Large-size oil-rich coal in-situ pyrolysis exploitation physical simulation experiment method

Abstract

The application discloses a large-size oil-rich coal in-situ pyrolysis mining physical simulation experiment device and method, which comprises a reaction kettle body, a deep ground stress loading system communicated with the reaction kettle body, an impact wave fracturing system, a heat carrier fluid injection system, an ultrasonic detection system, an optical fiber temperature-stress-strain sensing system and a pyrolysis oil and gas collection and separation system; the oil-rich coal sample in the reaction kettle body is subjected to confining pressure, impact wave fracturing and injection of high-temperature heat carrier fluid to stimulate the pyrolysis reaction of the oil-rich coal; the ultrasonic detection is used to detect the crack development state of the oil-rich coal sample before and after pre-cracking; the temperature, strain and pyrolysis oil and gas migration parameters of the oil-rich coal in the reaction kettle body in the pyrolysis process are monitored in real time, the in-situ pyrolysis effect of the oil-rich coal is evaluated, the in-situ efficient heat injection mining method of the oil-rich coal under different heat injection modes and parameter conditions is explored, and reliable experimental basis is provided for the in-situ heat injection engineering amplification and pyrolysis mining industrialization test of the oil-rich coal.

Description

Technical Field

[0001] This invention belongs to the field of green and low-carbon coal mining technology, and relates to a physical simulation experimental device and method for large-scale in-situ pyrolysis mining of oil-rich coal. Background Technology

[0002] Oil-rich coal is a coal-based oil and gas resource with a tar yield of 7% to 22%, and it is a strategic oil and gas resource with great potential.

[0003] In-situ pyrolysis mining technology for rich oil-bearing coal aligns with the new development philosophy and the development trend of the coal industry, and is one of the important ways to achieve green, low-carbon mining and efficient cascade utilization of rich oil-bearing coal. Compared with underground pyrolysis technology for shale oil (gas), in-situ pyrolysis mining of rich oil-bearing coal is currently in the early exploratory stage, lacking physical simulation experimental devices for in-situ pyrolysis mining of rich oil-bearing coal, which brings considerable difficulties to the efficient development and utilization of rich oil-bearing coal, the determination of underground in-situ pyrolysis mining methods, and the comprehensive determination of key technical parameters.

[0004] To explore and develop new theories and technologies for in-situ pyrolysis mining of oil-rich coal, monitor the in-situ pyrolysis process of oil-rich coal well drilling in real time, and study and obtain fracturing, efficient in-situ heat injection methods and key technical parameters of oil-rich coal reservoirs, this invention provides a large-scale physical simulation experimental device and method for in-situ pyrolysis mining of oil-rich coal. Summary of the Invention

[0005] To address the aforementioned deficiencies in the existing technology, the present invention aims to provide a physical simulation experimental device and method for large-size in-situ pyrolysis mining of oil-rich coal, enabling physical simulation experiments of the large-size in-situ pyrolysis process of oil-rich coal and determination of multiphase and multi-field dynamic parameters, thus providing a fundamental experimental basis for achieving efficient in-situ heating, efficient heat transfer and regulation of oil-rich coal.

[0006] The present invention is achieved through the following technical solution.

[0007] According to one aspect of the present invention, a large-scale physical simulation experimental apparatus for in-situ pyrolysis mining of oil-rich coal is provided, comprising:

[0008] The deep geostress loading system applies confining pressure to the oil-rich coal sample inside the experimental chamber of the reactor body.

[0009] The heat transfer fluid injection system is used to inject high-temperature heat transfer fluid into the oil-rich coal sample in the experimental chamber of the reactor to activate the pyrolysis reaction of the oil-rich coal.

[0010] A controllable shock wave fracturing system is used to apply shock wave fracturing to oil-rich coal samples in the experimental chamber of a reactor.

[0011] Ultrasonic testing system for detecting fracture development information in oil-rich coal samples before and after fracturing;

[0012] Fiber optic temperature-stress-strain sensing system for distributed fiber optic stress-strain testing;

[0013] The pyrolysis oil and gas collection and separation system monitors the temperature, strain, and pyrolysis oil and gas migration parameters of the oil-rich coal in the reactor in real time during the pyrolysis process, and evaluates the effect of in-situ pyrolysis of oil-rich coal.

[0014] Preferably, the reactor body is a cylindrical steel structure reactor body, and a cuboid experimental chamber is set inside the steel structure reactor body; a heat insulation layer is arranged between the walls of the experimental chamber, and an oil-rich coal sample wrapped with sealing colloid is placed inside the experimental chamber; the experimental chamber is equipped with a channel connecting the heat transfer fluid injection system and the controllable shock wave fracturing system.

[0015] Preferably, the deep geostress loading system includes a nitrogen cylinder group, a booster pump, and a cooling system connected in sequence, with the air compressor connected to the booster pump and the gas injection pump connected to the cooling system.

