiency of fuel compared to pure oxygen.

[0033] Furthermore, the carbon dioxide compression device used in the semi-closed Brayton cycle power generation and oil displacement system provided by the present invention is a carbon dioxide compression pump.

[0034] According to this technical solution, the carbon dioxide compression pump further reduces the requirements for equipment compared to the traditional carbon dioxide compressor, so that the compression equipment does not need to operate near the critical point, ensuring efficient and long-term stable operation of the cycle, and reducing the number of equipment downtimes and maintenance.

[0035] Furthermore, the combustion chamber used in this system is a high-pressure combustion chamber.

[0036] According to this technical solution, under high pressure, the flame temperature can be increased, the radiation coefficient enhanced, thereby increasing combustion intensity and heat transfer efficiency, thus making fuller use of the chemical energy in the fuel. This not only improves the calorific value utilization rate of the fuel and avoids energy waste, but also reduces the emission of harmful gases produced by incomplete combustion, such as carbon monoxide and unburned fuel, which is in line with the environmental protection concept of energy conservation and emission reduction.

[0037] Furthermore, based on the efficient combustion environment provided by the high-pressure combustion chamber, the fuel used in this system can be natural gas, liquefied petroleum gas, and / or gasified gas.

[0038] According to this technical solution, the diverse fuel options enable its wide applicability in various environments. This gives the system extremely high flexibility. Different regions can choose suitable fuels based on their own resource conditions and needs.

[0039] The present invention also provides a semi-closed Brayton cycle power generation and oil displacement method, comprising the following steps:

[0040] The combustion step involves the combustion of fuel in a combustion chamber to produce a circulating working fluid, which is a mixture of carbon dioxide and water vapor.

[0041] In the power-doping process, the turbine receives the circulating working fluid from the outlet of the combustion chamber and performs work.

[0042] In the oil displacement step, the circulating working fluid is separated into carbon dioxide, liquid water and / or water vapor by a water separator. The carbon dioxide, liquid water and / or water vapor are discharged to the external oil field through the outlet of the water separator to carry out carbon dioxide oil displacement and / or water displacement operations.

[0043] In the compression cycle step, the carbon dioxide that is not discharged to the oil field is compressed by the carbon dioxide compression device to obtain compressed carbon dioxide, which is then returned to the combustion chamber for a semi-closed Brayton cycle.

[0044] Preferably, the semi-closed Brayton cycle power generation and oil displacement method provided by the present invention further includes a reheating step, in which oxygen, compressed carbon dioxide and fuel exchange heat with the circulating working fluid in the reheater before entering the combustion chamber to participate in combustion. Attached Figure Description

[0045] Figure 1 This is a schematic diagram of the semi-closed Brayton cycle power generation and oil displacement system according to the first embodiment of the present invention.

[0046] Figure 2 This is a schematic diagram of the semi-closed Brayton cycle power generation and oil displacement system according to the second embodiment of the present invention.

[0047] Figure 3 This is a flowchart of a semi-closed Brayton cycle power generation and oil displacement method according to the first and second embodiments of the present invention.

[0048] Figure label:

[0049] Turbine 1; Regenerator 2; First water separator 12; Second water separator 3; Multi-way valve 4; Gas distributor 6; First circulating pump 5; Second circulating pump 8; Gas mixer 7; Air separator 9; Combustion chamber 10; Mechanical energy output device 11; Oil field 14; Oil displacement pretreatment device 13. Detailed Implementation

[0050] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0051] [First Implementation Method]

[0052] Please see Figure 1 The diagram shown is a schematic diagram of a semi-closed Brayton cycle power generation and oil displacement system according to an embodiment of the present invention.

[0053] In this embodiment, the power generation and oil displacement system includes: turbine 1, regenerator 2, first water separator 12, second water separator 3, multi-way valve 4, first circulation pump 5, gas distributor 6, gas mixer 7, second circulation pump 8, air separator 9, combustion chamber 10, mechanical energy output device 11, and oil displacement pretreatment device 13.

[0054] Combustion chamber 10 has a fuel inlet, an oxygen inlet, a first circulating working fluid outlet, and a separated material return port. Fuel and oxygen enter combustion chamber 10 through the fuel inlet and oxygen inlet, respectively, and are combusted in combustion chamber 10 to generate a high-temperature, high-pressure circulating working fluid (mainly composed of carbon dioxide and water vapor). This high-temperature, high-pressure circulating working fluid is output from the first circulating working fluid outlet and sent to turbine 1.

