Shale composite aperture medium molecular model construction method and device

Abstract

The invention provides a shale composite aperture medium molecular model construction method and device. The model construction method comprises the following steps: constructing an organic matter matrix molecular model of target shale, and constructing a target shale organic matter block model developed with a corresponding type of aperture structure in combination with the organic pore content, the organic seam content and the organic matter main aperture type of the target shale; constructing an inorganic mineral molecular model of the target shale, and constructing a target shale inorganic substance aperture block model developed with a corresponding type of aperture structure by combining the inorganic pore content, the inorganic seam content and the inorganic substance main aperture type of the target shale; the organic matter block model and the inorganic matter aperture block model are combined, aperture structures corresponding to the main aperture types between the organic matter and the inorganic matter of the target shale are formed at the contact positions of the two models, and then the aperture structures in the models are adjusted by combining the organic hole content, the organic seam content, the inorganic hole content and the inorganic seam content of the target shale. And constructing to obtain the shale composite aperture medium molecular model.

Description

Technical Field

[0001] The invention belongs to the technical field of shale gas development geology, and in particular relates to a method and a device for constructing a molecular model of a shale composite pore medium. Background Art

[0002] Shale gas resources are abundant, and have the characteristics of high calorific value, easy storage and transportation, and green environmental protection. It is one of the most important successor resources to conventional oil and gas resources. Since shale reservoirs have nanoscale pore throat networks, complex rock components, diverse fluid occurrence states and seepage mechanisms, and high temperature and high pressure conditions in the reservoir, experimental research on the behavior of shale reservoir fluids is extremely challenging. Molecular simulation has good adaptability to the description of fluid behavior in nanoscale pores of shale reservoirs. Among them, constructing a representative shale nanopore molecular model is a prerequisite for conducting molecular simulation research on shale reservoir fluid behavior.

[0003] The rock components of shale reservoirs are complex, and the pore structures and surface chemical properties of different rock components are significantly different. The shale nanopore molecular models reported so far mainly include detrital mineral models, clay mineral models, organic matter models, and simplified shale composite models. Among them, the detrital mineral model and clay mineral model have relatively fixed structures due to their crystalline properties; the organic matter model has various types and shows a trend of gradual complexity and realism; the reported shale composite model is a simple merger of organic and inorganic matter, and the pore structure is relatively simple. The current frontier of shale nanopore molecular model research is to construct a dual-medium composite model that combines pore structure and surface chemical heterogeneity.

[0004] In actual shale reservoirs, organic matter is usually dispersed in inorganic matter, and organic matter and inorganic matter coexist in an interlaced manner. Some scholars have tried to construct a shale composite model of organic and inorganic matter. For example, some scholars have constructed a shale composite model of sodium montmorillonite and organic matter by inserting pure organic matter components, including pyridine, heptylamine and quinaldine, into the interlayers of sodium montmorillonite. They mixed montmorillonite and pure organic components, then carried out XRD test analysis, and then used the interlayer distance determined by XRD to constrain the interlayer distance in the molecular model and determine the number of interlayer molecules. Subsequently, these scholars replaced the pure organic matter components with Green River three-dimensional kerogen molecules on the basis of the shale composite model of sodium montmorillonite and organic matter components, and constructed a more complex shale composite model of sodium montmorillonite and kerogen. For example, some scholars have established a shale composite model of organic and inorganic matter by inserting methylnaphthalene components into the interlayer space of montmorillonite, in which the number of organic matter is determined according to the organic matter content data obtained from the experiment, and the slit aperture is determined by fitting the adsorption isotherms of simulation and experiment. For example, some scholars have established a shale composite model of shale organic and inorganic matter by adsorbing kerogen components on the silicon surface. For example, some scholars directly contacted the upper and lower surfaces of the bulk illite model with the bulk amorphous carbon model, and used the reaction force field to simulate annealing of the composite model. During the annealing, amorphous carbon and illite were allowed to generate new chemical bonds at the contact surface, thereby constructing a shale composite model of shale organic matter-inorganic matter composite. For example, some scholars have constructed a shale composite model of sodium montmorillonite-kerogen composite by inserting kerogen molecules into the slits of sodium montmorillonite, and used the virtual particle method to expand the pore size distribution range in the model.

[0005] The shale composite models reported so far are obtained by simply merging organic and inorganic matter. The model size is small, the pore structure is simple, and basically no cracks are included. The pore composition of the model is very different from that of the actual shale, resulting in poor representation of the model for the actual shale. Summary of the invention

[0006] The purpose of the present invention is to provide a technical solution that can realize the construction of a shale composite model that is well representative of actual shale. In order to achieve the above purpose, the present invention provides the following five technical solutions.

[0007] In a first aspect, the present invention provides a method for constructing a molecular model of a shale composite porous medium, the method comprising:

[0008] 1) Construct an inorganic mineral molecular model of the target shale;

[0009] 2) Constructing the molecular model of organic matrix of target shale;

[0010] 3) Obtain the organic pore content, organic fracture content, inorganic pore content and inorganic fracture content of the target shale, as well as the main pore and fracture types of organic matter, the main pore and fracture types of inorganic matter, and the main pore and fracture types between organic matter and inorganic matter;

[0011] 4) Based on the organic matrix molecular model of the target shale, combined with the organic pore content, organic fracture content and main pore and fracture types of the target shale, an organic block model of the target shale with corresponding pore and fracture structures is constructed;

[0012] 5) Based on the inorganic mineral molecular model of the target shale, combined with the inorganic pore content, inorganic fracture content and main pore and fracture types of the target shale, an inorganic pore and fracture block model of the target shale with corresponding pore and fracture structures is constructed;

[0013] 6) Combine the organic block model of the target shale and the inorganic pore and fracture block model of the target shale, and form a pore and fracture structure corresponding to the main pore and fracture types between the organic and inorganic matter of the target shale at the contact position between the organic block model of the target shale and the inorganic pore and fracture block model of the target shale, and then adjust the pore and fracture structure in the model in combination with the organic pore content, organic fracture content, inorganic pore content and inorganic fracture content of the target shale to construct a shale composite pore and fracture medium molecular model.

[0014] In a second aspect, the present invention provides a device for constructing a molecular model of a shale composite porous medium, the device comprising:

[0015] The first model building module: used to build an inorganic mineral molecular model of the target shale;

[0016] The second model building module is used to build an organic matrix molecular model of the target shale;

[0017] Parameter acquisition module: used to obtain the organic pore content, organic fracture content, inorganic pore content and inorganic fracture content of the target shale, as well as the main pore and fracture types of organic matter, the main pore and fracture types of inorganic matter, and the main pore and fracture types between organic matter and inorganic matter;

[0018] The third model building module is used to build an organic block model of the target shale with corresponding pore and fracture structures based on the organic matrix molecular model of the target shale, combined with the organic pore content, organic fracture content and main pore and fracture types of the target shale.

[0019] The fourth model building module is used to build an inorganic pore-fracture block model of the target shale with corresponding pore-fracture structures based on the inorganic mineral molecular model of the target shale, combined with the inorganic pore content, inorganic fracture content and main pore-fracture types of the target shale;

[0020] The fifth model construction module is used to combine the organic block model of the target shale and the inorganic pore and fracture block model of the target shale, and form a pore and fracture structure corresponding to the main pore and fracture types between the organic matter and inorganic matter of the target shale at the contact position between the organic block model of the target shale and the inorganic pore and fracture block model of the target shale, and then adjust the pore and fracture structure in the model in combination with the organic pore content, organic fracture content, inorganic pore content and inorganic fracture content of the target shale to construct a shale composite pore and fracture medium molecular model.

[0021] In a third aspect, the present invention provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the method for constructing a molecular model of a shale composite porous medium provided in the first aspect when executing the computer program.

[0022] In a fourth aspect, the present invention provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the method for constructing a molecular model of a shale composite porous medium provided in the first aspect.

