A method and device for simulating the cavity evolution of underground coal gasification

Abstract

The present application provides a method and device for simulating the cavity evolution of underground coal gasification. The method includes: generating a multi-field coupling constitutive model for underground coal gasification according to a pre-constructed stress-strain model, gas migration model, chemical reaction model, and energy balance model; establishing a finite element initial model for underground coal gasification based on the multi-field coupling constitutive model; and simulating the cavity evolution process of underground coal gasification according to the actual occurrence conditions of the coal seam and the finite element initial model. The method and device for simulating the cavity evolution of underground coal gasification provided by the present application achieve a full-dimensional prediction of the cavity modeling and development process of deep underground coal gasification, can simulate the boundary characteristics of the coal seam gasification cavity under different injection conditions, determine the influence of different underground coal gasification characteristic fields on the cavity evolution law, and provide technical support for optimizing the gasification process parameters under in-situ temperature and pressure conditions.

Description

Technical Field

[0001] The present application relates to the technical field of clean coal utilization, and in particular to a cavity evolution simulation method and device for underground coal gasification. Background Art

[0002] As shallow mineral resources become exhausted, mineral mining is gradually moving deeper underground. Underground coal gasification (UCG) is one of the effective means to solve the in-situ development of deep coal. This technology is to carry out controlled combustion of underground coal in situ, and produce CO, H and other gases through pyrolysis of coal and a series of chemical reactions with oxygen, water vapor, etc. 2 , CH 4 and other combustible gases, comprehensively develop clean energy and produce chemical raw materials, and effectively utilize new technologies for deep coal and unmineable coal.

[0003] Deep underground coal gasification is a complex process involving solid-fluid-heat-chemical multi-field coupling, which requires research under the in-situ conditions of coal. In the existing technology, the research on the expansion law of the gasification zone under the interaction between gasifier and coal is mainly focused on the field of shallow underground coal gasification, while there is still a blank in the field of deep underground in-situ coal gasification, which needs to be solved urgently. Summary of the invention

[0004] In view of the problems in the prior art, the embodiments of the present application provide a method and device for simulating cavity evolution of underground coal gasification, which can at least partially solve the problems in the prior art.

[0005] In a first aspect, the present application provides a method for simulating cavity evolution of underground coal gasification, comprising:

[0006] Generate a multi-field coupled constitutive model for underground coal gasification based on the pre-built stress-strain model, gas migration model, chemical reaction model and energy balance model;

[0007] Establishing a finite element initial model of underground coal gasification according to the multi-field coupled constitutive model;

[0008] The cavity evolution process of underground coal gasification is simulated according to the actual occurrence conditions of the coal seam and the finite element initial model.

[0009] Furthermore, the steps of pre-building the stress-strain model, gas migration model, chemical reaction model and energy balance model include:

[0010] Construct a stress-strain model based on the acquired block geological parameters and rock mechanics parameters;

[0011] A gas migration model is constructed based on the obtained initial fluid parameters;

[0012] Construct a chemical reaction model based on the underground coal gasification reaction;

[0013] Construct an energy balance model based on the thermal equilibrium state.

[0014] Furthermore, the gas migration model includes a gas migration model and a steam migration model; constructing the gas migration model according to the obtained initial fluid parameters includes:

[0015] Construct the gas migration model according to the initial fluid parameters and the gas migration mechanism;

[0016] Construct the steam migration model according to the initial fluid parameters and the steam migration mechanism.

[0017] Furthermore, generating a multi-field coupling constitutive model for underground coal gasification according to the pre-constructed stress-strain model, gas migration model, chemical reaction model and energy balance model includes:

[0018] Generate a permeability evolution model according to the coal-rock porosity evolution model;

[0019] Cross-couple the stress-strain model, the gas migration model and the energy balance model by using the coal-rock porosity evolution model, the permeability evolution model, the obtained gas volume model and the ideal gas state model, and combine with the chemical reaction model to obtain the multi-field coupling constitutive model.

[0020] Furthermore, establishing a finite element initial model for underground coal gasification according to the multi-field coupling constitutive model includes:

[0021] Construct a two-dimensional geometric model according to the preset geometric parameters;

[0022] Establish the finite element initial model according to the two-dimensional geometric model and the multi-field coupling constitutive model.

[0023] Furthermore, simulating the cavity evolution process of underground coal gasification according to the actual occurrence conditions of the coal seam and the finite element initial model includes:

[0024] Generate a finite element model according to the actual occurrence conditions of the coal seam and the finite element initial model;

[0025] Use the finite element model to simulate the cavity evolution process of underground coal gasification.

[0026] Furthermore, generating a finite element model according to the actual occurrence conditions of the coal seam and the finite element initial model includes:

[0027] Generate multi-field boundary conditions according to the actual occurrence conditions of the coal seam;

[0028] Perform non - homogeneous assignment of the parameters of the initial finite - element model to obtain non - homogeneous parameters;

[0029] Input the multi - field boundary conditions and the non - homogeneous parameters into the initial finite - element model to obtain the finite - element model.

[0030] Further, the process of simulating the cavity evolution process of underground coal gasification using the finite - element model includes:

[0031] Use the finite - element model and the obtained initial in - situ stress balance parameters to determine the cavity boundary characteristics;

[0032] Determine the cavity evolution process of underground coal gasification according to the cavity boundary characteristics.

[0033] Further, before using the finite - element model and the obtained initial in - situ stress balance parameters to determine the cavity boundary characteristics, it also includes:

[0034] Establish a mechanical model according to the stress - strain model;

[0035] Perform steady - state calculation using the mechanical model to obtain the initial in - situ stress balance parameters.

[0036] In a second aspect, the present application provides a device for simulating the cavity evolution of underground coal gasification, including:

[0037] A constitutive model generation unit, configured to generate a multi - field coupling constitutive model of underground coal gasification according to a pre - constructed stress - strain model, gas migration model, chemical reaction model, and energy balance model;

[0038] An initial finite - element model establishment unit, configured to establish an initial finite - element model of underground coal gasification according to the multi - field coupling constitutive model;

[0039] A cavity evolution simulation unit, configured to simulate the cavity evolution process of underground coal gasification according to the actual occurrence conditions of the coal seam and the initial finite - element model.

[0040] Further, it also includes:

[0041] A stress - strain model construction unit, configured to construct a stress - strain model according to the obtained block geological parameters and rock mechanics parameters;

[0042] A gas migration model construction unit, configured to construct a gas migration model according to the obtained initial fluid parameters;

[0043] A chemical reaction model construction unit, configured to construct a chemical reaction model according to the underground coal gasification reaction;

[0044] An energy balance model construction unit, configured to construct an energy balance model based on the thermal equilibrium state.

[0045] Further, the gas migration model construction unit includes:

[0046] A gas migration model construction module for constructing the gas migration model according to the initial fluid parameters and the gas migration mechanism;

[0047] A water vapor migration model construction module for constructing the water vapor migration model according to the initial fluid parameters and the water vapor migration mechanism.

