Deep coal seam and geothermal resource combined mining method

Abstract

The invention discloses a deep coal seam and geothermal resource combined mining method which comprises the following steps: S1, sample preparation: mixing different rock powders according to a particle size ratio, and pressing into a rock test piece; s2, preparing the device; loading the processed rock test piece into a supporting sleeve, then loading the supporting sleeve into a clamping structure, sealing through a sealing structure, then connecting an injection system and a temperature monitoring system with the clamping structure, and setting test conditions; s3, starting a test, injecting a fluid into the sample through an injection system to complete the test, and recording the temperature change condition of the test piece in the whole test process and the temperature change condition of the fluid flowing through the test piece at the same time; s4, repeating the test, respectively changing the proportion of the rock test piece, the heating temperature of the test piece, the injection pressure and the water injection rate, repeating the test, obtaining a heat exchange change rule in the hot dry rock mining process through comparison, simulating the coal seam water injection process through an indoor test, and analyzing the prevention and control effect of coal seam water injection by changing the water injection condition. And a basis is provided for improving the heat exchange efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of geothermal energy resource exploitation, and particularly relates to a method for jointly exploiting deep coal seams and geothermal resources. Background Technique

[0002] Geothermal resources are renewable clean energies that are key research and development focuses in various countries around the world. High-temperature geothermal resources mainly include hydrothermal and hot dry rock types. Hot dry rock is a hot rock mass that contains little or no water or steam, mainly various metamorphic or crystalline rock masses. Common rocks include biotite gneiss, granite, granodiorite, etc.

[0003] The exploitation process of hot dry rock involves complex physical, chemical, and mechanical processes, especially the interaction and coupling among multiple fields (temperature field, stress field, seepage field, chemical field), which have a significant impact on exploitation efficiency, system stability, and environmental impact. In the in-situ heat exchange exploitation technology of different working fluids and hot dry rock, the heat exchange mechanism and heat exchange efficiency have an important impact on improving the utilization rate of hot dry rock. Summary of the Invention

[0004] The present invention intends to provide a method for jointly exploiting deep coal seams and geothermal resources, and simulate the heat exchange variation law during the in-situ hot dry rock exploitation process through indoor experiments, so as to provide a basis for how to improve the heat exchange efficiency.

[0005] To this end, the technical solution adopted by the present invention is as follows: A method for jointly exploiting deep coal seams and geothermal resources, comprising the following steps:

[0006] S1: Specimen preparation. Crush and grind different types of rocks to the required particle size range, screen and dry the ground rock powder through a vibrating sieve for standby. Mix the rock powder according to the particle size ratio requirements, add a rock powder binder in proportion and stir evenly, and load the rock powder into a mold to press into a cylindrical rock specimen.

[0007] S2: Equipment preparation. Load the processed rock specimen into a support sleeve, and sleeved a confining pressure sleeve outside the support sleeve. Then place the support sleeve into a clamping structure and seal it through a sealing structure. Then connect the injection system, temperature monitoring system with the clamping structure, set the temperature of the heating component for heating the specimen, and apply axial pressure and confining pressure to the specimen according to the test requirements.

[0008] S3: Start the experiment. Inject the fluid into the specimen through the injection system to complete the experiment, and record the temperature change of the specimen during the whole process of the experiment, as well as the temperature change of the fluid flowing through the specimen.

[0009] S4: Repeat the experiment. After separately changing the ratio of the rock specimen, the heating temperature of the specimen, the injection pressure, and the water injection rate, repeat the experiment and record the temperature change of the specimen during the whole process under different conditions. Through comparison, obtain the heat transfer change law during the dry hot rock exploitation process.

[0010] As an optimization of the above solution, the clamping structure includes a mounting plate and a ductile specimen tube which is arranged with upper and lower through holes. A pressurization system for realizing triaxial pressurization of the specimen is arranged on the clamping structure. The pressurization system includes an annular pressure sleeve arranged between the specimen tube and the support sleeve, and an axial pressure mounting plate arranged below the mounting plate through a connecting column. The annular pressure sleeve is equipped with an annular pressure tracking system, and an axial pressure cylinder is arranged on the axial pressure mounting plate.

