A numerical simulation method and system for horizontal well cementing displacement based on the principle of relative motion

Abstract

The present invention discloses a numerical simulation method and system for horizontal well cementing displacement based on the principle of relative motion. The method comprises: establishing a three-dimensional annulus physical model for eccentric horizontal well cementing based on the wellbore structure of the horizontal well; performing structural grid division on the annulus physical model to form a cementing annulus grid model; determining the control equation and component model equations based on the cementing annulus grid model, and setting physical property parameters; setting the relative motion boundary conditions and initial conditions of the horizontal well based on the principle of relative motion; redefining the dynamic displacement interface and dynamic displacement efficiency, initiating steady-state flow field calculations, and determining the initial pressure and flow rate of the horizontal well; performing grid independence verification based on the displacement interface and dynamic displacement efficiency, initiating unsteady calculations, and simulating the cementing displacement process of a long horizontal well. The present invention solves the problems of low simulation efficiency and low sensitivity of parameter impact analysis in current numerical simulation methods.

Description

Technical Field

[0001] The present invention relates to the technical field of oil drilling and production, and in particular to a horizontal well cementing displacement numerical simulation method and system based on the principle of relative motion. Background Art

[0002] Horizontal well cementing is a critical step in oil and gas development. Its purpose is to ensure wellbore stability, prevent wellbore collapse, isolate fluids between different strata, and protect groundwater resources. During horizontal well cementing, different types of fluids, such as cement slurry, spacer fluid, and drilling fluid, are sequentially introduced into the well through displacement, forming multiple displacement interfaces. Each displacement interface significantly impacts cementing quality. Therefore, in-depth research on the formation process and patterns of displacement interfaces in the horizontal section of horizontal wells is of great significance.

[0003] Current methods for studying cementing displacement interfaces fall into three main categories: theoretical analysis of displacement interfaces, laboratory experimental methods, and numerical simulation methods. Theoretical analysis of displacement interfaces can effectively describe the dynamics of the cementing-displacement interface, but modeling and solving the interface are quite challenging. Laboratory experimental studies of displacement interfaces are limited by the length of the wellbore simulation, hindering the utility of this research method. Numerical simulation methods often use the VOF (Volume of Fluid) method to simulate the multiphase fluid displacement process during cementing. This method can study the effects of fluid density differences, viscosity, and injection rate. Simultaneously, the temporal evolution of the mud volume fraction at different axial sections of the wellbore is monitored to predict and analyze displacement efficiency and flow patterns. However, mixing occurs between the two phases of cementing displacement fluids, and this method cannot reflect the diffusion process between the two phases or the actual interface characteristics of the two phases. Furthermore, due to the long distances in actual horizontal wells, the simulation requires the generation of a large number of grids, which is computationally cumbersome and time-consuming, and cannot fully simulate the entire cementing process.

[0004] Therefore, it is necessary to propose a numerical simulation method for horizontal well displacement based on the principle of relative motion, which can study the cementing displacement problem of long horizontal sections with a shorter model and describe the fluid mixing phenomenon during displacement, providing an efficient numerical simulation means for the rapid analysis of horizontal well cementing displacement. Summary of the Invention

[0005] In view of this, the present invention provides a horizontal well cementing displacement numerical simulation method and system based on the principle of relative motion, which is used to solve the technical problems of low simulation efficiency and low sensitivity of parameter influence analysis in existing numerical simulation methods.

[0006] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0007] The present invention provides a numerical simulation method for horizontal well cementing displacement based on the principle of relative motion, comprising:

[0008] A three-dimensional annular physical model for eccentric horizontal well cementing is established based on the wellbore structure of the horizontal well;

[0009] Performing structural grid division on the annulus physical model to form a cementing annulus grid model;

[0010] Determining control equations and component model equations according to the cementing annulus grid model, and setting physical property parameters;

[0011] The relative motion boundary conditions and initial conditions of the horizontal well are set based on the relative motion principle;

[0012] The dynamic displacement interface and dynamic displacement efficiency were redefined, steady flow field calculations were initiated, and the initial pressure and flow rate of the horizontal well were determined;

[0013] The grid independence is verified based on the displacement interface and dynamic displacement efficiency, and the unsteady calculation is started to simulate the cementing displacement process of the long horizontal well.

