Porous medium imbibition simulation method and system considering dynamic contact angle effect

Abstract

The invention relates to the field of porous medium fluid flowing and oil-gas field development, in particular to a porous medium imbibition simulation method and system considering a dynamic contact angle effect. According to the porous medium imbibition simulation method and system considering the dynamic contact angle effect, the dynamic contact angle effect is considered, aiming at different application scenes, different dynamic contact angle theories are adapted, and the dynamic contact angle theories and a two-phase imbibition mathematical model are coupled, so that the porous medium imbibition simulation method and system considering the dynamic contact angle effect are provided; the influence of the dynamic contact angle effect on the porous medium imbibition can be effectively analyzed, and the porous medium imbibition simulation theory and method are perfected.

Description

Technical Field

[0001] The invention relates to the fields of porous medium fluid flow and oil and gas field development, and in particular to a porous medium imbibition simulation method and system considering dynamic contact angle effect. Background Art

[0002] Porous media imbibition is one of the most common phenomena in nature, such as rainwater absorption on the ground, water absorption on towels, and water absorption on diapers. Porous media imbibition also has important applications in the engineering field, such as nanoporous material manufacturing and enhanced oil and gas recovery. Taking the background of enhanced oil and gas recovery as an example, the imbibition method has been widely used in fractured reservoirs and carbonate reservoirs. Fractures are developed in fractured and carbonate reservoirs, which will form two systems of reservoir matrix and fractures. The matrix permeability is low and the fracture permeability is high. Under the action of capillary pressure, the wetting phase (usually water) in the fracture system is imbibed into the matrix system, and then the non-wetting phase (usually oil or gas) of the matrix system is discharged and flows into the fractures.

[0003] At present, imbibition oil recovery is being studied intensively in tight oil reservoirs. The pore throat scale of tight oil and gas reservoirs is mainly nanometer scale, and the capillary pressure effect is more significant. Through large-scale volume fracturing, a large number of artificial fractures are generated, creating conditions for imbibition oil recovery. The dynamic contact angle effect refers to the change of the three-phase contact angle with the change of fluid velocity due to the friction of the contact line of the three phases (solid phase, wetting phase and non-wetting phase) during the flow or imbibition process. The dynamic contact angle effect has been widely studied and applied in single-tube or single-pore imbibition. However, the flow law of the wetting phase and the non-wetting phase in porous media (such as rocks) is complex, and the influence of the dynamic contact angle effect on imbibition is still unclear. Summary of the invention

[0004] The present invention takes into account the dynamic contact angle effect, adapts different dynamic contact angle theories for different application scenarios, and proposes a porous media imbibition simulation method and system considering the dynamic contact angle effect by coupling the dynamic contact angle theory and the two-phase imbibition mathematical model. The method and system can effectively analyze the influence of the dynamic contact angle effect on the porous media imbibition.

[0005] The present invention proposes a porous media imbibition simulation method and system considering the dynamic contact angle effect, and the specific steps include: 1) Determine the basic parameters of the porous media imbibition system under study; The basic parameters include fluid data and porous medium data; 2) Select the dynamic contact angle theory; The dynamic contact angle theory includes: molecular dynamics theory, hydrodynamics theory, and empirical model; 3) Establish a two-phase imbibition mathematical model; 4) Coupling dynamic contact angle theory and two-phase imbibition mathematical model; 5) Set the corresponding fluid pressure and boundary conditions according to the actual imbibition conditions; 6) Simulation solution.

[0006] During the flow of porous media fluid, due to the friction of the three-phase contact line, the three-phase contact angle is not fixed, but changes with the fluid velocity.

[0007] The present invention provides three dynamic contact angle theories for application in different scenarios: When the application scenario is a solid-liquid-liquid system at the micro-nano scale, choose molecular dynamics theory; When the application scenario is a solid-liquid-gas system at the micro-nano scale, choose molecular dynamics theory or hydrodynamics theory; When the application scenario is a solid-liquid-gas system at a conventional scale, choose an empirical model or hydrodynamic theory.