[0011] Further preferably, the sealing structure includes floating plugs arranged at the upper and lower ends of the specimen tube. Between each floating plug and the specimen tube, multiple high-temperature gaskets and a double-V-shaped combined graphite component are sequentially arranged from inside to outside. On the end of each floating plug, a bolt pre-tightening and pressing structure for ensuring reliable sealing of the sealing structure is arranged. An outlet for fluid injection or an inlet communicated with the injection system is arranged in the floating plug, and the outlet and the inlet are respectively arranged in different floating plugs.

[0012] Further preferably, the bolt pre-tightening and pressing structure includes an upper bolt pre-tightening and pressing structure and a lower bolt pre-tightening and pressing structure corresponding to the upper and lower floating plugs. The upper bolt pre-tightening and pressing structure includes a first flange sleeved on the upper end of the specimen tube and a second flange sleeved on the upper end of the upper floating plug. The first flange and the second flange are connected by mounting bolts. At a position near the upper end of the floating plug, a T-shaped upper pressing block is arranged, and the lower end of the upper pressing block can be inserted into the upper end of the specimen tube. A lower notch for the upper pressing block to be inserted into is arranged at the lower end of the second flange, and an upper pressing bolt capable of pressing on the upper pressing block is arranged on the second flange.

[0013] The lower bolt pre-tightening and pressing structure includes a third flange sleeved on the lower end of the specimen tube and a fourth flange sleeved at a position near the lower end of the lower floating plug. The third flange is arranged on the mounting plate located at its lower end, the upper end of the fourth flange is located inside the mounting plate, and at a position near the lower end of the lower floating plug, a T-shaped lower pressing block is arranged, and the upper end of the lower pressing block can be inserted into the lower end of the specimen tube. An upper notch for the lower pressing block to be inserted into is arranged at the upper end of the fourth flange, and a lower pressing bolt capable of pressing on the lower pressing block is arranged on the fourth flange.

[0014] Further preferably, the mounting disc is arranged on the flipping assembly, the flipping assembly includes a flipping bracket, both ends of the mounting disc are horizontally provided with flipping shafts, the other ends of the flipping shafts are rotatably arranged on the flipping seats, the flipping seats are arranged on the flipping bracket, and a traveling mechanism for driving the whole flipping assembly to move and fix the position after moving is arranged at the bottom of the flipping bracket.

[0015] Further preferably, the injection system includes a storage container for containing fluid and a constant-pressure pump for realizing the flow of the fluid. The storage container and the constant-pressure pump are sequentially connected through an injection pipeline, and a monitoring structure for monitoring its pressure is arranged on the injection pipeline.

[0016] Further preferably, the temperature monitoring system includes a plurality of temperature monitoring sensors. The temperature monitoring sensors are arranged in at least two rows, and at least four temperature monitoring sensors are arranged in each row in different directions. The temperature monitoring sensors pass through the specimen tube and then contact the specimen. The temperature monitoring sensors are arranged on a sensor bracket, and the sensor bracket is arranged on the mounting disc.

[0017] Further preferably, the heating assembly includes a heating tile sleeved outside the specimen tube, and a heat preservation sleeve is arranged outside the heating tile.

[0018] The beneficial effects of the present invention: It can simulate the heat exchange test under the conditions of confining pressure and axial pressure. By changing the ratio of rock specimens, the heating temperature of the specimens, the injection pressure and the water injection rate, repeating the test, and analyzing, the heat exchange change law in the process of dry hot rock exploitation can be obtained, providing a basis for improving the utilization efficiency of dry hot rock. Description of the Drawings

[0019] Figure 1 It is a schematic flow chart of the present invention.

[0020] Figure 2 It is a schematic diagram of the test device used in the present invention.

[0021] Figure 3 It is a schematic diagram of the clamping structure in the present invention.

[0022] Figure 4 It is a three-dimensional schematic diagram of the clamping structure in the present invention.

