An integrated utilization method for in-situ conversion of rich oil coal underground

Abstract

The present invention provides a comprehensive utilization method for in-situ conversion of rich oil coal underground, belonging to the technical field of unconventional energy. By forming a continuous grouting body in the coal seam section of the underground pyrolysis zone of rich oil coal, the hydraulic connection between the pyrolysis zone and the surrounding strata is blocked, solving the problem that the heating efficiency is affected by the intrusion of formation water during the in-situ conversion of rich oil coal underground, and at the same time preventing the diffusion of pyrolysis pollutants to the surrounding strata; by adding a resistivity regulator to the high-temperature resistant cement slurry, monitoring the diffusion form of the grouting body, and adjusting the grouting parameters in real time, precise control of the grouting body is achieved; by using horizontal wells and packers in combination, adjusting the proportion of oxygen and water in nitrogen, and making appropriate monthly adjustments to the operating parameters of the process according to the monthly profit curve, the economy of the entire project is improved, realizing the comprehensive utilization of rich oil coal, and solving the problems of heavy coal tar blocking the strata, low utilization rate of rich oil coal resources, and low yield rate when developing rich oil coal in the prior art.

Description

Technical Field

[0001] The present invention belongs to the technical field of unconventional energy, and particularly relates to a comprehensive utilization method for in-situ underground conversion of oil-rich coal. Background Art

[0002] Oil-rich coal is not only coal, but also a coal-based oil and gas resource. The in-situ underground conversion technology of oil-rich coal is an important direction for realizing the low-carbon development of high-carbon resources. It changes physical coal mining to chemical coal mining, underground coal mining to drilling coal mining, and coal mining to oil and gas extraction. It is an important means to realize the low-carbon, green, safe and efficient development of coal. Compared with the traditional underground mining and surface pyrolysis processes, it has the advantages of small floor area, less environmental pollution, small investment, high safety factor, and effectively solving the problems of deep resource utilization.

[0003] During the in-situ underground conversion of oil-rich coal, the free water in the coal seam will have a certain impact on the pyrolysis zone, mainly reflected in the problems of reduced thermal efficiency, difficult control of pollutant diffusion, low recovery rate of oil and gas products, high energy consumption, and low yield. Summary of the Invention

[0004] The purpose of the present invention is to provide a comprehensive utilization method for in-situ underground conversion of oil-rich coal to solve the problems mentioned in the background art.

[0005] To achieve the above object, in a first aspect, the present invention provides a comprehensive utilization method for in-situ underground conversion of oil-rich coal, including the following steps:

[0006] S1: Construct injection well 1, production well 1, injection well 2 and production well 2 above the coal seam roof in the oil-rich coal pyrolysis block. The lower ends of injection well 1, production well 1, injection well 2 and production well 2 are all drilled into the coal seam floor. Then, construct horizontal well 1 in the oil-rich coal pyrolysis block to connect injection well 1 and production well 1, construct horizontal well 2 in the oil-rich coal pyrolysis block to connect injection well 2 and production well 2. Finally, lower casings into injection well 1, production well 1, horizontal well 1, injection well 2, production well 2 and horizontal well 2 for cementing operations;

[0007] S2: Construct several grouting wells above the coal seam roof at the edge of the oil-rich coal pyrolysis block. The lower ends of the grouting wells are all drilled into the coal seam floor. The several grouting wells enclose the oil-rich coal pyrolysis block. After drilling, lower casings for cementing operations;

[0008] S3: Perform conventional perforation operations on all well sections. In the oil-rich coal pyrolysis block section, perform directional perforation between two adjacent grouting wells, injection well 1 and injection well 2, production well 1 and production well 2, horizontal well 1 and horizontal well 2;

[0009] S4: After perforation, perform fracture creation operations on all well sections;

[0010] S5: Conduct grouting operations on the grouting wells;

[0011] S6: Conduct in-situ pyrolysis operations after the grout has finally set.

[0012] Furthermore, before step S4, install the wellheads of injection heat well 1, injection heat well 2, production well 1, and production well 2, and install annulus valves on each wellhead.

[0013] Furthermore, step S4 specifically includes the following steps:

[0014] S401: Fill each grouting well with water, successively lower a controllable shock wave device into each grouting well, and successively conduct fracture creation operations on the coal seam sections of each grouting well to connect the wells through the fractures. The fracture creation radius of each grouting well is not less than the spacing between adjacent grouting wells;

[0015] S402: After the fracture creation of the grouting wells is completed, fill injection heat well 1, horizontal well 1, production well 1, injection heat well 2, horizontal well 2, and production well 2 with water, and successively conduct fracture creation operations on the rich oil coal pyrolysis block sections of injection heat well 1, production well 1, injection heat well 2, production well 2, and each point of horizontal well 1 and horizontal well 2;

[0016] S403: After the fracture creation operation is completed, conduct formation drainage operations.

