Model construction method and system for simulating core fluid

Abstract

The invention discloses a model construction method and system for simulating rock core fluid, and the method comprises the steps: obtaining an image of a rock core to be researched, determining a pore region and a matrix region on the rock core image according to the gray value distribution characteristics on the rock core image, and on the basis, combining the actual characteristic parameters of the rock core to be researched to obtain a model; a rock core model used for distinguishing pores and matrix areas in the rock core is constructed, and the actual characteristic parameters include but are not limited to actual pore data and actual matrix data; on the basis of the rock core model, fluid injection simulation is carried out on the rock core to be researched according to specified injection fluid, injection conditions and injection modes, distribution characteristics of the fluid in pores and matrix areas in the rock core model are obtained, and a rock core fluid model used for simulating actual fluid distribution characteristics is formed. According to the invention, rapid and accurate simulation of single-phase, two-phase and component-changed fluid flow in an actual rock core is realized, and a technical support is provided for quantitative evaluation of the flow law, distribution and recovery degree of the fluid.

Description

Technical Field

[0001] The invention belongs to the field of digital core technology, and in particular relates to a model building method and system for simulating core fluid. Background Art

[0002] At present, core-level flow simulation methods mainly include centimeter-scale core-scale macro-simulation in reservoir numerical simulation software, micro-simulation based on digital core micro-nanoscale, and micro-nanoscale micro-simulation formed by combining pore models established based on digital cores with micro-flow methods. Micro-flow methods mainly include lattice Boltzmann method, pore network model, Navier-Stokes equation, percolation theory and finite element method. The existing technology first constructs a three-dimensional digital model of complex pores in low-permeability media and converts it into a CAD solid model, and then uses COMSOL to establish multiple groups of characterizing unit body finite element models, based on numerical calculation of fluid transport characteristics in micro-nanopores under different boundary conditions. The existing technology also uses reconstructed digital cores and combines invasion-percolation theory to simulate the two-phase seepage process and study the changing characteristics of phase permeability curves before and after reservoir damage. In addition, the existing technology also uses pore network models and finite element methods to carry out single-phase flow simulation and dynamic "self-imbibition" flow simulation.

[0003] In the process of realizing the present invention, the inventors found that the above-mentioned prior art mainly uses microscopic simulation, and the simulation size is micro-nanoscale. However, for cores with strong microscopic heterogeneity characteristics, the micro-nanoscale cannot well describe the microscopic heterogeneity characteristics of the core and the impact of the current microscopic heterogeneity characteristics on the core fluid, so it is necessary to intervene in the core-level simulation control or alternative experiment to separately describe the impact of microscopic heterogeneity characteristics on the core fluid. Summary of the invention

[0004] In order to solve the above problems, an embodiment of the present invention provides a model construction method for simulating core fluid, the model construction method comprising: obtaining an image of a core to be studied, and determining the pore area and matrix area on the core image according to the gray value distribution characteristics on the core image, based on this, combined with the actual characteristic parameters of the core to be studied, constructing a core model for distinguishing the pore and matrix areas in the core, wherein the actual characteristic parameters include but are not limited to actual pore data and actual matrix data; based on the core model, according to the specified injection fluid, injection conditions and injection method, performing fluid injection simulation on the core to be studied, obtaining the distribution characteristics of the fluid in the pore and matrix areas in the core model, so as to form a core fluid model for simulating the actual fluid distribution characteristics.

[0005] Preferably, the size of the core to be studied is at the level of 10 to the first power cubic centimeters; and the resolution of the core image is at the level of 10 to the second power micrometers.

[0006] Preferably, the pore region on the core image includes conventional pores and throats for communicating the conventional pores, wherein the step of determining the pore region and the matrix region on the core image includes: converting the grayscale value distribution feature into a grayscale value histogram for representing the correlation between the grayscale value and the number of occurrences of the corresponding grayscale value, thereby determining the variation trend of the number of occurrences with the grayscale value, so as to obtain the boundary grayscale threshold between the matrix region and the throat; according to the boundary grayscale threshold, in combination with the actual pore data and the actual matrix data, determining a first grayscale range for representing the pore region on the core image and a second grayscale range for representing the matrix region on the core image, so as to obtain the pore region and the matrix region on the core image.

[0007] Preferably, in the process of determining the pore area and the matrix area on the core image, it includes: respectively configuring a first mark and a second mark for each pixel point on the core image within the first grayscale range and the second grayscale range, so as to construct the core model according to the marking results.