[0008] The micro-nano scale refers to pores less than or equal to 1 μm; the conventional scale refers to pores greater than 1 μm.

[0009] (1) Molecular dynamics theory The relationship between the three-phase contact line velocity and the dynamic contact angle is as follows: (1); Where: U is the contact line velocity, m / s; γ is the interfacial tension between the two phases of fluid, N / m; is the three-phase contact line friction coefficient, Pa·s; θ st is the static contact angle, °; θ d is the dynamic contact angle, °.

[0010] For the solid-liquid-gas system, considering the viscosity of the fluid and the solid-fluid interaction, the friction coefficient of the three-phase contact line can be further expressed as: (2); Where: μ is the fluid viscosity, Pa·s; V is the volume of a single fluid molecule, m 3 ; λ is the jump length of the fluid molecules, m; k B is the Boltzmann constant, 1.38×10 −23 J / K; T is the temperature, K; the subscript w indicates the wetting phase.

[0011] For a solid-liquid-liquid system, the three-phase contact line friction coefficient can be expressed as: (3); Where: η ing is the displacement phase viscosity, Pa·s; V ing is the molar volume of the displacing phase molecules, m 3 / mol; x ing is the displacement phase viscosity fraction; η ed is the viscosity of the displaced phase, Pa·s; V ed is the molar volume of the displaced phase molecules, m 3 / mol; x ed is the viscosity fraction of the displaced phase; A and B are the coefficients related to flow-flow interaction (viscous effect) and solid-flow interaction, respectively; A Usually it can be taken as 1, B It can be obtained by fitting experimental data; h p is Planck's constant.

[0012] The present invention uses molecular dynamics theory to comprehensively consider the characteristics of fluid viscosity and solid-fluid interaction, and applies it to a solid-fluid system at a micro-nano scale. More preferably, the solid-fluid system is a solid-liquid-liquid system.

[0013] (2) Hydrodynamic theory (4); Where: g ( θ ) is ; Ca is the capillary number; χ is a constant that is related to the length of the capillary or porous medium and the strength of the solid-liquid interaction.

[0014] For a solid-liquid-gas system, the above equation can be simplified to: (5); Where: L is the characteristic length of the capillary; L s is the slip length.

[0015] The present invention utilizes the hydrodynamic theory to emphasize the viscous dissipation of the three-phase contact zone, and comprehensively considers the influence of the capillary number and the fluid slip, and applies it to the solid-liquid-gas system.

[0016] (3) Empirical model The empirical model is one of the formulas (6) to (8): (6); (7); (8); Where: A 0 and B 0 is an empirical constant obtained by fitting.

[0017] The present invention utilizes the characteristics of the empirical model derived from experimental data, and comprehensively considers the difficulty of conducting dynamic wetting experiments on different solid-fluid systems, and applies it to the solid-liquid-gas system; more preferably, the solid-liquid-gas system is a solid-liquid-gas system at a conventional scale.

[0018] In step 3), the method for establishing a two-phase imbibition mathematical model is as follows: In the x-direction, the mass conservation equation is as follows: (9); Where: v is the Darcy speed, m / s; x is the distance, along the core axis, m; is the porosity, a decimal; S is the saturation, a decimal; t is the time, s; subscript β Indicates wetting or non-wetting phase; In the x-direction, the flow equation is as follows: (10); Where: k is the porous medium permeability, m 2 ; k r is the relative permeability, dimensionless; P is the pressure, Pa; μ is the fluid viscosity, Pa·s. In step 4), the method of coupling the dynamic contact angle effect theory and the two-phase imbibition mathematical model is as follows: The coupled dynamic contact angle theory and two-phase imbibition mathematical model are shown below: (11); Where: P cd is the dynamic capillary pressure; a and b is the coefficient in the J function that characterizes the capillary pressure and is dimensionless; S wnis the normalized water saturation and is dimensionless.

