Porous medium permeability testing method

Abstract

The invention discloses a porous medium permeability testing method and relates to the field of porous material permeability testing. The porous medium permeability testing method comprises the following steps: taking the porosity and average pore size of a porous medium sample; determining the average porosity of a porous medium sample computational domain and generating a pore scale computational grid and a macroscale computational grid; performing pore scale and macro scale simulation on the flowing process of the fluid flowing through the porous medium sample, calculating to obtain the fluid mechanical energy loss of pore simulation when the flowing process reaches a stable condition and the fluid mechanical energy loss of macro simulation when the flowing process reaches the stable condition, and calculating the permeability constant and permeability of the porous medium sample. According to the porous medium permeability testing method provided by the embodiment of the invention, the dynamic behaviors of the solid and the fluid can be described at the same time, the porous medium permeability can be effectively measured through a numerical simulation method, a large number of complex pure fluid domain irregular discrete grids do not need to be depended on, and the calculation consumption and the calculation difficulty are greatly reduced.

Description

Technical Field

[0001] The present application relates to the field of porous material permeability testing, and in particular, to a porous medium permeability testing method. Background Art

[0002] The permeability of porous media is a measure of the ability of porous media to allow fluid to pass through. The property of porous media to allow fluid to pass through under a certain pressure difference is called permeability, and the ability to allow fluid to pass through is called permeability. The permeability of porous media is often expressed by Darcy's law.

[0003] The test methods for porous media permeability are generally divided into two categories, namely physical tests and numerical tests. Physical tests are conducted by injecting or pumping water into the porous medium, recording the changes in the amount of water in the medium, and calculating the permeability based on Darcy's law. Water pressure tests can also be conducted to record the changes in water pressure and water flow rate, and then calculate the permeability based on Darcy's law. Numerical tests are generally conducted through computational fluid dynamics simulations to predict the pressure loss of fluids passing through porous media under given flow rates, or to predict the flow rate of fluids passing through porous media under given pressure differentials, and the permeability is calculated using Darcy's law.

[0004] The physical test of porous media permeability has a long test cycle and relies on complex test equipment and test processes, which brings significant inconvenience to engineering application tests; and due to the microscopic differences of the tested samples and test errors, the permeability test results often have an order of magnitude deviation, which affects the engineering application effect. Numerical test methods have the advantages of short test cycles, relatively simple test processes, and good consistency of results, but traditional computational fluid dynamics methods can only consider pure fluid domains, that is, they need to draw irregular fluid domains outside the porous medium skeleton and generate complex irregular grids, which are computationally expensive, have poor accuracy, and poor computational stability. Summary of the invention

[0005] The purpose of this application is to provide a porous media permeability testing method, which can simultaneously describe the dynamic behavior of solids and fluids and effectively realize the measurement of porous media permeability through numerical simulation methods, without relying on a large number of complex pure fluid domain irregular discrete grids, greatly reducing calculation consumption and difficulty.

[0006] The embodiment of the present application is implemented as follows: The present invention provides a method for testing the permeability of a porous medium, which comprises the following steps: Get the porosity of porous media samples f and average pore size d ; In the range of porous media samples Oh Determine the computational domain U The average porosity , the generated grid cell size isx The pore-scale computational grid is based on the porosity f Mapping to obtain the porosity of each grid point of the pore-scale calculation grid f 1; The flow process of the fluid flowing through the porous medium sample is simulated at the pore scale, and the mechanical energy loss of the fluid simulated at the pore scale when the flow process reaches the stable condition is calculated: In the computational domain U The size of the internal generated grid cell is L The macro-scale computational grid is based on the porosity f Mapping to obtain the porosity of each grid point of the macro-scale computational grid f 2; Simulate the flow process of fluid through porous media samples at a macro scale and calculate the mechanical energy loss of the fluid in the macro simulation when the flow process reaches a stable condition; The permeability constant and permeability of the porous media sample are calculated based on the fluid mechanical energy loss of the pore simulation when the flow process reaches a stable condition and the fluid mechanical energy loss of the macroscopic simulation when the flow process reaches a stable condition.

[0007] In some alternative embodiments, 10 d ≤ U ≤ Oh .

[0008] In some optional embodiments, x ≤0.1 d .

