Mathematical model-based acid etching wall surface form prediction method

Abstract

The invention provides an acid etching wall surface form prediction method based on a mathematical model, and relates to the technical field of petroleum engineering, and the method comprises the steps: carrying out the three-dimensional modeling of a rock plate crack surface through a three-dimensional laser scanner and fluid finite element software, and obtaining a crack space model; based on the fracture space model, performing coupling solution on a pressure field and a velocity field of the fracture space model to obtain fluid flow dynamic parameter distribution in the fracture; the dynamic parameter distribution of fluid flow in the fracture is input into the constructed acid rock reaction mathematical model, and the corrosion mass of each wall face node is obtained; obtaining the corresponding corrosion depth of the wall surface by utilizing the corrosion quality of each wall surface node; and removing the influence of the corrosion depth corresponding to the wall surface by using the crack space model to obtain the shape of the wall surface after acid etching, and completing the prediction of the shape of the acid-etched wall surface. According to the invention, the problem that etching form research cannot be carried out on the same wall surface under different acid liquid injection conditions is solved.

Description

Technical Field

[0001] The present invention relates to the field of petroleum engineering technology, and in particular to a method for predicting the morphology of acid-etched wall surfaces based on a mathematical model. Background Art

[0002] At present, the market for the development of carbonate oil and gas has been oriented towards deep development. Deep carbonate oil and gas resources account for about 70% of the world's total oil and gas resources. To this day, deep carbonate oil and gas are still an indispensable part of energy supply. However, the deep burial of the reservoir, strong heterogeneity, high ambient temperature, and high closure pressure are common problems faced by the development of deep carbonate reservoirs today. After acid fracturing of deep carbonate reservoirs, there are often problems such as weak conductivity of acid-etched fractures and short duration of production increase effects. The main reason is that the morphology of the acid-etched wall restricts the oil and gas channels after the fracture is closed, which may lead to restricted oil and gas flow. Therefore, the morphology of the wall of the acid-etched fracture is one of the determining factors of the conductivity of the acid-etched fracture, and it is also an important parameter for predicting and judging the effect of acid fracturing.

[0003] At present, the main method for studying the surface morphology of acid-etched cracks is to obtain the acid-etched rock surface through acid flow experiments, and then use laser scanning to digitize it, so as to conduct relevant research on acid-etched cracks under different conditions. However, due to the strong heterogeneity of carbonate rocks, the initial fracture surfaces obtained by each experimental sample are very different, and the traditional research method cannot study the etching characteristics of different acid injection conditions on the same wall surface. Summary of the invention

[0004] In view of the above-mentioned deficiencies in the prior art, the present invention provides a method for predicting the acid-etched wall morphology based on a mathematical model, which solves the problem that it is impossible to conduct etching morphology research on the same wall surface under different acid injection conditions.

[0005] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is: a method for predicting the morphology of acid-etched wall based on a mathematical model, comprising:

[0006] S1: Use a 3D laser scanner and fluid finite element software to perform 3D modeling on the crack surface of the rock plate to obtain a crack space model;

[0007] S2: Based on the preset conditions of the fracture space model and the fluid injection parameters, the pressure field and the velocity field of the fracture space model are coupled and solved using the finite volume method principle to obtain the distribution of the fluid flow dynamics parameters in the fracture;

[0008] S3: Based on the boundary layer, natural diffusion and convective mass transfer theories of acid fluid in fractures, a mathematical model of acid-rock reaction controlled by mass transfer is constructed;

[0009] S4: inputting the distribution of fluid flow dynamics parameters in the fracture into the acid-rock reaction mathematical model to obtain the dissolution mass of each wall node;

[0010] S5: using the dissolution mass of each wall node, analyzing the corresponding relationship with the point dissolution depth, and obtaining the corresponding dissolution depth of the wall;

[0011] S6: using the fracture space model, removing the influence of the corresponding dissolution depth of the wall, obtaining the wall morphology after acid etching, and completing the prediction of the acid-etched wall morphology.

