Construction method of artificial geological cover layer for carbon dioxide sequestration

Abstract

The invention discloses a construction method of an artificial geological cover layer for carbon dioxide sequestration, and belongs to the technical field of carbon dioxide sequestration. The construction method of the artificial geological cover layer for carbon dioxide sequestration comprises the following steps: determining construction parameters of the artificial geological cover layer; determining the position of an overlying strata artificial geological cap layer in the mining space, and determining the position of an overlying strata key layer by using a key layer discrimination method according to drilling geological data of a mining area; determining the following grouting parameters including arrangement and size of ground grouting holes, proportion and particle size of grouting materials and grouting pressure; grouting is conducted on the artificial geological cover layers with different depths; and CO2 leakage of the artificial geological cover layer is monitored. According to the construction method of the artificial geological cap layer for carbon dioxide sequestration, the CO2 coal mine mining space geological sequestration reserves can be increased, and the application range of the CO2 coal mine mining space geological sequestration technology is wider.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon dioxide sequestration, and in particular to a construction method of an artificial geological cover layer for carbon dioxide sequestration. Background Art

[0002] Carbon capture, storage and utilization (CCUS) technology is one of the important technologies for energy conservation and emission reduction and realizing CO2 resource utilization, and geological storage of CO2 in coal mining space is an important part of it.

[0003] The key factors for the storage capacity and storage effect of CO2 coal mining space geological sealing are the sealing, integrity and continuity of the overburden cover of the mining space, which puts forward strict requirements on the permeability and thickness of the geological cover. Although my country has a huge underground coal mining space, the natural cover of most underground mining spaces is difficult to meet the geological conditions of sealing, integrity and continuity required for CO2 storage, resulting in a low storage capacity of CO2 coal mining space geological sealing, which limits the promotion of CO2 coal mining space geological sealing technology. Summary of the invention

[0004] The purpose of the present invention is to overcome the problems in the prior art and provide a construction method for an artificial geological cover for carbon dioxide storage, which can increase the geological storage capacity of CO2 coal mine mining space and make the application scope of CO2 coal mine mining space geological storage technology more extensive.

[0005] The present invention provides a construction method of an artificial geological cover layer for carbon dioxide storage, comprising the following steps: S01: Determine the construction parameters of the artificial geological cover layer, including the ground construction scope of the artificial geological cover layer, the permeability coefficient and thickness of the artificial geological cover layer; S02: Determine the position of the artificial geological cover layer in the mining space, determine the position of the key layer of the overburden rock by using the key layer identification method according to the drilling geological data of the mining area, calculate the height of the overburden rock collapse fracture zone, and use geotechnical engineering software to establish a numerical calculation model to simulate the development law of overburden rock fractures caused by coal seam mining in the artificial geological cover layer area. Combined with theoretical calculation and numerical simulation results, the position of the artificial geological cover layer is set above the overburden rock collapse fracture zone; S03: According to the different lithologies within the geological cover layer, the following grouting parameters are determined: the layout and size of the ground grouting holes, the proportion and particle size of the grouting materials, and the grouting pressure; S04: within the range of the artificial geological cover layer, grouting is performed on the artificial geological cover layer at different depths.

[0006] Preferably, when determining the ground construction scope of the artificial geological cover layer, the mine rock movement angle is first determined based on the specific mine engineering geological conditions, and the specific mine engineering geological conditions include: drilling geological data, rock mechanical properties data, mining operation procedure data, and then the ground construction scope of the artificial geological cover layer is determined based on the mine rock movement angle; when determining the permeability coefficient and thickness of the artificial geological cover layer, first determine the theoretical target values ​​of the permeability coefficient and thickness of the artificial geological cover layer based on the pressure level of CO2 in the mining space and the formation mechanical parameters, and then conduct a CO2 permeability test, and perform numerical simulation based on the experimental results and the mine engineering geological conditions to verify or correct the target values ​​of the permeability coefficient and thickness.

[0007] Preferably, the grouting material is ultrafine cement-fly ash slurry, and the particle size of the ultrafine cement is at least 1200 mesh.

