Prediction method and system for realizing porous medium microscopic two-phase interface imbibition behavior

Abstract

The invention belongs to the technical field of microcosmic interface dynamic research, and relates to a method and system for predicting the imbibition behavior of a microcosmic two-phase interface of a porous medium, and the method comprises the steps: obtaining a pore network composed of pores and throats according to a target porous medium; calculating the flow of the two-phase fluid injected into the throat; according to the flow of the two-phase fluid injected into the throat, the flow of the fluid in the main interface displacement mode and the flow of the fluid in the wetting mode displacement mode are calculated; determining the displacement mode of the two-phase fluid interface according to the fluid flow ratio under the two displacement modes; according to the displacement mode of the two-phase fluid interface, the flow resistance corresponding to the throat is calculated; according to the flow resistance, a motion control equation of the two-phase fluid is updated, and therefore prediction of the imbibition behavior of the micro two-phase interface of the porous medium is completed. According to the method, the preferential flow paths and the dynamic evolution modes of different types of interfaces in the displacement process in the pore structure of the complex porous medium are defined, and the types of the fluid interfaces are accurately judged under the transient condition.

Description

Technical Field

[0001] The present invention relates to a method and system for predicting the imbibition behavior of a microscopic two-phase interface of a porous medium, and belongs to the technical field of microscopic interface dynamics research. Background Art

[0002] In many energy and environmental engineering fields involving multiphase flow, such as oil and gas development, geological storage of carbon dioxide, shale oil and gas extraction, and underground hydrogen storage, the imbibition behavior of fluids in porous media and the microscopic interface dynamics play a decisive role in macroscopic flow patterns and development efficiency. This type of imbibition process is usually a two-phase flow, exhibiting complex interfacial behaviors such as fingering, Haines jumps, capillary-driven corner flow, and main bend liquid surface intrusion. Especially in heterogeneous porous media, the competition between capillary and viscous forces determines the migration path, retention pattern, and displacement efficiency of fluids in the pores, and is an important basis for influencing the distribution of remaining oil in the reservoir, recovery rate, and injection and production control strategies.

[0003] In existing research, although a large number of microfluidic experiments and numerical simulations have made significant progress in revealing the dynamics of microscopic interfaces, there are still problems such as complex modeling, high consumption of computing resources, and limited scale, which make it difficult to directly apply to macroscopic reservoir simulation and engineering design. In addition, most studies focus on the interface propulsion mode dominated by the main curved liquid surface, ignoring the impact of "incomplete displacement paths" such as corner flow on the imbibition process and its macroscopic effects. In fact, in the complex pore structure of the core, the wetting film flow formed by the expansion of the wetting phase along the corners of the pore plays a key role in maintaining connectivity and inducing unstable displacement during the low-speed imbibition process, directly affecting the retention, fracture and re-migration behavior of the non-wetting phase.

[0004] Traditional network models have achieved simplified modeling of pore-scale seepage processes to a certain extent, but they are still insufficient in describing the dynamic competition between the main interface flow and the wetting film and predicting the microscopic interface transition behavior. Especially in heterogeneous or complex porous media, how to accurately predict which local areas dominate the corner flow wetting film or main interface intrusion and its impact on the overall displacement behavior still lacks a theoretically complete modeling framework and numerical tools. Some studies have attempted to decompose the pores into multiple sub-channels to construct a fine network model to simulate the coexistence of main interface flow and wetting film flow. However, this type of model has a large amount of computation and is difficult to obtain parameters, making it difficult to meet the needs of multi-scale simulation and rapid prediction in engineering.

[0005] Furthermore, current multiscale modeling approaches lack a universal method for effectively upscaling microscopic interface evolution to the pore network or even reservoir scale. Because microscopic interface dynamics (such as instability mechanisms like snap-off, burst, and overlap) are influenced by multiple factors, including pore geometry, wettability, and the ratio of flow rate to viscosity, upscaling modeling must simultaneously capture key physical mechanisms while maintaining high computational efficiency.

[0006] Therefore, there is an urgent need to develop a method and model framework that can efficiently predict the imbibition behavior of the microscopic two-phase interface, accurately describe the competitive relationship between the main interface and the wetting film, and realize upscaling simulation, so as to make up for the shortcomings of existing technologies in the prediction of microscopic flow behavior and multi-scale simulation of porous media, and thus provide theoretical and tool support for improving recovery rate, optimizing injection and production schemes and developing efficient displacement technology. Summary of the Invention

[0007] In response to the above problems, the purpose of the present invention is to provide a method and system for predicting the imbibition behavior of the microscopic two-phase interface of porous media, which makes up for the shortcomings of the existing technology in predicting the microscopic flow behavior of porous media and multi-scale simulation, and thus provides theoretical and tool support for improving recovery rate, optimizing injection and production schemes and developing efficient displacement technology.