[0014] Furthermore, the annulus physical model is divided into structural grids to form a cementing annulus grid model, including:

[0015] Using a preset finite element analysis tool, meshing the eccentric semi-annulus region of the annulus physical model along the axial direction, and performing mesh encryption processing on the portion close to the wall;

[0016] Using the surface mapping operation and setting the axial unit grid length, a regular hexahedral three-dimensional structure grid is generated;

[0017] The surface grid is mapped out through the three-dimensional structural grid, and each boundary is named to obtain an annular grid model.

[0018] Furthermore, the control equations are used to simulate the process of displacement flow of two-phase fluids, including the continuity equation and the turbulence equation;

[0019] The component model equation is used to simulate the mixing phenomenon between the cementing displacement two-phase fluid and describe the mass diffusion between the fluids, including laminar mass diffusion and turbulent mass diffusion equations;

[0020] The physical parameters are used to describe the deformation and flow properties of the slurry under the action of external forces, including the rheological parameters of the cement slurry and the spacer fluid.

[0021] Furthermore, the relative motion boundary conditions for setting the horizontal well based on the relative motion principle include:

[0022] Based on the principle of relative motion, the displacement process is simulated using moving wall boundary conditions. The moving wall inlet and outlet conditions are set, and the initial mass fraction distributions of the two fluids are set.

[0023] Furthermore, setting the initial conditions of the horizontal well based on the principle of relative motion includes: determining the distribution of flow field physical quantities in the eccentric annulus of the horizontal well at the start of displacement.

[0024] Furthermore, the redefinition of the dynamic replacement interface and dynamic replacement efficiency includes:

[0025] The displacement front and rear positions are determined based on the eccentricity effect, gravity, and mass diffusion. The difference between the front and rear positions is used as the dynamic displacement interface length, which is used to analyze the growth of slurry volume under the influence of different parameters during the displacement process.

[0026] According to the dynamic displacement interface length, the ratio of the displacement fluid trailing edge volume to the displacement fluid leading edge swept volume is taken as the dynamic displacement efficiency, and the interface length and displacement efficiency in the displacement process are coupled together.

[0027] Furthermore, grid independence verification based on the replacement interface and dynamic replacement efficiency includes:

[0028] The radial and circumferential grids are kept unchanged, the circumferential flow grid size is changed, and the grid independence is verified using the displacement interface length and displacement efficiency under different grids as evaluation indicators.

[0029] Furthermore, the initiation of unsteady calculation to simulate the cementing displacement process of the long horizontal well includes:

[0030] The pressure and flow rate of each preset time step are numerically calculated. If the local residual value of the current time step meets the convergence criterion, the calculation is completed and the dynamic displacement interface length and displacement efficiency are updated. The numerical calculation of the next time step is performed until the calculation of the last time step is completed.

[0031] Furthermore, the method further comprises: extracting the displacement interface length and displacement efficiency under different parameter values ​​during the sensitivity analysis of different parameters.

[0032] The present invention also provides a horizontal well cementing displacement numerical simulation system based on the principle of relative motion, comprising:

[0033] A 3D annulus model building module is used to build a 3D annulus physical model for eccentric horizontal well cementing based on the wellbore structure of the horizontal well;

[0034] A grid division module is used to perform structural grid division on the annulus physical model to form a cementing annulus grid model;

[0035] A parameter setting module, for determining the control equation and the component model equation according to the cementing annulus grid model, and setting the physical property parameters;

[0036] Condition setting module, used to set the relative motion boundary conditions and initial conditions of the horizontal well based on the relative motion principle;

[0037] A custom setting module is used to redefine the dynamic displacement interface and dynamic displacement efficiency, start the steady flow field calculation, and determine the initial pressure and flow rate of the horizontal well;

[0038] The simulation output module is used to verify the grid independence according to the displacement interface and the dynamic displacement efficiency, start the unsteady calculation, and simulate the long horizontal well cementing displacement process.

