Critical path-based oil-water two-phase seepage model construction method, system and medium

Abstract

The invention discloses an oil-water two-phase seepage model construction method and system based on a critical path and a medium. Relates to the technical field of oil-gas field development. According to the scheme, a traditional black oil model simulation technology and a critical radius technology based on a critical path seepage theory are combined, and on the basis of ensuring the scale of an oil reservoir model, the oil-water two-phase seepage characteristic oil reservoir simulation method considering the micro-scale critical path is provided; microscopic characteristics such as a pore throat structure in a real reservoir rock are restored to the greatest extent by using the critical radius, and phenomena such as a dominant channel (critical path) of seepage of oil-water two-phase fluid in a pore throat and factors influencing displacement efficiency are researched from a microscopic perspective, so that a higher-precision oil reservoir simulation analysis result is obtained; according to the scheme, the flow and pressure of each component of oil and water are calculated directly based on the critical radius and the critical path length, a static oil-water relative permeability curve does not need to be input in the simulation process, and the stress state and the change process of each part of the oil reservoir can be reflected more directly.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas field development, and in particular to a method, system and medium for constructing an oil-water two-phase seepage model based on a critical path. Background Art

[0002] Oil is an indispensable strategic resource for a country's survival and development. How to maximize the extraction of underground energy and transform it into a driving force for economic development is particularly important and plays a key role in national energy planning and deployment. After years of research, reservoir development methods have become mature. Most researchers use numerical simulation methods to reduce development costs, and formulate reasonable opening plans and provide scientific guidance based on simulation results. The reservoir numerical simulation method refers to the use of models to study the dynamic changes of reservoirs, including physical simulation and mathematical (numerical) simulation. Physical simulation refers to the indoor study of reservoir development dynamics, while the main principle of the reservoir numerical simulation method is to use a group of partial differential equations to describe the state of reservoir exploitation and obtain the changes in development indicators through computer numerical solution. The reservoir numerical simulation method can consider the influence of factors such as reservoir geometry, heterogeneity, changes in rock and fluid properties, well network mode and production on dynamics. It is the method that considers the most factors in reservoir dynamic research so far and has become one of the important means of reservoir development research; the main feature of the numerical simulation method is to analyze and predict the development dynamics by simulating and analyzing the fluid and energy distribution in the reservoir.

[0003] In the actual oil production process, the application of the oil-water two-phase model is crucial because it can accurately describe and predict the complex flow behavior of the oil-water two-phase fluid in the reservoir. By constructing a mathematical model and using numerical simulation technology, the model can simulate the dynamic changes of the water-to-oil process and the advancement of the oil-water front, providing a scientific basis for formulating and optimizing oilfield development plans, evaluating the performance of submersible pumps, optimizing oil-water separation technology, and conducting dynamic monitoring and analysis of reservoirs, thereby effectively improving the recovery rate and economic benefits of the oilfield.

[0004] The oil-water two-phase seepage model in the traditional black oil model is a simplified model used to simulate the flow of oil and water in the reservoir. Although this model is a widely used basic tool in reservoir simulation, it has some defects in the actual oil production process: it ignores the heterogeneity of reservoir rocks, and the geological heterogeneity of the reservoir, the existence of fractures, and the small-scale characteristics are usually simplified in the form of grids (grid sides are usually tens of meters long), which cannot accurately describe the actual reservoir conditions, and cannot directly consider the influence of microscopic factors such as rock pore throat characteristics and dynamic seepage characteristics of dynamic multiphase fluids at pore scales (micrometer and centimeter scales) on the macroscopic seepage process. At the same time, due to the simplification of complex flow mechanisms, complex flow mechanisms such as gravity effects in multiphase flow are handled roughly. In addition, in the multiphase seepage simulation of the traditional black oil model, a static oil-water relative permeability curve needs to be input to describe the oil-water content, viscosity and capillary force of each grid point, and to calculate the grid conductivity. However, in the actual seepage process, the oil-water relative permeability curve is a dynamic data that will change dynamically with time and fluid position. Therefore, the relative permeability curve input by the traditional simulation method has certain defects. These defects limit the use of traditional black oil models under complex reservoir conditions. Summary of the invention