[0019] According to the definition of capillary pressure (capillary pressure is the pressure difference between the non-wetting phase and the wetting phase at the interface between the two phases), formula (11) is derived through the mass conservation equation and the flow equation.

[0020] Specifically, the molecular dynamics theory is coupled with the two-phase imbibition mathematical model, and the dynamic capillary pressure of the solid-liquid-gas system at the micro-nano scale is: (12); Specifically, the molecular dynamics theory is coupled with the two-phase imbibition mathematical model, and the dynamic capillary pressure of the solid-liquid-liquid system at the micro-nano scale is: (13); Specifically, the hydrodynamic theory is coupled with the two-phase imbibition mathematical model, and the dynamic capillary pressure of the solid-liquid-gas system is: (14); Specifically, the empirical model is coupled with the two-phase imbibition mathematical model, and the dynamic capillary pressure of the solid-liquid-gas system at a conventional scale is: (15); (16); (17).

[0021] When the normalized water saturation reaches 1, the dynamic capillary pressure is equal to the capillary back pressure or threshold pressure, and the fluid velocity is close to zero. The capillary back pressure can be expressed as: (18).

[0022] In step 5), the fluid pressure includes an inlet boundary pressure and an outlet boundary pressure; wherein the difference between the inlet boundary pressure and the internal pressure of the porous medium at the initial moment is equal to the capillary back pressure, and the outlet boundary pressure is equal to the internal pressure of the porous medium.

[0023] The boundary conditions can be set to be open or closed according to requirements, that is, they can be in contact with or not in contact with the ambient fluid, thereby controlling whether the imbibition process occurs.

[0024] In step 6), the simulation method of steps 1) to 5) is solved by programming or embedding it into simulation software.

[0025] Preferably, the simulation software is Comsol Multiphysics software.

[0026] The porous media imbibition simulation method considering the dynamic contact angle effect provided by the present invention can accurately describe the influence of the dynamic wetting angle effect on the porous media imbibition, and can be applied to different wettability, viscosity systems, interfacial tension, permeability and other systems, thus improving the porous media imbibition simulation theory and method.

[0027] An embodiment of the present invention further provides a porous medium imbibition simulation system taking into account the dynamic contact angle effect, the system comprising: an equation building module, a coupling module, and a simulation solution module.

[0028] The equation establishment module is used to select the dynamic contact angle theory and establish a two-phase imbibition mathematical model; the coupling module characterizes the J function through capillary pressure, couples the dynamic contact angle theory and the established two-phase imbibition mathematical model; the simulation solution module can perform simulation solution based on the coupled dynamic contact angle theory and the two-phase imbibition mathematical model.

[0029] Compared with the prior art, the advantages of the present invention are: Based on the existing theory, the present invention considers the influence of the dynamic contact angle effect and proposes a porous medium imbibition simulation method. According to the present invention, the influence of the dynamic contact angle effect on the porous medium imbibition can be accurately described, and can be applied to different fluid imbibition systems and different porous medium imbibition systems. The present invention has broad application prospects in fluid flow, petroleum engineering and nano-micro porous material production, especially in the field of oil field development. The simulation method will further improve the imbibition oil production method and theory. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] 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 are briefly introduced below.