[0023] In a fifth aspect, the present invention provides a computer program product, which includes a computer program, and when the computer program is executed by a processor, it implements the method for constructing a molecular model of a shale composite porous medium provided in the first aspect.

[0024] The technical solution provided by the present invention can realize the construction of a shale composite pore medium molecular model. The constructed shale composite pore medium molecular model includes two types of media, inorganic and organic. The inorganic type, organic chemical structure, pore composition and pore type are consistent with the experimental characterization results and are well representative of actual shale. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art descriptions. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. In the drawings:

[0026] Figure 1 The present invention provides a flowchart of a method for constructing a molecular model of a shale composite pore-fracture medium.

[0027] Figure 2 This is a diagram of a device for constructing a molecular model of a shale composite porous medium provided in an embodiment of the present invention.

[0028] Figure 3This is a diagram of the mineral analysis results of the target shale in Example 1.

[0029] Figure 4 This is the inorganic mineral molecular model diagram of the target shale in Example 1.

[0030] Figure 5 The chemical structural unit of the organic matter of the target shale in Example 1

[0031] Figure 6 This is a diagram of dissolved mineral pores in the organic mass of the target shale in Example 1.

[0032] Figure 7 This is a slit pore diagram between organic matter and inorganic matter in the target shale in Example 1.

[0033] Figure 8 This is the initial molecular model diagram of the organic matter of the target shale in Example 1.

[0034] Fig. 9 This is a molecular model diagram of the organic matrix of the target shale in Example 1.

[0035] Fig.10 This is a pore distribution diagram in the organic matrix molecular model of the target shale in Example 1.

[0036] Fig.11 This is a molecular model diagram of the organic matrix of the target shale after the pore structure is constructed in Example 1.

[0037] Fig.12 This is a molecular model diagram of the organic matrix of the target shale with expanded pore structure in Example 1.

[0038] Fig.13 This is a model diagram of the organic block of the target shale in Example 1.

[0039] Fig.14 This is a unit cell diagram of the inorganic mineral matrix of the target shale in Example 1.

[0040] Fig.15 This is a diagram of the inorganic block model of the target shale in Example 1.

[0041] Fig.16 This is a diagram of the inorganic block model of the target shale after the pore structure is constructed in Example 1.

[0042] Fig.17 This is a diagram of the inorganic pore block model of the target shale in Example 1.

[0043] Fig.18 This is a schematic diagram of the combination of the organic block model of the target shale and the inorganic pore block model of the target shale in Example 1.

[0044] Fig.19 This is a molecular model diagram of the target shale composite pore medium in Example 1. DETAILED DESCRIPTION

[0045] To make the purpose, technical solution and advantages of the embodiments of the present invention more clear, the embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings. Here, the exemplary embodiments of the present invention and their descriptions are used to explain the present invention, but are not intended to limit the present invention.

[0046] In the description of this specification, the terms "include", "including", "have", "contain", etc. are all open terms, which mean including but not limited to. The descriptions with reference to the terms "one embodiment", "a specific embodiment", "some embodiments", "for example", etc. mean that the specific features, structures or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. The order of steps involved in each embodiment is used to schematically illustrate the implementation of the present application, and the order of steps is not limited and can be appropriately adjusted as needed.

[0047] In order to construct a shale composite model that is well representative of actual shale, the embodiments of the present invention propose a shale composite pore and fracture medium molecular model construction method, a shale composite pore and fracture medium molecular model construction device, a computer device, a computer-readable storage medium, and a computer program product.

[0048] Figure 1 A flowchart of a method for constructing a molecular model of a shale composite porous medium provided in an embodiment of the present invention, the method comprising the following steps:

[0049] Step 101, constructing an inorganic mineral molecular model of target shale;

[0050] Step 102, constructing an organic matrix molecular model of the target shale;

[0051] Step 103, obtaining the organic pore content, organic fracture content, inorganic pore content and inorganic fracture content of the target shale, as well as the main pore fracture types of organic matter, the main pore fracture types of inorganic matter, and the main pore fracture types between organic matter and inorganic matter;

[0052] Step 104, based on the organic matrix molecular model of the target shale, combined with the organic pore content, organic fracture content and main pore and fracture types of the target shale, an organic block model of the target shale with corresponding types of pore and fracture structures is constructed;

[0053] Step 105, based on the inorganic mineral molecular model of the target shale, combined with the inorganic pore content, inorganic fracture content and main pore and fracture types of the inorganic matter of the target shale, an inorganic pore and fracture block model of the target shale with corresponding types of pore and fracture structures is constructed;

[0054] Step 106, combining the organic block model of the target shale and the inorganic pore and fracture block model of the target shale, forming a pore and fracture structure corresponding to the main pore and fracture types between the organic and inorganic matter of the target shale at the contact position between the organic block model of the target shale and the inorganic pore and fracture block model of the target shale, and then adjusting the pore and fracture structure in the model in combination with the organic pore content, organic fracture content, inorganic pore content and inorganic fracture content of the target shale, to construct a composite pore and fracture medium molecular model of the target shale.

[0055] Combine the following Figure 1 The method for constructing the molecular model of the shale composite pore-fracture medium shown in the figure is described in detail.

[0056] In the above step 101, the construction of the inorganic mineral molecular model of the target shale is achieved.

[0057] In one embodiment, step 101 may specifically include:

[0058] Step 1011: obtaining representative inorganic clay mineral types of target shale and mineral crystal structure parameters of the inorganic clay minerals of this type;

[0059] Step 1012: Based on the representative inorganic clay mineral type of the target shale and the mineral crystal structure parameters of the inorganic clay mineral of the type, a molecular model corresponding to the inorganic clay mineral of the type is constructed as the inorganic mineral molecular model of the target shale;

[0060] Furthermore, in step 1011, when obtaining the representative inorganic clay mineral type of the target shale, the inorganic clay mineral with the highest content in the target shale can be determined through shale mineral analysis, and the inorganic clay mineral with the highest content is used as the representative inorganic clay mineral of the target shale;

[0061] Further, in step 1012, the molecular model corresponding to the type of inorganic clay mineral can be constructed by, but is not limited to, the existing molecular model construction method in the art, and the molecular model construction method used when constructing the molecular model corresponding to the type of inorganic clay mineral is not limited here. For example, first construct the unit cell of the inorganic clay mineral molecular model; then input the atomic space coordinates to construct the clay layered structure; then, cut along the cleavage plane of the clay mineral and expand to establish a supercell structure; finally, supercell structures are superimposed to form the inorganic clay mineral molecular model.

[0062] In the above step 102, the construction of the organic matrix molecular model of the target shale is achieved.

[0063] In one embodiment, step 102 may specifically include:

[0064] Step 1021: constructing organic matter molecular structural units of target shale;

[0065] Step 1022: constructing an organic matrix molecular model of the target shale based on the organic molecular structural units of the target shale.

[0066] In one embodiment, step 1021 may specifically include:

[0067] Step 10211: obtaining chemical structure parameters of organic matter in target shale;

[0068] Step 10212: constructing the organic matter molecular structure unit of the target shale based on the chemical structure parameters of the organic matter of the target shale;

[0069] Furthermore, the chemical structure parameters of the organic matter of the target shale include but are not limited to chemical structure, atomic composition, carbon skeleton structure parameters, and heteroatom functional groups; further, the chemical structure parameters of the organic matter of the target shale include but are not limited to heteroatom composition, structural parameters (such as condensation degree, fatty branching, degree of substitution, number of heteroatom groups), etc.

