Research method of efficiency and influencing factors of carbon dioxide geological storage in abandoned coal mine

Abstract

The application discloses a research method for carbon dioxide geological storage efficiency and influencing factors of abandoned coal mines, relates to the technical field of abandoned mine resource development and utilization and environmental protection, and comprises the following steps: establishing a mine geological structure geometric model for carbon dioxide geological storage based on the coal seam geological structure and mining conditions of the to-be-tested abandoned coal mine; constructing a simulation experiment model according to the mine geological structure geometric model; obtaining carbon dioxide reserves and carbon dioxide flow distribution based on the simulation experiment model according to a carbon dioxide coal body deformation control equation, a carbon dioxide migration equation, coal mine parameters and a carbon dioxide storage target; and obtaining carbon dioxide geological storage efficiency and carbon dioxide geological storage influencing factors according to the carbon dioxide reserves and the carbon dioxide flow distribution. The application realizes the testing of the geological storage efficiency and the detection of the influences generated by the geological storage.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of abandoned mine resource development and utilization and environmental protection, in particular to a research method for abandoned coal mine CO2 geological storage efficiency and influencing factors. BACKGROUND

[0002] More than 90% of coal mines in China currently use underground mining, and abandoned mines left by non-minable underground coal mines and underground mining provide good congenital conditions for CO2 geological storage. With the deepening of China's de-capacity and energy supply-side structural reform, using non-minable coal seams and abandoned mines for CO2 geological storage not only can alleviate the greenhouse effect, but also can develop mine gas or space resources for the second time, maximize the avoidance of resource waste, promote sustainable development, and the effect will be very remarkable.

[0003] Currently, relevant scholars have developed methods for using non-minable coal seams or abandoned mines for CO2 storage, such as a CO2 block storage method based on abandoned mine goaf (CN115306479A) and a method for storing CO2 in coal mine abandoned mine goaf (CN109812293A). The above methods use abandoned mine goaf as a CO2 storage place, have strong environmental adaptability, do not require personnel to modify the abandoned mine goaf, reduce construction processes and costs, and have other advantages. For example, a CO2 storage method based on thick unconsolidated layer deep goaf space (CN115199331A) has the advantages of reducing the sealing difficulty of abandoned mines and improving the effect of storing CO2 in abandoned mines. However, the above patents mainly study the storage method of CO2 in abandoned mines or non-minable coal seams, and it is difficult to evaluate the CO2 geological storage efficiency of abandoned mines, and it is impossible to confirm the influencing factors of CO2 geological storage.

[0004] In recent years, relevant scholars have conducted basic research on the mechanical properties of coal and CO2 coupling, the seepage properties of CO2, and the feasibility of CO2 geological storage in abandoned coal mines, and have made some progress. However, how to comprehensively consider the large amount of experimental laws obtained and summarized in the laboratory, establish a multi-field coupling model for CO2 geological storage in abandoned coal mines, and deeply analyze the changes in coal seams after CO2 injection, gas flow rules, storage efficiency, and storage capacity is unknown, and the influencing factors of CO2 storage efficiency are unknown. SUMMARY

[0005] The purpose of the present application is to provide a research method for abandoned coal mine CO2 geological storage efficiency and influencing factors, which can realize the testing of geological storage efficiency and the detection of influencing factors of storage efficiency.

[0006] To achieve the above purpose, the present application provides the following solutions:

[0007] A research method of carbon dioxide geological storage efficiency and influencing factors of abandoned coal mine, the research method comprises:

[0008] A mine geological structure geometric model of carbon dioxide geological storage is established based on the coal seam geological structure and mining conditions of the to-be-tested abandoned coal mine;

[0009] According to the mine geological structure geometric model, a simulation experiment model is constructed;

[0010] According to the carbon dioxide coal body deformation control equation, the carbon dioxide migration equation, the coal mine parameters and the carbon dioxide storage target, the carbon dioxide storage and the carbon dioxide flow distribution are obtained based on the simulation experiment model;

[0011] According to the carbon dioxide storage and the carbon dioxide flow distribution, the carbon dioxide geological storage efficiency and the carbon dioxide geological storage influencing factors are obtained.