[0031] Figure 1 It is a flow chart of the application of the simulation method in the embodiment of the present invention; Figure 2 A three-dimensional porous medium grid cross section according to an embodiment of the present invention; Figure 3 The YZ plane water saturation distribution of the porous medium at different imbibition moments in the embodiment of the present invention; Figure 4 The distribution of oil-water streamlines in the XY plane of the porous medium at different imbibition moments in the embodiment of the present invention; Figure 5 The capillary pressure distribution of the porous medium in the XY plane at different imbibition moments in the embodiment of the present invention; Figure 6 Comparison of the imbibition amount simulated by the method of the present invention and the traditional method in the embodiments of the present invention; Figure 7Comparison of the recovery degree simulated by the method of the present invention and the traditional method in the embodiment of the present invention; Figure 8 is the average water saturation change calculated by the method of the present invention in the embodiments of the present invention; Fig. 9 is the average capillary pressure change calculated by the method of the present invention in the embodiment of the present invention; Fig.10 Diagram of porous media imbibition simulation system considering dynamic contact angle effect; Among them, the method of the present invention refers to a research method based on the present invention that takes into account the dynamic contact angle effect; the traditional method refers to a research method that does not take into account the dynamic contact angle effect, that is, a research method when the friction coefficient of the three-phase contact line is zero. DETAILED DESCRIPTION

[0032] In order to make the purpose, scheme and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments and the accompanying drawings. Here, the illustrative embodiments of the present invention and their descriptions are used to explain the present invention, but are not intended to limit the present invention. Without violating the purpose of the present invention and the claims, a variety of similar representations can be made, and such changes all fall within the scope of protection of the present invention.

[0033] The main implementation steps of the present invention are as follows (see Figure 1 ): Step 101: First, determine the basic parameters of the porous medium imbibition system, including fluid data, porous medium data, etc., to provide a basis for subsequent simulation solutions; Step 102: According to the content provided by the present invention, select a suitable dynamic contact angle effect theory and calculate relevant parameters; Step 103: According to the present invention, a two-phase imbibition mathematical model is established; Step 104: coupling the dynamic contact angle theory and the two-phase imbibition mathematical model according to the present invention; Step 105: Calculate the capillary back pressure according to the present invention and set a suitable initial pressure and boundary pressure of the fluid; Step 106: Perform simulation solution and application.

[0034] The above method of the present invention is further described below with reference to specific embodiments.

[0035] Example The imbibition process is affected by many factors, including fluid interfacial tension, fluid viscosity, porous medium wettability, porous medium permeability, porous medium imbibition boundary conditions, etc. This embodiment is based on the fully open boundary conditions of the porous medium, and simulates the influence of the dynamic contact angle effect on the imbibition in the fully open boundary. The imbibition simulation under other influencing factors can be implemented with reference to this example, and also belongs to the protection scope of the present invention.

[0036] in accordance with Figure 1 First, determine the basic data of the porous medium imbibition system, including fluid viscosity, density, oil-water interfacial tension, porous medium porosity, permeability, etc. The wetting phase in the fluid properties is water, and the non-wetting phase is the main component of shale oil; the porous medium is a cuboid, and the material is quartz; the porous medium imbibition boundary condition is a fully open boundary, that is, all end faces of the porous medium can undergo imbibition. The basic parameters of the porous medium imbibition system are shown in Table 1.

[0037] Table 1 Basic parameters of porous media imbibition system parameter Parameter Value Permeability / mD 0.1 Porosity / decimal 0.1 Porous medium length / cm 6 Porous media width / cm 5 Porous medium height / cm 5 Immune water saturation / decimal 0.35 Residual oil saturation / decimal 0.50 Water phase viscosity / Pa·s 0.001 Oil phase viscosity / Pa·s 0.001 Oil-water interfacial tension / mN / m 48 Static contact angle / ° 30 Secondly, the main parameters are calculated according to the present invention. Based on the parameters in Table 1, according to the capillary pressure formula (18), the capillary back pressure can be calculated to be 0.083 MPa.

[0038] Then, according to the present invention, the dynamic contact angle theory is preferred. The porous medium in this example is a low-permeability dense medium, belonging to the micro-nano scale, and the object is a solid-liquid-liquid system. Therefore, the dynamic contact angle effect is characterized by the molecular dynamics theory. According to the three-phase contact line friction coefficient formula (3), the calculated three-phase contact line friction coefficient is 25 Pa·s, where η ing is 0.001Pa·s; V ing is 2.99×10 -29 m 3 / mol; x ing is 0.5; η ed is 0.001 Pa·s; V ed is 3.78×10 -28 m 3 / mol; x ed is 0.5; A is 1, B is 1; h p is 6.62607×10 -34 J.S.