[0048] Further, the constitutive model generation unit includes:

[0049] A permeability evolution model generation module for generating a permeability evolution model according to the coal and rock porosity evolution model;

[0050] A constitutive model generation module for cross-coupling the stress-strain model, the gas migration model and the energy balance model by using the coal and rock porosity evolution model, the permeability evolution model, the obtained gas volume model and the ideal gas state model, and combining the chemical reaction model to obtain the multi-field coupling constitutive model.

[0051] Further, the finite element initial model establishment unit includes:

[0052] A two-dimensional geometric model construction module for constructing a two-dimensional geometric model according to preset geometric parameters;

[0053] A finite element initial model establishment module for establishing the finite element initial model according to the two-dimensional geometric model and the multi-field coupling constitutive model.

[0054] Further, the cavity evolution simulation unit includes:

[0055] A finite element model generation module for generating a finite element model according to the actual occurrence conditions of the coal seam and the finite element initial model;

[0056] A cavity evolution simulation module for simulating the cavity evolution process of underground coal gasification by using the finite element model.

[0057] Further, the finite element model generation module includes:

[0058] A multi-field boundary condition generation sub-module for generating multi-field boundary conditions according to the actual occurrence conditions of the coal seam;

[0059] A heterogeneous parameter generation sub-module for performing heterogeneous assignment on the parameters of the finite element initial model to obtain heterogeneous parameters;

[0060] A finite element model generation sub-module for inputting the multi-field boundary conditions and the heterogeneous parameters into the initial finite element model to obtain the finite element model.

[0061] Further, the cavity evolution simulation module includes:

[0062] A cavity boundary feature determination sub-module for determining cavity boundary features by using the finite element model and the obtained initial in-situ stress balance parameters;

[0063] A cavity evolution process determination sub-module for determining the cavity evolution process of underground coal gasification according to the cavity boundary features.

[0064] Further, it further includes:

[0065] A mechanical model establishment unit for establishing a mechanical model according to the stress-strain model;

[0066] A steady-state calculation unit for performing steady-state calculation by using the mechanical model to obtain the initial in-situ stress balance parameters.

[0067] In a third aspect, the present application provides a computer device, including a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the computer program, the method described in any one of the above embodiments is implemented.

[0068] In a fourth aspect, the present application provides a computer-readable storage medium storing a computer program, and when the computer program is executed by a processor, the method described in any one of the above embodiments is implemented.

[0069] In a fifth aspect, the present application provides a computer program product, including a computer program, and when the computer program is executed by a processor, the method described in any one of the above embodiments is implemented.

[0070] The cavity evolution simulation method and device for underground coal gasification provided by the present application generate a multi-field coupling constitutive model for underground coal gasification according to a pre-constructed stress-strain model, gas migration model, chemical reaction model, and energy balance model; establish an initial finite element model for underground coal gasification according to the multi-field coupling constitutive model; simulate the cavity evolution process of underground coal gasification according to the actual occurrence conditions of the coal seam and the initial finite element model, realizing full-dimensional prediction of the deep underground coal gasification cavity modeling and development process, capable of simulating the cavity boundary features of the coal seam gasification cavity under different injection conditions, determining the influence of different underground coal gasification characteristic fields on the cavity evolution law, and providing technical support for optimizing the gasification process parameters under in-situ temperature and pressure conditions. Among them, heterogeneous assignment of model parameters improves the performance of the model. Description of the Drawings

[0071] To more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0072] Figure 1 It is a schematic flowchart of a method for simulating the cavity evolution of underground coal gasification provided by an embodiment of the present application;

[0073] Figure 2 It is a schematic flowchart of a method for simulating the cavity evolution of underground coal gasification provided by an embodiment of the present application;

[0074] Figure 3 It is a schematic flowchart of a method for simulating the cavity evolution of underground coal gasification provided by an embodiment of the present application;

[0075] Figure 4 It is a schematic flowchart of a method for simulating the cavity evolution of underground coal gasification provided by an embodiment of the present application;

[0076] Figure 5 It is a schematic flowchart of a method for simulating the cavity evolution of underground coal gasification provided by an embodiment of the present application;

[0077] Figure 6 It is a schematic flowchart of a method for simulating the cavity evolution of underground coal gasification provided by an embodiment of the present application;

[0078] Figure 7 It is a schematic flowchart of a method for simulating the cavity evolution of underground coal gasification provided by an embodiment of the present application;

[0079] Figure 8 It is a schematic flowchart of a method for simulating the cavity evolution of underground coal gasification provided by an embodiment of the present application;

[0080] Figure 9 It is a schematic flowchart of a method for simulating the cavity evolution of underground coal gasification provided by an embodiment of the present application;

[0081] Figure 10 It is a schematic structural diagram of a device for simulating the cavity evolution of underground coal gasification provided by an embodiment of the present application;

[0082] Figure 11 It is a schematic structural diagram of a device for simulating the cavity evolution of underground coal gasification provided by an embodiment of the present application;

[0083] Figure 12It is a schematic structural diagram of a cavity evolution simulation device for underground coal gasification provided by an embodiment of the present application;

[0084] Figure 13 It is a schematic structural diagram of a cavity evolution simulation device for underground coal gasification provided by an embodiment of the present application;

[0085] Figure 14 It is a schematic structural diagram of a cavity evolution simulation device for underground coal gasification provided by an embodiment of the present application;

[0086] Figure 15 It is a schematic structural diagram of a cavity evolution simulation device for underground coal gasification provided by an embodiment of the present application;

[0087] Figure 16 It is a schematic structural diagram of a cavity evolution simulation device for underground coal gasification provided by an embodiment of the present application;

[0088] Figure 17 It is a schematic structural diagram of a cavity evolution simulation device for underground coal gasification provided by an embodiment of the present application;

[0089] Figure 18 It is a schematic structural diagram of a cavity evolution simulation device for underground coal gasification provided by an embodiment of the present application;

[0090] Figure 19 It is a schematic physical structure diagram of an electronic device provided by an embodiment of the present application;

[0091] Figure 20 It is a schematic diagram of the three-dimensional distribution of cavities for underground coal gasification provided by an embodiment of the present application;

[0092] Figure 21 It is a multi-physical field coupling relationship diagram for underground coal gasification provided by an embodiment of the present application;

[0093] Figure 22 It is a schematic diagram of a two-dimensional numerical model grid for underground coal gasification provided by an embodiment of the present application. Detailed implementation manners

[0094] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer and more understandable, the following further elaborates on the embodiments of the present application with reference to the accompanying drawings. Herein, the illustrative embodiments of the present application and their descriptions are used to explain the present application, but not to limit the present application. It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined arbitrarily with each other.

[0095] The following takes the server as the execution entity as an example to illustrate the specific implementation process of the cavity evolution simulation method for underground coal gasification provided by the embodiments of the present application.

[0096] Figure 1 is a schematic flowchart of a method for simulating the cavity evolution of underground coal gasification provided by an embodiment of the present application. As Figure 1 shown, the method for simulating the cavity evolution of underground coal gasification provided by the present application includes:

[0097] S101: Generate a multi-field coupling constitutive model for underground coal gasification according to a pre-constructed stress-strain model, gas migration model, chemical reaction model, and energy balance model;

[0098] S102: Establish a finite element initial model for underground coal gasification according to the multi-field coupling constitutive model;

[0099] S103: Simulate the cavity evolution process of underground coal gasification according to the actual occurrence conditions of the coal seam and the finite element initial model.