[0012] The beneficial effects of the present invention are as follows: the processor uses the fracture space model and the acid-rock reaction mathematical model to predict the corresponding dissolution depth of the wall surface, obtains the wall surface morphology after acid etching, and completes the prediction of the acid-etched wall surface morphology. By using a three-dimensional laser scanner to obtain a digital model of the real fracture surface morphology, and importing the fluid finite element modeling software to obtain the real fracture space model, the experimental workload is greatly simplified, experimental samples and experimental costs are saved, and the problem of being unable to carry out etching morphology research under different acid injection conditions on the same wall surface is solved; using the fracture space model and the acid-rock reaction mathematical model, the accuracy and efficiency of the acid-etched wall surface prediction can also be improved.

[0013] Furthermore, the S1 includes:

[0014] Use a 3D laser scanner to scan the Brazilian split rock slab and obtain 3D point cloud data of the real rock surface;

[0015] The 3D point cloud data of the real rock surface is finely modeled using fluid finite element software to obtain a gridded fracture space model.

[0016] Based on the theories of acid boundary layer, natural diffusion and convective mass transfer in fractures, a calculation model for acid-rock reaction rate was established under the comprehensive parameter conditions of formation temperature, acid viscosity, acid concentration, acid flow rate and fracture width, which greatly improved the accuracy of the model calculation results.

[0017] Further, the S3 includes:

[0018] Based on the boundary layer theory of acid in cracks, the critical Reynolds number is calculated by using the relationship between acid flow rate, pumping displacement and Reynolds number.

[0019] Based on the natural diffusion theory of acid in fractures, the diffusion coefficient is calculated by using the influence of acid concentration, acid viscosity and formation high temperature on the diffusion of acid during acid flow.

[0020] Based on the convective mass transfer theory of acid solution in fractures, the convective mass transfer coefficient of laminar flow in formation fractures is obtained.

[0021] Using the critical Reynolds number, the diffusion coefficient and the convection mass transfer coefficient, an effective mass transfer coefficient of the acid fluid in the formation fracture is obtained;

[0022] Based on the effective mass transfer coefficient of the acid in the formation fractures, a mass transfer controlled acid-rock reaction mathematical model is constructed using Fick's first law and the acid-rock reaction chemical equation.

[0023] By considering comprehensive parameters such as formation temperature, acid viscosity, acid flow rate, fracture width, etc., it is more in line with the actual formation conditions and the calculation results are more accurate.

[0024] Furthermore, the expression of the critical Reynolds number is:

[0025]

[0026] The expression of the diffusion coefficient is:

[0027] D = [9.77 × 10 -11 EXP(0.0847T)C+1.61×10 -9 EXP(0.023T)] / 1000μ;

[0028] The expression of the convective mass transfer coefficient is:

[0029] k L =0.047w -1 / 2 u 1 / 2 D 2 / 3 v -1 / 6 ;

[0030] Where Re is the critical Reynolds number, Q is the pumping displacement, ρ is the acid density, h is the average fracture height, μ is the acid viscosity, D is the diffusion coefficient, EXP is the natural constant exponential form, T is the formation temperature, C is the acid concentration, k is L represents the convective mass transfer coefficient, w represents the crack width, u represents the acid flow rate, and v represents the kinematic viscosity of the acid.

[0031] Furthermore, the expression of the effective mass transfer coefficient of the acid solution is:

[0032] D e =0.00235w 1 / 2 u 1 / 2 ρ 1 / 6 μ -7 / 6 [9.77×10 -11 e 0.0847T +1.61×10 -9 e 0.023T ];

[0033] The expression of the acid-rock reaction mathematical model is:

[0034] J R1 =2.35w -1 / 2 u 1 / 2 D 2 / 3 v -1 / 6 C;

[0035] J R2 =2.162w -1 / 2 u 1 / 2 D 2 / 3 v -1 / 6 C;

[0036] Among them, D e represents the effective mass transfer coefficient of the acid solution, w represents the fracture width, u represents the acid flow rate, ρ represents the acid density, μ represents the acid viscosity, e represents the natural constant, T represents the formation temperature, C represents the acid concentration, J R1 represents the calcite dissolution rate of the corresponding node, J R2 Indicates the dolomite dissolution rate of the corresponding node.