[0017] Furthermore, before the start of grouting, demarcate a monitoring strip on the ground to monitor the spatial diffusion range of the grout. Use the high-density resistivity method to measure the initial resistivity data of the rich oil coal seam within the ground monitoring boundary line range, and adjust the resistivity of the grout according to the initial resistivity of the rich oil coal seam to increase the difference between the resistivity of the grout and the initial resistivity of the rich oil coal seam;

[0018] After the start of grouting, conduct high-density resistivity method monitoring on the formation, compare it with the initial resistivity of the rich oil coal seam in real time, infer the diffusion range of the grout, and adjust the grouting parameters according to the comparison data.

[0019] Furthermore, the formation drainage operation includes the following steps:

[0020] First, lower grouting pipes and gas injection pipes into each grouting well, injection heat well 1, injection heat well 2, production well 1, and production well 2. Then, inject pressurized air from injection heat well 1, injection heat well 2, production well 1, and production well 2. The water in the formation is discharged from each grouting well in turn, and then pressurized air is injected from each grouting well again. The water in the formation is discharged from injection heat well 1, injection heat well 2, production well 1, and production well 2 in turn.

[0021] Furthermore, step S6 specifically includes the following steps:

[0022] S601: Lower the first packer into the horizontal well 1 from the injection well 1, activate the first packer, then lower the downhole electric heater 1 into the injection well 1, connect the production pipe 1, the slotted pipe 1, and the second packer in sequence, and then lower the second packer to one end of the horizontal well 1 close to the injection well 1 and activate the second packer;

[0023] S602: Lower the third packer into the horizontal well 2 from the injection well 2, activate the third packer, then lower the downhole electric heater 2 into the injection well 2, connect the production pipe 2, the slotted pipe 2, and the fourth packer in sequence, and then lower the fourth packer to one end of the horizontal well 2 close to the injection well 2 and activate the fourth packer;

[0024] S603: Pyrolyze the rich oil coal block on the connection line between the injection well 1 and the production well 1, and transport the pyrolysis products to the ground through the production pipe 1;

[0025] S604: Pyrolyze the rich oil coal block on the connection line between the injection well 2 and the production well 2, and transport the pyrolysis products to the ground through the production pipe 2;

[0026] S605: Pyrolyze the rich oil coal block on the connection line between the injection well 1 and the production well 2, and transport the pyrolysis products to the ground through the production pipe 2;

[0027] S606: Pyrolyze the rich oil coal block on the connection line between the injection well 2 and the production well 1, and transport the pyrolysis products to the ground through the production pipe 1.

[0028] Further, the method further includes step S7: First, inject air into the injection well 1 and the injection well 2, activate the downhole electric heater 1 and the downhole electric heater 2 respectively, and ignite the pyrolyzed rich oil coal seam;

[0029] Then, monitor the combustion situation of the pyrolyzed coal seam through the product components of the production well 1 and the production well 2. When the coal seam is ignited, switch the air to a mixed gas, and the components of the mixed gas include O 2 , N 2 , H 2 O. The mixed gas reacts with the pyrolyzed rich oil coal seam to generate CO and H 2 . The generated gas is transported to the ground through the production pipe 1 and the production pipe 2.

[0030] Further, both the production pipe 1 and the production pipe 2 are heat-insulating pipes with heating functions.

[0031] Further, after the grouting stops, inject pressurized air into the injection well 1, the injection well 2, the production well 1, and the production well 2. The pressure of the pressurized air is greater than the initial pressure of the air in the well, which is used to prevent the slurry from flowing continuously after the grouting stops.

[0032] Further, during the second in-situ underground conversion, first calculate the monthly input cost in the in-situ underground conversion production process of rich oil coal, and calculate the monthly income in the in-situ underground conversion production process of rich oil coal according to the amount of pyrolysis products; then calculate the monthly profit in the in-situ underground conversion production process of rich oil coal based on the monthly input cost and the monthly income; finally, make monthly adjustments to the in-situ underground conversion process parameters according to the monthly profit in the in-situ underground conversion production process of rich oil coal.

[0033] The advantages of the present invention are as follows:

[0034] 1. The comprehensive utilization method of in-situ underground conversion of rich oil coal provided by the present invention forms a continuous grouting body in the coal seam section of the rich oil coal pyrolysis block, blocking the hydraulic connection between the pyrolysis zone and the surrounding strata, solving the problem that the heating efficiency is affected by the intrusion of formation water during the in-situ underground conversion of rich oil coal, and at the same time preventing the diffusion of pyrolysis pollutants to the surrounding strata.

[0035] 2. The comprehensive utilization method of in-situ underground conversion of rich oil coal provided by the present invention, through the combined use of horizontal wells and packers, can prevent heavy coal tar from blocking the formation and improve the recovery rate of pyrolysis products.

[0036] 3. The comprehensive utilization method of in-situ underground conversion of rich oil coal provided by the present invention, by alternately using grouting wells, heat injection wells, and production wells as pressurized air injection wells and drainage wells, can improve the displacement effect of formation water in the pyrolysis zone.

[0037] 4. The comprehensive utilization method of in-situ underground conversion of rich oil coal provided by the present invention reduces the energy consumption of the in-situ underground conversion process of rich oil coal by reacting oxygen with the pyrolyzed coal.

[0038] 5. The economic evaluation method provided by the present invention can conduct monthly evaluations on the economic benefits of the in-situ underground conversion method of rich oil coal, monitor the operation of the in-situ underground conversion method, and make appropriate monthly adjustments to the operation parameters of the process according to the monthly profit curve, improving the economy of the entire project.