[0016] Preferably, the fiber optic temperature-stress-strain sensing system includes a fiber optic temperature sensor and a stress-strain sensor arranged inside the oil-rich coal sample. The fiber optic temperature sensor and the stress-strain sensor are respectively connected to the fiber optic temperature testing system and the stress-strain testing system via insulated, heat-resistant, and armored optical cables.

[0017] As a preferred option, high-temperature steam injection wells and pyrolysis product collection wells, as well as fiber optic temperature measuring holes and stress-strain measuring holes are arranged in the oil-rich coal sample in the experimental chamber.

[0018] Preferably, the heat transfer fluid injection system includes a water container, a liquid injection pump and a steam generator connected in sequence. The steam generator is connected to a high-temperature steam injection well to the interior of the oil-rich coal sample in the experimental chamber, and a cooling port is provided on the pipeline connecting the steam generator.

[0019] Preferably, the pyrolysis oil and gas collection and separation system includes a gas-liquid separator, a filter, a dryer, a gas chromatograph, and a computer acquisition system connected in sequence; a sampling bottle is connected to the gas-liquid separator.

[0020] Preferably, the controllable shock wave fracturing system includes a motor, which is connected to the shock wave action end placed inside the oil-rich coal sample via a power control line and channel.

[0021] Preferably, the ultrasonic testing system includes an ultrasonic excitation transducer and an ultrasonic receiving transducer arranged on both sides of the oil-rich coal sample. The ultrasonic excitation transducer and the ultrasonic receiving transducer are connected to a waveform generator, which is sequentially connected to a high-frequency high-voltage amplifier, an oscilloscope, and a computer control system.

[0022] According to another aspect of the present invention, a physical simulation experimental method for large-scale in-situ pyrolysis mining of oil-rich coal using the aforementioned apparatus is provided, comprising:

[0023] A controllable shock wave and a high-temperature steam injection well were placed at the top of the oil-rich coal sample, and a pyrolysis product collection well was placed at the bottom of the coal sample.

[0024] An optical fiber connecting a fiber temperature sensor and a stress strain sensor is inserted into an oil-rich coal sample. An ultrasonic excitation transducer and an ultrasonic receiving transducer are respectively arranged on both sides of the oil-rich coal sample.

[0025] The oil-rich coal sample was sealed and placed into the experimental chamber with a heat insulation layer, and the armored optical cable connector was sealed and connected to the connector outside the reactor body.

[0026] High-pressure nitrogen gas is introduced into the reactor body, and confining pressure is applied step by step to the predetermined load through the deep in-situ stress loading system;

[0027] The controllable shock wave fracturing system was activated to pre-fracture the oil-rich coal sample in the experimental chamber. The ultrasonic oscilloscope monitored the fracture development status at different locations of the oil-rich coal sample in real time, so that a horizontal and vertical fracture network was formed inside the sample.

[0028] Nitrogen gas is released through the exhaust port, and the confining pressure is gradually reduced to normal atmospheric pressure to end the ultrasonic testing.

[0029] The deep geostress loading system is activated to apply confining pressure step by step to the predetermined load, and the confining pressure is monitored by pressure sensors on the reactor body.

[0030] Start the heat transfer fluid injection system and inject high-temperature water vapor into the oil-rich coal sample in the experimental chamber at a certain pressure and temperature to stimulate the pyrolysis reaction of the oil-rich coal.

[0031] Fiber optic temperature sensors and stress-strain sensors are used to monitor the temperature, stress, and strain characteristics of oil-rich coal samples at different locations during pyrolysis in real time. The temperature field variation of the oil-rich coal samples is compared and analyzed to evaluate the heat transfer effect and the pyrolysis reaction range.

[0032] The pyrolysis oil and gas collection and separation system was started to collect and measure the composition and content of pyrolysis gas of oil-rich coal samples in the experimental chamber, compare and determine the pyrolysis reaction stages at different locations of oil-rich coal, and evaluate the pyrolysis effect of oil-rich coal samples.

[0033] Modify the test parameters and repeatedly start the deep geostress loading system-controllable shock wave fracturing system-deep geostress loading system-heat transfer fluid injection system until the physical simulation experiment of in-situ pyrolysis mining of oil-rich coal under different stress states and different heat injection methods is completed.