[0037] A real fracture space model was established using a three-dimensional laser scanner and fluid mechanics finite element software, and the distribution of fluid parameters on the fracture surface was obtained after numerical simulation. The dissolution quality of a single node on the fracture surface was obtained by combining the acid-rock reaction mathematical model, making the analysis of fracture surface dissolution laws more refined and specific.

[0038] Further, the S4 includes:

[0039] The average coverage area of ​​nodes, calcite content, and dolomite content were obtained using a 3D laser scanner and fluid finite element software;

[0040] The distribution of fluid flow dynamics parameters in the fracture, the average coverage area of ​​the nodes, the calcite content and the dolomite content are input into the acid-rock reaction mathematical model to obtain the dissolution quality of each wall node.

[0041] By using the finite element meshing idea, the fracture surface mesh is noded and the control area of ​​a single node is calculated, so that the subsequent dissolution calculation can be refined to specific nodes, which is more in line with the actual formation conditions.

[0042] Furthermore, the expression of the average coverage area of ​​the nodes is:

[0043]

[0044] in, represents the average coverage area of ​​nodes, S represents the wall area, and n represents the number of wall mesh nodes.

[0045] The calculation formulas for dissolution mass and dissolution depth can be used to obtain the dissolution height of each wall node at different times, thereby establishing the dynamic dissolution process of acid solution in the crack and predicting the morphology of the acid-etched wall at different times.

[0046] Furthermore, the expression of the dissolution quality of each wall node is:

[0047]

[0048] Where m represents the dissolution mass of each wall node, x1 represents the calcite content, and J R1 represents the calcite dissolution rate of the corresponding node, x2 represents the dolomite content, J R2 represents the dolomite dissolution rate of the corresponding node, represents the average coverage area of ​​the nodes, and t represents the acid flow simulation time.

[0049] Furthermore, the expression of the wall surface corresponding to the dissolution depth is:

[0050]

[0051] Among them, h represents the corresponding dissolution depth of the wall, m represents the point dissolution quality, represents the average coverage area of ​​nodes, ρ R Indicates the density of acid liquid. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] This specification will be further described in the form of exemplary embodiments, which will be described in detail by the accompanying drawings. These embodiments are not restrictive, and in these embodiments, the same number represents the same structure, wherein:

[0053] Figure 1 It is an exemplary flow chart of a method for predicting acid-etched wall morphology based on a mathematical model according to some embodiments of this specification. DETAILED DESCRIPTION

[0054] The specific implementation modes of the present invention are described below to facilitate those skilled in the art to understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation modes. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concept of the present invention are protected.

[0055] Example

[0056] Figure 1 is an exemplary flow chart of a method for predicting the morphology of acid-etched wall surfaces based on a mathematical model according to some embodiments of this specification. Figure 1 As shown, the process includes the following steps. In some embodiments, the process can be executed by a processor.

[0057] S1: Use a 3D laser scanner and fluid finite element software to perform 3D modeling on the crack surface of the rock slab to obtain a crack space model.

[0058] A 3D laser scanner is an instrument that scans and obtains rock surface information.

[0059] Fluid finite element software is used to model the rock surface and obtain the fracture space model.

[0060] The fracture space model is a three-dimensional space model that reflects the fracture information of the rock surface. For example, the fracture space model may include grid nodes for dividing the wall surface.

[0061] In some embodiments, the processor can use a three-dimensional laser scanner to scan the rock plate to obtain three-dimensional point cloud data of the real rock surface; use fluid finite element software to finely model the three-dimensional point cloud data of the real rock surface to obtain a gridded fracture space model.

[0062] The three-dimensional point cloud data of the real rock surface is data reflecting the distribution of point clouds on the surface of the real rock plate. For example, the three-dimensional point cloud data of the real rock surface may include the three-dimensional point cloud data of the Brazilian split rock surface.