[0039] The present invention will be described in detail below with reference to the accompanying drawings and embodiments. Brief Description of the Drawings

[0040] Figure 1 It is a schematic diagram of well position layout and direction of directional perforation.

[0041] Figure 2 It is the cross-sectional schematic diagram of the high-temperature fluid at B-B during the process operation in Figure 1 the

[0042] Figure 3 It is the cross-sectional schematic diagram of the grouting well at A-A in Figure 1 the

[0043] Figure 4 It is a schematic diagram of the monitoring strip.

[0044] Figure 5 It is a schematic diagram of the flow of the injected gas and pyrolysis products.

[0045] Explanation of the reference numerals in the drawings: 1. Rich oil coal pyrolysis block; 2. Coal seam roof; 3. Coal seam floor; 4. Production well 1; 5. Horizontal well 1; 6. Heat injection well 1; 7. Production well 2; 8. Horizontal well 2; 9. Heat injection well 2; 10. Gas injection pipe; 11. Annular space valve; 12. Downhole electric heater 1; 13. First packer; 14. Second packer; 15. Perforated pipe 1; 16. Production pipe 1; 17. Grouting well; 18. Monitoring strip. Specific implementation manners

[0046] In order to further elaborate on the technical means and effects adopted by the present invention to achieve the predetermined purpose, the specific implementation manners, structural features and their effects of the present invention will be described in detail below with reference to the drawings and embodiments.

[0047] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0048] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "aligned", "overlapped", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0049] The terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features; in the description of the present invention, unless otherwise specified, the meaning of "plurality" is two or more.

[0050] Embodiment 1

[0051] This embodiment provides a comprehensive utilization method for in-situ conversion of rich oil coal underground, as Figure 1As shown, first, according to the geological data of the rich oil coal pyrolysis block 1, determine the positions of the grouting well 17, the first heat injection well 6, the first production well 4, the second heat injection well 9 and the second production well 7, and then implement the following steps:

[0052] S1: As Figure 1 and Figure 2 shown, construct the first heat injection well 6, the first production well 4, the second heat injection well 9 and the second production well 7 above the coal seam roof 2 of the rich oil coal pyrolysis block 1. The lower ends of the first heat injection well 6, the first production well 4, the second heat injection well 9 and the second production well 7 are all drilled 5 meters into the coal seam floor 3. Then, construct the first horizontal well 5 in the rich oil coal pyrolysis block 1 to connect the first heat injection well 6 and the first production well 4, and construct the second horizontal well 8 in the rich oil coal pyrolysis block 1 to connect the second heat injection well 9 and the second production well 7. Preferably, the first horizontal well 5 and the horizontal well 5 are located in the middle of the rich oil coal pyrolysis block 1. The cross-sections of the first heat injection well 6, the first horizontal well 5 and the first production well 4, and the cross-sections of the second heat injection well 9, the second horizontal well 8 and the second production well 7 are all of H-shaped structure. Finally, lower the casing into the first heat injection well 6, the first production well 4, the first horizontal well 5, the second heat injection well 9, the second production well 7 and the second horizontal well 8 for cementing operation;

[0053] On the plane, the first heat injection well 6 and the second heat injection well 9 are arranged in the direction of the coal seam groundwater recharge source, and the distance between the first heat injection well 6 and the second heat injection well 9 is 40 meters.

[0054] The hole diameter of the heat injection well and the production well is 480mm. After drilling, a casing with a diameter of 298.5mm is lowered, and the cementing operation is completed; the hole diameter of the horizontal well is 185mm. After drilling, a casing with a diameter of 114.3mm is lowered, and the cementing operation is completed; the casing used is a high-temperature resistant casing.

[0055] S2: As Figure 1 and Figure 3 shown, construct several grouting wells 17 above the coal seam roof 2 at the edge of the rich oil coal pyrolysis block 1. The diameter of the grouting well 17 is 185mm, and the lower ends of the grouting wells 17 are all drilled 5 meters into the coal seam floor 3. The several grouting wells 17 enclose the rich oil coal pyrolysis block 1, and its shape is determined according to the rich oil coal pyrolysis block 1. After drilling, a casing with a diameter of 114.3mm is lowered for cementing operation;

[0056] Specifically, the hole diameter of the grouting well 17 is 185mm. After drilling, a casing with a diameter of 114.3mm is lowered, and the cementing operation is completed; the casing used is a high-temperature resistant casing.

[0057] After cementing, install the wellheads of the first heat injection well 6 and the second heat injection well 9, the first production well 4 and the second production well 7, and install the annulus valve 11 on each wellhead. A pressure sensor and a flowmeter are also installed on the wellheads of the first heat injection well 6 and the second heat injection well 9.

