An integrated device and working method for supercritical CO2 fracturing and in-situ conversion of oil shale.

Abstract

The application provides an oil shale supercritical CO2 fracturing and in-situ conversion integrated device and working method, and belongs to the technical field of oil shale mining. Through integration of a CO2 liquefaction storage system, a fracturing heating system, a formation simulation system and a data monitoring system, efficient cooperation of supercritical CO2 fracturing and in-situ conversion is realized. The device comprises: a CO2 liquefaction storage system, which converts CO2 into a supercritical state and mixes to form a composite fracturing fluid; an oil shale fracturing and heating system, which fractures a core under simulated formation confining pressure conditions and triggers an in-situ oil shale cracking reaction through medium frequency heating; an oil shale fracturing model, which simulates a downhole fracturing environment and guides crack propagation; and a data monitoring system, which collects temperature and pressure parameters in real time to optimize process control. The fracturing and conversion processes are innovatively coupled, supercritical CO2 is used as a fracturing medium, a heat transfer carrier and a reaction medium, energy utilization and CO2 recycling efficiency are significantly improved, and oil shale recovery is improved.

Description

Technical Field

[0001] This invention relates to an integrated device and working method for supercritical CO2 fracturing and in-situ conversion of oil shale, belonging to the field of oil shale mining technology. Background Technology

[0002] Oil shale, as an unconventional oil and gas resource, has abundant reserves in my country. Current oil shale extraction methods primarily rely on surface pyrolysis, but this method is only suitable for shallow oil shale formations. For deep oil shale development, underground in-situ conversion technology is gradually becoming a breakthrough direction and future trend. Underground in-situ conversion technology directly pyrolyzes oil shale underground to produce oil and gas. However, this method requires interconnected fractures in the formation to ensure the formation of oil and gas channels. Fracturing, as a conventional reservoir stimulation method, can improve the permeability of oil shale formations and enhance the connectivity between wells, thereby accelerating the heating rate of the oil shale formation and increasing the oil recovery rate. Supercritical CO2, due to its unique properties, can effectively penetrate low-permeability formations and generate complex fracture networks. By carrying catalysts into the fracture network, it expands the contact area between the catalyst and the oil shale, promoting the decomposition of organic matter and thus improving the hydrocarbon recovery rate after oil shale pyrolysis.

[0003] Existing supercritical CO2 fracturing and in-situ conversion processes can only achieve a single process. Chinese patent document CN106644871A mainly evaluates the impact of fracturing fluid on core permeability, focusing on core permeability evaluation and damage degree, without involving the pyrolysis process. Chinese patent document CN114737936A mainly studies the pyrolysis of shale oil. Although many experimental devices in this field have equipment such as gas cylinders, pipelines, valves, core clamps, heating devices, thermometers, pressure gauges, and reaction vessels, these devices are mainly designed for conventional pyrolysis experiments and cannot meet the process requirements of fracturing followed by pyrolysis of oil shale. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides an integrated device and method for supercritical CO2 fracturing and in-situ conversion of oil shale, which can perform supercritical CO2 fracturing on oil shale and conduct in-situ conversion pyrolysis experiments, providing pilot experiments for underground in-situ conversion experiments of oil shale.

[0005] The technical solution of the present invention is as follows:

[0006] An integrated device for supercritical CO2 fracturing and in-situ conversion of oil shale includes: a CO2 liquefaction and storage system, an oil shale fracturing and heating system, an oil shale fracturing model, a data monitoring system, and a product analysis system.

[0007] A CO2 liquefaction storage system includes a CO2 cylinder, a temperature control device, and a high-pressure stirring device. The temperature control device is mainly used to cool the CO2, converting gaseous CO2 into liquid CO2, so as to pressurize it and reach a supercritical state. The high-pressure stirring device is mainly used to stir the CO2 fluid, thickener, and catalyst to ensure uniform mixing, so that the CO2 fluid can carry the catalyst and be injected into the oil shale.

[0008] The oil shale fracturing and heating system includes a constant-speed and constant-pressure pump, a confining pressure loading device, and a medium-frequency heating device. The constant-speed and constant-pressure pump is mainly used for continuous CO2 injection and can be adjusted to either constant-speed or constant-pressure modes. The confining pressure loading device is mainly used to apply confining pressure to the core to better simulate formation conditions. The medium-frequency heating device is mainly used to heat the oil shale after fracturing to achieve in-situ transformation of the oil shale. The system is equipped with a temperature and pressure linkage switching valve group, including an automatic pressure relief valve, a thermal trigger valve, and a pressure control regulating valve, for automatically switching to pyrolysis after the fracturing stage. When the system detects that the fracturing pressure has dropped to a threshold, the control unit automatically starts the medium-frequency heating device and simultaneously injects CO2 to raise the internal pressure of the reactor to a specified range, realizing CO2 circulation and diversion during the pyrolysis stage.