[0063] In some embodiments, the processor may import the three-dimensional point cloud data of the real rock surface into the three-dimensional reverse modeling software to obtain a three-dimensional wall model.

[0064] The three-dimensional wall model is a three-dimensional model that reflects the real rock surface structure.

[0065] In some embodiments, the processor may perform curvature and grid construction on the three-dimensional wall model to obtain a curved three-dimensional wall model.

[0066] The gridded fracture space model is a three-dimensional space model with grid information that reflects the rock surface fracture information.

[0067] In some embodiments, the processor may utilize fluid finite element software to process the curved three-dimensional wall model, and grid the processed model to obtain a gridded fracture space model.

[0068] S2: Based on the preset conditions and fluid injection parameters of the fracture space model, the pressure field and velocity field of the fracture space model are coupled and solved using the finite volume method principle to obtain the distribution of fluid flow dynamics parameters in the fracture.

[0069] Preset conditions are given assumptions used to simplify the prediction model. For example, the preset conditions may include that each input parameter is not affected by temperature, that the heat of acid-rock reaction and the heat conduction between the wall model and the acid are not considered, that the filtration of the acid and the deformation of the wall model do not occur, etc.

[0070] Fluid injection parameters are the initial conditions and boundary conditions required by the prediction model. For example, fluid injection parameters may include initial conditions such as injection time, acid density, acid viscosity, injection flow rate, formation temperature, average fracture height, and pumping displacement, and boundary conditions such as import and export types.

[0071] In some embodiments, the processor can obtain initial conditions and boundary conditions based on the scanning of the crack surface of the rock plate.

[0072] The principle of the finite volume method is to use the conservation equations in integral form to calculate the numerical values ​​of fluid mechanics.

[0073] The distribution of fluid flow dynamics parameters in fractures is the data reflecting the distribution of acid flow velocity on the fracture surface using three-axis coordinates.

[0074] In some embodiments, the processor may utilize the finite volume method principle to solve the fracture space model based on preset conditions and fluid injection parameters to obtain the distribution of fluid flow dynamics parameters in the fracture.

[0075] S3: Based on the boundary layer, natural diffusion and convective mass transfer theories of acid fluid in fractures, a mathematical model of acid-rock reaction controlled by mass transfer is constructed.

[0076] The boundary layer theory of acid fluid in cracks is a theory that reflects the influence of viscous force on the movement of fluid.

[0077] The natural diffusion theory of acid solution in seams is a theory that reflects the natural movement and diffusion of fluids.

[0078] The convective mass transfer theory of acid solution in cracks is a theory that reflects the mass transfer between fluid and solid wall.

[0079] The acid-rock reaction mathematical model of mass transfer control is a mathematical model that reflects the movement of acid and the reaction between acid and rock surface.

[0080] In some embodiments, the processor can calculate the critical Reynolds number based on the boundary layer theory of the acid fluid in the fracture and the relationship between the acid fluid flow rate, pumping displacement and Reynolds number; calculate the diffusion coefficient based on the natural diffusion theory of the acid fluid in the fracture and the influence of the acid fluid concentration, acid fluid viscosity and the high temperature of the formation on the diffusion of the acid fluid during the flow of the acid fluid; obtain the convective mass transfer coefficient of the laminar flow in the formation fracture based on the convective mass transfer theory of the acid fluid in the fracture; obtain the effective mass transfer coefficient of the acid fluid in the formation fracture using the critical Reynolds number, the diffusion coefficient and the convective mass transfer coefficient of the flow; based on the effective mass transfer coefficient of the acid fluid in the formation fracture, construct a mathematical model of the acid-rock reaction controlled by mass transfer using Fick's first law and the chemical equation of the acid-rock reaction.

[0081] The critical Reynolds number is a parameter used to determine the flow state of the acid. For example, a Reynolds number less than 2300 may be laminar flow, a Reynolds number between 2300 and 4000 may be transitional flow, and a Reynolds number greater than 4000 may be turbulent flow. When the Reynolds number of the acid flow in the crack is less than 500, it can be said that the flow of the acid in the crack is mainly laminar flow.

