Horizontal well carbon dioxide fracturing-heat extraction-utilization integrated method and horizontal well carbon dioxide fracturing-heat extraction-utilization integrated device

Abstract

The invention relates to the technical field of geothermal energy development and utilization, in particular to a horizontal well carbon dioxide fracturing-heat removal-utilization integrated method and device.The method comprises the steps that fracturing fluid in a supercritical state is injected into an injection well to fracture a geothermal reservoir to form cracks; injecting nanofluid formed by mixing fracturing fluid in a supercritical state and heat-conducting nanoparticles into the cracks of the geothermal reservoir through the injection well so as to absorb heat energy of the geothermal reservoir; and the nanofluid absorbing the heat energy of the geothermal reservoir is conveyed into a ground heat removal system through a production well, so that the heat energy generated by expansion of the nanofluid is collected. According to the embodiment of the invention, the geothermal reservoir is fractured by the fracturing fluid in the supercritical state, the permeability of the geothermal reservoir is improved, and geothermal resources can be ensured to flow and be extracted more efficiently. The heat-conducting nano-particles and the fracturing fluid in the supercritical state are combined to form the nano-fluid, so that the heat energy extraction efficiency is greatly improved, and efficient utilization of geothermal resources is achieved.

Description

Technical Field

[0001] The embodiments of the present invention relate to the technical field of geothermal energy development and utilization, and specifically to an integrated method and device for horizontal well carbon dioxide fracturing-heat extraction-utilization. Background Art

[0002] Hot dry rock is a clean energy with abundant resources and unique advantages, and has great potential for development and utilization. The buried depth is greater than 3km, the temperature is greater than or equal to 180℃, and it is a high-temperature dense rock mass with no or little water. Its advantages are stability and efficiency, it is not restricted by factors such as seasons / climate / day and night, and it is green and environmentally friendly. The development method of hot dry rock includes the following steps: First, high-pressure water is injected into the underground reservoir through drilling injection wells. The injection of high-pressure water forces the rock to fission and form a permeable multi-scale artificial fracture network structure. Next, the low-temperature heat extracting medium is injected into the hot dry rock reservoir with an artificial fracture network through the injection well, and after sufficient heat exchange with the high-temperature rock mass, it is extracted from the underground through the production well. Finally, the extracted heat energy is converted into electrical energy through the ground power generation system to realize the utilization and power generation of geothermal energy.

[0003] At present, the fracturing methods used in the geothermal development methods of hot dry rock horizontal wells mostly adopt high-intensity pumping, which is easy to cause local stress concentration, so that the hydraulic energy is released quickly in a short time, and only a single main fracture is generated, which is difficult to activate and communicate with natural fractures to form a three-dimensional fracture network. As a result, the heat exchange area in the reservoir is small, the communication capacity between wells is poor, and the injection fluid is seriously lost, resulting in small production flow, rapid production temperature drop, low heat extraction power, and short operating life. In addition, there are many shortcomings in the existing hot dry rock horizontal well geothermal development methods that select water as a heat extraction medium. During the fracturing process, due to the low viscosity of water, it is easy to flow through existing fractures during the fracturing process, and it is difficult to form new fractures or fully expand existing fractures. This limits the efficiency of fracturing and may not effectively cover a large area of ​​heat source rock formations. In addition, under high temperature conditions, water reacts chemically with rocks, which may lead to mineral precipitation, especially the formation of silicate sediments. This will cause the fractures to be blocked, thereby reducing the permeability of the entire geothermal reservoir, affecting the flow of subsequent circulating working fluids and heat energy extraction. In addition, water has a high specific heat capacity, which means that it needs to absorb more heat to increase its temperature, but at the same time, its density changes little and its heat exchange efficiency is limited. The chemical reaction between water and minerals in rocks under high temperature and high pressure conditions is also an important factor that restricts the thermal energy extraction efficiency of water, and may also cause equipment corrosion and crack blockage. At the same time, water is prone to phase change under high temperature and high pressure conditions, from liquid to gas. The volume change caused by the phase change makes the fluid control of the system complicated, which may lead to a decrease in circulation efficiency.

[0004] Therefore, how to overcome the problems in existing hot dry rock development methods, such as the inability to form a three-dimensional fracture network, easy chemical reactions, and poor permeability of geothermal reservoirs, and propose a hot dry rock horizontal well geothermal development method with high heat extraction efficiency and circulation efficiency is a key issue that needs to be solved urgently. Summary of the invention

[0005] The purpose of the embodiments of this specification is to provide an integrated method and device for horizontal well carbon dioxide fracturing-heat extraction-utilization, so as to overcome the problems existing in the hot dry rock horizontal well geothermal development method, such as the inability to form a three-dimensional fracture network, easy chemical reactions, and poor permeability of geothermal reservoirs, and to improve the heat extraction efficiency and circulation efficiency of hot dry rock horizontal well geothermal development.

[0006] On the one hand, an embodiment of the present specification provides an integrated method for horizontal well carbon dioxide fracturing-heat extraction-utilization, the method comprising: injecting a fracturing fluid in a supercritical state into an injection well to fracture a geothermal reservoir to form cracks; injecting a nanofluid formed by mixing the fracturing fluid in a supercritical state with heat-conductive nanoparticles into the cracks of the geothermal reservoir via the injection well to absorb the thermal energy of the geothermal reservoir; and transporting the nanofluid after absorbing the thermal energy of the geothermal reservoir to a ground heat extraction system via a production well to collect the thermal energy generated by the expansion of the nanofluid.