[0008] Preferably, when determining the grouting material ratio, it is necessary to first master the physical and mechanical properties of the ultrafine cement-fly ash slurry material through indoor tests, and then determine the technical indicators of the fly ash dosage, the water-cement ratio of the slurry, and the compressive strength of the stone body.

[0009] Preferably, the design interval of the grouting holes is determined according to the diffusion radius of the slurry, and the diffusion radius of the slurry is estimated according to the columnar slurry diffusion theory.

[0010] Preferably, after grouting at different depths within the range of the artificial geological cover is completed, the CO2 leakage of the artificial geological cover is monitored, including monitoring of the soil CO2 concentration and microseismic events in the artificial geological cover area.

[0011] Preferably, when monitoring the soil CO2 concentration of the artificial geological cover layer, the monitoring is performed by arranging soil CO2 concentration monitoring equipment around the grouting holes.

[0012] Preferably, when monitoring microseismic events in the artificial geological cover area, microseismic signal monitoring stations should be arranged based on the range of the artificial geological cover to carry out joint well-ground microseismic monitoring.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows: the construction method of an artificial geological cover layer for carbon dioxide storage of the present invention determines the position of the key layer of the overburden by using the key layer discrimination method, calculates the height of the overburden collapse cracks in combination with the empirical formula, and establishes a numerical calculation model to simulate the development law of overburden cracks caused by coal seam mining in the artificial geological cover layer area, and then combines the theoretical calculation and numerical simulation results to set the artificial geological cover layer position at the position of the key layer above the collapse crack zone, thereby preventing the collapse crack zone from affecting the stability of CO2 storage, and improving the density of the original cover layer overlying the mining space. The sealing, integrity and continuity of the artificial geological cover layer are enhanced, and the grouting material is injected into the geological cover layer through the grouting pipe on the ground. Since the artificial geological cover layer needs a certain thickness, grouting is carried out at different depths within the artificial geological cover layer to form a "composite" artificial geological cover layer with the original geological cover layer, which can meet the geological conditions of sealing, integrity and continuity required for CO2 storage, thereby increasing the geological storage capacity of CO2 coal mine mining space, and making the application scope of CO2 coal mine mining space geological storage technology more extensive. This method has important engineering significance for the promotion and application of CO2 coal mine mining space geological storage technology.

[0014] The present invention increases the diffusion range of the grouting slurry and the permeability and stability of the rock mass after grouting reinforcement by setting the particle size, water-cement ratio and grouting pressure of the grouting slurry. According to the key layer theory, the artificial geological cover layer is selected at the key layer and above, which is beneficial to the stability of the artificial geological cover layer in the later stage. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 Schematic diagram of the ground construction scope of the artificial geological cover layer.

[0016] Figure 2 Schematic diagram of grouting of artificial geological cover. DETAILED DESCRIPTION

[0017] The following is combined with Figure 1 and Figure 2 , the specific implementation of the present invention is described in detail, but it should be understood that the protection scope of the present invention is not limited by the specific implementation. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0018] like Figure 1 and Figure 2 As shown, the present invention provides a construction method for an artificial geological cover layer for carbon dioxide storage, comprising the following steps: S01: Determine the construction parameters of the artificial geological cover layer, including the ground construction scope of the artificial geological cover layer, the permeability coefficient and thickness of the artificial geological cover layer; S02: Determine the position of the artificial geological cover layer in the mining space, determine the position of the key layer of the overburden rock by using the key layer identification method according to the drilling geological data of the mining area, calculate the height of the overburden rock collapse fracture zone, and use geotechnical engineering software to establish a numerical calculation model to simulate the development law of overburden rock fractures caused by coal seam mining in the artificial geological cover layer area. Combined with theoretical calculation and numerical simulation results, the position of the artificial geological cover layer is set above the overburden rock collapse fracture zone; S03: According to the different lithologies within the geological cover layer, the following grouting parameters are determined: the layout and size of the ground grouting holes, the proportion and particle size of the grouting materials, and the grouting pressure; S04: within the range of the artificial geological cover layer, grouting is performed on the artificial geological cover layer at different depths.

