Non-Newtonian two-phase fluid displacement simulation method and system based on nuclear magnetic resonance logging

Abstract

The present invention discloses a non-Newtonian two-phase fluid displacement simulation method and system based on nuclear magnetic resonance logging, relating to the technical field of oil and gas field development simulation. Based on traditional non-Newtonian two-phase flow simulation technology, the simulation method is improved. Under the critical radius model and equivalent assumptions, the microscopic characteristics of fluid seepage in rocks are effectively considered, and an Ellis non-Newtonian fluid-oil two-phase numerical model suitable for a single well in an oil reservoir is established. The model can dynamically adapt to changes in reservoir pressure while ensuring the scale and accuracy of the model. On the other hand, when calculating the effective viscosity of the Ellis non-Newtonian fluid-oil two-phase fluid, the effective radius and reservoir pressure changes of the Ellis non-Newtonian fluid-oil two-phase fluid in the critical path are taken into account, so that the Ellis non-Newtonian fluid-oil two-phase numerical model can dynamically adapt to changes in reservoir pressure, thereby obtaining more accurate simulation results.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas field development simulation, and in particular to a non-Newtonian two-phase fluid displacement simulation method and system based on nuclear magnetic resonance logging. Background Art

[0002] During oil and gas reservoir development, non-Newtonian two-phase fluid displacement technology, due to its unique rheological properties such as shear thinning and viscoelasticity, can effectively improve sweep efficiency during the displacement process, particularly in heterogeneous reservoirs. Non-Newtonian fluids can enhance oil recovery by reducing fingering, optimizing fluid distribution, and blocking high-permeability pathways, while also adapting to the complex conditions of low-permeability reservoirs. This technology is widely used in enhanced oil recovery (EOR) techniques such as polymer flooding, foam flooding, and gel flooding, and is an important means of improving oil and gas reservoir development efficiency. Therefore, studying the flow patterns and displacement mechanisms of non-Newtonian two-phase fluid displacement and establishing accurate simulation models are of great significance for optimizing oil recovery strategies.

[0003] Traditional non-Newtonian two-phase flow models and simulations are developed based on black oil models and face multiple defects. First, traditional non-Newtonian two-phase flow models usually rely on ideal and simplified assumptions, such as homogeneous reservoirs and stable flow conditions. When applied to highly heterogeneous reservoirs, large-scale grids cannot effectively handle the changes in the viscoelasticity of non-Newtonian fluids in small-scale pore throat spaces, which limits the model's ability to express in detail and makes the model no longer applicable under complex geological conditions and dynamic production environments. Secondly, the rheological properties of non-Newtonian fluids are complex and changeable, and shear thinning has a significant impact on fluid flow behavior. Traditional models use reservoir macro-porosity and permeability to characterize changes in rheological properties, which is different from the actual micro-effective pore space in which non-Newtonian fluids flow, resulting in simulation results that are inconsistent with actual conditions. Summary of the Invention

[0004] The technical problem to be solved by the present invention is that traditional non-Newtonian two-phase flow models cannot effectively handle the changes in the viscoelasticity of non-Newtonian fluids in small-scale pore throat spaces, making it difficult to simulate the influence of shear thinning on the flow behavior of non-Newtonian fluids, resulting in simulation results that are inconsistent with actual conditions. The present invention aims to provide a non-Newtonian two-phase fluid displacement simulation method and system based on nuclear magnetic resonance logging. Based on traditional non-Newtonian two-phase flow simulation technology, the simulation method is improved. Under the critical radius model and equivalent assumptions, an Ellis non-Newtonian fluid-oil two-phase numerical model suitable for a single well in an oil reservoir is established, which can dynamically adapt to changes in reservoir pressure. Based on nuclear magnetic resonance logging technology and critical path seepage theory, the microscopic characteristics of fluid seepage in rocks are effectively considered to construct a more refined Ellis non-Newtonian fluid-oil two-phase numerical model. At the same time, the Ellis non-Newtonian fluid-oil two-phase numerical model constructed by this solution can dynamically adapt to changes in reservoir pressure and accurately simulate the influence of shear thinning on the flow behavior of non-Newtonian fluids, while ensuring the scale and accuracy of the model.

[0005] The present invention is achieved through the following technical solutions:

[0006] This solution provides a non-Newtonian two-phase fluid displacement simulation method based on nuclear magnetic resonance logging, including:

[0007] Based on nuclear magnetic logging technology and critical path seepage theory, the critical radius model of Ellis non-Newtonian fluid-oil two-phase flow is established;

[0008] Based on the critical radius model and under equivalent assumptions, an Ellis non-Newtonian fluid-oil two-phase numerical model applicable to a single well in an oil reservoir is established; the Ellis non-Newtonian fluid-oil two-phase numerical model can dynamically adapt to changes in reservoir pressure;

[0009] The Ellis non-Newtonian fluid-oil two-phase numerical model is solved to obtain simulation results of the Ellis non-Newtonian fluid-oil two-phase displacement process.