[0055] Turbine 1 has a circulating working fluid inlet, a second circulating working fluid outlet, and a mechanical energy output end. The circulating working fluid inlet of turbine 1 is connected to the first circulating working fluid outlet of combustion chamber 10. The function of turbine 1 is to convert the thermal energy of the circulating working fluid (mainly composed of carbon dioxide and water vapor) generated by fuel combustion in combustion chamber 10 into mechanical energy by doing work.

[0056] The mechanical energy output end of turbine 1 is connected to mechanical energy output device 11, which converts the mechanical energy output by turbine into electrical energy and / or kinetic energy.

[0057] In some implementations, the mechanical energy output device may be a generator.

[0058] The regenerator 2 includes a first circulating working fluid channel, a second circulating channel, and a third air channel. The circulating working fluid (mainly composed of carbon dioxide and water vapor) output from the turbine 1 enters the first circulating working fluid channel of the regenerator 2, providing heat to the regenerator. The inlet of the second circulating channel is connected to the outlet of the second circulating pump 8, and the outlet of the second circulating channel is connected to the separator return port of the combustion chamber 10, used to provide combustion-supporting gas for the cycle. The inlet of the third air channel is connected to one outlet of the air separator 9, and the outlet of the third air channel is connected to the oxygen inlet of the combustion chamber 10, used to provide preheated oxygen to the combustion chamber 10. The function of the regenerator 2 is to transfer the heat of the circulating working fluid in the first circulating working fluid channel to the medium entering the second circulating channel and the oxygen in the third air channel through heat exchange.

[0059] After the circulating working fluid output from turbine 1 enters the inlet of the first circulating working fluid channel of the self-regenerating regenerator 2, it is divided into a first stream and a second stream at the outlet of the first circulating working fluid channel. The first stream flows into the first water separator 12, and the second stream flows into the second water separator 3.

[0060] The first water separator 12 is provided with a first separation port and a second separation port. The first water separator 12 separates carbon dioxide and water vapor in the circulating working fluid of the first stream through membrane separation or adsorption separation. The water vapor is sent to the oil field and discharged through the first separation port.

[0061] The second water separator 3 cools and separates the circulating working fluid in the second stream into carbon dioxide and liquid water. The separated liquid water is discharged through the outlet of the second water separator 3, while the separated carbon dioxide is sent to the oil field or to the first circulating pump 5 for compression through the outlet of the second water separator 3 via the multi-way valve 4 and finally returned to the combustion chamber 10 to participate in the circulation.

[0062] The carbon dioxide flowing from the second separation port of the first water separator 12 and the outlet of the second water separator 3 is collected into a multi-way valve 4. The multi-way valve 4 has a first port, a second port, a third port, and a fourth port. The second separation port of the first water separator 12 is connected to the first port of the multi-way valve 4; the outlet of the second water separator 3 is connected to the second port of the multi-way valve; the third and fourth ports of the multi-way valve are connected to the first circulation pump 5 and the oil field 14, respectively. When water-driven oil recovery is used, the carbon dioxide separated from the two water separators is no longer discharged to the oil field, but is discharged to the first circulation pump 5 through the multi-way valve 4. After being compressed by the first circulation pump 5, it is circulated back to the combustion chamber 10 and enters through the separation return port of the combustion chamber 10, achieving stable flow in a semi-closed Brayton cycle. The function of the multi-way valve 4 is to regulate the flow direction of carbon dioxide, selectively sending carbon dioxide from the first water separator 12 and the second water separator 3 either to the first circulation pump 5 for compression and ultimately back to the combustion chamber 10 for circulation, or to the gas injection wells in the oil field 14 for oil recovery.

[0063] Optionally, the semi-closed Brayton cycle power generation and oil displacement system of this embodiment also includes an oil displacement pretreatment device 13. The two inlets of the oil displacement pretreatment device 13 are respectively connected to the second separation port of the first water separator 12 and the fourth port of the multi-way valve 4, and the only outlet is connected to the oil field. The function of the oil displacement pretreatment device 13 is to regulate the pressure, temperature, and chemical content of carbon dioxide and / or water entering the oil field to ensure the achievement of optimal oil displacement process parameters.