[0008] To achieve the above-mentioned objectives, the present invention proposes the following technical solutions: a method for predicting the imbibition behavior of a microscopic two-phase interface in a porous medium, comprising the following steps: obtaining a pore network consisting of pores and throats according to a target porous medium; calculating the flow rate of the two-phase fluid injected at the throat; calculating the fluid flow rate in the main interface displacement mode and the wetting mode displacement mode according to the flow rate of the two-phase fluid injected at the throat; determining the displacement mode of the two-phase fluid interface according to the fluid flow ratio under the two displacement modes; calculating the flow resistance corresponding to the throat according to the displacement mode of the two-phase fluid interface; and updating the motion control equation of the two-phase fluid according to the flow resistance, thereby completing the prediction of the imbibition behavior of the microscopic two-phase interface in the porous medium.

[0009] Furthermore, the fluid flow rate of the main interface displacement mode for:

[0010] in, is the transient capillary number when the two-phase interface flows through the throat; is the cross-sectional area of ​​the throat through which the fluid flows; is the interfacial tension between the two phase fluids; is the wetting phase viscosity.

[0011] Furthermore, the fluid flow rate of the wetting mode displacement mode for:

[0012] Where C is a parameter related to the geometric characteristics of the pore network throat interface, B is the conductivity function of the injected fluid wetting phase in the throat, R is the cross-sectional radius of the two-phase interface flowing through the throat, and t is the flow time of the wetting film front.

[0013] Furthermore, the method for determining the displacement mode of the two-phase fluid interface is as follows: determining the critical capillary number corresponding to each throat according to the properties of the two-phase fluid and the pore network; simulating the imbibition process of the porous medium, and judging in real time the transient capillary number when the two-phase interface flows through a throat; and judging whether the displacement mode of the two-phase fluid interface is the main interface displacement mode or the wetting mode displacement mode according to whether the transient capillary number reaches the critical capillary number.

[0014] Furthermore, the critical capillary number is the transient capillary number when the fluid flow rates in the main interface displacement mode and the wetting mode displacement mode are the same. Its calculation formula is:

[0015] Where C is a parameter related to the geometric characteristics of the pore network throat interface; R is the cross-sectional radius of the throat through which the two-phase interface flows; is the viscosity of the wetting phase; B is the conductivity function of the injected fluid wetting phase in the throat; t is the time for the wetting film front to flow; is the cross-sectional area of ​​the throat through which the fluid flows; is the interfacial tension between the two phase fluids; is dimensionless time.

[0016] Furthermore, the calculation formula of the transient capillary number is:

[0017] in, is the fluid viscosity; is the fluid flow rate; is the cross-sectional area of ​​the throat through which the fluid flows, is the interfacial tension between the two phase fluids.

[0018] Furthermore, a method for judging whether the displacement mode of the two-phase fluid interface is the main interface displacement mode or the wetting mode displacement mode based on whether the transient capillary number reaches the critical capillary number is as follows: when the two-phase fluid flows through the throat and the transient capillary number is less than the critical capillary number, the interface of the two-phase fluid changes from the main interface displacement mode to the wetting mode displacement mode; when the two-phase fluid flows through the throat and the local capillary pressure is greater than the critical capillary pressure, the interface of the two-phase fluid changes from the wetting mode displacement mode to the main interface displacement mode.

[0019] Furthermore, the method for calculating the corresponding flow resistance at the throat is as follows: the main interface displacement mode selects the Hagen-Poiseuille equation to calculate the flow resistance of the two-phase fluid; the wetting mode displacement mode selects the two-phase viscous coupling calculation formula to calculate the flow resistance of the two-phase fluid in the throat.

[0020] Furthermore, the target porous medium is any one or more of a two-dimensional porous medium and a three-dimensional porous medium.

[0021] The present invention also discloses a prediction system for realizing the imbibition behavior of the microscopic two-phase interface of porous media, comprising: a pore network module, used to obtain a pore network composed of pores and throats according to the target porous medium; a flow calculation module, used to calculate the flow rate of the two-phase fluid injected at the throat, and calculate the fluid flow rate under the main interface displacement mode and the wetting mode displacement mode according to the flow rate of the two-phase fluid injected at the throat; a displacement mode determination module, used to determine the displacement mode of the two-phase fluid interface according to the fluid flow ratio under the two displacement modes; a flow resistance calculation module, used to calculate the corresponding flow resistance at the throat according to the displacement mode of the two-phase fluid interface; an output module, used to update the motion control equation of the two-phase fluid according to the flow resistance, thereby completing the prediction of the imbibition behavior of the microscopic two-phase interface of porous media.

[0022] The technical solution of the present invention has at least the following technical effects or advantages: 1. The method of the present invention focuses on the dynamic prediction of the displacement interface induced by the competition of two-phase fluids in the local structure under the influence of microscopic forces. The resulting prediction method can be used as a research method and upscaling application basis for multiphase flow processes in porous media, such as formation energy resource development, fuel cells, and CO2 geological storage.