[0009] The oil shale fracturing model includes the model body and a core holder. The core holder is equipped with a fracturing wellbore, with a protruding injection end for inserting the core and a flat outlet end. The injection end of the core holder is inserted into the core, and fluid enters the core through the fracturing wellbore under the action of a constant speed and constant pressure pump to fracture the core. The outlet end is flat and closely adheres to the core.

[0010] The data monitoring system includes a temperature detection module, a pressure detection module, and an acoustic emission detection module. The temperature detection module is used to detect the temperature of the main body of the in-situ conversion system model, the pressure detection module is used to detect the injection end pressure and confining pressure of the core holder, and the acoustic emission detection module is placed on the inner wall of the main body of the model to capture the formation signal of the hydraulic fracturing induced fracture.

[0011] The product analysis system mainly includes a product collection module and an analysis module. The product collection module collects pyrolysis products via an autosampler, and the analysis module is a mass spectrometer detector that can perform molecular weight and structural analysis on the pyrolysis products.

[0012] Preferably, the temperature control device is a high-low temperature constant temperature bath, which can be used to control the temperature of CO2 through coils to achieve the phase transformation of CO2; the high-low temperature constant temperature bath is located between the CO2 cylinder and the constant speed and constant pressure pump, and is connected to a high pressure stirring device to keep the temperature in the entire system pipeline constant and the CO2 in the same phase.

[0013] Preferably, the high-pressure stirring device uses a magnetic stirrer for stirring, which is used to mix supercritical CO2, thickener, and catalyst; the high-pressure stirring device is located between the constant speed and constant pressure pump and the oil shale fracturing model, and is used to mix supercritical CO2 and thickener and then deliver it to the oil shale fracturing model for oil shale fracturing.

[0014] Preferably, the oil shale fracturing and heating system also includes a pressure tracking controller, and a constant speed and constant pressure pump with constant speed and constant pressure functions, adjustable to both constant flow and constant pressure fracturing modes; the constant speed and constant pressure pump is located between the temperature control device (high and low temperature constant temperature bath) and the pressure tracking controller, used for stable injection of CO2 fluid, and has pressure protection and upper and lower position limit protection; when the constant speed mode is set, the constant speed and constant pressure pump can continuously pump fluid with a constant flow rate and no pulses, while automatically detecting the pressure and flow signals in the pump barrel, and has a pressure upper limit protection function; when the constant speed and constant pressure pump is set to constant pressure mode, it can ensure that the pressure inside the pump is constant.

[0015] Preferably, the confining pressure loading device is a high-pressure manual pump, which can apply confining pressure to the oil shale fracturing model. The high-pressure manual pump is located after the oil shale fracturing model and connected to the lower end of the model body. It applies confining pressure to the core through water injection to realistically simulate the actual pressure conditions under the formation. A confining pressure gauge is installed on the connection line between the high-pressure manual pump and the model body to detect the magnitude of the confining pressure in real time.

[0016] Preferably, the medium-frequency heating device is a high-temperature heater, which can heat the oil shale fracturing model; the thermal trigger valve is located in the high-temperature heater, and can automatically open the high-temperature heater after receiving the signal from the pressure control valve; the high-temperature heater is connected to a copper tube wrapped around the outside of the model body; the high-temperature heater heats the copper tube, and the heat is transferred to the model body through the copper tube, and then transferred from the model body to the rock core, thereby realizing the heating, heat preservation and cooling of the rock core.

[0017] Preferably, the main body of the model is a high-temperature and high-pressure reactor, made of high-strength materials, which can be repeatedly used without deformation and still has high strength under high temperature and pressure. The oil shale fracturing model includes a core sleeve, an aluminum sleeve, a graphite ring, and a flange. The core sleeve has holes to apply confining pressure to the core. The aluminum sleeve can tightly wrap the core and protect it. The aluminum sleeve is longer than the core and fits in the center of the core sleeve. The core is placed in the aluminum sleeve, and the upper and lower core holders are tightly attached to the core, with the narrow end also wrapped by the aluminum sleeve. The confining pressure loading device (high-pressure manual pump) injects water through the holes on the surface of the core sleeve to apply pressure to the aluminum sleeve, thereby applying confining pressure to the core.