[0034] The present invention, by adopting the above technical solution, has the following beneficial effects:

[0035] 1. An experimental chamber was placed inside a high-temperature, high-pressure reactor, and large-sized oil-rich coal samples were arranged in the chamber. Physical simulation experiments of the in-situ thermal pyrolysis process of large-sized oil-rich coal were conducted under lateral confining pressure, controlled pulse fracturing, and high-temperature heat transfer fluid injection conditions. Ultrasonic testing was used to detect the fracture development state of the oil-rich coal samples before and after pre-fracture. Using ultrasonic testing, fiber optic strain testing systems, and pyrolysis oil and gas collection and separation systems, the heat transfer, temperature field evolution, pyrolysis oil and gas migration characteristics, and key parameters of oil-rich coal at different stages of the in-situ pyrolysis process can be monitored in real time, realizing the study of the solid-liquid-gas-thermal-chemical coupling law of the in-situ pyrolysis process of oil-rich coal.

[0036] 2. The experimental chamber's stress loading, controlled fracturing, and heat injection systems are independent of each other. Distributed fiber optic stress and strain sensing systems, pyrolysis oil and gas collection and separation systems, and other methods are used to monitor in real time the heat transfer, temperature field evolution, pyrolysis oil and gas migration characteristics, and key parameters of oil-rich coal at different stages of the in-situ pyrolysis process. This effectively reveals the multiphase and multifield dynamic evolution law of the in-situ pyrolysis process of large-size oil-rich coal, and provides a basic experimental basis for further research on key technologies for efficient in-situ heating, efficient heat energy transfer, and control of oil-rich coal. Attached Figure Description

[0037] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, do not constitute an undue limitation of the invention. In the drawings:

[0038] Figure 1 This is a schematic diagram of the simulation experimental device of the present invention;

[0039] Figure 2 Schematic diagram of crack induction by a controllable shock wave system;

[0040] Figure 3 A schematic diagram of the ultrasonic testing system layout;

[0041] Figures 4(a)-(c) show the layout of the well network for high-temperature steam injection and pyrolysis oil and gas collection;

[0042] Figures 5(a)-(c) show schematic diagrams of the arrangement of fiber optic temperature and stress-strain sensors;

[0043] In the diagram: 1. Oil-rich coal sample; 2. Reactor body; 3. Experimental chamber; 4. Insulation layer; 5. Nitrogen cylinder group; 6. Booster pump; 7. Air compressor; 8. Cooling system; 9. Gas injection pump; 10. Exhaust port; 11. Safety valve; 12. Motor; 13. Power control line; 14. Sealing flange; 15. Casing; 16. Shock wave action end; 17. Channel; 18. Waveform generator; 19. Ultrasonic excitation transducer; 20. Ultrasonic receiving transducer; 21. High-frequency high-voltage amplifier; 22. Oscilloscope; 23. Computer control system; 24. Water container; 5. Liquid injection pump; 26. Steam generator; 27. Cooling port; 28. High-temperature steam injection well; 29. ​​Fiber optic temperature testing system; 30. Stress and strain testing system; 31. Fiber optic temperature sensor; 32. Stress and strain sensor; 33. Fiber optic temperature measuring hole; 34. Stress and strain measuring hole; 35. Pyrolysis product collection well; 36. Gas-liquid separator; 37. Sampling bottle; 38. Filter; 39. Dryer; 40. Gas chromatograph; 41. Computer acquisition system; 42. Check valve; 43. Thermometer valve; 44. Pressure gauge valve.

[0044] 101 Deep geostress loading system; 102 Heat transfer fluid injection system; 103 Controllable shock wave fracturing system; 104 Fiber optic temperature-stress-strain sensing system; 105 Pyrolysis oil and gas collection and separation system. Detailed Implementation

[0045] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The illustrative embodiments and descriptions of the present invention are used to explain the present invention, but are not intended to limit the present invention.

[0046] like Figure 1 As shown, the present invention provides a large-scale physical simulation experimental device for in-situ pyrolysis mining of oil-rich coal, including a large-scale oil-rich coal pyrolysis reactor body 2, with an experimental chamber 3 built inside the reactor body 2.

[0047] The reactor body 2 is connected to the deep in-situ stress loading system 101, and the experimental chamber 3 is connected to the heat transfer fluid injection system 102, the controllable shock wave fracturing system 103, the ultrasonic detection system, the fiber optic temperature-stress-strain sensing system 104, and the pyrolysis oil and gas collection and separation system 105. Gas pressure, temperature, and flow sensors are respectively installed at the locations of the large-size oil-rich coal pyrolysis reactor body 2, the experimental chamber 3, the deep in-situ stress loading system 101, the heat transfer fluid injection pump, and the pyrolysis oil and gas collection channel.

[0048] The reactor body includes a cylindrical steel structure, inside which a cuboid experimental chamber is installed. In one embodiment, the reactor body has external dimensions of 820×670×560mm, and the experimental chamber is cuboid with internal dimensions of 620×470×360mm, used to hold oil-rich coal samples. The experimental chamber can withstand a maximum temperature of 650–700℃. By sealing the experimental chamber, the oil-rich coal samples inside are isolated from the steel pyrolysis reactor body. A gas pressure gauge is installed on the outside of the steel reactor body to monitor the gas pressure inside the reactor body, so as to control the gas pressure applied by the deep stress loading system.

