Ocean natural gas hydrate comprehensive exploitation and power generation utilization system and method

Abstract

The application provides a kind of ocean natural gas hydrate comprehensive exploitation and power generation utilization system and method, belong to energy technical field, including gas power generation unit, gas unit and CO2 storage unit, gas unit includes fracturing preheating component, gas power generation unit includes natural gas compression cooling component, combustion turbine component, high temperature regenerator, low temperature regenerator, cooler, separator, evaporator and CO2 booster pump, CO2 booster pump outlet is connected with CO2 storage unit and low temperature regenerator cold side import, outlet is connected with high temperature regenerator cold side import, its outlet is connected with the inlet end of combustion turbine component;Cooler cold side import is connected with seawater, outlet is connected with low temperature regenerator cold side import, its outlet is connected with fracturing preheating component;Evaporator cold side is connected with refrigerant circulating component;High temperature regenerator cold side import is connected with oxygen, outlet is connected with combustion turbine component.The whole recycling process of the application has high exploitation efficiency, low energy consumption and no carbon emission.

Description

Technical Field

[0001] This application relates to the field of energy technology, and in particular to a system and method for the integrated exploitation and power generation of marine natural gas hydrates. Background Technology

[0002] Natural gas hydrates are ice-like crystalline substances formed by natural gas and water under high pressure and low temperature conditions. They are widely distributed in seafloor strata and permafrost strata of plateaus, with estimated reserves twice the total proven reserves of coal, oil, and natural gas, making them a highly promising unconventional natural gas resource. The development of natural gas hydrates mainly involves altering the phase equilibrium conditions of the hydrates to decompose and produce gas. The main methods include depressurization, thermal shock, inhibitor methods, displacement methods, and combinations of these methods. Among these, depressurization, which reduces the environmental pressure surrounding the hydrates to induce decomposition and gas production, is a common method for large-scale offshore natural gas extraction due to its relatively high extraction efficiency and ease of implementation. However, this method has certain limitations. Because the hydrate decomposition process involves an endothermic reaction, the reservoir temperature continuously decreases as depressurization extraction progresses, potentially leading to internal freezing and severely impacting extraction efficiency in the later stages of extraction. Thermal injection, which raises reservoir temperature to promote hydrate decomposition, can be used as an adjunct to depressurization extraction. Before or during depressurization extraction, heat is injected into the storage facility or the reservoir is heated to increase its temperature, effectively promoting hydrate decomposition and gas production, thus improving recovery rates. However, reservoir thermal injection or heating requires additional energy, increasing extraction costs. Furthermore, since offshore natural gas hydrate reservoirs are generally far from coastlines, extracted natural gas needs to be transported to land via long-distance pipelines or LNG carriers, further increasing overall extraction costs. In addition, the utilization of extracted natural gas generates carbon dioxide emissions.

[0003] Therefore, there is a need to invent a system and method for the extraction and comprehensive utilization of marine natural gas hydrates, to improve the extraction efficiency and recovery rate of natural gas hydrates, enhance comprehensive utilization efficiency, and reduce carbon emissions. The extracted natural gas can be directly utilized on offshore platforms, such as through gas-fired power generation, and then the electricity can be transmitted inland via cables, solving the problem of long-distance transportation of marine natural gas; the waste heat generated during power generation can be used to heat the hydrate reservoir, improving depressurization and gas extraction efficiency; and the carbon dioxide produced during power generation can be directly buried in the extracted reservoir, effectively solving the problem of carbon dioxide emissions.

[0004] Current hydrate extraction technologies mainly include: 1. Vertical well technology: a depressurization method for marine natural gas hydrate extraction and a subsea extraction system (CN201510455687.2), and an inclined well method for marine natural gas hydrate extraction (CN201710005368.0); 2. Horizontal well technology: a method for parallel horizontal well extraction of natural gas hydrates (CN201710983424.8), and a method for combined depressurization and heating extraction of marine hydrates using multi-branch horizontal wells (CN201811501628.4); 3. Thermal injection extraction technology: a method for extracting natural gas hydrates by injecting hot water into parallel horizontal wells (CN201710987944.6), and a method for developing heterogeneous natural gas hydrate reservoirs through segmented perforation in horizontal wells (CN20181072). 1969.6); 4. Direct power generation technology for offshore platforms for hydrate extraction: combustible ice power plant (CN200710024421.8), a method and apparatus for flue gas auxiliary heat replacement extraction of natural gas hydrate (CN201720151795.5), a low-carbon marine hydrate extraction and power generation system (CN202010485964.5); 5. CO2 storage technology after hydrate power generation: a process method combining depressurization extraction of natural gas hydrate and CO2 storage (CN201611113530.2); 2.6. Integration of horizontal wells, power generation, heat injection and CO2 injection: methane gas recovery method, low carbon dioxide emission power generation method, methane gas recovery system and low carbon dioxide emission power generation system (WO2018159594A1).

[0005] However, current hydrate extraction methods all have many drawbacks. 1. High gas production cost: Thermal injection, as an auxiliary method for depressurization extraction, can increase reservoir temperature, thereby improving decomposition rate, gas production rate, and recovery rate. However, existing thermal injection methods often directly heat the reservoir by consuming electricity or adding other auxiliary heat-generating devices (such as heat pumps), increasing gas production costs and making them unsuitable for large-scale natural gas hydrate extraction. 2. High transportation cost: Marine natural gas hydrate reservoirs are generally far from the coastline. Most extraction methods only focus on gas production itself. The produced gas is separated, purified, and then pressurized before being transported to land via pipelines laid on the seabed or liquefied and stored. This increases the overall gas production cost and also increases the risk of gas leakage. 3. Low comprehensive utilization efficiency: Some methods use offshore floating platforms to directly burn the produced hydrate gas to generate electricity, injecting the combustion product CO2 along with the cooling loop hot water into the reservoir to increase the reservoir temperature, or using the cooling loop hot water separately to heat the reservoir, and then injecting the separated CO2 back into abandoned wells. However, in addition to water and CO2, the combustion products of these recycling methods also include nitrogen oxides and sulfides. Furthermore, the system requires the installation of CO2 separation and capture devices, making it impossible to achieve efficient CO2 capture. Moreover, the overall system has low cycle thermal efficiency and poor economic performance. Summary of the Invention

[0006] In view of this, the embodiments of this application provide a system and method for the integrated exploitation and power generation of marine natural gas hydrates, which at least partially solves the problems of high gas extraction and transportation costs and poor economic efficiency of integrated utilization in the existing marine natural gas hydrate exploitation and utilization processes.