[0018] Graphite rings are stacked layer by layer at both ends of the core sleeve, wrapping around the core holder; flanges are located at both ends of the model body, with the narrower end protruding and able to be inserted into the vessel body; the flanges can be screwed inward to compress the graphite rings, making the graphite rings contact more tightly.

[0019] Preferably, the pressure detection module consists of an inlet pressure gauge and a confining pressure gauge, used for detecting the pressure and confining pressure at the inlet of the model body; the pressure sensor in the pressure gauge can collect the pressure in the process in real time and transmit it to the computer for real-time display.

[0020] The pressure control valve is connected to the inlet pressure gauge. When the fracturing pressure drops to the set threshold, it can transmit a signal to trigger the thermally sensitive valve to open.

[0021] The temperature detection module uses a K-type thermocouple to collect temperature data in real time; the acoustic emission detection module is an acoustic emission instrument placed on the inner wall of the model body, which can collect acoustic emission events during the core fracturing process in real time.

[0022] A method for operating an integrated supercritical CO2 fracturing and in-situ conversion device for oil shale includes the following steps:

[0023] The gas cylinder is connected to the temperature control device (high and low temperature constant temperature water bath) through a pipeline. CO2 fluid is introduced into the temperature control device (high and low temperature constant temperature water bath) through valve 1. Valve 2 is opened and valve 3 is closed, and the fluid is directly introduced into the high pressure stirring device.

[0024] The temperature control device (high and low temperature constant temperature water bath) is located between the gas cylinder and the high pressure stirring device. When the temperature control device (high and low temperature constant temperature water bath) is turned on and the temperature is set to 6°C, the high pressure stirring device is kept at the same temperature through the coil. In this system, CO2 gas is converted from gaseous state to liquid state.

[0025] Wrap the core with an aluminum sleeve and fix it at both ends with a core holder. Put the core sleeve on to the core position in the middle of the aluminum sleeve. Install graphite rings at both ends of the core holder. Then put the whole thing into the reactor. Install flanges on both ends of the reactor and tighten the screws to make the graphite rings make tight contact.

[0026] The high-pressure stirring device is located between the temperature control device (high and low temperature constant temperature water bath) and the main body of the model. When the servo stirring motor is turned on, the magnetic particle starts to rotate, so that the liquid CO2 is fully mixed with the thickener, catalyst and other treatment agents in the cavity of the high-pressure stirring device.

[0027] By using the confining pressure loading device (high-pressure manual pump), rotate the hand crank clockwise to pump water into the model body to apply confining pressure, and observe the magnitude of the confining pressure through the confining pressure gauge;

[0028] When valve 2 is closed and valve 3 is opened, CO2 gas enters the constant speed and constant pressure pump. The fluid injection mode is adjusted by the pressure tracking controller. When valve 4 is opened, CO2 gas forces the piston downward, causing the pressure inside the cavity to rise.

[0029] Open valve 6 and close valve 8 (when valve 8 is open, the CO2 fluid is directly connected to the reactor without the high-pressure stirring device; when the supercritical CO2 fracturing fluid carries the catalyst, valve 8 needs to be closed). Under pressure, the fracturing fluid is introduced into the inlet of the model body through the pipeline and injected into the core through the core holder to perform fracturing.

[0030] After fracturing is completed, open the confining pressure unloading valve to unload the confining pressure inside the model body, close the automatic pressure relief valve, and wait for the internal pressure of the model body to rise to the specified range before closing the gas cylinder and the temperature control device (high and low temperature constant temperature water bath).

[0031] Turn on the medium frequency heating device to heat the copper pipe. The heat is transferred to the main body of the model through the copper pipe to carry out in-situ conversion and heating of the oil shale. The pyrolyzed oil shale oil flows out from the outlet of the main body of the model.

[0032] Open the product collection valve, start the high-pressure pump, and the mobile phase, after degassing, passes through the system at a set flow rate; the collected oil shale oil sample is quantitatively injected into the mobile phase via an autosampler, and the mixture enters the chromatographic column in the column oven to achieve component separation; the separated products are sequentially entered into the mass spectrometer for molecular weight and structure analysis, and the concentration information of each component is obtained by combining the chromatographic peak area.

[0033] After collection, open the automatic pressure relief valve, open valve 5 and valve 7 to release the gas in the pipeline, turn off the medium frequency heating device, and loosen the screws after the model body has cooled to room temperature. Take out the entire model body, remove the graphite ring, remove the core sleeve, take out the core holder, remove the aluminum sleeve, and take out the core.