[0010] Working principle of this scheme: Traditional non-Newtonian two-phase flow models cannot effectively deal with the changes in the viscoelasticity of non-Newtonian fluids in small-scale pore throat spaces, and it is difficult to simulate the influence of shear thinning on the flow behavior of non-Newtonian fluids, resulting in simulation results that are inconsistent with actual conditions; the purpose of the present invention is to provide a non-Newtonian two-phase fluid displacement simulation method and system based on nuclear magnetic resonance logging. Based on the traditional non-Newtonian two-phase flow simulation technology, the simulation method is improved. Under the critical radius model and equivalent assumptions, the microscopic characteristics of fluid seepage in rocks are effectively considered, and an Ellis non-Newtonian fluid-oil two-phase numerical model suitable for a single well in the reservoir that can dynamically adapt to changes in reservoir pressure is established, while ensuring the scale and accuracy of the model; on the other hand, when calculating the effective viscosity of the Ellis non-Newtonian fluid-oil two-phase fluid, the effective radius and reservoir pressure changes of the Ellis non-Newtonian fluid-oil two-phase fluid in the critical path are taken into account, so that the Ellis non-Newtonian fluid-oil two-phase numerical model can dynamically adapt to changes in reservoir pressure, thereby obtaining more accurate simulation results.

[0011] A further optimization scheme is to establish a critical radius model of Ellis non-Newtonian fluid-oil two-phase fluid based on nuclear magnetic resonance logging technology and critical path seepage theory; including the following methods:

[0012] Construct a well location grid model and calculate the permeability and porosity of each grid;

[0013] 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 the Ellis critical radius model for non-Newtonian fluid-oil two-phase flow:

[0014] The critical radius r in the critical path between any grid i and grid j in the well location grid model cij for:

[0015]

[0016] Among them, k ij represents the harmonic permeability between adjacent grids i and j, φ ij represents the average porosity between adjacent grids i and j; τ is the tortuosity; σ z is the coefficient of variation of rock heterogeneity; w and h represent the first parameter and the second parameter related to the reservoir rock type, respectively.

[0017] A further optimization solution is that the equivalent assumptions include:

[0018] a. In the critical radius model, the critical path is the main channel for fluid seepage. The pressure drop of fluid flow mainly occurs in the critical path, and the contribution of other paths to the overall pressure drop can be ignored.

[0019] b. In the critical path, there is only one stable two-phase fluid interface between the Ellis non-Newtonian fluid and the oil two-phase fluid, and the interface morphology does not change significantly with time;

[0020] c. The two fluids flowing in the network are immiscible with each other and maintain their respective physical and chemical properties during the flow process;

[0021] d. The fluid flow in the critical path is mainly piston-type displacement, that is, the front fluid completely displaces the rear fluid, and there is no obvious diffusion or mixing phenomenon at the interface.

[0022] A further optimization scheme is to establish an Ellis non-Newtonian fluid-oil two-phase numerical model applicable to a single well scale of an oil reservoir based on the critical radius model under equivalent assumptions; including the following methods:

[0023] Calculate the equivalent capillary force on the reservoir grid caused by the Ellis non-Newtonian fluid-oil two-phase interface within the critical path, as well as the effective fluid density and comprehensive compressibility of the Ellis non-Newtonian fluid-oil two-phase fluid;

[0024] Obtaining an effective radius of the Ellis non-Newtonian fluid-oil two-phase fluid in the critical path, and calculating an effective viscosity of the Ellis non-Newtonian fluid-oil two-phase fluid based on the effective radius and taking into account reservoir pressure changes;

[0025] Based on the mass conservation equation, the Ellis non-Newtonian fluid-oil two-phase flow and pressure diffusion differential equations are established. The equivalent capillary force, effective fluid density, comprehensive compressibility coefficient and effective viscosity of the reservoir grid are substituted into the Ellis non-Newtonian fluid-oil two-phase flow and pressure diffusion differential equations to obtain the Ellis non-Newtonian fluid-oil two-phase numerical model.

[0026] A further optimization scheme is to calculate the equivalent capillary force of the reservoir grid caused by the Ellis non-Newtonian fluid-oil two-phase interface in the critical path, as well as the effective fluid density and comprehensive compressibility coefficient of the Ellis non-Newtonian fluid-oil two-phase fluid; including the following methods:

[0027] The equivalent capillary force p of the reservoir grid caused by the Ellis non-Newtonian fluid-oil two-phase interface in the critical path is calculated based on the following formula: cij :

[0028] p cij =2γcosθ / r cij ;

[0029] Among them, r cij represents the critical radius of the critical path between grid i and grid j; γ represents the interfacial tension between the Ellis non-Newtonian fluid and the oil phase; θ represents the wetting angle;

[0030] The effective fluid density ρ of the Ellis non-Newtonian fluid-oil two-phase in the critical path is calculated based on the following formula: ow :

[0031] ρ ow =ρ w X ij +ρ o (1-X ij )

[0032] Among them, ρ w represents the density of oil; ρ o represents the density of the Ellis non-Newtonian fluid, X ij represents the dimensionless number related to the position of the Ellis non-Newtonian fluid-oil two-phase interface, (0≤X ij ≤1), which is the position of the concave liquid surface divided by the length of the entire critical path; g represents the acceleration due to gravity;

[0033] The comprehensive compressibility coefficient C of Ellis non-Newtonian fluid-oil two-phase fluid is calculated based on the following formula tow :

[0034] C tow =C w X ij +C o (1-X ij )

[0035] Among them, C w Indicates the compressibility coefficient of oil; C o represents the compressibility of the Ellis non-Newtonian fluid.