[0100] From Figure 1 the shown process, it can be seen that for the method for simulating the cavity evolution of underground coal gasification provided by the present application, a multi-field coupling constitutive model for underground coal gasification is generated according to a pre-constructed stress-strain model, gas migration model, chemical reaction model, and energy balance model; a finite element initial model for underground coal gasification is established according to the multi-field coupling constitutive model; and the cavity evolution process of underground coal gasification is simulated according to the actual occurrence conditions of the coal seam and the finite element initial model, realizing the full-dimensional prediction of the deep underground coal gasification cavity modeling and development process, being able to simulate the boundary characteristics of the coal seam gasification cavity under different injection conditions, determining the influence of different underground coal gasification characteristic fields on the cavity evolution law, and providing technical support for the optimization of gasification process parameters under in-situ temperature and pressure conditions.

[0101] The following is a detailed explanation of each step.

[0102] S101: Generate a multi-field coupling constitutive model for underground coal gasification according to a pre-constructed stress-strain model, gas migration model, chemical reaction model, and energy balance model;

[0103] Specifically, as Figure 20 shown is a schematic diagram of the three-dimensional distribution of the cavity of underground coal gasification. The server constructs a thermo-hydro-mechanical-chemical (THMC) multi-field coupling constitutive model for the whole process of underground coal gasification according to a pre-constructed stress-strain model, gas migration model, chemical reaction model, and energy balance model to simulate and predict the cavity evolution law of underground coal gasification, including the changes in characteristic fields such as temperature, pressure, stress-strain, and gas concentration. As Figure 21The figure shows the coupling relationship diagram of multiple physical fields in underground coal gasification. Heat-flow-solid-chemical refers to the interaction between heat conduction, fluid seepage, solid deformation, and chemical reactions during underground coal gasification, corresponding to the energy balance model, gas migration model, stress-strain model, and chemical reaction model respectively.

[0104] In one embodiment, the deep coal can be a coal seam with a burial depth greater than 2200 meters and a thickness between 5 meters and 20 meters, but the present application is not limited thereto.

[0105] Figure 2 It is a schematic flow chart of the cavity evolution simulation method for underground coal gasification provided by an embodiment of the present application. As Figure 2 shown, the steps of pre-constructing the stress-strain model, gas migration model, chemical reaction model, and energy balance model include:

[0106] S201: Construct a stress-strain model according to the obtained block geological parameters and rock mechanics parameters;

[0107] Specifically, considering the thermal expansion of the coal matrix under high temperature and the gas pressure on the coal seam pores, the server constructs a stress-strain model according to the obtained block geological parameters and rock mechanics parameters. The block geological parameters include coal seam gas pressure, coal seam water vapor pressure, comprehensive pressure of the generated coal gas, and coal seam temperature, etc. The rock mechanics parameters include shear modulus of coal, bulk modulus of the coal matrix, Poisson's ratio of coal, and thermal expansion coefficient, etc.

[0108] In one embodiment, the non-isothermal stress-strain model constructed by the server can be expressed as:

[0109]

[0110] where G is the shear modulus of coal, K is the bulk modulus of the coal matrix, υ is Poisson's ratio of coal, α is the Biot coefficient, α T is the thermal expansion coefficient, p g is the coal seam gas pressure, p v is the coal seam water vapor pressure, p p is the comprehensive pressure of the generated coal gas, T is the coal seam temperature, i = x, y, z; j = x, y, z, f i and u i are the body force and displacement in the i direction, ε s is the volumetric strain caused by gas adsorption or desorption.

[0111] In one embodiment, the stress-strain model is based on the Navier form of the elasticity model, and the Navier model is used to describe the deformation and stress state of a continuous medium.

[0112] S202: Construct a gas migration model based on the obtained initial fluid parameters;

[0113] Specifically, the server constructs a gas migration model based on the obtained initial fluid parameters. During the underground coal gasification process, the main gases are gas and water vapor. Therefore, the gas migration model includes a gas migration model and a water vapor migration model. The initial fluid parameters include gas density, gas volume, gas Darcy velocity, etc.

[0114] Figure 3 It is a schematic flow diagram of the cavity evolution simulation method for underground coal gasification provided by an embodiment of the present application. As Figure 3 shown, S202 includes:

[0115] S301: Construct the gas migration model according to the initial fluid parameters and the gas migration mechanism;

[0116] Specifically, the gas migration mechanism in the coal seam matrix is a process dominated by diffusion, and the gas migration mechanism in the coal seam fissures is a process dominated by seepage. Due to the dynamic equilibrium of the gas pressure in the coal matrix and fissures, the gas migration model constructed by the server according to the initial fluid parameters and the gas migration mechanism can be expressed as:

[0117]

[0118] Where is the porosity, ρ g is the gas density under the equivalent coal seam gas pressure, ρ s is the coal seam density, ρ a is the gas density under standard atmospheric pressure, t is the total time, V L is the Langmuir volume constant at the critical temperature of gas adsorption and desorption, V sg is the gas volume adsorbed per unit mass of coal seam, is the Darcy velocity of the gas.

[0119] In one embodiment, the gas migration model is a mass continuity model that satisfies Darcy's law, where Darcy's law describes the seepage behavior of fluids in porous media, and the mass continuity model describes the mass conservation of fluids within a control volume.

[0120] S302: Construct the water vapor migration model according to the initial fluid parameters and the water vapor migration mechanism.

[0121] Specifically, water vapor content is mostly in the coal seam fissures. The water vapor migration model constructed by the server according to the initial fluid parameters and the water vapor migration mechanism can be expressed as:

[0122]

[0123] wherein, is the porosity, ρ v is the water vapor density, t is the total time, is the Darcy velocity of water vapor, m v is the water vapor mass, S v * is the change amount of the chemical reaction between part of the water vapor and char during the underground coal gasification process.

[0124] In one embodiment, the water vapor migration model is based on a mass continuity model that satisfies Darcy's law, where Darcy's law describes the seepage behavior of fluids in porous media, and the mass continuity model describes the mass conservation of fluids within a control volume.

[0125] In one embodiment, since the gas generated by the underground coal gasification reaction diffuses freely in the coal seam and also flows due to the seepage of water vapor and gas, the server also constructs a dilute substance transfer model in the porous medium, expressed as:

[0126]

[0127] wherein, is the porosity, c i is the concentration of different gas components, t is the total time, is the diffusion coefficient of the gas generated in the coal rock, a ij is the reaction rate coefficient, r j is the chemical reaction rate.