[0070] Further, in step 10211, when obtaining the chemical structure parameters of the organic matter in the target shale, the chemical structure parameters of the organic matter in the target shale can be determined by an organic geochemical characterization test; further, the organic geochemical characterization test includes but is not limited to elemental analysis, solid carbon nuclear magnetic resonance spectrum test, and X-ray photoelectron spectroscopy test; for example, the chemical structure of the organic matter in the target shale is characterized by elemental analysis, solid carbon nuclear magnetic resonance spectrum test, and X-ray photoelectron spectroscopy test, the atomic composition of the organic matter in the target shale is determined by elemental analysis, the carbon skeleton structure parameters of the organic matter in the target shale are determined by solid carbon nuclear magnetic resonance spectrum test, and the heteroatom functional groups of the organic matter in the target shale are determined by X-ray photoelectron spectroscopy test;

[0071] Furthermore, in step 10212, constructing the organic molecular structural unit of the target shale may be performed by, but is not limited to, using the existing organic molecular structural unit construction method in the art; further, step 102121 may specifically include:

[0072] The main skeleton of the chemical structure of the organic matter of the target shale is constructed based on the aromatic carbon rate, aromatic ring condensation degree and aromatic ring substitution degree of the organic matter of the target shale, and then the aliphatic carbon and heteroatom groups on the main skeleton are adjusted until the chemical structure parameters of the organic matter of the target shale are consistent with the chemical structure parameters of the organic matter of the target shale, thereby obtaining the organic matter molecular structural units of the target shale.

[0073] In one embodiment, step 1022 may specifically include:

[0074] Step 10221: Based on the organic matter molecular structural unit of the target shale, the molecular structure is optimized by using geometric optimization and molecular dynamics methods to obtain an optimized organic matter molecular structural unit;

[0075] Step 10222: Integrate multiple (more than 2) optimized organic matter molecular structural units in a periodic cubic box to establish an initial molecular model of organic matter in the target shale;

[0076] Step 10223: performing organic matter structure relaxation on the initial molecular model of organic matter of the target shale to obtain a balanced organic matter matrix molecular model as the organic matter matrix molecular model of the target shale;

[0077] Further, in step 10221, the geometric optimization and molecular dynamics methods may be used to optimize the molecular structure, but are not limited to the molecular structure unit geometric optimization and molecular dynamics optimization methods already available in the art, which are not limited here; for example, the geometric optimization method is used to optimize the organic molecular structure unit using the smart algorithm to obtain the organic molecular structure with the local minimum energy; the molecular dynamics method is used to optimize the geometrically optimized molecular structure under the canonical ensemble to obtain the organic molecular structure with the global minimum energy;

[0078] Further, in step 10222, a plurality of optimized organic matter molecular structural units are integrated in the periodic cubic box, and when the initial molecular model of organic matter of the target shale is established, 5-10 optimized organic matter molecular structural units are integrated in the periodic cubic box;

[0079] Furthermore, in step 10223, performing organic matter structure relaxation on the initial molecular model of organic matter in the target shale includes: sequentially performing high temperature relaxation simulation, structure condensation simulation, annealing simulation and structure relaxation simulation on the initial molecular model of organic matter in the target shale.

[0080] In the above step 103, the pore composition (organic pore content, organic fracture content, inorganic pore content and inorganic fracture content) and main pore types (main pore types of organic matter, main pore types of inorganic matter and main pore types between organic and inorganic matter) of the target shale are determined.

[0081] In one embodiment, in step 103, the organic pore content, the organic seam content, the inorganic pore content and the inorganic seam content are characterized by using the organic pore surface ratio percentage, the organic seam surface ratio percentage, the inorganic pore surface ratio percentage and the inorganic seam surface ratio percentage;

[0082] Furthermore, the organic pore face ratio percentage, the organic fracture face ratio percentage, the inorganic pore face ratio percentage and the inorganic fracture face ratio percentage can be determined by the following method: the organic pore face ratio, the organic fracture face ratio, the inorganic pore face ratio and the inorganic fracture face ratio of the target shale are obtained, and then the sum of the organic pore face ratio, the organic fracture face ratio, the inorganic pore face ratio and the inorganic fracture face ratio of the target shale is taken as 100%, and the organic pore face ratio, the organic fracture face ratio, the inorganic pore face ratio and the inorganic fracture face ratio of the target shale are normalized respectively to obtain the organic pore face ratio percentage, the organic fracture face ratio percentage, the inorganic pore face ratio percentage and the inorganic fracture face ratio percentage.

[0083] In one embodiment, step 103 may specifically include:

[0084] The pore composition of the target shale (organic pore content, organic fracture content, inorganic pore content and inorganic fracture content) was determined based on the test results of shale large-field stitching scanning electron microscopy technology (MAPS). The main pore types of the target shale (main pore types of organic matter, main pore types of inorganic matter and main pore types between organic and inorganic matter) were determined based on the scanning electron microscopy results.

[0085] In one embodiment, in step 103, the main types of pores and fractures developed in the organic matter of the target shale, the main types of pores and fractures developed in the inorganic matter, and the main types of pores and fractures developed between the organic matter and the inorganic matter obtained include:

[0086] The main types of pores and fractures developed in organic matter include micropores and ultramicropores; the main types of pores and fractures developed in inorganic matter include slit-like pores and cracks; the main type of pores and fractures developed between organic and inorganic matter is slit-like pores.

[0087] In the above step 104, the construction of the organic block model of the target shale is achieved.

[0088] In one embodiment, step 104 may specifically include:

[0089] Based on the organic pore content, organic fracture content and main pore and fracture types of organic matter in the target shale, the pore and fracture structure of the organic matrix molecular model of the target shale is constructed, and the model is expanded in the X-axis, Y-axis and Z-axis directions to obtain the organic block model of the target shale.

[0090] In the above step 105, the inorganic pore block model of the target shale is constructed.

[0091] In one embodiment, step 105 may specifically include:

[0092] Step 1051: cutting the inorganic mineral molecular model of the target shale to obtain the inorganic mineral matrix unit body of the target shale;

[0093] Step 1052: Based on the inorganic pore content, inorganic fracture content and main pore and fracture types of the target shale, the pore and fracture structure of the inorganic mineral matrix unit body of the target shale is constructed and the model is expanded in the X-axis, Y-axis and Z-axis directions, so as to obtain an inorganic pore and fracture block model of the target shale;

[0094] Furthermore, when the inorganic mineral is a layered structure, step 1051 may specifically include:

[0095] The inorganic mineral molecular model of the target shale is cut along the cleavage plane, and the thickness of the cut is 2 inorganic mineral layered structures to obtain the inorganic mineral matrix unit body of the target shale.

[0096] In one embodiment, in step 104 and step 105, during the process of constructing the pore structure and expanding the model in the X-axis, Y-axis, and Z-axis directions, when the main pore types include only micropores and / or ultramicropores, the pore structure is constructed first and then the model is expanded;

[0097] For example, when the main pore types of the organic matter include only micropores and / or ultramicropores, step 104 may specifically include:

[0098] Step 1041: Based on the main pore types (micropores and / or ultramicropores) of organic matter, construct corresponding pore structures (micropore structures and / or ultramicropore structures) in the organic matrix molecular model of the target shale;

[0099] Step 1042: Based on the organic matrix molecular model of the target shale after the pore structure is constructed, the organic block model of the target shale is obtained by respectively expanding along the X-axis, Y-axis, and Z-axis directions;

[0100] Furthermore, step 1042 may specifically include:

[0101] The organic matrix molecular model of the target shale after constructing the pore structure is expanded by 2 times along the X-axis and Y-axis directions respectively, and then the pore structure corresponding to the main pore types of organic matter is constructed at the exact center of the model obtained after the expansion, and then the obtained model is further expanded along the Z-axis direction or along the X-axis and Z-axis directions or along the Y-axis and Z-axis directions or along the X-axis, Y-axis and Z-axis directions to obtain the organic block model of the target shale.