[0009] In some optional embodiments, the flow process of the fluid flowing through the porous medium sample is simulated at the pore scale using the following governing equations based on the pore scale computational grid: ; ; In the formula, is the pore flow velocity at the next time step to be solved; For time; The porosity of each grid point of the grid is calculated for the pore scale; is the dynamic pressure, is the viscosity of the fluid; is the latest known pore flow velocity at the current time step; is the time step.

[0010] In some optional embodiments, the following formula is used to calculate the fluid mechanical energy loss of the pore simulation when the flow process reaches a stable condition: p pore : ; In the formula, p pore The mechanical energy loss of the fluid simulated by the pores when the flow process reaches stable conditions; The mechanical energy of the fluid after the pore-simulated fluid flows out of the porous medium sample. p 1 is the fluid pressure flowing out of the porous medium sample when the flow process of the pore simulation reaches the stable condition, u 1 is the fluid flow rate out of the porous media sample when the flow process of the pore simulation reaches the stable condition; The mechanical energy of the fluid before the pore-simulated fluid flows into the porous medium sample. p 0 is the fluid pressure flowing into the porous medium sample when the flow process of the pore simulation reaches the stable condition, u 0 is the fluid flow rate flowing into the porous media sample when the flow process of the pore simulation reaches the stable condition.

[0011] In some alternative embodiments, 16 d ≤ L .

[0012] In some optional embodiments, the flow process of the fluid flowing through the porous medium sample is simulated at a macroscale using the following control equation based on the macroscale computational grid: ; ; In the formula, is the pore flow velocity at the next time step to be solved; For time; The porosity of each grid point of the mesh is calculated for the macroscale; is the dynamic pressure, is the viscosity of the fluid; is the latest known pore flow velocity at the current time step; is the time step.

[0013] In some optional implementation schemes, the following formula is used to calculate the fluid mechanical energy loss obtained by macroscopic simulation under stable flow conditions: p macro : ; In the formula, p macro In order to achieve the fluid mechanical energy loss calculated by macroscopic simulation under stable flow conditions, is the fluid mechanical energy calculated after the macroscopically simulated fluid flows out of the porous medium sample. p 3 is the fluid pressure flowing out of the porous medium sample when the macroscopic simulated flow process reaches a stable condition,u 3 is the fluid flow rate out of the porous medium sample when the macroscopic simulated flow process reaches a stable condition; is the fluid mechanical energy before the fluid flows into the porous medium sample, p 2 is the fluid pressure flowing into the porous medium sample when the macroscopic simulated flow process reaches a stable condition, u 2 is the fluid flow rate flowing into the porous medium sample when the macroscopic simulated flow process reaches a stable condition.

[0014] In some optional embodiments, the permeability constant of the porous medium sample is calculated using the following formula: K 0: ; In the formula, p macro It is the fluid mechanical energy loss of macroscopic simulation when the flow process reaches stable conditions; p pore The mechanical energy loss of the fluid simulated by the pores when the flow process reaches stable conditions; is the average porosity of the computational domain U; is the viscosity of the fluid; is the time step.

[0015] In some optional embodiments, the permeability of the porous medium sample is calculated according to the following formula: ; In the formula, p macro It is the fluid mechanical energy loss of macroscopic simulation when the flow process reaches stable conditions; p pore The mechanical energy loss of the fluid simulated by the pores when the flow process reaches stable conditions; is the average porosity of the computational domain U; is the porosity of the porous medium sample; is the viscosity of the fluid; is the time step.

[0016] In some optional embodiments, the porosity of the porous medium sample Acquired using X-ray or optical imaging.