[0128] S203: Construct a chemical reaction model according to the underground coal gasification reaction;

[0129] Specifically, underground coal gasification includes various chemical reactions, such as coal pyrolysis, oxidation, and gasification reactions. The chemical reaction model constructed by the server according to the underground coal gasification reaction can be expressed as:

[0130] Coal→Char+H 2 +CO 2 +CO+H 2 O+H 2 S+CH 4 +N 2 +C 6 H 6

[0131] Char→C+S+H 2 +CH 4 +C 6 H 6 +H 2 S+N 2 +CO 2 +CO+H2 O + ASH

[0132] C + O 2 → CO 2

[0133] C + 0.5O 2 → CO

[0134] C + H 2 O → CO + H 2

[0135] C + CO 2 → 2CO

[0136] In one embodiment, the server also constructs an Arrhenius model to describe the relationship between the reaction rate and factors such as temperature and reaction activation energy, helping to simulate the generation and change of various gases during the gasification process. The Arrhenius model can be expressed as:

[0137]

[0138] where k r is the rate constant, A is the pre-exponential factor, E a is the apparent activation energy, R is the molar gas constant, and T is the coal seam temperature.

[0139] S204: Construct an energy balance model based on the thermal equilibrium state.

[0140] Specifically, since the pore gas and the coal rock solid particles are in a thermal equilibrium state during the gasification process, the server constructs an energy balance model based on the thermal equilibrium state, where the chemical reaction kinetic parameters include the equivalent specific heat capacity and the equivalent thermal conductivity, etc.

[0141] In one embodiment, the energy balance model constructed by the server based on the thermal equilibrium state can be expressed as:

[0142]

[0143] where the equivalent specific heat capacity the equivalent thermal conductivity T is the coal seam temperature, C ps , C pg and C pv are the specific heat capacities of coal particles, gas, and water vapor in the coal seam respectively, x g and x v are the sub-item coefficients of gas and water vapor, Q T is the chemical reaction heat source, is the Darcy velocity of gas, ρ g is the gas density under the equivalent coal seam gas pressure, ρ v is the water vapor density, is the Darcy velocity of water vapor, is the porosity, ρ s is the coal seam density, κ s , κ g and κ v are the thermal conductivities of coal particles, gas and water vapor in the coal seam, respectively.

[0144] Figure 4 is a schematic flowchart of a method for simulating the cavity evolution of underground coal gasification provided by an embodiment of the present application, as shown in Figure 4 shown, S101 includes:

[0145] S401: Generate a permeability evolution model according to the coal and rock porosity evolution model;

[0146] Specifically, the coal and rock porosity evolution model pre-constructed by the server is expressed as:

[0147]

[0148] wherein, the reference parameter refers to the initial value of the parameter ε v is the volumetric strain, is the porosity increase coefficient of the high-temperature gasification reaction, T is the coal seam temperature, T h0 is the critical temperature for water evaporation, is the initial value of the porosity.

[0149] The server generates a permeability evolution model according to the pre-constructed coal and rock porosity evolution model. The permeability evolution model is expressed as:

[0150]

[0151] wherein, is the porosity, is the initial value of the porosity, k 0 is the initial value of the permeability.

[0152] S402: Cross-couple the stress-strain model, the gas migration model and the energy balance model by using the coal and rock porosity evolution model, the permeability evolution model, the obtained gas volume model and the ideal gas state model, and combine the chemical reaction model to obtain the multi-field coupled constitutive model.

[0153] Specifically, the gas volume model adsorbed by the unit mass coal seam represented by the Langmuir model obtained by the server is expressed as:

[0154]

[0155] wherein, pg is the gas pressure of coal seam gas, T ar is the critical temperature for gas adsorption and desorption, P L is the critical temperature for gas adsorption and desorption T ar is the Langmuir pressure constant at, c 1 is the pressure constant, c 2 is the temperature constant, and T is the coal seam temperature.

[0156] The ideal gas state model obtained by the server is expressed as:

[0157]

[0158] Among them, ρ is the density of the gas, M is the molar mass, R is the molar gas constant, T is the coal seam temperature, and p is the gas pressure.

[0159] Taking into account the heat conduction, fluid seepage, solid deformation and the interaction between chemical reactions in the process of underground coal gasification, the server substitutes the coal-rock porosity evolution model, permeability evolution model, gas volume model and ideal gas state model into the stress-strain model, gas migration model, water vapor migration model and energy balance model of formulas (1)-(3) and (6) for cross-coupling to obtain the thermo-hydro-mechanical-chemical (THMC) multi-field coupling constitutive model. The multi-field coupling constitutive model includes the coal seam deformation model, coal seam gas migration model, coal seam water vapor migration model, coal seam energy model and chemical reaction model.

[0160] The coal seam deformation model is expressed as:

[0161]

[0162] Among them, G is the shear modulus of coal, K is the bulk modulus of coal matrix, υ is the Poisson's ratio of coal, α is the Biot coefficient, α T is the coefficient of thermal expansion, p g is the gas pressure of coal seam gas, p v is the water vapor pressure of coal seam, p p is the comprehensive pressure of the generated coal gas, T is the coal seam temperature, i = x, y, z; j = x, y, z, f i and u i are the body force and displacement in the i direction, ε s is the volumetric strain due to gas adsorption or desorption, p g is the equivalent coal seam gas pressure, T ar is the critical temperature for gas adsorption and desorption, P L is the critical temperature for gas adsorption and desorption T ar is the Langmuir pressure constant at, c 1 is the pressure constant, c2 is the temperature constant, V sg is the volume of gas adsorbed by unit mass of coal seam.

[0163] The coal seam gas migration model is expressed as:

[0164]

[0165] Among them, p g is the equivalent coal seam gas pressure, T ar is the critical temperature of gas adsorption and desorption, P L is the Langmuir pressure constant at the critical temperature T of gas adsorption and desorption ar under, c 1 is the pressure constant, c 2 is the temperature constant, is the porosity, ρ s is the coal seam density, ρ a is the gas density under standard atmospheric pressure, t is the total time, V L is the Langmuir volume constant at the critical temperature of gas adsorption and desorption, V sg is the volume of gas adsorbed by unit mass of coal seam, α is the Biot coefficient, is the initial value of the porosity, ε L is the adsorption strain under infinite pore pressure, α T is the coefficient of thermal expansion, is the coefficient of increase in porosity for high-temperature gasification reaction, k is the permeability, p v is the coal seam water vapor pressure, ε v is the volume strain, T is the coal seam temperature, K s is the bulk modulus of the skeleton, T a is the temperature under standard atmospheric pressure, μ g is the gas dynamic viscosity.

[0166] The coal seam water vapor migration model is expressed as:

[0167]

[0168] Among them, p g is the equivalent coal seam gas pressure, T ar is the critical temperature of gas adsorption and desorption, P L is the critical temperature T of gas adsorption and desorption ar under the Langmuir pressure constant, c 1 is the pressure constant, c 2 is the temperature constant, is the porosity, ρ s is the coal seam density, ρ ais the gas density under standard atmospheric pressure, t is the total time, V L is the Langmuir volume constant at the critical temperature of gas adsorption and desorption, V sg is the volume of gas adsorbed per unit mass of coal seam, α is the Biot coefficient, is the initial value of porosity, ε L is the adsorption strain under infinite pore pressure, α T is the coefficient of thermal expansion, is the coefficient of porosity increase in high-temperature gasification reaction, k is the permeability, p v is the water vapor pressure in the coal seam, ε v is the volume strain, R is the molar gas constant, K s is the bulk modulus of the skeleton, μ v is the dynamic viscosity of water vapor, A h is the water evaporation coefficient, M v is the molar mass of water vapor, S v * is the change in the chemical reaction of part of the water vapor and char during underground coal gasification.