[0064] Optionally, in this embodiment, the first circulation pump 5 of the semi-closed Brayton cycle power generation and oil displacement system is indirectly connected to the combustion chamber 10, and the compressed carbon dioxide is circulated through a series of components. These components specifically include: a gas distributor 6, a gas mixer 7, a second circulation pump 8, and an air separator 9.

[0065] The inlet of gas splitter 6 is connected to the outlet of the first circulating pump 5, used to split and purify the compressed working fluid (mainly carbon dioxide) to regulate the working fluid content in the Brayton cycle system. The purified working fluid (carbon dioxide) from gas splitter 6 enters gas mixer 7, where it mixes with oxygen from air separator 9 to form a combustion-supporting gas. This combustion-supporting gas is preheated by regenerator 2 and then enters the separator return port of combustion chamber 10 to participate in the semi-closed Brayton cycle. The portion of the working fluid split by gas splitter 6 that leaves the circulation system contains carbon dioxide with high purity, which can also be used for carbon capture.

[0066] The air separator 9 has an inlet that is connected to the outside atmosphere, and two outlets that are connected to the third air flow channel inlet of the regenerator 2 and the inlet of the gas mixer 7, respectively. After the outside air is separated by the air separator 9, pure oxygen can be obtained. Part of the pure oxygen is sent to the gas mixer 7 to mix with the working fluid (carbon dioxide) after being diverted and purified by the gas distributor 6 to form a combustion-supporting stream. The other part is preheated by the regenerator 2 and sent to the oxygen inlet of the combustion chamber 10 to provide pure oxygen for fuel combustion, ensuring that the combustion process is efficient and clean.

[0067] Through the above methods, the semi-closed Brayton cycle power generation and oil displacement system provided in this embodiment enhances the oil displacement effect and improves crude oil recovery by utilizing the excellent solubility and expansion properties of supercritical carbon dioxide, especially when dealing with low-permeability and heavy oil reservoirs. At the same time, the semi-closed Brayton cycle power generation and oil displacement system provided in this embodiment also overcomes the drawbacks of traditional carbon dioxide flooding operations, such as high carbon dioxide acquisition costs and the need for specialized production and transportation facilities. Furthermore, the water separator design allows for flexible selection of the oil displacement mode according to reservoir characteristics, effectively optimizing costs and improving recovery efficiency. Simultaneously, utilizing the supercritical state reduces turbine inlet temperature, simplifies turbine design, lowers manufacturing costs, extends service life, and further improves the reliability of the entire system.

[0068] [Second Implementation Method]

[0069] A schematic diagram of the semi-closed Brayton cycle power generation and oil displacement system and method in the second embodiment of the present invention is shown below. Figure 2 As shown. Its structure is basically the same as the semi-closed Brayton cycle power generation and oil displacement system in the first embodiment, the difference being that the first water separator 12 is omitted in this embodiment, simplifying the system structure. That is, the circulating working fluid output from turbine 1 enters through the inlet of the first circulating working fluid channel of the regenerator 2, and flows entirely into the second water separator 3 without splitting at the outlet of the first circulating working fluid channel. The second water separator 3 cools the circulating working fluid and separates liquid water and carbon dioxide. The carbon dioxide outlet of the second water separator 3 is connected to the second port of the multi-way valve; the drain outlet of the second water separator 3 leads to the oil field.

[0070] The first and second embodiments together provide a semi-closed Brayton cycle power generation and oil displacement method, referenced Figure 3 The power generation and oil displacement method includes the following steps:

[0071] In the combustion step, the fuel is burned in the combustion chamber 10 to produce a circulating working fluid, which is a mixture including carbon dioxide and water vapor;

[0072] In the power-doping process, turbine 1 receives the circulating working fluid from the outlet of combustion chamber 10 and performs work;

[0073] In the reheating step, oxygen and compressed carbon dioxide exchange heat with the circulating working fluid in the reheater 2 before entering the combustion chamber 10 to participate in combustion.

[0074] In the oil displacement step, the circulating working fluid is separated into carbon dioxide, liquid water and / or water vapor by water separators 3 and 12. The carbon dioxide, liquid water and / or water vapor are discharged to the external oil field 14 through the outlet of water separators 3 and 12 to carry out carbon dioxide oil displacement and / or water displacement operations.

[0075] In the compression cycle step, the supercritical carbon dioxide that was not discharged to oil field 14 is compressed and then processed by a series of equipment. Finally, a portion of it is returned to combustion chamber 10 for a semi-closed Brayton cycle.