[0049] The experimental chamber is made of elastic plexiglass; a heat insulation layer 4 is arranged between the walls of the experimental chamber 3; the experimental chamber 3 contains an oil-rich coal sample 1 encapsulated in a sealing colloid; the experimental chamber 3 is equipped with a channel 17 that connects the heat transfer fluid injection system 102 and the controllable shock wave fracturing system 103; the channel 17 connects to the shock wave action end 16 at the top of the oil-rich coal sample 1.

[0050] The deep in-situ stress loading system 101 includes a nitrogen cylinder group 5, a booster pump 6, an air compressor 7, a cooling system 8, a gas injection pump 9, an exhaust port 10, and a safety valve 11. The nitrogen cylinder group 5, booster pump 6, and cooling system 8 are connected sequentially. The air compressor 7 is connected to the booster pump 6, and the gas injection pump 9 is connected to the cooling system 8. The in-situ stress loading system 101 is connected to the reaction vessel 2 via the gas injection pump 9. The nitrogen cylinder group provides nitrogen gas, which is powered by the air compressor to the booster pump. The booster pump increases the gas pressure and injects nitrogen gas into the reaction vessel 2. The high-pressure nitrogen gas applies confining pressure to the oil-rich coal sample 1. The cooling system is used to adjust and cool the temperature of the pressurized nitrogen gas. The gas injection pump has a maximum gas pressure of 15 MPa, enabling stable and high-precision control of gas pressure and flow rate output to simulate the in-situ stress state of deep oil-rich coal seams.

[0051] A one-way valve 42 is installed on the pipeline connecting nitrogen cylinder group 5 and booster pump 6. A pressure gauge valve 44 is installed on the pipeline connecting cooling system 8 and reactor body 2.

[0052] The heat transfer fluid injection system 102 includes a water container 24, a liquid injection pump 25, a steam generator 26, a cooling port 27, and a high-temperature steam injection well 28. The water container 24, the liquid injection pump 25, and the steam generator 26 are connected in sequence. The steam generator 26 is connected to the high-temperature steam injection well 28 and then to the oil-rich coal sample 1 inside the experimental chamber 3. The cooling port 27 is provided on the pipeline connecting the steam generator 26. A thermometer valve 43 is provided on the pipeline of the high-temperature steam injection well 28. The heat transfer fluid is high-temperature steam. The heat transfer fluid injection system 102 is mainly used to inject high-temperature steam into the coal seam fractures to stimulate the pyrolysis reaction of the coal sample and precipitate coal tar and pyrolysis gas.

[0053] The pyrolysis oil and gas collection and separation system 105 includes a pyrolysis product collection well 35, a gas-liquid separator 36, a sampling bottle 37, a filter 38, a dryer 39, a gas chromatograph 40, and a computer acquisition system 41; the gas-liquid separator 36, the filter 38, the dryer 39, the gas chromatograph 40, and the computer acquisition system 41 are connected in sequence; the sampling bottle 37 is connected to the gas-liquid separator 36.

[0054] The gas-liquid separator 36 is used to separate pyrolysis gas and coal tar. It contains a gas volume measuring instrument to measure the flow rate of gas flowing into the separator. A sampling bottle 37 is used to sample and weigh the coal tar. A filter 38 filters impurities from the pyrolysis gas. A dryer 39 dries the pyrolysis gas. A gas chromatograph analyzes the composition of the pyrolysis gas. The pyrolysis oil and gas collection and separation system 105 mainly collects the tar and pyrolysis gas generated during the pyrolysis of the oil-rich coal sample through a pyrolysis product collection well 35 located at the lower end of the steel-structured reactor body 2. It separates and measures the pyrolysis tar, gas components, and content to comprehensively determine the pyrolysis reaction stage and pyrolysis efficiency of the oil-rich coal.

[0055] like Figure 2 As shown, the controllable shock wave fracturing system 103 includes a motor 12, a power control line 13, a sealing flange 14, a casing 15, and a shock wave action end 16. The motor 12 is connected to the shock wave action end 16 through the power control line 13. The power control line 13 passes through a channel 17 into the experimental chamber 3. A sealing flange 14 is provided on the channel 17 of the experimental chamber 3 to ensure the sealing of the channel connection. The casing 15 is used to protect the shock wave action end. The controllable shock wave action end 16 is placed inside the oil-rich coal sample 1 through the channel 17, and an electronic pulse is activated to form a horizontal and vertical fracture network inside the oil-rich coal sample 1.

