A method and device for predicting the migration process of micro-leakage methane in porous media

Abstract

The present invention discloses a method for predicting the migration process of micro-leakage methane in porous media, comprising the following steps: S1, constructing a prediction model; S1-1, gradually establishing partial differential equations of gas phase and water phase according to Darcy's law and the law of conservation of mass; S1-2, respectively processing the partial differential equations of gas phase and water phase using the implicit difference method of backward difference to obtain corresponding linear discrete equations; S1-3, combining the linear discrete equations obtained in step S1-2 to construct a model for predicting the distribution of methane concentration in porous media with depth and time; S2, obtaining training data S3, updating the model obtained in step S2 with the data obtained in step S3. The concentration change trend of micro-leakage methane in porous media can be accurately predicted, reducing the difficulty of monitoring the change of methane concentration, and contributing to accelerating the research progress of atmospheric methane and promoting the research of global greenhouse effect.

Description

Technical Field

[0001] The invention relates to the technical field of light hydrocarbon micro-leakage research in oil and gas reservoirs, and in particular to a method and a device for predicting the migration process of micro-leakage methane in porous media. Background Art

[0002] Microleakage is the migration of methane and other gases from deep oil and gas reservoirs in oil and gas basins to the surface, where unoxidized methane is released into the atmosphere, leading to an enhanced greenhouse effect. The known oil and gas basins in the world cover an area of ​​up to 80 million km. 2 Therefore, micro-seepage methane in oil and gas basins plays an important role in atmospheric temperature changes. It is of great significance to study its migration mechanism and predict the release amount. In the middle of the 20th century, many scientists began to study the mechanism and vertical migration mechanism of hydrocarbon gas in underground oil and gas reservoirs, hoping to clarify the migration process of micro-seepage methane in theory and promote the research progress of atmospheric methane. In 1996, Klusman and Saeed proposed the basic equation describing hydrocarbon gas and water in porous media based on Darcy's law-two-phase flow equation, and further improved and modified it to be suitable for buoyancy-driven hydrocarbon gas migration. In 2009, Klusman used computer program code to simulate the change of hydrocarbon gas flux with time and depth based on this equation, which has a very good reference for studying the migration of micro-seepage after methane escapes from the reservoir. In addition, models that can show the migration process of micro-seepage methane and predict the change of methane concentration are still very scarce and cannot meet the current model requirements. Summary of the invention

[0003] The purpose of the present invention is to solve the two-phase flow equation based on the finite difference method and MATLAB, and propose a method and device for predicting the migration process of micro-seepage methane in porous media, which can clearly show the changing trend of micro-seepage methane above the reservoir and below the water table with time and depth.

[0004] In order to solve the above technical problems, the technical solution of the present invention is:

[0005] A method for predicting the migration process of micro-leakage methane in porous media comprises the following steps:

[0006] S1. Build a prediction model

[0007] S1-1, gradually establish the partial differential equations of the gas phase and the water phase according to Darcy's law and the law of conservation of mass;

[0008] S1-2, the partial differential equations of the gas phase and the water phase are processed by the implicit difference method of backward difference to obtain the corresponding linear discrete equations;

[0009] S1-3, combining the linear discrete equations obtained in step S1-2 to construct a model for predicting the distribution of methane concentration in porous media with depth and time;

[0010] S2. Get training data

[0011] According to the actual stratum, a simulated stratum column is set, wherein the simulated stratum column is set with a simulated cap layer, a simulated stratum and a simulated Quaternary sediment from bottom to top, wherein the simulated Quaternary sediment is set with two monitoring layers, the simulated stratum is set with four monitoring layers, and the simulated cap layer is set with one monitoring layer. Mixed hydrocarbon gas is injected from the bottom of the simulated stratum column to simulate the micro-leakage migration of methane gas in the reservoir under the real geology, and water is injected to simulate the saturated zone at the same time, and the pressure, temperature, methane concentration and flux of each monitoring layer at each time point are monitored;

[0012] S3. Update the model obtained in step S2 using the data obtained in step S3.