[0034] Compared with existing technologies, this invention designs an oil shale fracturing model, realizing an integrated development mode of oil shale through fracturing followed by pyrolysis. This invention is the first to propose an experimental device and method integrating supercritical CO2 fracturing and in-situ conversion of oil shale. By achieving deep coupling of supercritical CO2 fracturing fracture network formation, uniform catalyst dispersion, and in-situ conversion processes, it overcomes the limitations of existing technologies that only conduct single fracturing or pyrolysis experiments. Simultaneously, it employs innovative designs such as efficient mixing of catalyst and supercritical CO2, precise temperature control via medium-frequency heating, efficient fracture network formation, and real-time temperature and pressure monitoring, resulting in a more comprehensive and advanced technical solution.

[0035] This project innovatively integrates and optimizes a hydraulic fracturing-pyrolysis coupled experimental platform to address the high-temperature, high-pressure, and fracture-conducting environment required for in-situ underground conversion of oil shale. During the fracturing stage, a catalyst is added to the high-pressure stirring device, allowing supercritical CO2 fluid to carry and uniformly disperse the catalyst within the oil shale core during fracturing, achieving full penetration and uniform spread of the catalyst. After fracturing, no device replacement is required, allowing direct entry into the pyrolysis stage. This ensures the synergistic effect of the fracture network and catalyst distribution, significantly improving oil shale conversion efficiency and oil production, and providing a referable process route and parameter basis for in-situ development.

[0036] Unlike existing technologies, this invention features specialized coupling optimization in its structure and control system. The reactor serves as both a fracturing chamber and a pyrolysis chamber, incorporating a built-in temperature-pressure linkage conversion module, including a thermosensitive trigger valve and a pressure control valve. When the system detects a drop in fracturing pressure to a set threshold, the thermosensitive trigger valve automatically activates the medium-frequency heating device, directly entering pyrolysis mode within the reactor without the need for pressure relief or core replacement, achieving dynamic and continuous fracturing-pyrolysis conversion. The medium-frequency heating system and the CO2 fluid pathway of this invention form a dual-loop coupled structure, utilizing the exothermic expansion effect of supercritical CO2 for energy reuse. The residual high-pressure CO2 formed during the fracturing stage assists in heat transfer during the pyrolysis stage, thereby improving energy utilization and pyrolysis uniformity.

[0037] The beneficial effects of this invention are as follows:

[0038] 1. This invention, through a constant-speed constant-tower pump and a high-low temperature constant-temperature bath, can achieve the phase transformation of CO2 by adjusting the pressure and temperature, and can conduct fracturing experiments of CO2 in different phases according to experimental requirements;

[0039] 2. The present invention has a high-pressure stirring device, which can be used to add different thickeners, catalysts and other treatment agents to prepare different CO2 fracturing fluids. At the same time, it can make the catalyst mix better with the fracturing fluid, penetrate deeper into the rock core during the fracturing process, and increase the contact area between the catalyst and the oil shale.

[0040] 3. The temperature and pressure linkage conversion module set in this invention can automatically identify the end of the fracturing stage and start the heating and diversion process to form a dynamic continuous process of fracturing-pyrolysis, realizing integrated control of the "force-heat" dual field;

[0041] 4. The medium-frequency heating system designed in this invention forms a dual-loop coupling structure with the CO2 fluid channel. The outer loop consists of a copper tube wound around the outer wall of the reactor and a medium-frequency heating device, which continuously supplies heat to the reactor wall through the copper tube. The inner loop is the CO2 fluid circulation path inside the reactor. After being heated inside the reactor, CO2 forms a closed flow along the product flow path. The two loops use the reactor wall as the coupling interface, and heat exchange is achieved through wall heat transfer. When the local temperature of the reactor body rises, the internal CO2 absorbs heat and transfers the heat to the lower temperature area inside the reactor with the fluid flow, thereby forming an internal heat cycle. This makes the temperature distribution of the reactor body and the core more uniform, realizes the internal recycling of some heat, improves energy utilization efficiency, and accelerates the pyrolysis process. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0043] Figure 2 This is a schematic cross-sectional view of the oil shale fracturing model of the present invention;

[0044] Figure 3 This is a schematic diagram of the high-pressure stirring device of the present invention;