[0007] In a first aspect, embodiments of this application provide a comprehensive marine natural gas hydrate exploitation and power generation system. The system includes a gas-fired power generation unit, a gas production unit, and a CO2 storage unit. The gas production unit includes a fracturing preheating assembly. The gas-fired power generation unit is mounted on a floating platform at sea and includes a natural gas compression and cooling assembly, a combustion turbine assembly, a high-temperature regenerator, a low-temperature regenerator, a first cooler, a separator, an evaporator, and a CO2 booster pump. The inlet end of the natural gas compression and cooling assembly is connected to the gas production unit, and the outlet end of the natural gas compression and cooling assembly is connected to the inlet end of the combustion turbine assembly. The outlet end of the combustion turbine assembly is connected to the hot-side inlet of the high-temperature regenerator, the hot-side outlet of the high-temperature regenerator is connected to the hot-side inlet of the low-temperature regenerator, and the hot-side outlet of the low-temperature regenerator is connected to the hot-side inlet of the first cooler. The hot-side outlet of the cooler is connected to the inlet of the separator; the outlet of the separator is connected to the hot-side inlet of the evaporator; the hot-side outlet of the evaporator is connected to the inlet of the CO2 booster pump; the first branch of the CO2 booster pump outlet is connected to the CO2 storage unit; the second branch of the CO2 booster pump outlet is connected to the first cold-side inlet of the low-temperature regenerator; the first cold-side outlet of the low-temperature regenerator is connected to the first cold-side inlet of the high-temperature regenerator; the first cold-side outlet of the high-temperature regenerator is connected to the inlet of the combustion turbine assembly; seawater is introduced into the cold-side inlet of the first cooler; the cold-side outlet of the first cooler is connected to the second cold-side inlet of the low-temperature regenerator; the second cold-side outlet of the low-temperature regenerator is connected to the fracturing preheating assembly; a refrigerant circulation assembly is connected to the cold side of the evaporator; oxygen is introduced into the third cold-side inlet of the high-temperature regenerator; the third cold-side outlet of the high-temperature regenerator is connected to the inlet of the combustion turbine assembly.

[0008] According to a specific implementation of an embodiment of this application, the natural gas compression and cooling assembly includes a dryer filter, a first natural gas compressor, a second cooler, and a second natural gas compressor connected in sequence. The inlet of the dryer filter is connected to the gas extraction unit, and the outlet of the second natural gas compressor is connected to the inlet end of the combustion turbine assembly.

[0009] According to a specific implementation of an embodiment of this application, the combustion turbine assembly includes a high-pressure combustion chamber, a high-pressure turbine, a low-pressure combustion chamber, and a low-pressure turbine. The first inlet of the high-pressure combustion chamber is connected to the second natural gas compression outlet, the second inlet of the high-pressure combustion chamber is connected to the third outlet on the cold side of the high-temperature regenerator, the third inlet of the high-pressure combustion chamber is connected to the first outlet on the cold side of the high-temperature regenerator, the outlet of the high-pressure combustion chamber is connected to the inlet of the high-pressure turbine, the outlet of the high-pressure turbine is connected to the second inlet of the low-pressure combustion chamber, the first inlet of the low-pressure combustion chamber is connected to the outlet of the first natural gas compressor, the outlet of the low-pressure combustion chamber is connected to the inlet of the low-pressure turbine, and the outlet of the low-pressure turbine is connected to the hot side inlet of the high-temperature regenerator.

[0010] According to a specific implementation of an embodiment of this application, the refrigerant circulation assembly includes a refrigerant compressor, a condenser, and an expansion valve. The inlet of the refrigerant compressor is connected to the cold-side outlet of the evaporator, the outlet of the refrigerant compressor is connected to the hot-side inlet of the condenser, the hot-side outlet of the condenser is connected to the inlet of the expansion valve, and the outlet of the expansion valve is connected to the cold-side inlet of the evaporator. The cold side of the condenser is seawater.

[0011] According to a specific implementation of an embodiment of this application, the separator outlet is further connected to a recompressor, the recompressor outlet is connected to the second inlet on the cold side of the high-temperature regenerator, and the second outlet on the cold side of the high-temperature regenerator is connected to the high-pressure turbine.

[0012] According to a specific implementation of an embodiment of this application, the gas-fired power generation unit further includes an air separation device and an oxygen compressor. The air separation device is used to obtain oxygen from the air. The outlet of the air separation device is connected to the inlet of the oxygen compressor. The outlet of the oxygen compressor is connected to the third inlet on the cold side of the high-temperature regenerator. The third outlet on the cold side of the high-temperature regenerator is connected to the second inlet of the high-pressure combustion chamber.

[0013] According to a specific implementation of an embodiment of this application, the gas-fired power generation unit further includes a seawater filter and a high-pressure water pump. The inlet of the seawater filter is connected to a seawater supply pipeline, the outlet of the seawater filter is connected to the inlet of the high-pressure water pump, the outlet of the high-pressure water pump is connected to the cold-side inlet of the condenser, and the cold-side outlet of the condenser is connected to the cold-side inlet of the first cooler.

[0014] According to a specific implementation of an embodiment of this application, the gas production unit further includes a production well and a gas production pipeline network connected to the production well. The fracturing preheating component includes a preheating well and a hot water pipeline network connected to the preheating well. Both the preheating well and the production well are located within the hydrate reservoir. The pipeline of the preheating well is provided with perforations. The outlet end of the gas production pipeline network is connected to the inlet end of the natural gas compression and cooling component. A branch is provided between the cold-side outlet of the first cooler and the cold-side second inlet of the low-temperature regenerator. This branch and the cold-side second outlet of the low-temperature regenerator merge and are connected to the inlet end of the hot water pipeline network.

[0015] According to a specific implementation of an embodiment of this application, the CO2 storage unit includes an abandoned well and a CO2 delivery pipeline connected to the abandoned well. The abandoned well is located within a hydrate reservoir, and the inlet of the CO2 delivery pipeline is connected to the first branch of the outlet of the CO2 booster pump.

[0016] Secondly, embodiments of this application also provide a method for the integrated exploitation and power generation of marine natural gas hydrates, the method comprising:

[0017] The hydrate reservoir is fracturing and preheated by the fracturing preheating component. When the temperature of the hydrate reservoir is within the preset range of its decomposition temperature under pressure conditions, the gas production unit performs depressurization gas production.

[0018] The collected natural gas passes through a natural gas compression and cooling assembly and enters a combustion turbine assembly, where it is burned with oxygen to generate electricity, producing a combustion mixture.

[0019] Part of the generated electricity is used for equipment consumption in the gas-fired power generation unit, gas extraction unit, and CO2 storage unit, while the other part is transmitted to land.

[0020] The combustion mixture enters the hot side of the high-temperature regenerator, where it exchanges heat with CO2 and oxygen on the cold side of the high-temperature regenerator. Then it enters the hot side of the low-temperature regenerator, where it exchanges heat again with CO2 on the cold side of the low-temperature regenerator before entering the hot side of the first cooler, where it exchanges heat with seawater on the cold side of the first cooler to cool down.

[0021] After the seawater is heated by heat exchange, it enters the cold side of the low-temperature regenerator for further heating. The heated seawater then enters the fracturing preheating component.