[0039] Compared with existing technologies, the numerical simulation method for horizontal well cementing displacement based on the principle of relative motion provided by this invention first establishes a three-dimensional eccentric annulus physical model based on the eccentric and axisymmetric flow characteristics during horizontal well cementing, reducing the number of grid cells by half and improving computational efficiency. Second, a component model is used to capture the mixing of fluids during the displacement process, more realistically simulating the fluid motion process during cementing displacement. Third, a moving solid wall boundary is set based on relative motion, allowing the use of short models to simulate the displacement process of horizontal well sections of varying lengths, significantly improving computational efficiency. Finally, the dynamic displacement efficiency is redefined. Furthermore, compared to traditional volumetric displacement efficiency, this invention is more conducive to parameter sensitivity analysis, providing a highly effective technical approach for studying horizontal well cementing displacement processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 A flow chart of an embodiment of a numerical simulation method for horizontal well cementing displacement based on the relative motion principle provided by the present invention;

[0041] Figure 2 A schematic diagram of a three-dimensional annulus physical model for eccentric horizontal well cementing provided by the present invention;

[0042] Figure 3 A schematic diagram of the cementing annulus grid model provided by the present invention;

[0043] Figure 4 Schematic diagram of mass diffusion distribution in the transverse and longitudinal sections of the annulus provided by the present invention;

[0044] Figure 5 A schematic diagram of the displacement process of the fixed wall boundary condition provided by the present invention;

[0045] Figure 6 A schematic diagram of the displacement process of the moving wall boundary condition provided by the present invention;

[0046] Figure 7 A schematic diagram of the displacement position and interface length provided by the present invention;

[0047] Figure 8 A schematic diagram comparing the parameter sensitivity of the traditional displacement efficiency and the dynamic displacement efficiency provided by the present invention;

[0048] Figure 9 The cloud diagram of cement slurry mass fraction under different displacement rates and the corresponding schematic diagram of interface length and displacement efficiency change curves provided by the present invention;

[0049] Figure 10 This is a structural schematic diagram of an embodiment of a horizontal well cementing displacement numerical simulation system based on the relative motion principle provided by the present invention. DETAILED DESCRIPTION

[0050] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, and are not used to limit the scope of the present invention.

[0051] The present invention provides a horizontal well cementing displacement numerical simulation method and system based on the principle of relative motion, which are described below.

[0052] A specific embodiment of the present invention discloses a numerical simulation method for horizontal well cementing displacement based on the principle of relative motion. Figure 1 FIG. 1 is a flow chart of the numerical simulation method for horizontal well cementing displacement based on the relative motion principle, as shown in FIG. Figure 1 As shown, the method includes:

[0053] Step S101: establishing a three-dimensional annulus physical model for eccentric horizontal well cementing based on the wellbore structure of the horizontal well;

[0054] Step S102: performing structural grid division on the annulus physical model to form a cementing annulus grid model;

[0055] Step S103: determining the control equation and component model equation according to the cementing annulus grid model, and setting the physical property parameters;

[0056] Step S104: setting relative motion boundary conditions and initial conditions of the horizontal well based on the relative motion principle;

[0057] Step S105: redefine the dynamic displacement interface and dynamic displacement efficiency, start the steady flow field calculation, and determine the initial pressure and flow rate of the horizontal well;

[0058] Step S106: Grid independence verification is performed based on the displacement interface and dynamic displacement efficiency, unsteady calculation is started, and the cementing displacement process of the long horizontal well is simulated.

[0059] The method of this embodiment first establishes a three-dimensional eccentric annulus physical model based on the eccentric and axisymmetric flow characteristics during horizontal well cementing, reducing the number of grid cells by half and improving computational efficiency. Second, a component model is used to capture the mixing of fluids during the displacement process, more realistically simulating the fluid motion during cementing displacement. Third, a moving solid wall boundary is established based on relative motion, enabling the use of a short model to simulate the displacement process of horizontal well sections of varying lengths, significantly improving computational efficiency. Finally, the dynamic displacement efficiency is redefined. Furthermore, compared to traditional volumetric displacement efficiency, this method is more conducive to parameter sensitivity analysis, providing a highly effective technical approach for studying the displacement process during horizontal well cementing.