[0013] Preferably, in step S1-1, the method for establishing the partial differential equation of the gas phase is as follows:

[0014] 1) Darcy's law is proportional to the potential gradient of the gas phase, as follows:

[0015]

[0016] Among them, V g represents the gas velocity; K represents the intrinsic permeability, the unit is m 2 ; K g Represents the relative permeability of gas, the unit is m 2 ;μ g represents viscosity, the unit is kg / m / s; ▽ represents the vector differential operator, φ g represents the gas potential energy, φ g =P+ρgh;

[0017] 2) The pressure in the gas phase is greater than the pressure in the water phase, and the difference between the two forms the capillary pressure P c :

[0018] P c =P g -P w =(φ g -φ w )+(ρ g -ρ w )gh (2)

[0019] Where P represents the pressure of the water phase or gas phase; φ w represents water potential, φ w =P+ρgh;ρ g and ρw They represent the viscosity of water and gas respectively; g represents the acceleration due to gravity; h represents the height of the column;

[0020] 3) The relationship between capillary pressure and water saturation s can be obtained by the following formula:

[0021]

[0022] So we can get:

[0023]

[0024] 4) Based on the law of conservation of mass, the partial differential equation of gas potential with respect to time t can be finally obtained:

[0025]

[0026] Among them, ▽· represents the divergence, denoted as div, φ w and φ g represents potential energy, Q g is the flux of the gas phase, ε represents the water content, and Represents partial differential.

[0027] Preferably, in step S1-2, the method for obtaining the linear discrete equation corresponding to the gas phase is as follows:

[0028] 1) Simplify the partial differential equation (5):

[0029]

[0030] 2) Order The partial differential equation (6) is discretized by backward difference:

[0031]

[0032] 3) Arrange formula (7) to obtain:

[0033]

[0034] Preferably, in step S1-1, the method for establishing the partial differential equation of the water phase is:

[0035] 1) Darcy's law is proportional to the potential gradient of the water phase, as follows:

[0036]

[0037] Among them, V w Indicates the water velocity in m 2 / s; K w Represents water relative permeability, unit is m2 ;μ w Indicates viscosity, the unit is kg / m / s; φ w represents the water potential energy, φ w =P+ρgh;

[0038] 2) According to the law of conservation of mass, equations (4) and (9) can be used to obtain the partial differential equation of water potential with respect to time t:

[0039]

[0040] Among them, Q w Represents the flux of the aqueous phase.

[0041] Preferably, in step S1-2, the method for obtaining the linear discrete equation corresponding to the water phase is as follows:

[0042] 1) Simplify the partial differential equation (10):

[0043]

[0044] 2) Order The partial differential equation (11) is discretized by backward difference:

[0045]

[0046] 3) Arrange formula (12) to obtain:

[0047]

[0048] Preferably, in step S1-3, a model for predicting the distribution of methane concentration in porous media with depth and time is constructed, and its expression is as follows:

[0049]

[0050] Preferably, in step S3, the model for predicting the distribution of methane concentration in porous media with depth and time is updated to obtain:

[0051]

[0052] Transforming formula (15) into a form that is convenient for solving, we get:

[0053]

[0054] The present invention also discloses a device for predicting the migration process of micro-seepage methane in porous media, comprising a data acquisition unit, a memory and a processor. The memory stores a computer program that can be run on the processor. The computer program run by the processor implements the above-mentioned method for predicting the migration process of micro-seepage methane in porous media.

[0055] Preferably, the data acquisition unit includes a simulated formation column, a water tank and an air cylinder, the simulated formation column is provided with a simulated cap layer, a simulated formation and a simulated Quaternary sediment from bottom to top, the simulated Quaternary sediment is provided with two monitoring layers, the simulated formation is provided with four monitoring layers, and the simulated cap layer is provided with one monitoring layer, the water tank and the air cylinder are both connected to the bottom of the simulated formation column, a constant pressure flow pump and a water valve are provided between the water tank and the simulated formation column, and a pressure gauge is provided between the air cylinder and the simulated formation column.

[0056] The present invention has the following characteristics and beneficial effects:

[0057] The above technical solution can accurately predict the concentration change trend of micro-leakage methane in porous media, reduce the difficulty of monitoring methane concentration changes, and contribute to accelerating the research progress of atmospheric methane and promoting the research on the global greenhouse effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0059] Figure 1 This is a diagram of a micro-leakage methane migration simulation experimental device in an embodiment of the present invention.