[0005] The technical problem to be solved by the present invention is that the oil-water two-phase seepage model in the traditional black oil model relies on the relative permeability curve to be constructed, but the oil-water relative permeability curve in the actual seepage process is a dynamic data, which will dynamically move and change with time and fluid position, resulting in a large application defect in the oil-water two-phase seepage model constructed by the traditional simulation method; the present invention aims to provide a construction method, system and medium for the oil-water two-phase seepage model based on the critical path, and the flow rate and pressure of each component of oil and water can be directly calculated based on the critical radius and the critical path length for the dynamic pore fluid pressure, gravity and capillary force of each grid (spatial position) of the reservoir during the oil-water two-phase seepage process. It is no longer necessary to input the static oil-water relative permeability curve during the simulation process, and the stress state and change process of each part of the reservoir can be more directly reflected. The pressure sweep range, the spatial position and movement state of the oil-water two-phase fluid interface can be directly reflected through the calculation results.

[0006] The present invention is achieved through the following technical solutions:

[0007] This solution provides a method for constructing an oil-water two-phase seepage model based on a critical path, including:

[0008] Based on nuclear magnetic logging technology and critical path seepage theory, a critical radius model of oil-water two-phase fluid flow process is established;

[0009] Based on the critical radius model and under equivalent assumptions, an oil-water two-phase numerical model suitable for a single well in an oil reservoir is established;

[0010] The oil-water two-phase numerical model is solved to obtain the simulation result of the oil-water mutual phase displacement.

[0011] Working principle of this scheme: the oil-water two-phase seepage model in the traditional black oil model relies on the relative permeability curve to be constructed, but the oil-water relative permeability curve in the actual seepage process is a dynamic data, which will dynamically move and change with time and fluid position, resulting in large application defects in the oil-water two-phase seepage model constructed by the traditional simulation method; the purpose of the present invention is to provide a method, system and medium for constructing an oil-water two-phase seepage model based on a critical path, combining the respective advantages of the traditional black oil model simulation technology and the critical radius technology based on the critical path theory, and on the basis of ensuring the scale of the reservoir model, a reservoir simulation method for oil-water two-phase seepage characteristics considering the microscopic critical path is proposed, which can use the critical radius to restore the microscopic characteristics such as the pore throat structure inside the real reservoir rock to the greatest extent, and can study the critical path (dominant channel) of the seepage of oil-water two-phase fluid in the pore throat and the factors affecting the displacement efficiency from a microscopic perspective, so as to obtain more accurate reservoir simulation analysis results. In addition, the present invention can directly calculate the flow rate and pressure of each oil and water component based on the critical radius and critical path length for the stress states of dynamic pore fluid pressure, gravity and capillary force of each grid (spatial position) of the reservoir during the oil-water two-phase seepage process. There is no need to input a static oil-water relative permeability curve during the simulation process, and it can more directly reflect the stress state and change process of each part of the reservoir. The pressure sweep range, the spatial position and movement state of the oil-water two-phase fluid interface can be directly reflected through the calculation results.

[0012] A further optimization scheme is to establish a critical radius model based on nuclear magnetic logging technology and critical path seepage theory, including the following methods:

[0013] Construct a well location grid model and calculate the permeability and porosity of each grid;

[0014] Based on the critical path seepage theory, the actual rock pore throat characteristics and seepage channel characteristics are considered in the well location grid model to construct a critical radius model of the oil-water two-phase fluid flow process; the critical radius model includes:

[0015] The critical radius r between grids i and j cij for:

[0016]

[0017] Among them, k ij represents the permeability between adjacent grids i and j, m 2 ; φ ij represents the porosity between adjacent grids i and j, dimensionless; τ represents the tortuosity, dimensionless; σz Represents the coefficient of variation of rock heterogeneity, dimensionless.

[0018] A further optimization scheme is that the equivalent assumptions include:

[0019] a. In the critical radius model, the critical path is the main channel for fluid seepage, and the pressure drop caused by fluid flow mainly occurs in the critical path;

[0020] b, there is only one two-phase fluid interface between the oil and water two-phase fluids in the critical path;

[0021] c, the two fluids flowing in the network are immiscible;

[0022] d, Piston-like displacement occurs in the critical path.