[0058] S3: Conduct conventional perforation operations on all well sections, with 16 holes per meter. In the first section of the rich oil coal pyrolysis block, conduct directional perforation between two adjacent grouting wells 17, heat injection well 1-6 and heat injection well 2-9, production well 1-4 and production well 2-7, horizontal well 1-5 and horizontal well 2-8. The perforation direction is as Figure 1 shown, which is used to enhance the fracture creation effect of adjacent grouting wells 17, heat injection well 1-6 and heat injection well 2-9, production well 1-4 and production well 2-7, horizontal well 1-5 and horizontal well 2-8 in the first section of the rich oil coal pyrolysis block. The number of directional perforations is 12 holes per meter;

[0059] S4: After perforation, conduct fracture creation operations on all well sections, which specifically include the following steps:

[0060] S401: Fill each grouting well 17 with water, whose function is to transmit the pressure generated by the controllable shock wave. Then, sequentially lower the controllable shock wave device into each grouting well 17. Specifically, the controllable shock wave device is a fracture-causing type controllable shock wave device, with the model: KK-ZL-600. When in use, adjust the parameters of the controllable shock wave device, control the fracture propagation radius within 5 meters, and the spacing between adjacent operation points is 5 meters. Sequentially conduct fracture creation operations on the coal seam sections of each grouting well 17, connect each well through the fractures, and the fracture creation radius of each grouting well 17 should not be less than half of the spacing between adjacent grouting wells 17;

[0061] S402: After the fracture creation of the grouting well 17 is completed, fill heat injection well 1-6, horizontal well 1-5, production well 1-4, heat injection well 2-9, horizontal well 2-8, and production well 2-7 with water, adjust the parameters of the controllable shock wave device, control the fracture propagation radius within 20 meters, and connect each well through the fractures. The spacing between adjacent operation points in the coal seam sections of the heat injection wells and production wells is 5 meters, and the spacing between adjacent operation points of the horizontal wells is 5 meters. Sequentially conduct fracture creation operations on each point of the first section of the rich oil coal pyrolysis block of heat injection well 1-6, production well 1-4, heat injection well 2-9, production well 2-7, and each point of horizontal well 1-5 and horizontal well 2-8. Before the fracture creation operation starts, close the wellheads of each well;

[0062] S403: After the operation of creating fractures is completed, perform formation drainage operation. The method of the formation drainage operation is as follows: First, lower the grouting pipes and air injection pipes 10 into each grouting well 17, the first heat injection well 6, the second heat injection well 9, the first production well 4, and the second production well 7. Then, inject pressurized air from the first heat injection well 6, the second heat injection well 9, the first production well 4, and the second production well 7. The air pressure is the formation fracture initiation pressure, and the pressure value is different for different formation depths. The water in the formation is discharged from each grouting well 17 in sequence. Then, inject pressurized air from each grouting well 17 again, and the water in the formation is discharged from the first heat injection well 6, the second heat injection well 9, the first production well 4, and the second production well 7 in sequence, which can ensure that the water in the pyrolysis zone is basically discharged to the surface. When the total flow rate of the air discharged from each grouting well is 90% of the flow rate of the injected pressurized air and the volume percentage of water in the air is 10%, stop injecting pressurized air from the heat injection wells and production wells; then inject pressurized air from each grouting well 17 simultaneously, and discharge the water in the formation from the heat injection wells and production wells simultaneously. When the total flow rate of the air discharged from the heat injection wells and production wells is 90% of the injection flow rate and the volume percentage of water in the air is 10%, stop injecting pressurized air and close each well, and the formation drainage operation ends.

[0063] As Figure 4 shown, demarcate the monitoring strip 18 on the ground to monitor the spatial diffusion range of the grout body. In the plane, the distance between the boundary line of the monitoring strip 18 and the well position is 15 meters. Before the grouting starts, use the high-density resistivity method to measure the initial resistivity data of the oil-rich coal seam within the range of the ground monitoring boundary line. The various measurement parameters of the high-density resistivity method are determined according to the geological data of the oil-rich coal pyrolysis block 1. Combine the initial resistivity data of the formation to invert the spatial positions of the well positions in the formation, and compare with the formation geological data and drilling data to adjust the inversion algorithm of the formation resistivity data. When the difference between the inverted spatial position of the formation well position and the actual well position spatial position data is 0.1%, stop adjusting the inversion algorithm. According to the obtained resistivity data of the oil-rich coal seam, select the type of resistivity regulator for the high-temperature resistant cement slurry. When the resistivity of the oil-rich coal seam is lower than the resistivity of the high-temperature resistant cement slurry, the resistivity regulator is ultrafine cubic boron nitride powder; when the initial resistivity of the oil-rich coal seam is higher than the resistivity of the high-temperature resistant cement slurry, the resistivity regulator is ultrafine pure iron powder; the addition amount of the resistivity regulator accounts for 5%-10% of the mass of the cement slurry, and the maximum diameter of the resistivity regulator is 1 / 3 of the minimum fracture width of the oil-rich coal seam. By increasing the resistivity difference between the high-temperature resistant cement slurry and the oil-rich coal seam, improve the accuracy of monitoring the diffusion range of the grout body, and then start the grouting operation.