[0036] A further optimization scheme is to obtain the effective radius of the Ellis non-Newtonian fluid-oil two-phase fluid in the critical path, consider the reservoir pressure change and calculate the effective viscosity of the Ellis non-Newtonian fluid-oil two-phase fluid based on the effective radius; including the following method:

[0037] Get the critical radius r between grid i and grid j cij ;

[0038] According to the critical radius r cij Japanese style eff =r cij ·φ cij The effective radius r of the Ellis non-Newtonian fluid-oil two-phase fluid in the critical path is obtained eff ; where φ cij represents the effective porosity between adjacent grids i and j;

[0039] The effective viscosity η of the Ellis non-Newtonian fluid-oil two-phase fluid is calculated according to the following formula eff :

[0040]

[0041] Among them, B w Indicates the volume coefficient of oil; μ w Indicates the viscosity of the oil; B o represents the Ellis non-Newtonian volume coefficient; μ c represents the initial viscosity of the Ellis non-Newtonian fluid; represents the Ellis non-Newtonian fluid viscosity μ s =μ c / 2; α is the empirical constant related to the shear rheology of Ellis fluid; r eff represents the effective radius in the critical path; l ij represents the length of the critical path between grid i and grid j; Δp ij =p i -p j -p cij , p i =p oi +ρ ow ZGar i , p oi is the pressure at grid i, ρ ow is the effective fluid density of the Ellis non-Newtonian fluid-oil two-phase, g is the acceleration due to gravity, Z i represents the height of the center point of grid i; p j =p oj +ρ ow ZGar j , p oj is the pressure at grid j, Z j represents the height of the center point of grid j; p cij is the equivalent capillary force on the reservoir grid caused by the Ellis non-Newtonian fluid-oil two-phase interface in the critical path.

[0042] A further optimization solution is that the two-phase flow and pressure diffusion differential equations include:

[0043]

[0044] Where Δp ij =p i -p j -p cij , p i =p oi +ρ ow ZGar i , p oi is the pore pressure of grid i, ρ ow is the effective fluid density of the Ellis non-Newtonian fluid-oil two-phase.

[0045] A further optimization scheme is that solving the non-Newtonian fluid two-phase numerical model to obtain a non-Newtonian two-phase fluid displacement simulation result includes the following process:

[0046] When Ellis non-Newtonian fluid is used as the displacement phase to displace oil, the initial pore network of the well grid model is completely filled with oil, which is produced as the displaced phase. The wetting angle θ is 150°, and the Ellis non-Newtonian fluid is injected as the non-wetting phase as the displacement phase.

[0047] During the numerical simulation, the movement process and distribution state of the Ellis non-Newtonian fluid-oil two-phase interface are calculated according to the time step update, and the equivalent capillary force p of all grids is updated. cij , effective fluid density ρ ow , comprehensive compression coefficient C tow and effective viscosity η eff .

[0048] A further optimization scheme is to traverse each grid in the well location grid model and write the nonlinear equations satisfying the Ellis non-Newtonian fluid-oil two-phase flow and pressure diffusion differential equations into a matrix equation of the form MP=B, where M represents the coefficient matrix related to the two-phase flow, and P represents the pressure to be solved p i The variable vector composed of , B represents the right-hand side term related to the sink flow;

[0049] Solve the matrix equation MP=B according to the Gauss-Seidel method:

[0050] The superscript n represents the current time step, and the superscript n+1 represents the next time step. is the pressure of grid i at the current moment, and the pressure of grid i at the next time step Calculate as follows:

[0051]

[0052] Where N is the total number of grids; M ii is the diagonal element corresponding to grid i in matrix M; B i is the element in vector B corresponding to grid i; M ij is the off-diagonal element corresponding to the grid j adjacent to the grid i in the matrix M; represents the pressure of grid j at the current time step; represents the pressure of grid j at the next time step;

[0053] Set the convergence condition when When , the iteration stops and the pressure result is output;

[0054] The global pressure field and Ellis non-Newtonian fluid-oil flow result data are solved for different grids at different time steps until the set termination condition is reached (the ratio of oil flow to Ellis non-Newtonian fluid flow is less than 0.01%), ending the calculation of the entire process.

[0055] This solution also provides a non-Newtonian two-phase fluid displacement simulation system based on nuclear magnetic logging, which is used to implement the above-mentioned non-Newtonian two-phase fluid displacement simulation method based on nuclear magnetic logging. The system includes:

[0056] The first module is used to establish the critical radius model of Ellis non-Newtonian fluid-oil two-phase fluid based on nuclear magnetic resonance logging technology and critical path seepage theory;

[0057] The second establishment module is used to establish an Ellis non-Newtonian fluid-oil two-phase numerical model applicable to a single well scale of an oil reservoir based on the critical radius model under equivalent assumptions; the Ellis non-Newtonian fluid-oil two-phase numerical model can dynamically adapt to changes in reservoir pressure;

[0058] The solution module is used to solve the Ellis non-Newtonian fluid-oil two-phase numerical model to obtain the simulation results of the Ellis non-Newtonian fluid-oil two-phase displacement process.