[0019] The working principle of the above embodiment is briefly described: Collect geological exploration data and production technology data within the mining range of the mine where CO2 geological storage is planned, understand the engineering geological conditions and whether there are special geological structures in the area in detail, master the lithology and spatial distribution of each rock layer, and determine the basic mechanical properties of the overburden. Understand the mining technical conditions of the mining face, the layout of the recovery tunnel, the production system, and the mining situation in the adjacent area. Based on the above-mentioned survey results of the mine where CO2 geological storage is planned, analyze the lithology, integrity and continuity of the overburden in the goaf area, and master the overburden damage characteristics and rock movement laws (overburden collapse range and collapse height) of the mining space through empirical formula calculation and numerical simulation research, and determine the parameters such as the position, permeability, thickness and mining influence range of the artificial geological cover layer that meets the requirements of geological storage of CO2 coal mining space, so as to provide a basis for the subsequent ground grouting reinforcement to form an artificial geological cover layer.

[0020] The mining space left over after coal mining is used for geological storage of CO2. In order to prevent CO2 leakage through infiltration and diffusion, the permeability coefficient and thickness of the artificially modified geological cover layer need to be determined according to the CO2 gas pressure stored in the mining space. At the same time, in order to ensure the integrity and continuity of the artificial geological cover layer, the ground construction scope of the artificial geological cover layer is determined according to the rock movement angle.

[0021] Artificial geological cover should try to avoid the mining crack development area to ensure the integrity and stability of the cover. Therefore, the present invention uses the key layer identification method to determine the position of the key layer of the overburden according to the drilling geological data of the mining area, uses the empirical formula to calculate the height of the overburden collapse crack, and uses the geotechnical engineering software UEDC (universal discrete element method program) to establish a numerical calculation model to simulate the development law of overburden cracks caused by coal seam mining in the artificial geological cover area. Combining the theoretical calculation and numerical simulation results, the artificial geological cover layer is set at the key layer position above the collapse crack zone.

[0022] According to the requirements and stratigraphic positions of the artificial geological cover layer determined in the previous steps, the layout and size of the ground grouting holes, the ratio and particle size of the grouting materials, and the grouting pressure are determined for the different lithologies within the stratigraphic range of the geological cover layer to ensure the diffusion range of the grouting slurry and the sealing effect of the artificial geological cover layer.

[0023] The specific parameters are determined as follows: a. Grouting material selection Due to the functionality of the artificial sealed geological cap layer, its ground grouting reinforcement project has the dual functions of anti-seepage and consolidation, improving the sealing and integrity of the original rock formation. When using ground grouting to transport slurry over long distances, the setting time of the grouting slurry needs to be given special consideration, which limits the use of most chemical slurries and slurry accelerators. Therefore, the present invention uses ultrafine cement-fly ash slurry (ultrafine cement at least 1200 mesh) as the grouting material.

[0024] b. Determination of grouting material ratio When using ultrafine cement-fly ash slurry as grouting material, it is necessary to master the physical and mechanical properties of the ultrafine cement-fly ash slurry material through indoor tests, determine the relevant technical indicators such as the dosage of fly ash, the water-cement ratio of the slurry, and the compressive strength of the stone body, so as to provide a basis and reference for the selection of the grouting slurry ratio.

[0025] c. Determination of grouting pressure The grouting pressure provides the kinetic energy required for the slurry to penetrate, flow, and diffuse in the rock mass voids, but the higher the grouting pressure is, the better. Excessive grouting pressure may change the nature of the grouting, from penetration grouting to splitting grouting, causing secondary damage to the grouting rock mass.

[0026] When determining the grouting pressure, the grouting pressure can be calculated by the following formula: ; Where: P —hole grouting pressure, MPa; H —is the depth from the grouting section to the grouting hole.

[0027] Assuming that the burial depth of the grouting layer is about 550 m and considering that the deadweight pressure of the slurry column is about 6 MPa, the grouting pressure range is designed to be 6 MPa~17 MPa.