[0060] Since cementing displacement generally occurs in the annular space between the casing and the wellbore wall, the casing will generally be eccentric downward due to gravity. At the same time, the annular flow has an axisymmetric characteristic. Therefore, it is necessary to establish a physical model of the eccentric horizontal well cementing annulus.

[0061] As a specific example, in step S101, considering the common wellbore structure, the wellbore outer diameter is 215.9mm, and 139.7mm casing is used for cementing. In addition, an 8% wellbore expansion rate is taken into account, so the horizontal well outer diameter is 233.2mm, the horizontal section annulus model length is designed to be 50m, and the annulus displacement flow direction is perpendicular to the gravity direction. A three-dimensional horizontal well eccentric annulus cementing displacement physical model is established in Solidwork software, as shown in the following figure: Figure 2 As shown, it is shortened by a ratio of 25:1 in the flow direction to facilitate observation of its model features.

[0062] As a specific embodiment, in step S102, first use Hypermesh to read the 3D horizontal well eccentric annulus cementing displacement physical model file, then perform regular grid division on the axial eccentric semi-annulus, and at the same time perform grid encryption near the wall, use surface mapping operation and set the axial unit grid length to generate a regular hexahedral 3D structure grid, then delete all surface grids and map the surface grids through the 3D volume grid, and name each boundary to generate a 3D grid file, such as Figure 3 shown.

[0063] Using an axially eccentric semi-annulus for regular meshing effectively controls mesh quality and accuracy, improving the efficiency and accuracy of numerical simulations. Meshing areas close to the wall more accurately capture flow field variations and enhance the accuracy of simulation results. The resulting 3D mesh file can be directly used in subsequent numerical simulations, streamlining workflows and increasing efficiency.

[0064] As a specific embodiment, in step S103, first, a three-dimensional eccentric annulus grid file is read using CFD numerical simulation software (Ansys Fluent), and then the grid size is set. Since it is imported from different grid software, it is necessary to perform size scaling with a scaling factor of 0.001 to complete grid size homogenization;

[0065] Secondly, select the control equation and component model equation, and set the physical property parameters. Specifically:

[0066] (1) Selection of control equations

[0067] Since the essence of horizontal well cementing displacement is the flow process of liquid-liquid two-phase fluid in the long annular space, the two-phase fluid displacement flow process and law satisfy the fluid mechanics equations, and the controlling equations include the continuity equation and the momentum equation.

[0068] The continuity equation in inertial coordinates can be expressed as:

[0069]

[0070] Where ρ is the fluid density, V is the fluid velocity, t is the flow time, and ▽ is the gradient operator.

[0071] The momentum equation is:

[0072]

[0073] Where, is the acceleration due to gravity, div is the divergence operator, and T is the stress tensor.

[0074] (2) Selection of component model

[0075] Since the VOF model is generally used in the numerical simulation of cementing displacement, it cannot reflect the material diffusion process of the two phases and the real interface characteristics of the two phases of fluid. However, there is mixing between the two phases of fluid in cementing displacement, such as Figure 4 As shown, it is necessary to select the component model and the laminar diffusion equation to describe the mass diffusion problem between fluids:

[0076]

[0077] Mass Diffusion in Laminar Flow:

[0078]

[0079] Where: Y i is the volume fraction of each component, dimensionless; D i,m is the diffusion coefficient between the components.

[0080] (3) Fluid physical property parameter setting

[0081] In this example, cement slurry is used to replace the spacer fluid. The rheological properties of cementing slurry refer to the deformation and flow properties of the slurry under external forces. The vast majority of fluids involved in cementing are non-Newtonian fluids. During the cementing process, the shear rate of the fluid in the cementing operation is limited. Since the power law model accurately describes the rheological properties of the slurry, it is used throughout this example for calculations. It can be expressed as:

[0082]

[0083] Where τ is the shear stress, Pa; K is the consistency coefficient, Pa.s n ; n is the rheological index, dimensionless.