[0007] On the other hand, an embodiment of the present specification provides an integrated device for horizontal well carbon dioxide fracturing-heat extraction-utilization, which includes: a fracturing module, which is used to inject fracturing fluid in a supercritical state into an injection well to fracture a geothermal reservoir to form cracks; an absorption module, which is used to inject a nanofluid formed by mixing the fracturing fluid in a supercritical state with heat-conductive nanoparticles into the cracks of the geothermal reservoir via the injection well to absorb the thermal energy of the geothermal reservoir; and a collection module, which is used to transport the nanofluid after absorbing the thermal energy of the geothermal reservoir to a ground heat extraction system via a production well to collect the thermal energy generated by the expansion of the nanofluid.

[0008] On the other hand, a computer device is provided, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the above-mentioned horizontal well carbon dioxide fracturing-heat extraction-utilization integrated method.

[0009] It can be seen from the technical solutions provided by the above embodiments of this specification that the embodiments of this specification can inject the fracturing fluid in a supercritical state into the injection well to fractur e the geothermal reservoir to form cracks; the nanofluid formed by mixing the fracturing fluid in a supercritical state with the heat-conducting nanoparticles is injected into the cracks of the geothermal reservoir via the injection well to absorb the heat energy of the geothermal reservoir; the nanofluid after absorbing the heat energy of the geothermal reservoir is transported to the ground heat extraction system via the production well to collect the heat energy generated by the expansion of the nanofluid. Compared with the existing methods, the embodiments of this specification use the fracturing fluid in a supercritical state to fractur e the geothermal reservoir, which can improve the permeability of the geothermal reservoir and ensure that geothermal resources can flow and be extracted more efficiently. By combining the heat-conducting nanoparticles with the fracturing fluid in a supercritical state to form a nanofluid, the efficiency of heat extraction is greatly improved, which promotes the efficient use of geothermal resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In order to more clearly illustrate the technical solutions in the embodiments of this specification or the prior art, the drawings required for use in the embodiments or the prior art description are briefly introduced below.

[0011] Figure 1 This is a flow chart of a horizontal well carbon dioxide fracturing-heat extraction-utilization integrated method provided in an embodiment of this specification;

[0012] Figure 2 This is a structural diagram of a horizontal well carbon dioxide fracturing-heat extraction-utilization integrated method provided in an embodiment of this specification;

[0013] Figure 3 It is a schematic diagram of a diversion method based on a temporary plugging agent provided in an embodiment of this specification;

[0014] Figure 4 It is a schematic diagram of using sand plugs to perform staged fracturing of a geothermal reservoir provided in an embodiment of this specification;

[0015] Figure 5 This is a schematic diagram of the structural composition of a horizontal well carbon dioxide fracturing-heat extraction-utilization integrated device provided in an embodiment of this specification;

[0016] Figure 6 It is a schematic diagram of the structural composition of a computer device provided in an embodiment of this specification.

[0017] Reference numerals in the above drawings:

[0018] 1. Caprock; 2. Geothermal reservoir; 3. Heat medium; 4. Cement; 5. Development area; 6. Insulation casing; 7. Circulation pump; 8. Primary turbine; 9. High-pressure manifold; 10. Compressor; 11. Primary generator; 12. Primary heat exchanger; 13. Secondary generator; 14. Gas-liquid separator; 15. Secondary turbine; 16. Secondary heat exchanger; 17. Condenser; 18. Condensate; 19. Adsorption refrigeration unit; 20. Mixing pump; 21. Injection well; 22. Production well; 23. Fracture; 24. Temporary plugging agent; 25. Fractured geothermal reservoir section; 26. Sand plug; 27. Unfractured geothermal reservoir section; 28. Horizontal well fracturing string. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of this specification to clearly and completely describe the technical solutions in the embodiments of this specification. Obviously, the described embodiments are only part of the embodiments of this specification, not all of the embodiments. Based on the embodiments in this specification, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of this specification.

[0020] Figure 1 This is a flow chart of an integrated method for horizontal well carbon dioxide fracturing-heat extraction-utilization. In specific implementation, the method includes the following steps:

[0021] S101: Injecting a fracturing fluid in a supercritical state into an injection well to fracture the geothermal reservoir to form cracks.

[0022] The fracturing of the geothermal reservoir is achieved by injecting fracturing fluid in a supercritical state into an injection well to fracture the geothermal reservoir to form cracks.

[0023] Reference Figure 2 , the cap layer 1 is located above the geothermal reservoir 2. The geothermal reservoir refers to a stratum, rock mass or structural belt buried underground with effective voids and permeability, in which the geothermal fluid stored is available for development and utilization. These geothermal fluids can be steam or hot water, which store geothermal energy through convection and enrichment of heat-carrying fluids. The cap layer refers to a protective layer located above the geothermal reservoir that can isolate the geothermal reservoir and prevent the oil and gas therein from escaping upward. A development area 5 suitable for geothermal development can be selected in the geothermal reservoir 2. Specifically, the fluidity and exploitability of the geothermal fluid can be determined by evaluating the permeability, porosity and other parameters of the geothermal reservoir, and then a suitable geothermal reservoir area can be selected as the development area, which will not be repeated here.

[0024] In some embodiments, sCO may be 2The fracturing fluid in a supercritical state is injected into the injection well to fracture the geothermal reservoir in stages; the proppant concentration in the fracturing fluid in a supercritical state can be increased to a preset concentration threshold to form a sand plug; the sand plug is used to prevent the fracturing fluid in a supercritical state from flowing back into the fractured geothermal reservoir segment.