[0028] d. Grouting hole location layout The spacing of the ground grouting holes is designed according to the slurry diffusion radius. The slurry diffusion radius can be estimated according to the columnar slurry diffusion theory. The calculation formula is as follows: ; Where: r-slurry diffusion radius, cm; t- Grouting time, s; h - Grouting pressure head, cm; n - Porosity of the injected carrier; - Ratio of slurry viscosity to water viscosity; k - Permeability coefficient of the injected carrier; In order to ensure the grouting effect, the spacing between the grouting holes can be appropriately reduced, and the location of the grouting holes can be selected according to the actual terrain on site.

[0029] A pressure pump is used on the ground to inject grouting material into the geological cover layer through a grouting pipe. Since the artificial geological cover layer requires a certain thickness, grouting is carried out at different depths within the range of the artificial geological cover layer to form a "composite" artificial geological cover layer with the original geological cover layer to meet the requirements for geological storage of CO2 in coal mine mining space.

[0030] When the key layer identification method is used to determine the position of the key layer of the overburden, the calculation formula is: ; ; In the formula— , Considering the n Layer and n When adding +1 layer of rock, the load borne by the first layer of hard rock is KPa.

[0031] ——No. i The elastic modulus of the rock layer, in MPa; ——No. i The thickness of the rock layer, in m; ——No. i The gravity density of the rock layer, the unit is KN / m3.

[0032] By judging layer by layer from bottom to top, the hard rock layer that is most likely to become the key layer and its corresponding rock layer number can be determined, and then the breaking distance of each hard rock layer can be calculated to determine whether the hard rock layer is the key layer and determine the position of the key layer.

[0033] The construction method of the artificial geological cover for carbon dioxide storage of the present invention performs grouting reinforcement on a certain layer or multiple layers of rock strata in the overlying rock strata in the goaf area formed after the mining of the coal resource well through ground drilling, thereby improving the sealing and stability of the rock strata in this range, forming an artificial geological cover layer, ensuring that the goaf area of ​​the coal seam can form a sealed space, and finally realizing the geological storage of CO2 in the coal mine mining space.

[0034] On the basis of the above embodiments, in order to obtain a "final determined value" that meets the on-site sealing requirements of the mine and is constructible.

[0035] like Figure 1 and Figure 2 As shown, when determining the ground construction scope of the artificial geological cover layer, the mine rock movement angle is first determined according to the specific mine engineering geological conditions, and the specific mine engineering geological conditions include: drilling geological data, rock mechanical properties data, and mining operation procedures data, and then the ground construction scope of the artificial geological cover layer is determined according to the mine rock movement angle; when determining the permeability coefficient and thickness of the artificial geological cover layer, the target values ​​of the theoretical permeability coefficient and thickness of the artificial geological cover layer are first determined according to the pressure level of CO2 in the mining space and the formation mechanical parameters, and then a CO2 permeability test is conducted. According to the experimental results and the mine engineering geological conditions, COMSOL (multi-physics field simulation software) numerical simulation is performed to verify or correct the target values ​​of the permeability coefficient and thickness. When determining the permeability coefficient and thickness of the artificial geological cover layer, the first step is to deduce a "target permeability coefficient and thickness" range from the perspective of theory or design based on the pressure level of CO2 in the mining space, formation mechanics and other parameters. The second step is the experimental and numerical verification process, which involves conducting CO2 permeability tests under laboratory conditions, combining the test results with the actual geological conditions of the mining space, and then using COMSOL numerical simulation to verify or correct the target values ​​of the permeability coefficient and thickness.

[0036] In summary, the first step (preliminary parameter determination) is more at the level of theoretical design or engineering plan, defining the target value based on macro parameters such as CO2 pressure in the mining space, and proposing "what thickness and permeability range we need".

[0037] The second step (experiments + numerical verification) is to bring the above-mentioned target permeability coefficient and thickness range into a real or quasi-real environment (experiments and numerical simulations), verify and correct the target permeability coefficient and thickness range through measurement and simulation, and obtain the final "permeability coefficient and thickness range" that can meet the mine on-site sealing needs and is constructible.