[0084] At the same time, considering the flow state changes during the cementing process, it is necessary to calculate the fluid Reynolds number. The calculation formula of the annulus Reynolds number Re is:

[0085]

[0086] Where, D1 is the outer diameter of the annulus, m; D2 is the inner diameter of the annulus, m; V is the average velocity of the annulus, m / s.

[0087] It should be noted that in previous numerical simulation studies of eccentric annulus displacement in horizontal wells, stationary wall boundary conditions were often used. Under such conditions, the fluid interface quickly reaches the outlet position of the eccentric annulus flow field in the horizontal well, and the observable displacement process is very short. Figure 5 This figure shows the process of cement slurry (red) displacing the spacer fluid (blue) under fixed wall conditions. It can be found that the displacement interface quickly develops to the outlet boundary position. Observing the development process of the displacement interface requires a fairly long flow field model. In this case, the numerical simulation of long horizontal sections requires a physical model of equal length, resulting in a sharp increase in the number of grids and increased computational cost.

[0088] In order to solve the above problem, as a preferred embodiment, in step S104, relative motion boundary and other boundary conditions are set, that is, based on the principle of relative motion, the solid walls inside and outside the eccentric annulus are changed to motion wall boundary conditions, and other boundary conditions are set. The specific setting method is as follows:

[0089] (1) Setting of moving wall boundary conditions

[0090] Assuming that the wall of the eccentric annulus of a horizontal well moves in the opposite direction at an average velocity, the fluid in the eccentric annulus of a horizontal well can be regarded as a movement with a zero cross-sectional flow integral. Figure 6As shown, using a moving wall boundary condition allows the interface between the two phases to remain in the center of the flow field and expand outwards, rather than quickly reaching the outlet boundary. This advantage is that a relatively short flow field model can be used to simulate long displacement interfaces, and the development of the displacement interface over time can be captured, which solves the current problem of low computational efficiency in numerical simulations of long horizontal sections.

[0091] (2) Setting of entry and exit boundary conditions

[0092] In order to be consistent with the moving solid wall boundary conditions, the velocity at the inlet position needs to satisfy the flow integral of zero. There are generally two ways to set boundary conditions: the first is to calculate the velocity distribution of the eccentric annulus of the horizontal well under the single-phase conditions of the two-phase fluid, subtract the average velocity from the velocity distribution, and directly assign it to the inlet boundary; the other method is to directly assign the boundary condition velocity value to zero. Regardless of which initial condition is used, the flow field will have a velocity distribution formation process at the initial moment. At the beginning of the displacement, there is a certain error between the velocity distribution and the actual situation. This embodiment uses the second method to set the inlet boundary conditions.

[0093] The outlet boundary adopts the mass outlet condition, that is, the physical quantity at the outflow boundary position is derived from the physical quantity at the adjacent position inside the region through interpolation and other methods, and is corrected by the mass conservation equation, which has little effect on the upstream flow.

[0094] (3) Initial condition setting

[0095] Initial conditions refer to the initial state of the flow field at the initial moment, which should be satisfied by the fluid motion. Specifically, the values ​​of various physical quantities in the flow field at that initial moment must be determined. At the onset of displacement in the eccentric annulus of a horizontal well, the distribution patterns of physical quantities in the flow field must be determined, particularly the distribution patterns of two-phase fluid in the eccentric annulus of the horizontal well. Initially, the annulus is filled with both the displacing fluid and the displaced fluid in a 60%:40% ratio, with the displacing fluid near the inlet and the displaced fluid near the outlet.

[0096] In some embodiments, before starting the replacement calculation, step S105 requires redefining the dynamic replacement interface and dynamic replacement efficiency and compiling a user-defined function (UDF). Specifically:

[0097] (1) Define the length of the dynamic replacement interface

[0098] When two-phase fluid flows in an eccentric annulus, it is affected by the coupling of multiple factors such as gravity and buoyancy caused by density difference. The velocity characteristics of the wide and narrow sides are different. Under different displacement parameter conditions, different displacement interface characteristics will appear.