[0169] The coal seam energy model is expressed as:

[0170]

[0171] Among them, the equivalent specific heat capacity The equivalent thermal conductivity T is the temperature of the coal seam, C ps , C pg and C pv are the specific heat capacities of coal particles, gas and water vapor in the coal seam respectively, x g and x v are the sub-item coefficients of gas and water vapor, Q T is the heat source of chemical reaction, is the Darcy velocity of gas, ρ g is the gas density under the equivalent coal seam gas pressure, ρ v is the water vapor density, is the Darcy velocity of water vapor, is the porosity, ρ s is the coal seam density, κ s , κ g and κ v are the thermal conductivities of coal particles, gas and water vapor in the coal seam respectively, p g is the equivalent coal seam gas pressure, p m is the adsorbed gas pressure, R is the molar gas constant, M v is the molar mass of water vapor, p v is the water vapor pressure in the coal seam, ε Lis the adsorption strain under infinite pore pressure, p m is the adsorbed state pressure of gas, is the porosity increase coefficient of high-temperature gasification reaction, α is the Biot coefficient, α T is the coefficient of thermal expansion, is the initial value of porosity, K s is the skeleton bulk modulus, T ar is the critical temperature of gas adsorption and desorption, P L is the critical temperature T of gas adsorption and desorption ar the Langmuir pressure constant at, c 1 is the pressure constant, c 2 is the temperature constant, κ s , κ g and κ v and κ are the thermal conductivities of coal particles, gas and water vapor in the coal seam respectively, ε v is the volume strain, M g is the molar mass of gas.

[0172] S102: Establish a finite element initial model for in-situ coal gasification according to the multi-field coupling constitutive model;

[0173] Specifically, the server uses the finite element analysis method to establish a finite element initial model for in-situ coal gasification according to the multi-field coupling constitutive model to simulate and predict the cavity evolution law of in-situ coal gasification, including the changes in characteristic fields such as temperature, pressure, stress strain and gas concentration.

[0174] Figure 5 is a schematic flow chart of the cavity evolution simulation method for in-situ coal gasification provided by an embodiment of the present application, as Figure 5 shown, S102 includes:

[0175] S501: Construct a two-dimensional geometric model according to the preset geometric parameters;

[0176] Specifically, the server uses the finite element analysis method to establish a simplified two-dimensional geometric model of the plane where the coal seam is located, specifically to construct a two-dimensional geometric model of the coal seam in the finite element software according to the preset geometric parameters for easy simulation and analysis.

[0177] S502: Establish the finite element initial model according to the two-dimensional geometric model and the multi-field coupling constitutive model.

[0178] Specifically, the server inputs the multi-field coupling constitutive model into the two-dimensional geometric model established by using the finite element software, and after grid division, obtains as Figure 22The shown initial finite element model is used to simulate and predict the cavity evolution law of underground coal gasification, including the changes in characteristic fields such as temperature, pressure, stress and strain, and gas concentration.

[0179] S103: Simulate the cavity evolution process of underground coal gasification according to the actual occurrence conditions of the coal seam and the initial finite element model.

[0180] Specifically, after the server completes the construction of the initial finite element model, it simulates the cavity evolution process of underground coal gasification according to the actual occurrence conditions of the coal seam and the initial finite element model, so as to simulate and predict the cavity evolution law of underground coal gasification, including the changes in characteristic fields such as temperature, pressure, stress and strain, and gas concentration.

[0181] Figure 6 is a schematic flowchart of a method for simulating the cavity evolution of underground coal gasification provided by an embodiment of the present application. As Figure 6 shown, S103 includes:

[0182] S601: Generate a finite element model according to the actual occurrence conditions of the coal seam and the initial finite element model;

[0183] Specifically, the server determines the parameters of the initial finite element model according to the actual occurrence conditions of the coal seam, and inputs the parameters into the initial finite element model to obtain a finite element model. Among them, the actual occurrence conditions of the coal seam include geological structure, coal seam thickness, lithological characteristics, porosity, permeability, temperature, pressure, and chemical composition, etc.

[0184] Figure 7 is a schematic flowchart of a method for simulating the cavity evolution of underground coal gasification provided by an embodiment of the present application. As Figure 7 shown, S601 includes:

[0185] S701: Generate multi-field boundary conditions according to the actual occurrence conditions of the coal seam;

[0186] Specifically, the server sets the boundary conditions of each physical field according to the obtained actual occurrence conditions of the coal seam, where the boundary conditions include in-situ stress parameters, initial temperature and pressure, etc., so as to input the multi-field boundary conditions into the initial finite element model.

[0187] In one embodiment, the server uses the similarity principle to obtain multi-field boundary conditions according to the actual occurrence conditions of the coal seam and inputs them into the initial finite element model.

[0188] S702: Perform heterogeneous assignment on the parameters of the initial finite element model to obtain heterogeneous parameters;

[0189] Specifically, considering the heterogeneity of the coal seam, the parameters of the model are assigned heterogeneous values according to the grid divided by the initial finite element model, and the heterogeneous parameters are obtained and input into the initial finite element model.

[0190] In one embodiment, the server assigns heterogeneous values to the parameters of the model using the Weibull distribution model, and uses the Weibull distribution model to characterize the heterogeneity of the coal seam. The expression of its probability distribution density function is as follows:

[0191]

[0192] In the formula, u represents the rock property parameters that satisfy this distribution, such as elastic modulus, permeability, etc., and u 0 represents the average value of the above parameters, and m is the shape parameter that defines the shape of the Weibull distribution model, that is, the heterogeneity coefficient.

[0193] In one embodiment, the server assigns heterogeneous values to parameters such as elastic modulus, permeability, heat conduction coefficient, and thermal conductivity in the initial finite element model, while keeping parameters such as in-situ stress and gasification time unchanged, to characterize the heterogeneous characteristics of the coal seam.

[0194] S703: Input the multi-field boundary conditions and the heterogeneous parameters into the initial finite element model to obtain the finite element model.

[0195] Specifically, after obtaining the multi-field boundary conditions according to the actual occurrence conditions of the coal seam and obtaining the heterogeneous parameters through heterogeneous replication, the server inputs the multi-field boundary conditions and the heterogeneous parameters into the initial finite element model to obtain the finite element model, so as to simulate and predict the cavity evolution law of underground coal gasification, including the changes of characteristic fields such as temperature, pressure, stress strain, and gas concentration.

[0196] S602: Use the finite element model to simulate the cavity evolution process of underground coal gasification.

[0197] Specifically, after the server obtains the finite element model, it uses the finite element model for calculation to simulate the cavity evolution process of underground coal gasification, including the changes of characteristic fields such as temperature, pressure, stress strain, and gas concentration, and realizes the full-dimensional prediction of the deep coal gasification cavity modeling and development process.