[0012] Optionally, the carbon dioxide coal body deformation control equation is:

[0013]

[0014] In the formula, K is the bulk modulus, F i is the body load, G is the shear modulus, α is the biot coefficient, p' is the carbon dioxide pressure, p ,i is the partial derivative of the carbon dioxide pressure in the i direction, ε s,i is the adsorption deformation degree ε s is the partial derivative of the carbon dioxide pressure in the i direction, α T is the thermal expansion coefficient of the coal rock mass, T ,i is the partial derivative of the temperature in the i direction, u i,kk is the second partial derivative of the i direction component of displacement in the k direction, v is the Poisson's ratio, u k,ki is the partial derivative of the k direction component of displacement in the k direction, and then the partial derivative in the i direction, F i is the body load;

[0015] In the formula, the calculation formula of the Poisson's ratio is:

[0016] ν(p)=0.272+0.326p-0.006p 2 ;

[0017] In the formula, p is the carbon dioxide pressure;

[0018] The calculation formula of the bulk modulus is:

[0019] K=E / 1-2v;

[0020] In the formula, E is the strength;

[0021] The formula for calculating the strength is:

[0022] E(p) = 1.89 + 3.69e -0.64p ;

[0023] In the formula, p is the carbon dioxide pressure.

[0024] Optionally, the coal mine parameters include: elastic modulus, strength, Poisson's ratio, bulk load, carbon dioxide pressure, adsorption deformation degree, displacement, skeleton elastic modulus, bulk strain, density of coal, permeability of coal, dynamic viscosity coefficient of gas in coal, gas pressure gradient in seepage direction.

[0025] Optionally, the formula for calculating the elastic modulus is:

[0026] σ c (p) = 24.17 + 26.59e -0.41p ;

[0027] In the formula, p is the carbon dioxide pressure, and σ c is the elastic modulus.

[0028] Optionally, the carbon dioxide storage target includes: boundary conditions and initial values.

[0029] Optionally, the carbon dioxide transport equation is:

[0030]

[0031] In the formula, K s is the skeleton elastic modulus, ε L is the Langmuir volume constant, ε v is the bulk strain, P L is the Langmuir pressure constant; φ is the coal fracture degree; α is the biot coefficient; p is the carbon dioxide pressure; p a is the standard atmospheric pressure; ρ c is the density of coal; V L is the Langmuir volume constant; t is time; k is the permeability of coal; μ is the dynamic viscosity coefficient of gas in coal; gas pressure gradient in seepage direction; m is the non-Darcy seepage characteristic coefficient.

[0032] Optionally, the formula for calculating the coal fracture degree is:

[0033]

[0034] In the formula, φ0 is the initial fracture degree, c f is the compressibility coefficient of coal, and Δσ' v is the effective increment of volumetric stress of tensile stress, which is positive.

[0035] Optionally, the formula for calculating the permeability of the coal is:

[0036]

[0037] In the formula, q CO2 is the Darcy velocity vector.

[0038] According to the specific embodiments provided by the present application, the following technical effects are disclosed:

[0039] The application discloses a research method for carbon dioxide geological storage efficiency and influencing factors of abandoned coal mines.

[0040] Compared with the prior art of using unexploited coal seams or abandoned mines for carbon dioxide geological storage, the application determines the influencing factors of carbon dioxide geological storage efficiency by changing the input values in the numerical simulation solver. BRIEF DESCRIPTION OF DRAWINGS

[0041] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0042] Figure 1 The figure is a method flowchart of the present application.

[0043] Figure 2 The figure is a coal mining layout schematic diagram of the present application.

[0044] Figure 3 The figure is a two-dimensional geometric calculation diagram of the present application.

[0045] Figure 4 The figure is a carbon dioxide flow distribution schematic diagram of the present application.

[0046] Figure 5 The figure is a carbon dioxide storage amount schematic diagram of the present application under different initial permeabilities over time. DETAILED DESCRIPTION

[0047] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0048] The purpose of this invention is to provide a research method for the geological sequestration efficiency and influencing factors of carbon dioxide in abandoned coal mines, which realizes the testing of geological sequestration efficiency and the detection of influencing factors of sequestration efficiency.