[0059] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0060] 1. The non-Newtonian two-phase fluid displacement simulation method and system based on nuclear magnetic resonance logging provided by the present invention are based on traditional non-Newtonian two-phase flow simulation technology and make improvements on the simulation method. Under the critical radius model and equivalent assumptions, the microscopic characteristics of fluid seepage in rocks are effectively considered to establish an Ellis non-Newtonian fluid-oil two-phase numerical model suitable for a single well in an oil reservoir that can dynamically adapt to changes in reservoir pressure, while ensuring the scale and accuracy of the model. On the other hand, when calculating the effective viscosity of the Ellis non-Newtonian fluid-oil two-phase fluid, the effective radius of the Ellis non-Newtonian fluid-oil two-phase fluid in the critical path and the reservoir pressure changes are taken into account, so that the Ellis non-Newtonian fluid-oil two-phase numerical model can dynamically adapt to changes in reservoir pressure, thereby obtaining more accurate simulation results.

[0061] 2. The non-Newtonian two-phase fluid displacement simulation method and system based on nuclear magnetic resonance logging provided by the present invention combines the critical path and critical radius to calculate the equivalent capillary force, effective fluid density and comprehensive compressibility coefficient of the reservoir grid caused by the Ellis non-Newtonian fluid-oil two-phase interface, thereby accurately characterizing the impact of interfacial tension and wettability changes on the displacement process, while enhancing the description of the two-phase fluid interface behavior in the microscopic effective pore space of actual reservoir rocks.

[0062] 3. The non-Newtonian two-phase fluid displacement simulation method and system based on nuclear magnetic resonance logging provided by the present invention improves the rheological model of non-Newtonian fluids through the Ellis effective viscosity calculation method of non-Newtonian fluid-oil two-phase fluids, fully considers the influence of shear thinning on fluid flow behavior, and enables the final Ellis non-Newtonian fluid-oil two-phase numerical model to dynamically adapt to changes in reservoir pressure conditions; in addition, when calculating the effective viscosity of the Ellis non-Newtonian fluid-oil two-phase fluid, the effective radius in the critical radius model is used. Compared with the original black oil model and pore network model, the Ellis non-Newtonian fluid-oil two-phase numerical model constructed based on effective porosity can better reflect the migration process of fluids in actual reservoirs. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] 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 examples. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be considered as limiting the scope. A person of ordinary skill in the art can also derive other relevant drawings based on these drawings without inventive effort. In the drawings:

[0064] Figure 1 This is a flow chart of the non-Newtonian two-phase fluid displacement simulation method based on nuclear magnetic resonance logging;

[0065] Figure 2 Schematic diagram of the position of the interface between the two phases when the Ellis non-Newtonian fluid and oil coexist on the critical path;

[0066] Figure 3 This is a schematic diagram of the structure of the non-Newtonian two-phase fluid displacement simulation system based on nuclear magnetic logging;

[0067] Figure 4 Schematic diagram of the simulation of non-Newtonian fluid oil two-phase displacement at the scale of a single well in the reservoir. DETAILED DESCRIPTION

[0068] 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 examples and drawings. The exemplary embodiments of the present invention and their descriptions are only used to explain the present invention and are not intended to limit the present invention.

[0069] Example 1

[0070] This embodiment provides a non-Newtonian two-phase fluid displacement simulation method based on nuclear magnetic logging, such as Figure 1 As shown, including:

[0071] Step 1: Based on nuclear magnetic resonance logging technology and critical path seepage theory, a critical radius model of Ellis non-Newtonian fluid-oil two-phase fluid is established; this step specifically includes the following methods:

[0072] S11, construct a well location grid model and calculate the permeability and porosity of each grid;

[0073] S12, based on the critical path seepage theory, considers the actual rock pore throat characteristics and seepage channel characteristics in the well grid model, and constructs the Ellis critical radius model for non-Newtonian fluid-oil two-phase flow:

[0074] The critical radius r between grid i and grid j cij for:

[0075]

[0076] 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 is the tortuosity; σ z is the coefficient of variation of rock heterogeneity; w and h represent the first parameter and the second parameter related to the reservoir rock type, respectively. In this embodiment, taking tight sandstone as an example, the value range of w is [-0.31, -0.88]; the value range of h is [0.5, 0.8].

[0077] This approach uses nuclear magnetic resonance (NMR) logging technology to obtain key static geological parameters such as reservoir porosity and permeability, and can use these parameters to inversely characterize the flow paths in the reservoir rock microstructure. By extending NMR logging data from static characterization to the critical radius of the critical path of the dynamic displacement process, geological modeling of small-scale pore throat spaces and fluid flow simulation in microscopic effective pore spaces can be achieved.

[0078] Step 2: Based on the critical radius model and under equivalent assumptions, an Ellis non-Newtonian fluid-oil two-phase numerical model applicable to a single well in the reservoir is established; the Ellis non-Newtonian fluid-oil two-phase numerical model can dynamically adapt to changes in reservoir pressure. In this step, the equivalent assumptions include:

[0079] a. In the critical radius model, the critical path is the main channel for fluid seepage. The pressure drop of fluid flow mainly occurs in the critical path, and the contribution of other paths to the overall pressure drop can be ignored.