[0198] Figure 8 is a schematic flowchart of the cavity evolution simulation method for underground coal gasification provided by an embodiment of the present application. As Figure 8 shown, S602 includes:

[0199] S801: Use the finite element model and the obtained initial in-situ stress balance parameters to determine the cavity boundary characteristics;

[0200] Specifically, the server imports the obtained initial in-situ stress balance parameters into the finite element model, inherits the calculation results of the steady-state calculation, and then performs transient calculations step by step to simulate the boundary characteristics of the cavity formation and expansion during the gasification process. After the model starts to calculate, the gasification cavity will continuously expand, and the boundary characteristics of the gasification cavity include intuitive parameter information such as the length and height of the cavity, or changes based on parameters such as temperature and pressure.

[0201] In one embodiment, the server can use the Anderson acceleration method to improve the convergence of calculating highly nonlinear problems.

[0202] Figure 9 is a schematic flow chart of a method for simulating the cavity evolution of underground coal gasification provided by an embodiment of the present application. As Figure 9 shown, before determining the cavity boundary characteristics using the finite element model and the obtained initial in-situ stress balance parameters, it further includes:

[0203] S901: Establish a mechanical model according to the stress-strain model;

[0204] Specifically, in addition to constructing the finite element model, the server also establishes a mechanical model in the finite element software according to the stress-strain model to calculate the initial stress field and analyze the mechanical behavior in the coal seam.

[0205] S902: Perform steady-state calculation using the mechanical model to obtain the initial in-situ stress balance parameters.

[0206] Specifically, the server uses the established mechanical model to perform steady-state calculation to solve the stress and strain distributions of the model under stable conditions. The steady-state calculation aims to find the initial in-situ stress balance state of the coal seam and the surrounding rock mass under the current conditions, and obtain the initial in-situ stress balance parameters as the basis for subsequent analysis.

[0207] S802: Determine the cavity evolution process of underground coal gasification according to the cavity boundary characteristics.

[0208] Specifically, the server dynamically updates the model parameters according to the cavity boundary characteristics, simulates the changes of the cavity at different time nodes during the gasification process, and predicts the dynamic behaviors such as the expansion, contraction, and deformation of the gasification cavity, which involves the coupling of multiple physical fields such as gasification reaction, heat conduction, and gas migration.

[0209] In one embodiment, after determining the cavity evolution process of underground coal gasification, the server predicts possible geological problems during the gasification process, such as cavity collapse or rock mass fracture, based on the dynamic behavior of the cavity, so as to provide optimization suggestions and safety guarantee measures for the gasification process.

[0210] In one embodiment, the cavity evolution law obtained by the server can provide technical support for the optimization method of gasification process parameters under in-situ temperature and pressure conditions. The gasification process parameters include the injection water-oxygen ratio, injection pressure, initial temperature, etc. When these parameters are changed, the changes of the gasification cavity under different conditions can be obtained, and the optimal result can be regressed by comparing the result changes. The process parameters corresponding to the optimal result are the optimized process parameters.

[0211] The present application provides a method for simulating the cavity evolution of underground coal gasification. By generating a multi-field coupling constitutive model of underground coal gasification according to a pre-constructed stress-strain model, gas migration model, chemical reaction model, and energy balance model; establishing a finite element initial model of underground coal gasification according to the multi-field coupling constitutive model; and simulating the cavity evolution process of underground coal gasification according to the actual occurrence conditions of the coal seam and the finite element initial model, the full-dimensional prediction of the deep underground coal gasification cavity modeling and development process is realized. It can simulate the boundary characteristics of the coal seam gasification cavity under different injection conditions, determine the influence of different underground coal gasification characteristic fields on the cavity evolution law, and provide technical support for the optimization of gasification process parameters under in-situ temperature and pressure conditions. Among them, the non-uniform assignment of model parameters improves the performance of the model.

[0212] Based on the same inventive concept, an embodiment of the present application also provides a device for simulating the cavity evolution of underground coal gasification, which can be used to implement the method described in the above embodiment, as described in the following embodiment. Since the principle of solving problems by the device for simulating the cavity evolution of underground coal gasification is similar to that of the method for simulating the cavity evolution of underground coal gasification, the implementation of the device for simulating the cavity evolution of underground coal gasification can refer to the implementation of the method for determining the software performance benchmark, and the repeated parts will not be described again. As used hereinafter, the term "unit" or "module" can be a combination of software and / or hardware that can achieve a predetermined function. Although the system described in the following embodiments is preferably implemented in software, the implementation of hardware, or a combination of software and hardware, is also possible and contemplated.

[0213] Figure 10 is a schematic structural diagram of a device for simulating the cavity evolution of underground coal gasification provided by an embodiment of the present application, as Figure 10 shown, the device includes:

[0214] A constitutive model generation unit 1001, configured to generate a multi-field coupling constitutive model of underground coal gasification according to a pre-constructed stress-strain model, gas migration model, chemical reaction model, and energy balance model;

[0215] A finite element initial model establishment unit 1002, configured to establish a finite element initial model of underground coal gasification according to the multi-field coupling constitutive model;

[0216] The cavity evolution simulation unit 1003 is used to simulate the cavity evolution process of underground coal gasification according to the actual occurrence conditions of the coal seam and the finite element initial model.

[0217] Figure 11 It is a schematic structural diagram of the cavity evolution simulation device for underground coal gasification provided by an embodiment of the present application. On the basis of the Figure 10 embodiment, further, as Figure 11 shown, the cavity evolution simulation device for underground coal gasification provided by the present application further includes:

[0218] The stress-strain model construction unit 1101 is used to construct a stress-strain model according to the obtained block geological parameters and rock mechanics parameters;

[0219] The gas migration model construction unit 1102 is used to construct a gas migration model according to the obtained initial fluid parameters;

[0220] The chemical reaction model construction unit 1103 is used to construct a chemical reaction model according to the underground coal gasification reaction;

[0221] The energy balance model construction unit 1104 is used to construct an energy balance model based on the thermal equilibrium state.

[0222] Figure 12 It is a schematic structural diagram of the cavity evolution simulation device for underground coal gasification provided by an embodiment of the present application. On the basis of the Figure 11 embodiment, further, as Figure 12 shown, the cavity evolution simulation device for underground coal gasification provided by the present application further includes:

[0223] The gas migration model construction module 1201 is used to construct the gas migration model according to the initial fluid parameters and the gas migration mechanism;

[0224] The water vapor migration model construction module 1202 is used to construct the water vapor migration model according to the initial fluid parameters and the water vapor migration mechanism.

[0225] Figure 13 It is a schematic structural diagram of the cavity evolution simulation device for underground coal gasification provided by an embodiment of the present application. On the basis of the Figure 10 embodiment, further, as Figure 13 shown, the cavity evolution simulation device for underground coal gasification provided by the present application further includes:

[0226] The permeability evolution model generation module 1301 is used to generate a permeability evolution model according to the coal-rock porosity evolution model;

[0227] The constitutive model generation module 1302 is configured to cross-couple the stress-strain model, the gas migration model, and the energy balance model by using the coal-rock porosity evolution model, the permeability evolution model, the obtained gas volume model, and the ideal gas state model, and combine the chemical reaction model to obtain the multi-field coupled constitutive model.