[0049] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0050] like Figure 1 As shown, this invention discloses a method for studying the efficiency and influencing factors of carbon dioxide geological sequestration in abandoned coal mines. The method includes:

[0051] S1: Establish a geometric model of the geological structure of a mine for carbon dioxide geological sequestration based on the coal seam geological structure and mining conditions of the abandoned coal mine to be tested.

[0052] S2: Construct a simulation experiment model based on the geometric model of the mine's geological structure.

[0053] S3: Based on the carbon dioxide coal body deformation control equation, carbon dioxide transport equation, coal mine parameters, and carbon dioxide sequestration target, the carbon dioxide reserves and carbon dioxide flow distribution are obtained based on the simulation experimental model.

[0054] Step S3 specifically involves: inputting the carbon dioxide coal deformation control equation into the solid mechanics module of the COMSOL with MATLAB numerical simulation solver; inputting the carbon dioxide transport equation into the Darcy's law module of the COMSOL with MATLAB numerical simulation solver; inputting coal mine parameters: elastic modulus, strength, Poisson's ratio, volume load, carbon dioxide pressure, degree of adsorption deformation, displacement, skeletal elastic modulus, volume strain, coal density, coal permeability, dynamic viscosity coefficient of gas in coal, and gas pressure gradient in the seepage direction; refining the mesh size; performing transient analysis and solving; and obtaining the carbon dioxide reserves and carbon dioxide flow distribution based on the simulation experimental model according to the carbon dioxide sequestration target.

[0055] S4: Based on carbon dioxide reserves and carbon dioxide flow distribution, we obtain the efficiency of carbon dioxide geological sequestration and the influencing factors of carbon dioxide geological sequestration.

[0056] In step S1, based on Figure 2 and Figure 3A geological structure model of a mine can be created using AutoCAD.

[0057] In step S2, a simulation experimental model can be constructed by importing the mine geological structure model into the COMSOFT WITH MATLAB numerical simulation solver.

[0058] In step S3, the constitutive relationship of the coal body considering the effect of carbon dioxide is calculated based on the elastic deformation theory; specifically, the elastic deformation relationship of the coal is as follows:

[0059] σ ij =λε kk δ ij +2Gε ij .

[0060] In the formula, λ is the lateral pressure coefficient; G is the shear modulus; ε kk The first stress invariant; δ ij For Kronecker notation, when i = j, δ ij =1, when i≠j, δ ij =0; σ ij The stress on the iOj surface; ε ij The strain is on the iOj surface.

[0061] Where λ=Ev / [(1+v)(1-2v)]; E is the elastic modulus; v is Poisson's ratio. G=E / 2(1+v).

[0062] Considering the softening effect of carbon dioxide adsorption, the following can be obtained:

[0063] dσ ij (p)=dλ(p)ε kk (p)δ ij +λ(p)dε kk (p)δ ij +2ε ij (p)dG(p)+2G(p)dε ij (p).

[0064] The constitutive relationship of the coal body affected by carbon dioxide is specifically as follows:

[0065] dσ x = (1.42 + 2.77e) -0.64p )d(ε kk +ε x )-1.77(ε kk +ε x )e -0.64p dp.

[0066] dσ y = (1.42 + 2.77e) -0.64p )d(εkk +ε y )-1.77(ε kk +ε y )e -0.64p dp.

[0067] dσ z = (1.42 + 2.77e) -0.64p )d(ε kk +ε z )-1.77(ε kk +ε z )e -0.64p dp.

[0068] dτ xy = (1.42 + 2.77e) -0.64p )dγ xy -1.77γ xy e -0.64p dp.

[0069] dτ yz = (1.42 + 2.77e) -0.64p )dγ yz -1.77γ yz e -0.64p dp.

[0070] dτ zx = (1.42 + 2.77e) -0.64p )dγ zx -1.77γ zx e -0.64p dp.

[0071] In the formula, σ x σ y σ z ε represents the normal stresses xOy, yOz, and zOx of any unit cell within carbon dioxide-rich coal rock; x ε y ε z τ represents the normal strain of any unit cell xOy, yOz, and zOx within the carbon dioxide-rich coal rock; xy τ yz τ zx ε represents the shear stress on the xOy, yOz, and zOx surfaces, respectively; p is the carbon dioxide pressure; ε kk γ is the first stress invariant; xy γ yz γ yz These are the displacement components on the xOy, yOz, and zOx planes, respectively. The Poisson's ratio is a common value of 0.33.