[0064] S5: Perform grouting operation on the grouting well 17. The specific steps are as follows:

[0065] Inject high-temperature resistant cement slurry from each grouting well 17 simultaneously. Open two heat injection wells and close two production wells. Real-time monitor the pressure and flow rate of the exhausted air through the pressure sensors and flow meters of the two heat injection wells. When the air exhaust flow rate from the heat injection well is 1 / 3 of the theoretical flow rate, reduce the grouting pump volume to 2 / 3 of the initial pump volume, maintain the grouting pressure, close the two heat injection wells, and open the two production wells. When the cumulative air exhaust flow rate from the heat injection wells and the production wells is 2 / 3 of the theoretical flow rate, open the two heat injection wells again; when the cumulative air exhaust flow rate from the heat injection wells and the production wells is 5 / 4 of the theoretical flow rate, stop grouting; simultaneously inject pressurized air into the heat injection wells and the production wells, maintain the air pressure in the heat injection wells and the production wells at 5 / 4 of the initial gas pressure, and close the wellheads of each well at the same time, which can prevent the high-temperature resistant cement slurry from flowing continuously after grouting stops and ensure the controllability of the volume of the grouted body. A continuous grouted body is formed in the No. 1 coal seam section of the rich oil coal pyrolysis block to block the material transmission channel between the pyrolysis zone and the external space;

[0066] The calculation formula for the theoretical value of the air exhaust flow rate is shown in Equation 1,

[0067]

[0068] In Equation 1: Q - is the theoretical value of the air exhaust flow rate; P 1 - is the initial gas pressure; P 2 - is the real-time pressure of the gas during grouting; V 1 - is the fracture volume of the pyrolysis zone; A - is the cross-sectional area of the pipeline for exhausting air; t - is the time for exhausting air.

[0069] During grouting, the grouting parameters can be adjusted in a timely manner according to the diffusion range of the grouted body to make the grouted body evenly distributed in space, and at the same time, the strength of the grouted body can also be improved. After the start of grouting, the formation is monitored by the high-density resistivity method and compared with the initial resistivity of the rich oil coal seam in real time to preliminarily infer the diffusion range of the grouted body. When the comparison data is abnormal, the monitoring data is inverted to determine whether the diffusion of the grouted body is abnormal. If the diffusion of the grouted body is abnormal, adjust the various grouting parameters to ensure the controllability of the diffusion range of the grouted body; if the inversion result is normal, continue grouting with the original parameters.

[0070] S6: After the grouted body has finally set, open Heat Injection Well 1-6 and Heat Injection Well 2-9 to exhaust the air in the pyrolysis zone and carry out in-situ pyrolysis operations. The specific steps are as follows:

[0071] S601: Lower the first packer 13 from the first injection well 6 into the first horizontal well 5, activate the first packer 13, and then lower the downhole electric heater 12 into the first injection well 6. The first packer 13 is used to ensure that the high-temperature gas in the first injection well 6 flows through the pyrolyzed coal seam. Connect the first production pipe 16, the first slotted pipe 15, and the second packer 14 in sequence, and then lower the second packer 14 to one end of the first horizontal well 5 close to the first injection well 6 and activate the second packer 14; the second packer 14 is used to ensure that the high-temperature fluid flows through the coal seam to be pyrolyzed, and the first slotted pipe 15 ensures that the high-temperature formation fluid can be transported to the surface through the production pipe; the first packer 13 and the second packer 14 used are high-temperature resistant packers.

[0072] S602: Lower the third packer from the second injection well 9 into the second horizontal well 8, activate the third packer, and then lower the downhole electric heater 2 into the second injection well 9. The third packer is used to ensure that the high-temperature gas in the second injection well 9 flows through the pyrolyzed coal seam. Connect the second production pipe, the second slotted pipe, and the fourth packer in sequence, and then lower the fourth packer to one end of the second horizontal well 8 close to the second injection well 9 and activate the fourth packer; the fourth packer is used to ensure that the high-temperature fluid flows through the coal seam to be pyrolyzed, and the second slotted pipe ensures that the high-temperature formation fluid can be transported to the surface through the production pipe; the third packer and the fourth packer used are high-temperature resistant packers.

[0073] Both the first production pipe 16 and the second production pipe are heat-insulating pipes with heating functions. Specifically, both the first production pipe 16 and the second production pipe are electrically heated heat-insulating pipes, which can ensure that the wall temperature of the production pipe remains at 150 °C to prevent the heavy coal tar from cooling and blocking the production pipe.

[0074] S603: Pyrolyze the rich oil coal block on the connection line between the first injection well 6 and the first production well 4. The pyrolysis method is as follows: Close the first production well 4 and the second production well 7, inject pressurized N 2 into the first injection well 6. The purity of N 2 is 99.99%, and N 2 is used as the heating medium. When the pressure of N 2 in the first injection well 6 is greater than the formation fracture initiation pressure, start the downhole electric heater 12, and set the outlet temperature of the downhole electric heater 12 to 650 °C. When the oil and gas products obtained from the first production pipe 16 are 80% of the oil and gas products obtained in the laboratory under the same conditions, move the first production pipe 16 towards the first production well 4 at a moving speed of 5 meters per time. When the distance between the first production pipe 16 and the first production well 4 is 5 meters, turn off the downhole electric heater 12, the first injection well 6, and the first production well 4, and the pyrolysis and oil extraction work of the rich oil coal block on the connection line between the first injection well 6 and the first production well 4 ends; during the pyrolysis process, the pyrolysis products are transported to the ground through the first production pipe 16;