[0228] Figure 14 is a schematic structural diagram of a cavity evolution simulation device for underground coal gasification provided by an embodiment of the present application. On the Figure 10 basis of the embodiment, further, as Figure 14 shown, the cavity evolution simulation device for underground coal gasification provided by the present application further includes:

[0229] The two-dimensional geometric model construction module 1401 is configured to construct a two-dimensional geometric model according to preset geometric parameters;

[0230] The finite element initial model establishment module 1402 is configured to establish the finite element initial model according to the two-dimensional geometric model and the multi-field coupled constitutive model.

[0231] Figure 15 is a schematic structural diagram of a cavity evolution simulation device for underground coal gasification provided by an embodiment of the present application. On the Figure 10 basis of the embodiment, further, as Figure 15 shown, the cavity evolution simulation device for underground coal gasification provided by the present application further includes:

[0232] The finite element model generation module 1501 is configured to generate a finite element model according to the actual occurrence conditions of the coal seam and the finite element initial model;

[0233] The cavity evolution simulation module 1502 is configured to simulate the cavity evolution process of underground coal gasification by using the finite element model.

[0234] Figure 16 is a schematic structural diagram of a cavity evolution simulation device for underground coal gasification provided by an embodiment of the present application. On the Figure 15 basis of the embodiment, further, as Figure 16 shown, the cavity evolution simulation device for underground coal gasification provided by the present application further includes:

[0235] The multi-field boundary condition generation sub-module 1601 is configured to generate multi-field boundary conditions according to the actual occurrence conditions of the coal seam;

[0236] The inhomogeneous parameter generation sub-module 1602 is configured to perform inhomogeneous assignment on the parameters of the finite element initial model to obtain inhomogeneous parameters;

[0237] The finite element model generation sub-module 1603 is configured to input the multi-field boundary conditions and the inhomogeneous parameters into the initial finite element model to obtain the finite element model.

[0238] Figure 17 is a schematic structural diagram of a cavity evolution simulation device for underground coal gasification provided by an embodiment of the present application. Based on the Figure 15 embodiment, further, as Figure 17 shown, the cavity evolution simulation device for underground coal gasification provided by the present application further includes:

[0239] The cavity boundary feature determination sub-module 1701 is configured to determine the cavity boundary features by using the finite element model and the obtained initial in-situ stress balance parameters;

[0240] The cavity evolution process determination sub-module 1702 is configured to determine the cavity evolution process of underground coal gasification according to the cavity boundary features.

[0241] Figure 18 is a schematic structural diagram of a cavity evolution simulation device for underground coal gasification provided by an embodiment of the present application. Based on the Figure 17 embodiment, further, as Figure 18 shown, the cavity evolution simulation device for underground coal gasification provided by the present application further includes:

[0242] The mechanical model establishment unit 1801 is configured to establish a mechanical model according to the stress-strain model;

[0243] The steady-state calculation unit 1802 is configured to perform a steady-state calculation by using the mechanical model to obtain the initial in-situ stress balance parameters.

[0244] The present application provides a method and a device for simulating the cavity evolution of underground coal gasification. By generating a multi-field coupling constitutive model of underground coal gasification according to a pre-constructed stress-strain model, a gas migration model, a chemical reaction model, and an energy balance model; establishing an initial finite element model of underground coal gasification according to the multi-field coupling constitutive model; and simulating the cavity evolution process of underground coal gasification according to the actual occurrence conditions of the coal seam and the initial finite element model, the full-dimensional prediction of the deep underground coal gasification cavity modeling and the development process is realized. It can simulate the cavity boundary features of the coal seam gasification cavity under different injection conditions, determine the influence of different underground coal gasification characteristic fields on the cavity evolution law, and provide technical support for optimizing the gasification process parameters under in-situ temperature and pressure conditions. Among them, the non-uniform assignment of model parameters improves the performance of the model.

[0245] Figure 19 is a schematic physical structure diagram of an electronic device provided by an embodiment of the present application, as Figure 19As shown in the figure, the electronic device may include: a processor 1901, a communications interface 1902, a memory 1903, and a communication bus 1904. Among them, the processor 1901, the communications interface 1902, and the memory 1903 communicate with each other through the communication bus 1904. The processor 1901 may call logic instructions in the memory 1903 to execute the following methods: generating a multi-field coupling constitutive model for underground coal gasification according to a pre-constructed stress-strain model, gas migration model, chemical reaction model, and energy balance model; establishing a finite element initial model for underground coal gasification according to the multi-field coupling constitutive model; and simulating the cavity evolution process of underground coal gasification according to the actual occurrence conditions of the coal seam and the finite element initial model.

[0246] In addition, when the logic instructions in the above-mentioned memory 1903 are implemented in the form of software functional units and sold or used as independent products, they may be stored in a computer-readable storage medium. Based on such an understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or a part of this technical solution, may be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in various embodiments of this application. The foregoing storage medium includes: various media such as USB flash drives, mobile hard disks, read-only memories (ROM, Read-Only Memory), random access memories (RAM, Random Access Memory), magnetic disks, or optical discs that can store program codes.

[0247] This embodiment discloses a computer program product. The computer program product includes a computer program stored on a computer-readable storage medium. The computer program includes program instructions. When the program instructions are executed by a computer, the computer can execute the methods provided in the above method embodiments, for example, including: generating a multi-field coupling constitutive model for underground coal gasification according to a pre-constructed stress-strain model, gas migration model, chemical reaction model, and energy balance model; establishing a finite element initial model for underground coal gasification according to the multi-field coupling constitutive model; and simulating the cavity evolution process of underground coal gasification according to the actual occurrence conditions of the coal seam and the finite element initial model.

[0248] This embodiment provides a computer-readable storage medium that stores a computer program, which causes the computer to execute the methods provided in the above method embodiments. For example, it includes: generating a multi-field coupling constitutive model for underground coal gasification according to a pre-constructed stress-strain model, gas migration model, chemical reaction model, and energy balance model; establishing a finite element initial model for underground coal gasification according to the multi-field coupling constitutive model; and simulating the cavity evolution process of underground coal gasification according to the actual occurrence conditions of the coal seam and the finite element initial model.

[0249] Those skilled in the art should understand that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0250] The present application is described with reference to the flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each flow and / or block in the flowchart and / or block diagram can be implemented by computer program instructions, and the combination of the flows and / or blocks in the flowchart and / or block diagram can also be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing devices generate a device for realizing the functions specified in one Figure 1 flow or multiple flows and / or blocks Figure 1 block or multiple blocks.

[0251] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer-readable memory generate a manufactured product including an instruction device, and the instruction device realizes the functions specified in one Figure 1 flow or multiple flows and / or blocks Figure 1 block or multiple blocks.

[0252] These computer program instructions can also be loaded onto a computer or other programmable data processing device, so that a series of operation steps are executed on the computer or other programmable device to generate a computer-implemented process. Therefore, the instructions executed on the computer or other programmable device provide for realizing the functions in one Figure 1 flow or multiple flows and / or blocks Figure 1Steps of the functions specified in one or more boxes.

[0253] In the description of this specification, the descriptions with reference to terms such as "one embodiment", "a specific embodiment", "some embodiments", "for example", "example", "specific example", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of this application. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0254] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of this application. It should be understood that the above are only specific embodiments of this application and are not used to limit the protection scope of this application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of this application shall be included in the protection scope of this application.