[0022] After being cooled in the first cooler, the combustion mixture enters the separator, where the combustion products CO2 and water are separated. The water produced is discharged directly, while the gaseous CO2 produced enters the evaporator to be cooled into a liquid state.

[0023] Liquid CO2 enters the CO2 booster pump to increase the pressure and is then split into two branches for output. The high-pressure liquid CO2 output from the second branch of the CO2 booster pump enters the cold side of the low-temperature regenerator for heating, and then enters the cold side of the high-temperature regenerator for heating. The heated CO2 then enters the combustion turbine assembly.

[0024] When the gas production rate is less than the preset value, the gas production unit is converted into a CO2 storage unit. The high-pressure liquid CO2 from the first branch of the CO2 booster pump outlet enters the CO2 storage unit and stores the CO2 in the extracted reservoir.

[0025] Gas production units and CO2 storage units are repeatedly set up and moved within the hydrate reservoir, continuously opening new wells and sealing old ones.

[0026] Beneficial effects:

[0027] The integrated exploitation and power generation system and method for marine natural gas hydrates in this application embodiment has the following beneficial effects:

[0028] 1. Utilizing the waste heat from the gas-fired power generation unit to increase the reservoir temperature reduces heat injection costs, improves hydrate extraction efficiency, and reduces gas production costs;

[0029] 2. Through the integrated design of hydrate mining and power generation, the problems of gas storage and long-distance transportation during large-scale production have been solved, reducing transportation costs;

[0030] 3. During the comprehensive mining and power generation of hydrates, only CO2 and water are generated, with no other pollutants. The generated CO2 is buried in abandoned wells, and no carbon emissions are produced, thus achieving low-carbon operation.

[0031] 4. The cooling process in the power generation system uses seawater as a cold source, eliminating the need for additional refrigeration equipment, reducing equipment investment, and improving the economic efficiency of the integrated mining and power generation process.

[0032] 5. The direct combustion power generation cycle facilitates direct high-pressure carbon capture and carbon storage. Attached Figure Description

[0033] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is a schematic diagram of a marine natural gas hydrate integrated exploitation and power generation system according to an embodiment of the present invention;

[0035] Figure 2 This is a schematic diagram of the operation method of a marine natural gas hydrate integrated exploitation and power generation system according to an embodiment of the present invention.

[0036] In the diagram: A. Gas-fired power generation unit; B. Gas extraction unit; B1. Gas extraction pipeline network; B2. Production well; B3. Hot water pipeline network; B4. Preheating well; B41. Perforation; C. CO2 storage unit; C1. CO2 buried pipeline network; C2. Abandoned well; 1. Dryer filter; 2. First natural gas compressor; 3. Second cooler; 4. Second natural gas compressor; 5. High-pressure combustion chamber; 6. High-pressure turbine; 7. Low-pressure combustion chamber; 8. Low-pressure turbine; 9. High-temperature regenerator; 10. Low-temperature regenerator; 11. First cooler; 12. Separator; 13. Recompressor; 14. Air separator; 15. Oxygen compressor; 16. Evaporator; 17. CO2 booster pump; 18. Refrigerant compressor; 19. Condenser; 20. Expansion valve; 21. High-pressure water pump; 22. Seawater filter. Detailed Implementation

[0037] The embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0038] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. This application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0039] It should be noted that various aspects of embodiments within the scope of the appended claims are described below. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any particular structure and / or function described herein is merely illustrative. Based on this application, those skilled in the art will understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects set forth herein can be used to implement the device and / or practice the method. Additionally, this device and / or method can be implemented using structures and / or functionalities other than one or more of the aspects set forth herein.

[0040] It should also be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of this application. The illustrations only show the components related to this application and are not drawn according to the number, shape and size of the components in actual implementation. In actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0041] Furthermore, specific details are provided in the following description to facilitate a thorough understanding of the examples. However, those skilled in the art will understand that the described aspects can be practiced without these specific details.

[0042] To address the high extraction and transportation costs and poor economic efficiency of integrated utilization in existing marine natural gas hydrate exploitation and utilization processes, this application provides a system and method for integrated exploitation and power generation of marine natural gas hydrates. Specifically, the natural gas produced by depressurization and decomposition of the natural gas hydrate reservoir is directly transported to an offshore floating platform for oxygen-enriched combustion power generation, reducing energy transportation costs. The waste heat generated by power generation is used to heat seawater and transport it to the hydrate reservoir for preheating, further reducing the extraction cost of natural gas hydrates. The high-pressure, high-concentration CO2 generated by power generation is directly transported through pipelines to the already extracted reservoir for storage, solving the CO2 emission problem and achieving low-carbon emissions and economic efficiency in the power generation system.

[0043] Explanation of technical terms:

[0044] Hydrates (combustible ice): Hydrates refer to substances in a state where, under certain external conditions such as temperature and pressure, guest molecules are encased by water molecules through cage-like structures formed by hydrogen bonds and other bonding methods. Common guest molecules for hydrates in nature include methane, ethane, and carbon dioxide. Methane hydrates are widely distributed in deep-sea sediments or permafrost on land, and are ice-like crystalline substances formed by natural gas and water under high pressure and low temperature conditions. Because they look like ice and can be ignited, they are also called "combustible ice." They have high resource density, are widely distributed globally, and have extremely high resource value.

[0045] In a first aspect, embodiments of this application provide a system for the integrated exploitation and power generation of marine natural gas hydrates, as described below. Figure 1 and Figure 2A detailed description is provided. The system includes a gas-fired power generation unit A, a gas production unit B, and a CO2 storage unit C. Gas production unit B includes a fracturing preheating assembly. Gas-fired power generation unit A is located on an offshore floating platform and includes a natural gas compression and cooling assembly, a combustion turbine assembly, a high-temperature regenerator 9, a low-temperature regenerator 10, a first cooler 11, a separator 12, an evaporator 16, and a CO2 booster pump 17. The inlet of the natural gas compression and cooling assembly is connected to gas production unit B, and the outlet of the natural gas compression and cooling assembly is connected to the inlet of the combustion turbine assembly. The outlet of the combustion turbine assembly is connected to the hot-side inlet of the high-temperature regenerator 9, the hot-side outlet of the high-temperature regenerator 9 is connected to the hot-side inlet of the low-temperature regenerator 10, the hot-side outlet of the low-temperature regenerator 10 is connected to the hot-side inlet of the first cooler 11, and the hot-side outlet of the first cooler 11 is connected to the inlet of the separator 12. The outlet of unit 12 is connected to the hot-side inlet of evaporator 16. The hot-side outlet of evaporator 16 is connected to the inlet of CO2 booster pump 17. The first branch of the outlet of CO2 booster pump 17 is connected to CO2 storage unit C. The second branch of the outlet of CO2 booster pump 17 is connected to the first cold-side inlet of low-temperature regenerator 10. The first cold-side outlet of low-temperature regenerator 10 is connected to the first cold-side inlet of high-temperature regenerator 9. The first cold-side outlet of high-temperature regenerator 9 is connected to the inlet of combustion turbine assembly. Seawater is introduced into the cold-side inlet of first cooler 11. The cold-side outlet of first cooler 11 is connected to the second cold-side inlet of low-temperature regenerator 10. The second cold-side outlet of low-temperature regenerator 10 is connected to fracturing preheating assembly. A refrigerant circulation assembly is connected to the cold side of evaporator 16. Oxygen is introduced into the third cold-side inlet of high-temperature regenerator 9. The third cold-side outlet of high-temperature regenerator 9 is connected to the inlet of combustion turbine assembly.