[0023] Figure 5 It is a schematic diagram of the clamping structure and the flipping assembly in the present invention.

[0024] Reference numerals: inlet - 1, outlet - 2, specimen tube - 3, mounting plate - 4, support sleeve - 5, floating plug - 6, high - temperature gasket - 7, graphite component - 8, inlet - equipped - 9, first flange - 10, second flange - 11, upper top block - 12, upper tightening bolt - 13, third flange - 14, fourth flange - 15, lower top block - 16, heating tile - 17, heat - insulating sleeve - 18, high - temperature ring - pressing sleeve - 20, connecting column - 21, axial - pressure mounting plate - 22, axial - pressure cylinder - 23, cooling sleeve - 24, temperature - monitoring sensor - 25, sensor support - 27, detection plate - 28, flipping bracket - 29, flipping shaft - 30, flipping seat - 31, traveling mechanism - 32, storage container - 33, constant - pressure pump - 34, lower tightening bolt - 45. Detailed implementation mode

[0025] The present invention will be further described below with reference to embodiments and the accompanying drawings:

[0026] As Figures 1-5 shown, a method for jointly exploiting deep - coal seams and geothermal resources includes the following steps:

[0027] The first step is specimen preparation. Crush and grind different types of rocks to the required particle - size range, screen and dry the ground rock powder through a vibrating sieve for standby, mix the rock powder according to the particle - size ratio requirements, add a rock - powder binder in proportion and stir evenly, and load the rock powder into a mold to press it into a cylindrical rock specimen.

[0028] The second step is device assembly. Load the processed rock specimen into the support sleeve, sleeved with a ring - pressing sleeve outside the support sleeve, then load the support sleeve into the clamping structure and seal it through the sealing structure, and then connect the injection system, temperature - monitoring system with the clamping structure, set the temperature of the heating component for heating the specimen, and apply axial pressure and confining pressure to the specimen according to the test requirements.

[0029] The clamping assembly includes a mounting plate 4 and an extensible specimen tube 3, and the specimen tube 3 is arranged to penetrate through up and down. Preferably, the specimen tube and the support sleeve are made of nickel - based alloy materials, specifically high - temperature aviation materials, such as imported alloy 718 or domestic material 4169. It has high temperature, high - pressure and corrosion resistance, does not deform after repeated use, still has high strength under high temperature and high pressure, and even under the high - temperature condition of 800 °C, the tensile strength still reaches 1500 N / mm 2 , the yield strength reaches 800 N / mm 2 , and the elongation rate can reach more than 30%.

[0030] A pressurization system for realizing axial compression and confining pressure pressurization of the specimen to simulate the surrounding environment of the coal body is provided on the clamping structure. The pressurization system includes a confining pressure sleeve 20 arranged between the specimen tube 3 and the support sleeve 5, and an axial pressure mounting plate 22 arranged below the mounting disc 4 through a connecting column 21. The confining pressure sleeve 20 is equipped with a confining pressure tracking system, and an axial pressure cylinder 23 is arranged on the axial pressure mounting plate 22.

[0031] Preferably, the confining pressure tracking system includes a confining pressure tracking pump and a confining pressure tracking pipeline communicated with the confining pressure sleeve. The confining pressure tracking pump is equipped with a control panel, a safety pressure relief function, etc., and can realize differential pressure tracking, automatic pressure lifting and lowering, display of pressure data, feedback system, etc. through a control terminal; it has a manual control function for pressure lifting and lowering.

[0032] Preferably, a heating assembly for heating the rock specimen is arranged outside the specimen tube. The heating assembly includes a heating tile 17 sleeved outside the specimen tube 3. The heating tile is located between the first flange and the second flange. A heat preservation sleeve 18 is arranged outside the heating tile 17. The lower end of the heat preservation sleeve is arranged on the mounting disc, and the upper end of the heat preservation sleeve is located above the fourth flange. A dry-burning resistant electric heating tube can be inserted into the heating tile. To ensure the heating temperature, a temperature control thermocouple probe is installed at an appropriate position on the heating tile. At the same time, the temperature control instrument adopts an imported temperature control instrument with PID. The temperature control range is: room temperature - 999°C, and the temperature control accuracy is ±0.5°C. The heat preservation sleeve is heat-insulated by an imported high-efficiency STP heat-insulation layer and is externally provided with a stainless steel decorative outer sleeve to ensure that the temperature of the exposed parts is controlled below 30°C.