[0076] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A semi-closed Brayton cycle power generation and oil displacement system, characterized in that, include: A combustion chamber for burning fuel and producing a circulating working fluid, which is a mixture including carbon dioxide and water vapor; The turbine is connected to the outlet of the combustion chamber, receives the circulating working fluid from the outlet of the combustion chamber, and performs work. A mechanical energy output device is connected to the output end of the turbine and generates energy by doing work on the turbine. A water separator receives the circulating working fluid from the outlet of the turbine, the circulating working fluid is separated into carbon dioxide, liquid water and / or water vapor by the water separator, and the carbon dioxide, liquid water and / or water vapor are discharged to the external oil field through the outlet of the water separator; A carbon dioxide compression device is connected to the water separator. The carbon dioxide compression device is used to compress the carbon dioxide that is not discharged to the oil field. The carbon dioxide compressed by the carbon dioxide compression device is returned to the combustion chamber for the semi-closed Brayton cycle. An air separator, connected to the inlet of the combustion chamber, separates oxygen from the air and supplies it to the combustion chamber; The regenerator is used to exchange heat between the circulating working fluid output from the turbine, the oxygen separated by the air separator, and the carbon dioxide returned to the combustion chamber. The oxygen and carbon dioxide then enter the combustion chamber. A multi-way valve having a first port, a second port, a third port, and a fourth port; The water separator includes: A first water separator separates water vapor and carbon dioxide from the circulating working fluid from the regenerator. The water vapor is discharged to the external oil field via the water outlet of the first water separator, and the carbon dioxide outlet of the first water separator is connected to the first port of the multi-way valve. The second water separator cools the circulating working fluid from the regenerator and separates liquid water and carbon dioxide. The carbon dioxide outlet of the second water separator is connected to the second port of the multi-way valve. The third and fourth ports of the multi-way valve are respectively connected to the carbon dioxide compression device and the oil field; A gas splitter is provided in the pipe section from the carbon dioxide compression device to the combustion chamber, and is connected to the outlet of the carbon dioxide compression device. The gas splitter diverts a portion of the carbon dioxide compressed by the carbon dioxide compression device out of the semi-closed Brayton cycle to regulate the amount of carbon dioxide in the semi-closed Brayton cycle.

2. The semi-closed Brayton cycle power generation and oil displacement system according to claim 1, characterized in that, The working fluid produced by the combustion of fuel in the combustion chamber is a mixture of carbon dioxide and water vapor.

3. The semi-closed Brayton cycle power generation and oil displacement system according to claim 1, characterized in that, It also includes an oil displacement pretreatment device, the inlet of which is connected to a water separator and the outlet of which is connected to the oil field, for adjusting one or more of the pressure, temperature, and chemical content of carbon dioxide, liquid water and / or water vapor entering the oil field.

4. The semi-closed Brayton cycle power generation and oil displacement system according to claim 1, characterized in that, The multi-directional valve switches according to the reservoir conditions of the oilfield to control the carbon dioxide flow rate at the third and fourth ports.

5. A semi-closed Brayton cycle power generation and oil displacement method, characterized in that, The system applied to the semi-closed Brayton cycle power generation and oil displacement system as described in any one of claims 1-4 includes the following steps: The combustion step involves the combustion of fuel in a combustion chamber to produce a circulating working fluid, which is a mixture comprising carbon dioxide and water vapor. In the power-doping step, the turbine receives the circulating working fluid from the outlet of the combustion chamber and performs work; In the oil displacement step, the circulating working fluid is separated into carbon dioxide, liquid water and / or water vapor by a water separator, and the carbon dioxide, liquid water and / or water vapor are discharged to the external oil field through the outlet of the water separator to carry out carbon dioxide oil displacement and / or water displacement operations. In the compression cycle step, the carbon dioxide that is not discharged to the oil field is compressed by a carbon dioxide compression device to obtain compressed carbon dioxide, which is then returned to the combustion chamber to perform the semi-closed Brayton cycle.

6. The semi-closed Brayton cycle power generation and oil displacement method as described in claim 5, characterized in that, It also includes a reheating step, in which oxygen, compressed carbon dioxide and fuel exchange heat with the circulating working fluid in the reheater before entering the combustion chamber to participate in combustion.

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