[0038] like Figure 1 As shown, when simulating the development law of overburden cracks caused by coal seam mining in the artificial geological cover layer area, it is necessary to use geotechnical engineering software to establish a numerical simulation model to simulate the development law of overburden cracks.

[0039] The Specification for Coal Pillar Retention and Coal Mining in Buildings, Water Bodies, Railways and Main Wells and Lanes includes the height of the collapse fracture zone corresponding to the common overburden lithology ( ) The empirical calculation formula can be used as a reference value for calculating the crack height.

[0040] Empirical calculation formula for collapse fracture zone height:

[0041] Where: - Coal seam thickness Furthermore, a numerical calculation model was established using UDEC to simulate the development law of overburden cracks caused by coal mining in the artificial geological cover layer area. Combining theoretical calculations with numerical simulation results, the impact height of mining cracks was determined, and the position of the artificial geological cover layer was determined to be outside the impact range of mining cracks.

[0042] As a preferred solution, Figure 1 and Figure 2 As shown, the grouting material is ultrafine cement-fly ash slurry, and the particle size of the ultrafine cement is at least 1200 meshes. Using ultrafine cement-fly ash slurry as a grouting material and controlling the particle size of the ultrafine cement can improve the diffusion range of the slurry and the permeability and stability of the rock mass after grouting reinforcement.

[0043] As a preferred solution, when determining the grouting material ratio, it is necessary to first master the physical and mechanical properties of the ultrafine cement-fly ash slurry material through indoor tests, and then determine the technical indicators of the fly ash dosage, the water-cement ratio of the slurry, and the compressive strength of the stone body. Various mechanical tests are carried out on the ultrafine cement-fly ash slurry material indoors to master the physical and mechanical properties of the ultrafine cement-fly ash slurry material under different ratios, and then determine the relevant technical indicators of the fly ash dosage, the water-cement ratio of the slurry, and the compressive strength of the stone body with the best mechanical properties, so as to further improve the permeability and stability of the rock mass after grouting reinforcement.

[0044] As a preferred solution, Figure 2 As shown, the design interval of the grouting holes is determined according to the diffusion radius of the slurry, and the diffusion radius of the slurry is estimated according to the columnar slurry diffusion theory. The diffusion radius of the slurry is estimated according to the columnar slurry diffusion theory, and the design interval of the grouting holes is determined according to the diffusion radius of the slurry, thereby determining the layout of the ground grouting holes, which can ensure that the layout of the grouting holes is more reasonable.

[0045] As a preferred solution, Figure 2As shown, after grouting at different depths within the range of the artificial geological cover layer, the CO2 leakage monitoring of the artificial geological cover layer is carried out, including the monitoring of the soil CO2 concentration and the microseismic events in the artificial geological cover layer area. After the grouting of the artificial geological cover layer is completed, in order to prevent the CO2 under the sealing of the mining space from leaking through the cover layer, the CO2 leakage monitoring of the artificial geological cover layer is carried out, mainly including the monitoring of the soil CO2 concentration and the microseismic events in the artificial geological cover layer area. The grouting hole is the location where gas leakage is most likely to occur. After the grouting is completed, the soil CO2 concentration monitoring equipment is arranged around the grouting hole. The microseismic event monitoring point is based on the range of the artificial geological cover layer, and the well-ground joint microseismic monitoring is carried out to monitor the microseismic events during the geological sealing of CO2 in the mining space, and timely analyze the causes of the microseismic events.

[0046] As a preferred solution, Figure 2 As shown, when monitoring the soil CO2 concentration of the artificial geological cover layer, the soil CO2 concentration monitoring equipment is arranged around the grouting hole for monitoring. By arranging the soil CO2 concentration monitoring equipment around the grouting hole to monitor the soil CO2 concentration of the artificial geological cover layer in real time, the CO2 leakage of the artificial geological cover layer can be effectively prevented.

[0047] As a preferred solution, Figure 2 As shown, when monitoring microseismic events in the artificial geological cover area, microseismic signal monitoring stations should be arranged based on the scope of the artificial geological cover to carry out joint well-ground microseismic monitoring.

