Coal mine goaf mineralization, storage and carbon sequestration underground test method

Abstract

The invention discloses a coal mine goaf mineralization, sequestration and carbon sequestration underground test method. The method comprises a geological space for geological sequestration of supercritical / liquid carbon dioxide; testing geological space rock physical and mechanical characteristics and a micro-pore structure; designing and erecting a supercritical / liquid carbon dioxide injection pipeline, a solid waste slurry conveying pipeline, a monitoring pipeline and the like; calculating the thickness of the sealing wall and building the sealing wall by a building method; supercritical / liquid carbon dioxide is injected, solid waste slurry is conveyed, and the gas volume is monitored in a closed mode; continuously monitoring the residual gas in the geological space, and removing the sealing wall when the residual gas reaches a safe range; testing physical and mechanical properties and the like of sealed solid wastes, blind lane roofs, floors and surrounding coal rocks, and analyzing physical and mechanical differences before and after the test; according to the invention, the geological sequestration test can be carried out through supercritical or liquid carbon dioxide mineralization carbon sequestration, and the mineralization effect of slurry and supercritical or liquid carbon dioxide mineralization reaction products can be monitored in real time.

Description

Technical Field

[0001] The present invention relates to the technical field of underground carbon sequestration, and particularly relates to a method for underground test of mineralization and sequestration of carbon in a goaf of a coal mine. Background Art

[0002] CO2 geological sequestration is a core component of CCUS technology, which refers to injecting the captured CO2 into selected and safe geological bodies, and permanently sequestering CO2 in the geological bodies through physical sequestration and chemical sequestration mechanisms to achieve large-scale carbon removal technology. Due to the decline of the building materials market in recent years, the sales of coal-related solid waste resources such as gangue, gasification slag, and fly ash are not smooth, and the ground disposal costs are too high, etc., facing serious problems of stacking, which always affect the environmental problems of the stacking yard.

[0003] As an unconventional potential sequestration geological body, the goaf of a coal mine can provide a vast underground space. As long as it meets the requirements of a stable geological cover layer that is not affected by mining disturbances and good airtightness of the storage space, geological sequestration of supercritical / liquid CO2 mineralization and carbon sequestration in the goaf can be achieved. As an important negative carbon technology reserve to solve the carbon emission problems of high-energy-consuming industries such as coal / coal power, it can not only realize the secondary utilization of waste resources in the goaf of a coal mine to reduce ground subsidence, but also realize the reuse of coal-related solid waste resources such as gangue, gasification slag, and fly ash.

[0004] However, in the current mineralization and carbon sequestration in the goaf of a coal mine, some coal mine production units have carried out crushing and grouting of coal-related solid waste resources such as gangue, gasification slag, and fly ash in the goaf of a coal mine to achieve the effects of reducing subsidence, reinforcement, fire extinguishing, and water control in the goaf of a coal mine. Some coal mine units have also carried out perfusion of CO2 gas in the goaf of a coal mine to achieve the effect of preventing and extinguishing fires in the goaf of a coal mine. However, relevant research shows that the existing work has only carried out filling mineralization of gaseous carbon dioxide, and has not carried out geological sequestration tests for supercritical or liquid carbon dioxide mineralization and carbon sequestration under the condition of an underground closed goaf. At the same time, the mineralization effect of the slurry and the mineralization reaction products of supercritical or liquid carbon dioxide is also lacking in investigation.

[0005] For example, the prior art with the patent publication number CN116163730A and the patent name of "A Method for Two-way Progressive Filling Mining and Carbon Dioxide Sequestration of Thin Coal Seam Drills" discloses the following steps: (1) Conduct a geological survey of the mine geological conditions to obtain coal seam geological structure data; (2) Prepare filling slurry; (3) Layout the working face and arrange equipment; (4) Layout the carbon dioxide transportation pipeline; (5) Layout the filling pipeline; (6) Use a screw drill to drill and mine the upper and lower side coal seams successively; (7) Transport coal to the ground using a scraper conveyor; (8) The screw drill advances; (9) Treat the goaf, use coal gangue for in-situ filling, and inject filling slurry and carbon dioxide waste gas successively; (10) Carry out roadway support; (11) Repeat steps (2) to (10). It mainly designs a gaseous carbon dioxide transportation pipeline to the open goaf under the condition of side mining and side filling, and transports carbon dioxide waste gas (gaseous carbon dioxide) to react with coal gangue. Summary of the Invention

[0006] The technical problem to be solved by the present invention is: how to carry out geological sequestration tests for supercritical or liquid carbon dioxide mineralization and carbon fixation.

