Method for identifying water bridge in pore

Abstract

The invention provides a method for identifying a water bridge in pores, and the method comprises the steps: constructing a micro-pore model according to the structure information of micro-pores, the micro-pore model comprises a plurality of micro-pores, and the micro-pores refer to pores formed by arranging a first medium surface and a second medium surface which are opposite to each other; placing crude oil molecules and water molecules in the micro-pore model, and performing structural relaxation to obtain a mixed system model after structural relaxation; performing molecular dynamics simulation on the mixed system model to obtain a static model in a stable state; creating a Van der Waals surface for water molecules of the static model; and determining whether the micro-pore model forms a water bridge or not according to the continuity of the Van der Waals surface.

Description

Technical Field

[0001] The present application relates to the technical field of microscopic pore simulation, and in particular to a method for identifying water bridges in pores. Background Art

[0002] Molecular dynamics simulation technology is widely used in the characterization of microscopic fluid storage and flow characteristics due to its obvious advantages such as intuitiveness, fine scale, and cost savings. Model building is the first step in molecular dynamics simulation. In the existing technology, the same solid material is generally selected as the medium at both ends of the pore as the storage characteristics of the fluid. The molecular dynamics simulation performed in this way cannot fully and truly reflect the actual underground situation.

[0003] Water bridges refer to the hydrogen bond network formed by water molecules at the microscopic scale, which connects the water molecules between oil and rock pores. Water bridges play an important role in the storage and flow of porous fluids. The existence of water bridges will affect the distribution of fluids at different positions in the pores. For example, the existence of water bridges will cause a large number of water molecules to gather on the surface of the fluid adsorption layer, thereby affecting the flow characteristics of the fluid. Therefore, it is necessary to identify whether there are water bridges in the pores, and by identifying water bridges, an influencing feature can be provided for studying the flow mode of the fluid. Summary of the invention

[0004] In view of this, the purpose of the present application is to provide at least a method for identifying water bridges in pores, by constructing a microscopic pore model including multiple microscopic pores, and filling crude oil molecules and water molecules in multiple microscopic pores, and obtaining a static model corresponding to the microscopic pore model in a stable state by sequentially performing structural relaxation and molecular dynamics simulation, and creating a van der Waals surface of water molecules under the static model, and determining the water bridge formation in the microscopic pore model by identifying the continuity of the van der Waals surface in multiple microscopic pores, thereby solving the technical problem in the prior art that it is impossible to determine whether a water bridge is formed in the pores and thus affecting fluid analysis, and achieving the technical effect of increasing the feature recognition capability for fluid analysis.

[0005] This application mainly includes:

[0006] An embodiment of the present application provides a method for identifying water bridges in pores, the method comprising: constructing a microscopic pore model based on structural information of the microscopic pores, the microscopic pore model comprising a plurality of microscopic pores, the microscopic pores referring to pores formed by setting a first medium surface and a second medium surface relative to each other; placing crude oil molecules and water molecules in the microscopic pore model, and performing structural relaxation to obtain a mixed system model after structural relaxation; performing molecular dynamics simulation on the mixed system model to obtain a static model in a stable state; creating a van der Waals surface of water molecules for the static model; and determining whether the microscopic pore model forms a water bridge based on the continuity of the van der Waals surface.

[0007] Optionally, the structural information of the microscopic pores includes boundary conditions, size levels, and material types corresponding to the first medium surface and the second medium surface, respectively, of the microscopic pores, wherein the material types include minerals or kerogen, and the boundary conditions are used to control the number of microscopic pores in the microscopic pore model.

[0008] Optionally, the structural information also includes the material molecular layer structure of the mineral and the length and width corresponding to the material molecular layer structure.

[0009] Optionally, structural relaxation is performed in the following manner: geometric optimization of the microscopic pore model is performed in sequence, and annealing treatment and molecular dynamics simulation are performed under a canonical ensemble to optimize the intermolecular structure in the microscopic pores.

[0010] Optionally, the molecular dynamics simulation of the mixed system model is performed to obtain a static model in a stable state, including: performing molecular dynamics simulation of the mixed system model under an isothermal and isobaric ensemble, and obtaining a trajectory model corresponding to the simulation process, and taking the last frame of the trajectory model as the static model.