[0102] In one embodiment, in step 104 and step 105, during the process of constructing the hole and crack structure and expanding the model in the X-axis, Y-axis, and Z-axis directions, when the main hole and crack types include holes and cracks, the model is expanded first and then the hole and crack structure is constructed;

[0103] For example, when the main pore types of the inorganic substance include pores and slits, step 105 may specifically include:

[0104] Step 1051: cutting the inorganic mineral molecular model of the target shale to obtain the inorganic mineral matrix unit body of the target shale;

[0105] Step 1052: adjusting the dimensions of the inorganic mineral matrix unit body of the target shale in the X-axis and Y-axis directions so that their common multiples are equal to the dimensions of the organic block model of the target shale in the X-axis and Y-axis directions; expanding the adjusted inorganic mineral matrix unit body of the target shale along the X-axis, Y-axis and Z-axis directions respectively to obtain the inorganic block model of the target shale; wherein the dimensions of the inorganic block model of the target shale in the X-axis and Y-axis directions are equal to the dimensions of the organic block model of the target shale in the X-axis and Y-axis directions;

[0106] Step 1053: Based on the inorganic pore content, inorganic fracture content and main pore and fracture types of the target shale, a corresponding pore and fracture structure is constructed in the inorganic block model of the target shale, thereby obtaining an inorganic pore and fracture block model of the target shale;

[0107] Furthermore, step 1053 may specifically include:

[0108] Based on the main pore and fracture types of the inorganic matter in the target shale, the corresponding pore and fracture structure is constructed in the inorganic block model of the target shale. Then, based on the inorganic pore content and inorganic fracture content of the target shale, the sizes of the inorganic pores and inorganic fractures in the inorganic block model of the target shale are adjusted to satisfy the content ratio of the inorganic pores and inorganic fractures, thereby obtaining the inorganic pore and fracture block model of the target shale.

[0109] In one embodiment, when a fracture structure exists in the inorganic pore-fracture block model of the target shale, the fracture structure should be able to extend to the surface in contact with the organic block model of the target shale.

[0110] In one embodiment, when a fracture structure exists in the organic block model of the target shale, the fracture structure should be able to extend to the surface in contact with the inorganic pore-fracture block model of the target shale.

[0111] In the above step 106, the construction of the shale composite pore-fracture medium molecular model is achieved.

[0112] In one embodiment, step 106 may specifically include:

[0113] The organic block model of the target shale, the inorganic pore and fracture block model of the target shale, and the inverted organic block model of the target shale are superimposed in the same coordinate axis direction, and a pore and fracture structure corresponding to the main pore and fracture types between the organic and inorganic matter of the target shale is formed at the contact position between the organic block model of the target shale and the inorganic pore and fracture block model of the target shale. Then, the pore and fracture structure in the model is adjusted in combination with the organic pore content, organic fracture content, inorganic pore content, and inorganic fracture content of the target shale, and a composite pore and fracture medium molecular model of the target shale is constructed.

[0114] The present invention also provides a shale composite porous medium molecular model construction device, as described in the following embodiments. Since the principle of the device to solve the problem is similar to the shale composite porous medium molecular model construction method, the implementation of the device can refer to the implementation of the shale composite porous medium molecular model construction method, and the repeated parts will not be repeated.

[0115] Figure 2 A schematic diagram of a shale composite pore medium molecular model construction device provided in an embodiment of the present invention, the device may specifically include:

[0116] The first model building module 201 is used to build an inorganic mineral molecular model of the target shale;

[0117] The second model building module 202 is used to build an organic matrix molecular model of the target shale;

[0118] Parameter acquisition module 203: used to obtain the organic pore content, organic fracture content, inorganic pore content and inorganic fracture content of the target shale, as well as the main pore fracture types of organic matter, the main pore fracture types of inorganic matter and the main pore fracture types between organic matter and inorganic matter;

[0119] The third model building module 204 is used to build an organic block model of the target shale with corresponding pore and fracture structures based on the organic matrix molecular model of the target shale, combined with the organic pore content, organic fracture content and main pore and fracture types of the target shale.

[0120] The fourth model building module 205 is used to build an inorganic pore-fracture block model of the target shale with corresponding pore-fracture structures based on the inorganic mineral molecular model of the target shale, combined with the inorganic pore content, inorganic fracture content and main pore-fracture types of the target shale;

[0121] The fifth model construction module 206 is used to combine the organic block model of the target shale and the inorganic pore and fracture block model of the target shale, and form a pore and fracture structure corresponding to the main pore and fracture types between the organic and inorganic matter of the target shale at the contact position between the organic block model of the target shale and the inorganic pore and fracture block model of the target shale, and then adjust the pore and fracture structure in the model in combination with the organic pore content, organic fracture content, inorganic pore content and inorganic fracture content of the target shale to construct a composite pore and fracture medium molecular model of the target shale.

[0122] In one embodiment, the first model building module 201 may specifically include:

[0123] Inorganic clay mineral parameter acquisition submodule 2011: used to obtain representative inorganic clay mineral types of target shale and mineral crystal structure parameters of this type of inorganic clay mineral;

[0124] The first model building submodule 2012 is used to build a molecular model corresponding to a representative inorganic clay mineral type of the target shale and a mineral crystal structure parameter of the inorganic clay mineral type as an inorganic mineral molecular model of the target shale;

[0125] Furthermore, the representative inorganic clay mineral of the target shale is the inorganic clay mineral with the highest content in the target shale.

[0126] In one embodiment, the second model building module 202 may specifically include:

[0127] Organic matter molecular structure unit construction submodule 2021: used to construct the organic matter molecular structure unit of the target shale;

[0128] The second model building submodule 2022 is used to build an organic matrix molecular model of the target shale based on the organic molecular structural units of the target shale.

[0129] In one embodiment, the organic molecular structure unit construction submodule 221 may specifically include:

[0130] Organic matter parameter acquisition unit 20211: used to obtain chemical structure parameters of organic matter of target shale;

[0131] Organic matter molecular structure unit construction unit 20212: used to construct the organic matter molecular structure unit of the target shale based on the chemical structure parameters of the organic matter of the target shale;

[0132] Further, the chemical structure parameters of the organic matter of the target shale include, but are not limited to, chemical structure, atomic composition, carbon skeleton structure parameters, and heteroatom functional groups; further, the chemical structure parameters of the organic matter of the target shale include, but are not limited to, heteroatom composition, structural parameters (such as condensation degree, aliphatic branching, degree of substitution, number of heteroatom groups), etc.;

[0133] Furthermore, the organic molecular structure unit building unit 20212 is specifically used for:

[0134] The main skeleton of the chemical structure of the organic matter of the target shale is constructed based on the aromatic carbon rate, aromatic ring condensation degree and aromatic ring substitution degree of the organic matter of the target shale, and then the aliphatic carbon and heteroatom groups on the main skeleton are adjusted until the chemical structure parameters of the organic matter of the target shale are consistent with the chemical structure parameters of the organic matter of the target shale, thereby obtaining the organic matter molecular structural units of the target shale.

[0135] In one embodiment, the second model building submodule 2022 may specifically include:

[0136] Organic matter molecular structure unit optimization unit 20221: used for the organic matter molecular structure unit based on the target shale, using geometric optimization and molecular dynamics methods to optimize its molecular structure to obtain the optimized organic matter molecular structure unit;

[0137] Initial molecular model building unit 20222: used to integrate multiple (more than 2) optimized organic matter molecular structure units in a periodic cubic box to establish an initial molecular model of organic matter in the target shale;

[0138] The second model building unit 20223 is used to: perform organic matter structure relaxation on the initial molecular model of organic matter of the target shale to obtain a balanced organic matter matrix molecular model as the organic matter matrix molecular model of the target shale;

[0139] Further, a plurality of optimized organic matter molecular structural units are integrated in the periodic cubic box, and when the initial molecular model of organic matter of the target shale is established, 5 to 10 optimized organic matter molecular structural units are integrated in the periodic cubic box;

[0140] Furthermore, performing organic matter structure relaxation on the initial molecular model of organic matter in the target shale includes: sequentially performing high temperature relaxation simulation, structure condensation simulation, annealing simulation and structure relaxation simulation on the initial molecular model of organic matter in the target shale.