[0060] Figure 2 This is a prediction diagram of the potential energy change trend of micro-leakage methane in an embodiment of the present invention.

[0061] Figure 3 This is a prediction diagram of the change trend of micro-leakage methane concentration in an embodiment of the present invention.

[0062] In the figure: 1-simulated stratigraphic column, 101-simulated Quaternary sediment, 102-simulated stratigraphic layer, 103-simulated cap layer, 2-water tank, 3-constant pressure flow pump, 4-water valve, 5-pressure gauge, 6-gas cylinder. DETAILED DESCRIPTION

[0063] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0064] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and the like are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", and the like may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0065] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0066] The present invention provides a method for predicting the migration process of micro-leakage methane in porous media, comprising the following steps:

[0067] S1. Build a prediction model

[0068] S1-1, gradually establish the partial differential equations of the gas phase and the water phase according to Darcy's law and the law of conservation of mass;

[0069] S1-2, the partial differential equations of the gas phase and the water phase are processed by the implicit difference method of backward difference to obtain the corresponding linear discrete equations;

[0070] S1-3, combining the linear discrete equations obtained in step S1-2 to construct a model for predicting the distribution of methane concentration in porous media with depth and time;

[0071] S2. Get training data

[0072] According to the actual stratum, a simulated stratum column is set, wherein the simulated stratum column is set with a simulated cap layer, a simulated stratum and a simulated Quaternary sediment from bottom to top, wherein the simulated Quaternary sediment is set with two monitoring layers, the simulated stratum is set with four monitoring layers, and the simulated cap layer is set with one monitoring layer. Mixed hydrocarbon gas is injected from the bottom of the simulated stratum column to simulate the micro-leakage migration of methane gas in the reservoir under the real geology, and water is injected to simulate the saturated zone at the same time, and the pressure, temperature, methane concentration and flux of each monitoring layer at each time point are monitored;

[0073] Understandably, due to the difficulty in obtaining data under actual geological conditions, the actual strata were simplified into simulated cap layers, simulated strata, and simulated Quaternary sediments, i.e., near the surface. A simplified three-layer stratigraphic column was built in the laboratory, and seven monitoring layers were arranged from bottom to top, such as Figure 1 As shown, mixed hydrocarbon gas is injected from the bottom of the column to simulate the micro-leakage and migration of methane gas in the reservoir under real geology, and water is injected to simulate the saturated zone. The pressure, temperature, methane concentration, flux and other data of each monitoring layer at each time point are monitored.

[0074] S3. Update the model obtained in step S2 using the data obtained in step S3.

[0075] In the above technical solution, a model is established based on the physical properties of micro-seepage methane, and the model is continuously updated and iterated based on the data, so that the concentration change trend of micro-seepage methane in porous media can be accurately predicted, reducing the difficulty of monitoring methane concentration changes, and contributing to accelerating the research progress of atmospheric methane and promoting the research on the global greenhouse effect.

[0076] Specifically, in step S1-1, the method for establishing the partial differential equation of the gas phase is as follows:

[0077] 1) Darcy's law is proportional to the potential gradient of the gas phase, as follows:

[0078]

[0079] Among them, V g represents the gas velocity; K represents the intrinsic permeability, the unit is m 2 ; K g Represents the relative permeability of gas, the unit is m 2 ;μ g represents viscosity, the unit is kg / m / s; ▽ represents the vector differential operator, φ g represents the gas potential energy, φ g =P+ρgh;

[0080] 2) The pressure in the gas phase is greater than the pressure in the water phase, and the difference between the two forms the capillary pressure P c :

[0081] P c =P g -P w =(φ g -φ w )+(ρ g -ρ w )gh (2)

[0082] Where P represents the pressure of the water phase or gas phase; φ w represents water potential, φ w =P+ρgh;ρ g and ρ w They represent the viscosity of water and gas respectively; g represents the acceleration due to gravity; h represents the height of the column;

[0083] 3) The relationship between capillary pressure and water saturation s can be obtained by the following formula:

[0084]

[0085] So we can get:

[0086]

[0087] 4) Based on the law of conservation of mass, the partial differential equation of gas potential with respect to time t can be finally obtained:

[0088]

[0089] Among them, ▽· represents the divergence, denoted as div, φ w and φ g represents potential energy, Q g is the flux of the gas phase, ε represents the water content, and Represents partial differential.