[0017] The beneficial effects of the present application are as follows: the porous medium permeability test method provided in the embodiment of the present application comprises the following steps: obtaining the porosity and average pore size of the porous medium sample; determining the calculation domain within the range of the porous medium sample; U The average porosity , the generated grid cell size is x The pore-scale computational grid is based on the porosity fMap the porosity of each grid point of the pore-scale calculation grid; simulate the flow process of the fluid flowing through the porous medium sample at the pore scale, and calculate the fluid mechanical energy loss of the pore simulation when the flow process reaches the stable condition: U The size of the internal generated grid cell is L The macro-scale computational grid is based on the porosity f Mapping obtains the porosity of each grid point of the macro-scale computational grid; performs macro-scale simulation of the flow process of the fluid flowing through the porous medium sample, and calculates the mechanical energy loss of the macro-simulated fluid when the flow process reaches a stable condition; calculates the permeability constant and permeability of the porous medium sample according to the mechanical energy loss of the pore-simulated fluid when the flow process reaches a stable condition and the mechanical energy loss of the macro-simulated fluid when the flow process reaches a stable condition. The porous medium permeability test method provided in the embodiment of the present application can effectively realize the measurement of the permeability of porous media through a numerical simulation method. The method can simultaneously describe the dynamic behavior of solids and fluids, does not need to rely on a large number of complex irregular discrete grids of pure fluid domains, supports the use of simple and regular computational grids, thereby greatly reducing computational consumption and computational difficulty, and solves the problem of long cycle and reliance on complex hardware equipment of traditional test methods. At the same time, it also overcomes the problem that traditional numerical simulation methods are difficult to calculate and analyze for complex porous media problems. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 A schematic flow chart of a porous media permeability testing method provided in an embodiment of the present application. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments.

[0021] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for which protection is sought, but merely represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0022] The characteristics and performance of the porous medium permeability testing method of the present application are further described in detail below in conjunction with the examples.

[0023] like Figure 1 As shown, the embodiment of the present application provides a porous medium permeability testing method, which includes the following steps: Step 1: Obtain the porosity of porous media samples f and average pore size d ; Optionally, use X-ray or optical imaging to obtain the porosity of porous media samples f ; Step 2: Within the scope of porous media samples Oh Determine the computational domain U The average porosity , the generated grid cell size is x The pore-scale computational grid is based on the porosity f Mapping to obtain the porosity of each grid point of the pore-scale calculation grid f 1; optional, 10 d ≤ U ≤ Oh ; optional, x ≤0.1 d .

[0024] Step 3: Simulate the flow process of the fluid through the porous medium sample at the pore scale, and calculate the fluid mechanical energy loss of the pore simulation when the flow process reaches a stable condition: Optionally, the following governing equations are used to simulate the flow of fluid through a porous medium sample at the pore scale: ; ; In the formula, is the pore flow velocity at the next time step to be solved, in m / s; is the time, in seconds; The porosity of each grid point of the pore-scale calculation grid, with a unit of 1; is the dynamic pressure, in m 2 / s 2 ; is the viscosity of the fluid, in m 2 / s; is the latest pore flow velocity known in the current time step, in m / s; is the time step in seconds.

[0025] Optionally, the following formula is used to calculate the fluid mechanical energy loss of the pore simulation when the flow process reaches the stable condition: p pore : ; In the formula, p pore The mechanical energy loss of the fluid simulated by the pores when the flow process reaches stable conditions; The mechanical energy of the fluid after the pore-simulated fluid flows out of the porous medium sample. p 1 is the fluid pressure flowing out of the porous medium sample when the flow process of the pore simulation reaches the stable condition, u 1 is the fluid flow rate out of the porous media sample when the flow process of the pore simulation reaches the stable condition; The mechanical energy of the fluid before the pore-simulated fluid flows into the porous medium sample. p 0 is the fluid pressure flowing into the porous medium sample when the flow process of the pore simulation reaches the stable condition, u 0 is the fluid flow rate flowing into the porous media sample when the flow process of the pore simulation reaches the stable condition.

[0026] Step 4: In the computational domain U The size of the internal generated grid cell is L The macro-scale computational grid is based on the porosity f Mapping to obtain the porosity of each grid point of the macro-scale computational grid f 2; optional, 16 d ≤ L .

[0027] Step 5: Perform a macroscopic simulation of the flow process of the fluid flowing through the porous medium sample, and calculate the macroscopic simulated fluid mechanical energy loss when the flow process reaches a stable condition.

[0028] Optionally, the following governing equations are used to simulate the flow of fluid through a porous medium sample at a macroscale: ; ; In the formula, in the formula, is the pore flow velocity at the next time step to be solved, in m / s; is the time, in seconds; The porosity of each grid point of the macro-scale calculation grid, with a unit of 1; is the dynamic pressure, in m 2 / s 2 ; is the viscosity of the fluid, in m 2 / s; is the latest pore flow velocity known in the current time step, in m / s; is the time step, in seconds.