[0007] To solve the above technical problem, the present invention provides the following technical solutions:

[0008] An underground test method for mineralization sequestration and carbon fixation in a coal mine goaf, including:

[0009] S1. Select a geological space in the coal mine underground mining area that can be used for supercritical / liquid carbon dioxide geological sequestration;

[0010] S2. Test the physical and mechanical characteristics and microscopic pore structures of the surrounding rock, roof, and floor rocks of the geological space;

[0011] S3. Design and install supercritical / liquid carbon dioxide injection pipelines, solid waste slurry transportation pipelines, monitoring device pipelines, and pressure sensor pipelines to achieve multi-parameter dynamic real-time monitoring of the geological space;

[0012] S4. Calculate the thickness of the sealing wall and the masonry method, and build the sealing wall;

[0013] S5. Start injecting supercritical / liquid carbon dioxide and transport solid waste slurry, and carry out closed monitoring of the gas volume;

[0014] S6. Continuously monitor the remaining gas in the geological space, and remove the sealing wall after reaching the safe range;

[0015] S7. Test the physical and mechanical properties and microscopic pore structures of the sealed solid waste, the roof, floor, and surrounding coal and rock of the blind roadway, and compare and analyze the differences in the physical and mechanical properties of the rocks before and after the test.

[0016] This application utilizes the geological space in the underground mining area, tests the rock physical and mechanical properties in the geological space, etc., and then installs critical / liquid carbon dioxide injection pipelines, solid waste slurry transportation pipelines, monitoring device pipelines, pressure sensor pipelines, etc. to achieve the injection and storage of supercritical / liquid carbon dioxide and solid waste slurry. During this process, multi-parameter dynamic real-time monitoring is carried out. After continuous monitoring, it is ensured to reach the safe range. Finally, the differences in the rock physical and mechanical properties after storage are compared. This process can realize the geological storage test of supercritical or liquid carbon dioxide mineralization and carbon sequestration; at the same time, real-time monitoring is carried out on the mineralization effect of the slurry and the mineralization reaction products of supercritical or liquid carbon dioxide and the differences before and after the reaction of the surrounding country rock (rock physical and mechanical properties, microscopic pore structure).

[0017] As a further solution of the present invention: The geological space includes, but is not limited to, the blind lanes or chambers within the underground mining area range that can be enclosed and do not affect the production and excavation work space.

[0018] As a further solution of the present invention: In the step S2;

[0019] The rock range for testing the rock physical and mechanical properties of the roof and floor includes, but is not limited to, different types of rocks within the range of 25m - 30m above the roof and 25m - 30m below the floor of the geological space;

[0020] The rock physical property indexes for testing include, but are not limited to, rock density, rock weight, rock hardness, rock porosity, rock natural moisture content, rock natural water absorption rate, rock natural water retention rate;

[0021] The rock mechanical property indexes for testing include, but are not limited to, rock compressive strength, rock tensile strength, rock elastic modulus, rock shear modulus, rock Poisson's ratio, rock softening coefficient.

[0022] As a further solution of the present invention: The monitoring objects of the monitoring device in the step S3 include, but are not limited to, gas, temperature, pH value.

[0023] As a further solution of the present invention: In the step S3:

[0024] The critical / liquid carbon dioxide injection pipeline is installed on the middle side of the geological space;

[0025] The solid waste slurry transportation pipeline is installed on one side of the top of the geological space;

[0026] The monitoring device pipeline is installed on the other side of the top of the geological space;

[0027] The pressure sensor pipeline is installed in the middle of the top of the geological space.

[0028] As a further solution of the present invention: The monitoring device includes a gas sensor for detecting gas, and at least three gas sensors are arranged at positions evenly distributed outward from the closed wall.