[0023] A further optimization scheme is to establish an oil-water two-phase numerical model suitable for a single well scale of an oil reservoir based on the critical radius model under equivalent assumptions; including methods:

[0024] Calculate the equivalent capillary force p of the reservoir grid caused by the oil-water interface in the critical path cij (Unit: Pa): p cij =2γcosθ / r cij ; Among them, r cij represents the critical radius of the critical path between grid i and grid j, m; γ represents the interfacial tension between oil and water phases, N / m; θ represents the wetting angle, °;

[0025] Calculate the conductivity of the oil-water two-phase fluid between any two grids based on the critical path;

[0026] Obtain the effective viscosity and density of the oil-water two-phase fluid in the critical path between reservoir grids;

[0027] Based on the critical radius, the conductivity, effective viscosity and density are input into the mass conservation equation to construct the differential equations of oil-water two-phase flow and pressure diffusion;

[0028] The oil-water two-phase numerical model is obtained by numerically simulating the oil-water two-phase flow and pressure diffusion differential equations.

[0029] A further optimization scheme is to calculate the conductivity of the oil-water two-phase fluid between any two grids based on the critical path; including the method:

[0030] When oil and water coexist in the critical path between grid i and grid j, the conductivity ξ of the oil-water two-phase fluid in the equivalent capillary force of the reservoir grid is ij [Unit: m 3 / (Pa·s)] is:

[0031]

[0032] Then the pressure difference Δp between grid i and grid j is ij The flow rate q of the oil-water two-phase mixed fluid under (unit Pa) ij (Unit: m 3 / s)Flow meets:

[0033]

[0034] Δp ij =p i -p j -p cij ;

[0035] Among them, p i =p oi +ρ ow G JZ i , p oi is the pore pressure of grid i, Pa; ρ ow is the density of the mixed fluid, kg / m 3 , g is the acceleration due to gravity, 9.8m / s 2 ;p j =p oj +ρ ow G JZ j , p oj is the pore pressure of grid j, Pa; Z i is the vertical height of grid i, m; Z j The vertical height of grid j, m; p cij The equivalent capillary force of the reservoir grid is Pa; τ is the tortuosity, dimensionless; l ij is the grid side length, m; cij is the effective porosity, dimensionless; r cij is the critical radius, m; η eff is the effective viscosity of the mixed fluid, Pa·s.

[0036] A further optimization scheme is that the effective viscosity and density of the oil-water two-phase fluid in the critical path between the reservoir grids are obtained; including the method:

[0037] The effective viscosity η of the oil-water two-phase fluid in the critical path between reservoir grids is calculated according to the following formula eff :

[0038] η eff =B w μ w X ij +B o μ o (1-X ij )

[0039] Among them Bw Represents the volume coefficient of water, dimensionless; B o Represents the volume coefficient of oil, dimensionless; μ w Indicates the viscosity of water, Pa·s; μ o Indicates the viscosity of the oil, Pa·s; X ij represents a dimensionless number related to the position of the oil-water interface, (0≤X ij ≤1), which is the location of the concave meniscus divided by the length of the entire critical path;

[0040] The density of the oil-water two-phase fluid in the critical path between reservoir grids is calculated according to the following formula: ow =ρ w X ij +ρ o (1-X ij );

[0041] Among them, ρ w represents the density of water; ρ o Indicates the density of oil.

[0042] A further optimization scheme is that, based on the mass conservation equation, the oil-water two-phase flow and pressure diffusion differential equations include:

[0043]

[0044] Where i represents any number from 1 to N, and N represents the total number of grids. represents the conductivity between two adjacent grids i and j, m 3 / (Pa·s);Δp ij represents the pressure difference between grid i and grid j, Pa; ψ = φ c0i V bi C tow ; φ c0i represents the initial porosity of grid i, dimensionless; V bi represents the volume of grid i, m 3 ; Δt is the simulation time step, s; Δp i represents the change in pressure of grid i within Δt, Pa; C tow (Pa -1 ) is the comprehensive compressibility coefficient of the oil and water phases. Since the compressibility of oil and water is roughly equal, to simplify the calculation, C tow The value of can be consistent with the compressibility coefficient of oil or water.