[0023] 2. This invention establishes a microscopic two-phase interface prediction method based on the coupling mechanism of the wetting film and the main interface imbibition behavior, and clarifies the preferential flow paths and dynamic evolution patterns of different types of interfaces in the displacement process in the pore structure of complex porous media; by introducing the critical capillary number The quantitative demarcation between the wetting film flow and the main interface flow enables the accurate discrimination of the fluid interface type under transient conditions and effectively reflects the physical evolution process of microscale imbibition behavior.

[0024] 3. The present invention constructs a coupling mechanism among microstructure, interface behavior and flow response, and realizes the upscaling mapping process from pore-throat scale to macroscopic seepage field with the help of structural scale information and interface evolution law, providing support for establishing a multi-scale, multi-physical field coupled seepage simulation framework.

[0025] 4. The method proposed in this paper effectively characterizes the evolutionary relationship between the main fluid interface and the wetting film in porous media under complex geometric structures, enabling high-precision prediction of the imbibition behavior of the microscopic two-phase interface and establishing a dynamic conversion mechanism driven by flow state. Based on this, the constructed upscaling computational model not only improves the resolution of seepage simulations but also provides new tools and approaches for the research and development of complex two-phase behavior in porous media such as unconventional oil and gas reservoirs and shale reservoirs. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a schematic diagram of a pore network consisting of pores and throats in one embodiment of the present invention; Figure 2 is a schematic diagram of the microscopic interface behavior of two-phase fluids in one embodiment of the present invention, Figure 2 (a) is the interface distribution diagram of immiscible fluids in a square interface capillary; Figure 2 (b) is the geometric characteristic diagram of the wetting film on the capillary square interface; Figure 2 (c) is a schematic diagram of the process of the wetted film spreading forward from the initial state; Figure 3 This is a simulation effect diagram of the microscopic interface behavior of two-phase fluids in one embodiment of the present invention; Figure 4 This is an experimental effect diagram of the imbibition behavior of porous media in one embodiment of the present invention. Figure 4 (a) is the depth variation coefficient of 1.0, the capillary number is 2.6*10 -4 Experimental effect diagram; Figure 4 (b) is the depth variation coefficient of 1.0 and the capillary number is 2.6*10 -5 Experimental effect diagram; Figure 4 (c) is the depth variation coefficient of 1.0 and the capillary number is 2.6*10 -6 Experimental effect diagram; Figure 4 (d) is the depth variation coefficient of 1.0, and the capillary number is 2.6*10 -7 Experimental effect diagram; Figure 4 (e) is the depth variation coefficient of 2.0, and the capillary number is 2.6*10 -4 Experimental effect diagram; Figure 4 (f) is the depth variation coefficient of 2.0, and the capillary number is 2.6*10 -5 Experimental effect diagram; Figure 4 (g) is the depth variation coefficient of 2.0, and the capillary number is 2.6*10 -6 Experimental effect diagram; Figure 4 (h) is the depth variation coefficient of 2.0, and the capillary number is 2.6*10 -7 Experimental effect diagram; Figure 4 (i) The depth variation coefficient is 3.0 and the capillary number is 2.6*10-4 Experimental effect diagram; Figure 4 (j) is the depth variation coefficient of 3.0 and the capillary number of 2.6*10 -5 Experimental effect diagram; Figure 4 (k) is the depth variation coefficient of 3.0, and the capillary number is 2.6*10 -6 Experimental effect diagram; Figure 4 (l) is the depth variation coefficient of 3.0, the capillary number is 2.6*10 -7 Experimental effect diagram; Figure 5 This is a simulation effect diagram of the porous medium imbibition behavior using a method for predicting microscopic interface behavior without considering the critical capillary number in one embodiment of the present invention. Figure 5 (a) is the depth variation coefficient of 1.0, the capillary number is 2.6*10 -4 Simulation effect diagram; Figure 5 (b) is the depth variation coefficient of 1.0 and the capillary number is 2.6*10 -5 Simulation effect diagram; Figure 5 (c) is the depth variation coefficient of 1.0 and the capillary number is 2.6*10 -6 Simulation effect diagram; Figure 5 (d) is the depth variation coefficient of 1.0, and the capillary number is 2.6*10 -7 Simulation effect diagram; Figure 5 (e) is the depth variation coefficient of 2.0, and the capillary number is 2.6*10 -4 Simulation effect diagram; Figure 5 (f) is the depth variation coefficient of 2.0, and the capillary number is 2.6*10 -5 Simulation effect diagram; Figure 5 (g) is the depth variation coefficient of 2.0, and the capillary number is 2.6*10 -6 Simulation effect diagram; Figure 5 (h) is the depth variation coefficient of 2.0, and the capillary number is 2.6*10 -7 Simulation effect diagram; Figure 5 (i) The depth variation coefficient is 3.0 and the capillary number is 2.6*10 -4 Simulation effect diagram; Figure 5 (j) is the depth variation coefficient of 3.0 and the capillary number of 2.6*10 -5 Simulation effect diagram; Figure 5 (k) is the depth variation coefficient of 3.0, and the capillary number is 2.6*10 -6 Simulation effect diagram; Figure 5 (l) is the depth variation coefficient of 3.0, the capillary number is 2.6*10 -7 Simulation effect diagram; Figure 6This is a simulation effect diagram of the porous medium imbibition behavior using a method for predicting microscopic interface behavior by considering the critical capillary number in one embodiment of the present invention; Figure 6 (a) is the depth variation coefficient of 1.0, the capillary number is 2.6*10 -4 Simulation effect diagram; Figure 6 (b) is the depth variation coefficient of 1.0 and the capillary number is 2.6*10 -5 Simulation effect diagram; Figure 6 (c) is the depth variation coefficient of 1.0 and the capillary number is 2.6*10 -6 Simulation effect diagram; Figure 6 (d) is the depth variation coefficient of 1.0, and the capillary number is 2.6*10 -7 Simulation effect diagram; Figure 6 (e) is the depth variation coefficient of 2.0, and the capillary number is 2.6*10 -4 Simulation effect diagram; Figure 6 (f) is the depth variation coefficient of 2.0, and the capillary number is 2.6*10 -5 Simulation effect diagram; Figure 6 (g) is the depth variation coefficient of 2.0, and the capillary number is 2.6*10 -6 Simulation effect diagram; Figure 6 (h) is the depth variation coefficient of 2.0, and the capillary number is 2.6*10 -7 Simulation effect diagram; Figure 6 (i) The depth variation coefficient is 3.0 and the capillary number is 2.6*10 -4 Simulation effect diagram; Figure 6 (j) is the depth variation coefficient of 3.0 and the capillary number of 2.6*10 -5 Simulation effect diagram; Figure 6 (k) is the depth variation coefficient of 3.0, and the capillary number is 2.6*10 -6 Simulation effect diagram; Figure 6 (l) is the depth variation coefficient of 3.0, the capillary number is 2.6*10 -7 Simulation effect diagram; Figure 7 This is a water-gas two-phase spatial distribution diagram obtained by using different research methods for the imbibition behavior of porous media in one embodiment of the present invention. Figure 7 (a) is the depth variation coefficient of 1.0, the capillary number is 2.6*10 -4 Experimental results of immiscible fluids; Figure 7 (b) is the depth variation coefficient of 1.0 and the capillary number is 2.6*10 -4 The simulation results without considering the critical capillary number; Figure 7 (c) is the depth variation coefficient of 1.0 and the capillary number is 2.6*10 -4The effect diagram of simulation results considering critical capillary number; Figure 7 (d) is the depth variation coefficient of 3.0 and the capillary number is 2.6*10 -4 Experimental results of immiscible fluids; Figure 7 (e) is the depth variation coefficient of 3.0 and the capillary number is 2.6*10 -4 The simulation results without considering the critical capillary number; Figure 7 (f) is the depth variation coefficient of 3.0 and the capillary number is 2.6*10 -4 The effect diagram of simulation results considering critical capillary number; Figure 7 (g) is the depth variation coefficient of 1.0, the capillary number is 2.6*10 -4 The somatic efficiency of the wetting fluid changes with time during the imbibition process; Figure 7 (h) is the depth variation coefficient of 3.0, and the capillary number is 2.6*10 -4 A graph showing the change in the somatic efficiency of the wetting fluid over time during the imbibition process. DETAILED DESCRIPTION