[0033] The sealing structure includes floating plugs 6 arranged at the upper and lower ends of the specimen tube 3. Between each floating plug 6 and the specimen tube 3, multiple high-temperature gaskets 7 and double V-shaped combined graphite components 8 are sequentially arranged from inside to outside. When the internal pressure extrudes outwards, the self-sealing rubber ring deforms, making its outer diameter fit more closely with the specimen tube and its inner diameter fit more closely with the confining pressure sleeve, thereby realizing reliable sealing. An inlet 1 and an outlet 2 for realizing the inflow and outflow of fluid are arranged on the floating plug 6, and the inlet 1 and the outlet 2 are arranged on different floating plugs. Preferably, a spare inlet 9 is arranged on the floating plug where the outlet is located.

[0034] Preferably, the high-temperature gasket material is an imported ultra-high temperature material from the United States. It has good elasticity even at 1000°C and can be used for frequent loading and unloading. It can be arbitrarily stamped into a formed sealing gasket. The double V-shaped combined graphite component is used as the sealing component, which has the characteristics of reliable sealing and convenient loading and unloading. At the same time, it plays a role in blocking the boundary cross-flow between the confining pressure sleeve and the core sample and eliminating the boundary effect.

[0035] To ensure the reliable sealing of the sealing structure, a bolt pre-tightening and pressing structure for ensuring the reliable sealing of the sealing structure is provided at the end of each floating plug 6. The bolt pre-tightening and pressing structure includes an upper bolt pre-tightening and pressing structure and a lower bolt pre-tightening and pressing structure arranged up and down. That is, the upper bolt pre-tightening and pressing structure is used to lock the upper floating plug, and the lower bolt pre-tightening and pressing structure is used to lock the lower floating plug.

[0036] The upper bolt pre-tightening and pressing structure includes a first flange 10 sleeved on the upper end of the sample tube 3 and a second flange 11 sleeved on the upper end of the upper floating plug 6. The first flange 10 and the second flange 11 are connected by mounting bolts. At a position near the upper end of the floating plug 6, a T-shaped upper top block 12 is provided, and the lower end of the upper top block 12 can be inserted into the upper end of the sample tube 3. At the lower end of the second flange 11, a lower notch for the upper top block 12 to be inserted into is provided, and an upper tightening bolt 13 that can press on the upper top block 12 is provided on the second flange 11.

[0037] The lower bolt pre-tightening and pressing structure includes a third flange 14 sleeved on the lower end of the sample tube 3 and a fourth flange 15 sleeved at a position near the lower end of the lower floating plug 6. The third flange 14 is arranged on the mounting plate 4 located at its lower end, and the upper end of the fourth flange 15 is inside the mounting plate 4. At a position near the lower end of the lower floating plug 6, a T-shaped lower top block 16 is provided, and the upper end of the lower top block 16 can be inserted into the lower end of the sample tube 3. At the upper end of the fourth flange 15, an upper notch for the lower top block 16 to be inserted into is provided, and a lower tightening bolt 45 that can press on the lower top block 16 is provided on the fourth flange 15.

[0038] The sealing structure is tightened by multiple tightening bolts and top blocks to prevent the outward movement of the sealing structure when the internal pressure rises. Preferably, the screws are made of high-strength heat-resistant materials and will not produce sticking phenomena at high temperatures.

[0039] To achieve horizontal and vertical flipping, the mounting plate 4 is arranged on the flipping assembly. The flipping assembly includes a flipping bracket 29. At both ends of the mounting plate 4, rotating shafts 30 are horizontally arranged, and the other ends of the rotating shafts 30 are rotatably arranged on the flipping seats 31. The flipping seats 31 are arranged on the flipping bracket 29. At the bottom of the flipping bracket 29, a traveling mechanism 32 for driving the entire flipping assembly to move and fixing the position after movement is provided.