[0046] In practice, the gas-fired power generation unit is placed on a floating platform near gas production unit B. It is used to burn the natural gas collected by gas production unit B to generate electricity. The resulting combustion mixture is separated by separator 12, producing water and gaseous CO2. The gaseous CO2 is cooled and pressurized to become liquid CO2, which is then stored in CO2 storage unit C. In this integrated hydrate extraction and power generation process, only CO2 and water are produced, with no other pollutants generated. Furthermore, the generated CO2 is stored in abandoned well C2, resulting in no carbon emissions. Seawater is used as a cold source. After heat exchange through the first cooler 11 and the low-temperature regenerator 10, the seawater is injected into the fracturing preheating assembly to raise the reservoir temperature. Therefore, the waste heat from the power generation unit is used to raise the reservoir temperature, eliminating the need for additional refrigeration equipment, reducing heat injection costs, improving hydrate extraction efficiency, and enhancing the economics of the integrated extraction and power generation process. The integrated hydrate extraction and power generation design solves the problems of difficult gas storage and long-distance transportation during large-scale production, reducing transportation costs. This embodiment adopts a direct combustion power generation cycle, which facilitates direct high-pressure carbon capture and carbon storage.

[0047] Furthermore, the natural gas compression and cooling assembly includes a dryer filter 1, a first natural gas compressor 2, a second cooler 3, and a second natural gas compressor 4 connected in sequence. The inlet of the dryer filter 1 is connected to the gas extraction unit B, and the outlet of the second natural gas compressor 4 is connected to the inlet end of the combustion turbine assembly.

[0048] In practice, the natural gas produced by gas extraction unit A passes through a dryer filter 1 and then enters the first natural gas compressor 2 for pressurization. A portion of the pressurized natural gas is then cooled by a second cooler 3 before entering the second natural gas compressor 4 for further pressure increase. The natural gas compression and cooling assembly is mainly used to dry, filter, pressurize, and cool the natural gas collected by extraction unit A. The processed natural gas then enters the combustion turbine assembly for combustion and power generation.

[0049] Furthermore, the combustion turbine assembly includes a high-pressure combustion chamber 5, a high-pressure turbine 6, a low-pressure combustion chamber 7, and a low-pressure turbine 8. The first inlet of the high-pressure combustion chamber 5 is connected to the second natural gas compression outlet, the second inlet of the high-pressure combustion chamber 5 is connected to the third outlet on the cold side of the high-temperature regenerator 9, the third inlet of the high-pressure combustion chamber 5 is connected to the first outlet on the cold side of the high-temperature regenerator 9, the outlet of the high-pressure combustion chamber 5 is connected to the inlet of the high-pressure turbine 6, the outlet of the high-pressure turbine 6 is connected to the second inlet of the low-pressure combustion chamber 7, the first inlet of the low-pressure combustion chamber 7 is connected to the outlet of the first natural gas compressor 2, the outlet of the low-pressure combustion chamber 7 is connected to the inlet of the low-pressure turbine 8, and the outlet of the low-pressure turbine 8 is connected to the hot-side inlet of the high-temperature regenerator 9.

[0050] In specific implementation, the outlet of the first natural gas compressor 2 includes two branches. Natural gas enters the first natural gas compressor 2 and is pressurized. Part of the pressurized natural gas enters the low-pressure combustion chamber 7 through the first branch, and the other part enters the second cooler 3 through the second branch. After cooling, it enters the second natural gas compressor 4 to further increase the pressure, and then enters the high-pressure combustion chamber 5. High-pressure O2 and high-pressure natural gas are burned in the high-pressure combustion chamber 5 and mix with CO2 input to the high-pressure combustion chamber 5 from the first outlet of the high-temperature regenerator 9 to form a high-temperature and high-pressure combustion mixture. The high-temperature and high-pressure combustion mixture expands and does work through the high-pressure turbine 6 and then enters the low-pressure combustion chamber 7, where it is burned again with the natural gas transported by the first branch of the outlet of the first natural gas compressor 2 to form a combustion mixture. The combustion mixture is input to the low-pressure turbine 8 for expansion and power generation. The exhaust gas from the outlet of the low-pressure turbine 8 enters the hot side of the high-temperature regenerator 9, where it exchanges heat with the high-pressure CO2 and high-pressure oxygen on the cold side of the high-temperature regenerator 9, and then enters the low-temperature regenerator 10 for cooling, where it exchanges heat again with the high-pressure CO2 on the cold side of the low-temperature regenerator 10. After heating, the CO2 enters the first cooler 11 for cooling, and then enters the separator 12. The combustion products CO2 and water are separated in the separator 12. The water in the separator 12 is directly discharged, while part of the gaseous CO2 enters the compressor 13 via the first branch for pressurization, and then enters the high-temperature regenerator 9 for heating. The heated CO2 is sent to the high-pressure turbine 6 for turbine blade cooling. The other part of the CO2 enters the evaporator 16 via the second branch for cooling into liquid state. The liquid CO2 enters the CO2 booster pump 17 for pressure increase. After entering the CO2 booster pump 17, the liquid CO2 is divided into two branches. The high-pressure liquid CO2 from the second branch of the CO2 booster pump 17 enters the cold side of the low-temperature regenerator 10 for heating, and then enters the cold side of the high-temperature regenerator 9 for heating. The heated CO2 then enters the high-pressure combustion chamber 5. This part of CO2 is used to provide the combustion environment. Since the high-pressure combustion chamber 5 produces high-temperature gas, the injection of CO2 can form more high-temperature and high-pressure gas. The high-pressure liquid CO2 from the first branch of the CO2 booster pump 17 enters the storage unit C.

[0051] In this embodiment, staged combustion was achieved under different pressures (two natural gas compressors were installed, as well as a high-pressure combustion chamber 5 and a low-pressure combustion chamber 7), and the average heat absorption temperature of the circulation system was increased by reheating (oxygen was heated by a high-temperature regenerator 9), thereby improving combustion efficiency and power generation efficiency.

[0052] Furthermore, the refrigerant circulation assembly includes a refrigerant compressor 18, a condenser 19, and an expansion valve 20. The inlet of the refrigerant compressor 18 is connected to the cold-side outlet of the evaporator 16, the outlet of the refrigerant compressor 18 is connected to the hot-side inlet of the condenser 19, the hot-side outlet of the condenser 19 is connected to the inlet of the expansion valve 20, and the outlet of the expansion valve 20 is connected to the cold-side inlet of the evaporator 16. The cold side of the condenser 19 is seawater.