[0027] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be described in detail through specific embodiments. However, it should be understood that the specific embodiments are provided only for a better understanding of the present invention and should not be construed as limiting the present invention. In the description of the present invention, it should be understood that the terms used are for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0028] In order to deeply reveal the dynamic competition mechanism between the main interface and the wetting film flow in complex porous media and its influence on the macroscopic seepage behavior, the present invention provides a method and system for predicting the imbibition behavior of the microscopic two-phase interface of porous media. The method can identify the evolution mode of the two-phase interface in the local area based on the pore structure and wettability characteristics, establish a quantitative mapping relationship between the microscopic interface displacement behavior and the pore-scale physical properties, and on this basis realize the spatial prediction of the imbibition behavior and the modeling of the dynamic evolution process. At the same time, this method organically links the microscopic interface evolution process with the macroscopic displacement efficiency by constructing a structure-behavior-response upscaling calculation framework, providing new theoretical tools and technical paths for multi-scale seepage simulation, recovery rate prediction and fluid control strategy optimization. The scheme of the present invention is described in detail below with reference to the accompanying drawings.

[0029] Example 1 This embodiment discloses a method for predicting the imbibition behavior of a microscopic two-phase interface in a porous medium, comprising the following steps: S1 obtains a pore network consisting of pores and throats according to the target porous medium.