[0082] In some embodiments, the expression for the critical Reynolds number may be:

[0083]

[0084] Where Re represents the critical Reynolds number, Q represents the pump displacement, ρ represents the acid density, h represents the average seam height, and μ represents the acid viscosity.

[0085] The diffusion coefficient is a parameter that describes the diffusion of acid flow.

[0086] In some embodiments, the expression for the diffusion coefficient may be:

[0087] D = [9.77 × 10 -11 EXP(0.0847T)C+1.61×10 -9 EXP(0.023T)] / 1000μ;

[0088] Wherein, D represents the diffusion coefficient, EXP represents the natural constant exponential form, T represents the formation temperature, and C represents the acid concentration.

[0089] The convective mass transfer coefficient is a parameter that describes the reaction between the acid and the rock surface in the laminar flow in the formation fracture.

[0090] In some embodiments, the expression for the convective mass transfer coefficient may be:

[0091] k L =0.047w -1 / 2 u 1 / 2 D 2 / 3 v -1 / 6 ;

[0092] Among them, k L represents the convective mass transfer coefficient, w represents the crack width, u represents the acid flow rate, and v represents the kinematic viscosity of the acid.

[0093] The effective mass transfer coefficient of acid fluid reflects the mass transfer capacity of hydrogen ions from acid fluid to the rock surface and determines the parameter of rock dissolution rate during acid fracturing.

[0094] In some embodiments, the expression of the effective mass transfer coefficient of the acid solution can be:

[0095] D e =0.00235w 1 / 2 u 1 / 2 ρ 1 / 6 μ -7 / 6 [9.77×10 -11 e 0.0847T +1.61×10 -9 e 0.023T ];

[0096] Among them, D e represents the effective mass transfer coefficient of acid, w represents the fracture width, u represents the acid flow rate, ρ represents the acid density, μ represents the acid viscosity, e represents the natural constant, T represents the formation temperature, and C represents the acid concentration.

[0097] Fick's first law is a law that describes the flow rate of a diffusing substance per unit time through a unit cross-sectional area perpendicular to the diffusion direction.

[0098] The acid-rock reaction chemical equation is a chemical equation that reflects the changes in matter caused by acid salt reactions.

[0099] In some embodiments, the expression of the acid-rock reaction mathematical model may be:

[0100] J R1 =2.35w -1 / 2 u 1 / 2 D 2 / 3 v -1 / 6 C;

[0101] J R2 =2.162w -1 / 2 u 1 / 2 D 2 / 3 v -1 / 6 C;

[0102] Among them, J R1 represents the calcite dissolution rate of the corresponding node, J R2 Indicates the dolomite dissolution rate of the corresponding node.

[0103] S4: Input the distribution of fluid flow dynamics parameters in the fracture into the acid-rock reaction mathematical model to obtain the dissolution mass of each wall node.

[0104] The dissolution mass of each wall node is the mass data reflecting the loss of the rock surface at the wall node after acid dissolution.

[0105] In some embodiments, the processor can use a three-dimensional laser scanner and fluid finite element software to obtain the average coverage area of ​​the nodes, the calcite content and the dolomite content; the distribution of the fluid flow dynamics parameters in the fracture, the average coverage area of ​​the nodes, the calcite content and the dolomite content are input into the acid-rock reaction mathematical model to obtain the dissolution mass of each wall node.

[0106] The average node coverage area is data that reflects the average coverage area of ​​each node.

[0107] In some embodiments, the expression of the average coverage area of ​​the nodes may be:

[0108]

[0109] in, represents the average coverage area of ​​the nodes, S represents the wall area, n represents the number of wall grid nodes, and the calcite content is the amount of calcite contained in the rock wall within each node.

[0110] Dolomite content is the amount of dolomite contained in the rock wall within each node.

[0111] In some embodiments, the processor may use a three-dimensional laser scanner to scan the rock plate to obtain the calcite content and dolomite content corresponding to each node.