[0053] In practice, when the gas-fired power generation unit A is running, the refrigerant enters the condenser 19 through the refrigerant compressor 18 and exchanges heat with the seawater on the cold side. After cooling, the refrigerant enters the evaporator 16 through the throttle valve 20 to exchange heat and cools the gaseous CO2 generated by the separator 12 into a liquid state. Then, the refrigerant, after being heated, enters the refrigerant compressor 18 again. The refrigerant can be selected as CO2.

[0054] Furthermore, the outlet of the separator 12 is also connected to a re-compressor 13, the outlet of the re-compressor 13 is connected to the second inlet on the cold side of the high-temperature regenerator 9, and the second outlet on the cold side of the high-temperature regenerator 9 is connected to the high-pressure turbine 6.

[0055] In this embodiment, one branch of the separator 12 outlet is connected to the evaporator 16, and the other branch is connected to the recompressor 13. The mixed combustion products are separated into water and gaseous CO2 in the separator 12. A portion of the gaseous CO2 is pressurized by the recompressor 13 and then heated by heat exchange in the high-temperature regenerator 9 to form high-temperature and high-pressure CO2. By transporting the CO2 that has passed through the high-temperature regenerator 9 to the high-pressure turbine 6, the turbine blades can be cooled. In actual operation, the turbine blade temperature can reach more than 1,000 degrees Celsius. Using the CO2 that has passed through the high-temperature regenerator 9 to cool the blades can avoid damage to the blades. At the same time, the heat generated by combustion is effectively utilized, and the stable and reliable operation of the system is achieved.

[0056] Furthermore, the gas-fired power generation unit A also includes an air separator 14 and an oxygen compressor 15. The air separator 14 is used to obtain oxygen from the air. The outlet of the air separator 14 is connected to the inlet of the oxygen compressor 15. The outlet of the oxygen compressor 15 is connected to the third inlet on the cold side of the high-temperature regenerator 9. The third outlet on the cold side of the high-temperature regenerator 9 is connected to the second inlet of the high-pressure combustion chamber 5.

[0057] In practice, when the gas-fired power generation unit A is running, the high-purity O2 generated by the air separation device 14 is compressed to a high-pressure state by the oxygen compressor 15, and then heated by the high-temperature regenerator 9 before entering the high-pressure combustion chamber 5 to burn with the high-pressure natural gas in the high-pressure combustion chamber 5.

[0058] Furthermore, the gas-fired power generation unit A also includes a seawater filter 22 and a high-pressure water pump 21. The inlet of the seawater filter 22 is connected to the seawater supply pipeline, the outlet of the seawater filter 22 is connected to the inlet of the high-pressure water pump 21, the outlet of the high-pressure water pump 21 is connected to the cold side inlet of the condenser 19, and the cold side outlet of the condenser 19 is connected to the cold side inlet of the first cooler 11.

[0059] Specifically, when the gas-fired power generation unit A is running, seawater enters the high-pressure water pump 21 after passing through the filter 22 to be pressurized. The pressurized seawater first enters the cold side of the condenser 19 to be heated, then enters the cold side of the first cooler 11 to be heated, and then enters the cold side of the low-temperature regenerator 10 to be further heated to 60-100℃. The heated high-temperature seawater finally enters the hot water pipe network B3 in the acquisition unit B.

[0060] Furthermore, the gas production unit B also includes a production well B2 and a gas production pipeline network B1 connected to the production well B2. The fracturing preheating assembly includes a preheating well B4 and a hot water pipeline network B3 connected to the preheating well B4. Both the preheating well B4 and the production well B2 are located within the hydrate reservoir and can be vertical or horizontal wells. A perforation B41 is provided on the pipeline of the preheating well B4. The outlet end of the gas production pipeline network B1 is connected to the inlet end of the natural gas compression and cooling assembly. A branch is provided between the cold side outlet of the first cooler 11 and the cold side second inlet of the low-temperature regenerator 10. This branch and the cold side second outlet of the low-temperature regenerator 10 merge and are connected to the inlet end of the hot water pipeline network B3.

[0061] In specific implementation, the gas extraction pipeline B1 of the gas extraction unit B is connected to the dryer filter 1 of the gas-fired power generation unit A to supply natural gas to the gas-fired power generation unit A. The hot water pipeline B3 of the gas extraction unit B is connected to the second cold-side outlet of the low-temperature regenerator 10 of the gas-fired power generation unit A to inject the heat-exchanged hot seawater into the preheating well B4. During extraction, the hydrate reservoir is fracturing using perforation B41 in preheating well B4, creating a large flow channel within the reservoir. High-temperature seawater produced by the low-temperature regenerator 10 in gas-fired power generation unit A is then injected into preheating well B4 via hot water pipeline B3. Simultaneously, the injection temperature is controlled by adjusting the seawater flow rate in the branch pipeline between the cold-side outlet of the first cooler 11 and the second cold-side outlet of the low-temperature regenerator 10. The injection temperature is maintained between 60-100℃ based on the actual reservoir conditions. During this process, the seawater temperature rises after passing through the low-temperature regenerator 10, and the seawater in the branch pipeline between the cold-side outlet of the first cooler 11 and the second cold-side outlet of the low-temperature regenerator 10 mixes with the seawater after passing through the low-temperature regenerator 10. Adjusting the flow rates of both mixtures regulates the temperature of the mixed fluid. When the reservoir temperature approaches or exceeds its decomposition temperature under pressure conditions, preheating well B4 becomes production well B2 for depressurization and gas production. The generated natural gas is collected through the gas production pipeline B1 in gas production unit B.

[0062] Furthermore, the CO2 storage unit C includes an abandoned well C2 and a CO2 buried pipeline C1 connected to the abandoned well C2. The abandoned well C2 is located in the hydrate reservoir and can be a vertical well or a horizontal well. The inlet of the CO2 buried pipeline C1 is connected to the first branch of the outlet of the CO2 booster pump 17.

[0063] In practical implementation, when the gas production rate is less than 1000m...3 / d, the production well B2 is converted into the abandoned well C2. The high-pressure CO2 from the first branch of the CO2 booster pump 17 of the gas power generation unit A enters the abandoned well C2 through the delivery pipeline C1 of the CO2 storage unit C, and stores the CO2 in the already extracted reservoir.

[0064] Secondly, embodiments of this application also provide a method for the integrated exploitation and power generation of marine natural gas hydrates, the method comprising:

[0065] The hydrate reservoir is fracturing and preheated by the fracturing preheating component. When the temperature of the hydrate reservoir is within the preset range of its decomposition temperature under pressure conditions, gas production unit A performs depressurization gas production.

[0066] The collected natural gas passes through a natural gas compression and cooling assembly and enters a combustion turbine assembly, where it is burned with oxygen to generate electricity, producing a combustion mixture.