[0030] The target porous medium is any one or more of a two-dimensional porous medium and a three-dimensional porous medium. The schematic diagram of the pore network composed of pores and throats in this embodiment is as follows Figure 1 As shown in Figure 2, the porous media structure is simplified and abstracted by extracting the pore network. Each pore throat unit has a predetermined critical capillary number based on local geometric characteristics and fluid properties. A pore throat unit consists of two pores of equal size and a narrow intermediate channel (i.e., the throat). The pore unit has a diameter of 500 microns and a throat width of 250 microns, forming a typical "pore-throat-pore" structure. This structure effectively reflects the geometric characteristics of pore throat connecting units in actual porous media and facilitates observation of the evolutionary transition between the wetting film and the primary interface.

[0031] S2 calculates the flow rate of the two-phase fluid injected at the throat; based on the flow rate of the two-phase fluid injected at the throat, the fluid flow rates in the main interface displacement mode and the wetting mode displacement mode are calculated respectively.

[0032] like Figure 2 As shown, Figure 2 (a) is the interface distribution diagram of immiscible fluids in a square interface capillary, showing the interface distribution diagram of the wetting film; Figure 2 (b) is the geometric characteristic diagram of the wetting film on the capillary square interface; Figure 2 (c) is a schematic diagram of the process of the wet film spreading forward from the initial state. Figure 2 As can be seen from the figure, microscopic two-phase interface imbibition behavior mainly includes two types: fluid wetting film and fluid main interface. Two-phase interface imbibition behavior refers to the distribution of the two-phase interface at the pore throat unit of the porous medium. Main interface behavior means that the injected wetting phase fluid completely occupies the throat, while wetting film behavior means that the injected wetting phase fluid flows through the corners of the pore throat, while the non-wetting phase fluid occupies the middle area of ​​the pore throat cross section.

[0033] Fluid flow rate in main interface displacement mode for:

[0034] in, is the transient capillary number when the two-phase interface flows through the throat; is the cross-sectional area of ​​the throat through which the fluid flows; is the interfacial tension between the two phase fluids; is the wetting phase viscosity.

[0035] Fluid flow rate in wetting mode displacement mode for:

[0036] Among them, C is a parameter related to the geometric characteristics of the pore network throat interface, B is the conductivity function of the injected fluid wetting phase in the throat, R is the cross-sectional radius of the two-phase interface flowing through the throat, and t is the time for the wetting film front to flow. The wetting film flow morphology changes at different times. Assuming the dimensionless time is Dimensionless time is a method of converting time into a pure numerical value by eliminating the influence of time units, which facilitates comparative analysis of different scales or systems. In this embodiment, the system is a water-gas two-phase system, and the value corresponding to dimensionless time can be determined to be 1000 through experiments.

[0037] S3 determines the displacement mode of the two-phase fluid interface according to the fluid flow ratio under the two displacement modes.

[0038] The method for determining the displacement mode of the two-phase fluid interface is: S3.1 Determine the critical capillary number for each throat based on the two-phase fluid properties and pore network.

[0039] Based on the pore network, the critical capillary number corresponding to each pore throat unit is determined according to the properties of the injected two-phase fluid and the local structural characteristics of the pore network. A critical capillary number is proposed based on the dynamic balance between the fluid wetting film flow rate and the main interface imbibition flow rate. , in order to determine the priority of the fluid wetting film and the fluid main interface during the next moment of two-phase fluid imbibition. Critical capillary number is the transient capillary number when the fluid flow rates in the main interface displacement mode and the wetting mode displacement mode are the same. Its calculation formula is:

[0040] Where C is a parameter related to the geometric characteristics of the pore network throat interface; R is the cross-sectional radius of the throat through which the two-phase interface flows; is the viscosity of the wetting phase; B is the conductivity function of the injected fluid wetting phase in the throat; t is the time for the wetting film front to flow; is the cross-sectional area of ​​the throat through which the fluid flows; is the interfacial tension between the two phase fluids; is dimensionless time.

[0041] S3.2 simulates the imbibition process of porous media and determines in real time the transient capillary number when the two-phase interface flows through a throat.

[0042] The calculation formula of transient capillary number is:

[0043] in, is the fluid viscosity; is the fluid flow rate; is the cross-sectional area of ​​the throat through which the fluid flows, is the interfacial tension between the two phase fluids.

[0044] S3.3 Determine whether the displacement mode of the two-phase fluid interface is the main interface displacement mode or the wetting mode displacement mode based on whether the transient capillary number reaches the critical capillary number.

[0045] The method of judging whether the displacement mode of the two-phase fluid interface is the main interface displacement mode or the wetting mode displacement mode according to whether the transient capillary number reaches the critical capillary number is as follows: when the two-phase fluid flows through the throat, and the transient capillary number is less than the critical capillary number, that is, , the interface of the two-phase fluid changes from the main interface displacement mode to the wetting mode displacement mode; when the two-phase fluid flows through the throat, when the local capillary pressure is greater than the critical capillary pressure, the interface of the two-phase fluid changes from the wetting mode displacement mode to the main interface displacement mode.