[0025] By using sCO 2 As a fracturing fluid, sCO is fully utilized 2 The low viscosity and high fluidity of the sand plug, as well as the properties of both gas and liquid in the supercritical state, greatly enhance the conductivity of the geothermal reservoir, improve the permeability of the geothermal reservoir, and ensure that geothermal resources can flow and be extracted more efficiently. By using sand plugs for staged fracturing, the fractured geothermal reservoir section can be effectively isolated from the unfractured geothermal reservoir section, preventing the backflow of fracturing fluid and interference between sections, and ensuring that the fracturing operation of each geothermal reservoir section is carried out independently. In addition, staged fracturing of geothermal reservoirs can fracture the geothermal reservoir more evenly and extensively, effectively avoiding the problem of insufficient fracturing of the geothermal reservoir. Finally, by using sand plugs, there is no need for complex mechanical isolation tools or repeated downhole operations, which can significantly reduce operation time and equipment usage and reduce overall operating costs.

[0026] Reference Figure 2 and Figure 3 , for the development area 5 between the injection well 21 and the production well 22, the development area 5 can be segmented in advance. The geothermal reservoir segmentation is to divide the development area of ​​the geothermal reservoir into multiple relatively independent layers according to the geological characteristics, heat storage performance and development requirements of the geothermal reservoir. By segmenting the geothermal reservoir, the characteristics of the geothermal reservoir can be better understood and controlled, and the efficiency of geothermal energy extraction can be improved. The geothermal reservoir segmentation method can be divided by stratum, by lithology, and by geotemperature. According to the stratum division, the development area of ​​the geothermal reservoir can be divided into different layers according to the sedimentary sequence and lithological characteristics of the stratum. According to the lithology division, the development area of ​​the geothermal reservoir can be divided into different layers according to the type and nature of the rock. Usually, the lithology of the thermal reservoir is mainly sandstone layer, with a sand-mud ratio greater than 0.5, which is a relative aquifer or thermal reservoir. The cap rock is mainly mudstone layer, with a sand-mud ratio less than 0.5, which is a relative impermeable layer or thermal insulation layer. According to the ground temperature, the development area of ​​the geothermal reservoir can be divided into different layers according to the ground temperature. For example, according to the instantaneous ground temperature data of the geothermal well, the thermal reservoir can be divided into a low-temperature single-layer structure thermal reservoir section and a medium-low temperature double-layer structure thermal reservoir section.

[0027] After the development area of ​​the geothermal reservoir is segmented, the geothermal reservoir segments of the development area 5 can be fractured one by one. The purpose of fracturing the geothermal reservoir segments of the development area 5 one by one is to improve the permeability of the geothermal reservoir so that the fracturing fluid can flow through the formation more effectively, thereby improving the release and recovery rate of thermal energy. 2With low viscosity and high fluidity, it can quickly penetrate into the tiny cracks in the geothermal reservoir under high pressure, causing the geothermal reservoir to rupture. 2 As a fracturing fluid. Figure 2 , Figure 3 and Figure 4 sCO can be continuously injected into the injection well 21 using the horizontal well fracturing string 28. 2 Among them, cement 4 can be used to reinforce the injection well 21 to ensure that the injected sCO 2 The injection well 21 includes a horizontal well section and a vertical well section, and a horizontal well fracturing string 28 is placed in the horizontal well section. The horizontal well fracturing string 28 can be injected through a high-pressure sCO 2 The geothermal reservoir section between the injection well 21 and the production well 22 is continuously compressed. 2 With the continuous injection of sCO, the pressure in the geothermal reservoir section continues to increase. When the pressure exceeds the fracture strength of the rock in the geothermal reservoir section, the rock breaks and cracks appear23. 2 The fluidity of sCO enables it to evenly distribute and extend cracks 23, forming a preliminary crack network. 2 It has the property of combining with gas and liquid, and can penetrate the development area 5 more effectively, causing the fracture 23 to extend.

[0028] After fracturing a geothermal reservoir section, the concentration of proppant in the fracturing fluid can be gradually increased to form a sand plug. The proppant is used to support the fractures formed after fracturing the geothermal reservoir section, preventing the fractures from closing, thereby maintaining the conductivity of the fractures. The function of the sand plug is to isolate the fractured section from the unfractured section and prevent the fracturing fluid from causing flow interference between the fractured section and the unfractured section. Figure 4 , ceramsite sand can be used as a proppant, and by gradually increasing the proportion of ceramsite sand to a preset concentration threshold, the ceramsite sand is aggregated between the fractured geothermal reservoir section 25 and the unfractured geothermal reservoir section 27 of the injection well 21 to form a dense sand plug 26. High concentration of ceramsite sand can block the connection between the injection well 21 wellbore and the development area 5, avoid the backflow of fracturing fluid during the subsequent fracturing process, and ensure that the unfractured geothermal reservoir section 27 is not disturbed. The sand plug 26 prevents the fracturing fluid in the fractured geothermal reservoir section 25 from flowing back to the injection well 21 wellbore through the isolation effect, ensuring the independent development of the next fracturing section. At the same time, the sand plug 26 can improve the efficiency of the fracturing operation, reduce the mutual influence between the fractured geothermal reservoir section 25 and the unfractured geothermal reservoir section 27, and promote the formation of a fracture network.

[0029] In some embodiments, a temporary plugging agent may be injected into the injection well to plug the fractured geothermal reservoir segment.

[0030] By using temporary plugging agents to form temporary barriers within the fractures of the fractured geothermal reservoir section, the fracture network is further expanded, and ultimately multiple fractures are formed, thereby improving the overall permeability of the geothermal reservoir.