[0011] Optionally, the creating of the van der Waals surface for the water molecules in the static model includes: removing the crude oil molecules, the first medium surface and the second medium surface in the static model, and retaining only the water molecules in the static model; creating a Connery surface for the water molecules in the static model, and configuring lattice parameters and Connery radius to obtain the van der Waals surface of the water molecules.

[0012] Optionally, before determining whether the microscopic pore model forms a water bridge according to the continuity of the van der Waals surface, the method further includes: restoring the first medium surface and the second medium surface in the static model.

[0013] Optionally, determining whether the microscopic pore model forms a water bridge based on the continuity of the van der Waals surface includes: if there is at least one microscopic pore in which the first medium surface and the second medium surface are connected through the van der Waals surface, then a water bridge exists in the microscopic pore model; if the first medium surface and the second medium surface of each microscopic pore are not connected through the van der Waals surface, then no water bridge exists in the microscopic pore model.

[0014] Optionally, before randomly distributing the crude oil molecules and the water molecules into the multiple microscopic pores of the microscopic pore model, the method further includes: constructing a molecular model of the crude oil molecules and a molecular model of the water molecules, wherein the crude oil molecules include single hydrocarbon molecules or mixed hydrocarbon molecules, and the water molecules include pure water or formation water.

[0015] Optionally, the mixed system model after structural relaxation is obtained in the following manner: crude oil molecules and water molecules of a preset mass ratio are randomly placed in the microscopic pore model by random placement order, and the mixed system model is obtained by structural relaxation of the placed microscopic pore model; or, a first molecule is randomly placed in the microscopic pore model by a preset placement order, and the microscopic pore model after the placement of the first molecule is structurally relaxed, when part of the first molecule is adsorbed on the surface of the first medium surface and / or the second medium surface, a second molecule is randomly placed in the microscopic pore model and the mixed system model is obtained by structural relaxation, wherein the preset placement order is used to improve the simulation ability of the mixed system model for the distribution of crude oil molecules and water molecules in an actual geological environment, the first molecule is one of the crude oil molecule and the water molecule, the second molecule is the other of the crude oil molecule and the water molecule, and the first molecule and the second molecule meet the preset mass ratio.

[0016] An embodiment of the present application provides a method for identifying water bridges in pores, the method comprising: constructing a microscopic pore model based on structural information of the microscopic pores, the microscopic pore model comprising a plurality of microscopic pores, the microscopic pores referring to pores formed by setting a first medium surface and a second medium surface relative to each other; placing crude oil molecules and water molecules in the microscopic pore model, and performing structural relaxation to obtain a mixed system model after structural relaxation; performing molecular dynamics simulation on the mixed system model to obtain a static model in a stable state; creating a van der Waals surface of water molecules for the static model; and determining whether the microscopic pore model forms a water bridge based on the continuity of the van der Waals surface. A microscopic pore model including multiple microscopic pores is constructed, and crude oil molecules and water molecules are filled in the multiple microscopic pores. A static model corresponding to the microscopic pore model in a stable state is obtained by sequentially performing structural relaxation and molecular dynamics simulation, and a van der Waals surface of water molecules under the static model is created. The formation of water bridges in the microscopic pore model is determined by identifying the continuity of the van der Waals surface in multiple microscopic pores. This solves the technical problem in the prior art that it is impossible to determine whether a water bridge is formed in the pores, which affects fluid analysis, and achieves the technical effect of increasing the feature recognition capability for fluid analysis.

[0017] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, preferred embodiments are specifically cited below and described in detail with reference to the attached drawings. 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 flow chart of a method for identifying water bridges in pores provided in an embodiment of the present application is shown.

[0020] Figure 2 A schematic diagram of a microscopic pore provided in an embodiment of the present application is shown. DETAILED DESCRIPTION

[0021] To make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme 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. It should be understood that the drawings in the present application only serve the purpose of explanation and description and are not used to limit the scope of protection of the present application. In addition, it should be understood that the schematic drawings are not drawn in real proportion. The flowchart used in this application shows the operations implemented according to some embodiments of the present application. It should be understood that the operations of the flowchart can be implemented out of sequence, and the steps without logical context can be reversed in order or implemented simultaneously. In addition, those skilled in the art, under the guidance of the content of the present application, can add one or more other operations to the flowchart, or remove one or more operations from the flowchart.