[0040] The injection system includes a storage container 33 for containing fluid and a constant-pressure pump 34 for realizing the flow of fluid, and the storage container 33 and the constant-pressure pump 34 are sequentially connected through an injection pipeline. A control valve 38, a pressure gauge for monitoring its pressure, and a thermometer for monitoring temperature are provided on the injection pipeline.

[0041] The temperature monitoring system includes several temperature monitoring sensors 25. The temperature monitoring sensors 25 are arranged in at least two rows, and at least four temperature monitoring sensors 25 are arranged in different directions in each row. The temperature monitoring sensors 25 pass through the specimen tube 3 and contact the specimen. A sealing ring and a gasket are arranged between the temperature monitoring sensors and the specimen tube. The temperature monitoring sensors 25 are arranged on the sensor bracket 27, and the sensor bracket 27 is arranged on the mounting plate 4.

[0042] At the outlet, it is connected to the collection container through a collection pipeline, and a thermometer is arranged on the collection pipeline.

[0043] In the third step, start the test. Inject the fluid into the specimen through the injection system to complete the test. At the same time, record the temperature change of the specimen during the whole test process and the temperature change of the fluid after flowing through the specimen, and obtain the curve graph of the specimen temperature and the injection time.

[0044] In the fourth step, repeat the test. After changing the ratio of the rock specimen, the heating temperature of the specimen, the injection pressure, and the water injection rate respectively, record the temperature change of the specimen during the whole test process and the temperature change of the fluid after flowing through the specimen under different conditions. By comparison, obtain the heat exchange change law during the dry hot rock mining process, and provide a basis for improving the heat exchange efficiency of dry hot rock.

Claims

1. A method for jointly exploiting deep coal seams and geothermal resources, characterized in that, It includes the following steps: S1: Specimen preparation. Crush and grind different types of rocks to the required particle size range, sieve and dry the ground rock powder through a vibrating sieve for standby. Mix the rock powder according to the particle size ratio requirements, add a rock powder binder in proportion and stir evenly. Load the rock powder into a mold and press it into a cylindrical rock specimen. S2: Equipment preparation. Load the processed rock specimen into the support sleeve, and set a circumferential pressure sleeve outside the support sleeve. Then install the support sleeve into the clamping structure and seal it through the sealing structure. Connect the injection system, temperature monitoring system to the clamping structure, set the temperature of the heating component for heating the specimen, and apply axial pressure and confining pressure to the specimen according to the test requirements. S3: Start the test. Inject fluid into the specimen through the injection system to complete the test. At the same time, record the temperature change of the specimen during the whole test process and the temperature change of the fluid after flowing through the specimen. S4: Repeat the test. After changing the ratio of the rock specimen, the heating temperature of the specimen, the injection pressure and the water injection rate respectively, repeat the test, and record the temperature change of the specimen during the whole test process under different conditions and the temperature change of the fluid after flowing through the specimen. Obtain the heat exchange change law during the dry hot rock exploitation process through comparison.

2. The combined mining method of deep coal seam and geothermal resources according to claim 1, characterized in that: The clamping structure includes a mounting plate (4) and a ductile specimen tube (3). The specimen tube (3) is arranged with upper and lower through holes. A pressurization system for realizing axial pressure and confining pressure pressurization of the specimen is arranged on the clamping structure. The pressurization system includes a circumferential pressure sleeve (20) arranged between the specimen tube (3) and the support sleeve (5) and an axial pressure mounting plate (22) arranged below the mounting plate (4) through a connecting column (21). The circumferential pressure sleeve (20) is equipped with a circumferential pressure tracking system. An axial pressure cylinder (23) is arranged on the axial pressure mounting plate (22), and a cooling sleeve (24) with water inlet and outlet is arranged between the axial pressure cylinder (23) and the specimen tube (3).