[0090] It can be understood that in step S1-1, the partial differential equation of the gas phase is gradually established according to Darcy's law and the law of conservation of mass, and the migration process of gas in the porous medium is expressed in the form of a mathematical equation. By solving the gas phase partial differential equation, the variation law of methane potential energy in time and space scales can be obtained.

[0091] Furthermore, in step S1-2, the method for obtaining the linear discrete equation corresponding to the gas phase is as follows:

[0092] 2) Simplify the partial differential equation (5):

[0093]

[0094] 2) Order The partial differential equation (6) is discretized by backward difference:

[0095]

[0096] 3) Arrange formula (7) to obtain:

[0097]

[0098] It should be noted that since this model only studies the migration of micro-leakage methane in the vertical direction, the partial differential equation (5) can be simplified, thereby reducing the amount of calculation and improving the prediction efficiency.

[0099] In the above technical solution, the gas phase partial differential equation (6) is processed by the implicit difference method of backward difference to obtain the corresponding linear discrete equation. Finite difference is one of the two most widely used methods for numerical solution of partial differential equations. The approximate solution of the potential energy value of methane in porous media can be obtained through the difference equation, which solves the problem that the solution of the partial differential equation cannot be expressed in the form of analytical solution.

[0100] The present invention is further configured that in step S1-1, the method for establishing the partial differential equation of the water phase is:

[0101] 1) Darcy's law is proportional to the potential gradient of the water phase, as follows:

[0102]

[0103] Among them, V w Indicates the water velocity in m 2 / s; K w Represents water relative permeability, unit is m 2 ;μ w Indicates viscosity, the unit is kg / m / s; φ w represents the water potential energy, φ w =P+ρgh;

[0104] 2) According to the law of conservation of mass, equations (4) and (9) can be used to obtain the partial differential equation of water potential with respect to time t:

[0105]

[0106] Among them, Q w Represents the flux of the aqueous phase.

[0107] In the above technical solution, the partial differential equation of the water phase is established according to Darcy's law and the law of conservation of mass. The migration process of the liquid in the porous medium is expressed in the form of a mathematical equation, and the change law of the water phase potential energy in time and space scales can be obtained by solving the partial differential equation of the water phase.

[0108] In step S1-2, the method for obtaining the linear discrete equation corresponding to the water phase is as follows:

[0109] 1) Simplify the partial differential equation (10):

[0110]

[0111] 2) Order The partial differential equation (11) is discretized by backward difference:

[0112]

[0113] 3) Arrange formula (12) to obtain:

[0114]

[0115] In the above technical solution, the water phase partial differential equation (10) is processed by the implicit difference method of backward difference to obtain the corresponding linear discrete equation, and the approximate solution of the potential energy change of the water phase in the porous medium is obtained through the finite difference equation of the water phase.

[0116] Furthermore, in step S1-3, a model for predicting the distribution of methane concentration in porous media with depth and time is constructed, and its expression is as follows:

[0117]

[0118] It is understandable that since the partial differential equations of the two phases both exist in another phase, it is impossible to obtain the potential energy change of the methane or water phase by solving a single equation, so the linear discrete equations obtained in step S1-2 are combined to construct a coupling model of methane and water phases. By writing a program in MATLAB to solve the coupling model, an approximate solution of the change value of the potential energy of the water phase and methane on the spatial and temporal scales can be obtained, and finally the prediction of the migration process of micro-leakage methane in porous media can be realized.

[0119] Specifically, in step S3, the model for predicting the distribution of methane concentration in porous media with depth and time is updated to obtain:

[0120]

[0121] Transforming formula (15) into a form that is convenient for solving, we get:

[0122]

[0123] It is understandable that, since water does not achieve an ideal flow effect in the simulated formation column during the actual experiment of the physical simulation, the model for predicting the change of methane concentration with depth and time obtained in step S3 is updated.