[0048] Determination of grouting parameters for artificial geological cover layer: According to the requirements and stratigraphic position of the artificial geological cover layer determined in the previous steps, the grouting parameters such as the arrangement of ground grouting holes, the size of grouting holes, the particle size of grouting materials, the ratio of grouting materials, and the grouting pressure are determined for different lithologies within the stratigraphic range of the geological cover layer to ensure the diffusion range of the grouting slurry and the sealing effect of the artificial geological cover layer.

[0049] While the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that many changes, modifications, substitutions and variations can be made to the embodiments without departing from the principles and spirit of the invention.

Claims

1. A construction method for an artificial geological cover for carbon dioxide storage, characterized in that: The following steps are involved: S01: Determine the construction parameters of the artificial geological cover layer, including the ground construction scope of the artificial geological cover layer, the permeability coefficient and thickness of the artificial geological cover layer; S02: Determine the position of the artificial geological cover layer in the mining space, determine the position of the key layer of the overburden rock by using the key layer identification method according to the drilling geological data of the mining area, calculate the height of the overburden rock collapse fracture zone, and use geotechnical engineering software to establish a numerical calculation model to simulate the development law of overburden rock fractures caused by coal seam mining in the artificial geological cover layer area. Combined with theoretical calculation and numerical simulation results, the position of the artificial geological cover layer is set above the overburden rock collapse fracture zone; S03: According to the different lithologies within the geological cover layer, the following grouting parameters are determined: the layout and size of the ground grouting holes, the proportion and particle size of the grouting materials, and the grouting pressure; S04: within the range of the artificial geological cover layer, grouting is performed on the artificial geological cover layer at different depths.

2. The construction method of an artificial geological cover for carbon dioxide storage according to claim 1, characterized in that: When determining the ground construction scope of the artificial geological cover layer, the mine rock movement angle is first determined according to the specific mine engineering geological conditions, and the specific mine engineering geological conditions include: drilling geological data, rock mechanical properties data, mining operation procedure data, and then the ground construction scope of the artificial geological cover layer is determined according to the mine rock movement angle; when determining the permeability coefficient and thickness of the artificial geological cover layer, first determine the theoretical target values ​​of the permeability coefficient and thickness of the artificial geological cover layer according to the pressure level of CO2 in the mining space and the formation mechanical parameters, and then conduct a CO2 permeability test, and conduct numerical simulation based on the experimental results and the mine engineering geological conditions to verify or correct the target values ​​of the permeability coefficient and thickness.

3. The construction method of an artificial geological cover for carbon dioxide storage according to claim 1, characterized in that: The grouting material is ultrafine cement-fly ash slurry, and the particle size of the ultrafine cement is at least 1200 meshes.

4. The construction method of an artificial geological cover for carbon dioxide storage according to claim 3, characterized in that: When determining the grouting material ratio, it is necessary to first master the physical and mechanical properties of the ultrafine cement-fly ash slurry material through indoor tests, and then determine the technical indicators of the fly ash dosage, the water-cement ratio of the slurry, and the compressive strength of the stone body.

5. The construction method of an artificial geological cover for carbon dioxide storage according to claim 1, characterized in that: The design interval of the grouting holes is determined according to the diffusion radius of the slurry, and the diffusion radius of the slurry is estimated according to the columnar slurry diffusion theory.

6. The construction method of an artificial geological cover for carbon dioxide storage according to claim 1, characterized in that: After grouting at different depths within the artificial geological cover layer is completed, the CO2 leakage of the artificial geological cover layer is monitored, including the monitoring of soil CO2 concentration and microseismic events in the artificial geological cover layer area.

7. The construction method of an artificial geological cover for carbon dioxide storage according to claim 6, characterized in that: When monitoring the soil CO2 concentration of the artificial geological cover layer, soil CO2 concentration monitoring equipment is arranged around the grouting holes for monitoring.

8. The construction method of an artificial geological cover for carbon dioxide storage according to claim 6, characterized in that: When monitoring microseismic events in artificial geological cover areas, microseismic signal monitoring stations should be arranged based on the scope of the artificial geological cover to carry out joint well-ground microseismic monitoring.

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