[0080] b. In the critical path, there is only one stable two-phase fluid interface between the Ellis non-Newtonian fluid and the oil two-phase fluid, and the interface morphology does not change significantly with time;

[0081] c. The two fluids flowing in the network are immiscible with each other and maintain their respective physical and chemical properties during the flow process;

[0082] d. The fluid flow in the critical path is mainly piston-type displacement, that is, the front fluid completely displaces the rear fluid, and there is no obvious diffusion or mixing phenomenon at the interface.

[0083] Step 2 specifically includes the following methods:

[0084] S21, calculate the equivalent capillary force of the reservoir grid caused by the Ellis non-Newtonian fluid-oil two-phase interface in the critical path, as well as the effective fluid density and comprehensive compressibility of the Ellis non-Newtonian fluid-oil two-phase fluid; specifically, the equivalent capillary force p of the reservoir grid caused by the Ellis non-Newtonian fluid-oil two-phase interface in the critical path is calculated based on the following formula: cij :

[0085] p cij =2γcosθ / r cij ;

[0086] Among them, r cij represents the critical radius of the critical path between grid i and grid j; γ represents the interfacial tension between the Ellis non-Newtonian fluid and the oil phase; θ represents the wetting angle, which ranges from 0° to 180°; the position of the interface between the Ellis non-Newtonian fluid and the oil phase when the two phases coexist on the critical path is as follows: Figure 2 As shown;

[0087] The effective fluid density ρ of the Ellis non-Newtonian fluid-oil two-phase in the critical path is calculated based on the following formula: ow :

[0088] ρ ow =ρ w X ij +ρ o (1-X ij )

[0089] Among them, ρ w represents the density of oil; ρ o represents the density of the Ellis non-Newtonian fluid, X ij represents the dimensionless number related to the position of the Ellis non-Newtonian fluid-oil two-phase interface, (0≤X ij ≤1), which is the location of the concave liquid surface divided by the length of the entire critical path; g represents the acceleration due to gravity, 9.8m / s 2 ;

[0090] The comprehensive compressibility coefficient C of Ellis non-Newtonian fluid-oil two-phase fluid is calculated based on the following formula tow :

[0091] C tow =C w X ij +C o (1-X ij )

[0092] Among them, C w Indicates the oil compressibility, Pa -1 ; C o represents the compressibility of the Ellis non-Newtonian fluid, Pa -1 .

[0093] Compared with the traditional black oil model, this method combines the critical path and critical radius to calculate the equivalent capillary force, effective fluid density and comprehensive compressibility coefficient of the reservoir grid caused by the Ellis non-Newtonian fluid-oil two-phase interface, achieving accurate characterization of the impact of interfacial tension and wettability changes on the displacement process, while enhancing the description of the two-phase fluid interface behavior in the microscopic effective pore space of actual reservoir rocks.

[0094] S22, obtaining the effective radius of the Ellis non-Newtonian fluid-oil two-phase fluid in the critical path, and calculating the effective viscosity of the Ellis non-Newtonian fluid-oil two-phase fluid based on the effective radius taking into account the reservoir pressure change; including the method:

[0095] Get the critical radius r between grid i and grid j cij ;

[0096] According to the critical radius r cij Japanese style eff =r cij ·φ cij The effective radius r of the Ellis non-Newtonian fluid-oil two-phase fluid in the critical path is obtained eff ; where φ cij represents the effective porosity between adjacent grids i and j;

[0097] The effective viscosity of the Ellis non-Newtonian fluid-oil two-phase fluid is calculated according to the following formula:

[0098]

[0099] Among them, B w Indicates the volume coefficient of oil; μ w Indicates the viscosity of the oil, Pa·s; B o represents the Ellis non-Newtonian volume coefficient; μ c represents the initial viscosity of the Ellis non-Newtonian fluid, Pa·s; represents the Ellis non-Newtonian fluid viscosity μ s =μ c Shear stress at / 2, Pa -1 ; α is the empirical constant related to the shear rheology of Ellis fluid, dimensionless; r eff represents the effective radius in the critical path; l ij represents the length of the critical path between grid i and grid j; Δp ij =pi -p j -p cij , p i =p oi +ρ ow ZGar i , p oi is the pressure at grid i, ρ ow is the effective fluid density of the Ellis non-Newtonian fluid-oil two-phase, g is the acceleration due to gravity, Z i represents the height of the center point of grid i; p j =p oj +ρ ow ZGar j , p oj is the pressure at grid j, Z j represents the height of the center point of grid j; p cij is the equivalent capillary force on the reservoir grid caused by the Ellis non-Newtonian fluid-oil two-phase interface in the critical path.

[0100] This proposal improves the rheological model of non-Newtonian fluids by using the aforementioned Ellis method for calculating the effective viscosity of non-Newtonian fluid-oil two-phase fluids. This method fully considers the influence of shear thinning on fluid flow behavior, enabling the resulting Ellis non-Newtonian fluid-oil two-phase numerical model to dynamically adapt to changes in reservoir pressure conditions. Furthermore, the effective radius in the critical radius model is used when calculating the effective viscosity of the Ellis non-Newtonian fluid-oil two-phase fluid. Compared with traditional models, the effective porosity better reflects the fluid migration process in the actual reservoir.