[0046] S4 calculates the flow resistance at the throat based on the displacement pattern of the two-phase fluid interface.

[0047] The method for calculating the flow resistance at the throat is as follows: the Hagen-Poiseuille equation is used in the main interface displacement mode to calculate the flow resistance of the two-phase fluid; the two-phase viscous coupling calculation formula is used in the wetting mode displacement mode to calculate the flow resistance of the two-phase fluid in the throat. The Hagen-Poiseuille equation and the two-phase viscous coupling model are used to calculate the resistance and update the velocity according to the flow mechanism corresponding to different interface morphologies, ensuring the dynamic consistency and physical rationality of the interface behavior prediction, and further driving the dynamic evolution of the two-phase fluid in the global network.

[0048] S5 updates the motion control equations of the two-phase fluid based on the flow resistance, thereby completing the prediction of the imbibition behavior of the microscopic two-phase interface of the porous medium.

[0049] During the simulation, five sets of fluid viscosity ratios were set ( ), respectively 0.01, 0.1, 1, 10 and 100; corresponding to the setting of five groups of capillary numbers ( ), respectively 、 、 、 and ,in, is the wetted phase viscosity, is the injection speed, The simulation adopts a two-phase system with water as the wetting phase and gas as the non-wetting phase, and uses a dynamic network simulation numerical method to track the competitive evolution behavior of the main interface and the wetting film in the pore throat unit.

[0050] The simulation effect diagram of the microscopic interface behavior of two-phase fluid is as follows Figure 3 As shown in the figure, the experimental effect of porous media imbibition behavior is shown in Figure 4 As shown, Figure 4 The horizontal axis is the depth variation coefficient of different structures. The plane of all structures Figure 1 There are differences in the depth direction. When the depth variation coefficient is 1, the depth of all pore structures is 40 microns. When the depth variation coefficient is 2, the corresponding depth of pores with a diameter less than 40 microns is still 40 microns, and the corresponding depth of pores larger than 40 microns is 80 microns. When the depth variation coefficient is 3, the pore structure expands the depth of pores with a diameter larger than 80 to 120 microns based on the depth variation coefficient of 2. Each vertical column of the graph corresponds to its depth variation coefficient. Figure 3 、 Figure 4 As shown, under different combinations of conditions, the microscopic interface morphology exhibits clear demarcation characteristics: when the local transient capillary number is less than the critical capillary number, the imbibition process manifests as preferential growth of the wetting film, with remote wetting achieved through corner flow. However, when the local capillary number exceeds the critical capillary number, displacement behavior is dominated by the main interface, and the wetting film cannot effectively migrate. This transition pattern of interfacial behavior is highly consistent with the theoretical prediction of the critical capillary number proposed in this example.

[0051] This example verifies the applicability of the critical capillary number criterion from the most basic pore-throat connection unit, confirming that the theory can accurately describe the evolution boundary between the wetting film and the main interface under various viscosity ratio and capillary number combinations, providing a reliable microscopic criterion basis for the prediction of two-phase flow in complex porous media systems.

[0052] Example 2 Based on the same inventive concept, this embodiment discloses a method for predicting the imbibition behavior of a microscopic two-phase interface in a porous medium. The porous medium model in this embodiment utilizes a two-dimensional pore structure generated using an image reconstruction algorithm from a three-dimensional CT scan of a sandstone core. This ensures that the resulting two-dimensional planar pore structure is highly consistent with the pore size distribution characteristics of the original three-dimensional digital core. The two-dimensional pore structure has an average pore diameter of approximately 100 microns, a maximum pore diameter of approximately 240 microns, and a depth-wise thickness of 40 microns.

[0053] To systematically analyze the effects of varying depth distributions in two-dimensional structures on the imbibition behavior of the two-phase interface and the accuracy of upscaling simulations, this embodiment designed and fabricated three sets of microfluidic chip models with varying depth configurations: the first set of models was an isobath structure model, meaning all pore units had a depth of 40 microns; the second set of models was a single-depth extension model, in which pores larger than 40 microns were subjected to secondary micromachining based on the first set of models, extending their depth to 80 microns; and the third set of models was a secondary depth extension model, in which pores larger than 80 microns were further micromachined to a depth of 120 microns based on the second set of models. These three sets of models were used to investigate the effects of non-uniform depth distribution on the displacement path selection of the wetting film and the main interface, as well as the overall imbibition behavior.

[0054] This example conducts three types of comparative experiments and simulations in three groups of microfluidic models: (1) Upscaling numerical simulation without considering the critical capillary number mechanism and microscopic interface prediction method proposed in this application, such as Figure 5 As shown; (2) Consider the upscaling numerical simulation of the method of this application, as shown Figure 6 (3) Two-dimensional microscopic imbibition experiment under the same conditions. Each type of comparative test set up 4 groups of different injection speeds to cover different levels of capillary numbers, namely 、 、 and Each set of tests corresponds to 12 water vapor distribution states (3 models × 4 capillary numbers).