[0045] A further optimization scheme is that solving the oil-water two-phase numerical model to obtain the oil-water two-phase displacement simulation result includes the following method:

[0046] Combined with the oil-water displacement process, in the process of numerical simulation of the oil-water two-phase flow and pressure diffusion differential equations, the interface movement process and distribution state are calculated according to the time step update, and the fluid conductivity of all grids is updated;

[0047] The pressure and flow rate of different grids are solved, and the global pressure field at different times is solved by the conjugate gradient method.

[0048] This solution provides a critical path-based oil-water two-phase seepage model construction system, which is characterized by being used to implement the above-mentioned critical path-based oil-water two-phase seepage model construction method; the system includes:

[0049] The first building module is used to establish a critical radius model of the oil-water two-phase fluid flow process based on nuclear magnetic logging technology and critical path seepage theory;

[0050] The second establishment module is used to establish an oil-water two-phase numerical model applicable to a single well scale of an oil reservoir based on the critical radius model under equivalent assumptions;

[0051] The solution module is used to solve the oil-water two-phase numerical model to obtain the oil-water mutual displacement simulation result.

[0052] The present solution also provides a computer-readable medium having a computer program stored thereon, and the computer program is executed by a processor to implement the above-mentioned method for constructing an oil-water two-phase seepage model based on a critical path.

[0053] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0054] 1. The present invention provides a method, system and medium for constructing an oil-water two-phase seepage model based on a critical path; combining the respective advantages of traditional black oil model simulation technology and critical radius technology based on critical path seepage theory, on the basis of ensuring the scale of the reservoir model, a reservoir simulation method for oil-water two-phase seepage characteristics considering the microscopic critical path is proposed, which can use the critical radius to restore the microscopic characteristics such as the pore throat structure inside the real reservoir rock to the greatest extent, and can study the critical path (dominant channel) of the seepage of oil-water two-phase fluid in the pore throat and the factors affecting the displacement efficiency from a microscopic perspective, so as to obtain more accurate reservoir simulation analysis results.

[0055] 2. The present invention provides a method, system and medium for constructing an oil-water two-phase seepage model based on a critical path; for the stress states of dynamic pore fluid pressure, gravity and capillary force of each grid (spatial position) in the reservoir during the oil-water two-phase seepage process, the flow rate and pressure of each oil and water component can be directly calculated based on the critical radius and critical path length. There is no need to input a static oil-water relative permeability curve during the simulation process, which can more directly reflect the stress state and change process of each part of the reservoir, and the pressure sweep range, the spatial position and movement state of the oil-water two-phase fluid interface can be directly reflected through the calculation results. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other relevant drawings can be obtained based on these drawings without creative work. In the drawings:

[0057] Figure 1 A schematic diagram of the process of constructing an oil-water two-phase flow model based on a critical path;

[0058] Figure 2 Schematic diagram of the oil-water interface position when the two phases coexist on the critical path;

[0059] Figure 3 This is a schematic diagram of water-to-oil simulation at a single-well scale in a water-to-oil reservoir;

[0060] Figure 4 Schematic diagram of oil-water displacement simulation at the scale of a single well in an oil reservoir. DETAILED DESCRIPTION

[0061] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0062] The oil-water two-phase seepage model in the traditional black oil model relies on the relative permeability curve to be constructed. However, in the actual seepage process, the oil-water relative permeability curve is a dynamic data, which will dynamically move and change with time and fluid position, resulting in a large application defect in the oil-water two-phase seepage model constructed by the traditional simulation method. In view of this, the present invention provides the following embodiments to solve the above technical problems.