[0039] If the friction coefficient of the three-phase contact line is zero, it means that the dynamic contact angle effect is not considered, which belongs to the static imbibition process of the traditional method; if the friction coefficient of the three-phase contact line is not zero, it means that the dynamic contact angle effect is considered, which belongs to the dynamic imbibition process of the method of the present invention.

[0040] Finally, by coupling the dynamic contact angle theory and the two-phase imbibition mathematical model, the simulation results of porous media imbibition considering the dynamic contact angle effect can be obtained through simulation and solution using Comsol Multiphysics software. The coupling formula of the dynamic contact angle theory and the two-phase imbibition mathematical model is: (13).

[0041] Attached Figure 2 The shape of the porous medium is not limited to the rectangular parallelepiped shape of the present embodiment, and any shape can cause the imbibition process.

[0042] Attached Figure 3 It is the water saturation distribution of the porous medium in the YZ plane at different imbibition moments in the embodiment of the present invention. The color bar in the figure means the water saturation. At 1s, the imbibition starts from the surrounding boundary, the water saturation inside the porous medium does not change, and the water saturation at the boundary begins to change slightly; at 100s, the scope of the imbibition process is still small; at 1000s, the scope of the imbibition process is significantly increased, the water saturation inside the porous medium is significantly increased, and the oil saturation is significantly reduced; at 3548.1s, the imbibition process is nearing the end, and the oil inside the porous medium is driven out.

[0043] Attached Figure 4 The figure shows the distribution of oil-water streamlines in the XY plane of the porous medium at different imbibition moments in the embodiment of the present invention. The color bar in the figure means the water saturation, where the pink arrow represents the oil phase and the green arrow represents the water phase. At 1s, imbibition starts from the surrounding boundary, the fluid equilibrium state inside the porous medium is broken, and the oil-water streamlines are very chaotic; at 100s, the oil-water streamlines are still relatively chaotic; at 1000s, the imbibition has been carried out stably, and the oil-water streamlines are relatively uniform; at 3548.1s, the imbibition process has basically ended, the fluid has been basically redistributed, and the oil-water streamlines are more uniform and stable.

[0044] Attached Figure 5The capillary pressure distribution of the porous medium in the XY plane at different imbibition moments in the embodiment of the present invention, and the color bar in the figure means the capillary pressure. At 1s, the imbibition starts from the surrounding boundary, the water saturation at this time is small, the capillary pressure is maximum, and the imbibition speed is fastest; at 100s, the water saturation is still small, the capillary pressure is still large, and the imbibition speed is fast; at 1000s, the scope of the imbibition process is significantly increased, the water saturation inside the porous medium is significantly increased, and the capillary pressure decreases; at 3548.1s, the imbibition process has basically ended, the water saturation approaches the maximum, and the capillary pressure develops towards the minimum direction.

[0045] Attached Figure 6 It is a comparison of the imbibition amount simulated by the method of the present invention and the traditional method in the embodiment of the present invention. As can be seen from the figure, in the early and middle stages, the imbibition amount of static imbibition is greater than the dynamic imbibition amount, indicating that in the early and middle stages, the traditional research method overestimates the imbibition amount. In the later stage, the amount of static imbibition and dynamic imbibition is equal, mainly because the initial oil-containing volume of the porous medium is the same, so the final imbibition volume is equal.

[0046] Attached Figure 7 It is a comparison of the recovery degree simulated by the method of the present invention and the traditional method in the embodiment of the present invention. As can be seen from the figure, with the same change in the imbibition amount, the recovery degree simulated by the traditional method is higher than the recovery degree simulated by the present invention, that is, the recovery degree after considering the dynamic contact angle effect is lower than that without considering the dynamic contact angle effect. The main reason is that the dynamic contact angle effect is the resistance in the imbibition process. The larger the dynamic contact angle effect, the more unfavorable it is for the imbibition effect.