[0101] S23, based on the mass conservation equation, establish the Ellis non-Newtonian fluid-oil two-phase flow and pressure diffusion differential equations, substitute the reservoir grid equivalent capillary force, effective fluid density, comprehensive compressibility, and effective viscosity into the Ellis non-Newtonian fluid-oil two-phase flow and pressure diffusion differential equations to obtain the Ellis non-Newtonian fluid-oil two-phase numerical model. The two-phase flow and pressure diffusion differential equations include:

[0102]

[0103] Where Δp ij =p i -p j -p cij , p i =p oi +ρ ow ZGar i , p oi is the pore pressure of grid i, ρ ow is the effective fluid density of the Ellis non-Newtonian fluid-oil two-phase.

[0104] Step three, solving the Ellis non-Newtonian fluid-oil two-phase numerical model to obtain the simulation results of the Ellis non-Newtonian fluid-oil two-phase displacement process.

[0105] This step specifically includes the following process: when Ellis non-Newtonian fluid is used as the displacement phase to drive oil, the initial pore network of the well grid model is completely filled with oil and produced as the displaced phase, the wetting angle θ is set to 150°, and the Ellis non-Newtonian fluid is injected as the non-wetting phase as the displacement phase;

[0106] During the numerical simulation, the movement process and distribution state of the Ellis non-Newtonian fluid-oil two-phase interface are calculated according to the time step update, and the equivalent capillary force p of all grids is updated. cij , effective fluid density ρ ow , comprehensive compression coefficient C tow and effective viscosity η eff .

[0107] The said solving the non-Newtonian fluid two-phase numerical model to obtain the non-Newtonian two-phase fluid displacement simulation result also includes a method:

[0108] Traversing each grid in the well location grid model, the nonlinear equations satisfying the Ellis non-Newtonian fluid-oil two-phase flow and pressure diffusion differential equations are written as a matrix equation in the form of MP=B, where M represents the coefficient matrix related to the two-phase flow, and P represents the pressure to be solved p i The variable vector composed of , B represents the right-hand side term related to the sink flow;

[0109] Solve the matrix equation MP=B according to the Gauss-Seidel method:

[0110] The superscript n represents the current time step, and the superscript n+1 represents the next time step. is the pressure of grid i at the current moment, and the pressure of grid i at the next time step Calculate as follows:

[0111]

[0112] Where N is the total number of grids; M ii is the diagonal element corresponding to grid i in matrix M; B i is the element in vector B corresponding to grid i; M ij is the off-diagonal element corresponding to the grid j adjacent to the grid i in the matrix M; represents the pressure of grid j at the current time step; represents the pressure of grid j at the next time step;

[0113] Set the convergence condition when When , the iteration stops and the pressure result is output;

[0114] The global pressure field and Ellis non-Newtonian fluid-oil flow result data are solved for different grids at different time steps until the set termination condition is reached (the ratio of oil flow to Ellis non-Newtonian fluid flow is less than 0.01%), ending the calculation of the entire process.

[0115] Through the above steps, a complete geological modeling process—Ellis's non-Newtonian fluid-oil two-phase flow theory model—and numerical simulation can be established. This process directly reflects the sweep range, spatial position, and movement of the fluid front of the Ellis non-Newtonian fluid-oil two-phase flow. The simulation technology in this embodiment uses implicit finite difference methods to calculate the pressure field distribution in the equivalent model, 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 GPU-accelerated computing technology can be used to increase the number of grids, calculation speed, and simulation accuracy.

[0116] Example 2

[0117] This embodiment provides a non-Newtonian two-phase fluid displacement simulation system based on nuclear magnetic logging, which is used to implement the non-Newtonian two-phase fluid displacement simulation method based on nuclear magnetic logging described in Example 1, such as Figure 3 As shown, the system includes:

[0118] The first module is used to establish the critical radius model of Ellis non-Newtonian fluid-oil two-phase fluid based on nuclear magnetic resonance logging technology and critical path seepage theory;

[0119] The second establishment module is used to establish an Ellis non-Newtonian fluid-oil two-phase numerical model applicable to a single well scale of an oil reservoir based on the critical radius model under equivalent assumptions; the Ellis non-Newtonian fluid-oil two-phase numerical model can dynamically adapt to changes in reservoir pressure;

[0120] The solution module is used to solve the Ellis non-Newtonian fluid-oil two-phase numerical model to obtain the simulation results of the Ellis non-Newtonian fluid-oil two-phase displacement process.

[0121] Example 3

[0122] This embodiment provides a computer-readable medium having a computer program stored thereon. The computer program is executed by a processor to implement the non-Newtonian two-phase fluid displacement simulation method based on nuclear magnetic resonance logging as described in Example 1. Specifically, the following steps are performed:

[0123] Step 1: Based on nuclear magnetic resonance logging technology and critical path seepage theory, the critical radius model of Ellis non-Newtonian fluid-oil two-phase fluid is established;

[0124] Step 2: Based on the critical radius model and under equivalent assumptions, an Ellis non-Newtonian fluid-oil two-phase numerical model applicable to a single well in the reservoir is established; the Ellis non-Newtonian fluid-oil two-phase numerical model can dynamically adapt to changes in reservoir pressure;

[0125] Step three, solving the Ellis non-Newtonian fluid-oil two-phase numerical model to obtain the simulation results of the Ellis non-Newtonian fluid-oil two-phase displacement process.