[0075] S604: Pyrolyze the rich oil coal block on the connection line between the second injection well 9 and the second production well 7. The pyrolysis method is as follows: Inject N into the second injection well 9 2 , start the downhole electric heater 2, and set the outlet temperature of the downhole electric heater 2 to 650 °C. When the distance between the second production pipe and the second production well 7 is 5 meters, close the second production well 7 and implement step S605; During pyrolysis, the pyrolysis products are transported to the ground through the second production pipe;

[0076] As the pyrolysis reaction proceeds, the production pipe continuously moves towards the production well. The pyrolysis products are directly transported to the ground through the production pipe without long-distance migration in the formation, which can prevent the pyrolysis products from blocking the formation, ensure the timely discharge of the pyrolysis products to the ground, and improve the recovery rate of the pyrolysis products.

[0077] S605: Pyrolyze the rich oil coal block on the connection line between the first injection well 6 and the second production well 7. The specific steps are as follows:

[0078] Open the first production well 4, pyrolyze and extract oil from the rich oil coal on the connection line between the second injection well 9 and the first production well 4. When the oil and gas products obtained from the first production well 4 are 15% of the oil and gas products obtained in the laboratory under the same conditions, sequentially close the downhole electric heater 2, the second injection well 9, and the first production well 4;

[0079] S605: Pyrolyze the rich oil coal block on the connection line between the second injection well 9 and the first production well 4. The specific steps are as follows:

[0080] Inject pressurized N into the first injection well 6 2 (N 2 The pressure is the formation fracture pressure, and the pressure value is different for different formation depths), start the downhole electric heater 12, set its outlet temperature to 650 °C, open the second production well 7. When the oil and gas products obtained from the second production well 7 are 15% of the oil and gas products obtained in the laboratory under the same conditions, sequentially close the downhole electric heater 12, the first injection well 6, and the second production well 7, and the pyrolysis and oil extraction work of the rich oil coal block ends.

[0081] As Figure 5 shown, after the pyrolysis products in steps S603, S604, and S605 are transported to the ground through the production pipe, they are then transported to the gas-liquid separator through the thermal compensation / cooling unit. The liquid products are processed by the oil-water separator, and the coal tar is stored in the storage oil tank, and the waste water is stored in the storage water tank; The gaseous products are transported to the gas separation device after being measured by the on-line analyzer. The on-line analyzer is used to analyze the components and their percentage contents of the gaseous products. After the gaseous products are separated by the gas separation device, each component is stored separately.

[0082] When the temperature of the pyrolysis product is relatively low, the heat compensation / cooling unit is used to heat the pyrolysis product to 150 °C to prevent the pyrolysis product from blocking the pipeline due to too low temperature; when the temperature of the pyrolysis product is relatively high, the heat compensation / cooling unit is used to cool the pyrolysis product to 150 °C to prevent the too high temperature of the pyrolysis product from affecting the gas-liquid separation effect.

[0083] S7: Re-develop the oil-rich coal seam after pyrolysis. The specific method is as follows:

[0084] First, inject air into injection well 1-6 and injection well 2-9, start downhole electric heater 1-12 and downhole electric heater 2 respectively, set the outlet temperature of the downhole electric heater to 500 °C, and ignite the oil-rich coal seam after pyrolysis;

[0085] Then, monitor the combustion situation of the coal seam after pyrolysis through the product components of production well 1-4 and production well 2-7. After the coal seam is ignited, switch the air to a mixed gas. The components of the mixed gas include O 2 , N 2 , H 2 O. The specific parameters are (5% O 2 , 89% N 2 , 6% H 2 O), (8% O 2 , 82% N 2 , 10% H 2 O). The adjustment interval between adjacent parameter combinations is 24 hours. The outlet temperature of the downhole electric heater is adjusted between 500 °C and 550 °C according to the product components in the production pipe;

[0086] The O 2 in the mixed gas is used to react with the coal after pyrolysis, further increasing the temperature of the mixed gas and making it easier for the coal after pyrolysis to react with H 2 O; the temperature of the coal seam after pyrolysis is relatively high, and the remaining heat can provide part of the heat required for the reaction of the coal after pyrolysis with H 2 O, reducing energy consumption; after the reaction, CO and H 2 are generated. The generated gas is transported to the ground through production pipe 1-16 and production pipe 2. After separation and purification, CO, H 2 , N 2 are stored separately. When the yields of CO and H 2 meet the design requirements, the process operation stops, and the downhole electric heater, injection well, and production well are closed in sequence.

[0087] Further, during the second in-situ underground conversion, first calculate the monthly input cost during the in-situ underground conversion of rich oil coal production, and calculate the monthly income during the in-situ underground conversion of rich oil coal production according to the amount of pyrolysis products; then calculate the monthly profit during the in-situ underground conversion of rich oil coal production based on the monthly input cost and the monthly income; finally, make monthly adjustments to the in-situ underground conversion process parameters according to the monthly profit during the in-situ underground conversion of rich oil coal production.