[0045] The components include: 1. CO2 cylinder; 2. Cylinder pressure gauge; 3. Pipeline; 4. Valve 1; 5. High and low temperature constant temperature bath; 6. Valve 2; 7. Valve 3; 8. Constant speed and constant pressure pump; 9. Pressure tracking controller; 10. High pressure stirring device; 11. Valve 4; 12. Valve 5; 13. Valve 6; 14. Valve 7; 15. Valve 8; 16. Inlet pressure gauge; 17. Reactor; 18. Copper pipe; 19. Medium frequency heating device; 20. Confining pressure gauge; 21. High pressure manual pump; 22. Hand crank. 23. Rod; 24. Reactor inlet; 25. Screw; 26. Clamping device for fracturing wellbore; 27. Confining pressure unloading valve; 28. Core; 29. ​​Graphite ring; 30. Core clamping device; 31. Core sleeve; 32. Flange; 33. Reactor outlet; 34. Piston; 35. Cavity; 36. Magnetic pad; 37. Servo stirring motor; 38. Coil; 39. High-pressure pump; 40. Autosampler; 41. Chromatographic column; 42. Column oven; 43. Detector; 44. Automatic pressure relief valve; 45. Product collection valve. Detailed Implementation

[0046] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Examples of the embodiments are shown in the drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0047] Example 1

[0048] An integrated device for supercritical CO2 fracturing and in-situ conversion of oil shale, such as... Figure 1-3 As shown, it includes: a CO2 liquefaction and storage system, an oil shale fracturing and heating system, an oil shale fracturing model, a data monitoring system, and a product analysis system.

[0049] A CO2 liquefaction and storage system includes a CO2 cylinder, a temperature control device, and a high-pressure stirring device. The temperature control device is mainly used to cool the CO2, converting gaseous CO2 into liquid CO2, which is then pressurized to reach a supercritical state. The high-pressure stirring device is mainly used to stir the CO2 fluid, thickener, and catalyst to ensure uniform mixing, allowing the CO2 fluid to carry the catalyst and be injected into the oil shale. The temperature control device is a high-low temperature constant-temperature bath, which can be used to control the temperature of CO2 through coils to achieve phase transformation of CO2. The high-low temperature constant-temperature bath is located between the CO2 cylinder and the constant-speed constant-pressure pump, connected to the high-pressure stirring device, to maintain a constant temperature throughout the entire system pipeline, ensuring that the CO2 is in the same phase. The high-pressure stirring device uses a magnetic stirrer to mix the supercritical CO2, thickener, and catalyst. The high-pressure stirring device is located between the constant-speed constant-pressure pump and the oil shale fracturing model, used to deliver the mixed supercritical CO2 and thickener to the oil shale fracturing model for oil shale fracturing.

[0050] The oil shale fracturing and heating system includes a constant-speed, constant-pressure pump, a confining pressure loading device, a medium-frequency heating device, and a pressure tracking controller. The constant-speed, constant-pressure pump is located between the temperature control device (high and low temperature constant-temperature bath) and the pressure tracking controller. It is primarily used for continuous CO2 injection and features pressure protection and upper / lower position limit protection. It can be adjusted to either constant-speed or constant-pressure mode. In constant-speed mode, it continuously pumps fluid at a constant flow rate without pulses, while automatically detecting the pressure and flow signals within the pump barrel, and includes a pressure upper limit protection function. In constant-pressure mode, it ensures constant pressure within the pump. The confining pressure loading device is a high-pressure manual pump, primarily used to apply confining pressure to the core sample to better simulate formation conditions. Located after the oil shale fracturing model and connected to the lower end of the model body, the high-pressure manual pump applies confining pressure to the core sample through water injection to realistically simulate the actual pressure conditions beneath the formation. A confining pressure gauge is installed on the connection line between the high-pressure manual pump and the model body to monitor the confining pressure in real time. The intermediate frequency heating device is a high-temperature heater, mainly used to heat oil shale after fracturing to achieve in-situ conversion of oil shale. The system is equipped with a temperature and pressure linkage switching valve group, including an automatic pressure relief valve, a thermosensitive trigger valve, and a pressure control regulating valve, for automatic switching to pyrolysis after the fracturing stage. When the system detects that the fracturing pressure has dropped to a threshold, the control unit automatically starts the intermediate frequency heating device and simultaneously injects CO2 to raise the internal pressure of the reactor to a specified range, realizing CO2 circulation during the pyrolysis stage. The thermosensitive trigger valve is located in the high-temperature heater and automatically opens the high-temperature heater after receiving a signal from the pressure control regulating valve. The high-temperature heater is connected to a copper tube wrapped around the outside of the model body. The high-temperature heater heats the copper tube, and the heat is transferred through the copper tube to the model body, and then from the model body to the rock core, thereby achieving heating, heat preservation, and cooling of the rock core.

[0051] The oil shale fracturing model includes the model body and a core holder. The core holder has a fracturing wellbore, with a protruding injection end for inserting the core, and a flat outlet end. The injection end of the core holder is inserted into the core, and fluid enters the core through the fracturing wellbore under the action of a constant speed and pressure pump to fracture the core. The outlet end is flat and closely adheres to the core.