[0031] Reference Figure 3 and Figure 4 After the sand plug 26 is formed, a temporary plugging agent 24 can be injected through the injection well 21 to plug the fractures of the fractured geothermal reservoir section 25. For example, a temporary plugging agent can be used that uses acrylamide (AM) as a main monomer and adds 2-acrylamide-2-methylpropanesulfonic acid (AMPS) and acrylic acid (AA) as functional monomers. AMPS contains—SO 3 -group, has strong salt resistance and can remain stable under high temperature and high salt conditions. The -COO- group in acrylic acid has the ability to absorb water and swell, which can enhance the sealing performance of the gel. After the temporary plugging agent 24 is injected through the injection well 21, the cracks in the fractured geothermal reservoir section 25 can be blocked, so that sCO 2 The fracturing fluid is diverted to the reservoir section that has not been fractured. After the sand plug 26 is formed, the injected temporary plugging agent 24 can block the cracks in the fractured geothermal reservoir section 25, thereby preventing the fracturing fluid from entering the cracks in the fractured geothermal reservoir section 25. This plugging is temporary. When the pressure of the fracturing fluid reaches a certain level, the temporary plugging agent will be pressed open, allowing the fracturing fluid to be diverted to the unfractured geothermal reservoir section 27, further expanding the fracture network of the development area 5.

[0032] For a geothermal reservoir segment, a fracturing fluid can be first used to fracture the geothermal reservoir segment to form a fracture, then the proppant concentration is increased to a preset concentration threshold to generate a sand plug, and finally a temporary plugging agent is injected to plug the geothermal reservoir segment. For each geothermal reservoir segment of the geothermal reservoir, the above steps are repeated to complete the fracturing of the entire geothermal reservoir and form a fracture network of the geothermal reservoir.

[0033] S102: Injecting a nanofluid formed by mixing a supercritical fracturing fluid with heat-conductive nanoparticles into the fractures of the geothermal reservoir through the injection well to absorb thermal energy of the geothermal reservoir.

[0034] The nanofluid formed by mixing the fracturing fluid in a supercritical state with the heat-conducting nanoparticles is injected into the cracks of the geothermal reservoir through the injection well, thereby achieving the acquisition of thermal energy in the geothermal reservoir.

[0035] In some embodiments, sCO may be 2 As a fracturing fluid in a supercritical state, CuO nanoparticles can be used as thermal conductive nanoparticles, and the sCO 2 Nanofluids are injected into injection wells to expand fractures in geothermal reservoirs; sCO formed by mixing supercritical fracturing fluid with thermally conductive nanoparticles2 The nanofluid is injected into the fractures of the expanded geothermal reservoir through the injection well to absorb the thermal energy of the geothermal reservoir.

[0036] By combining CuO nanoparticles with sCO 2 Combined with, significantly enhanced sCO 2 The thermal conductivity of the fluid makes the heat transfer more efficient. The Brownian motion of CuO nanoparticles strengthens the convective heat transfer mechanism, especially under high temperature and high pressure conditions, which greatly improves the efficiency of heat energy extraction and greatly promotes the efficient use of geothermal resources.

[0037] Compared with water-based fluids, sCO 2 With lower viscosity and higher penetration ability, it can quickly and evenly expand cracks and transfer heat. 2 Nanofluids, as circulating fluids and heat extractors, will not cause formation blockage or pore blockage and can operate stably for a long time. Figure 2 After completing the fracturing of the entire development area 5, sCO 2 Mixed with CuO nanoparticles to form sCO 2 Nanofluid is injected into the fractures of the development area 5 as heat extracting medium 3. 2 Nanofluids can effectively penetrate into the cracks and pores of the development area 5, thereby removing the sCO 2 The pressure and velocity carried by the nanofluid rapidly and uniformly expand the cracks in the development area 5. 2 Combination can effectively improve the heat extraction efficiency. CuO nanoparticles have extremely high thermal conductivity, which is much higher than that of basic fluids (such as water or CO 2 ) thermal conductivity. 2 Adding CuO nanoparticles to the fluid can significantly increase sCO 2 In addition, CuO nanoparticles in sCO 2 Brownian motion in the fluid can enhance the convective heat transfer mechanism, especially under high temperature and high pressure conditions. The addition of CuO nanoparticles can enhance the sCO 2 CuO nanoparticles show good chemical stability under high temperature and high pressure conditions and are not easily reacted with sCO 2 This stability allows CuO nanoparticles to be used in sCO 2 The thermal conductivity of the fluid is maintained for a long time without performance degradation or agglomeration.

[0038] S103: transporting the nanofluid after absorbing the thermal energy of the geothermal reservoir to a ground heat extraction system via a production well to collect the thermal energy generated by the expansion of the nanofluid.

[0039] The nanofluid that has absorbed the thermal energy of the geothermal reservoir is transported to a ground heat extraction system via a production well to collect the thermal energy generated by the expansion of the nanofluid, thereby realizing the utilization of the thermal energy in the geothermal reservoir.

[0040] In some embodiments, the ground heat extraction system includes a power generation system and a heating system; the sCO 2 The nanofluid is transported to the ground heat extraction system via the production well, including: 2 The nanofluid is transported to the power generation system via a production well; the sCO output by the power generation system is 2 Nanofluids are delivered to the heating system; supercritical CO 2 The fracturing fluid is injected into the injection well to fracture the geothermal reservoir to form fractures, including: cooling the CO output from the heating system 2 The fracturing fluid is compressed to a supercritical state; the CO 2 The fracturing fluid is injected into the injection well to fracture the geothermal reservoir to form fractures.

[0041] By using sCO 2 Nanofluids are used for power generation and heating and for converting sCO 2 Nanofluid recompression to generate sCO 2 , significantly reducing greenhouse gas emissions and providing CO 2 It lays the foundation for recycling.