[0088] The calculation method of the monthly input cost is as follows in Equation 2:

[0089]

[0090] In Equation 2: A is the monthly input cost, in ten thousand yuan; Bw is the well drilling, completion and grouting cost, in ten thousand yuan; Y is the planned production months of the project; Dw is the cost of surface equipment and project infrastructure construction, in ten thousand yuan; Pw is the monthly maintenance cost of project equipment, in ten thousand yuan; Ew is the electricity cost, in yuan / kW·h; W is the monthly electricity consumption, in kW·h; Fw is the monthly cost of project personnel, in ten thousand yuan.

[0091] The monthly income is calculated as follows in Equation 3:

[0092] B = Q L ·P L + Q G ·P G (3)

[0093] In Equation 3: B is the monthly income, in ten thousand yuan; Q L - is the monthly output of coal tar, in barrels; P L - is the price of coal tar, in yuan / barrel; Q G - is the monthly output of gaseous products, in m 3 ; P G - is the price of gaseous products, in yuan / m 3 ; A is the monthly input cost. The gaseous products include CH 4 , CO, H 2 and other gases, and are uniformly converted according to the output and price of CH 4 during calculation.

[0094] The monthly profit H is calculated as follows in Equation 4:

[0095] H = B - A (4)

[0096] In summary, the comprehensive utilization method for in-situ underground conversion of rich oil coal provided by the present invention forms a continuous grouting body in the 1 coal seam section of the rich oil coal pyrolysis block, blocking the hydraulic connection between the pyrolysis area and the surrounding strata, solving the problem that the heating efficiency is affected by the intrusion of formation water during the in-situ underground conversion of rich oil coal, and at the same time preventing the diffusion of pyrolysis pollutants to the surrounding strata. By using horizontal wells and packers in combination, the blockage of the formation by heavy coal tar can be prevented, and the recovery rate of pyrolysis products can be improved. By alternately using the grouting well 17, the heat injection well, and the production well as the pressurized air injection well and the drainage well, the displacement effect of formation water in the pyrolysis area can be improved. By reacting oxygen with the pyrolyzed coal, the energy consumption of the gasification reaction can be reduced; moreover, the economic benefits of the in-situ underground conversion method of rich oil coal can be evaluated monthly, the operation of the in-situ underground conversion method can be monitored, and appropriate monthly adjustments can be made to the operation parameters of the process according to the historical monthly profit, improving the economy of the entire project.

[0097] The above content is a further detailed description of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention belongs, without departing from the concept of the present invention, several simple deductions or substitutions can be made, and all should be regarded as belonging to the protection scope of the present invention.

Claims

1. An integrated utilization method for in-situ conversion of rich oil coal underground, characterized in that: It includes the following steps: S1: Construct injection well 1 (6), production well 1 (4), injection well 2 (9) and production well 2 (7) above the coal seam roof (2) of the rich oil coal pyrolysis block (1). The lower ends of the injection well 1 (6), production well 1 (4), injection well 2 (9) and production well 2 (7) are all drilled into the coal seam floor (3). Then, construct horizontal well 1 (5) in the rich oil coal pyrolysis block (1) to connect the injection well 1 (6) and the production well 1 (4), and construct horizontal well 2 (8) in the rich oil coal pyrolysis block (1) to connect the injection well 2 (9) and the production well 2 (7). Finally, lower casings into the injection well 1 (6), production well 1 (4), horizontal well 1 (5), injection well 2 (9), production well 2 (7) and horizontal well 2 (8) for cementing operations; S2: Construct several grouting wells (17) above the coal seam roof (2) at the edge of the rich oil coal pyrolysis block (1). The lower ends of the grouting wells (17) are all drilled into the coal seam floor (3). The several grouting wells (17) enclose the rich oil coal pyrolysis block (1). After drilling, lower casings for cementing operations; S3: Conduct conventional perforation operations on all well sections. In the rich oil coal pyrolysis block (1) section, conduct directional perforation between two adjacent grouting wells (17), injection well 1 (6) and injection well 2 (9), production well 1 (4) and production well 2 (7), horizontal well 1 (5) and horizontal well 2 (8); S4: After perforation, conduct fracture creation operations on all well sections; S5: Conduct grouting operations on the grouting wells (17); S6: Conduct in-situ pyrolysis operations after the grout has finally set.

2. An integrated utilization method for in-situ conversion of rich oil coal underground as described in claim 1, characterized in that: Before step S4, install the wellheads of injection well 1 (6) and injection well 2 (9), production well 1 (4) and production well 2 (7), and install annulus valves (11) on each wellhead.

3. An integrated utilization method for in-situ conversion of rich oil coal underground as described in claim 2, characterized in that: Step S4 specifically includes the following steps: S401: Fill each grouting well (17) with water, successively lower controllable shock wave devices into each grouting well (17), and successively conduct fracture creation operations on the coal seam sections of each grouting well (17) to connect the wells through the fractures; S402: After the fracture creation of the grouting wells (17) is completed, fill the injection well 1 (6), horizontal well 1 (5), production well 1 (4), injection well 2 (9), horizontal well 2 (8), and production well 2 (7) with water, and successively conduct fracture creation operations on the rich oil coal pyrolysis block (1) section of the injection well 1 (6), production well 1 (4), injection well 2 (9), production well 2 (7) and each point of the horizontal well 1 (5), horizontal well 2 (8); S403: After the fracture creation operation is completed, conduct formation drainage operations.