[0055] like Figure 7 As shown, Figure 7 (a) is the depth variation coefficient of 1.0, the capillary number is 2.6*10 -4 Experimental results of immiscible fluids; Figure 7 (b) is the depth variation coefficient of 1.0 and the capillary number is 2.6*10 -4 The simulation results without considering the critical capillary number; Figure 7 (c) is the depth variation coefficient of 1.0 and the capillary number is 2.6*10 -4 The effect diagram of simulation results considering critical capillary number; Figure 7 (d) is the depth variation coefficient of 3.0 and the capillary number is 2.6*10 -4 Experimental results of immiscible fluids; Figure 7 (e) is the depth variation coefficient of 3.0 and the capillary number is 2.6*10 -4 The simulation results without considering the critical capillary number; Figure 7 (f) is the depth variation coefficient of 3.0 and the capillary number is 2.6*10 -4 The effect diagram of simulation results considering critical capillary number; Figure 7 (g) is the depth variation coefficient of 1.0, the capillary number is 2.6*10 -4 The somatic efficiency of the wetting fluid changes with time during the imbibition process; Figure 7 (h) is the depth variation coefficient of 3.0, and the capillary number is 2.6*10 -4 The displacement efficiency of the wetting fluid changes with time during the imbibition process. The displacement efficiency is defined as the ratio of the volume of water in the porous medium to the volume of the entire pore space. Figure 7 (g) and Figure 7 The horizontal axis in (f) is dimensionless time, defined as the ratio of the real time t to the time t* when the water reaches the outlet.

[0056] All tests employed a water-gas two-phase system, with water as the wetting phase. By comparing the water-gas distribution images and interface morphology evolution in three types of experimental / simulation results, we found that the upscaling model, which incorporates the critical capillary number criterion and the microscopic interface evolution prediction mechanism of our invention, achieves highly consistent water-gas distribution with microscopic imbibition experiments, accurately predicting microscopic behaviors such as wetting film migration, main interface front advancement, and interface transitions. Meanwhile, conventional upscaling simulations exhibit significant deviations at high capillary numbers, failing to reflect the evolutionary characteristics of wetting film advancement and severing behavior at the pore-throat scale.

[0057] Example 3 Based on the same inventive concept, this embodiment discloses a system for predicting the imbibition behavior of a microscopic two-phase interface in a porous medium, comprising: The pore network module is used to obtain the pore network consisting of pores and throats according to the target porous medium; A flow calculation module is used to calculate the flow rate of the two-phase fluid injected at the throat, and calculate the fluid flow rate in the main interface displacement mode and the wetting mode displacement mode according to the flow rate of the two-phase fluid injected at the throat; A displacement mode determination module, for determining a displacement mode of a two-phase fluid interface according to a fluid flow ratio under two displacement modes; The flow resistance calculation module is used to calculate the corresponding flow resistance at the throat according to the displacement mode of the two-phase fluid interface; The output module is used to update the motion control equations of the two-phase fluid according to the flow resistance, thereby completing the prediction of the microscopic two-phase interface imbibition behavior of the porous medium.

[0058] The present invention constructs a microscopic two-phase interface prediction method based on the coupling mechanism of the wetting film and the main interface imbibition behavior, clarifies the preferential flow paths and dynamic evolution patterns of different types of interfaces in the pore throat structure of complex porous media during the displacement process, and introduces the critical capillary number to predict the flow path of the interface. The quantitative demarcation between the wetting film flow and the main interface flow enables the accurate discrimination of the fluid interface type under transient conditions and effectively reflects the physical evolution process of microscale imbibition behavior.

[0059] This method effectively characterizes the evolutionary relationship between the primary fluid interface and the wetting film in porous media under complex geometric structures, enabling high-precision prediction of the imbibition behavior of microscopic two-phase interfaces and establishing a dynamic conversion mechanism driven by flow state. Based on this, the constructed upscaling computational model not only improves the resolution of seepage simulations but also provides new tools and approaches for the research and development of complex two-phase behaviors in porous media such as unconventional oil and gas reservoirs and shale reservoirs.

[0060] Embodiments of the present invention may be provided as methods, systems, or computer program products. Thus, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0061] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowcharts and / or block diagrams, as well as combinations of processes and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowcharts and / or block diagrams. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0062] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0063] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 The steps for the function specified in one or more boxes.