[0141] In one embodiment, the organic pore content, the organic slit content, the inorganic pore content, and the inorganic slit content are characterized using the organic pore surface ratio percentage, the organic slit surface ratio percentage, the inorganic pore surface ratio percentage, and the inorganic slit surface ratio percentage;

[0142] Furthermore, the organic pore face ratio percentage, the organic fracture face ratio percentage, the inorganic pore face ratio percentage and the inorganic fracture face ratio percentage can be determined by the following method: the organic pore face ratio, the organic fracture face ratio, the inorganic pore face ratio and the inorganic fracture face ratio of the target shale are obtained, and then the sum of the organic pore face ratio, the organic fracture face ratio, the inorganic pore face ratio and the inorganic fracture face ratio of the target shale is taken as 100%, and the organic pore face ratio, the organic fracture face ratio, the inorganic pore face ratio and the inorganic fracture face ratio of the target shale are normalized respectively to obtain the organic pore face ratio percentage, the organic fracture face ratio percentage, the inorganic pore face ratio percentage and the inorganic fracture face ratio percentage.

[0143] In one embodiment, the third model building module 204 is specifically used to:

[0144] Based on the organic pore content, organic fracture content and main pore and fracture types of organic matter in the target shale, the pore and fracture structure of the organic matrix molecular model of the target shale is constructed, and the model is expanded in the X-axis, Y-axis and Z-axis directions to obtain the organic block model of the target shale.

[0145] In one embodiment, the fourth model building module 205 may specifically include:

[0146] Inorganic mineral matrix unit body construction submodule 2051: used to cut the inorganic mineral molecular model of the target shale to obtain the inorganic mineral matrix unit body of the target shale;

[0147] The fourth model building submodule 2052 is used to construct the pore structure of the inorganic mineral matrix unit body of the target shale and expand the model in the X-axis, Y-axis and Z-axis directions based on the inorganic pore content, inorganic fracture content and main pore and fracture types of the inorganic matter of the target shale, so as to obtain the inorganic pore and fracture block model of the target shale;

[0148] Furthermore, when the inorganic mineral is a layered structure, the inorganic mineral matrix unit body construction submodule 2051 is specifically used for:

[0149] The inorganic mineral molecular model of the target shale is cut along the cleavage plane, and the thickness of the cut is 2 inorganic mineral layered structures to obtain the inorganic mineral matrix unit body of the target shale.

[0150] In one embodiment, during the process of constructing the pore structure and expanding the model in the X-axis, Y-axis, and Z-axis directions, when the main pore types include only micropores and / or ultramicropores, the pore structure is constructed first and then the model is expanded;

[0151] For example, when the main pore types of organic matter include only micropores and / or ultramicropores, the third model building module 204 may specifically include:

[0152] Organic matter pore structure construction submodule 2041: used to construct corresponding pore structure (micropore structure and / or ultramicropore structure) in the organic matter matrix molecular model of the target shale based on the main pore types (micropores and / or ultramicropores) of organic matter;

[0153] The third model building submodule 2042 is used to expand the organic matrix molecular model of the target shale after the pore structure is built along the X-axis, Y-axis, and Z-axis directions to obtain the organic block model of the target shale;

[0154] Furthermore, the third model building submodule 2042 is specifically used for:

[0155] The organic matrix molecular model of the target shale after constructing the pore structure is expanded by 2 times along the X-axis and Y-axis directions respectively, and then the pore structure corresponding to the main pore types of organic matter is constructed at the exact center of the model obtained after the expansion, and then the obtained model is further expanded along the Z-axis direction or along the X-axis and Z-axis directions or along the Y-axis and Z-axis directions or along the X-axis, Y-axis and Z-axis directions to obtain the organic block model of the target shale.

[0156] In one embodiment, during the process of constructing the hole and seam structure and expanding the model in the X-axis, Y-axis, and Z-axis directions, when the main hole and seam types include holes and seams, the model expansion is performed first and then the hole and seam structure is constructed;

[0157] For example, when the main pore types of the inorganic substance include pores and slits, the fourth model building submodule 2052 may specifically include:

[0158] Inorganic block model construction unit 20521: used to adjust the dimensions of the inorganic mineral matrix unit body of the target shale in the X-axis and Y-axis directions so that their common multiples are equal to the dimensions of the organic block model of the target shale in the X-axis and Y-axis directions; expand the adjusted inorganic mineral matrix unit body of the target shale along the X-axis, Y-axis and Z-axis directions respectively to obtain the inorganic block model of the target shale; wherein the dimensions of the inorganic block model of the target shale in the X-axis and Y-axis directions are equal to the dimensions of the organic block model of the target shale in the X-axis and Y-axis directions;

[0159] The fourth model building unit 20522 is used to build a corresponding pore-fracture structure in the inorganic block model of the target shale based on the inorganic pore content, inorganic fracture content and main pore-fracture types of the inorganic matter of the target shale, thereby obtaining an inorganic pore-fracture block model of the target shale;

[0160] Furthermore, the fourth model building unit 20522 is specifically used for:

[0161] Based on the main pore and fracture types of the inorganic matter in the target shale, the corresponding pore and fracture structure is constructed in the inorganic block model of the target shale. Then, based on the inorganic pore content and inorganic fracture content of the target shale, the sizes of the inorganic pores and inorganic fractures in the inorganic block model of the target shale are adjusted to satisfy the content ratio of the inorganic pores and inorganic fractures, thereby obtaining the inorganic pore and fracture block model of the target shale.

[0162] In one embodiment, when a fracture structure exists in the inorganic pore-fracture block model of the target shale, the fracture structure should be able to extend to the surface in contact with the organic block model of the target shale.

[0163] In one embodiment, when a fracture structure exists in the organic block model of the target shale, the fracture structure should be able to extend to the surface in contact with the inorganic pore-fracture block model of the target shale.

[0164] In one embodiment, the fifth model building module 206 is specifically used to:

[0165] The organic block model of the target shale, the inorganic pore and fracture block model of the target shale, and the inverted organic block model of the target shale are superimposed in the same coordinate axis direction, and a pore and fracture structure corresponding to the main pore and fracture types between the organic and inorganic matter of the target shale is formed at the contact position between the organic block model of the target shale and the inorganic pore and fracture block model of the target shale. Then, the pore and fracture structure in the model is adjusted in combination with the organic pore content, organic fracture content, inorganic pore content, and inorganic fracture content of the target shale, and a composite pore and fracture medium molecular model of the target shale is constructed.

[0166] An embodiment of the present invention further provides a computer device, which includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the above-mentioned method for constructing a molecular model of a shale composite porous medium is implemented.

[0167] An embodiment of the present invention further provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the above-mentioned method for constructing a molecular model of a shale composite porous medium is implemented.

[0168] An embodiment of the present invention further provides a computer program product, which includes a computer program. When the computer program is executed by a processor, the method for constructing a molecular model of a shale composite porous medium is implemented.

[0169] Embodiment 1:

[0170] This embodiment provides a method for constructing a shale composite porous medium molecular model, which constructs a composite porous medium molecular model of shale in area A, specifically including:

[0171] 1. Collect several shale samples from the shale reservoir in Sichuan A area, and analyze the mineral composition of the target shale in combination with X-ray diffraction test (see Figure 3 ). Among them, illite is the most important inorganic clay mineral in the target shale, and it is taken as the representative inorganic clay mineral of the target shale. The most representative Al1Mtv illite type is selected, and its crystal structure parameters are combined to construct the corresponding molecular model as the inorganic mineral molecular model of the target shale (see Figure 4 ).

[0172] 2. Use a pulverizer to process the collected samples and screen and collect shale particles. Use the acid washing method and Soxhlet extraction process to separate and remove minerals and asphaltene from shale particles, extract organic matter samples - kerogen samples and store them after drying under vacuum. Determine the chemical structure parameters of organic matter (kerogen) through elemental analysis, solid carbon nuclear magnetic resonance spectrum test, and X-ray photoelectron spectroscopy test, specifically including characterizing the chemical structure of organic matter (kerogen) through elemental analysis, solid carbon nuclear magnetic resonance spectrum test, and X-ray photoelectron spectroscopy test, obtaining the atomic composition of organic matter (kerogen) by elemental analysis, obtaining the carbon skeleton structure parameters of organic matter (kerogen) by solid carbon nuclear magnetic resonance spectrum analysis, and obtaining the heteroatom functional groups of organic matter (kerogen) by X-ray photoelectron spectroscopy analysis.