[0022] In addition, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various configurations. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the application claimed for protection, but merely represents the selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present application.

[0023] In the prior art, the media at both ends of the pore are set to the same solid position, and the solid materials on both sides are set to minerals or kerogen. However, under actual geological conditions, the minerals around some pores, such as the pores within mineral grains, may be the same, but there are also many pores, such as intergranular pores, where the minerals around them are different. At this time, if the same solid materials on both sides are still selected to construct the pores, it is difficult to fully reflect the actual underground situation.

[0024] At present, molecular dynamics simulation research on the occurrence and characteristics of fluids at the microscopic scale mainly analyzes the density distribution of fluid molecules in pores, distinguishes their free, absorbed or adsorbed states, and counts their proportions in pores; or characterizes parameters such as the rate of molecular movement under the condition of external forces, reflecting the slip effect of nanoporous fluid flow, etc. In general, there is a lack of research on the connectivity characteristics of fluid distribution in pores, which is one of the important factors affecting the occurrence and flow characteristics of immiscible fluids in rock pores.

[0025] Water bridges play an important role in the storage and flow of pore fluids. The existence of water bridges will affect the distribution of fluids at different positions in the pores. For example, the existence of water bridges will cause water molecules to gather in large numbers on the surface of the fluid adsorption layer, thereby affecting the flow characteristics of the fluid.

[0026] Based on this, the embodiment of the present application provides a method for identifying water bridges in pores, by building a microscopic pore model including multiple microscopic pores, and filling crude oil molecules and water molecules in multiple microscopic pores, by sequentially performing structural relaxation and molecular dynamics simulation to obtain a static model corresponding to the microscopic pore model in a stable state, and creating a van der Waals surface of water molecules under the static model, and determining the formation of water bridges in the microscopic pore model by identifying the continuity of the van der Waals surface in multiple microscopic pores, solving the technical problem in the prior art that it is impossible to determine whether a water bridge is formed in the pore and affect fluid analysis, and achieving the technical effect of increasing the feature recognition capability for fluid analysis, as follows:

[0027] See also Figure 1 , Figure 1 This is a flow chart of a method for identifying water bridges in pores provided in an embodiment of the present application. Figure 1 As shown, the method for identifying water bridges in pores provided in the embodiment of the present application can be implemented by Materials Studio software, and the method includes the following steps:

[0028] S101: Construct a microscopic pore model based on the structural information of the microscopic pores.

[0029] The microscopic pore model includes a plurality of microscopic pores, and the microscopic pores refer to pores formed by setting a first medium surface and a second medium surface opposite to each other.

[0030] That is to say, the space between the relative first medium surface and the second medium surface is used as a microscopic pore, and the relative first medium surface and the second medium surface are placed in parallel, and projected from the first medium surface to the second medium surface. The projection surface of the first medium surface can completely overlap with the second medium surface or the projection surface of the first medium surface can partially overlap with the second medium surface.

[0031] For example, see Figure 2 , Figure 2 A schematic diagram of a microscopic pore provided in an embodiment of the present application. Figure 2 As shown, the microscopic pores can be understood as a hexahedral box, and the edges intersecting one corner of the hexahedral box are the first edge L 1 , the second side L 2 and the third side L 3 , and the first medium surface S 1 The plane where it is located is the same as the second medium surface S 2 The first medium surface is parallel to the plane where the second medium surface is located, and the projection surface obtained by projecting the first medium surface along the vertical direction onto the plane where the second medium surface is located partially overlaps with the second medium surface. The first medium surface and the second medium surface opposite to each other in the hexahedral box serve as the media on both sides of the microscopic pores, and the space between the first medium surface and the second medium surface serves as the microscopic pores. In this way, only the first medium surface and the second medium surface exist in the hexahedral box, and other surfaces are ignored. Moreover, if the projection surface obtained by projecting the first medium surface along the vertical direction onto the plane where the second medium surface is located completely overlaps with the second medium surface, then the hexahedral box corresponding to the microscopic pores is a cuboid.