[0047] Attached Figure 8 It is the average water saturation change calculated by the method of the present invention in the embodiment of the present invention. As can be seen from the figure, the same as the two-dimensional water saturation, as the imbibition time increases, the water saturation of the porous medium gradually increases, and a large amount of oil is driven out.

[0048] Attached Fig. 9 It is the average capillary pressure change calculated by the method of the present invention in the embodiment of the present invention. As can be seen from the figure, as the imbibition time increases, the water saturation of the porous medium increases, and the capillary pressure between the oil-water phases gradually decreases, which is consistent with the basic understanding.

[0049] The embodiment of the present invention also provides a porous medium imbibition simulation system considering the dynamic contact angle effect. Fig.10 As shown, including: Equation establishment module 1001: Select an appropriate dynamic contact angle theory. The present invention provides three main dynamic contact angle theories. A two-phase imbibition mathematical model is established, including the main mass conservation equation, motion equation, capillary pressure equation, etc.

[0050] Coupling module 1002: Through the capillary pressure J function, the dynamic contact angle theory and the established two-phase imbibition mathematical model are coupled to lay the foundation for subsequent solutions.

[0051] Simulation solution module 1003: Based on the coupled dynamic contact angle theory and the two-phase imbibition mathematical model, a simulation program can be compiled by the user to perform simulation solution or it can be embedded in Comsol Multiphysics software for solution.

[0052] It should be understood that in various embodiments of the present invention, the size of the serial numbers of the above-mentioned processes does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0053] Those of ordinary skill in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described in terms of function in the above description. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0054] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0055] In the embodiments provided in the present application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interfaces, devices or units, or it can be an electrical, mechanical or other form of connection.

[0056] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the embodiments of the present invention.

[0057] In addition, each functional unit in the embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0058] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention is essentially or the part that contributes to the prior art, or all or part of the technical solution can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, server, or network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk and other media that can store program codes.

[0059] The present invention uses specific embodiments to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation on the present invention.

Claims

1. A porous media imbibition simulation method considering dynamic contact angle effect, characterized in that: The specific steps include: 1) Determine the basic parameters of the porous media imbibition system; The basic parameters include fluid data and porous medium data; 2) Select the dynamic contact angle theory; The dynamic contact angle theory includes: molecular dynamics theory, hydrodynamics theory, and empirical model; 3) Establish a two-phase imbibition mathematical model; 4) Coupling dynamic contact angle theory and two-phase imbibition mathematical model; 5) Based on the coupling results, calculate the capillary back pressure and set the fluid pressure and boundary conditions; 6) Simulation solution; When the application scenario is a solid-liquid-liquid system at the micro-nano scale, choose molecular dynamics theory; When the application scenario is a solid-liquid-gas system at the micro-nano scale, choose molecular dynamics theory or hydrodynamics theory; When the application scenario is a solid-liquid-gas system at a conventional scale, choose an empirical model or hydrodynamic theory; The micro-nano scale refers to pores less than or equal to 1 μm; the conventional scale refers to pores greater than 1 μm.

2. The porous media imbibition simulation method considering dynamic contact angle effect according to claim 1, characterized in that: In step 3), the method for establishing a two-phase imbibition mathematical model is as follows: In the x-direction, the mass conservation equation is: （9）； Where: v is the Darcy speed, m / s; x is the distance, along the core axis, m; is the porosity, a decimal; S is the saturation, a decimal; t is time, s; Subscript β Indicates wetting or non-wetting phase; In the x direction, the flow equation is: （10）； Where: k is the porous medium permeability, m 2 ; k r is the relative permeability, dimensionless; P is the pressure, Pa; μ is the fluid viscosity, Pa·s.