[0173] 3. Combine the chemical structure parameters of the obtained organic matter (kerogen) to construct the organic matter molecular structure unit of the target shale. First, the main skeleton of the chemical structure of the organic matter (kerogen) is constructed based on the aromatic carbon rate, aromatic ring condensation degree and aromatic ring substitution degree of the organic matter (kerogen), and then the aliphatic carbon and heteroatom groups on the main skeleton are adjusted until the chemical structure parameters of the obtained organic matter (kerogen) match the chemical structure parameters of the obtained organic matter (kerogen), thereby obtaining the organic matter molecular structure unit of the target shale.

[0174] The final two-dimensional molecular structure of organic matter (kerogen) (C 320 O 19 N7S2) Figure 5Its composition and structural parameters are shown in Tables 1 to 4. The heteroatom composition of the chemical structural unit of organic matter (kerogen) is basically close to the elemental analysis results. The structural parameters of organic matter (kerogen), such as condensation degree, fatty branching, substitution degree, and number of heteroatom groups, are consistent with the experimental analysis results.

[0175] Table 1 Test of heteroatom ratio of organic matter (kerogen)

[0176] Atomic number ratio Model structure Experimental Results Relative error / % O / C 0.0594 0.0549 8.24 N / C 0.0219 0.0226 -3.30 S / C 0.0063 0.0071 -12.31

[0177] Table 2. Carbon skeleton parameter test of organic matter (kerogen)

[0178]

[0179]

[0180] Table 3 Test of oxygen-containing functional groups in organic matter (kerogen)

[0181]

[0182] Table 4. Test of nitrogen and sulfur functional groups in organic matter (kerogen)

[0183]

[0184] 4. Samples collected from three different wells in Area A (Well A, Well B, Well C) were tested by MAPS technology to obtain the organic pore face ratio, organic seam face ratio, inorganic pore face ratio and inorganic seam face ratio (see Table 5). The face ratio of the samples has strong heterogeneity. Taking the sum of the organic pore face ratio, organic seam face ratio, inorganic pore face ratio and inorganic seam face ratio of the samples as 100%, the face ratio data of each sample were normalized to obtain the organic pore face ratio percentage, organic seam face ratio percentage, inorganic pore face ratio percentage and inorganic seam face ratio percentage of each sample (see Table 6). The difference between the face ratio percentages obtained after normalization of each sample is small, and the maximum absolute error between the face ratio percentage results of each sample and the average value is less than 3%. The organic pore face ratio percentage, organic fracture face ratio percentage, inorganic pore face ratio percentage and inorganic fracture face ratio percentage of each sample were averaged, and the average organic pore face ratio percentage, organic fracture face ratio percentage and inorganic pore face ratio percentage were used as the organic pore face ratio, organic fracture face ratio, inorganic pore face ratio and inorganic fracture face ratio of the target shale for normalization to obtain the organic pore face ratio percentage, organic fracture face ratio percentage, inorganic pore face ratio percentage and inorganic fracture face ratio percentage.

[0185] As shown in Table 6, the surface porosity of organic pores in the target shale reaches 79.22%. Organic pores are the main pore type of the target shale. At the same time, there are also many inorganic pores and a certain amount of inorganic fractures. The surface porosity of inorganic pores and inorganic fractures are 14.01% and 4.65% respectively. Compared with organic pores, inorganic pores and inorganic fractures, the content of organic fractures in the target shale is less, and the surface porosity is only 2.12%.

[0186] Table 5 Sample face rate

[0187] Organic pores / % Organic seam / % Inorganic pores / % Inorganic seam / % total / % Sample from Well A 0.1767 0.0027 0.0377 0.0106 0.2278 Sample from Well B 0.5469 0.0039 0.1058 0.0269 0.6835 Sample from Well C 0.6775 0.0308 0.1042 0.0447 0.8573 Mean 0.4670 0.0125 0.0826 0.0274 0.5895

[0188] Table 6 Sample face rate percentage

[0189] Organic pores / % Organic seam / % Inorganic pores / % Inorganic seam / % Sample from Well A 77.57 1.19 16.57 4.67 Sample from Well B 80.01 0.57 15.48 3.94 Sample from Well C 79.03 3.60 12.16 5.22 Mean 79.22 2.12 14.01 4.65 Maximum absolute error -1.65 -1.54 2.56 -0.71

[0190] 5. Combined with the results of scanning electron microscopy of the samples, clarify the main pore types of organic matter, the main pore types of inorganic matter, and the main pore types between organic and inorganic matter. Figure 6 and Figure 7 They are the dissolved mineral pores in the organic matter of the sample and the slit pores between the organic matter and the inorganic matter. There are a large number of organic blocks in the sample, and the organic blocks are rich in micropores and ultramicropores, and the distribution of micropores and ultramicropores is relatively uniform. In addition, there are more soluble inorganic clay minerals interspersed in the organic blocks. The soluble inorganic clay minerals are dissolved by the acidic fluid of the formation to form more slit-shaped dissolved inorganic pores. The slit-shaped dissolved inorganic pores are mostly arranged parallel to each other, and a certain amount of inorganic slits are developed. In addition, slit-shaped pore spaces are developed at the contact position between the organic block and the inorganic matter, which are mainly formed by the contraction of organic matter. In summary, the main types of pores and slits developed in organic matter include micropores and ultramicropores; the main types of pores and slits developed in inorganic matter include slit pores and cracks; the main type of pores and slits developed between organic matter and inorganic matter are slit pores.

[0191] 6. Based on the organic matter molecular structural units of the target shale, the organic matter matrix molecular model of the target shale is constructed. First, the molecular structure of the organic matter molecular structural unit of the target shale is optimized by using geometric optimization and molecular dynamics methods to obtain the optimized organic matter molecular structural unit; then, the five optimized organic matter molecular structural units are integrated in a periodic cubic box to establish the initial molecular model of the organic matter of the target shale (see Figure 8 ); Finally, the organic matter structure relaxation is performed on the initial molecular model of the organic matter of the target shale using the steps in Table 7 to obtain a balanced organic matter matrix molecular model as the organic matter matrix molecular model of the target shale (see Fig. 9 ).

[0192] Table 7 Organic matter structure relaxation steps

[0193] order stage Ensemble Simulation time 1 High temperature relaxation NVT 200ps 2 Structural Cohesion NPT 200ps 3 Annealing simulation NVT 200ps 4 Structural relaxation NPT 200ps

[0194] 7. Based on the organic matrix molecular model of the target shale, combined with the organic pore content, organic fracture content and main pore and fracture types of the target shale, an organic block model of the target shale with corresponding types of pore and fracture structures is constructed.

[0195] The MAPS test results of shale show that organic pores are the main pore type in the target shale. The scanning electron microscope results show that there are a large number of micropores and ultramicropores in the shale organic matter. The main pore types of organic matter include micropores and ultramicropores. In the organic matrix molecular model of the target shale, the pore size is small, mainly ultramicropores with a pore size of less than 0.5nm, which belong to the intermolecular pores inside the organic matter (kerogen) (see Fig.10 In order to increase the pore space in the organic matrix molecular model of the target shale, a spherical micropore was created in the center of the model by deletion (see Fig.11 ). The molecular model of the organic matrix of the target shale is a cubic structure with a side length of To maintain the rationality of the model, the diameter of the micropores created should not be greater than half of the model side length. The diameter of the micropores created in this example is The created micropores are merged with the intermolecular ultramicropores in the molecular model of the organic matrix of the target shale, which significantly increases the pore space in the model. The model is further expanded based on the molecular model of the organic matrix of the target shale after the micropores are created to increase the pore space and model size. First, the molecular model of the organic matrix of the target shale after the micropores are constructed is expanded by 2 times along the X-axis and Y-axis directions, and then a new micropore is created in the center of the expanded model by deletion method. The diameter of the micropore is (See Fig.12 ); and then the obtained model is further expanded by 2 times along the X-axis and Z-axis directions to obtain the organic block model of the target shale (see Fig.13 ). The dimensions of the organic block model of the target shale in the X-axis, Y-axis, and Z-axis directions are

[0196] 8. Based on the inorganic mineral molecular model of the target shale, combined with the inorganic pore content, inorganic fracture content and main pore and fracture types of the target shale, an inorganic pore and fracture block model of the target shale with corresponding types of pore and fracture structures is constructed.