[0052] The main body of the model is a high-temperature and high-pressure reactor, made of high-strength materials, which can be reused without deformation and still maintain high strength under high temperature and pressure. The oil shale fracturing model includes a core sleeve, an aluminum sleeve, a graphite ring, and a flange. The core sleeve has holes to apply confining pressure to the core. The aluminum sleeve can tightly wrap the core and protect it. The aluminum sleeve is longer than the core and fits in the center of the core sleeve. The core is placed in the aluminum sleeve, and the upper and lower parts of the core holder are tightly attached to the core, with the narrow end also wrapped by the aluminum sleeve. The confining pressure loading device (high-pressure manual pump) injects water through the holes on the surface of the core sleeve to apply pressure to the aluminum sleeve, thereby applying confining pressure to the core.

[0053] Graphite rings are stacked layer by layer at both ends of the core sleeve, wrapping around the core holder; flanges are located at both ends of the model body, with the narrower end protruding and able to be inserted into the vessel body; the flanges can be screwed inward to compress the graphite rings, making the graphite rings contact more tightly.

[0054] The data monitoring system includes a temperature detection module, a pressure detection module, and an acoustic emission detection module. The temperature detection module is used to detect the temperature of the main body of the in-situ conversion system model, the pressure detection module is used to detect the injection end pressure and confining pressure of the core holder, and the acoustic emission detection module is placed on the inner wall of the main body of the model to capture the formation signal of hydraulic fracturing induced fractures.

[0055] The pressure detection module consists of an inlet pressure gauge and a confining pressure gauge, used for detecting the pressure and confining pressure at the inlet of the model body. The pressure sensor in the pressure gauge can collect the pressure during the process in real time and transmit it to the computer for real-time display. The pressure control regulating valve is connected to the inlet pressure gauge, and when the fracturing pressure drops to the set threshold, it can transmit a signal to trigger the thermal trigger valve to open. The temperature detection module uses a K-type thermocouple to collect the temperature in real time. The acoustic emission detection module is an acoustic emission instrument placed on the inner wall of the model body, which can collect acoustic emission events during the core fracturing process in real time.

[0056] The product analysis system mainly includes a product collection module and an analysis module. The product collection module collects pyrolysis products via an autosampler, and the analysis module is a mass spectrometer detector that can perform molecular weight and structural analysis on the pyrolysis products.

[0057] Example 2

[0058] A method for operating an integrated supercritical CO2 fracturing and in-situ conversion device for oil shale includes the following steps:

[0059] CO2 cylinder 1 is connected to high and low temperature constant temperature water bath 5 through pipeline. CO2 fluid is introduced into high and low temperature constant temperature water bath 5 through valve 1 (4). Valve 2 (6) is opened and valve 3 (7) is closed, and it can be directly introduced into high pressure stirring device 10.

[0060] The high and low temperature constant temperature water bath 5 is located between the CO2 gas cylinder 1 and the high pressure stirring device 10. The high and low temperature constant temperature water bath 5 is turned on and the temperature is set to 6°C. Through the coil 37, the high pressure stirring device 10 is kept at the same temperature. In this system, the CO2 gas is changed from gaseous to liquid.

[0061] Wrap the core 27 with an aluminum sleeve and fix both ends with core holders 29. Put the core sleeve 30 on to the core position in the middle of the aluminum sleeve. Install graphite rings 28 on both ends of the core holders 29. Then put the whole thing into the reactor 17. Install flanges 31 on both ends of the reactor 17 and screws 24 to make the graphite rings 28 in tight contact.

[0062] The high-pressure stirring device 10 is located between the high-low temperature constant temperature water bath 5 and the reaction vessel 17. When the servo stirring motor 36 is turned on, the magnetic particle 35 starts to rotate, so that the liquid CO2 is fully mixed with the thickener, catalyst and other treatment agents in the cavity 34 part of the high-pressure stirring device 10.

[0063] Water is pumped into the reactor 17 by manually rotating the hand crank 22 clockwise using the high-pressure pump 21 to apply confining pressure. The magnitude of the confining pressure is observed using the confining pressure gauge 20.

[0064] Close valve 2 (6), open valve 3 (7), CO2 gas enters constant speed and constant pressure pump 8, and through pressure tracking controller 9, adjusts the fluid injection mode, and opens valve 4 (11), CO2 gas presses piston (33) downward, causing the pressure in cavity (34) to rise.