[0072] in,

[0073] The formula for calculating effective stress is: σ' ij =σ ij +αpδ ij .

[0074] In the formula, σ' ij α represents the effective stress; α is the biot coefficient; the biot coefficient is set to 1 in the examples.

[0075] The deformation control equation for carbon dioxide-rich coal is:

[0076]

[0077] In the formula, K is the bulk modulus, and F is the mass modulus. i Let G be the body load, G be the shear modulus, p' be the carbon dioxide pressure, and p ,i Let ε be the partial derivative of the carbon dioxide pressure in the i-direction. s,i The degree of adsorption deformation ε s The partial derivative in the i-direction, α T T is the coefficient of thermal expansion of the coal and rock mass. ,i Let u be the partial derivative of temperature in the i-direction. i,kk Let v be the second partial derivative of the displacement in the i-direction component with respect to the k-direction, v be Poisson's ratio, and u be the partial derivative of the displacement in the i-direction component with respect to the k-direction component. k,ki Let F be the partial derivative of the displacement in the k-direction component in the k-direction, and then the partial derivative in the i-direction. i For body load.

[0078] The formula for calculating Poisson's ratio is as follows.

[0079] ν(p) = 0.272 + 0.326p - 0.006p 2 .

[0080] In the formula, p is the carbon dioxide pressure.

[0081] The formula for calculating the bulk modulus is:

[0082] K = E / (1-2v);

[0083] In the formula, E represents intensity.

[0084] The formula for calculating the strength is:

[0085] E(p) = 1.89 + 3.69e -0.64p .

[0086] In the formula, p is the carbon dioxide pressure.

[0087] In step S3, the coal mine parameters include: elastic modulus, strength, Poisson's ratio, volume load, carbon dioxide pressure, degree of adsorption deformation, displacement, skeletal elastic modulus, volume strain, coal density, coal permeability, dynamic viscosity coefficient of gas in coal, and gas pressure gradient in the seepage direction.

[0088] The formula for calculating the elastic modulus is as follows:

[0089] σ c (p) = 24.17 + 26.59e -0.41p ;

[0090] In the formula, σ c It is a spring mold.

[0091] The carbon dioxide sequestration objectives include: boundary conditions and initial values.

[0092] By conducting coal seam seepage experiments, the seepage law of coal was obtained. Based on the non-Darcy seepage model, the formula for calculating the permeability of coal is as follows:

[0093]

[0094] In the formula, q CO2 Darcy velocity vector; μ is the dynamic viscosity coefficient of gas in coal; Gas pressure gradient in the direction of seepage; m is the non-Darcy seepage characteristic coefficient; k is the permeability of coal.

[0095] The formula for calculating the porosity of the coal is as follows:

[0096]

[0097] In the formula, φ0 is the initial fracture degree, φ is the fracture degree of the coal, and c f Let Δσ' be the compressibility coefficient of coal. v The effective increment of the volumetric stress for tensile stress is positive.

[0098] Establish a coal permeability model:

[0099]

[0100] The carbon dioxide transport equilibrium can be expressed using the mass balance law, specifically as follows:

[0101]

[0102] In the formula, This represents the partial derivative of the carbon dioxide mass with respect to time. Let ρ be the mass of carbon dioxide, t be time, and ρ be the mass of carbon dioxide. g The pressure is the density of the gas at the pressure of carbon dioxide. Let Q be the Darcy velocity vector.s This refers to the consumption and sources of the gas.

[0103] Where, m CO2 =ρ g φ+ρ c ρ ga V CO2 In the formula, ρ ga ρ is the density of the gas at standard atmospheric pressure. Further, ρ g =ρ ga p / p a ;p a Standard atmospheric pressure.

[0104] Expanding the equation representing the carbon dioxide transport equilibrium using the mass balance law, the carbon dioxide transport equation is as follows:

[0105]

[0106] In the formula, K s For the elastic modulus of the skeleton, ε L ε is the Langmuir volume constant. v For volumetric strain, P L p is the Langmuir pressure constant. a Standard atmospheric pressure; ρ c V is the density of coal. L t is the Langmuir volume constant; t is time; k is the permeability of coal.