[0064] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the specific embodiments of the present invention can still be modified or replaced by equivalents, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention should be included within the scope of protection of the claims of the present invention. The above contents are only specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art who is familiar with the technical field can easily think of changes or replacements within the technical scope disclosed by the present invention, which should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for predicting the imbibition behavior of a microscopic two-phase interface in a porous medium, characterized in that: The following steps are involved: According to the target porous medium, a pore network consisting of pores and throats is obtained; Calculating the flow rate of the two-phase fluid injected into the throat; Calculating the fluid flow rates in the main interface displacement mode and the wetting mode displacement mode respectively according to the flow rates of the two-phase fluid injected into the throat; Determine the displacement mode of the two-phase fluid interface based on the fluid flow ratio under the two displacement modes; Calculating the flow resistance corresponding to the throat according to the displacement mode of the two-phase fluid interface; According to the flow resistance, the motion control equation of the two-phase fluid is updated, thereby completing the prediction of the imbibition behavior of the microscopic two-phase interface of the porous medium.

2. The method for predicting the imbibition behavior of a porous medium microscopic two-phase interface according to claim 1, wherein: Fluid flow rate of the main interface displacement mode for: in, is the transient capillary number when the two-phase interface flows through the throat; is the cross-sectional area of ​​the throat through which the fluid flows; is the interfacial tension between the two phase fluids; is the wetting phase viscosity.

3. The method for predicting the imbibition behavior of a porous medium microscopic two-phase interface according to claim 1, wherein: The fluid flow rate of the wetting mode displacement mode for: Where C is a parameter related to the geometric characteristics of the pore network throat interface, B is the conductivity function of the injected fluid wetting phase in the throat, R is the cross-sectional radius of the two-phase interface flowing through the throat, and t is the flow time of the wetting film front.

4. The method for predicting the imbibition behavior of a porous medium microscopic two-phase interface according to claim 1, wherein: The method for determining the displacement mode of the two-phase fluid interface is: Determining the critical capillary number corresponding to each throat according to the two-phase fluid properties and the pore network; Simulate the imbibition process of porous media and determine the transient capillary number when the two-phase interface flows through a throat in real time; Whether the displacement mode of the two-phase fluid interface is the main interface displacement mode or the wetting mode displacement mode is determined according to whether the transient capillary number reaches the critical capillary number.

5. The method for predicting the imbibition behavior of a porous medium microscopic two-phase interface according to claim 4, wherein: The critical capillary number is the transient capillary number when the fluid flow rates in the main interface displacement mode and the wetting mode displacement mode are the same. Its calculation formula is: Where C is a parameter related to the geometric characteristics of the pore network throat interface; R is the cross-sectional radius of the throat through which the two-phase interface flows; is the viscosity of the wetting phase; B is the conductivity function of the injected fluid wetting phase in the throat; t is the time for the wetting film front to flow; is the cross-sectional area of ​​the throat through which the fluid flows; is the interfacial tension between the two phase fluids; is dimensionless time.

6. The method for predicting the imbibition behavior of a porous medium microscopic two-phase interface according to claim 4, wherein: The calculation formula of the transient capillary number is: in, is the fluid viscosity; is the fluid flow rate; is the cross-sectional area of ​​the throat through which the fluid flows, is the interfacial tension between the two phase fluids.

7. The method for predicting the imbibition behavior of a porous medium microscopic two-phase interface according to claim 4, wherein: The method for judging whether the displacement mode of the two-phase fluid interface is the main interface displacement mode or the wetting mode displacement mode according to whether the transient capillary number reaches the critical capillary number is: When the two-phase fluid flows through the throat and the transient capillary number is less than the critical capillary number, the interface of the two-phase fluid changes from the main interface displacement mode to the wetting mode displacement mode; When the two-phase fluid flows through the throat, when the local capillary pressure is greater than the critical capillary pressure, the interface of the two-phase fluid changes from the wetting mode displacement mode to the main interface displacement mode.

8. The method for predicting the imbibition behavior of a porous medium microscopic two-phase interface according to claim 1, wherein: The method for calculating the flow resistance corresponding to the throat is as follows: the main interface displacement mode selects the Hagen-Poiseuille equation to calculate the flow resistance of the two-phase fluid; the wetting mode displacement mode selects the two-phase viscous coupling calculation formula to calculate the flow resistance of the two-phase fluid in the throat.

9. The method for predicting the imbibition behavior of a porous medium microscopic two-phase interface according to claim 1, wherein: The target porous medium is any one or more of a two-dimensional porous medium and a three-dimensional porous medium.

10. A system for predicting the imbibition behavior of a microscopic two-phase interface in porous media, characterized in that: include: The pore network module is used to obtain the pore network consisting of pores and throats according to the target porous medium; a flow calculation module, configured to calculate the flow rate of the two-phase fluid injected into the throat, and to calculate the fluid flow rates in the main interface displacement mode and the wetting mode displacement mode respectively according to the flow rate of the two-phase fluid injected into the throat; A displacement mode determination module, for determining a displacement mode of a two-phase fluid interface according to a fluid flow ratio under two displacement modes; A flow resistance calculation module, configured to calculate the flow resistance corresponding to the throat according to the displacement mode of the two-phase fluid interface; The output module is used to update the motion control equation of the two-phase fluid according to the flow resistance, thereby completing the prediction of the microscopic two-phase interface imbibition behavior of the porous medium.

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