[0099] The displacement interface length can be used to comprehensively evaluate the influence of various factors such as the eccentric effect of the eccentric annulus, gravity, mass diffusion, etc. In this invention, the displacement front position Z is defined as 20% of the cement slurry volume fraction. f 80% is the replacement rear edge position Z b ,like Figure 7 As shown in Figure 2, since the positions of the front and rear edges of the displacement change over time, the difference between the two is defined as the dynamic displacement interface length L. i This length characterizes the mixed volume of different slurries during the displacement process and can be used to analyze the growth of mixed slurry volume under the influence of different displacement parameters. Because the component model in the software only displays mass fractions, a user-defined function (UDF) is required to extract the leading and trailing edge positions. This function is written in C and compiled within the software.

[0100] (2) Define dynamic replacement efficiency

[0101] During cementing and displacement, the degree of displacement of one fluid by another is often characterized by displacement efficiency, symbolized by η. Displacement efficiency is generally categorized into volumetric displacement efficiency and cross-sectional displacement efficiency. Currently, volumetric displacement efficiency is often used to express displacement effectiveness in engineering and numerical simulation analysis. Volumetric displacement efficiency η is generally defined as the ratio of the cement slurry in the annular space to the total volume of the annular space:

[0102]

[0103] When η=1, the displacement fluid completely replaces the displaced fluid, and the displacement efficiency is high. When η<1, the displacement fluid partially replaces the displaced fluid, and the lower the value, the lower the displacement efficiency.

[0104] The disadvantages of this displacement efficiency method are: when analyzing parameter impacts, before the displacement fluid front reaches the outlet, the displacement efficiency slope under various parameters is the inverse of the injection volume versus time, which is a consistent straight line. The impact of various parameters can only be displayed as the difference in the time it takes for the displacement fluid to reach the outlet, which cannot accurately describe the impact of different parameters on the displacement efficiency during the displacement process. Furthermore, the simulated displacement time is short, which cannot reflect the actual displacement efficiency in long horizontal sections.

[0105] To address this problem, the present invention redefines the dynamic displacement efficiency η based on the dynamic displacement interface length. d , which is the ratio of the displacement fluid trailing edge volume to the displacement fluid front edge swept volume. Under this definition, the interface length and displacement efficiency in the displacement process are coupled together. Figure 8As shown in the figure, as the displacement interface stabilizes, the effects of different parameters on displacement efficiency become apparent in less than 20 seconds, compared to the original 30 seconds or more. This saves a significant amount of computational time for parameter sensitivity analysis in numerical simulations. Furthermore, combined with relative motion simulation methods, the displacement time can be further increased, simulating the displacement process over longer well sections, achieving a displacement efficiency closer to the actual displacement efficiency.

[0106] (3) Without starting the moving wall boundary condition, the steady flow field calculation is performed to obtain the stable initial pressure and flow rate.

[0107] As a specific embodiment, in step S106, the grid independence verification is first performed based on the definition of step S105, wherein the radial and circumferential grids remain unchanged, and the circumferential flow grid size is changed. The grid independence verification is performed using the displacement interface length and displacement efficiency under different grids as evaluation indicators, and a grid of appropriate size is selected.

[0108] Secondly, edit and mount the relevant UDF, start the moving wall, and set the time step Δt to meet the CFL number criterion. where Δx is the unit grid length of axial flow and v is the average displacement velocity.

[0109] Finally, CFD software is used to calculate the pressure, flow rate, and other parameters for each time step. The calculation is completed when the local residual value reaches the convergence criterion. When the calculation of a time step is completed, the dynamic displacement interface length and dynamic displacement efficiency are updated to calculate the values ​​of the next time step until the calculation of the final time step is completed.