[0032] The structural information of the microscopic pores includes the boundary conditions, size levels, and material types corresponding to the first medium surface and the second medium surface, wherein the material types include minerals or kerogens, and the boundary conditions are used to control the number of microscopic pores in the microscopic pore model. The structural information also includes the material molecular layer structure of the mineral and the length and width corresponding to the material molecular layer structure.

[0033] Specifically, the boundary condition of the microscopic pore refers to the first side L of the hexahedral box. 1 , the second side L 2 and the third side L 3 Periodic boundary conditions are used in the respective directions to set the number of microscopic pores in the microscopic pore model to be multiple. The size level of the microscopic pores is set to nanometer level to meet the microscopic requirements.

[0034] Among them, the structural information of microscopic pores also includes the unit cell parameters, that is, the first side L corresponding to the hexahedral box 1 , the second side L 2 and the third side L 3 The corresponding lengths respectively.

[0035] Among them, the material type of the microscopic pores is selected according to the material type of the underground in the study area. The material type of the first medium surface and the material type of the second medium surface can be the same or different. The material type includes minerals or kerogen. In other words, the first medium surface is a mineral or kerogen, and the second medium surface is a mineral or kerogen, that is, the material type of the first medium surface and the second medium surface is any one of the following: the material type of the first medium surface and the second medium surface are both minerals, the material type of the first medium surface and the second medium surface are both kerogen, the material type of the first medium surface is a mineral and the material type of the second medium surface is kerogen.

[0036] If the material type is mineral, it is also necessary to set the material molecular layer structure of the mineral and the length and width corresponding to the material molecular layer structure. Among them, the material molecular layer structure of the mineral includes a monomolecular layer structure and a multimolecular layer structure. Then, the material molecular layer structure of the mineral is set to a monomolecular layer structure or a multimolecular layer structure, and the length of the monomolecular layer structure or the multimolecular layer structure is set according to an integer multiple of the length of the mineral unit cell, and the width of the monomolecular layer structure or the multimolecular layer structure is set according to an integer multiple of the width of the mineral unit cell.

[0037] Exemplarily, minerals are selected for the first medium surface and the second medium surface, and illite is specifically selected, and a unit cell is established by cutting the (001) plane to increase structural stability, and the first medium surface and the second medium surface are set to a double-layer structure.

[0038] For example, if the length of a mineral unit cell is A and the width is B, no matter the material molecular layer structure of the mineral is set to a single molecular layer structure or a multi-molecular layer structure, the length of the material molecular layer structure of the mineral needs to be set to n 1 times A, the width of the mineral material molecular layer structure needs to be set to n 2 times B, where n 1 and n 2 All are integers.

[0039] Among them, the kerogen can select the corresponding pre-constructed kerogen molecular structure according to the type and maturity of the kerogen in the actual formation, and the kerogen molecular structure is irregular in shape.

[0040] S102: placing crude oil molecules and water molecules in the microscopic pore model and performing structural relaxation to obtain a mixed system model after structural relaxation.

[0041] Before randomly distributing crude oil molecules and water molecules into a plurality of microscopic pores of the microscopic pore model, the method further comprises: constructing a molecular model of the crude oil molecules and a molecular model of the water molecules, wherein the crude oil molecules include single hydrocarbon molecules or mixed hydrocarbon molecules, and the water molecules include pure water or formation water.

[0042] Among them, the underground crude oil samples in the research area are obtained, and the components of the crude oil samples are separated and analyzed to obtain the relative content of various types of crude oil components and typical hydrocarbon molecules. In this way, the molecular model of the crude oil molecule can select the molecular model of the single hydrocarbon molecule with the highest relative content, or the molecular model of the mixed hydrocarbon molecules can be established according to the proportion of various types of crude oil components and typical hydrocarbon molecules.

[0043] For example, the molecular model of crude oil molecules is selected from saturated hydrocarbons, with a specific molecular formula of C 21 H 44 , so that C 21 H 44 The molecular model of is used as the molecular model of crude oil molecule.

[0044] The molecular model of water molecules can select the molecular model of pure water, or establish the water molecular model of formation water according to the mineralization characteristics of formation water in the study area.