[0056] like Figure 3 As shown, the ultrasonic testing system includes a waveform generator 18, an ultrasonic excitation transducer 19, an ultrasonic receiving transducer 20, a high-frequency high-voltage amplifier 21, an oscilloscope 22, and a computer control system 23. The ultrasonic excitation transducer 19 and the ultrasonic receiving transducer 20, which are arranged on the left and right sides of the oil-rich coal sample 1, are connected to the waveform generator 18. The waveform generator 18 is connected in sequence to the high-frequency high-voltage amplifier 21, the oscilloscope 22, and the computer control system 23.

[0057] A waveform generator produces a pulse signal, which is then converted into a vibration signal by an ultrasonic excitation transducer. This vibration wave propagates within the fracturing or pyrolysis of oil-rich coal. An ultrasonic receiving transducer receives the signal, and a high-frequency voltage amplifier amplifies the amplitude and frequency of the output waveform signal. An oscilloscope displays the transmitted and received ultrasonic signals, while a computer control system acquires and processes the data. By comparing the differences between the transmitted and received signals, a detailed description of the distribution of layered fractures within the sample can be obtained.

[0058] Ultrasonic transducers connected to the data acquisition system were installed on both sides of the oil-rich coal sample in the experimental chamber.

[0059] By comparing the differences between the transmitted and received ultrasonic waveform signals, the degree of development of horizontal and vertical cracks inside the sample can be described in detail.

[0060] As shown in Figures 4(a)-(c), the high-temperature steam injection well 28 and the pyrolysis product collection well 35 are further arranged in the oil-rich coal sample 1 in the experimental chamber 3. In one embodiment, the arrangement is as follows: a borehole with a diameter of 20 mm and a depth of 360 mm is arranged at the center of the top of the oil-rich coal sample to place the high-temperature steam injection well 28; at the bottom of the sample 1, with the high-temperature steam injection well 28 as the center, six hexagonally distributed boreholes with a diameter of 30 mm, a depth of 300 mm, and a spacing of 135 mm are arranged to place the pyrolysis product collection well 35.

[0061] As shown in Figures 5(a)-(c), the fiber optic temperature-stress-strain sensing system 104 further includes a distributed fiber optic temperature testing system 29, a stress-strain testing system 30, a fiber optic temperature sensor 31, and a stress-strain sensor 32. The fiber optic temperature testing system 29 and the stress-strain testing system 30 are respectively connected to the fiber optic temperature sensor 31 and the stress-strain sensor 32 arranged inside the oil-rich coal sample 1 through insulated, heat-resistant, and heat-insulating armored optical cables. The distribution of the fiber optic temperature sensor 31 and the stress-strain sensor 32 is shown in Figures 5(b) and 5(c). The real-time monitoring of temperature, stress, and strain during the pyrolysis reaction of oil-rich coal is achieved by the fiber optic temperature sensor 31 and the stress-strain sensor 32 arranged inside the oil-rich coal sample 1.

[0062] In one embodiment, the fiber optic temperature sensor 31 and stress-strain sensor 32 are arranged as follows: Four holes are evenly arranged in a ring shape with a radius of 44 mm around the channel at the top of the sample; eight holes are evenly arranged in a ring shape with radii of 88 mm, 177 mm, and 221 mm; and six holes are evenly arranged in a ring shape with a radius of 265 mm, for a total of 34 vertical holes, which serve as fiber optic temperature measurement holes 33 and stress-strain measurement holes 34, respectively. Seventeen optical fibers connecting the fiber optic temperature sensors and seventeen optical fibers connecting the stress-strain sensors are inserted into the openings and bonded to the borehole walls with adhesive. The connecting wires are sealed and reinforced before being led out. Each optical fiber is equipped with seven sensors, for a total of 238 sensors, with a vertical spacing of 45 mm between the sensors.

[0063] It is used to achieve real-time monitoring of temperature, stress, and strain during the pyrolysis reaction of oil-rich coal.

[0064] The physical simulation experimental method for large-size in-situ pyrolysis mining of oil-rich coal according to an embodiment of the present invention comprises the following steps:

[0065] 1. Preparations before the experiment:

[0066] 1) Preparation of oil-rich coal samples

[0067] Prepare an oil-rich coal sample 1 with dimensions of 620×470×360mm. Grind the top of the coal sample flat and arrange a vertical drill hole with a diameter of 20mm and a depth of 360mm at the center of the top. Place the controllable shock wave action end 16, which is wrapped by the protective sleeve 15, at a position 246mm away from the top.

[0068] Grind the bottom of the sample flat, and with the vertical hole at the top as the center, evenly arrange six hexagonal holes with a diameter of 30mm, a depth of 300mm, and a spacing of 135mm. These holes are used to place the pyrolysis product collection well 35 for pyrolysis product collection.