[0124] This embodiment illustrates the prediction effect through specific implementation, which is as follows:

[0125] By observing formula (16), it is found that the micro-leakage methane migration model is a standard one-dimensional heat conduction equation, which can be solved in the same way as the one-dimensional heat conduction equation. The process is as follows:

[0126] 1) To make the subsequent expression clearer, the symbols of formula (16) are simplified:

[0127]

[0128] 2) Expressed in function matrix form:

[0129]

[0130] Among them, the matrix

[0131] Furthermore, the experimental data of five monitoring layers of the caprock and the stratum were selected to construct the model, define the constant values ​​and calculate the values ​​of each parameter:

[0132] K=0.202mD=2.02×10 -16 m 2 (Experimental matrix)

[0133]

[0134] Determined by soil-water characteristic curve

[0135]

[0136] Where D0 is the free atmospheric diffusion coefficient, in cm 2 / s; T represents Kelvin temperature, unit is K; M1 and M2 represent the molar mass fraction of air and methane, unit is g / mol; P represents atmospheric pressure, unit is atm; σ 1,2 represents the average collision diameter of air and methane, in nm; Ω represents the diffusion collision integral, dimensionless;

[0137] D soil =D0ε 2 (twenty two)

[0138] Where D soil Represents the gas diffusion coefficient, the unit is m 2 / s; ε represents porosity, dimensionless;

[0139]

[0140] Where Qz Indicates flux, the unit is kg / (m 2 d); P t , P s and P z Respectively represent the total pressure, the partial pressure of methane on the surface and the partial pressure of methane at depth z, the unit is pa; M air represents mass fraction, the unit is g / mol; z represents, the unit is m;

[0141] The concentration is converted to pressure using the ideal gas state equation:

[0142]

[0143] Where p is the pressure, the unit is pa; c is the concentration, the unit is ppm; R is the gas constant, the unit is pa·m 3 / mol·K, take 8.314; T represents, the unit is K;

[0144] It should be noted that, in order to verify the microseepage methane migration model, the program of the present invention is run in the Matlab2018b environment, using an Intel Core i5 processor, 2.5GHz CPU, and a computer with 4GB of memory. Figure 2 This is the prediction result of micro-leakage methane pressure change trend. Figure 3 This is a graph showing the prediction results of the trend of changes in microleakage methane concentration.

[0145] The present invention also discloses a device for predicting the migration process of micro-leakage methane in porous media. Figure 1 As shown, it includes a data acquisition unit, a memory and a processor, the memory stores a computer program that can be run on the processor, and the computer program run by the processor implements the above-mentioned method for predicting the migration process of micro-seepage methane in porous media.

[0146] According to a further configuration of the present invention, the data acquisition unit includes a simulated formation column 1, a water tank 2 and an air cylinder 6; the simulated formation column 1 is provided with a simulated cap layer 103, a simulated formation 102 and a simulated Quaternary sediment 101 from bottom to top; the simulated Quaternary sediment 101 is provided with two monitoring layers, the simulated formation 102 is provided with four monitoring layers, and the simulated cap layer 103 is provided with one monitoring layer; the water tank 2 and the air cylinder 6 are both connected to the bottom of the simulated formation column; a constant pressure flow pump 3 and a water valve 4 are provided between the water tank 2 and the simulated formation column; a pressure gauge 5 is provided between the air cylinder 6 and the simulated formation column.

[0147] The embodiments of the present invention are described in detail above with reference to the accompanying drawings, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions and variations of these embodiments including components are made without departing from the principles and spirit of the present invention, and still fall within the scope of protection of the present invention.