[0008] Preferably, after obtaining the core model, the model construction method further includes: determining the minimum grid of the core model suitable for simulating actual pore characteristics according to the throat size in the actual pore data, and meshing the core model according to the current minimum grid, thereby obtaining a gridded core model for conducting targeted research on the core model, wherein the number of minimum grids corresponding to the minimum throat size is greater than or equal to 4; and the size of the core model is greater than the sum of the actual pore area and the actual matrix area, and meets the penetration and diffusion requirements of the injected fluid.

[0009] Preferably, in the process of conducting targeted research on the core model, it includes: conducting research on the actual pore area and the actual matrix area of ​​the core model respectively, so as to coarsen the grid of the area not involved in the research in the core model to reduce the resolution of the area, wherein, when studying the distribution characteristics of the fluid in the actual pore area, the area not involved in the research is the matrix area; or, when studying the distribution characteristics of the fluid in the actual matrix area, the area not involved in the research is the pore area.

[0010] Preferably, in the process of coarsening the grid of the area not involved in the study in the core model, it includes: dividing the grids corresponding to the area not involved in the study into multiple groups of grid combinations to obtain the core model after grid coarsening, wherein the number of grids contained in each group of grid combinations is 4 or 9.

[0011] Preferably, in the process of forming the core fluid model, it includes: conducting fluid injection simulation based on the gridded core model passing through the actual pore area and the actual matrix area, respectively, wherein the specified fluid injection conditions are set according to the actual fluid flow pattern and the actual development plan, the actual fluid flow pattern includes but is not limited to: dialysis, displacement, diffusion, convection and seepage, and the actual development plan includes but is not limited to: gas injection, water injection, gas-water alternation and chemical flooding.

[0012] Preferably, the specified fluid injection conditions include but are not limited to: fluid injection temperature, fluid injection pressure, fluid phase number and fluid composition.

[0013] In a second aspect, the present invention also provides a model building system for simulating core fluid, the model building system comprising the following modules: a core model building module, which is used to obtain an image of the core to be studied, and determine the pore area and matrix area on the core image according to the gray value distribution characteristics on the core image, based on this, combined with the actual characteristic parameters of the core to be studied, to construct a core model for distinguishing the pore and matrix areas in the core, wherein the actual characteristic parameters include but are not limited to actual pore data and actual matrix data; a fluid model building module, which is used to perform fluid injection simulation on the core to be studied based on the core model according to specified injection fluids, injection conditions and injection methods, to obtain the distribution characteristics of the fluid in the pore and matrix areas in the core model, so as to form a core fluid model for simulating the actual fluid distribution characteristics.

[0014] Compared with the prior art, one or more embodiments of the above scheme may have the following advantages or beneficial effects:

[0015] The present invention discloses a model construction method and system for simulating core fluid. The model construction method first determines the pore area and matrix area on the core based on the image of the actual core, thereby constructing a core model with pore area characteristics and matrix area characteristics consistent with the actual core; then, a fluid injection simulation is performed on the currently constructed core model to determine the distribution characteristics of the fluid in the pore and matrix areas in the core model, thereby forming a core fluid model consistent with the fluid distribution characteristics of the actual core. The present invention solves the problems of slow simulation speed and small scale that exist in the traditional actual core model, which is only a micron-scale microscopic model, and at the same time makes up for the deficiency that the macroscopic model of the traditional core is only an ideal homogeneous model that cannot accurately express the core information, and ignores the influence of the core medium, and realizes the rapid and accurate simulation of the flow of single-phase, two-phase and component-changed fluids in the actual core, and provides technical support for quantitatively evaluating the flow law, distribution and recovery degree of the fluid.

[0016] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0018] Figure 1 This is a step diagram of a method for constructing a model for simulating core fluid according to an embodiment of the present application.

[0019] Figure 2 An example diagram of a core image of a model building method for simulating core fluid according to an embodiment of the present application.

[0020] Figure 3 This is an example diagram of a grayscale value histogram of a model building method for simulating core fluid according to an embodiment of the present application.

[0021] Figure 4 An example diagram of a core model of a model building method for simulating core fluid according to an embodiment of the present application.

[0022] Figure 5 An example diagram of a core fluid model for a model building method for simulating core fluid according to an embodiment of the present application.

[0023] Figure 6This is an example diagram of the distribution of remaining oil in a core where the injection scheme of the model building method for simulating core fluid in an embodiment of the present application is water flooding.