[0069] Thirty-four vertical holes, each 4 mm in diameter and 360 mm deep, are arranged at the top of the sample with the channel as the center. Seventeen optical fibers connecting to temperature sensor 31 and seventeen optical fibers connecting to stress-strain sensor 32 are wrapped in insulating, heat-resistant, and heat-resistant armor and inserted into the holes. The optical fibers are then bonded to the hole walls with adhesive, and the connecting wires are sealed and reinforced before being led out. The fiber optic temperature sensor 31 has a fiber diameter of 1.2 mm, a temperature measurement range of 100℃ to 800℃, and a temperature resolution of 0.1℃. The stress-strain sensor 32 has a measurement range of 0 to 700 με, and is used to monitor the temperature and strain changes at different locations of the coal sample in real time during pyrolysis.

[0070] Special vacuum grease was applied to both ends of the oil-rich coal sample 1. An ultrasonic excitation transducer 19 was placed in the center of the left end of the oil-rich coal sample 1, and an ultrasonic receiving transducer 20 was placed in the center of the right end of the sample. This was used to monitor the changes in the development of horizontal and vertical cracks inside the coal sample under the action of a controllable shock wave, and to provide a detailed description of the cracks.

[0071] 2) Sealing of oil-rich coal samples and experimental chamber

[0072] The prepared oil-rich coal sample 1 was wrapped in a sealing colloid and placed into the experimental chamber 3. A 60mm heat insulation layer was arranged between the sample and the chamber wall. The experimental chamber 3 was placed in the reaction vessel body 2.

[0073] At the top of the sample, the shock wave action end 16 is connected to the power control line 13 outside the reactor body through the channel 17 arranged on the heat insulation layer 4, the experimental chamber 3, and the reactor body 2. The aperture of the channel 17 is 20mm.

[0074] The armored optical cable connectors connecting the optical fiber temperature sensor 31 and the stress strain sensor 32 pass through 34 holes with a diameter of 4 mm pre-set on the surface of the experimental chamber 3 and are connected to the optical fiber temperature testing system 29 and the stress strain testing system 30 outside the reactor.

[0075] The ultrasonic excitation transducer 19 and the ultrasonic receiving transducer 20 are connected to the high-frequency high-voltage amplifier 21 outside the reactor body via connecting lines; the pyrolysis product collection well 35 is connected to the pyrolysis oil and gas collection and separation system 49 outside the reactor body.

[0076] Ensure that experimental chamber 3 is sealed to the joint and isolated from the geostress simulation medium.

[0077] 3) Inspection: All valves, pumps and sealing flanges 14 in the system are closed and a sealing check is performed.

[0078] 2. Simulation test process:

[0079] 4) Deep geostress environment simulation

[0080] ① Open the valve of nitrogen cylinder group 5 to introduce nitrogen into the booster pump 6 to pressurize the nitrogen. Open the valve of air compressor 7 to provide power to booster pump 6 and introduce the pressurized nitrogen into cooling system 8. High-pressure nitrogen is then introduced into reactor body 2 through gas injection pump 9.

[0081] ② Open the exhaust port 10 valve to allow the original air in the reactor body 2 to be discharged from the test device through the exhaust port 10. Monitor the pressure gauge on the valve to ensure that all the original air in the reactor body 2 has been discharged, and then close the exhaust port 10 valve.

[0082] ③ By filling the reactor body 2 with high-pressure nitrogen, a confining pressure is applied to the oil-rich coal sample 1; the confining pressure is monitored by a pressure sensor installed on the reactor body 2, and once the applied confining pressure reaches a predetermined value, the gas injection pump 9 is turned off and the nitrogen filling is stopped.

[0083] 5) Oil-rich coal causes cracking

[0084] The motor 12 is started, and the power control line 13 is connected to the shock wave action end 16 to perform pre-fracturing on the oil-rich coal sample 1 in the experimental chamber 3. The waveform data output by the oscilloscope 22 is monitored in real time. The output data is collected and processed by the computer control system 23 to analyze the development status of horizontal and vertical fractures inside the oil-rich coal sample 1. The controllable shock wave action parameters are adjusted in a timely manner. Once a fracture network is formed inside the oil-rich coal sample 1, the motor 12 is turned off, and the artificial controllable fracturing of the coal seam is completed.

[0085] 6) Release nitrogen through exhaust port 10, gradually reduce the confining pressure to normal atmospheric pressure, remove ultrasonic excitation transducer 19 and ultrasonic receiving transducer 20, and end ultrasonic testing; open sealing flange 14 and remove shock wave action end 16, put high temperature water steam injection well 28 into the oil-rich coal sample 1 through the top channel 17 of the reactor body for high temperature water steam injection to stimulate the pyrolysis reaction of the coal sample to precipitate coal tar and pyrolysis gas; high temperature water steam injection well 28 passes through the channel 17 arranged on the heat insulation layer 4, experimental chamber 3, and reactor body 2 and is connected to the heat transfer fluid injection system 46 outside the reactor body.