[0029] As a further solution of the present invention: At least two gas sensors are arranged inward from the closed wall, one at the innermost side of the closed wall and one close to the closed wall.

[0030] As a further solution of the present invention: The masonry materials of the closed wall in step S4 include but are not limited to concrete, yellow sand, fly ash, or coal gangue cementitious materials.

[0031] As a further solution of the present invention: When all the gas sensors inside the geological space reach below the limit value, it is considered that the supercritical / liquid carbon dioxide geological sequestration carbonization has been completed.

[0032] As a further solution of the present invention: The range of the rock physical and mechanical property test in step S7 is within 25m - 30m above the roof of the geological space, within 25m - 30m below the floor, and within 15m - 20m of the surrounding coal and rock.

[0033] Compared with the prior art, the beneficial effects of the present invention are:

[0034] This application utilizes the geological space mined in the underground mining area, tests the rock physical and mechanical properties in the geological space, etc., and then installs critical / liquid carbon dioxide injection pipelines, solid waste slurry transportation pipelines, monitoring device pipelines, pressure sensor pipelines, etc. to realize the injection of supercritical / liquid carbon dioxide and solid waste slurry for sequestration. During this process, multi-parameter dynamic real-time monitoring is carried out. After continuous monitoring, it is ensured to reach the safe range. Finally, the differences in the rock physical and mechanical properties after sequestration are compared. This process can realize the geological sequestration test of supercritical or liquid carbon dioxide mineralization and carbon sequestration; at the same time, real-time monitoring is carried out on the mineralization effect of the slurry and the mineralization reaction products of supercritical or liquid carbon dioxide and the differences before and after the reaction of the surrounding rock mass (rock physical and mechanical properties, microscopic pore structure). Description of the Drawings

[0035] Figure 1 It is a schematic structural diagram of the underground test operation of the mineralization sequestration and carbon sequestration in the goaf of the coal mine in the embodiment of the present invention;

[0036] Figure 2 It is an embodiment of the present invention Figure 1 Top view;

[0037] Description of the reference numerals: 1. Geological space; 2. Closed wall; 3. Supercritical / liquid carbon dioxide injection pipeline; 4. Monitoring device pipeline; 5. Pressure sensor pipeline; 6. Solid waste slurry transportation pipeline; 7. Gas sensor one; 8. Gas sensor two. Detailed implementation manners

[0038] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0039] Embodiment 1

[0040] A downhole test method for mineralization and carbon sequestration in a coal mine goaf includes the following steps:

[0041] Step S1: Optimize the geological space in the coal mine underground mining area available for supercritical / liquid carbon dioxide geological sequestration;

[0042] Step S11: Select the goaf in the south three mining area of a certain coal mine in Huainan Mining Area as the geological sequestration space for supercritical / liquid carbon dioxide;

[0043] Step S12: The test scale to be carried out in the small geological space available for supercritical / liquid carbon dioxide geological sequestration in the south three mining area of a certain coal mine in Huainan Mining Area is 0.8 t (ton) of carbon dioxide and 12 t (ton) of solid waste slurry;

[0044] Step S13: The raw materials of the solid waste slurry are fly ash from a by-product of a certain power plant in Huainan Mining Area and screened coal gangue from a certain coal preparation plant. Through crushing treatment, the solid waste slurry is obtained;

[0045] Step S14: There are seven small geological spaces available for supercritical / liquid carbon dioxide geological sequestration in the south three mining area of a certain coal mine in Huainan Mining Area, including four blind headings and three refuge chambers. See Table 1 for details;

[0046] Table 1 is a simple table of the small geological space available for supercritical / liquid carbon dioxide geological sequestration in the blind headings of the south three mining area of a certain coal mine in Huainan Mining Area

[0047]

[0048] It should be noted that the homogeneity and inhomogeneity in the properties in the table refer to whether the lithological properties are similar or the same; if the lithology of an area is all argillaceous rock, the property is homogeneous; if the lithology is a mixture of argillaceous and sandy rocks, it is inhomogeneous.