3. The porous media imbibition simulation method considering the dynamic contact angle effect according to claim 2, characterized in that: In step 4), the method of coupling the dynamic contact angle effect theory and the two-phase imbibition mathematical model is as follows: （11）； Where: P cd is the dynamic capillary pressure; γ is the interfacial tension between the two phases of fluid, N / m; θ d is the dynamic contact angle, °; a and b is the coefficient in the J function that characterizes the capillary pressure and is dimensionless; S wn is the normalized water saturation and is dimensionless.

4. The porous media imbibition simulation method considering dynamic contact angle effect according to claim 3, characterized in that: In the molecular dynamics theory, the relationship between the three-phase contact line velocity and the dynamic contact angle is: （1）； Where: U is the contact line velocity, m / s; γ is the interfacial tension between the two phases of fluid, N / m; is the three-phase contact line friction coefficient, Pa·s; θ st is the static contact angle, °; θ d is the dynamic contact angle, °; For the solid-liquid-gas system, the three-phase contact line friction coefficient for: （2）； Where: μ is the fluid viscosity, Pa·s; V is the volume of a single fluid molecule, m 3 ; λ is the jump length of the fluid molecule, m; k B is the Boltzmann constant, 1.38×10 −23 J / K; T is the temperature, K; the subscript w indicates the wetting phase; For a solid-liquid-gas system, the dynamic capillary pressure is: （12）； For a solid-liquid-liquid system, the three-phase contact line friction coefficient for: （3）； Where: η ing is the displacement phase viscosity, Pa·s; V ing is the molar volume of the displacing phase molecules, m 3 / mol; x ing is the displacement phase viscosity fraction; η ed is the viscosity of the displaced phase, Pa·s; V ed is the molar volume of the displaced phase molecules, m 3 / mol; x ed is the viscosity fraction of the displaced phase; A and B are the coefficients related to flow-flow interaction and solid-flow interaction, respectively; h p is Planck's constant; For a solid-liquid-liquid system, the dynamic capillary pressure is: （13）。 5. The porous media imbibition simulation method considering dynamic contact angle effect according to claim 3, characterized in that: In the hydrodynamic theory, （4）； Where: g ( θ ) is ; Ca is the capillary number; χ is a constant related to the length of the capillary or porous medium and the strength of the solid-liquid interaction; For the solid-liquid-gas system, formula (4) can be simplified as: （5）； Where: L is the characteristic length of the capillary; L s is the slip length; For a solid-liquid-gas system, the dynamic capillary pressure is: （14）。 6. The porous media imbibition simulation method considering dynamic contact angle effect according to claim 3, characterized in that: The empirical model is one of the formulas (6) to (8): （6）； （7）； （8）； Where: A 0 and B 0 is an empirical constant obtained by fitting; The dynamic capillary pressure is one of the equations (15) to (17): （15）； （16）； （17）。 7. The porous media imbibition simulation method considering dynamic contact angle effect according to claim 1, characterized in that: In step 5), the fluid pressure includes an inlet boundary pressure and an outlet boundary pressure; the difference between the inlet boundary pressure and the internal pressure of the porous medium at the initial moment is equal to the capillary back pressure, and the outlet boundary pressure is equal to the internal pressure of the porous medium; The boundary condition is set to open or closed.

8. The porous media imbibition simulation method considering dynamic contact angle effect according to claim 1, characterized in that: In step 6), the simulation solution method is to program the simulation method of steps 1) to 5) or embed it into simulation software for solution.

9. A porous media imbibition simulation system considering dynamic contact angle effect based on the method according to any one of claims 1 to 8, characterized in that: The system comprises: an equation building module, a coupling module, and a simulation solution module; The equation building module is used to select the dynamic contact angle theory and establish a two-phase imbibition mathematical model; The coupling module characterizes the J function through capillary pressure, coupling the dynamic contact angle theory and the established two-phase imbibition mathematical model; The simulation solution module performs simulation solution based on coupled dynamic contact angle theory and two-phase imbibition mathematical model.

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