[0024] Figure 7 This is a comparison diagram of the core remaining oil distribution of different injection schemes of the model building method for simulating core fluid in an embodiment of the present application.

[0025] Figure 8 A module block diagram of a model building system for simulating core fluid according to an embodiment of the present application. DETAILED DESCRIPTION

[0026] The following will describe the implementation methods of the present invention in detail with reference to the accompanying drawings and embodiments, so that the implementation process of how the present invention applies technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly. It should be noted that as long as there is no conflict, the various embodiments of the present invention and the various features in the embodiments can be combined with each other, and the technical solutions formed are all within the protection scope of the present invention.

[0027] In addition, the steps shown in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowcharts, in some cases, the steps shown or described can be performed in an order different from that shown here.

[0028] At present, core-level flow simulation methods mainly include centimeter-scale core-scale macro-simulation in reservoir numerical simulation software, micro-simulation based on digital core micro-nanoscale, and micro-nanoscale micro-simulation formed by combining pore models established based on digital cores with micro-flow methods. Micro-flow methods mainly include lattice Boltzmann method, pore network model, Navier-Stokes equation, percolation theory and finite element method. The existing technology first constructs a three-dimensional digital model of complex pores in low-permeability media and converts it into a CAD solid model, and then uses COMSOL to establish multiple groups of characterizing unit body finite element models, based on numerical calculation of fluid transport characteristics in micro-nanopores under different boundary conditions. The existing technology also uses reconstructed digital cores and combines invasion-percolation theory to simulate the two-phase seepage process and study the changing characteristics of phase permeability curves before and after reservoir damage. In addition, the existing technology also uses pore network models and finite element methods to carry out single-phase flow simulation and dynamic "self-imbibition" flow simulation.

[0029] In the process of realizing the present invention, the inventors found that the above-mentioned prior art mainly uses microscopic simulation, and the simulation size is micro-nanoscale. However, for cores with strong microscopic heterogeneity characteristics, the micro-nanoscale cannot well describe the microscopic heterogeneity characteristics of the core and the impact of the current microscopic heterogeneity characteristics on the core fluid, so it is necessary to intervene in the core-level simulation control or alternative experiment to separately describe the impact of microscopic heterogeneity characteristics on the core fluid.

[0030] Therefore, in order to solve the above problems, the present invention proposes a model construction method and system for simulating core fluid. The model construction method first determines the pore area and matrix area on the core based on the image of the actual core, thereby constructing a core model with pore area characteristics and matrix area characteristics consistent with the actual core; then, the fluid injection simulation is performed on the currently constructed core model to determine the distribution characteristics of the fluid in the pore and matrix areas in the core model, thereby forming a core fluid model with fluid distribution characteristics consistent with the actual core. The present invention solves the problems of slow simulation speed and small scale that exist in the traditional actual core model, which is only a micron-scale microscopic model, and at the same time makes up for the deficiency that the macroscopic model of the traditional core is only an ideal homogeneous model that cannot accurately express the core information, and ignores the influence of the core medium, and realizes the rapid and accurate simulation of the flow of single-phase, two-phase and component-changing fluids in the actual core, and provides technical support for quantitatively evaluating the flow law, distribution and recovery degree of the fluid.

[0031] Embodiment 1

[0032] In view of the fact that the existing macroscopic simulation technology is a fluid flow simulation based on an ideal core, it is unable to truly reflect the microscopic characteristics of a core with strong microscopic heterogeneity characteristics. In other words, the fluid flow simulation results of the prior art do not involve the influence of microscopic heterogeneity on the fluid flow in the core, and the obtained fluid distribution characteristics in the core have a certain deviation from the actual situation. Accordingly, the present invention constructs a core model with the same microscopic characteristics as the current actual core based on the core image of the actual core, thereby achieving the purpose of accurately describing the actual internal structure of the core in the core model.

[0033] Figure 1 This is a step diagram of the model construction method for simulating core fluid in the embodiment of the present application. Figure 1 To illustrate the various steps of this method.