3. The combined mining method of deep coal seam and geothermal resources according to claim 2, characterized in that: The sealing structure includes floating plugs (6) arranged at the upper and lower ends of the specimen tube (3). A multi-layer high-temperature gasket (7) and a double-V-shaped combined graphite component (8) are sequentially arranged between each floating plug (6) and the specimen tube (3) from inside to outside. A bolt pre-tightening and top-tightening structure for ensuring reliable sealing of the sealing structure is arranged at the end of each floating plug (6). An outlet (2) for fluid injection or an inlet (1) communicated with the injection system is arranged in the floating plug (6), and the outlet (2) and the inlet (1) are respectively arranged in different floating plugs (6).

4. The method for jointly exploiting deep coal seams and geothermal resources according to claim 3, characterized in that: The bolt pre-tightening and jacking structure includes an upper bolt pre-tightening and jacking structure and a lower bolt pre-tightening and jacking structure corresponding to the upper and lower floating plugs. The upper bolt pre-tightening and jacking structure includes a first flange (10) sleeved on the upper end of the specimen tube (3) and a second flange (11) sleeved on the upper end of the upper floating plug (6). The first flange (10) and the second flange (11) are connected by mounting bolts. At a position near the upper end of the floating plug (6), a T-shaped upper jacking block (12) is provided, and the lower end of the upper jacking block (12) can be inserted into the upper end of the specimen tube (3). A lower notch for the upper jacking block (12) to be inserted into is provided at the lower end of the second flange (11), and an upper jacking bolt (13) capable of pressing on the upper jacking block (12) is provided on the second flange (11). The lower bolt pre-tightening and jacking structure includes a third flange (14) sleeved on the lower end of the specimen tube (3) and a fourth flange (15) sleeved at a position near the lower end of the lower floating plug (6). The third flange (14) is arranged on the mounting plate (4) located at its lower end. The upper end of the fourth flange (15) is located inside the mounting plate (4). At a position near the lower end of the lower floating plug (6), a T-shaped lower jacking block (16) is provided, and the upper end of the lower jacking block (16) can be inserted into the lower end of the specimen tube (3). An upper notch for the lower jacking block (16) to be inserted into is provided at the upper end of the fourth flange (15), and a lower jacking bolt (45) capable of pressing on the lower jacking block (16) is provided on the fourth flange (15).

5. The method for combined exploitation of deep coal seams and geothermal resources according to claim 2, characterized in that: The mounting plate (4) is arranged on the flipping assembly. The flipping assembly includes a flipping bracket (29). Horizontal rotating shafts (30) are arranged at both ends of the mounting plate (4). The other ends of the rotating shafts (30) are rotatably arranged on the flipping seats (31). The flipping seats (31) are arranged on the flipping bracket (29). A traveling mechanism (32) for driving the entire flipping assembly to move and fix the position after movement is provided at the bottom of the flipping bracket (29).

6. The method for jointly exploiting deep coal seams and geothermal resources according to claim 1, characterized in that: The injection system includes a storage container (33) for containing fluid and a constant pressure pump (34) for realizing the flow of the fluid. The storage container (33) and the constant pressure pump (34) are sequentially connected through an injection pipeline, and a monitoring structure for monitoring its pressure and temperature is provided on the injection pipeline.

7. The method for jointly exploiting deep coal seams and geothermal resources according to claim 2, characterized in that: The temperature monitoring system includes a plurality of temperature monitoring sensors (25). The temperature monitoring sensors (25) are arranged in at least two rows, and at least four temperature monitoring sensors (25) are arranged in different directions in each row. The temperature monitoring sensors (25) pass through the specimen tube (3) and then contact the specimen. The temperature monitoring sensors (25) are arranged on the sensor bracket (27), and the sensor bracket (27) is arranged on the mounting plate (4).

8. The method for jointly exploiting deep coal seams and geothermal resources according to claim 2, characterized in that: The heating assembly includes a heating tile (17) sleeved outside the specimen tube (3), and a heat preservation sleeve (18) is arranged outside the heating tile (17).

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