[0049] Step S15: According to the surrounding rock properties, the preferred small geological spaces to be selected are Blind Heading 1, Blind Heading 3 and Chamber 1;

[0050] Step S16: According to Step S15, considering the minimum thickness from the goaf (safety influencing factor), the small geological spaces available for selection are preferably Blind Alley 1, Blind Alley 3, and Chamber 1;

[0051] Step S17: According to Step S16, considering the distance from the transportation track, the small geological spaces available for selection are preferably Blind Alley 3 and Chamber 1;

[0052] Step S18: According to Step S17, considering the scale of the experiment to be carried out in the small geological space and the scope of the small geological space, the small geological space available for selection is preferably Blind Alley 3.

[0053] Step S2: Test the physical and mechanical characteristics and microscopic pore structures of the surrounding rock, roof, and floor rocks in the geological space;

[0054] Step S21: Collect data on different types of rocks within 30 m above the roof and 30 m below the floor of Blind Alley 3, and drill on-site samples of different types of rocks within 30 m above the roof and 30 m below the floor in the same mining area;

[0055] Step S22: Collect data on the coal seam or gangue in the same horizon in the surrounding rock of Blind Alley 3, and drill samples of the coal seam or gangue in the same horizon in Blind Alley 3;

[0056] Step S23: Test and obtain the physical properties of the rocks such as rock density, rock weight, rock porosity, natural moisture content of the rock, natural water absorption of the rock, and natural water retention rate of the rock, as well as the mechanical property indexes of the rocks such as uniaxial compressive strength of the rock, tensile strength of the rock, elastic modulus of the rock, shear modulus of the rock, Poisson's ratio of the rock, and softening coefficient of the rock within 30 m above the roof and 30 m below the floor of Blind Alley 3 and the surrounding rock;

[0057] Step S24: Test and obtain the index parameters such as carbon dioxide adsorption pore structure, liquid nitrogen adsorption pore structure, mercury intrusion adsorption pore structure, SEM scanning electron microscope results, and XRD test results within 30 m above the roof and 30 m below the floor of Blind Alley 3 and the surrounding rock.

[0058] Step S3: Design and install supercritical / liquid carbon dioxide injection pipelines, solid waste slurry transportation pipelines, (gas, temperature, pH value) monitoring device pipelines, and pressure sensor pipelines to achieve multi-parameter dynamic real-time monitoring of the geological space;

[0059] Step S31: Install the supercritical / liquid carbon dioxide injection pipeline 3 on the side of the middle part of Blind Alley 3 (refer to Figure 1 );

[0060] Step S32: Install the solid waste slurry transportation pipeline 6 on the right side of the top of Blind Alley 3 (refer to Figure 1) to prevent blockage of other parts and the slurry pipeline. The slurry raw materials transported by the solid waste slurry pipeline include, but are not limited to, solid waste slurries such as coal gangue, gasification slag, and fly ash, either alone or in mixture;

[0061] Step S33: Install the gas-temperature-pH value monitoring device pipeline 4 on the left side at the top of the blind roadway 3 (refer to Figure 1 ) for monitoring the air gas concentration, temperature, and pH value within the area of the test space;

[0062] Step S34: Install the pressure sensor pipeline 5 in the middle at the top of the blind roadway 3 (refer to Figure 1 ) for monitoring the pressure change state in the small geological space;

[0063] It should be noted that the left and right top directions designed in the above Steps S31 - S34 are based on Figure 2 ;

[0064] Step S35: The types of gas monitoring devices include carbon dioxide, oxygen, nitrogen, and carbon monoxide;

[0065] Step S36: The gas sensors should be evenly arranged according to the distribution law of the small geological space. At least two gas sensors should be installed inside the sealing wall 2, one at the deepest part of the sealing wall 2 and one near the sealing wall 2, namely Figure 2 gas sensor one 7 and gas sensor two 8 in

[0066] Three gas sensors should be evenly arranged outside the sealing wall 2 at an interval of 3 m;

[0067] It should be noted that the temperature sensor can measure the temperature in the small geological space and display the corresponding value outside the pipeline; the pH sensor can measure the pH value in the small geological space and display the corresponding value outside the pipeline;

[0068] Step S38: When installing the gas-temperature-pH value sensors and pressure sensors in the blind roadway 3, they should be calibrated before use to ensure the normal state of the corresponding sensors;

[0069] Step S39: The supercritical / liquid carbon dioxide injection pipeline 3 and the solid waste slurry pipeline 6 installed in the blind roadway 3 should be equipped with stop valves outside the sealing wall 2;

[0070] Step S310: Flow meters should be installed outside the stop valves on the supercritical / liquid carbon dioxide injection pipeline 3 and the solid waste slurry conveying pipeline 6 installed in the blind heading 3.