[0034] like Figure 1As shown, in step S110, an image of the core to be studied is obtained, and the pore area and matrix area on the core image are determined according to the gray value distribution characteristics on the core image. Based on this, combined with the actual characteristic parameters of the core to be studied, a core model for distinguishing the pore and matrix areas in the core is constructed. In an embodiment of the present application, first, the actual core to be studied is scanned to obtain a three-dimensional or two-dimensional core image of the current core to be studied. Afterwards, the core image is first converted into a grayscale image using image processing software or programming, and then the gray value of each pixel constituting the core image is identified, and a gray value distribution map of the core image is generated, thereby obtaining the gray value distribution characteristics of the core image. Next, by analyzing the number of occurrences of different gray values ​​in the gray value distribution characteristics on the core image, the pore area and matrix area on the core image are distinguished, and the pore area and matrix area on the core image are determined accordingly. Finally, the determined pore area and matrix area are matched with the actual characteristic parameters of the corresponding positions of the actual core to be studied, so as to construct a core model for distinguishing the pore and matrix areas in the core, wherein the actual characteristic parameters include but are not limited to actual pore data and actual matrix data.

[0035] The present invention scans the core to be studied of a specified size based on micron-level CT, providing a data basis for constructing a microscopic actual core model with microscopic core medium characteristics. In this way, the core fluid model formed based on the fluid flow simulation of the microscopic actual core model can accurately reflect the actual fluid flow characteristics. In a specific embodiment of the present application, the size of the core to be studied is at the level of 10 to the first power of cubic centimeters; and the resolution of the core image is at the level of 10 to the second power of micrometers.

[0036] Furthermore, the pore region on the core image includes conventional pores and throats for communicating the conventional pores, wherein, in the step of determining the pore region and the matrix region on the core image, the grayscale value distribution feature is first converted into a grayscale value histogram for representing the correlation between the grayscale value and the number of occurrences of the corresponding grayscale value, thereby determining the changing trend of the number of occurrences with the grayscale value, so as to obtain the boundary grayscale threshold between the matrix region and the throat; thereafter, according to the boundary grayscale threshold, combined with the actual pore data and the actual matrix data, a first grayscale range for representing the pore region on the core image and a second grayscale range for representing the matrix region on the core image are determined, thereby obtaining the pore region and the matrix region on the core image.

[0037] Specifically, the pore area on the core image includes conventional pores and throats for communicating conventional pores. In the step of determining the pore area and matrix area on the core image, the present embodiment first uses image processing software or programming to calculate the gray value histogram of the currently acquired three-dimensional or two-dimensional core image, so as to achieve the purpose of converting the gray value distribution feature into a gray value histogram for representing the correlation between the gray value and the number of occurrences of the corresponding gray value. Then, using the calculated gray value histogram, the trend of the number of occurrences with the gray value is directly read, and the boundary gray threshold between the matrix area and the throat is obtained according to the reading result. Among them, according to the reading result, the gray value distribution on the core image has two large peaks, one is the peak of the matrix gray value, and the other is the peak of the pore throat gray value. The junction of these two peak areas is the boundary gray threshold between the matrix area and the throat. Afterwards, the actual porosity and actual matrix data of the core to be studied are measured by experimental methods, and the specific boundary position of the matrix and pores in the core model is determined based on the actual porosity and actual matrix data, and then the determined boundary grayscale threshold is corrected based on the specific boundary position. Accordingly, according to the boundary grayscale threshold, combined with the actual pore data and the actual matrix data, the corrected boundary grayscale threshold is obtained to divide the matrix area and the pore area in the core model, so that the first grayscale range for representing the pore area on the core image and the second grayscale range for representing the matrix area on the core image can be obtained, thereby obtaining the accurate pore area and matrix area on the core image, effectively improving the matching degree between the microscopic features in the core model and the microscopic features of the actual core, and realizing the accurate description of the actual characteristics of the core.

[0038] In the process of determining the pore area and matrix area on the core image, the present invention configures the first mark and the second mark for each pixel point in the first grayscale range and the second grayscale range on the core image, respectively, so as to construct a core model according to the marking results. In a specific embodiment of the present application, image processing software or programming (for example: Eclipse) is used to determine each pixel point in the first grayscale range on the core image and configure a mark of "0" for each pixel point as the first mark, and to determine each pixel point in the second grayscale range on the core image and configure a mark of "1" for each pixel point as the second mark, to form a text file including pixel point positions and corresponding marks, and the text file is imported into the reservoir engineering numerical simulation software (for example: Eclipse, CMG, TNavigator), so as to achieve the purpose of constructing a core model with a size level of a centimeter-level numerical model.