[0112] In some embodiments, the expression of the dissolution quality of each wall node can be:

[0113]

[0114] Where m represents the dissolution mass of each wall node, x1 represents the calcite content, and J R1 represents the calcite dissolution rate of the corresponding node, x2 represents the dolomite content, J R2 represents the dolomite dissolution rate of the corresponding node, represents the average coverage area of ​​the nodes, and t represents the acid flow simulation time.

[0115] S5: Analyze the corresponding relationship between the dissolution quality of each wall node and the point dissolution depth to obtain the corresponding dissolution depth of the wall.

[0116] The corresponding dissolution depth of the wall is data reflecting the depth change after wall dissolution.

[0117] In some embodiments, the expression of the wall surface corresponding to the dissolution depth can be:

[0118]

[0119] Among them, h represents the corresponding dissolution depth of the wall, m represents the point dissolution quality, represents the average coverage area of ​​nodes, ρ R Indicates the density of acid liquid.

[0120] S6: using the fracture space model, removing the influence of the corresponding dissolution depth of the wall, obtaining the wall morphology after acid etching, and completing the prediction of the acid-etched wall morphology.

[0121] The wall morphology after acid etching reflects the wall morphology of the rock slab after being dissolved by acid.

[0122] In some embodiments, the processor may use the obtained wall dissolution depth of each grid to process the corresponding grid in the fracture space model to obtain the wall morphology after acid etching.

[0123] In some embodiments of this specification, the processor uses the fracture space model and the acid-rock reaction mathematical model to predict the corresponding dissolution depth of the wall, obtain the wall morphology after acid etching, and complete the prediction of the acid-etched wall morphology. In this way, the experimental workload is greatly simplified, experimental samples and experimental costs are saved, and the problem of not being able to carry out etching morphology research under different acid injection conditions on the same wall is solved; the fracture space model and the acid-rock reaction mathematical model can also improve the accuracy and efficiency of acid-etched wall prediction.

Claims

1. A method for predicting the morphology of acid-etched wall based on a mathematical model, characterized in that: include: S1: Use a 3D laser scanner and fluid finite element software to perform 3D modeling on the crack surface of the rock plate to obtain a crack space model; S2: Based on the preset conditions of the fracture space model and the fluid injection parameters, the pressure field and the velocity field of the fracture space model are coupled and solved using the finite volume method principle to obtain the distribution of the fluid flow dynamics parameters in the fracture; S3: Based on the boundary layer, natural diffusion and convective mass transfer theories of acid fluid in fractures, a mathematical model of acid-rock reaction controlled by mass transfer is constructed; S4: inputting the distribution of fluid flow dynamics parameters in the fracture into the acid-rock reaction mathematical model to obtain the dissolution mass of each wall node; S5: using the dissolution mass of each wall node, analyzing the corresponding relationship with the point dissolution depth, and obtaining the corresponding dissolution depth of the wall; S6: using the fracture space model, removing the influence of the corresponding dissolution depth of the wall, obtaining the wall morphology after acid etching, and completing the prediction of the acid-etched wall morphology.

2. The method for predicting the acid-etched wall morphology based on a mathematical model according to claim 1, characterized in that: The S1 includes: Use a 3D laser scanner to scan the rock slab and obtain the 3D point cloud data of the real rock surface; The three-dimensional point cloud data of the real rock surface is finely modeled using fluid finite element software to obtain a gridded fracture space model.

3. The method for predicting the acid-etched wall morphology based on a mathematical model according to claim 1, characterized in that: The S3 includes: Based on the boundary layer theory of acid in cracks, the critical Reynolds number is calculated by using the relationship between acid flow rate, pumping displacement and Reynolds number. Based on the natural diffusion theory of acid in fractures, the diffusion coefficient is calculated by using the influence of acid concentration, acid viscosity and formation high temperature on the diffusion of acid during acid flow. Based on the convective mass transfer theory of acid in fractures, the convective mass transfer coefficient of laminar flow in formation fractures is obtained; Using the critical Reynolds number, the diffusion coefficient and the convection mass transfer coefficient, an effective mass transfer coefficient of the acid fluid in the formation fracture is obtained; Based on the effective mass transfer coefficient of the acid in the formation fractures, a mass transfer controlled acid-rock reaction mathematical model is constructed using Fick's first law and the acid-rock reaction chemical equation.