[0071] Step S311: The stop valves and corresponding flow meters on the supercritical / liquid carbon dioxide injection pipeline 3 and the solid waste slurry conveying pipeline 6 installed in the blind heading 3 should be inspected before use to ensure that the stop valves and corresponding flow meters are in normal condition.

[0072] Step S4: Calculate the thickness and masonry method of the sealing wall, and build the sealing wall.

[0073] The masonry materials for the sealing wall of the blind heading 3 include, but are not limited to, cementitious materials such as concrete, yellow sand, fly ash, and coal gangue.

[0074] Preset 10 t (tons) of supercritical carbon dioxide and a perfusion volume of 50 t (tons) of solid waste slurry to calculate the thickness of the sealing wall. The masonry thickness of the sealing wall is calculated to be 3.5 m according to relevant numerical simulation software such as matlab. The above simulation software are all existing conventional software, and this application does not improve them, so no detailed description is given.

[0075] Calculating the thickness and masonry method of the sealing wall includes, but is not limited to, using relevant numerical simulation software such as matlab to calculate the pressure during the entire reaction cycle time with the corresponding perfusion volume of supercritical / liquid carbon dioxide and the perfusion volume of solid waste slurries such as coal gangue, gasification slag, and fly ash.

[0076] It should be noted that the masonry thickness of the sealing wall is determined by, but is not limited to, the thickness that can prevent the overflow of supercritical / liquid carbon dioxide and solid waste based on the inverse pressure and the selected masonry materials.

[0077] Step S43: The masonry thickness of the sealing wall is 4.2 m.

[0078] It should be noted that the actual masonry thickness should have a margin compared to the inverse pressure calculation, not less than 120% of the inverse pressure calculation, to prevent the sealing wall from being pushed open by the pressure. Therefore, the actual masonry thickness of the sealing wall is calculated to be 4.2 m by multiplying the inverse pressure calculation by 120%.

[0079] Step S44: The masonry method of the sealing wall includes, but is not limited to, manual masonry with steel structures of corresponding grades placed inside.

[0080] Step S5: Start injecting supercritical / liquid carbon dioxide, convey the solid waste slurry, and monitor the gas volume in the enclosure.

[0081] Step S51, respectively open the stop valves of the supercritical / liquid carbon dioxide injection pipeline 3 and the solid waste slurry delivery pipeline 6 in the blind alley 3, and always pay attention to the gas sensor, pressure sensor and the gas / slurry flow meter of the corresponding pipeline;

[0082] Step S52: When the amount of supercritical / liquid carbon dioxide or solid waste slurry transported in blind alley 3 is about to reach the expected limit, the corresponding stop valve is closed in time;

[0083] Step S53, timely pay attention to the gas sensor and pressure sensor outside the closed wall of the blind alley 3 to prevent the pressure or gas concentration from exceeding the limit;

[0084] Step S54: After the gas sensor and pressure sensor outside the closed wall of blind alley 3 exceed the limit, the stop valve of the supercritical / liquid carbon dioxide injection pipeline and the solid waste slurry conveying pipeline should be closed in time according to the predetermined procedures, and the on-site workers should be evacuated.

[0085] Step S6: Continuously monitor the gas residual inside the geological space, and remove the closed wall after reaching a safe range;

[0086] Step S61, continuously monitoring the values of the gas-temperature-pH value monitoring sensors inside the blind alley 3, when the corresponding dangerous values of the carbon dioxide, oxygen, nitrogen, and carbon monoxide gas sensors inside the small geological space reach below the limit, it is considered that the carbon dioxide geological storage carbonization has been completed;

[0087] Step S62: while continuously monitoring the relevant values of the carbon dioxide, oxygen, nitrogen and carbon monoxide gas sensors inside the small geological space, arrange relevant personnel wearing isolation protective clothing to dismantle the closed wall.