[0039] After obtaining the core model, the present invention also determines the minimum grid of the core model suitable for simulating the actual pore characteristics according to the throat size in the actual pore data, and meshes the core model according to the current minimum grid, thereby obtaining a gridded core model for conducting targeted research on the core model. In an embodiment of the present application, the throat size in the actual pore data is first extracted, and the minimum number of pixels capable of reflecting the actual pore characteristics is determined according to the throat size, so that the grid size corresponding to the minimum number of pixels is used as the minimum grid. Afterwards, the core model is meshed according to the current minimum grid to obtain a gridded core model that is convenient for quantifying microscopic characteristics, and targeted research on the core model is carried out based on the gridded core model, realizing a rapid and accurate simulation of the core fluid distribution characteristics. In a specific embodiment of the present application, the number of minimum grids corresponding to the minimum throat size is greater than or equal to 4. In order to obtain the accurate seepage characteristics of the injected fluid, the size of the core model needs to be larger than the actual core to be studied (i.e., under the premise of ensuring that the core model has the actual pore area size and the actual matrix area size, the area size surrounding the pore area or the matrix area is expanded), so as to ensure that the part of the core model that matches the actual core to be studied is the same as the seepage characteristics of the core in the reservoir. Therefore, the size of the core model of the present embodiment is larger than the sum of the actual pore area and the actual matrix area, and meets the penetration and diffusion requirements of the injected fluid. By measuring the core pore permeability information of the actual core to be studied, and according to the core pore permeability information and the actual pore data, the seepage range of the fluid in the core model is expanded, and it is possible to obtain a core model that satisfies the size of the core model greater than the sum of the actual pore area and the actual matrix area, and meets the penetration and diffusion requirements of the injected fluid. It can be seen that the present invention is based on the expansion of the seepage range of the fluid in the core model, which effectively weakens the deviation between the actual fluid distribution characteristics finally simulated and the actual, so that the actual fluid distribution characteristics obtained are more consistent with the actual.

[0040] In the process of conducting targeted research on the core model, the present invention studies the actual pore area and the actual matrix area of ​​the core model respectively, so as to coarsen the mesh of the area not involved in the research in the core model to reduce the resolution of the area. For the case where the research object is the matrix area and the pore area, the resolution of the entire core model constructed is reduced by an overall coarsening method to reduce the space occupied by the core model in the corresponding calculation unit and improve the operation speed. For the case where the research object of this embodiment is a single area, the area not involved in the research does not participate in the acquisition of the actual fluid distribution characteristics, so this embodiment studies the actual pore area and the actual matrix area of ​​the core model respectively, and then uses a local coarsening method to reduce the resolution of the area not involved in the research in the constructed core model to reduce the space occupied by the core model in the corresponding calculation unit and improve the operation speed. Among them, when studying the distribution characteristics of the fluid in the actual pore area, the area not involved in the research is the matrix area; or, when studying the distribution characteristics of the fluid in the actual matrix area, the area not involved in the research is the pore area.

[0041] Further, in the process of coarsening the mesh of the area not involved in the study in the core model, the present invention divides the mesh corresponding to the area not involved in the study into multiple groups of mesh combinations to obtain a core model after mesh coarsening. Specifically, this embodiment determines the area in the core model that can currently be coarsened (the area not involved in the study) according to actual research needs, and divides the mesh corresponding to the area not currently involved in the study (ie, the matrix area or the pore area) into multiple groups of mesh combinations to obtain a core model with a coarsened mesh after mesh coarsening. Wherein, each grid combination contains multiple grids, and the edges of the grids forming the periphery of the grid combination are used as the edges of the single coarsened grid after coarsening to obtain the coarsened mesh corresponding to each grid combination. In a specific embodiment of the present application, the number of grids contained in each group of grid combinations is 4 or 9.

[0042] Further, in step S120, based on the core model constructed in step S110, according to the specified injection fluid, injection conditions and injection method, the core to be studied is subjected to fluid injection simulation, and the distribution characteristics of the fluid in the pores and matrix areas within the core model are obtained to form a core fluid model for simulating the actual fluid distribution characteristics. In an embodiment of the present application, according to the core environment requirements to be studied, the environmental parameters such as the temperature and pressure inside the core when the core to be studied is subjected to fluid injection simulation are determined, and the determined environmental parameters are loaded into the core model, thereby utilizing the constructed core model carrying environmental parameters. Next, the injection fluid required for the study is specified for the simulation process, and the corresponding fluid injection conditions such as fluid injection temperature, fluid injection pressure, fluid phase number and fluid component are specified for the current injection fluid, as well as the corresponding injection methods such as dialysis, displacement, diffusion, convection and seepage. Further, according to the specified injection fluid, injection conditions and injection method, the core to be studied is subjected to fluid injection simulation. During the simulation process, the distribution characteristics of the fluid in the pores and matrix areas of the core model are obtained in real time, so that the purpose of forming a core fluid model for simulating the actual fluid distribution characteristics can be achieved. Accordingly, the present invention constructs a core fluid model based on a core model with accurate core characteristics, realizes the rapid and accurate construction of a macro flow model (i.e., a core fluid model) with microscopic core medium characteristics, and fills the gap of the lack of medium microscopic heterogeneity in flow simulation, and can quickly and accurately obtain the actual fluid distribution characteristics.