Claims

1. A method for simulating cavity evolution of underground coal gasification, characterized in that: include: Generate a multi-field coupled constitutive model for underground coal gasification based on the pre-built stress-strain model, gas migration model, chemical reaction model and energy balance model; Establishing a finite element initial model of underground coal gasification according to the multi-field coupled constitutive model; Simulating the cavity evolution process of underground coal gasification according to the actual occurrence conditions of the coal seam and the finite element initial model; The steps of pre-built stress-strain model, gas migration model, chemical reaction model and energy balance model include: Construct a stress-strain model based on the acquired block geological parameters and rock mechanics parameters; A gas migration model is constructed based on the obtained initial fluid parameters; Construct a chemical reaction model based on underground coal gasification reaction; Construct an energy balance model based on thermal equilibrium state; The gas migration model includes a gas migration model and a water vapor migration model; the gas migration model is constructed according to the acquired initial fluid parameters, including: constructing the gas migration model according to the initial fluid parameters and the gas migration mechanism; Constructing the water vapor migration model according to the initial fluid parameters and the water vapor migration mechanism; The multi-field coupled constitutive model of underground coal gasification is generated according to the pre-built stress-strain model, gas migration model, chemical reaction model and energy balance model, including: Generate a permeability evolution model based on the acquired coal rock porosity evolution model; The stress-strain model, the gas migration model and the energy balance model are cross-coupled using the coal rock porosity evolution model, the permeability evolution model, the acquired gas volume model and the ideal gas state model, and combined with the chemical reaction model to obtain the multi-field coupled constitutive model.

2. The cavity evolution simulation method for underground coal gasification according to claim 1, characterized in that: The method of establishing a finite element initial model of underground coal gasification according to the multi-field coupled constitutive model comprises: Construct a two-dimensional geometric model according to preset geometric parameters; The finite element initial model is established according to the two-dimensional geometric model and the multi-field coupling constitutive model.

3. The cavity evolution simulation method for underground coal gasification according to claim 1, characterized in that: The simulation of the cavity evolution process of underground coal gasification based on the actual occurrence conditions of the coal seam and the finite element initial model includes: Generate a finite element model according to the actual occurrence conditions of the coal seam and the finite element initial model; The finite element model is used to simulate the cavity evolution process of underground coal gasification.

4. The cavity evolution simulation method for underground coal gasification according to claim 3 is characterized in that: The generating of the finite element model according to the actual occurrence conditions of the coal seam and the finite element initial model comprises: Generate multiple boundary conditions according to the actual occurrence conditions of coal seams; Performing heterogeneous assignment on the parameters of the finite element initial model to obtain heterogeneous parameters; The multi-field boundary conditions and the inhomogeneous parameters are input into the finite element initial model to obtain the finite element model.

5. The cavity evolution simulation method for underground coal gasification according to claim 3, characterized in that: The method of simulating the cavity evolution process of underground coal gasification by using the finite element model includes: Determining cavity boundary characteristics using the finite element model and the obtained initial geostress balance parameters; The cavity evolution process of underground coal gasification is determined according to the cavity boundary characteristics.

6. The cavity evolution simulation method for underground coal gasification according to claim 5, characterized in that: Before determining the cavity boundary characteristics by using the finite element model and the obtained initial geostress balance parameters, the method further includes: Establishing a mechanical model according to the stress-strain model; The mechanical model is used to perform steady-state calculations to obtain initial ground stress equilibrium parameters.

7. A cavity evolution simulation device for underground coal gasification, characterized in that: include: A constitutive model generation unit is used to generate a multi-field coupled constitutive model of underground coal gasification based on a pre-built stress-strain model, a gas migration model, a chemical reaction model, and an energy balance model; A finite element initial model building unit, used to build a finite element initial model of underground coal gasification according to the multi-field coupling constitutive model; A cavity evolution simulation unit, used to simulate the cavity evolution process of underground coal gasification according to the actual occurrence conditions of the coal seam and the finite element initial model; A stress-strain model building unit is used to build a stress-strain model based on the acquired block geological parameters and rock mechanics parameters; A gas migration model building unit, used to build a gas migration model according to the acquired initial fluid parameters; A chemical reaction model building unit, used for building a chemical reaction model according to underground coal gasification reaction; An energy balance model building unit, used for building an energy balance model based on a thermal balance state; The gas migration model building unit comprises: A gas migration model building module, used to build the gas migration model according to the initial fluid parameters and the gas migration mechanism; A water vapor migration model building module, used to build the water vapor migration model according to the initial fluid parameters and the water vapor migration mechanism; The constitutive model generating unit comprises: A permeability evolution model generation module is used to generate a permeability evolution model according to the acquired coal rock porosity evolution model; The constitutive model generation module is used to cross-couple the stress-strain model, the gas migration model and the energy balance model by using the coal rock porosity evolution model, the permeability evolution model, the acquired gas volume model and the ideal gas state model, and combine the chemical reaction model to obtain the multi-field coupled constitutive model.

8. The cavity evolution simulation device for underground coal gasification according to claim 7, characterized in that: The finite element initial model building unit comprises: A two-dimensional geometric model building module, used to build a two-dimensional geometric model according to preset geometric parameters; The finite element initial model establishment module is used to establish the finite element initial model according to the two-dimensional geometric model and the multi-field coupling constitutive model.

9. The cavity evolution simulation device for underground coal gasification according to claim 7, characterized in that: The cavity evolution simulation unit comprises: A finite element model generation module, used to generate a finite element model according to the actual occurrence conditions of the coal seam and the finite element initial model; The cavity evolution simulation module is used to simulate the cavity evolution process of underground coal gasification using the finite element model.

10. The cavity evolution simulation device for underground coal gasification according to claim 9, characterized in that: The finite element model generation module comprises: The multi-field boundary condition generation submodule is used to generate multi-field boundary conditions according to the actual occurrence conditions of the coal seam; A non-homogeneous parameter generation submodule is used to perform non-homogeneous assignment on the parameters of the finite element initial model to obtain non-homogeneous parameters; The finite element model generation submodule is used to input the multi-field boundary conditions and the inhomogeneous parameters into the finite element initial model to obtain the finite element model.

11. The cavity evolution simulation device for underground coal gasification according to claim 9, characterized in that: The cavity evolution simulation module comprises: A cavity boundary feature determination submodule, used to determine the cavity boundary features using the finite element model and the acquired initial geostress balance parameters; The cavity evolution process determination submodule is used to determine the cavity evolution process of underground coal gasification according to the cavity boundary characteristics.

12. The cavity evolution simulation device for underground coal gasification according to claim 11, characterized in that: Also includes: A mechanical model building unit, used to build a mechanical model according to the stress-strain model; The steady-state calculation unit is used to perform steady-state calculation using the mechanical model to obtain initial ground stress equilibrium parameters.

13. A computer device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the method according to any one of claims 1 to 6 is implemented.

14. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the method according to any one of claims 1 to 6 is implemented.

15. A computer program product, characterized in that The computer program product comprises a computer program, and when the computer program is executed by a processor, the method according to any one of claims 1 to 6 is implemented.

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