[0065] Open valve 6 (13) and close valve 8 (15) (when valve 8 (15) is open, CO2 fluid is directly connected to 17 without high pressure stirring device. During the fracturing process of supercritical CO2 fracturing fluid carrying catalyst, valve 8 (15) needs to be closed). Under pressure, fracturing fluid is introduced into reactor inlet 23 of reactor 17 through pipeline and injected into core 27 through fracturing wellbore 25 by clamping device for fracturing.

[0066] After fracturing is completed, open the confining pressure unloading valve 26 to unload the confining pressure inside the reactor 17, close the automatic pressure relief valve 43, and wait for the internal pressure of the reactor to rise to the specified range before closing the gas cylinder 1 and the water bath.

[0067] Turn on the medium frequency heating device 19 to heat the copper pipe 18. The heat is transferred to the reactor 17 through the copper pipe 18 to carry out in-situ conversion heating of the oil shale. The pyrolyzed oil shale oil flows out from the reactor outlet 32.

[0068] Open the product collection valve 44, start the high-pressure pump 38, and the mobile phase, after degassing, passes through the system at a set flow rate; the collected oil shale oil sample is quantitatively injected into the mobile phase through the autosampler 39, and the mixture enters the chromatographic column 40 in the column oven 41 to achieve component separation; the separated products are sequentially entered into the mass spectrometer detector 42 for molecular weight and structure analysis, and the concentration information of each component is obtained by combining the chromatographic peak area.

[0069] After collection, open the pressure relief valve 43, open valve 5 (12) and valve 7 (14) to release the gas in the pipeline, close the medium frequency heating device 19, and loosen the screw 24 after the reactor 17 has cooled to room temperature. Take out the entire reactor 17, remove the graphite ring 28, remove the core sleeve 30, take out the core holder 29, remove the aluminum sleeve, and take out the core.

Claims

1. An integrated device for supercritical CO2 fracturing and in-situ conversion of oil shale, characterized in that, include: CO2 liquefaction storage system, oil shale fracturing and heating system, oil shale fracturing model, data monitoring system and product analysis system; The CO2 liquefaction storage system includes a CO2 cylinder, a temperature control device, and a high-pressure stirring device. The temperature control device is used to cool the CO2, converting gaseous CO2 into liquid CO2. The high-pressure stirring device is used to stir the CO2 fluid, thickener, and catalyst. The temperature control device is a high-low temperature constant temperature bath for controlling the temperature of the CO2. The high-low temperature constant temperature bath is located between the CO2 cylinder and the constant speed and constant pressure pump and is connected to the high-pressure stirring device. The oil shale fracturing and heating system includes a constant-speed, constant-pressure pump, a confining pressure loading device, and a medium-frequency heating device. The constant-speed, constant-pressure pump is used for continuous CO2 injection, with adjustable constant-speed or constant-pressure modes. The confining pressure loading device applies confining pressure to the core. The medium-frequency heating device heats the oil shale after fracturing. The confining pressure loading device is a high-pressure manual pump that applies confining pressure to the oil shale fracturing model. The high-pressure manual pump is connected to the lower end of the model body and applies confining pressure to the core through water injection. A confining pressure gauge is installed on the connection line between the high-pressure manual pump and the model body. The medium-frequency heating device is a high-temperature heater that heats the oil shale fracturing model. A thermosensitive trigger valve is located in the high-temperature heater and automatically opens the high-temperature heater after receiving a signal from the pressure control valve. The high-temperature heater is connected to a copper pipe wound around the outside of the model body. The system is equipped with a temperature-pressure linkage switching valve group, including an automatic pressure relief valve, a thermosensitive trigger valve, and a pressure control valve, for automatically switching to pyrolysis after the fracturing stage is completed. The oil shale fracturing model includes a model body and a core holder. The core holder has a fracturing wellbore with a protruding injection end for inserting the core. The model body is a high-temperature, high-pressure reactor. The oil shale fracturing model includes a core sleeve, an aluminum sleeve, graphite rings, and flanges. The core sleeve has perforations. The aluminum sleeve is longer than the core and fits around the center of the core sleeve, with the core placed inside. The upper and lower parts of the core holder are tightly attached to the core. A confining pressure loading device injects water through the perforations on the surface of the core sleeve to apply pressure to the aluminum sleeve, thereby applying confining pressure to the core. Graphite rings are stacked at both ends of the core sleeve, wrapping around the core holders. Flanges are located at both ends of the model body. The flanges are screwed inward to compress the graphite rings. The data monitoring system includes a temperature detection module, a pressure detection module, and an acoustic emission detection module. The temperature detection module detects the temperature of the model body, the pressure detection module detects the injection end pressure and confining pressure of the core holder, and the acoustic emission detection module is placed on the inner wall of the model body to capture the formation signal of fracturing-induced fractures. The pressure detection module consists of an inlet pressure gauge and a confining pressure gauge for detecting the inlet pressure and confining pressure of the model body. The pressure sensor in the pressure gauge collects the pressure during the process in real time and transmits it to the computer for real-time display. The pressure control regulating valve is connected to the inlet pressure gauge, and when the fracturing pressure drops to a set threshold, it transmits a signal to trigger the thermally sensitive valve to open. The product analysis system includes a product collection module and an analysis module. The product collection module collects pyrolysis products using an autosampler, and the analysis module uses a mass spectrometer to perform molecular weight and structural analysis on the pyrolysis products.