[0086] 7) Check: All valves and pumps are closed, and the sealing flange 14 is sealed to ensure that all pipelines are airtight and watertight;

[0087] 8) Start the deep geostress loading system 101, turn on the gas injection pump 9, and apply confining pressure step by step to the predetermined load. Monitor the confining pressure through pressure sensors installed on the injection pump and the reactor body 2.

[0088] 9) High-temperature steam injection

[0089] ① Open the valve of water container 24, and the water in water container 24 enters steam generator 26 through liquid injection pump 25; turn on steam generator 26 to heat water and generate high temperature steam, and inject high temperature steam into the internal fracture network of oil-rich coal sample 1 through high temperature steam injection well 28 to stimulate the pyrolysis reaction of oil-rich coal sample 1; and monitor the temperature and pressure in the pipeline in real time through temperature gauge and pressure sensor installed on injection well, so that high temperature steam is injected into the fracture network of sample according to the experimental requirements.

[0090] ② By using fiber optic temperature sensor 31 and stress-strain sensor 32 pre-arranged inside the sample and fiber optic temperature testing system 29 and stress-strain testing system 30 outside the experimental chamber 3, the temperature and strain at different locations inside the sample are monitored in real time, and the temperature field variation law of oil-rich coal sample 1 is analyzed to evaluate the heat transfer effect and pyrolysis reaction range.

[0091] 10) Separation and collection of pyrolysis products

[0092] ① During the high-temperature pyrolysis process, pyrolysis oil and gas products are continuously released. The pyrolysis oil and gas enter the gas-liquid separator 36 through the pyrolysis product collection well 35. The temperature inside the pipeline is monitored by the temperature gauges on the collection well and valve to prevent the oil and gas from solidifying and blocking the pipeline. The gas flow rate value measured by the dial inside the gas-liquid separator 36 is monitored and recorded.

[0093] ② Tar flows from the gas-liquid separator 36 into the sampling bottle 37. The tar yield of the pyrolysis reaction is calculated by weighing the amount of tar in the sampling bottle 37. The pyrolysis gas is passed into the filter 38 to filter out impurities such as ash. After being dried by the dryer 39, the pyrolysis gas is passed into the gas chromatograph 40. Using the gas flow rate measured in the gas-liquid separator 36, the gas chromatograph 40 and the computer acquisition system 41 determine the composition and content of the pyrolysis gas of the oil-rich coal sample 1 in the experimental chamber 3, analyze the pyrolysis reaction stages at different locations of the oil-rich coal sample 1, and evaluate the pyrolysis effect.

[0094] ③ After the pyrolysis gas analysis is completed, the pyrolysis gas is discharged through the exhaust port 10; open the valve to introduce high-temperature water vapor into the cooling port 27 for cooling.

[0095] 11) Repeated trials

[0096] Modify the test parameters and repeat steps 3) to 10) until the physical simulation experiment of in-situ pyrolysis mining of oil-rich coal under different stress states and different heat injection methods is completed.

[0097] This invention is not limited to the above embodiments. Based on the technical solutions disclosed in this invention, those skilled in the art can make some substitutions and modifications to some of the technical features without creative effort, and all such substitutions and modifications are within the protection scope of this invention.