[0107] In a specific embodiment, by conducting on-site investigations of the geological and mining conditions of the target coal seam, testing the physical and mechanical properties of the coal seam through laboratory experiments, establishing a multi-field coupled model of coal seam deformation and gas flow for carbon dioxide geological sealing, and then using a numerical simulation solver to mathematically solve the multi-field coupled model. Specific implementation examples:

[0109] Isothermal adsorption experiments of carbon dioxide on coal were conducted to obtain two sets of coal seam parameters, including the gas content per unit weight of coal and the carbon dioxide pressure. Adsorption parameters, including the Langmuir volume constant and the Langmuir pressure constant, were determined using these two sets of coal seam parameters.

[0110] The carbon dioxide pressure is determined based on the adsorption parameters and the adsorption calculation formula.

[0111] Specifically, the adsorption calculation formula is as follows:

[0112]

[0113] In the formula, V CO2 V is the gas content per unit weight of coal.L P is the Langmuir volume constant. L is the Langmuir pressure constant, and p is the carbon dioxide pressure.

[0114] Coal samples were drilled from the target coal seam and processed into cylinders with a diameter of 50 mm and a height of 100 mm. Each coal sample was placed under different carbon dioxide pressures for adsorption for more than 48 hours, and mechanical property tests were conducted to obtain mechanical parameters. These mechanical parameters included stress-strain curves, elastic modulus, strength, and Poisson's ratio. The mechanical property tests were performed using a triaxial multi-field coupled rock testing system, with displacement-controlled loading at a rate of 0.05 mm / min until the coal sample failed.

[0115] like Figure 2 and Figure 3 As shown, based on the target coal seam, a two-dimensional geometric calculation diagram is selected from the vertical section of the remaining coal pillar perpendicular to the mining direction. The coal pillar width is 24m and the coal seam thickness is 6m. AutoCAD is used to establish a geometric model of the mine's geological structure for carbon dioxide geological storage.

[0116] Based on the carbon dioxide coal body deformation control equation, carbon dioxide transport equation, coal mine parameters, and carbon dioxide sequestration targets, the carbon dioxide reserves and carbon dioxide flow distribution are obtained using a simulation experiment model. The initial value in the carbon dioxide sequestration target is the initial permeability.

[0117] like Figure 4 The diagram shows the distribution of carbon dioxide flow within the coal pillar 5 days after carbon dioxide injection, with the arrows indicating relative flow velocities. The maximum flow velocity is located in the region with a large carbon dioxide pressure gradient and migrates towards the center of the coal pillar with continuous carbon dioxide injection. This can be determined based on... Figure 4 The rate at which carbon dioxide is stored is obtained.

[0118] like Figure 5 The figure shows the evolution of carbon dioxide reserves in abandoned coal pillars with different initial permeability over time. With initial permeability ranging from 0.05 mD to 1 mD, and for the same storage capacity, the gas injection time is shortened from 460 days to 20 days, indicating improved gas injection efficiency. This can be based on... Figure 5 The study determined the carbon dioxide reserves and their impact on the efficiency of carbon dioxide geological sequestration.

[0119] according to Figure 5 The variation of carbon dioxide reserves over time can determine the maximum carbon dioxide reserves, and the initial permeability is the influencing factor for determining carbon dioxide geological sequestration. The carbon dioxide geological sequestration efficiency can be obtained based on the carbon dioxide storage rate and the maximum carbon dioxide reserves. The initial value includes, but is not limited to, the initial permeability.

[0120] This invention establishes a multi-field coupled model of coal seam deformation and gas flow for carbon dioxide geological storage by conducting field investigations of the geological mining conditions of the target coal seam, testing the physical and mechanical properties of the coal seam through laboratory experiments, and then mathematically solving the multi-field coupled model using a numerical simulation solver. Ultimately, it obtains the carbon dioxide reserves, carbon dioxide storage rate, and the degree of deformation of the storage space. Furthermore, it can determine the influencing factors on the efficiency of carbon dioxide geological storage based on different initial values ​​input to the numerical simulation solver.