Claims

1. A method for predicting the migration process of micro-leakage methane in porous media, characterized in that: The steps include: S1. Build a prediction model S1-1, gradually establish the partial differential equations of the gas phase and the water phase according to Darcy's law and the law of conservation of mass; The method of establishing the partial differential equation of the gas phase is as follows: 1) Darcy's law is proportional to the potential gradient of the gas phase, as follows: Among them, V g represents the gas velocity; K represents the intrinsic permeability, the unit is m 2 ; K g Represents the relative permeability of gas, the unit is m 2 ;μ g Indicates viscosity in kg / m / s; represents the vector differential operator, φ g represents the gas potential energy, φ g =P+ρgh; 2) The pressure in the gas phase is greater than the pressure in the water phase, and the difference between the two forms the capillary pressure P c : P c =P g -P w =(φ g -f w )+(ρ g -r w )gh (2) Where P represents the pressure of the water phase or gas phase; φ w represents water potential, φ w =P+ρgh;ρ g and ρ w They represent the viscosity of water and gas respectively; g represents the acceleration due to gravity; h represents the height of the column; 3) The relationship between capillary pressure and water saturation s can be obtained by the following formula: So we can get: 4) Based on the law of conservation of mass, the partial differential equation of gas potential with respect to time t can be finally obtained: Among them, φ w and φ g represents potential energy, Q g is the flux of the gas phase, ε represents the water content, and represents partial differential; Method for establishing the partial differential equation of the water phase: 1) Darcy's law is proportional to the potential gradient of the water phase, as follows: Among them, V w Indicates the water velocity in m 2 / s; K w Represents water relative permeability, unit is m 2 ;μ w Indicates viscosity, the unit is kg / m / s; φ w represents the water potential energy, φ w =P+ρgh; 2) According to the law of conservation of mass, equations (4) and (9) can be used to obtain the partial differential equation of water potential with respect to time t: Among them, Q w represents the flux of the water phase; S1-2, the partial differential equations of the gas phase and the water phase are processed by the implicit difference method of backward difference to obtain the corresponding linear discrete equations; The method to obtain the linear discrete equation of the gas phase is as follows: 1) Simplify the partial differential equation (5): 2) Order The partial differential equation (6) is discretized by backward difference: 3) Arrange formula (7) to obtain: The method to obtain the linear discrete equation corresponding to the water phase is as follows: 1) Simplify the partial differential equation (10): 2) Order The partial differential equation (11) is discretized by backward difference: 3) Arrange formula (12) to obtain: S1-3, combining the linear discrete equations obtained in step S1-2 to construct a model for predicting the distribution of methane concentration in porous media with depth and time; S2. Get training data According to the actual stratum, a simulated stratum column is set, wherein the simulated stratum column is set with a simulated cap layer, a simulated stratum and a simulated Quaternary sediment from bottom to top, wherein the simulated Quaternary sediment is set with two monitoring layers, the simulated stratum is set with four monitoring layers, and the simulated cap layer is set with one monitoring layer. Mixed hydrocarbon gas is injected from the bottom of the simulated stratum column to simulate the micro-leakage migration of methane gas in the reservoir under the real geology, and water is injected to simulate the saturated zone at the same time, and the pressure, temperature, methane concentration and flux of each monitoring layer at each time point are monitored; S3. Update the model obtained in step S1 using the data obtained in step S2.

2. The method for predicting the migration process of micro-leakage methane in porous media according to claim 1, characterized in that: In step S1-3, a model for predicting the distribution of methane concentration in porous media with depth and time is constructed, and its expression is as follows: 。 3. The method for predicting the migration process of micro-leakage methane in porous media according to claim 2, characterized in that: In step S3, the model for predicting the distribution of methane concentration in porous media with depth and time is updated to obtain: Transforming formula (15) into a form that is convenient for solving, we get:

4. A device for predicting the migration process of micro-leakage methane in porous media, characterized in that: The method comprises a data acquisition unit, a memory and a processor, wherein the memory stores a computer program that can be run on the processor, and the computer program run by the processor implements the method for predicting the migration process of micro-seepage methane in porous media as described in any one of claims 1 to 3.

5. The device for predicting the migration process of micro-leakage methane in porous media according to claim 4, characterized in that: The data acquisition unit includes a simulated formation column, a water tank and an air cylinder. The simulated formation column is provided with a simulated cap layer, a simulated formation and a simulated Quaternary sediment from bottom to top. The simulated Quaternary sediment is provided with two monitoring layers, the simulated formation is provided with four monitoring layers, and the simulated cap layer is provided with one monitoring layer. The water tank and the air cylinder are both connected to the bottom of the simulated formation column. A constant pressure flow pump and a water valve are provided between the water tank and the simulated formation column, and a pressure gauge is provided between the air cylinder and the simulated formation column.

Images