[0088] Step S7, testing the physical and mechanical properties and microscopic pore structure of the sealed solid waste, blind alley roof, floor and surrounding coal rock, and comparing and analyzing the differences in the physical and mechanical properties of the rock before and after the test;

[0089] Step S71, testing the physical and mechanical properties of the reactant rock after the sealed solid waste reacts with supercritical / liquid carbon dioxide;

[0090] Step S72, testing the physical and mechanical properties of the rock within 30 m above the roof and 30 m below the floor of the blind lane 3 and within 20 m of the surrounding coal and rock;

[0091] Step S73: Test and obtain the physical properties of rocks such as the rock density, rock weight, rock porosity, natural water content of rock, natural water absorption of rock, and natural water retention rate of rock, as well as the mechanical property indexes of rocks such as the compressive strength of rock, tensile strength of rock, elastic modulus of rock, shear modulus of rock, Poisson's ratio of rock, and softening coefficient of rock, at 30 m above the roof, 30 m below the floor, and in the surrounding rock of the blind roadway 3 after the reaction;

[0092] Step S74: Test and obtain the index parameters such as the carbon dioxide adsorption pore structure, liquid nitrogen adsorption pore structure, mercury intrusion adsorption pore structure, SEM scanning electron microscope results, and XRD test results, at 30 m above the roof, 30 m below the floor, and in the surrounding rock of the blind roadway 3 after the reaction;

[0093] Step S75: Compare and analyze the differences before and after the supercritical / liquid carbon dioxide geological storage test, including but not limited to parameters such as the physical and mechanical properties of rocks and the microscopic pore structure; provide technical support for the subsequent large-scale supercritical / liquid carbon dioxide geological storage.

[0094] Example 2

[0095] Other steps are the same as those in Example 1. The differences from Example 1 are Steps S2 and S7:

[0096] Specifically, in Step S2: Test the physical and mechanical characteristics and microscopic pore structure of the surrounding rock, roof, and floor rocks in the geological space;

[0097] Step S21: Collect data on different types of rocks within the range of 25 m above the roof and 25 m below the floor of the blind roadway 3, and drill on-site samples of different types of rocks within the range of 25 m above the roof and 25 m below the floor in the same mining area;

[0098] Step S22: Collect data on the coal seam or gangue in the same horizon in the surrounding rock of the blind roadway 3, and drill samples of the coal seam or gangue in the same horizon in the blind roadway 3;

[0099] Step S23: Test and obtain the physical properties of rocks such as the rock density, rock weight, rock porosity, natural water content of rock, natural water absorption of rock, and natural water retention rate of rock, as well as the mechanical property indexes of rocks such as the compressive strength of rock, tensile strength of rock, elastic modulus of rock, shear modulus of rock, Poisson's ratio of rock, and softening coefficient of rock, at 25 m above the roof, 25 m below the floor, and in the surrounding rock of the blind roadway 3;

[0100] Step S24: Test and obtain the index parameters such as the carbon dioxide adsorption pore structure, liquid nitrogen adsorption pore structure, mercury intrusion adsorption pore structure, SEM scanning electron microscope results, and XRD test results, at 25 m above the roof, 25 m below the floor, and in the surrounding rock of the blind roadway 3.

[0101] Specifically, in step S7, test the physical and mechanical properties and microscopic pore structures of the sealed solid waste, the roof, the floor, and the surrounding coal and rock in the blind roadway, and comparatively analyze the differences in the physical and mechanical properties of the rock before and after the test;

[0102] In step S71, test the physical and mechanical properties of the reactant rock after the reaction of the sealed solid waste with supercritical / liquid carbon dioxide;

[0103] In step S72, test the physical and mechanical properties of the rock within 25 m above the roof and 25 m below the floor of the blind roadway 3 and within 15 m of the surrounding coal and rock;