4. The method for predicting the acid-etched wall morphology based on a mathematical model according to claim 3, characterized in that: The expression of the critical Reynolds number is: The expression of the diffusion coefficient is: D=[9.77×10 -11 EXP(0.0847T)C+1.61×10 -9 EXP(0.023T)] / 1000μ; The expression of the convective mass transfer coefficient is: <h2 style=";text-align:left;direction:ltr">k<h2 style=";text-align:left;direction:ltr"> L <h2 style=";text-align:left;direction:ltr"> <0.047w<h2 style=";text-align:left;direction:ltr"> -1 / 2 <h2 style=";text-align:left;direction:ltr"> u<h2 style=";text-align:left;direction:ltr"> 1 / 2 <h2 style=";text-align:left;direction:ltr"> D<h2 style=";text-align:left;direction:ltr"> 2 / 3 <h2 style=";text-align:left;direction:ltr"> v<h2 style=";text-align:left;direction:ltr"> -1 / 6 <h2 style=";text-align:left;direction:ltr"> ; Where Re is the critical Reynolds number, Q is the pumping displacement, ρ is the acid density, h is the average fracture height, μ is the acid viscosity, D is the diffusion coefficient, EXP is the natural constant exponential form, T is the formation temperature, C is the acid concentration, k is L represents the convective mass transfer coefficient, w represents the crack width, u represents the acid flow rate, and v represents the kinematic viscosity of the acid.

5. The method for predicting the acid-etched wall morphology based on a mathematical model according to claim 3, characterized in that: The expression of the effective mass transfer coefficient of the acid solution is: D e =0.00235w 1 / 2 you 1 / 2 r 1 / 6 m -7 / 6 [9.77×10 -11 e 0.0847T +1.61×10 -9 e 0.023T ]; The expression of the acid-rock reaction mathematical model is: J R1 =2.35w -1 / 2 u 1 / 2 D 2 / 3 v -1 / 6 C; J R2 =2.162w -1 / 2 you 1 / 2 D 2 / 3 v -1 / 6 C; Among them, D e represents the effective mass transfer coefficient of the acid solution, w represents the fracture width, u represents the acid flow rate, ρ represents the acid density, μ represents the acid viscosity, e represents the natural constant, T represents the formation temperature, C represents the acid concentration, J R1 represents the calcite dissolution rate of the corresponding node, J R2 Indicates the dolomite dissolution rate of the corresponding node.

6. The method for predicting the acid-etched wall morphology based on a mathematical model according to claim 1, characterized in that: The S4 includes: The average coverage area of ​​nodes, calcite content, and dolomite content were obtained using a 3D laser scanner and fluid finite element software; The distribution of fluid flow dynamics parameters in the fracture, the average coverage area of ​​the nodes, the calcite content and the dolomite content are input into the acid-rock reaction mathematical model to obtain the dissolution quality of each wall node.

7. The method for predicting the acid-etched wall morphology based on a mathematical model according to claim 6, characterized in that: The expression of the average coverage area of ​​the nodes is: in, represents the average coverage area of ​​nodes, S represents the wall area, and n represents the number of wall mesh nodes.

8. The method for predicting the acid-etched wall morphology based on a mathematical model according to claim 6, characterized in that: The expression of the dissolution quality of each wall node is: Where m represents the dissolution mass of each wall node, x1 represents the calcite content, and J R1 represents the calcite dissolution rate of the corresponding node, x2 represents the dolomite content, J R2 represents the dolomite dissolution rate of the corresponding node, represents the average coverage area of ​​the nodes, and t represents the acid flow simulation time.

9. The method for predicting the acid-etched wall morphology based on a mathematical model according to claim 1, characterized in that: The expression of the wall surface corresponding to the dissolution depth is: Among them, h represents the corresponding dissolution depth of the wall, m represents the point dissolution quality, represents the average coverage area of ​​nodes, ρ R Indicates the density of acid liquid.

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