[0042] Reference Figure 2 , sCO 2 After the nanofluid 3 is injected into the fractures of the development area 5, sCO 2 After the nanofluid 3 circulates in the development area 5 and absorbs a certain amount of heat, it can transfer sCO 2 The nanofluid is sent back to the surface. The production well 22 includes a horizontal well section and a vertical well section. 2 After circulating in the development area 5 and absorbing a certain amount of heat, the nanofluid 3 sequentially passes through the horizontal well section and the vertical well section of the production well 22 to reach the ground. 2 The temperature of nanofluids is usually over 200°C. 2 The nanofluid is first delivered to a power generation system to convert geothermal energy into electricity. 2 The nanofluid will be delivered to the heating system to convert sCO 2 The residual heat of the nanofluid is used for district heating. The heating system output is composed of sCO 2 Low-temperature CO separated by nanofluids 2 Fracturing fluid. The cooled CO2 The fracturing fluid is compressed to a supercritical state, and then the CO compressed to a supercritical state can be 2 The fracturing fluid is injected into the injection well to fracture the geothermal reservoir to form fractures.

[0043] In some embodiments, the power generation system includes a first expansion component and a second expansion component; the heating system includes a heat exchange component. 2 The nanofluid is transported to the power generation system via a production well, including: 2 The nanofluid is delivered to the first expansion component to collect the sCO 2 The nanofluid is expanded to generate heat energy; the nanofluid output from the first expansion component is transported to the second expansion component to mix the sCO 2 Nanofluid and water; based on the latent heat of phase change of water, the sCO is collected again 2 The heat energy generated by the expansion of the nanofluid. 2 The nanofluid is delivered to the heating system, including: the sCO output by the second expansion component 2 Nanofluids are delivered to the heating system to convert the sCO 2 The residual heat energy of the nanofluid is used for district heating.

[0044] By collecting sCO 2 The heat energy generated by the primary and secondary expansion of the nanofluid and the sCO 2 The residual heat energy of nanofluids can be used for district heating, which can make full use of geothermal energy and greatly improve the overall utilization rate of geothermal energy.

[0045] The first expansion component at least includes a circulation pump 7, a first-stage turbine 8, a high-pressure manifold 9, a compressor 10, and a first-stage generator 11. Figure 2 , sCO 2 After the nanofluid 3 is injected into the fractures of the development area 5, sCO 2 After the nanofluid 3 circulates in the development area 5 and absorbs a certain amount of heat, it can transfer sCO 2 The nanofluid is sent back to the surface. The pipe string of the production well 22 is wrapped with a thermal insulation sleeve 6, which can effectively reduce sCO 2 The heat loss of nanofluids during their return to the ground through the production wells improves the efficiency of thermal energy utilization and helps extend the life of the wellbore. 2 The temperature of nanofluids is usually over 200°C. 2 The nanofluid first passes through the circulation pump 7 and enters the compressor 10 for preheating and pressurization, and then enters the first-stage turbine 8 through the high-pressure manifold 9. During the expansion process, sCO 2The pressure of the nanofluid drops rapidly, driving the turbine blades of the first-stage turbine 8 to rotate, driving the first-stage generator 11 to convert mechanical energy into electrical energy. 2 The temperature and pressure of the nanofluid drop significantly, but a large amount of waste heat is still retained. 2 Then it enters the waste heat recovery system for further utilization.

[0046] The second expansion component includes at least a primary heat exchanger 12, a secondary generator 13, a gas-liquid separator 14 and a secondary turbine 15. Figure 2 , in sCO 2 After the nanofluid expands once to generate electricity, the primary heat exchanger 12 can be used to convert sCO 2 The waste heat of the nanofluid is transferred to water, and the sCO2 is received in the gas-liquid separator 14. 2 The waste heat of the nanofluid is converted into high-temperature and high-pressure steam. The steam can be mixed with sCO 2 The nanofluid is fed into the secondary turbine 15, and the latent heat of phase change of water vapor and sCO 2 The heat of the nanofluid is used for secondary expansion to generate electricity. Water vapor releases or absorbs a large amount of heat during phase change (such as from liquid to gas), which is called latent heat of phase change. 2 The nanofluid is input into the secondary turbine 15 together, and the heat of both can be fully utilized to drive the turbine blades of the secondary turbine 15 to rotate, driving the secondary generator 13 to convert mechanical energy into electrical energy. The latent heat released by water vapor during the phase change process and sCO 2 The remaining heat of the nanofluid acts together on the secondary generator 13 , thereby increasing the output power of the secondary turbine 15 .

[0047] The heat exchange component includes at least a secondary heat exchanger 16. Figure 2 , in sCO 2 After the nanofluid is expanded to generate electricity, the sCO 2 The waste heat of the nanofluid is transferred to the district heating system, using sCO 2 The waste heat of the nanofluid at 50°C to 100°C provides thermal energy for regional users. The secondary heat exchanger 16 can convert sCO 2 The waste heat in the nanofluid is effectively transferred to the circulating water or steam of the district heating system, thereby increasing the temperature of the district heating system. The secondary heat exchanger is usually characterized by high efficiency, corrosion resistance, and high temperature resistance, which can ensure the stability and reliability of the waste heat transfer process. 2 Using waste heat from nanofluids for heating can significantly reduce energy consumption and carbon emissions and improve energy efficiency. 2 Nanofluid waste heat heating can reduce heating costs and improve economic benefits.