[0063] Example 1

[0064] This embodiment provides a method for constructing an oil-water two-phase seepage model based on a critical path, such as Figure 1 As shown, including:

[0065] Step 1: Based on nuclear magnetic logging technology and critical path seepage theory, a critical radius model of the oil-water two-phase fluid flow process is established; this step specifically includes the following methods:

[0066] S11, construct a well location grid model and calculate the permeability and porosity of each grid;

[0067] S12, based on the critical path seepage theory, the actual rock pore throat characteristics and seepage channel characteristics are considered in the well location grid model to construct a critical radius model of the oil-water two-phase fluid flow process; the critical radius model includes:

[0068] The critical radius r between grids i and j cij (Unit: m) is:

[0069]

[0070] Among them, k ij represents the permeability between adjacent grids i and j, m 2 ; φ ij represents the porosity between adjacent grids i and j, dimensionless; τ represents the tortuosity, dimensionless; σ z Represents the coefficient of variation of rock heterogeneity, dimensionless.

[0071] Step 2: Based on the critical radius model and under equivalent assumptions, an oil-water two-phase numerical model applicable to a single well in the reservoir is established; the equivalent assumptions include:

[0072] a. In the critical radius model, the critical path is the main channel for fluid seepage, and the pressure drop caused by fluid flow mainly occurs in the critical path;

[0073] b, there is only one two-phase fluid interface between the oil and water two-phase fluids in the critical path;

[0074] c, the two fluids flowing in the network are immiscible;

[0075] d, Piston-like displacement occurs in the critical path.

[0076] Based on the critical radius model and under equivalent assumptions, an oil-water two-phase numerical model suitable for a single well in an oil reservoir is established; including methods:

[0077] S21, calculate the equivalent capillary force p of the reservoir grid caused by the oil-water interface in the critical path cij :p cij =2γcosθ / r cij ; Among them, r cij represents the critical radius of the critical path between grid i and grid j, m; γ represents the interfacial tension between oil and water phases, N / m; θ represents the wetting angle, °;

[0078] S22, calculating the conductivity of the oil-water two-phase fluid between any two grids based on the critical path; including the method:

[0079] When oil and water coexist in the critical path between grid i and grid j, the conductivity ξ of the oil-water two-phase fluid in the critical path ij [Unit: m 3 / (Pa·s)] is:

[0080]

[0081] Then the pressure difference Δp between grid i and grid j is ij The flow rate q of the oil-water two-phase mixed fluid under (unit Pa) ij (Unit: m 3 / s)Flow meets:

[0082]

[0083] Δp ij =p i -p j -p cij ;

[0084] Among them, p i =p oi +ρ ow G JZ i , p oi is the pore pressure of grid i, Pa, ρ ow is the density of the mixed fluid, kg / m 3 , g is the acceleration due to gravity, 9.8m / s 2 , Z i is the vertical height of grid i, m; p j =p oj +ρ ow G JZ j , p oj is the pore pressure of grid j, Pa, Z j The vertical height of grid j, m; p cij is the equivalent capillary force of the reservoir grid, Pa; τ is the tortuosity, dimensionless; l ij is the grid side length, m; φ ij is the effective porosity, dimensionless; r cij is the critical radius, m; η eff is the effective viscosity of the mixed fluid, Pa·s.

[0085] S23, obtaining the effective viscosity and density of the oil-water two-phase fluid in the critical path between reservoir grids; including methods:

[0086] The effective viscosity η of the oil-water two-phase fluid in the critical path between reservoir grids is calculated according to the following formula eff :

[0087] η eff =B w μ w X ij +B o μ o (1-X ij )

[0088] Among them B w Represents the volume coefficient of water, dimensionless; B o Represents the volume coefficient of oil, dimensionless; μ w Indicates the viscosity of water, Pa·s; μ o Indicates the viscosity of the oil, Pa·s; X ij represents a dimensionless number related to the position of the oil-water interface, (0≤X ij ≤1), which is the location of the concave meniscus divided by the length of the entire frontage path;

[0089] The density of the oil-water two-phase fluid in the critical path between reservoir grids is calculated according to the following formula: ow =ρ w X ij +ρ o (1-X ij );

[0090] Among them, ρ w represents the density of water; ρ o Indicates the density of oil.