[0104] In step S73, test and obtain the physical properties of the rock such as the rock density, rock weight, rock porosity, natural water content of the rock, natural water absorption of the rock, and natural water retention rate of the rock, and the mechanical property indexes of the rock such as the rock compressive strength, rock tensile strength, rock elastic modulus, rock shear modulus, rock Poisson's ratio, and rock softening coefficient for the rock 25 m above the roof and 25 m below the floor of the blind roadway 3 after the reaction and the surrounding rock;

[0105] In step S74, test and obtain the index parameters such as the carbon dioxide adsorption pore structure, liquid nitrogen adsorption pore structure, mercury intrusion adsorption pore structure, SEM scanning electron microscope results, and XRD test results for the rock 25 m above the roof and 25 m below the floor of the blind roadway 3 after the reaction and the surrounding rock;

[0106] In step S75, comparatively analyze the differences before and after the supercritical / liquid carbon dioxide geological sequestration test, including but not limited to parameters such as the physical and mechanical properties of the rock and the microscopic pore structure, so as to provide technical support for the subsequent large-scale supercritical / liquid carbon dioxide geological sequestration.

[0107] Example 3

[0108] Other steps are the same as those in Example 1. The differences from Example 1 are in step S2 and step S7:

[0109] Specifically, in step S2, test the physical and mechanical characteristics and microscopic pore structures of the surrounding rock, the roof, and the floor of the geological space;

[0110] In step S21, collect the data of different types of rocks within 27 m above the roof and 27 m below the floor of the blind roadway 3, and drill on-site samples of different types of rocks within 27 m above the roof and 27 m below the floor in the same mining area;

[0111] In step S22, collect the data of the coal seam or gangue in the same horizon in the surrounding rock of the blind roadway 3, and drill samples of the coal seam or gangue in the same horizon in the blind roadway 3;

[0112] Step S23: Test and obtain the physical properties of rocks such as the rock density, rock weight, rock porosity, natural water content of the rock, natural water absorption of the rock, and natural water retention rate of the rock, and the mechanical property indexes of the rock such as the compressive strength of the rock, tensile strength of the rock, elastic modulus of the rock, shear modulus of the rock, Poisson's ratio of the rock, and softening coefficient of the rock at 27 m above the roof, 27 m below the floor, and the surrounding rock of the blind roadway 3;

[0113] Step S24: Test and obtain the index parameters such as the carbon dioxide adsorption pore structure, liquid nitrogen adsorption pore structure, mercury intrusion adsorption pore structure, SEM scanning electron microscope results, and XRD test results at 27 m above the roof, 27 m below the floor, and the surrounding rock of the blind roadway 3.

[0114] Specifically, in Step S7: Test the physical and mechanical properties of the rock and the microscopic pore structure of the sealed solid waste, the roof, floor, and surrounding coal rock of the blind roadway, and compare and analyze the differences in the physical and mechanical properties of the rock before and after the test;

[0115] Step S71: Test the physical and mechanical properties of the reactant rock after the reaction of the sealed solid waste with supercritical / liquid carbon dioxide;

[0116] Step S72: Test the physical and mechanical properties of the rock within the range of 27 m above the roof and 27 m below the floor of the blind roadway 3 and within the range of 17 m of the surrounding coal rock;

[0117] Step S73: Test and obtain the physical properties of the rock such as the rock density, rock weight, rock porosity, natural water content of the rock, natural water absorption of the rock, and natural water retention rate of the rock, and the mechanical property indexes of the rock such as the compressive strength of the rock, tensile strength of the rock, elastic modulus of the rock, shear modulus of the rock, Poisson's ratio of the rock, and softening coefficient of the rock at 27 m above the roof, 27 m below the floor, and the surrounding rock of the blind roadway 3 after the reaction;

[0118] Step S74: Test and obtain the index parameters such as the carbon dioxide adsorption pore structure, liquid nitrogen adsorption pore structure, mercury intrusion adsorption pore structure, SEM scanning electron microscope results, and XRD test results at 27 m above the roof, 27 m below the floor, and the surrounding rock of the blind roadway 3 after the reaction;

[0119] Step S75: Compare and analyze the differences before and after the supercritical / liquid carbon dioxide geological sequestration test, including but not limited to parameters such as the physical and mechanical properties of the rock and the microscopic pore structure; provide technical support for the subsequent large-scale supercritical / liquid carbon dioxide geological sequestration.