[0048] In some embodiments, the ground heat extraction system further comprises a separation system; the step of compressing the cooled fracturing fluid outputted by the heating system to a supercritical state comprises: 2 Nanofluid is delivered to the separation system to output the cooled CO 2 Fracturing fluid; compressing the cooled CO 2 The fracturing fluid reaches a supercritical state.

[0049] By converting the expanded sCO 2 Nanofluid recompression to generate sCO 2 , significantly reducing greenhouse gas emissions and providing CO 2 It lays the foundation for recycling.

[0050] In the sCO 2 The waste heat of the nanofluid is transferred to the district heating system, which can 2 The nanofluid is input into the separation system. The separation system can be used to separate the low-temperature CO 2 , CuO nanoparticles and water mixed therein. The condensed water 18 separated in the separation system can be transported back to the gas-liquid separator 14, and the low-temperature CO separated in the separation system can be transported back to the gas-liquid separator 14. 2 Compressed to supercritical state to generate sCO 2 .

[0051] In some embodiments, the separation system includes a condensing component and a refrigeration component. 2 Nanofluid is delivered to the separation system to output the cooled CO 2 Fracturing fluid; compressing the cooled CO 2 Fracturing fluid to supercritical state, including: sCO output from the heating system 2 The nanofluid is transported to the condensation component to condense and separate CO 2 Fracturing fluid, CuO heat-taking nanoparticles and water; CO output from the condensation component 2 The fracturing fluid is transported to the refrigeration unit to cool the CO 2 The fracturing fluid and the cooled CO 2 The fracturing fluid is compressed to a supercritical state. 2 After the fracturing fluid is compressed to a supercritical state, the following steps are also included: 2 sCO formed by mixing fracturing fluid with CuO heat-sucking nanoparticles 2 The nanofluid is injected into the fractures of the geothermal reservoir through the injection well to absorb the thermal energy of the geothermal reservoir.

[0052] By using a separation system to separate the low temperature CO2 The fracturing fluid compresses the low temperature to a supercritical state, which can then 2 sCO formed by mixing fracturing fluid with CuO nanoparticles 2 Nanofluids injected into fractures in geothermal reservoirs achieve CO 2 The recycling of waste materials has greatly reduced greenhouse gas emissions and effectively improved resource utilization efficiency.

[0053] The separation system comprises at least a condensing component and a refrigeration component. The condensing component comprises at least a condenser 17. The refrigeration component comprises at least an adsorption refrigeration device 19. Figure 2 , in the sCO 2 The waste heat of the nanofluid is transferred to the district heating system, which can 2 The nanofluid is input to the condenser 17. The condenser 17 can be used to separate the low-temperature CO 2 , CuO nanoparticles and water mixed therein. The condensed water 18 separated in the condenser 17 can be transported back to the gas-liquid separator 14, and the low-temperature CO separated in the condenser 17 can be 2 The product is transported to the adsorption refrigeration device 19. The low-temperature CO 2 , CuO nanoparticles and water, sCO 2 The mixed gas of nanofluid and water vapor is input into the condenser 17, where the water vapor can be condensed into liquid water by lowering the temperature, and the CuO nanoparticles are no longer soluble in the low-temperature CO. 2 , thus achieving the separation of the three. After secondary expansion for power generation, district heating and condensation, CO 2 The temperature is close to the ambient temperature. The CO obtained by condensation separation can be condensed by adsorption refrigeration device 19 2 Compressed to a supercritical state to generate sCO 2 sCO can then be remixed using a mixing pump 20 2 and CuO nanoparticles to generate sCO 2 The nanofluid is transported back to the fractures in the development area 5 as a heat extracting medium 3, and absorbs the heat energy of the geothermal reservoir again and starts recycling again.

[0054] The method comprises injecting a fracturing fluid in a supercritical state into an injection well to fracture a geothermal reservoir to form cracks; injecting a nanofluid formed by mixing the fracturing fluid in a supercritical state with heat-conductive nanoparticles into the cracks of the geothermal reservoir via the injection well to absorb the thermal energy of the geothermal reservoir; and transporting the nanofluid after absorbing the thermal energy of the geothermal reservoir to a ground heat extraction system via a production well to collect the thermal energy generated by the expansion of the nanofluid, thereby realizing the integration of geothermal reservoir fracturing, heat extraction and utilization.

[0055] Based on the above-mentioned horizontal well carbon dioxide fracturing-heat extraction-utilization integrated method, this specification also proposes an embodiment of a horizontal well carbon dioxide fracturing-heat extraction-utilization integrated device. Figure 5 As shown, the horizontal well carbon dioxide fracturing-heat extraction-utilization integrated device may specifically include the following modules:

[0056] The fracturing module 501 can be used to inject fracturing fluid in a supercritical state into an injection well to fracture the geothermal reservoir to form cracks;

[0057] The absorption module 502 may be used to inject the nanofluid formed by mixing the fracturing fluid in a supercritical state with the heat-conducting nanoparticles into the fractures of the geothermal reservoir through the injection well to absorb the heat energy of the geothermal reservoir;

[0058] The collection module 503 can be used to transport the nanofluid after absorbing the thermal energy of the geothermal reservoir to the ground heat extraction system via the production well to collect the thermal energy generated by the expansion of the nanofluid.

[0059] In some embodiments, the fracturing module 501 can be used to inject fracturing fluid in a supercritical state into an injection well to fractur the geothermal reservoir in stages; increase the proppant concentration in the fracturing fluid in a supercritical state to a preset concentration threshold to form a sand plug; the sand plug is used to prevent the fracturing fluid in a supercritical state from flowing back into the fractured geothermal reservoir segment. In some embodiments, the fracturing module 501 can also be used to inject a temporary plugging agent into the injection well to plug the fractured geothermal reservoir segment.