2. The integrated device for supercritical CO2 fracturing and in-situ conversion of oil shale as described in claim 1, characterized in that, The high-pressure stirring device uses a magnetic stirrer to mix supercritical CO2, thickener, and catalyst. The high-pressure stirring device is located between the constant-speed and constant-pressure pump and the oil shale fracturing model. It is used to mix supercritical CO2 with thickener and then deliver it to the oil shale fracturing model for oil shale fracturing.

3. The integrated device for supercritical CO2 fracturing and in-situ conversion of oil shale as described in claim 1, characterized in that, The oil shale fracturing and heating system also includes a pressure tracking controller; a constant speed and constant pressure pump is located between the temperature control device and the pressure tracking controller.

4. The integrated device for supercritical CO2 fracturing and in-situ conversion of oil shale as described in claim 1, characterized in that, The temperature detection module uses a K-type thermocouple to collect temperature data in real time; the acoustic emission detection module is an acoustic emission instrument that collects acoustic emission events during the core fracturing process in real time.

5. A method for operating the integrated supercritical CO2 fracturing and in-situ conversion device for oil shale as described in claim 1, characterized in that, The steps include the following: The gas cylinder is connected to the temperature control device via pipeline. CO2 fluid is introduced into the temperature control device through a valve and then directly into the high-pressure stirring device. The temperature control device is located between the gas cylinder and the high-pressure stirring device. When the temperature control device is turned on and the temperature is set to 6°C, the high-pressure stirring device is kept at the same temperature through the coil. In this system, CO2 gas is converted from gaseous to liquid state. Wrap the core with an aluminum sleeve, fix both ends with core holders, put on the core sleeve, install graphite rings on both ends of the core holders, then put the whole thing into the reactor, install flanges on both ends of the reactor, tighten screws to make the graphite rings make tight contact; The high-pressure stirring device is located between the temperature control device and the main body of the model. When the servo stirring motor is turned on, the magnetic particle starts to rotate, so that the liquid CO2 is fully mixed with the thickener and catalyst in the cavity of the high-pressure stirring device. By rotating the hand crank clockwise through the confining pressure loading device, water is pumped into the model body to apply confining pressure, and the magnitude of the confining pressure is observed through the confining pressure gauge. CO2 gas enters the constant speed and constant pressure pump. Through the pressure tracking controller, the fluid injection mode is adjusted. The CO2 gas forces the piston downward, causing the pressure inside the cavity to rise. Under pressure, fracturing fluid is introduced into the inlet of the model body through the pipeline, and injected into the core through the core holder to perform fracturing; After fracturing is completed, open the confining pressure unloading valve to unload the confining pressure inside the model body, close the automatic pressure relief valve, and wait for the internal pressure of the model body to rise to the specified range before closing the gas cylinder and the temperature control device. Turn on the medium frequency heating device to heat the copper pipe. The heat is transferred to the main body of the model through the copper pipe to carry out in-situ conversion and heating of the oil shale. The pyrolyzed oil shale oil flows out from the outlet of the main body of the model. Open the product collection valve, start the high-pressure pump, and the mobile phase, after degassing, passes through the system at a set flow rate; the collected oil shale oil sample is quantitatively injected into the mobile phase via an autosampler, and the mixture enters the chromatographic column in the column oven to achieve component separation; the separated products are sequentially entered into the mass spectrometer for molecular weight and structure analysis, and the concentration information of each component is obtained by combining the chromatographic peak area. After collection is complete, open the automatic pressure relief valve to release the gas in the pipeline, turn off the medium frequency heating device, and loosen the screws after the model body has cooled to room temperature. Remove the entire model body, remove the graphite ring, remove the core sleeve, remove the core holder, remove the aluminum sleeve, and remove the core.

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