[0120] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A downhole test method for mineralization and carbon sequestration in coal mine gob areas, characterized in that Including: S1. Geological space in the underground mining area of a coal preparation plant that can be used for supercritical / liquid carbon dioxide geological sequestration; S2. Testing the physical and mechanical properties and microscopic pore structures of the surrounding rock, roof, and floor rocks in the geological space; S3. Designing and installing supercritical / liquid carbon dioxide injection pipelines, solid waste slurry transportation pipelines, monitoring device pipelines, and pressure sensor pipelines to achieve multi-parameter dynamic real-time monitoring of the geological space; S4. Calculating the thickness of the sealing wall and the masonry method, and building the sealing wall; S5. Starting to inject supercritical / liquid carbon dioxide and transporting solid waste slurry, and carrying out closed monitoring of the gas volume; S6. Continuously monitoring the remaining gas in the geological space, and removing the sealing wall after reaching the safe range; S7. Testing the physical and mechanical properties and microscopic pore structures of the solid waste, blind roadway roof, floor, and surrounding coal and rock that have been sequestered, and comparing and analyzing the differences in the physical and mechanical properties of the rocks before and after the test.

2. The underground test method for mineralization and carbon sequestration in coal mine goaf according to claim 1, characterized in that: The geological space includes, but is not limited to, the space in the blind roadway or chamber within the underground mining area that can be sealed without affecting production and excavation work.

3. A method for underground test of mineralization and carbon sequestration in a coal mine goaf according to claim 1, characterized in that: In the step S2; The rock range for testing the physical and mechanical properties of the roof and floor rocks includes, but is not limited to, different types of rocks within the range of 25m - 30m above the roof and 25m - 30m below the floor of the geological space; The physical property indexes for testing the rocks include, but are not limited to, rock density, rock weight, rock hardness, rock porosity, natural water content of the rock, natural water absorption rate of the rock, and natural water retention rate of the rock; The mechanical property indexes for testing the rocks include, but are not limited to, rock compressive strength, rock tensile strength, rock elastic modulus, rock shear modulus, rock Poisson's ratio, and rock softening coefficient.

4. A method for underground test of mineralization and carbon sequestration in coal mine goafs according to claim 1, characterized in that: The monitoring objects of the monitoring device in the step S3 include, but are not limited to, gas, temperature, and pH value.

5. A method for underground test of mineralization and carbon sequestration in coal mine goafs according to claim 1, characterized in that: In the step S3: The supercritical / liquid carbon dioxide injection pipeline is installed on the middle side of the geological space; The solid waste slurry transportation pipeline is installed on one side of the top of the geological space; The monitoring device pipeline is installed on the other side of the top of the geological space; The pressure sensor pipeline is installed in the middle of the top of the geological space.

6. A method for underground test of mineralization and carbon sequestration in a coal mine goaf according to claim 5, characterized in that: The monitoring device includes gas sensors for detecting gas, and at least three gas sensors are arranged at evenly distributed positions outward from the sealing wall.

7. A method for underground test of mineralization and carbon sequestration in coal mine goafs according to claim 6, characterized in that: At least two gas sensors are arranged inward from the sealing wall, including one at the innermost side of the sealing wall and one near the sealing wall.

8. A method for underground test of mineralization and carbon sequestration in coal mine gob areas according to claim 1, characterized in that: The masonry materials for the sealing wall in the step S4 include, but are not limited to, concrete, yellow sand, fly ash, or coal gangue cementitious materials.

9. A method for underground test of mineralization and carbon sequestration in coal mine goafs according to claim 1, characterized in that: When all the gas sensors inside the geological space reach below the limit value, it is considered that the supercritical / liquid carbon dioxide geological sequestration carbonization has been completed.

10. A method for underground test of mineralization and carbon sequestration in coal mine goafs according to claim 1, characterized in that: The range for testing the physical and mechanical properties of the rocks in the step S7 is within the range of 25m - 30m above the roof and 25m - 30m below the floor of the geological space and within the range of 15m - 20m of the surrounding coal and rock.

Images