[0045] The mixed system model after structural relaxation is obtained in the following manner: crude oil molecules and water molecules of a preset mass ratio are randomly placed in the microscopic pore model in a random placement order, and the mixed system model is obtained by structurally relaxing the microscopic pore model after placement; or, first molecules are randomly placed in the microscopic pore model in a preset placement order, and the microscopic pore model after the first molecules are placed is structurally relaxed, and when part of the first molecules are adsorbed on the surface of the first medium surface and / or the second medium surface, second molecules are randomly placed in the microscopic pore model and the mixed system model is obtained by structurally relaxing.

[0046] Among them, the preset release sequence is used to improve the simulation ability of the mixed system model for the distribution of crude oil molecules and water molecules in an actual geological environment, the first molecule is one of the crude oil molecule and the water molecule, the second molecule is the other of the crude oil molecule and the water molecule, and the first molecule and the second molecule meet the preset mass ratio.

[0047] That is, the placement of crude oil molecules and water molecules of a preset mass ratio in the microscopic pore model includes a random placement method or a sequential placement method according to a preset placement order. Wherein, the placement positions corresponding to the random placement method and the sequential placement method are all random.

[0048] Furthermore, when placing crude oil molecules and water molecules in a preset order, it is necessary to perform structural relaxation on the microscopic pore model after the first molecule is placed first, and after the first medium surface and / or the second medium surface of the microscopic pore model respectively adsorb a part of the first molecule, the second molecule is placed on the microscopic pore model, and after the second molecule is placed, the microscopic pore model is structurally relaxed to obtain a mixed system model. Furthermore, the first molecule and the second molecule are placed in sequence in order to simulate the distribution of the first molecule and the second molecule in the actual geological environment corresponding to the microscopic pore model, thereby obtaining a mixed system model that is more in line with the actual geological environment. Furthermore, the molecular types corresponding to the first molecule and the second molecule can be set according to the actual geological environment.

[0049] That is, when the first molecule is a crude oil molecule, the second molecule is a water molecule; or, when the first molecule is a water molecule, the second molecule is a crude oil molecule.

[0050] Exemplarily, the preset mass ratio is set to 3:1 between the mass of crude oil molecules and the mass of water molecules, and then the crude oil molecules and water molecules with set masses are randomly placed in the microscopic pore model in a random order.

[0051] The structural relaxation is performed in the following manner: the microscopic pore model is geometrically optimized in sequence and annealed and subjected to molecular dynamics simulation under a canonical ensemble to optimize the intermolecular structure in the microscopic pores.

[0052] That is to say, the microscopic pore model after placing crude oil molecules and water molecules is first geometrically optimized, and then annealing treatment and molecular dynamics simulation are performed under the canonical ensemble to achieve structural relaxation, thereby obtaining a mixed system model with optimized intermolecular structure in the microscopic pores.

[0053] Among them, for geometry optimization, you can choose the Steepest descent algorithm or the Smart algorithm, set the maximum number of iterations of geometry optimization to 50,000, and choose not to optimize the unit cell parameters, so as to perform geometry optimization at least once until the operation result shows normal (Termination status: Normal), indicating that the convergence curve (Convergence, unit log10) changes normally with the optimization step (Optimization Step). When the simulation reaches the convergence state, stop the geometry optimization.

[0054] The annealing process under the canonical ensemble (NVT) includes: setting the annealing cycle to 10, the initial temperature to 300K (Kelvin), the temperature rising to 1000K in each cycle, the total number of steps to 10000, the initial speed to random, the time step to 1fs (femtosecond), and the thermostat Nose.

[0055] Among them, the molecular dynamics simulation under the canonical ensemble includes: setting the force field type according to the material type, setting the temperature to room temperature or formation temperature, setting the initial velocity to random, setting the time step to 1fs, and the total simulation time is set according to the size of the microscopic pore model, with a minimum setting of 1ns (nanosecond), and selecting Nose as the thermostat.

[0056] Furthermore, the structure of each molecule in the micropore model is optimized by performing structural relaxation on the micropore model, so that the structure of the organic molecules in the micropore model is more reasonable, and the intermolecular energy is reduced, thereby stabilizing the molecular structure of the micropore model.

[0057] S103: performing molecular dynamics simulation on the mixed system model to obtain a static model in a stable state.