[0043] Further, in the process of forming the core fluid model, the present invention carries out fluid injection simulation based on the gridded core model passing through the actual pore area and the actual matrix area, respectively. Specifically, for the case where the research object of this embodiment is a single area, the specified fluid injection conditions are specifically implemented to the actual reservoir as needed, and the fluid injection simulation is implemented for the corresponding gridded core model after grid coarsening to obtain the actual fluid distribution characteristics of the research object area. Among them, the specified fluid injection conditions are set according to the actual fluid flow pattern and the actual development plan. The actual fluid flow pattern includes but is not limited to: dialysis, displacement, diffusion, convection and seepage, and the actual development plan includes but is not limited to: gas injection, water injection, gas-water alternation and chemical drive. Accordingly, the present invention realizes the effective acquisition of the actual fluid distribution characteristics formed by different types of specified fluid injection conditions by constructing a core-level seepage numerical model (i.e., core fluid model) containing the fluid's own properties, flow patterns and development plans.

[0044] In the embodiment of the present application, the specified fluid injection conditions include but are not limited to: fluid injection temperature, fluid injection pressure, fluid phase number and fluid composition. The fluid phase number of this embodiment is single phase, two phases or composition.

[0045] Embodiment 2

[0046] In a specific embodiment of the present application, according to the model building method described in Example 1, first, the actual target core is scanned by CT to obtain the following Figure 2 The three-dimensional image of the target core is shown ( Figure 2 , which is an example of a core image of the model building method for simulating core fluid in the embodiment of the present application). Then, the core model size is determined to be 1.5cm×1.5cm×1.5cm, and the grid size is determined to be 0.006cm. Next, the Matlab programming program is used to identify the following Figure 3 Gray value histogram of the core 3D scanning image shown ( Figure 3 1 is an example diagram of a grayscale value histogram of a model building method for simulating core fluid in an embodiment of the present application). After the grayscale value histogram is identified, the grayscale value histogram of the three-dimensional scanning image of the core is analyzed using image processing software or programming, and the analysis result is further combined with the experimentally measured porosity data, so that the demarcation grayscale threshold is determined to be 120, so as to use the current demarcation grayscale threshold to distinguish between pores and matrix.

[0047] In the process of using the current demarcation grayscale threshold to distinguish pores from matrix, the pixel points with grayscale values ​​within the matrix range on the core three-dimensional scanning image are extracted and marked as "0" by image processing software or programming, and the pixel points with grayscale values ​​within the pore range are extracted and marked as "1" and exported to form a text file. The text file is imported into the reservoir engineering numerical simulation software (such as Eclipse, CMG, TNavigator), and the purpose of constructing a core model with a centimeter-level numerical model can be achieved.

[0048] Next, after the core model is obtained, the core model is meshed based on the determined core model size and grid size to obtain the following: Figure 4 The grid size shown is 250×250×250 grid core model ( Figure 4 An example diagram of a core model for a model building method for simulating core fluid according to an embodiment of the present application).

[0049] This embodiment is a case where the research object is the matrix area and the pore area, so it is necessary to use an overall coarsening method to reduce the resolution of the entire core model constructed, so as to reduce the space occupied by the core model in the corresponding calculation unit and improve the grid coarsening scheme of the calculation speed. At this time, the grid size of the core model after grid coarsening is 0.3cm×0.3cm×0.3cm, and the number of coarsened grids is 50×50×50.