[0110] In addition, during the sensitivity analysis of different parameters, the displacement interface length and displacement efficiency under different parameter values ​​are extracted. Figure 9 As shown in the figure, the cement slurry mass fraction cloud diagrams and the corresponding interface length and dynamic displacement efficiency curves at five different displacement rates (i.e., injection rates) are used as examples. To maintain a single-factor analysis, the injection rate was kept constant. As the injection rate increases, the interface length increases with the pumping rate, while the displacement efficiency gradually decreases. However, as the pumping rate continues to increase, the difference in displacement efficiency between different injection rates gradually narrows.

[0111] like Figure 10 As shown, an embodiment of the present invention further provides a horizontal well cementing displacement numerical simulation system 1000 based on the principle of relative motion, comprising:

[0112] A three-dimensional annulus model building module 1001 is used to build a three-dimensional annulus physical model for eccentric horizontal well cementing based on the wellbore structure of the horizontal well;

[0113] A grid division module 1002 is used to perform structural grid division on the annulus physical model to form a cementing annulus grid model;

[0114] Parameter setting module 1003, for determining control equations and component model equations according to the cementing annulus grid model, and setting physical property parameters;

[0115] Condition setting module 1004, used to set relative motion boundary conditions and initial conditions of the horizontal well based on the relative motion principle;

[0116] The custom setting module 1005 is used to redefine the dynamic displacement interface and dynamic displacement efficiency, start the steady flow field calculation, and determine the initial pressure and flow rate of the horizontal well;

[0117] The simulation output module 1006 is used to verify the grid independence based on the displacement interface and dynamic displacement efficiency, start unsteady calculation, and simulate the long horizontal well cementing displacement process.

[0118] The present invention provides a numerical simulation method and system for horizontal well cementing displacement based on the principle of relative motion. First, a three-dimensional eccentric annulus physical model is established based on the eccentric and axisymmetric flow characteristics during horizontal well cementing, saving half the grid count and improving computational efficiency. Second, a component model is used to capture the mixing of fluids during the displacement process, more realistically simulating the fluid motion process during cementing displacement. Third, a moving solid wall boundary is set based on relative motion, allowing the use of short models to simulate the displacement process of horizontal well sections of varying lengths, significantly improving computational efficiency. Finally, the dynamic displacement efficiency is redefined. Furthermore, compared to traditional volumetric displacement efficiency, the present invention is more conducive to parameter sensitivity analysis, providing a highly effective technical approach for studying horizontal well cementing displacement processes.

[0119] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed by the present invention should be covered by the scope of protection of the present invention.

Claims

1. A numerical simulation method for horizontal well cementing displacement based on the principle of relative motion, characterized in that: include: A three-dimensional annular physical model for eccentric horizontal well cementing is established based on the wellbore structure of the horizontal well; Performing structural grid division on the annulus physical model to form a cementing annulus grid model; Determining control equations and component model equations according to the cementing annulus grid model, and setting physical property parameters; The relative motion boundary conditions and initial conditions of the horizontal well are set based on the relative motion principle; The dynamic displacement interface and dynamic displacement efficiency were redefined, steady flow field calculations were initiated, and the initial pressure and flow rate of the horizontal well were determined; The redefinition of the dynamic replacement interface and dynamic replacement efficiency includes: The displacement front and rear positions are determined based on the eccentricity effect, gravity, and mass diffusion. The difference between the front and rear positions is used as the dynamic displacement interface length, which is used to analyze the growth of slurry volume under the influence of different parameters during the displacement process. Based on the dynamic displacement interface length, the ratio of the displacement fluid trailing volume to the displacement fluid leading edge swept volume is used as the dynamic displacement efficiency, and the interface length and displacement efficiency during the displacement process are coupled together. A grid independence verification is performed based on the displacement interface and dynamic displacement efficiency, and unsteady calculations are initiated to simulate the cementing displacement process in a long horizontal well.