[0126] The schematic diagram of the oil flooding non-Newtonian fluid simulation at the single well scale of the reservoir obtained according to this scheme is as follows Figure 4 As shown, the injection well is located in the center of the model. Different colors represent the flow field distribution of the displacing oil phase, and the black portion represents the undisplaced non-Newtonian fluid phase. This solution establishes a complete workflow for underground non-Newtonian fluids: geological modeling, seepage theory modeling, numerical simulation, and visualization. This workflow directly reflects the fluid impact range, spatial location, and movement of the fluid front.

[0127] 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 non-Newtonian two-phase fluid displacement simulation method based on nuclear magnetic resonance logging, characterized in that: include: Based on nuclear magnetic logging technology and critical path seepage theory, the critical radius model of Ellis non-Newtonian fluid-oil two-phase flow is established; The method includes: constructing a well grid model and calculating the permeability and porosity of each grid; based on the critical path seepage theory, considering the actual rock pore throat characteristics and seepage channel characteristics in the well grid model, constructing the Ellis non-Newtonian fluid-oil two-phase fluid critical radius model: the critical radius r in the critical path between any grid i and grid j in the well grid model cij for: Among them, k ij represents the harmonic permeability between adjacent grids i and j, φ ij represents the average porosity between adjacent grids i and j; τ is the tortuosity; σ z is the coefficient of variation of rock heterogeneity; w and h represent the first and second parameters related to reservoir rock type, respectively; Based on the critical radius model and under equivalent assumptions, an Ellis non-Newtonian fluid-oil two-phase numerical model applicable to a single well in an oil reservoir is established; the Ellis non-Newtonian fluid-oil two-phase numerical model can dynamically adapt to changes in reservoir pressure; The Ellis non-Newtonian fluid-oil two-phase numerical model is solved to obtain simulation results of the Ellis non-Newtonian fluid-oil two-phase displacement process.

2. The non-Newtonian two-phase fluid displacement simulation method based on nuclear magnetic logging according to claim 1, characterized in that: The equivalent assumptions include: a. In the critical radius model, the critical path is the channel for fluid seepage. The pressure drop of the fluid flow occurs concentrated in the critical path, and the contribution of other paths to the overall pressure drop can be ignored. b. In the critical path, there is only one stable two-phase fluid interface between the Ellis non-Newtonian fluid and the oil two-phase fluid, and the interface morphology does not change significantly with time; c. The two fluids flowing in the network are immiscible with each other and maintain their respective physical and chemical properties during the flow process; d. The fluid flow in the critical path is mainly piston-type displacement, that is, the front fluid completely displaces the rear fluid, and there is no obvious diffusion or mixing phenomenon at the interface.

3. The non-Newtonian two-phase fluid displacement simulation method based on nuclear magnetic logging according to claim 1, characterized in that: Based on the critical radius model and under equivalent assumptions, an Ellis non-Newtonian fluid-oil two-phase numerical model applicable to a single well scale of an oil reservoir is established; method: Calculate the equivalent capillary force on the reservoir grid caused by the Ellis non-Newtonian fluid-oil two-phase interface within the critical path, as well as the effective fluid density and comprehensive compressibility of the Ellis non-Newtonian fluid-oil two-phase fluid; Obtaining an effective radius of the Ellis non-Newtonian fluid-oil two-phase fluid in the critical path, and calculating an effective viscosity of the Ellis non-Newtonian fluid-oil two-phase fluid based on the effective radius and taking into account reservoir pressure changes; Based on the mass conservation equation, the Ellis non-Newtonian fluid-oil two-phase flow and pressure diffusion differential equations are established. The equivalent capillary force, effective fluid density, comprehensive compressibility coefficient and effective viscosity of the reservoir grid are substituted into the Ellis non-Newtonian fluid-oil two-phase flow and pressure diffusion differential equations to obtain the Ellis non-Newtonian fluid-oil two-phase numerical model.

4. The non-Newtonian two-phase fluid displacement simulation method based on nuclear magnetic logging according to claim 3, characterized in that: The calculation includes the equivalent capillary force of the reservoir grid caused by the Ellis non-Newtonian fluid-oil two-phase interface in the critical path, and the effective fluid density and comprehensive compressibility coefficient of the Ellis non-Newtonian fluid-oil two-phase fluid; Includes methods: The equivalent capillary force p of the reservoir grid caused by the Ellis non-Newtonian fluid-oil two-phase interface in the critical path is calculated based on the following formula: 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 the Ellis non-Newtonian fluid and the oil phase; θ represents the wetting angle; The effective fluid density ρ of the Ellis non-Newtonian fluid-oil two-phase in the critical path is calculated based on the following formula: ow : r ow =ρ w X ij +r o (1-X ij ) Among them, ρ w represents the density of oil; ρ o represents the density of the Ellis non-Newtonian fluid, X ij represents a dimensionless number related to the position of the Ellis non-Newtonian fluid-oil two-phase interface, 0≤X ij ≤1, that is, the location of the concave liquid surface divided by the length of the entire critical path; g represents the acceleration due to gravity; The comprehensive compressibility coefficient C of Ellis non-Newtonian fluid-oil two-phase fluid is calculated based on the following formula tow : C tow =C w X ij +C o (1-X ij ) Among them, C w Indicates the compressibility coefficient of oil; C o represents the compressibility of the Ellis non-Newtonian fluid.