[0058] The molecular dynamics simulation of the mixed system model is performed to obtain a static model in a stable state, including: performing molecular dynamics simulation on the mixed system model under an isothermal and isobaric ensemble, and obtaining a trajectory model corresponding to the simulation process, and taking the last frame of the trajectory model as the static model.

[0059] That is to say, molecular dynamics simulation was performed again under the isothermal and isobaric ensemble (constant-pressure constant-temperature, NPT), including: the pressure was set to the formation pressure, the temperature was set to the formation temperature, the time step was set to 1 fs, the total simulation time was set according to the size of the microscopic pore model, the minimum was set to 1 ns, the initial velocity was set to random, the constant temperature regulator selected Nose, the constant pressure regulator selected Berendsen, and it was set to output one frame of results every 5000 time steps.

[0060] Exemplarily, the temperature is set to 77 degrees Celsius and the total simulation time is set to 5 ns.

[0061] Furthermore, by performing molecular dynamics simulation in an isothermal and isobaric ensemble, the trajectory of the microscopic pore model in each frame can be obtained, thereby obtaining a trajectory model of the entire process of molecular dynamics simulation in the isothermal and isobaric ensemble, and the trajectory model corresponding to the last frame is used as a static model.

[0062] Exemplarily, the static model is saved as a static format file.

[0063] S104: Creating a van der Waals surface of water molecules for the static model.

[0064] The step of creating the van der Waals surface of the water molecules in the static model comprises: removing the crude oil molecules, the first medium surface and the second medium surface in the static model, and retaining only the water molecules in the static model; creating a Connery surface for the water molecules in the static model, and configuring lattice parameters and Connery radius to obtain the van der Waals surface of the water molecules.

[0065] That is to say, the crude oil molecules except water molecules in the static model and the medium on both sides of the microscopic pores are deleted, so that only the water molecules in the static model are retained, and Connery surfaces are created for the water molecules, the lattice resolution is set to medium and above, the default lattice spacing matches the lattice resolution, the Connery radius is set to 0nm, and the probe is controlled to move along the water molecules in the static model to generate the Connery surface, so that the generated Connery surface is used as the van der Waals surface of the water molecules in the static model.

[0066] S105: Determine whether the microscopic pore model forms a water bridge according to the continuity of the van der Waals surface.

[0067] Before determining whether the microscopic pore model forms a water bridge according to the continuity of the van der Waals surface, the method further includes: restoring the first medium surface and the second medium surface in the static model.

[0068] That is to say, after the first medium surface and the second medium surface in the static model are restored, only the van der Waals surface, the first medium surface and the second medium surface remain in the static model, which is equivalent to removing the crude oil molecules in the static model.

[0069] The determining whether the microscopic pore model forms a water bridge according to the continuity of the van der Waals surface includes: if the first medium surface and the second medium surface of at least one microscopic pore are connected through the van der Waals surface, then the microscopic pore model has a water bridge; if the first medium surface and the second medium surface of each microscopic pore are not connected through the van der Waals surface, then the microscopic pore model does not have a water bridge.

[0070] Furthermore, among the multiple micropores in the micropore model, as long as there is a van der Waals surface in the gap between the first medium surface and the second medium surface of one micropore, and the van der Waals surface connects the first medium surface and the second medium surface, it is considered that the van der Waals surface is a water bridge between the medium surfaces on both sides of the target micropore, and thus, it is considered that there is a water bridge in the micropore model.

[0071] That is to say, in the multiple micropores of the micropore model, several channels surrounded by van der Waals surfaces may be formed in the connected space of any micropore. If there is a channel with both ends connecting the first medium surface and the second medium surface respectively, it is determined that the micropore forms a water bridge; if the two ends of any channel cannot connect the first medium surface and the second medium surface, it is determined that there is no water bridge in the micropore.

[0072] Those skilled in the art can clearly understand that, for the convenience and simplicity of description, the specific working process of the system and device described above can refer to the corresponding process in the aforementioned method embodiment, and will not be repeated here. In the several embodiments provided in the present application, it should be understood that the disclosed system, device and method can be implemented in other ways. The device embodiments described above are merely schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some communication interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0073] 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 solution of this embodiment.

[0074] In addition, each functional unit in each embodiment of the present application 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.