[0060] In some embodiments, the absorption module 502 can be specifically used to inject a nanofluid formed by mixing a supercritical fracturing fluid with thermally conductive nanoparticles into an injection well to expand the cracks in the geothermal reservoir; and inject a nanofluid formed by mixing a supercritical fracturing fluid with thermally conductive nanoparticles into the cracks in the expanded geothermal reservoir via the injection well to absorb the thermal energy of the geothermal reservoir.

[0061] In some embodiments, the collection module 503 can be used to transport the nanofluid after absorbing the heat energy of the geothermal reservoir to the power generation system via the production well; transport the nanofluid output by the power generation system to the heating system; inject the fracturing fluid in the supercritical state into the injection well to fracture the geothermal reservoir to form cracks, including: compressing the cooled fracturing fluid output by the heating system to the supercritical state; injecting the fracturing fluid compressed to the supercritical state into the injection well to fracture the geothermal reservoir to form cracks. In some embodiments, the collection module 503 can also be used to transport the nanofluid to the first expansion component to collect the heat energy generated by the expansion of the nanofluid; transport the nanofluid output by the first expansion component to the second expansion component to mix the nanofluid and water; based on the latent heat of phase change of water, collect the heat energy generated by the expansion of the nanofluid again; transport the nanofluid output by the second expansion component to the heat exchange component to use the remaining heat energy of the nanofluid for regional heating. In some embodiments, the collection module 503 can also be used to transport the nanofluid output from the heating system to the separation system to output the cooled fracturing fluid; compress the cooled fracturing fluid to a supercritical state. The collection module 503 can also be used to transport the nanofluid output from the heating system to the condensation component to condense and separate the fracturing fluid, heat-extracting nanoparticles and water; transport the fracturing fluid output from the condensation component to the refrigeration component to cool the fracturing fluid and compress the cooled fracturing fluid to a supercritical state; inject the nanofluid formed by mixing the fracturing fluid in the supercritical state with the heat-extracting nanoparticles into the cracks of the geothermal reservoir through the injection well to absorb the thermal energy of the geothermal reservoir.

[0062] It should be noted that the units, devices or modules described in the above embodiments can be implemented by computer chips or entities, or by products with certain functions. For the convenience of description, the above devices are described separately by functions divided into various modules. Of course, when implementing this specification, the functions of each module can be implemented in the same or more software and / or hardware, or the modules that implement the same function can be implemented by a combination of multiple sub-modules or sub-units. The device embodiments described above are only schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0063] As can be seen from the above, the integrated device for horizontal well carbon dioxide fracturing-heat extraction-utilization provided in the embodiments of this specification can fractur geothermal reservoirs with fracturing fluid in a supercritical state, which can improve the permeability of geothermal reservoirs and ensure that geothermal resources can flow and be extracted more efficiently. By combining heat-conducting nanoparticles with fracturing fluid in a supercritical state to form a nanofluid, the efficiency of heat extraction is greatly improved, which promotes the efficient utilization of geothermal resources.

[0064] The embodiments of the present specification also provide a computer device for an integrated method of horizontal well carbon dioxide fracturing-heat extraction-utilization, including a processor and a memory for storing instructions executable by the processor. The processor can perform the following steps according to the instructions when implemented: injecting a fracturing fluid in a supercritical state into an injection well to fracture a geothermal reservoir to form cracks; injecting a nanofluid formed by mixing the fracturing fluid in a supercritical state with heat-conductive nanoparticles into the cracks of the geothermal reservoir through the injection well to absorb the thermal energy of the geothermal reservoir; and transporting the nanofluid after absorbing the thermal energy of the geothermal reservoir to a ground heat extraction system through a production well to collect the thermal energy generated by the expansion of the nanofluid.

[0065] In order to complete the above instructions more accurately, refer to Figure 6 As shown, the embodiment of this specification also provides another specific electronic device, wherein the electronic device includes a network communication port 601, a processor 602 and a memory 603, and the above structures are connected through internal cables so that each structure can perform specific data interaction.

[0066] The processor 602 can be specifically used to inject fracturing fluid in a supercritical state into an injection well to fracture a geothermal reservoir to form cracks; inject a nanofluid formed by mixing the fracturing fluid in a supercritical state with heat-conductive nanoparticles into the cracks of the geothermal reservoir via the injection well to absorb the thermal energy of the geothermal reservoir; and transport the nanofluid after absorbing the thermal energy of the geothermal reservoir to a ground heat extraction system via a production well to collect the thermal energy generated by the expansion of the nanofluid.

[0067] The memory 603 may be specifically used to store corresponding instruction programs.

[0068] In this embodiment, the network communication port 601 can be a virtual port that is bound to different communication protocols so that different data can be sent or received. For example, the network communication port can be a port responsible for web data communication, a port responsible for FTP data communication, or a port responsible for email data communication. In addition, the network communication port can also be a physical communication interface or communication chip. For example, it can be a wireless mobile network communication chip, such as GSM, CDMA, etc.; it can also be a Wifi chip; it can also be a Bluetooth chip.

[0069] In this embodiment, the processor 602 may be implemented in any appropriate manner. For example, the processor may take the form of a microprocessor or processor and a computer-readable medium storing a computer-readable program code (such as software or firmware) executable by the (micro)processor, a logic gate, a switch, an application specific integrated circuit (ASIC), a programmable logic controller, and an embedded microcontroller, etc. This specification does not limit this.