[0067] Part of the generated electricity is used for equipment consumption in gas-fired power generation unit A, gas extraction unit B, and CO2 storage unit C, while the other part is transmitted to land.

[0068] The combustion mixture enters the hot side of the high-temperature regenerator 9, where it exchanges heat with CO2 and oxygen on the cold side of the high-temperature regenerator 9, and then enters the hot side of the low-temperature regenerator 10, where it exchanges heat again with CO2 on the cold side of the low-temperature regenerator 10, and then enters the hot side of the first cooler 11, where it exchanges heat with seawater on the cold side of the first cooler 11 to cool down.

[0069] After the seawater is heated by heat exchange, it enters the cold side of the low-temperature regenerator 10 for further heating. The heated seawater then enters the fracturing preheating component.

[0070] After being cooled in the first cooler 11, the combustion mixture enters the separator 12. The combustion products CO2 and water are separated in the separator 12. The water produced is discharged directly, and the gaseous CO2 produced enters the evaporator 16 to be cooled into liquid.

[0071] Liquid CO2 enters CO2 booster pump 17 to increase pressure and is split into two branches for output. The high-pressure liquid CO2 output from the second branch of CO2 booster pump 17 enters the cold side of low-temperature regenerator 10 for heating, and then enters the cold side of high-temperature regenerator 9 for heating. The heated CO2 then enters the combustion turbine assembly.

[0072] When the gas production rate is less than the preset value, the gas production unit A is converted into a CO2 storage unit. The high-pressure liquid CO2 from the first branch of the CO2 booster pump 17 enters the CO2 storage unit C and stores the CO2 in the extracted reservoir.

[0073] Gas production unit A and CO2 storage unit C are repeatedly set up and moved within the hydrate reservoir, continuously opening new wells and storing old wells.

[0074] In one embodiment, a specific example is provided to illustrate the integrated exploitation and power generation method for marine natural gas hydrates based on the Allam cycle, with reference to... Figure 1 and Figure 2 This includes the following steps:

[0075] (1) Using marine drilling technology, three or more wells are drilled in the natural gas hydrate reservoir. These wells can be horizontal or vertical, with a distance of more than 200m between them. The wells include one or more production wells B2, one or more preheating wells B4, and one or more abandoned wells C2. The preheating well B4 is equipped with a perforation B41, which can be used to fracture the hydrate reservoir and form a flow channel inside the reservoir. After fracturing, hot fluid is injected into the hydrate reservoir through the perforation B41 to increase the temperature inside the reservoir.

[0076] (2) Construct an offshore floating platform and arrange a gas-fired power generation unit A on it. The gas-fired power generation unit A includes a dryer filter 1, a first natural gas compressor 2, a second cooler 3, a second natural gas compressor 4, a high-pressure combustion chamber 5, a high-pressure turbine 6, a low-pressure combustion chamber 7, a low-pressure turbine 8, a high-temperature regenerator 9, a low-temperature regenerator 10, a first cooler 11, a separator 12, a re-compressor 13, an air separator 14, an oxygen compressor 15, an evaporator 16, a CO2 booster pump 17, a refrigerant compressor 18, a condenser 19, an expansion valve 20, a high-pressure water pump 21, and a seawater filter 22. The gas extraction pipeline B1 of the gas extraction unit B is connected to the dryer filter 1 of the gas-fired power generation unit A to provide natural gas to the power generation platform. The hot water pipeline B3 of the gas extraction unit B is connected to the second cold-side outlet of the low-temperature regenerator 10 of the gas-fired power generation unit A to inject the heat-exchanged hot seawater into the preheating well. The first branch of the CO2 booster pump 17 of the gas-fired power generation unit A is connected to the CO2 buried pipeline C1 of the CO2 storage unit C, for storing the CO2 generated by power generation in the abandoned well C2. Part of the electrical energy generated by the gas-fired power generation unit A is used for equipment consumption in the gas-fired power generation unit A, gas extraction unit B, and CO2 storage unit C; the remainder is directly transmitted to land via submarine cable.

[0077] (3) During extraction, the hydrate reservoir is fracturing using the perforation B41 in the preheating well B4, forming a large flow channel inside the hydrate reservoir. Then, the high-temperature seawater produced by the low-temperature regenerator 10 in the gas-fired power generation unit A is injected into the preheating well B4 through the hot water pipeline B3. At the same time, the injection temperature is controlled by adjusting the seawater flow rate in the pipeline connecting the outlet of the first cooler 11 and the second outlet of the low-temperature regenerator 10. The injection temperature is controlled between 60-100℃ according to the actual reservoir conditions. When the reservoir temperature is close to or higher than the decomposition temperature under its pressure conditions, the preheating well B4 is converted into a production well B2 for depressurization and gas production. The generated natural gas is collected through the gas production pipeline B1 in the gas production unit B. When the gas production rate is less than 1000m 3 / d, the production well B2 is converted into the abandoned well C2. The high-pressure CO2 from the first branch of the CO2 booster pump 17 of the gas power generation unit A enters the abandoned well C2 through the delivery pipeline C1 of the CO2 storage unit C, and stores the CO2 in the already extracted reservoir.

[0078] (4) When the gas-fired power generation platform A is running, the high-purity O2 produced by the air separator 14 is compressed to a high-pressure state by the oxygen compressor 15, and then heated by the high-temperature regenerator 9 before entering the high-pressure combustion chamber 5. The natural gas produced by the gas collection pipeline B1 is pressurized by the first natural gas compressor 2 after passing through the dryer filter 1. Part of the pressurized natural gas enters the low-pressure combustion chamber 7 through the first branch, and the other part is cooled by the second cooler 3 before entering the second natural gas compressor 4 to further increase the pressure, and then enters the high-pressure combustion chamber 5. The high-pressure O2 and high-pressure natural gas are burned in the high-pressure combustion chamber 5 and mixed with the CO2 input to the high-pressure combustion chamber 5 from the first outlet of the high-temperature regenerator 9 to form a high-temperature and high-pressure combustion mixture. The combustion mixture is expanded by the high-pressure turbine 6 to do work and then enters the low-pressure combustion chamber 7, where it is burned again with the natural gas transported by the first branch of the outlet of the first natural gas compressor 2 to form a combustion mixture. The combustion mixture is input to the low-pressure turbine 8 to expand and do work to generate electricity, and exhaust gas from the outlet of the low-pressure turbine 8. The CO2 enters the hot side of the high-temperature regenerator 9, exchanges heat with the high-pressure CO2 and high-pressure oxygen on the cold side, and then enters the low-temperature regenerator 10 for cooling. After exchanging heat again with the high-pressure CO2 on the cold side, it enters the first cooler 11 for further cooling, and then enters the separator 12. The combustion products CO2 and water are separated in the separator 12. The water in the separator 12 is directly discharged, while part of the gaseous CO2 enters the compressor 13 via the first branch for pressurization, and then enters the high-temperature regenerator 9 for heating. The heated CO2 is then sent to the high-pressure turbine 6 for turbine blade cooling. The other part of the CO2 enters the evaporator 16 via the second branch for cooling into liquid. The liquid CO2 enters the CO2 booster pump 17 to increase the pressure. After the booster pump 17, the liquid CO2 is divided into two branches. The high-pressure liquid CO2 in the second branch enters the cold side of the low-temperature regenerator 10 for heating, and then enters the cold side of the high-temperature regenerator 9 for heating. The heated CO2 then enters the high-pressure combustion chamber 5. The high-pressure liquid CO2 in the first branch enters the CO2 delivery pipeline C1 of the storage unit C.