Claims

1. A physical simulation experimental method for large-scale in-situ pyrolysis mining of oil-rich coal, characterized in that, The simulation experimental apparatus used in the method includes: The deep geostress loading system applies confining pressure to the oil-rich coal sample inside the experimental chamber of the reactor body. The heat transfer fluid injection system is used to inject high-temperature heat transfer fluid into the oil-rich coal sample in the experimental chamber of the reactor to activate the pyrolysis reaction of the oil-rich coal. A controllable shock wave fracturing system is used to apply shock wave fracturing to oil-rich coal samples in the experimental chamber of a reactor. Ultrasonic testing system for detecting fracture development information in oil-rich coal samples before and after fracturing; Fiber optic temperature-stress-strain sensing system for distributed fiber optic stress-strain testing; The pyrolysis oil and gas collection and separation system monitors the temperature, strain, and pyrolysis oil and gas migration parameters of the oil-rich coal in the reactor in real time during the pyrolysis process, and evaluates the effect of in-situ pyrolysis of oil-rich coal. The simulation experiment method includes: A controllable shock wave and a high-temperature steam injection well were placed at the top of the oil-rich coal sample, and a pyrolysis product collection well was placed at the bottom of the coal sample. An optical fiber connecting a fiber temperature sensor and a stress strain sensor is inserted into an oil-rich coal sample. An ultrasonic excitation transducer and an ultrasonic receiving transducer are respectively arranged on both sides of the oil-rich coal sample. The oil-rich coal sample was sealed and placed into the experimental chamber with a heat insulation layer, and the armored optical cable connector was sealed and connected to the connector outside the reactor body. High-pressure nitrogen gas is introduced into the reactor body, and confining pressure is applied step by step to the predetermined load through the deep in-situ stress loading system; The controllable shock wave fracturing system was activated to pre-fracture the oil-rich coal sample in the experimental chamber. The ultrasonic oscilloscope monitored the fracture development status at different locations of the oil-rich coal sample in real time, so that a horizontal and vertical fracture network was formed inside the sample. Nitrogen gas is released through the exhaust port, and the confining pressure is gradually reduced to normal atmospheric pressure to end the ultrasonic testing. The deep geostress loading system is activated to apply confining pressure step by step to the predetermined load, and the confining pressure is monitored by pressure sensors on the reactor body. Start the heat transfer fluid injection system and inject high-temperature water vapor into the oil-rich coal sample in the experimental chamber at a certain pressure and temperature to stimulate the pyrolysis reaction of the oil-rich coal. The deep geostress loading system, the controllable shock wave fracturing system, and the heat transfer fluid injection system are independent of each other; Fiber optic temperature sensors and stress-strain sensors are used to monitor the temperature, stress, and strain characteristics of oil-rich coal samples at different locations during pyrolysis in real time. The temperature field variation of the oil-rich coal samples is compared and analyzed to evaluate the heat transfer effect and the pyrolysis reaction range. The pyrolysis oil and gas collection and separation system was started to collect and measure the composition and content of pyrolysis gas of oil-rich coal samples in the experimental chamber, compare and determine the pyrolysis reaction stages at different locations of oil-rich coal, and evaluate the pyrolysis effect of oil-rich coal samples. Modify the test parameters and repeatedly start the deep geostress loading system-controllable shock wave fracturing system-deep geostress loading system-heat transfer fluid injection system until the physical simulation experiment of in-situ pyrolysis mining of oil-rich coal under different stress states and different heat injection methods is completed.

2. The physical simulation experimental method for large-scale in-situ pyrolysis mining of oil-rich coal according to claim 1, characterized in that, The reactor body is a cylindrical steel structure, and a cuboid experimental chamber is set inside the steel structure. A heat insulation layer is arranged between the walls of the experimental chamber, and the experimental chamber contains an oil-rich coal sample wrapped with a sealing colloid. The experimental chamber is equipped with a channel connecting the heat transfer fluid injection system and the controllable shock wave fracturing system.

3. The physical simulation experimental method for large-scale in-situ pyrolysis mining of oil-rich coal according to claim 1, characterized in that, The deep geostress loading system includes a nitrogen cylinder group, a booster pump, and a cooling system connected in sequence. The air compressor is connected to the booster pump, and the gas injection pump is connected to the cooling system.

4. The physical simulation experimental method for large-scale in-situ pyrolysis mining of oil-rich coal according to claim 1, characterized in that, The fiber optic temperature-stress-strain sensing system includes a fiber optic temperature sensor and a stress-strain sensor arranged inside an oil-rich coal sample. The fiber optic temperature sensor and the stress-strain sensor are connected to the fiber optic temperature testing system and the stress-strain testing system respectively via insulated, heat-resistant, and armored optical cables.

5. The physical simulation experimental method for large-scale in-situ pyrolysis mining of oil-rich coal according to claim 1, characterized in that, High-temperature steam injection wells and pyrolysis product collection wells, as well as fiber optic temperature measurement holes and stress-strain measurement holes, were arranged in the oil-rich coal sample in the experimental chamber.

6. The physical simulation experimental method for large-scale in-situ pyrolysis mining of oil-rich coal according to claim 5, characterized in that, The heat transfer fluid injection system includes a water container, a liquid injection pump and a steam generator connected in sequence. The steam generator is connected to a high-temperature steam injection well to the interior of the oil-rich coal sample in the experimental chamber. The steam generator is connected to a cooling port on the pipeline.

7. The physical simulation experimental method for large-scale in-situ pyrolysis mining of oil-rich coal according to claim 1, characterized in that, The pyrolysis oil and gas collection and separation system includes a gas-liquid separator, a filter, a dryer, a gas chromatograph, and a computer acquisition system connected in sequence; a sampling bottle is connected to the gas-liquid separator.

8. The physical simulation experimental method for large-scale in-situ pyrolysis mining of oil-rich coal according to claim 1, characterized in that, The controllable shock wave fracturing system includes a motor, which is connected to the shock wave action end placed inside the oil-rich coal sample via a power control line and channel.

9. The physical simulation experimental method for large-scale in-situ pyrolysis mining of oil-rich coal according to claim 1, characterized in that, The ultrasonic testing system includes ultrasonic excitation transducers and ultrasonic receiving transducers arranged on both sides of the oil-rich coal sample. The ultrasonic excitation transducers and ultrasonic receiving transducers are connected to a waveform generator, which is connected in sequence to a high-frequency high-voltage amplifier, an oscilloscope, and a computer control system.

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