[0197] The MAPS test results of shale show that the target shale contains a large number of inorganic pores and inorganic fractures. The scanning electron microscope results show that there are a large number of parallel slit-like dissolved inorganic pores and inorganic fractures that penetrate the inorganic pores in the organic blocks of the target shale. The main types of pores and fractures developed in inorganic matter include slit-like pores and cracks.

[0198] The inorganic mineral molecular model of the target shale is cut to obtain the inorganic mineral matrix unit body of the target shale. Specifically, the inorganic mineral molecular model of the target shale is cut along the illite 001 cleavage plane, and the thickness of the cut is 2 illite TOT layered structures (see Fig.14 ).

[0199] The X-axis and Y-axis dimensions of the inorganic mineral matrix unit body of the target shale are fine-tuned so that their common multiples are equal to the X-axis and Y-axis dimensions of the organic block model of the target shale; then, the adjusted inorganic mineral matrix unit body of the target shale is expanded along the X-axis, Y-axis, and Z-axis directions respectively to obtain the inorganic block model of the target shale (see Fig.15 The dimensions of the inorganic block model of the target shale in the X-axis and Y-axis directions are equal to the dimensions of the organic block model of the target shale in the X-axis and Y-axis directions (the dimensions of the X-axis and Y-axis directions are and The size of the inorganic block model of the target shale in the Z-axis direction needs to consider the size of the inorganic pores to be created. In this embodiment, it is set to There are no ultra-micropores in the inorganic block model of the target shale that are accessible to methane molecules.

[0200] Based on the main pore and fracture types of the inorganic matter of the target shale, a corresponding pore and fracture structure is constructed in the inorganic block model of the target shale, and then based on the inorganic pore content and inorganic fracture content of the target shale, the size of the inorganic pores and inorganic fractures in the inorganic block model of the target shale is adjusted to satisfy the content ratio of the inorganic pores and inorganic fractures, thereby obtaining the inorganic pore and fracture block model of the target shale. Specifically, it includes: combining the main pore and fracture types of the inorganic matter of the target shale, creating slit-shaped inorganic pores in the inorganic block model of the target shale (see Fig.16 ); To consider the influence of pore size, three inorganic holes of different heights were created in this embodiment, which are The three types of pores are parallel to each other, and the length and width of the pores are the same. Then, inorganic fractures are created. The height direction of the inorganic fractures is parallel to the Z-axis direction. The inorganic fractures penetrate the three inorganic pores of different heights and extend to the surface of the model perpendicular to the Z-axis. The length and width of the inorganic fractures are the same. Based on the inorganic pore content and inorganic fracture content of the target shale, the length and width of the inorganic pores and the length and width of the inorganic fractures in the inorganic block model of the target shale are adjusted to satisfy the content ratio of the inorganic pores and inorganic fractures, thereby obtaining the inorganic pore and fracture block model of the target shale (see Fig.17 ).

[0201] 9. Superimpose the target shale organic block model, the target shale inorganic pore block model, and the inverted target shale organic block model in the Z-axis direction (see Fig.18 ), during the superposition process, the contact surface between the organic block model and the inorganic pore block model is not smooth due to the periodic change of the organic block model in the Z-axis direction, forming organic-inorganic slit pores, and new micropores are formed at the end of the organic block model away from the inorganic pore block model. Then, the size of the organic-inorganic slit pores and inorganic mesopores in the model is adjusted based on the organic pore content, organic slit content, inorganic pore content and inorganic slit content of the target shale, and the molecular model of the composite pore medium of the target shale is constructed (see Fig.19 ).

[0202] The molecular model of the target shale composite porous medium includes two different rock media, organic matter and inorganic matter. Organic matter includes two types of pores, ultra-micropores and micropores, where the size of ultra-micropores is less than 0.5nm and the size of micropores is less than 2nm. Inorganic matter includes both inorganic pores and inorganic slits, where inorganic pores have three different pore heights, corresponding to three different fluid storage mechanisms: micropore filling, pore wall coupling, and macropore monolayer adsorption. Organic matter and inorganic matter are in contact through slit-like pore spaces, which correspond to the slit-like pore spaces developed at the contact position between the organic block and the inorganic matter in the scanning electron microscope (formed by organic matter shrinkage). Inorganic slits penetrate the inorganic pores in the Z-axis direction and are connected to the organic matter. In order to more accurately describe the interaction between different rock media and fluids, the cvff force field and clayFF force field are used to describe the organic and inorganic parts in the molecular model of the target shale composite porous medium.

[0203] In order to verify the representativeness of the obtained target shale composite pore-fracture medium molecular model, the pore-fracture composition of the target shale composite pore-fracture medium molecular model was compared with the MAPS test results, and the comparison results are shown in Table 8. The deviation between the surface ratio percentage of the target shale composite pore-fracture medium molecular model and the experimental test results is small, with an absolute error of less than 3% and a relative error of less than 10%, indicating that the constructed target shale composite pore-fracture medium molecular model with two media and multiple types of pores coexisting is highly representative of the target shale.

[0204] Table 8 Comparison of surface porosity percentage of target shale pore composition

[0205]

[0206] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, 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 disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0207] 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 flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, 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 flowchart and / or block diagram. 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.

[0208] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate 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 A function specified in one or more boxes.

[0209] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process in the computer or other programmable device. Figure 1 A process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0210] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for constructing a molecular model of a shale composite porous medium, the method comprising: 1) Construct an inorganic mineral molecular model of the target shale; 2) Constructing the molecular model of organic matrix of target shale; 3) Obtain the organic pore content, organic fracture content, inorganic pore content and inorganic fracture content of the target shale, as well as the main pore and fracture types of organic matter, the main pore and fracture types of inorganic matter, and the main pore and fracture types between organic matter and inorganic matter; 4) Based on the molecular model of the organic matrix of the target shale, combined with the organic pore content, organic fracture content and main pore and fracture types of the target shale, an organic block model of the target shale with corresponding types of pore and fracture structures is constructed; 5) Based on the inorganic mineral molecular model of the target shale, combined with the inorganic pore content, inorganic fracture content and main pore and fracture types of the target shale, an inorganic pore and fracture block model of the target shale with corresponding pore and fracture structures is constructed; 6) The organic block model of the target shale and the inorganic pore-fracture block model of the target shale are combined to form a pore-fracture structure corresponding to the main pore-fracture types between the organic and inorganic matter of the target shale at the contact position between the organic block model of the target shale and the inorganic pore-fracture block model of the target shale, and then the pore-fracture structure in the model is adjusted in combination with the organic pore content, organic fracture content, inorganic pore content and inorganic fracture content of the target shale to construct a shale composite pore-fracture medium molecular model.

2. The method according to claim 1, wherein: The inorganic mineral molecular model of the target shale is constructed as follows: Obtaining representative inorganic clay mineral types of target shale and mineral crystal structure parameters of this type of inorganic clay minerals; Based on the representative inorganic clay mineral type of the target shale and the mineral crystal structure parameters of the inorganic clay mineral of this type, a molecular model corresponding to the inorganic clay mineral of this type is constructed as the inorganic mineral molecular model of the target shale.