[0091] S24, based on the critical radius, the conductivity, effective viscosity and density are input into the mass conservation equation to construct the oil-water two-phase flow and pressure diffusion differential equations:

[0092]

[0093] Where i represents any number from 1 to N, and N represents the total number of grids. represents the conductivity between two adjacent grids i and j, m 3 / (Pa·s);Δp ij represents the pressure difference between grid i and grid j, Pa; ψ = φ c0i V bi C tow ; φ c0i represents the initial porosity of grid i, dimensionless; V bi represents the volume of grid i, m 3 ; Δt is the simulation time step, s; Δp i represents the change in pressure of grid i within Δt, Pa; Ctow (Pa -1 ) is the comprehensive compressibility coefficient of the oil and water phases. Since the compressibility of oil and water is roughly equal, to simplify the calculation, C tow The value of can be consistent with the compressibility coefficient of oil or water.

[0094] S25, numerical simulation of the oil-water two-phase flow and pressure diffusion differential equations is performed to obtain an oil-water two-phase numerical model.

[0095] Step 3: Solve the oil-water two-phase numerical model to obtain the oil-water mutual displacement simulation results; the mutual displacement simulation results include water-oil displacement and oil-water displacement. This step specifically includes the following methods:

[0096] S31, combined with the oil-water displacement process, in the process of numerical simulation of the oil-water two-phase flow and pressure diffusion differential equations, the interface movement process and distribution state are calculated according to the time step update, and the fluid conductivity of all grids is updated;

[0097] S32, solve the pressure and flow of different grids, and solve the global pressure field and oil-water flow result data at different times by the conjugate gradient method.

[0098] For the oil-water displacement process of this scheme, when water is used as the displacement phase to drive oil, the initial oil-water two-phase seepage model is completely filled with oil phase, which is produced as the displaced phase. The wetting angle of the oil-water two-phase seepage model is 150° (oil-wet), and the water phase is injected as the non-wetting phase as the displacement phase; when oil is used as the displaced phase, the wetting angle of the oil-water two-phase seepage model is 80° (water-wet), and the water phase is produced as the displaced phase. In the process of numerical simulation, it is necessary to update the calculation interface movement process and distribution state according to the time step, and update the fluid conductivity of all grids. The numerical simulation calculation process of oil-water two-phase flow can construct matrix equations at different times according to the law of conservation of mass. The simulation process described in this embodiment is to solve the pressure p of different grids. i With flow q ij , the global pressure field at different times can be solved by the conjugate gradient method. The two-phase seepage process continues until the entire equivalent model is filled with invading fluid (or the preset total simulation time is reached). The wellhead injection flow rate or injection pressure is kept unchanged throughout the process. It should be noted that when only water exists in the critical path between grid i and grid j, the critical path is marked as 1; when only oil exists in the critical path between grid i and grid j, the critical path is marked as 0; the number of critical paths with a mark value of 1 is counted and divided by the total number of grids to obtain the water drive sweep efficiency E in the water drive oil process. r By adopting the above steps and realizing fluid flow visualization through computer language, this scheme realizes water-to-oil simulation at the scale of a single well in the reservoir (e.g. Figure 3 As shown in Figure 2) and oil-water displacement simulation as shown in Figure 2 Figure 4The model is shown in Figure 1), where the injection well is in the middle, and different colors represent the flow field distribution of the displacement phase fluid. The black part is the displaced phase that has not been displaced. Figure 3 and Figure 4 , which can clearly reflect the differences in the displacement process caused by the differences in the properties of oil and water.

[0099] This embodiment combines the critical path seepage theory and takes into account the critical path, which is an advantageous seepage channel feature. It can directly reflect the dynamic changes of oil-water saturation during the simulation process, and there is no need to input the capillary pressure curve and the relative permeability curve. Through the above steps, a complete set of geological modeling-oil-water two-phase seepage theoretical model-numerical simulation solution process can be established, and the affected range, fluid front spatial position and movement state of the oil-water two-phase fluid can be directly reflected. Compared with the original black oil model, the simulation results are more reasonable.

[0100] The simulation technology of this embodiment calculates the pressure field distribution in the equivalent model through the implicit finite difference method, and then calculates the position of the two-phase fluid interface and the sweep efficiency. The reservoir model is simple and easy to use, and the number of grids, calculation speed and simulation accuracy can be improved through GPU accelerated computing technology.