[0075] If the function is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a non-volatile computer-readable storage medium that is executable by a processor. Based on this understanding, the technical solution of the present application, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product, and the computer software product is stored in a storage medium, including a number of instructions to enable a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM), random access memory (RAM), disk or optical disk, etc., various media that can store program codes.

[0076] The above are only specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A method for identifying water bridges in pores, characterized in that: The method comprises: A microscopic pore model is constructed according to the structural information of the microscopic pores, wherein the microscopic pore model includes a plurality of microscopic pores, and the microscopic pores refer to pores formed by setting a first medium surface and a second medium surface opposite to each other; placing crude oil molecules and water molecules in the microscopic pore model and performing structural relaxation to obtain a mixed system model after structural relaxation; Performing molecular dynamics simulation on the mixed system model to obtain a static model in a stable state; creating a van der Waals surface of water molecules for the static model; Whether the microscopic pore model forms a water bridge is determined according to the continuity of the van der Waals surface.

2. The method according to claim 1, characterized in that The structural information of the microscopic pores includes the boundary conditions, size levels, and material types corresponding to the first medium surface and the second medium surface of the microscopic pores. Wherein, the material type includes minerals or kerogen, and the boundary conditions are used to control the number of microscopic pores in the microscopic pore model.

3. The method according to claim 2, characterized in that The structural information also includes the material molecular layer structure of the mineral and the length and width corresponding to the material molecular layer structure.

4. The method according to claim 1, characterized in that: Structural relaxation is performed by: The microscopic pore model is sequentially subjected to geometric optimization, annealing treatment and molecular dynamics simulation under a canonical ensemble to optimize the intermolecular structure in the microscopic pores.

5. The method according to claim 1, characterized in that The molecular dynamics simulation of the mixed system model is performed to obtain a static model in a stable state, comprising: A molecular dynamics simulation is performed on the mixed system model under an isothermal and isobaric ensemble, and a trajectory model corresponding to the simulation process is obtained, and the last frame of the trajectory model is used as the static model.

6. The method according to claim 1, characterized in that The step of creating a van der Waals surface of water molecules for the static model comprises: removing the crude oil molecules, the first medium surface and the second medium surface in the static model, and retaining only the water molecules in the static model; A Connery surface is created for the water molecule of the static model, and lattice parameters and Connery radius are configured to obtain the van der Waals surface of the water molecule.

7. The method according to claim 6, characterized in that Before determining whether the microscopic pore model forms a water bridge according to the continuity of the van der Waals surface, the method further includes: The first medium surface and the second medium surface in the static model are restored.

8. The method according to claim 7, characterized in that The step of determining whether the microscopic pore model forms a water bridge according to the continuity of the van der Waals surface comprises: If the first medium surface having at least one microscopic pore is connected to the second medium surface through the van der Waals surface, a water bridge exists in the microscopic pore model; If the first medium surface and the second medium surface of each microscopic pore are not connected through the van der Waals surface, no water bridge exists in the microscopic pore model.

9. The method according to any one of claims 1 to 8, characterized in that: Before randomly distributing the crude oil molecules and water molecules into the plurality of microscopic pores of the microscopic pore model, the method further comprises: constructing a molecular model of the crude oil molecule and a molecular model of the water molecule, The crude oil molecules include single hydrocarbon molecules or mixed hydrocarbon molecules, and the water molecules include pure water or formation water.

10. The method according to any one of claims 1 to 8, characterized in that: The mixed system model after structural relaxation is obtained by the following method: The mixed system model is obtained by randomly placing crude oil molecules and water molecules of a preset mass ratio in the microscopic pore model in a random order, and performing structural relaxation on the placed microscopic pore model; Alternatively, the first molecule is randomly placed in the microscopic pore model by a preset placement order, and the microscopic pore model after the first molecule is placed is subjected to structural relaxation. When part of the first molecule is adsorbed on the surface of the first medium surface and / or the second medium surface, the second molecule is randomly placed in the microscopic pore model and the mixed system model is obtained by performing structural relaxation. Among them, the preset release sequence is used to improve the simulation ability of the mixed system model for the distribution of crude oil molecules and water molecules in an actual geological environment, the first molecule is one of the crude oil molecule and the water molecule, the second molecule is the other of the crude oil molecule and the water molecule, and the first molecule and the second molecule meet the preset mass ratio.

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