[0050] According to the core environment requirements to be studied, the temperature and pressure inside the core are determined to be 60°C and 50MPa respectively when simulating fluid injection into the target core. The currently determined environmental parameters are loaded into the core model. Then, the core model with the current environmental parameters is constructed to simulate fluid injection into the target core according to the specified fluid injection conditions currently required for the actual reservoir. Figure 5 The core fluid model ( Figure 5 1 is an example diagram of a core fluid model of a model construction method for simulating core fluid in an embodiment of the present application). The core fluid model of this embodiment is a single-phase, two-phase or component fluid model. In a specific embodiment of the present application, when the specified fluid injection condition is water flooding, the following is obtained: Figure 6 The core fluid model shown ( Figure 6 This is an example diagram of the distribution of remaining oil in a core where the injection scheme of the model building method for simulating core fluid in an embodiment of the present application is water flooding).

[0051] In the embodiment of the present application, the specified fluid injection conditions are gas injection, water injection and gas injection mixture, and water injection and gas injection and water injection mixture, and the injection and production method is top injection and bottom production. The core fluid models corresponding to the different specified fluid injection conditions are as follows: Figure 7 As shown ( Figure 7 3. This is a comparison diagram of the distribution of remaining oil in the core of different injection schemes of the model building method for simulating core fluid in an embodiment of the present application).

[0052] Embodiment 3

[0053] Based on the model building method for simulating core fluid described in the above-mentioned embodiment 1, the present invention also provides a model building system for simulating core fluid (hereinafter referred to as "model building system"). Figure 8 A module block diagram of a model building system for simulating core fluid according to an embodiment of the present application.

[0054] like Figure 8As shown, the model building system in this embodiment includes: a core model building module 81 and a fluid model building module 82. Specifically, the core model building module 81 is implemented according to the method described in step S110 above, and is configured to obtain an image of the core to be studied, and determine the pore area and matrix area on the core image according to the gray value distribution characteristics on the core image, based on which, combined with the actual characteristic parameters of the core to be studied, a core model for distinguishing the pore and matrix areas in the core is constructed, wherein the actual characteristic parameters include but are not limited to actual pore data and actual matrix data; the fluid model building module 82 is implemented according to the method described in step S120 above, and is configured to perform fluid injection simulation on the core to be studied according to the specified injection fluid, injection conditions and injection method based on the core model constructed by the core model building module 81, and obtain the distribution characteristics of the fluid in the pore and matrix areas in the core model, so as to form a core fluid model for simulating the actual fluid distribution characteristics.

[0055] The present invention discloses a model construction method and system for simulating core fluid. The model construction method first determines the pore area and matrix area on the core based on the image of the actual core, thereby constructing a core model with pore area characteristics and matrix area characteristics consistent with the actual core; then, a fluid injection simulation is performed on the currently constructed core model to determine the distribution characteristics of the fluid in the pore and matrix areas in the core model, thereby forming a core fluid model consistent with the fluid distribution characteristics of the actual core. The present invention solves the problems of slow simulation speed and small scale that exist in the traditional actual core model, which is only a micron-scale microscopic model, and at the same time makes up for the deficiency that the macroscopic model of the traditional core is only an ideal homogeneous model that cannot accurately express the core information, and ignores the influence of the core medium, and realizes the rapid and accurate simulation of the flow of single-phase, two-phase and component-changed fluids in the actual core, and provides technical support for quantitatively evaluating the flow law, distribution and recovery degree of the fluid. In addition, compared with the existing microscopic simulation technology, which is a micrometer-scale simulation, the model of the present invention has a larger scale and a shorter simulation time, and can better describe the impact of microscopic heterogeneity.

[0056] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any person familiar with the technology within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

[0057] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art may make various corresponding changes and modifications based on the present invention, but these corresponding changes and modifications should all fall within the scope of protection of the claims of the present invention.

[0058] It should be understood by those skilled in the art that the modules or steps of the present invention described above can be implemented by a general-purpose computing device, they can be concentrated on a single computing device, or distributed on a network composed of multiple computing devices, and optionally, they can be implemented by a program code executable by a computing device, so that they can be stored in a storage device and executed by the computing device, or they can be made into individual integrated circuit modules, or multiple modules or steps therein can be made into a single integrated circuit module for implementation. Thus, the present invention is not limited to any specific combination of hardware and software.

[0059] Although the embodiments disclosed in the present invention are as above, the above contents are only embodiments adopted for facilitating the understanding of the present invention and are not intended to limit the present invention. Any technician in the technical field to which the present invention belongs can make any modifications and changes in the form and details of the implementation without departing from the spirit and scope disclosed in the present invention, but the patent protection scope of the present invention shall still be subject to the scope defined in the attached claims.