[0079] When the gas-fired power generation platform A is running, the refrigerant enters the condenser 19 through the refrigerant compressor 18 and exchanges heat with the seawater on the cold side. After cooling, the refrigerant enters the evaporator 16 through the throttle valve 20 to exchange heat and cool the gaseous CO2 into liquid. Then, the refrigerant, after being heated, enters the refrigerant compressor 18 again. The refrigerant can be selected as CO2.

[0080] When the gas-fired power generation platform A is running, seawater enters the high-pressure water pump 21 after passing through the filter 22. The pressurized seawater first enters the cold side of the condenser 19 to be heated, then enters the cold side of the first cooler 11 to be heated, and then enters the cold side of the low-temperature regenerator 10 to be further heated to 60-100℃. The heated high-temperature seawater finally enters the hot water pipe network B3 in the acquisition unit B.

[0081] (5) During the integrated exploitation and power generation of hydrates, gas production unit B and CO2 storage unit C can be repeatedly set up and moved in the hydrate storage sea area, continuously opening new wells and sealing old wells, thereby realizing long-term large-scale gas production, power generation and CO2 storage process, and ultimately realizing efficient exploitation and power generation utilization of natural gas hydrate reservoir sea area.

[0082] In one embodiment, during the extraction process, a heat injection-gas production cycle operation can be performed on a single extraction well, which is beneficial to improving the recovery rate.

[0083] In one embodiment, the extraction well, preheating well, and storage well involved in the above embodiments can be multiple vertical wells or horizontal wells at the same time.

[0084] This application addresses the problems of high gas extraction and transportation costs and low comprehensive utilization efficiency in the exploitation and utilization of marine natural gas hydrates. It proposes a comprehensive exploitation and power generation system and method for marine natural gas hydrates. The extracted natural gas is directly used for oxygen-enriched combustion power generation. Waste heat from the power generation process is used to heat seawater, which is then injected into the hydrate reservoir to raise its temperature. Simultaneously, the high-pressure, high-concentration CO2 generated during power generation is sealed in the already exploited abandoned wells. The entire recycling process is highly efficient, energy-saving, and carbon-free. Specifically, the comprehensive exploitation and power generation system for marine natural gas hydrates of this application has the following characteristics:

[0085] 1. In the hydrate extraction process, fracturing is first performed through perforation, then the reservoir is preheated, and then depressurization extraction is carried out. During the preheating process, the waste heat of the gas power generation unit is used to increase the reservoir temperature. Specifically, seawater is used for heat exchange on the cold side of the first cooler 11, condenser 19 and low temperature regenerator 10 in the gas power generation system. After heat exchange, the temperature of the seawater rises and is then injected into the preheating well B4 to increase the reservoir temperature. This reduces the heat injection cost, improves the hydrate extraction efficiency, and reduces the gas production cost.

[0086] 2. Through the integrated design of hydrate mining and power generation, the problems of gas storage and long-distance transportation during large-scale production have been solved, reducing transportation costs;

[0087] 3. In the process of comprehensive mining and power generation of hydrates, the natural gas extracted from the mining well is directly transported to the power generation platform for combustion in an oxygen-enriched combustion power generation manner, which only produces CO2 and water, without the generation of other pollutants. Moreover, the generated CO2 is buried in the abandoned well, without producing carbon emissions, thus achieving low-carbon operation.

[0088] 4. The cooling process in the power generation system uses seawater as a cold source, eliminating the need for additional refrigeration equipment, reducing equipment investment, and improving the economic efficiency of the integrated mining and power generation process.

[0089] 5. The direct combustion power generation cycle facilitates direct high-pressure carbon capture and carbon storage;

[0090] 6. The gas-fired power generation system adopts multi-stage compression and combustion (reheat), which realizes staged combustion under different pressures and increases the average heat absorption temperature of the circulation system through reheating, effectively improving combustion efficiency and overall system performance.

[0091] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A system for the integrated exploitation and power generation of marine natural gas hydrates, characterized in that, The system includes a gas-fired power generation unit (A), a gas extraction unit (B), and a CO2 storage unit (C). The gas extraction unit (B) includes a fracturing preheating assembly. The gas-fired power generation unit (A) is located on a floating platform at sea. The gas-fired power generation unit (A) includes a natural gas compression and cooling assembly, a combustion turbine assembly, a high-temperature regenerator (9), a low-temperature regenerator (10), a first cooler (11), a separator (12), an evaporator (16), and a CO2 booster pump (17). The inlet end of the natural gas compression and cooling assembly is connected to the gas extraction unit (B), and the outlet end of the natural gas compression and cooling assembly is connected to the inlet end of the combustion turbine assembly. The outlet end of the combustion turbine assembly is connected to the hot-side inlet of the high-temperature regenerator (9). The hot-side outlet of the high-temperature regenerator (9) is connected to the hot-side inlet of the low-temperature regenerator (10). The hot-side outlet of the low-temperature regenerator (10) is connected to the hot-side inlet of the first cooler (11), and the hot-side outlet of the first cooler (11) is connected to the inlet of the separator (12). The outlet of separator (12) is connected to the hot-side inlet of evaporator (16), the hot-side outlet of evaporator (16) is connected to the inlet of CO2 booster pump (17), the first branch of the outlet of CO2 booster pump (17) is connected to CO2 storage unit (C), the second branch of the outlet of CO2 booster pump (17) is connected to the first cold-side inlet of low-temperature regenerator (10), the first cold-side outlet of low-temperature regenerator (10) is connected to the first cold-side inlet of high-temperature regenerator (9), and the cold-side outlet of high-temperature regenerator (9) is connected to the first cold-side inlet of high-temperature regenerator (9). The first outlet is connected to the inlet end of the combustion turbine assembly; seawater is introduced into the cold side inlet of the first cooler (11), the cold side outlet of the first cooler (11) is connected to the second cold side inlet of the low-temperature regenerator (10), the second cold side outlet of the low-temperature regenerator (10) is connected to the fracturing preheating assembly; a refrigerant circulation assembly is connected to the cold side of the evaporator (16); oxygen is introduced into the third cold side inlet of the high-temperature regenerator (9), the third cold side outlet of the high-temperature regenerator (9) is connected to the inlet end of the combustion turbine assembly.