5. The non-Newtonian two-phase fluid displacement simulation method based on nuclear magnetic logging according to claim 3, characterized in that: The effective radius of the Ellis non-Newtonian fluid-oil two-phase fluid in the critical path is obtained, and the effective viscosity of the Ellis non-Newtonian fluid-oil two-phase fluid is calculated based on the effective radius taking into account the reservoir pressure change; Includes methods: Get the critical radius r between grid i and grid j cij ; According to the critical radius r cij Japanese style eff =r cij ·φ cij The effective radius r of the Ellis non-Newtonian fluid-oil two-phase fluid in the critical path is obtained eff ; where φ cij represents the effective porosity between adjacent grids i and j; The effective viscosity η of the Ellis non-Newtonian fluid-oil two-phase fluid is calculated according to the following formula eff : Among them, B w Indicates the volume coefficient of oil; μ w Indicates the viscosity of the oil; B o represents the Ellis non-Newtonian volume coefficient; μ c represents the initial viscosity of the Ellis non-Newtonian fluid; represents the Ellis non-Newtonian fluid viscosity μ s =μ c / 2; α is the empirical constant related to the shear rheology of Ellis fluid; r eff represents the effective radius in the critical path; l ij represents the length of the critical path between grid i and grid j; Δp ij =p i -p j -p cij , p i =p oi +ρowgZ i , p oi is the pressure at grid i, ρow is the effective fluid density of the Ellis non-Newtonian fluid-oil two-phase, g is the acceleration due to gravity, Z i represents the height of the center point of grid i; p j =p oj +ρ ow ZGar j , p oj is the pressure at grid j, Z j represents the height of the center point of grid j; p cij is the equivalent capillary force on the reservoir grid caused by the Ellis non-Newtonian fluid-oil two-phase interface in the critical path.

6. The non-Newtonian two-phase fluid displacement simulation method based on nuclear magnetic logging according to claim 5, characterized in that: The two-phase flow and pressure diffusion differential equations include: Where Δp ij =p i -p j -p cij , p i =p oi +ρ ow ZGar i , p oi is the pore pressure of grid i, ρ ow is the effective fluid density of the Ellis non-Newtonian fluid-oil two-phase.

7. The non-Newtonian two-phase fluid displacement simulation method based on nuclear magnetic logging according to claim 1, characterized in that: Solve the Ellis non-Newtonian fluid-oil two-phase numerical model to obtain the simulation results of the Ellis non-Newtonian fluid-oil two-phase displacement process, including the following process: When Ellis non-Newtonian fluid is used as the displacement phase to displace oil, the initial pore network of the well grid model is completely filled with oil, which is produced as the displaced phase. The wetting angle θ is 150°, and the Ellis non-Newtonian fluid is injected as the non-wetting phase as the displacement phase. During the numerical simulation, the movement process and distribution state of the Ellis non-Newtonian fluid-oil two-phase interface are calculated according to the time step update, and the equivalent capillary force p of all grids is updated. cij , effective fluid density ρ ow , comprehensive compression coefficient C tow and effective viscosity η eff .

8. The non-Newtonian two-phase fluid displacement simulation method based on nuclear magnetic logging according to claim 7, characterized in that: Solving the Ellis non-Newtonian fluid-oil two-phase numerical model to obtain simulation results of the Ellis non-Newtonian fluid-oil two-phase displacement process, also includes methods: Traversing each grid in the well location grid model, the nonlinear equations satisfying the Ellis non-Newtonian fluid-oil two-phase flow and pressure diffusion differential equations are written as a matrix equation in the form of MP=B, where M represents the coefficient matrix related to the two-phase flow, and P represents the pressure to be solved p i The variable vector composed of , B represents the right-hand side term related to the sink flow; Solve the matrix equation MP=B according to the Gauss-Seidel method: Let n represent the current time step and n+1 represent the next time step, then is the pressure of grid i at the current moment, and the pressure of grid i at the next time step Calculate as follows: Where N is the total number of grids; M ii is the diagonal element corresponding to grid i in matrix M; B i is the element in vector B corresponding to grid i; M ij is the off-diagonal element corresponding to the grid j adjacent to the grid i in the matrix M; represents the pressure of grid j at the current time step; represents the pressure of grid j at the next time step; Set the convergence condition when When , the iteration stops and the pressure result is output; Solve the global pressure field and Ellis non-Newtonian fluid-oil flow result data for different grids at different time steps until the set termination condition is reached and the calculation of the entire process is terminated.

9. A non-Newtonian two-phase fluid displacement simulation system based on nuclear magnetic logging, characterized by: A system for implementing the non-Newtonian two-phase fluid displacement simulation method based on nuclear magnetic logging according to any one of claims 1 to 8, comprising: The first module is used to establish the critical radius model of Ellis non-Newtonian fluid-oil two-phase fluid based on nuclear magnetic resonance logging technology and critical path seepage theory; The second establishment module is used to establish an Ellis non-Newtonian fluid-oil two-phase numerical model applicable to a single well scale of an oil reservoir based on the critical radius model under equivalent assumptions; the Ellis non-Newtonian fluid-oil two-phase numerical model can dynamically adapt to changes in reservoir pressure; The solution module is used to solve the Ellis non-Newtonian fluid-oil two-phase numerical model to obtain the simulation results of the Ellis non-Newtonian fluid-oil two-phase displacement process.

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