2. The horizontal well cementing displacement numerical simulation method based on the relative motion principle according to claim 1 is characterized in that: Performing structural grid division on the annulus physical model to form a cementing annulus grid model includes: Using a preset finite element analysis tool, meshing the eccentric semi-annulus region of the annulus physical model along the axial direction, and performing mesh encryption processing on the portion close to the wall; Using the surface mapping operation and setting the axial unit grid length, a regular hexahedral three-dimensional structure grid is generated; The surface grid is mapped out through the three-dimensional structural grid, and each boundary is named to obtain an annular grid model.

3. The horizontal well cementing displacement numerical simulation method based on the relative motion principle according to claim 1 is characterized in that: The control equations are used to simulate the process of displacement flow of two-phase fluid, including continuity equation and turbulence equation; The component model equation is used to simulate the mixing phenomenon between the cementing displacement two-phase fluid and describe the mass diffusion between the fluids, including laminar mass diffusion and turbulent mass diffusion equations; The physical parameters are used to describe the deformation and flow properties of the slurry under the action of external forces, including the rheological parameters of the cement slurry and the spacer fluid.

4. The horizontal well cementing displacement numerical simulation method based on the relative motion principle according to claim 1 is characterized in that: The relative motion boundary conditions for setting the horizontal well based on the relative motion principle include: Based on the principle of relative motion, the displacement process is simulated using moving wall boundary conditions. The moving wall inlet and outlet conditions are set, and the initial mass fraction distributions of the two fluids are set.

5. The horizontal well cementing displacement numerical simulation method based on the relative motion principle according to claim 1 is characterized in that: The setting of the initial conditions of the horizontal well based on the relative motion principle includes: determining the distribution of flow field physical quantities in the eccentric annulus of the horizontal well at the start of displacement.

6. The horizontal well cementing displacement numerical simulation method based on the relative motion principle according to claim 1 is characterized in that: Verification of grid independence based on the displacement interface and dynamic displacement efficiency includes: The radial and circumferential grids are kept unchanged, the circumferential flow grid size is changed, and the grid independence is verified using the displacement interface length and displacement efficiency under different grids as evaluation indicators.

7. The horizontal well cementing displacement numerical simulation method based on the relative motion principle according to claim 1 is characterized in that: The starting of the unsteady calculation to simulate the cementing displacement process of the long horizontal well includes: The pressure and flow rate of each preset time step are numerically calculated. If the local residual value of the current time step meets the convergence criterion, the calculation is completed and the dynamic displacement interface length and displacement efficiency are updated. The numerical calculation of the next time step is performed until the calculation of the last time step is completed.

8. The horizontal well cementing displacement numerical simulation method based on the relative motion principle according to claim 1 is characterized in that: Also includes: During the sensitivity analysis of different parameters, the displacement interface length and displacement efficiency under different parameter values ​​were extracted.

9. A horizontal well cementing displacement numerical simulation system based on the principle of relative motion, characterized in that: include: A 3D annulus model building module is used to build a 3D annulus physical model for eccentric horizontal well cementing based on the wellbore structure of the horizontal well; A grid division module is used to perform structural grid division on the annulus physical model to form a cementing annulus grid model; A parameter setting module, for determining the control equation and the component model equation according to the cementing annulus grid model, and setting the physical property parameters; Condition setting module, used to set the relative motion boundary conditions and initial conditions of the horizontal well based on the relative motion principle; A custom setting module is used to redefine the dynamic displacement interface and dynamic displacement efficiency, start the steady flow field calculation, and determine the initial pressure and flow rate of the horizontal well; The redefinition of the dynamic displacement interface and dynamic displacement efficiency includes: determining the displacement front and rear edge positions based on the eccentricity effect, gravity, and mass diffusion, taking the difference between the front and rear edge positions as the dynamic displacement interface length, and using this difference to analyze the growth of the slurry volume under the influence of different parameters during the displacement process; taking the ratio of the displacement fluid rear edge volume to the displacement fluid front edge swept volume as the dynamic displacement efficiency based on the dynamic displacement interface length, and coupling the interface length and displacement efficiency during the displacement process; The simulation output module is used to verify the grid independence according to the displacement interface and the dynamic displacement efficiency, start the unsteady calculation, and simulate the long horizontal well cementing displacement process.

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