2. The integrated marine natural gas hydrate exploitation and power generation system according to claim 1, characterized in that, The natural gas compression and cooling assembly includes a dryer filter (1), a first natural gas compressor (2), a second cooler (3), and a second natural gas compressor (4) connected in sequence. The inlet of the dryer filter (1) is connected to the gas extraction unit (B), and the outlet of the second natural gas compressor (4) is connected to the inlet of the combustion turbine assembly.

3. The integrated marine natural gas hydrate exploitation and power generation system according to claim 2, characterized in that, The combustion turbine assembly includes a high-pressure combustion chamber (5), a high-pressure turbine (6), a low-pressure combustion chamber (7), and a low-pressure turbine (8). The first inlet of the high-pressure combustion chamber (5) is connected to the second natural gas compression outlet. The second inlet of the high-pressure combustion chamber (5) is connected to the third outlet on the cold side of the high-temperature regenerator (9). The third inlet of the high-pressure combustion chamber (5) is connected to the first outlet on the cold side of the high-temperature regenerator (9). The outlet of the high-pressure combustion chamber (5) is connected to the inlet of the high-pressure turbine (6). The outlet of the high-pressure turbine (6) is connected to the second inlet of the low-pressure combustion chamber (7). The first inlet of the low-pressure combustion chamber (7) is connected to the outlet of the first natural gas compressor (2). The outlet of the low-pressure combustion chamber (7) is connected to the inlet of the low-pressure turbine (8). The outlet of the low-pressure turbine (8) is connected to the hot-side inlet of the high-temperature regenerator (9).

4. The integrated marine natural gas hydrate exploitation and power generation system according to claim 1, characterized in that, The refrigerant circulation assembly includes a refrigerant compressor (18), a condenser (19), and an expansion valve (20). The inlet of the refrigerant compressor (18) is connected to the cold-side outlet of the evaporator (16), the outlet of the refrigerant compressor (18) is connected to the hot-side inlet of the condenser (19), the hot-side outlet of the condenser (19) is connected to the inlet of the expansion valve (20), and the outlet of the expansion valve (20) is connected to the cold-side inlet of the evaporator (16). The cold side of the condenser (19) is seawater.

5. The integrated marine natural gas hydrate exploitation and power generation system according to claim 3, characterized in that, The outlet of the separator (12) is also connected to the recompressor (13), the outlet of the recompressor (13) is connected to the second inlet on the cold side of the high-temperature regenerator (9), and the second outlet on the cold side of the high-temperature regenerator (9) is connected to the high-pressure turbine (6).

6. The integrated marine natural gas hydrate exploitation and power generation system according to claim 3, characterized in that, The gas-fired power generation unit (A) also includes an air separator (14) and an oxygen compressor (15). The air separator (14) is used to obtain oxygen from the air. The outlet of the air separator (14) is connected to the inlet of the oxygen compressor (15). The outlet of the oxygen compressor (15) is connected to the third inlet on the cold side of the high-temperature regenerator (9). The third outlet on the cold side of the high-temperature regenerator (9) is connected to the second inlet of the high-pressure combustion chamber (5).

7. The integrated marine natural gas hydrate exploitation and power generation system according to claim 4, characterized in that, The gas-fired power generation unit (A) also includes a seawater filter (22) and a high-pressure water pump (21). The inlet of the seawater filter (22) is connected to the seawater supply pipeline, the outlet of the seawater filter (22) is connected to the inlet of the high-pressure water pump (21), the outlet of the high-pressure water pump (21) is connected to the cold-side inlet of the condenser (19), and the cold-side outlet of the condenser (19) is connected to the cold-side inlet of the first cooler (11).

8. The integrated marine natural gas hydrate exploitation and power generation system according to claim 1, characterized in that, The gas production unit (B) also includes a production well (B2) and a gas production pipeline network (B1) connected to the production well (B2). The fracturing preheating assembly includes a preheating well (B4) and a hot water pipeline network (B3) connected to the preheating well (B4). Both the preheating well (B4) and the production well (B2) are located within the hydrate reservoir. The preheating well (B4) has a perforation (B41) on its pipeline. The outlet end of the gas production pipeline network (B1) is connected to the inlet end of the natural gas compression and cooling assembly. A branch is provided between the cold side outlet of the first cooler (11) and the cold side second inlet of the low-temperature regenerator (10). This branch and the cold side second outlet of the low-temperature regenerator (10) merge and are connected to the inlet end of the hot water pipeline network (B3).

9. The integrated marine natural gas hydrate exploitation and power generation system according to claim 1, characterized in that, The CO2 storage unit (C) includes an abandoned well (C2) and a CO2 buried pipeline (C1) connected to the abandoned well (C2). The abandoned well (C2) is located in the hydrate reservoir. The inlet of the CO2 buried pipeline (C1) is connected to the first branch of the outlet of the CO2 booster pump (17).

10. A method for the integrated exploitation and power generation of marine natural gas hydrates, employing the integrated exploitation and power generation system for marine natural gas hydrates as described in any one of claims 1-9, characterized in that, The method includes: The hydrate reservoir is fracturing and preheated by the fracturing preheating component. When the temperature of the hydrate reservoir is within the preset range of the decomposition temperature under its pressure, the gas production unit (B) performs depressurization gas production. The collected natural gas passes through a natural gas compression and cooling assembly and enters a combustion turbine assembly, where it is burned with oxygen to generate electricity, producing a combustion mixture. The generated electricity is used partly for equipment consumption in the gas-fired power generation unit (A), gas extraction unit (B), and CO2 storage unit (C), and partly transmitted to land; The combustion mixture enters the hot side of the high-temperature regenerator (9), exchanges heat with CO2 and oxygen on the cold side of the high-temperature regenerator (9), then enters the hot side of the low-temperature regenerator (10), exchanges heat again with CO2 on the cold side of the low-temperature regenerator (10), and then enters the hot side of the first cooler (11), where it exchanges heat with seawater on the cold side of the first cooler (11) to cool down. After the seawater is heated by heat exchange, it enters the cold side of the low-temperature regenerator (10) for further heating. The heated seawater then enters the fracturing preheating component. After being cooled in the first cooler (11), the combustion mixture enters the separator (12). The combustion products CO2 and water are separated in the separator (12). The water produced is discharged directly, and the gaseous CO2 produced enters the evaporator (16) to be cooled into liquid. Liquid CO2 enters the CO2 booster pump (17) to increase the pressure and is divided into two branches for output. The high-pressure liquid CO2 output from the second branch of the CO2 booster pump (17) enters the low-temperature regenerator (10) for cold-side heating, and then enters the high-temperature regenerator (9) for cold-side heating. The heated CO2 then enters the combustion turbine assembly. When the gas production rate is less than the preset value, the gas production unit (B) is converted into a CO2 storage unit (C). The high-pressure liquid CO2 from the first branch of the CO2 booster pump (17) enters the CO2 storage unit (C) and stores the CO2 in the extracted reservoir. The gas production unit (B) and CO2 storage unit (C) are repeatedly set up and moved within the hydrate reservoir, continuously opening new wells and storing old wells.

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