[0101] This scheme combines the reservoir grid model with the critical path seepage theory, which can greatly improve the model scale while ensuring the modeling accuracy. It can also study the microscopic seepage mechanism from the reservoir scale while ensuring the accuracy of the simulation results.

[0102] Example 2

[0103] This embodiment provides an oil-water two-phase seepage model construction system based on critical path seepage theory, which is used to implement the oil-water two-phase seepage model construction method based on critical path described in Example 1; the system includes:

[0104] The first building module is used to establish a critical radius model of the oil-water two-phase fluid flow process based on nuclear magnetic logging technology and critical theory;

[0105] The second establishment module is used to establish an oil-water two-phase numerical model applicable to a single well scale of an oil reservoir based on the critical radius model under equivalent assumptions;

[0106] The solution module is used to solve the oil-water two-phase numerical model to obtain the oil-water mutual displacement simulation result.

[0107] Example 3

[0108] This embodiment provides a computer-readable medium on which a computer program is stored. The computer program is executed by a processor to implement the method for constructing an oil-water two-phase seepage model based on a critical path as described in Embodiment 1; specifically, the following steps are performed:

[0109] Step 1: Based on nuclear magnetic logging technology and critical path seepage theory, a critical radius model of the oil-water two-phase fluid flow process is established;

[0110] Step 2: Based on the critical radius model and under equivalent assumptions, an oil-water two-phase numerical model suitable for a single well scale of an oil reservoir is established;

[0111] Step 3: Solve the oil-water two-phase numerical model to obtain the oil-water mutual displacement simulation results.

[0112] The specific implementation methods 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 implementation method 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 an oil-water two-phase seepage model based on a critical path, characterized in that: include: Based on nuclear magnetic logging technology and critical path seepage theory, a critical radius model of oil-water two-phase fluid flow process is established; Based on the critical radius model and under equivalent assumptions, an oil-water two-phase numerical model suitable for a single well in an oil reservoir is established; The oil-water two-phase numerical model is solved to obtain the simulation result of the oil-water mutual phase displacement.

2. The method for constructing an oil-water two-phase seepage model based on a critical path according to claim 1, characterized in that: The method for constructing the critical path seepage radius model of the oil-water two-phase fluid flow process includes: Construct a well location grid model and calculate the permeability and porosity of each grid; Based on the critical path seepage theory, the actual rock pore throat characteristics and seepage channel characteristics are considered in the well location grid model to construct a critical radius model of the oil-water two-phase fluid flow process; the critical radius model includes: The critical radius r between grids i and j cij for: Among them, k ij represents the permeability between adjacent grids i and j, φ ij represents the porosity between adjacent grids i and j; τ represents the tortuosity; σ z Represents the coefficient of variation of rock heterogeneity.

3. The method for constructing an oil-water two-phase seepage model based on a critical path according to claim 2, characterized in that: The equivalent assumptions include: a. In the critical radius model, the critical path is the main channel for fluid seepage, and the pressure drop caused by fluid flow mainly occurs in the critical path; b, there is only one two-phase fluid interface between the oil and water two-phase fluids in the critical path; c, the two fluids flowing in the network are immiscible; d, Piston-like displacement occurs in the critical path.

4. The method for constructing an oil-water two-phase seepage model based on a critical path according to claim 3, characterized in that: Based on the critical radius model, under equivalent assumptions, an oil-water two-phase numerical model suitable for a single well in an oil reservoir is established; including method: Calculate the equivalent capillary force p of the reservoir grid caused by the oil-water interface in the critical path cij :p cij =2γcosθ / r cij ; Among them, r cij represents the critical radius of the critical path between grid i and grid j; γ represents the interfacial tension between oil and water phases; θ represents the wetting angle; Calculate the conductivity of the oil-water two-phase fluid between any two grids based on the critical path; Obtain the effective viscosity and density of the oil-water two-phase fluid in the critical path between reservoir grids; Based on the critical radius, the conductivity, effective viscosity and density are input into the mass conservation equation to construct the differential equations of oil-water two-phase flow and pressure diffusion; The oil-water two-phase numerical model is obtained by numerically simulating the oil-water two-phase flow and pressure diffusion differential equations.