3. The method according to claim 1, wherein: The construction of the organic matrix molecular model of the target shale comprises: Constructing the organic matter molecular structural units of the target shale; Based on the organic matter molecular structural units of the target shale, an organic matter matrix molecular model of the target shale is constructed; Preferably, the organic molecular structural units for constructing the target shale include: Obtain the chemical structure parameters of organic matter in the target shale; Based on the chemical structure parameters of the organic matter of the target shale, the organic matter molecular structure unit of the target shale is constructed; Preferably, based on the organic molecular structural units of the target shale, constructing the organic matrix molecular model of the target shale includes: Based on the organic matter molecular structural unit of the target shale, the geometric optimization and molecular dynamics methods are used to optimize its molecular structure to obtain the optimized organic matter molecular structural unit; Integrate multiple optimized organic matter molecular structural units in a periodic cubic box to establish an initial molecular model of organic matter in the target shale; The organic matter structure relaxation is carried out on the initial molecular model of the organic matter of the target shale to obtain a balanced organic matter matrix molecular model as the organic matter matrix molecular model of the target shale.

4. The method according to claim 1, wherein: Based on the organic matrix molecular model of the target shale, combined with the organic pore content, organic fracture content and main pore and fracture types of the target shale, an organic block model of the target shale with corresponding pore and fracture structures is constructed, including: Based on the organic pore content, organic fracture content and main pore and fracture types of organic matter in the target shale, the pore and fracture structure of the organic matrix molecular model of the target shale is constructed, and the model is expanded in the X-axis, Y-axis and Z-axis directions to obtain the organic block model of the target shale.

5. The method according to claim 1, wherein: Based on the inorganic mineral molecular model of the target shale, combined with the inorganic pore content, inorganic fracture content and main pore and fracture types of the target shale, an inorganic pore and fracture block model of the target shale with corresponding pore and fracture structures is constructed, including: Cutting the inorganic mineral molecular model of the target shale to obtain the inorganic mineral matrix unit body of the target shale; Based on the inorganic pore content, inorganic fracture content and main pore and fracture types of the target shale, the pore and fracture structure of the inorganic mineral matrix unit of the target shale is constructed, and the model is expanded in the X-axis, Y-axis and Z-axis directions to obtain the inorganic pore and fracture block model of the target shale.

6. The method according to claim 4 or 5, wherein: In the process of constructing the pore structure and expanding the model in the X-axis, Y-axis, and Z-axis directions, when the main pore types only include micropores and / or ultramicropores, the pore structure is constructed first and then the model is expanded.

7. The method according to claim 6, wherein: When the main pore and fracture types of organic matter include only micropores and / or ultramicropores, based on the organic matrix molecular model of the target shale, combined with the organic pore content, organic fracture content and main pore and fracture types of organic matter of the target shale, the organic block model of the target shale with corresponding pore and fracture structure is constructed, including: Based on the main pore types of organic matter, the corresponding pore structure is constructed in the organic matrix molecular model of the target shale; The organic matrix molecular model of the target shale after constructing the pore structure is expanded by 2 times along the X-axis and Y-axis directions respectively, and then the pore structure corresponding to the main pore types of organic matter is constructed at the exact center of the model obtained after the expansion, and then the obtained model is further expanded along the Z-axis direction or along the X-axis and Z-axis directions or along the Y-axis and Z-axis directions or along the X-axis, Y-axis and Z-axis directions to obtain the organic block model of the target shale.

8. The method according to claim 4 or 5, wherein: In the process of constructing the hole and crack structure and expanding the model in the X-axis, Y-axis, and Z-axis directions, when the main hole and crack types include holes and cracks, the model is expanded first and then the hole and crack structure is constructed.

9. The method according to claim 8, wherein: When the main pore and fracture types of inorganic matter include pores and fractures, based on the inorganic mineral molecular model of the target shale, combined with the inorganic pore content, inorganic fracture content and main pore and fracture types of the target shale, the inorganic pore and fracture block model of the target shale with corresponding pore and fracture structures is constructed, including: Cutting the inorganic mineral molecular model of the target shale to obtain the inorganic mineral matrix unit body of the target shale; The dimensions of the inorganic mineral matrix unit body of the target shale in the X-axis and Y-axis directions are adjusted so that their common multiples are equal to the dimensions of the organic block model of the target shale in the X-axis and Y-axis directions; the inorganic mineral matrix unit body of the adjusted target shale is respectively expanded along the X-axis, Y-axis and Z-axis directions to obtain the inorganic block model of the target shale; wherein the dimensions of the inorganic block model of the target shale in the X-axis and Y-axis directions are equal to the dimensions of the organic block model of the target shale in the X-axis and Y-axis directions; Based on the main pore and fracture types of the inorganic matter in the target shale, the corresponding pore and fracture structure is constructed in the inorganic block model of the target shale. Then, based on the inorganic pore content and inorganic fracture content of the target shale, the sizes of the inorganic pores and inorganic fractures in the inorganic block model of the target shale are adjusted to satisfy the content ratio of the inorganic pores and inorganic fractures, thereby obtaining the inorganic pore and fracture block model of the target shale.

10. The method according to claim 1, wherein: When there is a fracture structure in the inorganic pore-fracture block model of the target shale, the fracture structure should be able to extend to the surface in contact with the organic block model of the target shale; When there is a fracture structure in the organic block model of the target shale, the fracture structure should be able to extend to the surface in contact with the inorganic pore-fracture block model of the target shale.

11. The method according to claim 1, wherein: The combined organic block model of the target shale and the inorganic pore block model of the target shale include: The organic block model of the target shale, the inorganic pore block model of the target shale, and the inverted organic block model of the target shale are superimposed in the same coordinate axis direction.

12. A device for constructing a molecular model of a shale composite porous medium, the device comprising: The first model building module: used to build an inorganic mineral molecular model of the target shale; The second model building module is used to build an organic matrix molecular model of the target shale; Parameter acquisition module: used to obtain the organic pore content, organic fracture content, inorganic pore content and inorganic fracture content of the target shale, as well as the main pore and fracture types of organic matter, the main pore and fracture types of inorganic matter, and the main pore and fracture types between organic matter and inorganic matter; The third model building module is used to build an organic block model of the target shale with corresponding pore and fracture structures based on the organic matrix molecular model of the target shale, combined with the organic pore content, organic fracture content and main pore and fracture types of the target shale. The fourth model building module is used to build an inorganic pore-fracture block model of the target shale with corresponding pore-fracture structures based on the inorganic mineral molecular model of the target shale, combined with the inorganic pore content, inorganic fracture content and main pore-fracture types of the target shale; The fifth model construction module is used to combine the organic block model of the target shale and the inorganic pore and fracture block model of the target shale, and form a pore and fracture structure corresponding to the main pore and fracture types between the organic matter and inorganic matter of the target shale at the contact position between the organic block model of the target shale and the inorganic pore and fracture block model of the target shale, and then adjust the pore and fracture structure in the model in combination with the organic pore content, organic fracture content, inorganic pore content and inorganic fracture content of the target shale to construct a shale composite pore and fracture medium molecular model.

13. The device according to claim 12, wherein: The third model building module is specifically used for: Based on the organic pore content, organic fracture content and main pore and fracture types of organic matter in the target shale, the pore and fracture structure of the organic matrix molecular model of the target shale is constructed, and the model is expanded in the X-axis, Y-axis and Z-axis directions to obtain the organic block model of the target shale.

14. The device according to claim 12, wherein: The fourth model building module includes: Inorganic mineral matrix unit body construction submodule: used to cut the inorganic mineral molecular model of the target shale to obtain the inorganic mineral matrix unit body of the target shale; The fourth model construction submodule is used to construct the pore structure of the inorganic mineral matrix unit body of the target shale based on the inorganic pore content, inorganic fracture content and main pore and fracture types of inorganic matter of the target shale, and to expand the model in the X-axis, Y-axis and Z-axis directions, so as to obtain the inorganic pore and fracture block model of the target shale.

15. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the computer program, the method according to any one of claims 1 to 11 is implemented.

16. A computer-readable storage medium storing a computer program, wherein the computer program implements the method according to any one of claims 1 to 11 when executed by a processor.

17. A computer program product, comprising a computer program, wherein when the computer program is executed by a processor, the method according to any one of claims 1 to 11 is implemented.

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