[0070] In this embodiment, the memory 603 includes a volatile memory and a non-volatile memory. The memory 603 may include multiple levels. In a digital system, anything that can store binary data can be a memory; in an integrated circuit, a circuit with a storage function without a physical form is also called a memory, such as RAM, FIFO, etc.; in a system, a storage device with a physical form is also called a memory, such as a memory stick, TF card, etc.

[0071] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0072] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0073] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0074] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0075] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A horizontal well carbon dioxide fracturing-heat extraction-utilization integrated method, characterized in that: include: injecting carbon dioxide in a supercritical state into an injection well to fracture a geothermal reservoir through a horizontal well section of the injection well; Injecting a nanofluid formed by mixing carbon dioxide in a supercritical state with heat-conductive nanoparticles into the fractures of the geothermal reservoir through the horizontal well section of the injection well to absorb thermal energy of the geothermal reservoir; The nanofluid after absorbing the thermal energy of the geothermal reservoir is transported to the ground heat extraction system through the production well to collect the thermal energy generated by the expansion of the nanofluid.

2. The method according to claim 1, characterized in that The method of injecting carbon dioxide in a supercritical state into an injection well to fracture a geothermal reservoir through a horizontal well section of the injection well to form fractures comprises: Injecting a fracturing fluid in a supercritical state into an injection well, and fracturing the geothermal reservoir in stages through a horizontal well section of the injection well; The proppant concentration in the supercritical fracturing fluid is increased to a preset concentration threshold to form a sand plug; the sand plug is used to prevent the fracturing fluid in the supercritical state from flowing back into the fractured geothermal reservoir section.

3. The method according to claim 2, characterized in that The method further comprises: A temporary plugging agent is injected into the injection well to plug the fractured geothermal reservoir section.

4. The method according to claim 1, characterized in that The nanofluid formed by mixing carbon dioxide in a supercritical state with heat-conductive nanoparticles is injected into the fractures of the geothermal reservoir through the horizontal well section of the injection well to absorb the thermal energy of the geothermal reservoir, comprising: Injecting a nanofluid formed by mixing carbon dioxide in a supercritical state with heat-conducting nanoparticles into an injection well to expand fractures in a geothermal reservoir; A nanofluid formed by mixing carbon dioxide in a supercritical state with heat-conductive nanoparticles is injected into the fractures of the expanded geothermal reservoir through the horizontal well section of the injection well to absorb the thermal energy of the geothermal reservoir.

5. The method according to claim 1, characterized in that The ground heat extraction system includes a power generation system and a heating system; the nanofluid after absorbing the heat energy of the geothermal reservoir is transported to the ground heat extraction system via a production well, including: transporting the nanofluid after absorbing thermal energy from the geothermal reservoir to the power generation system via a production well; transporting the nanofluid output from the power generation system to the heating system; Injecting carbon dioxide in a supercritical state into an injection well to fracture a geothermal reservoir through a horizontal section of the injection well, including: Compressing the cooled carbon dioxide output from the heating system to a supercritical state; Carbon dioxide compressed to a supercritical state is injected into an injection well to fracture the geothermal reservoir through a horizontal section of the injection well.

6. The method according to claim 5, characterized in that The power generation system includes a first expansion component and a second expansion component; the heating system includes a heat exchange component; The method of transporting the nanofluid after absorbing the thermal energy of the geothermal reservoir to the power generation system via a production well comprises: delivering the nanofluid to the first expansion component to collect heat energy generated by the expansion of the nanofluid; delivering the nanofluid outputted from the first expansion component to the second expansion component to mix the nanofluid with water; Based on the latent heat of phase change of water, the heat energy generated by the expansion of the nanofluid is collected again; The method of delivering the nanofluid outputted by the power generation system to the heating system comprises: The nanofluid output from the second expansion component is transported to the heat exchange component, so that the residual heat energy of the nanofluid is used for regional heating.

7. The method according to claim 5, characterized in that The ground heat extraction system also includes a separation system; The method of compressing the cooled carbon dioxide outputted by the heating system to a supercritical state comprises: transporting the nanofluid output from the heating system to a separation system to output cooled carbon dioxide; The cooled carbon dioxide is compressed to a supercritical state.

8. The method according to claim 7, characterized in that The separation system includes a condensing component and a refrigeration component; The nanofluid output from the heating system is transported to the separation system to output cooled carbon dioxide; Compressing the cooled carbon dioxide to a supercritical state comprises: The nanofluid output from the heating system is transported to a condensation component to condense and separate carbon dioxide, heat-extracting nanoparticles and water; transporting the carbon dioxide outputted from the condensing part to the refrigeration part to cool the carbon dioxide and compress the cooled carbon dioxide to a supercritical state; After compressing the cooled carbon dioxide to a supercritical state, the method further comprises: The nanofluid formed by mixing carbon dioxide in a supercritical state with heat-extracting nanoparticles is injected into the cracks of the geothermal reservoir through the horizontal well section of the injection well to absorb the thermal energy of the geothermal reservoir.

9. A horizontal well carbon dioxide fracturing-heat extraction-utilization integrated device, characterized in that: The device comprises: A fracturing module, used for injecting carbon dioxide in a supercritical state into an injection well to fracture a geothermal reservoir to form fractures through a horizontal well section of the injection well; An absorption module, used for injecting a nanofluid formed by mixing carbon dioxide in a supercritical state with heat-conductive nanoparticles into the fractures of the geothermal reservoir through the horizontal well section of the injection well to absorb thermal energy of the geothermal reservoir; The collection module is used to transport the nanofluid after absorbing the thermal energy of the geothermal reservoir to the ground heat extraction system through the production well to collect the thermal energy generated by the expansion of the nanofluid.

10. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the method according to any one of claims 1 to 8 is implemented.

Images