Claims

1. A model construction method for simulating core fluid, characterized in that: The model building method comprises: Acquire an image of the core to be studied, and determine the pore area and matrix area on the core image according to the gray value distribution characteristics on the core image, and based on this, construct a core model for distinguishing the pore and matrix areas in the core in combination with actual characteristic parameters of the core to be studied, wherein the actual characteristic parameters include but are not limited to actual pore data and actual matrix data; Based on the core model, according to the specified injection fluid, injection conditions and injection method, fluid injection simulation is performed on the core to be studied to obtain the distribution characteristics of the fluid in the pores and matrix areas within the core model, so as to form a core fluid model for simulating the actual fluid distribution characteristics.

2. The model building method according to claim 1, characterized in that: The size of the core to be studied is on the order of 10 to the first power cubic centimeters; and The resolution of the core image is at the level of 10 to the square of micrometers.

3. The model building method according to claim 1 or 2, characterized in that: The pore region on the core image includes conventional pores and throats for communicating the conventional pores, wherein the step of determining the pore region and the matrix region on the core image includes: Converting the gray value distribution characteristics into a gray value histogram for representing the correlation between the gray value and the number of occurrences of the corresponding gray value, thereby determining the variation trend of the number of occurrences with the gray value, so as to obtain the boundary gray threshold between the matrix area and the throat; According to the demarcation grayscale threshold, in combination with the actual pore data and the actual matrix data, a first grayscale range for representing the pore area on the core image and a second grayscale range for representing the matrix area on the core image are determined, thereby obtaining the pore area and the matrix area on the core image.

4. The model building method according to claim 3, characterized in that: The process of determining the pore area and the matrix area on the core image includes: A first mark and a second mark are respectively configured for each pixel point in the first grayscale range and the second grayscale range on the core image, so as to construct the core model according to the marking results.

5. The model building method according to any one of claims 2 to 4, characterized in that: After obtaining the core model, the model building method further includes: According to the throat size in the actual pore data, the minimum grid of the core model suitable for simulating the actual pore characteristics is determined, and the core model is meshed according to the current minimum grid, so as to obtain a gridded core model for carrying out targeted research on the core model, wherein: The number of the smallest grid cells corresponding to the smallest throat size is greater than or equal to 4; and The size of the core model is larger than the sum of the actual pore area and the actual matrix area, and meets the penetration and diffusion requirements of the injected fluid.

6. The model building method according to claim 5, characterized in that: In the process of conducting targeted research on the core model, the following aspects were included: The actual pore area and the actual matrix area of ​​the core model are studied respectively, so that the mesh of the area not involved in the study in the core model is coarsened to reduce the resolution of the area, wherein: When studying the distribution characteristics of fluid in the actual pore area, the area not involved in the study is the matrix area; or, When studying the distribution characteristics of fluid in the actual matrix area, the area not involved in the study is the pore area.

7. The model building method according to claim 6, characterized in that: The process of coarsening the mesh of the area not involved in the study in the core model includes: The grids corresponding to the areas not involved in the study are divided into multiple groups of grid combinations to obtain a core model after grid coarsening, wherein each group of grid combinations contains 4 or 9 grids.

8. The model building method according to claim 6 or 7, characterized in that: The process of forming the core fluid model includes: Fluid injection simulation is performed based on the gridded core model passing through the actual pore area and the actual matrix area, respectively, wherein the specified fluid injection conditions are set according to the actual fluid flow pattern and the actual development plan, wherein the actual fluid flow pattern includes but is not limited to: dialysis, displacement, diffusion, convection and seepage, and the actual development plan includes but is not limited to: gas injection, water injection, gas-water alternation and chemical flooding.

9. The model building method according to claim 8, characterized in that: The specified fluid injection conditions include, but are not limited to, fluid injection temperature, fluid injection pressure, fluid phase number and fluid composition.

10. A model building system for simulating core fluid, characterized in that: The model building system includes the following modules: A core model building module, which is used to obtain an image of the core to be studied, and determine the pore area and matrix area on the core image according to the gray value distribution characteristics on the core image, based on which, combined with the actual characteristic parameters of the core to be studied, a core model for distinguishing the pore and matrix areas in the core is built, wherein the actual characteristic parameters include but are not limited to actual pore data and actual matrix data; A fluid model building module is used to perform fluid injection simulation on the core to be studied based on the core model according to the specified injection fluid, injection conditions and injection method, to obtain the distribution characteristics of the fluid in the pores and matrix areas within the core model, so as to form a core fluid model for simulating the actual fluid distribution characteristics.

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