4. An integrated utilization method for in-situ conversion of rich oil coal underground as described in claim 1, characterized in that: Before the grouting starts, a monitoring strip (18) is demarcated on the ground to monitor the spatial diffusion range of the grout body. The initial resistivity data of the oil-rich coal seam is measured by the high-density resistivity method within the ground monitoring boundary line range, and the resistivity of the grout is adjusted according to the initial resistivity of the oil-rich coal seam to increase the difference between the resistivity of the grout and the initial resistivity of the oil-rich coal seam. After the grouting starts, the formation is monitored by the high-density resistivity method, and compared with the initial resistivity of the oil-rich coal seam in real time to infer the diffusion range of the grout body, and the grouting parameters are adjusted according to the comparison data.

5. A comprehensive utilization method for in-situ conversion of oil-rich coal underground as described in claim 3, characterized in that: The formation drainage operation includes the following steps: First, grouting pipes and gas injection pipes (10) are lowered into each grouting well (17), the first heat injection well (6), the second heat injection well (9), the first production well (4), and the second production well (7). Then, pressurized air is injected from the first heat injection well (6), the second heat injection well (9), the first production well (4), and the second production well (7). The water in the formation is discharged from each grouting well (17) in sequence, and then pressurized air is injected from each grouting well (17) again, and the water in the formation is discharged from the first heat injection well (6), the second heat injection well (9), the first production well (4), and the second production well (7) in sequence.

6. A comprehensive utilization method for in-situ conversion of oil-rich coal underground as described in claim 2, characterized in that: Step S6 specifically includes the following steps: S601: Lower the first packer (13) from the first heat injection well (6) into the first horizontal well (5) and activate the first packer (13). Then, lower the downhole electric heater one (12) into the first heat injection well (6). Connect the first production pipe (16), the first slotted pipe (15), and the second packer (14) in sequence, and then lower the second packer (14) to the end of the first horizontal well (5) close to the first heat injection well (6) and activate the second packer (14); S602: Lower the third packer from the second heat injection well (9) into the second horizontal well (8) and activate the third packer. Then, lower the downhole electric heater two into the second heat injection well (9). Connect the second production pipe, the second slotted pipe, and the fourth packer in sequence, and then lower the fourth packer to the end of the second horizontal well (8) close to the second heat injection well (9) and activate the fourth packer; S603: Pyrolyze the oil-rich coal block on the connection line between the first heat injection well (6) and the first production well (4), and transport the pyrolysis products to the ground through the first production pipe (16); S604: Pyrolyze the oil-rich coal block on the connection line between the second heat injection well (9) and the second production well (7), and transport the pyrolysis products to the ground through the second production pipe; S605: Pyrolyze the oil-rich coal block on the connection line between the first heat injection well (6) and the second production well (7), and transport the pyrolysis products to the ground through the second production pipe; S606: Pyrolyze the oil-rich coal block on the connection line between the second heat injection well (9) and the first production well (4), and transport the pyrolysis products to the ground through the first production pipe (16).

7. A comprehensive utilization method for in-situ conversion of oil-rich coal underground as described in claim 2, characterized in that: The method further includes step S7: First, inject air into injection well 1 (6) and injection well 2 (9), start downhole electric heater 1 (12) and downhole electric heater 2 respectively, and ignite the oil-rich coal seam after pyrolysis. Then, monitor the combustion of the pyrolyzed coal seam through the product components of production well one (4) and production well two (7). After the coal seam is ignited, switch the air to a mixed gas, and the components of the mixed gas include O 2 , N 2 , H 2 O. The mixed gas reacts with the oil-rich coal seam after pyrolysis to generate CO and H 2 . The generated gas is transported to the ground through production pipe one (16) and production pipe two.

8. A comprehensive utilization method for in-situ underground conversion of oil-rich coal according to claim 6, characterized in that: Both the first production pipe (16) and the second production pipe are heat-insulating pipes with heating functions.

9. A comprehensive utilization method for in-situ underground conversion of oil-rich coal according to claim 1, characterized in that: After the grouting stops, inject pressurized air into injection well 1 (6), injection well 2 (9), production well 1 (4), and production well 2 (7). The pressure of the pressurized air is greater than the initial air pressure in the well, and is used to prevent the slurry from flowing continuously after the grouting stops.

10. A comprehensive utilization method for in-situ underground conversion of oil-rich coal according to claim 1, characterized in that: During the second in-situ underground conversion, first calculate the monthly input cost in the production process of in-situ underground conversion of oil-rich coal, and calculate the monthly income in the production process of in-situ underground conversion of oil-rich coal according to the amount of pyrolysis products; then calculate the monthly profit in the production process of in-situ underground conversion of oil-rich coal according to the monthly input cost and the monthly income; finally, make monthly adjustments to the in-situ underground conversion process parameters according to the monthly profit in the production process of in-situ underground conversion of oil-rich coal.

Images