5. The method for constructing an oil-water two-phase seepage model based on a critical path according to claim 4, characterized in that: Calculate the conductivity of the oil-water two-phase fluid between any two grids based on the critical path; Included methods: When oil and water coexist in the critical path between grid i and grid j, the conductivity ξ of the oil-water two-phase fluid in the critical path ij for: Then the pressure difference Δp between grid i and grid j is ij The flow rate q of the oil-water two-phase mixed fluid under ij Flow meets: Among them, p i =p oi +ρ ow G JZ i , p oi is the pore pressure of grid i, ρ ow is the density of the mixed fluid, Z i is the vertical height of grid i, g is the acceleration due to gravity, 9.8m / s 2 ;p j =p oj +ρ ow G JZ j , p oj is the pore pressure of grid j, Z j The vertical height of grid j, m; p cij The equivalent capillary force of the reservoir grid; τ is the tortuosity; l ij is the grid side length; φ cij is the effective porosity; r cij is the critical radius; η eff is the effective viscosity of the mixed fluid; p cij is the equivalent capillary force.

6. The method for constructing an oil-water two-phase seepage model based on a critical path according to claim 4, characterized in that: The step of obtaining the effective viscosity and density of the oil-water two-phase fluid in the critical path between the reservoir grids; include method: The effective viscosity η of the oil-water two-phase fluid in the critical path between reservoir grids is calculated according to the following formula eff : or eff =B w m w X ij +B o m o (1-X ij ) Among them B w represents the volume coefficient of water, dimensionless; B o Represents the volume coefficient of oil, dimensionless; μ w Indicates the viscosity of water, Pa·s; μ o Indicates the viscosity of the oil; X ij represents a dimensionless number related to the position of the oil-water interface, (0≤X ij ≤1), which is the location of the concave meniscus divided by the length of the entire critical path; The density of the oil-water two-phase fluid in the critical path between reservoir grids is calculated according to the following formula: ow =ρ w X ij +ρ o (1-X ij ); Among them, ρ w represents the density of water; ρ o Indicates the density of oil.

7. The method for constructing an oil-water two-phase seepage model based on a critical path according to claim 1, characterized in that: The oil-water two-phase flow and pressure diffusion differential equations include: Where i represents any number from 1 to N, and N represents the total number of grids. represents the conductivity between two adjacent grids i and j; Δp ij Represents the pressure difference between grid i and grid j; ψ=φ c0i V bi C tow ; φ c0i represents the initial porosity of grid i; V bi represents the volume of grid i; Δt is the simulation time step; Δp i represents the change value of the pressure of grid i within Δt; C tow is the comprehensive compressibility coefficient of the oil and water phases. Since the compressibility of oil and water is roughly equal, to simplify the calculation, C tow The value of is consistent with the compressibility coefficient of oil or water.

8. The method for constructing an oil-water two-phase seepage model based on a critical path according to claim 4, characterized in that: The method of solving the oil-water two-phase numerical model to obtain the oil-water two-phase displacement simulation result includes: Combined with the oil-water displacement process, in the process of numerical simulation of the oil-water two-phase flow and pressure diffusion differential equations, the interface movement process and distribution state are calculated according to the time step update, and the fluid conductivity of all grids is updated; The pressure and flow of different grids are solved, and the global pressure field and oil-water flow result data at different times are solved by the conjugate gradient method.

9. The oil-water two-phase seepage model construction system based on the critical path is characterized by: A method for constructing an oil-water two-phase seepage model based on a critical path according to any one of claims 1 to 8; the system comprises: The first building module is used to establish a critical radius model of the oil-water two-phase fluid flow process based on nuclear magnetic logging technology and critical path seepage theory; The second establishment module is used to establish an oil-water two-phase numerical model applicable to a single well scale of an oil reservoir based on the critical radius model under equivalent assumptions; The solution module is used to solve the oil-water two-phase numerical model to obtain the oil-water mutual displacement simulation result.

10. A computer readable medium having a computer program stored thereon, characterized in that: The computer program is executed by a processor to implement the method for constructing an oil-water two-phase seepage model based on a critical path as described in any one of claims 1 to 8.

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