[0121] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0122] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for studying the efficiency and influencing factors of carbon dioxide geological sequestration in abandoned coal mines, characterized in that, The research methods include: A geometric model of the geological structure of a mine for carbon dioxide geological sequestration was established based on the coal seam geological structure and mining conditions of the abandoned coal mine to be tested. Based on the geometric model of the mine's geological structure, a simulation experimental model was constructed; Based on the carbon dioxide coal body deformation control equation, carbon dioxide transport equation, coal mine parameters, and carbon dioxide sequestration target, the carbon dioxide reserves and carbon dioxide flow distribution are obtained based on the simulation experimental model. Based on carbon dioxide reserves and carbon dioxide flow distribution, we obtained the efficiency of carbon dioxide geological sequestration and the influencing factors of carbon dioxide geological sequestration. Considering the softening effect of carbon dioxide adsorption on parameters, the deformation control equation for the carbon dioxide-coal body is: In the formula, K is the bulk modulus, and F is the mass modulus. i Let G be the volume load, G be the shear modulus, α be the biot coefficient, p' be the carbon dioxide pressure, p,i be the partial derivative of the carbon dioxide pressure in the i-direction, and ε be the partial derivative of the carbon dioxide pressure in the i-direction. s,i The degree of adsorption deformation ε s The partial derivative in the i-direction, α T Let Ti be the coefficient of thermal expansion of the coal and rock mass, Ti be the partial derivative of temperature in the i-th direction, and ui be the coefficient of thermal expansion of the coal and rock mass. i,kk Let v be the second partial derivative of the displacement in the i-direction component with respect to the k-direction, v be Poisson's ratio, and u be the partial derivative of the displacement in the i-direction component with respect to the k-direction component. k,ki Let F be the partial derivative of the displacement in the k-direction component in the k-direction, and then the partial derivative in the i-direction. i For volume load; The formula for calculating Poisson's ratio is: n(p)=0.272+0.326p-0.006p 2 ; In the formula, p is the carbon dioxide pressure; The formula for calculating the bulk modulus is: K = E / (1-2v); In the formula, E represents strength; The formula for calculating the strength is: E(p)=1.89+3.69e -0.64p ; The coal mine parameters include: elastic modulus, strength, Poisson's ratio, volume load, carbon dioxide pressure, degree of adsorption deformation, displacement, skeletal elastic modulus, volume strain, coal density, coal permeability, dynamic viscosity coefficient of gas in coal, and gas pressure gradient in the seepage direction. The formula for calculating the elastic modulus is: s c (p)=24.17+26.59e -0.41p ; In the formula, p is the carbon dioxide pressure, σ c It is a spring mold.

2. The research method for the efficiency and influencing factors of carbon dioxide geological sequestration in abandoned coal mines according to claim 1, characterized in that, The carbon dioxide sequestration objectives include: boundary conditions and initial values.

3. The research method for the efficiency and influencing factors of carbon dioxide geological sequestration in abandoned coal mines according to claim 1, characterized in that, The carbon dioxide transport equation is as follows: In the formula, K s For the elastic modulus of the skeleton, ε L ε is the Langmuir volume constant. v For volumetric strain, P L φ is the Langmuir pressure constant; φ is the coal fracture degree; α is the Biot coefficient; p is the carbon dioxide pressure; p a Standard atmospheric pressure; ρ c V is the density of coal. L is the Langmuir volume constant; t is time; k is the permeability of coal; μ is the dynamic viscosity coefficient of gas in coal; Gas pressure gradient in the seepage direction; m is the non-Darcy seepage characteristic coefficient.

4. The research method for the efficiency and influencing factors of carbon dioxide geological sequestration in abandoned coal mines according to claim 3, characterized in that, The formula for calculating the porosity of the coal is: In the formula, φ0 is the initial fracture density, and c f Let Δσ' be the compressibility coefficient of coal. v The effective increment of the volumetric stress for tensile stress is positive.

5. The research method for the efficiency and influencing factors of carbon dioxide geological sequestration in abandoned coal mines according to claim 4, characterized in that, The formula for calculating the permeability of the coal is as follows: In the formula, q CO2 This is the Darcy velocity vector.

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