[0029] Optionally, the following formula is used to calculate the fluid mechanical energy loss obtained by macroscopic simulation under stable flow conditions: p macro : ; In the formula, p macro In order to achieve the fluid mechanical energy loss calculated by macroscopic simulation under stable flow conditions, is the fluid mechanical energy calculated after the macroscopically simulated fluid flows out of the porous medium sample. p 3 is the fluid pressure flowing out of the porous medium sample when the macroscopic simulated flow process reaches a stable condition, u 3 is the fluid flow rate out of the porous medium sample when the macroscopic simulated flow process reaches a stable condition; is the fluid mechanical energy before the fluid flows into the porous medium sample, p 2 is the fluid pressure flowing into the porous medium sample when the macroscopic simulated flow process reaches a stable condition, u 2 is the fluid flow rate flowing into the porous medium sample when the macroscopic simulated flow process reaches a stable condition.

[0030] Step 6, calculating the permeability constant of the porous medium sample according to the fluid mechanical energy loss of the pore simulation when the flow process reaches a stable condition and the fluid mechanical energy loss of the macroscopic simulation when the flow process reaches a stable condition; Optionally, the permeability constant of the porous medium sample is calculated using the following formula: K 0: ; In the formula, p macro It is the fluid mechanical energy loss of macroscopic simulation when the flow process reaches stable conditions; p pore The mechanical energy loss of the fluid simulated by the pores when the flow process reaches stable conditions; is the average porosity of the computational domain U; is the viscosity of the fluid; is the time step.

[0031] Step 7: Calculate the permeability of the porous media sample.

[0032] Optionally, calculate the permeability of the porous media sample according to the following formula K : ; In the formula, p macroIt is the fluid mechanical energy loss of macroscopic simulation when the flow process reaches stable conditions; p pore The mechanical energy loss of the fluid simulated by the pores when the flow process reaches stable conditions; is the average porosity of the computational domain U; is the porosity of the porous medium sample; is the viscosity of the fluid; is the time step.

[0033] The porous media permeability testing method provided in the embodiment of the present application considers the fluid mechanics behavior of the porous media sample under pore simulation and macro simulation conditions respectively, and calculates the fluid mechanical energy losses of pore simulation and macro simulation when the flow process of the fluid flowing through the porous media sample reaches a stable condition, and then calculates the permeability constant and permeability of the porous media sample according to the fluid mechanical energy loss of pore simulation when the flow process reaches a stable condition and the fluid mechanical energy loss of macro simulation when the flow process reaches a stable condition. It can effectively realize the permeability measurement of porous media through numerical simulation methods. The numerical simulation method adopted in this method adopts a method that can simultaneously describe the solid and fluid dynamic behaviors, does not need to rely on a large number of complex pure fluid domain irregular discrete grids, supports the use of simple and regular calculation grids, thereby greatly reducing the calculation consumption and result difficulty, solves the problems of long cycle and dependence on complex hardware equipment of traditional test methods, and also overcomes the problems of traditional numerical simulation methods that cannot be calculated and difficult to analyze for complex porous media problems, and provides new ideas and methods for porous media permeability testing.

[0034] It should be noted that the porosity of the porous medium sample obtained in the porous medium permeability test method provided in this application is f is the local porosity of the porous medium sample, which is a quantity that varies with space. Similarly, the permeability of the porous medium sample calculated is also the corresponding local permeability, which is also a quantity that varies with space.

[0035] The embodiments described above are part of the embodiments of the present application, rather than all of the embodiments. The detailed description of the embodiments of the present application is not intended to limit the scope of the present application for protection, but merely represents the selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present application.

Claims

1. A porous medium permeability testing method, characterized in that: It includes the following steps: Get the porosity of porous media samples φ and average pore size d ; In the range of porous media samples Ω Determine the computational domain U The average porosity , the generated grid cell size is x The pore-scale computational grid is based on the porosity φ Mapping to obtain the porosity of each grid point of the pore scale calculation grid φ 1; The flow process of the fluid flowing through the porous medium sample is simulated at the pore scale, and the mechanical energy loss of the fluid simulated in the pore when the flow process reaches a stable condition is calculated: In the computational domain U The size of the internal generated grid cell is L The macro-scale computational grid is based on the porosity φ Mapping to obtain the porosity of each grid point of the macro-scale computational grid φ 2; Simulate the flow process of fluid through porous media samples at a macroscopic scale and calculate the mechanical energy loss of the fluid in the macroscopic simulation when the flow process reaches a stable condition; The permeability constant and the permeability of the porous medium sample are calculated according to the fluid mechanical energy loss of pore simulation when the flow process reaches a stable condition and the fluid mechanical energy loss of macroscopic simulation when the flow process reaches a stable condition.

2. The porous medium permeability testing method according to claim 1, characterized in that: 10 d ≤ U ≤ Ω 。 3. The porous medium permeability testing method according to claim 1, characterized in that: x ≤0.1 d 。 4. The porous medium permeability testing method according to claim 1, characterized in that: The flow process of the fluid through the porous media sample is simulated at the pore scale using the following governing equations based on the pore scale computational grid: ； ； In the formula, is the pore flow velocity at the next time step to be solved; For time; calculating a porosity at each grid point of the grid for the pore scale; is the dynamic pressure, is the viscosity of the fluid; is the latest known pore flow velocity at the current time step; is the time step.

5. The porous medium permeability testing method according to claim 4, characterized in that: The following formula is used to calculate the fluid mechanical energy loss of pore simulation when the flow process reaches stable conditions: p pore : ； In the formula, p pore The mechanical energy loss of the fluid simulated by the pores when the flow process reaches stable conditions; The mechanical energy of the fluid after the pore-simulated fluid flows out of the porous medium sample. p 1 is the fluid pressure flowing out of the porous medium sample when the flow process of the pore simulation reaches a stable condition, u 1 is the flow rate of the fluid flowing out of the porous medium sample when the flow process of the pore simulation reaches a stable condition; The mechanical energy of the fluid before the pore-simulated fluid flows into the porous medium sample. p 0 is the fluid pressure flowing into the porous medium sample when the flow process of the pore simulation reaches a stable condition, u 0 is the fluid flow rate flowing into the porous medium sample when the flow process of the pore simulation reaches a stable condition.

6. The porous medium permeability testing method according to claim 1, characterized in that: 16 d ≤ L 。 7. The porous medium permeability testing method according to claim 1, characterized in that: The following control equations are used based on the macro-scale computational grid to simulate the flow process of the fluid through the porous medium sample at a macro-scale: ； ； In the formula, is the pore flow velocity at the next time step to be solved; For time; calculating the porosity of each grid point of the grid for the macroscale; is the dynamic pressure, is the viscosity of the fluid; is the latest known pore flow velocity at the current time step; is the time step.

8. The porous medium permeability testing method according to claim 7, characterized in that: The following formula is used to calculate the fluid mechanical energy loss obtained by macroscopic simulation under stable flow conditions: p macro : ； In the formula, p macro In order to achieve the fluid mechanical energy loss calculated by macroscopic simulation under stable flow conditions, is the fluid mechanical energy calculated after the macroscopically simulated fluid flows out of the porous medium sample. p 3 is the fluid pressure flowing out of the porous medium sample when the macroscopically simulated flow process reaches a stable condition, u 3 is the flow rate of the fluid flowing out of the porous medium sample when the macroscopically simulated flow process reaches a stable condition; is the fluid mechanical energy before the fluid flows into the porous medium sample, p 2 is the fluid pressure flowing into the porous medium sample when the macroscopic simulated flow process reaches a stable condition, u 2 is the fluid flow rate flowing into the porous medium sample when the macroscopically simulated flow process reaches a stable condition.

9. The porous medium permeability testing method according to claim 1, characterized in that: The permeability constant of the porous medium sample is calculated using the following formula: K 0: ； In the formula, p macro It is the fluid mechanical energy loss of macroscopic simulation when the flow process reaches stable conditions; p pore The mechanical energy loss of the fluid simulated by the pores when the flow process reaches stable conditions; is the average porosity of the computational domain U; is the viscosity of the fluid; is the time step.

10. The porous medium permeability testing method according to claim 1, characterized in that: The permeability of the porous medium sample was calculated according to the following formula: ； In the formula, p macro It is the fluid mechanical energy loss of macroscopic simulation when the flow process reaches stable conditions; p pore The mechanical energy loss of the fluid simulated by the pores when the flow process reaches stable conditions; is the average porosity of the computational domain U; is the porosity of the porous medium sample; is the viscosity of the fluid; is the time step.

11. The porous medium permeability testing method according to claim 1, characterized in that: The porosity of the porous medium sample Acquired using X-ray or optical imaging.

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