A method for evaluating the flow drag reduction performance of fracturing fluid considering viscoelasticity

Abstract

A method for evaluating the drag reduction performance of fracturing fluid considering viscoelasticity is disclosed, relating to the field of fracturing fluid performance evaluation technology. The method includes the following steps: preparing fracturing fluid samples and testing their rheological properties using a rheometer; determining viscoelastic parameters by fitting the FENE-P constitutive equation; coupling the FENE-P equation and the Navier-Stokes equation into Fluent software based on a UDF to establish a geometric model of the jet channel in a flat plate fracture and complete mesh generation, setting initial and boundary conditions; numerically simulating the flow of fracturing fluid in a flat plate fracture, calculating the drag reduction rate through the flow pressure difference, and analyzing the drag reduction mechanism of the fracturing fluid. This invention provides a method that can accurately capture the elastic behavior and deformation field information of viscoelastic fracturing fluids, with simulation results more closely matching the actual flow state and high evaluation accuracy. It can provide reliable theoretical and data support for the development of fracturing fluid drag reducers and the analysis of drag reduction mechanisms.

Description

Technical Field

[0001] This invention relates to the field of fracturing fluid performance evaluation, and more specifically, to a method for evaluating the drag reduction performance of fracturing fluid considering viscoelasticity. Background Technology

[0002] Fracturing is a core technology for enhancing oil and gas field production. As the working medium in fracturing operations, the drag reduction performance of fracturing fluid directly affects the efficiency and cost of fracturing operations. Fracturing fluid is a typical viscoelastic fluid. Compared to Newtonian fluids, it not only exhibits viscous characteristics but also significant elastic behavior. However, in existing engineering simulations, Fluent software's non-Newtonian fluid model is only designed for generalized Newtonian fluids, modifying only the fluid viscosity. It cannot represent the elastic behavior of viscoelastic fluids, nor can it capture the deformation field information within viscoelastic fluids. This makes it difficult to accurately describe the actual flow state of the fracturing fluid, resulting in a significant deviation between the drag reduction performance evaluation results and the actual situation.

[0003] In existing technologies, constitutive equations describing viscoelastic fluids mainly include models such as FENE-P, Giesekus, Oldroyd-B, and Maxwell. Among them, the FENE-P model has become the mainstream model for characterizing the viscoelasticity of polymer solutions because it can consider the maximum elongation limit of polymer chains and avoid non-physical phenomena at high Weissenberg numbers. However, there is currently no systematic evaluation method for the drag reduction performance of fracturing fluids based on the FENE-P model, combining numerical simulation and experimental testing, which cannot provide accurate technical support for fracturing fluid formulation optimization and drag-reducing agent development. Therefore, developing a drag reduction performance evaluation method that can accurately characterize the viscoelasticity of fracturing fluids and closely reflect the actual flow state has become an urgent technical problem to be solved in this field. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a method for evaluating the drag reduction performance of fracturing fluids that considers viscoelasticity. This method solves the problems of existing technologies being unable to accurately characterize the elastic behavior of fracturing fluids and having large deviations in drag reduction performance evaluation, thereby achieving a precise evaluation of the drag reduction performance of fracturing fluids.

[0005] To achieve the above-mentioned objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for evaluating the drag reduction performance of fracturing fluid considering viscoelasticity includes the following steps:

[0007] S1. Prepare fracturing fluid samples and test their rheological properties: Add a certain mass fraction of drag-reducing agent to clean water, stir evenly to prepare fracturing fluid samples; use a rheometer to shear the fracturing fluid samples within a certain shear rate range to obtain shear stress-shear rate related characteristic parameters.

[0008] S2. Determine viscoelastic parameters based on the FENE-P constitutive equation: The FENE-P constitutive equation is used to characterize the rheological behavior of fracturing fluid. The rheological parameters obtained in step S1 are used for linear fitting to determine the key viscoelastic parameters of the FENE-P constitutive equation.

[0009] S3. Write UDF and implement the coupling of FENE-P equations with Fluent software: Based on the macro definition function of UDF, write the compilation code for the unsteady terms, convection terms, source terms of user-defined scalar transport equations and elastic stress terms in momentum equations respectively, load the FENE-P equations into Fluent software, and realize the coupled solution of FENE-P equations and NS equations.

[0010] S4. Construct a flat plate fracture jet channel model and perform mesh generation: A flat plate fracture jet channel model is constructed using numerical simulation software, with several inlets set in the flow direction to simulate perforation holes; the flat plate fracture jet channel model is structurally meshed using ICEM software, and the mesh is refined for the near-wellbore jet region and near-wall boundary layer.

[0011] S5. Set boundary conditions and perform numerical calculations of the model: Import the mesh model from step S4 into Fluent software, load the UDF from step S3, set boundary conditions, perform numerical calculations of the model, and evaluate the drag reduction performance and conduct mechanism analysis based on the calculation results.

[0012] Furthermore, in other preferred embodiments of the present invention, in step S1, the drag-reducing agent has a mass fraction of 0.01% to 0.3%, a shear rate range of 0.1 s⁻¹ to 500 s⁻¹, and a shear time of 20 min.

[0013] Furthermore, in other preferred embodiments of the present invention, in step S2, the FENE-P constitutive equation includes:

[0014] (1)

[0015] (2)

[0016] (3)

[0017] (4)

[0018] (5)

[0019] In the formula: , , ,and Let be the solution viscosity, solvent viscosity, polymer viscosity, and zero-shear viscosity of the solution, in Pa·s; The polymer relaxation time is in seconds. The shear rate is 1 / s; This represents the dimensionless maximum tensile length of the polymer.

[0020] Furthermore, in other preferred embodiments of the present invention, in step S2, the key viscoelastic parameters include solute viscosity, polymer relaxation time, and maximum molecular elongation.

[0021] Furthermore, in other preferred embodiments of the present invention, in step S4, the mesh refinement of the near-wellbore jet region and the near-wall boundary layer includes: refining the near-wellbore jet region in the x and z directions with the fracture length direction as the x direction, the fracture width direction as the y direction, and the fracture height direction as the z direction, and refining the boundary layer near the wall in the y direction.

[0022] Furthermore, in other preferred embodiments of the present invention, step S5, setting boundary conditions includes: setting the inlet as a velocity inlet and jet velocity, the outlet as a pressure outlet, and the wall as a solid wall with no slippage boundary.

[0023] Furthermore, in other preferred embodiments of the present invention, step S5, the evaluation of drag reduction performance includes calculating the drag reduction rate, the formula for which the drag reduction rate is calculated is:

[0024] (6)

[0025] In the formula, For drag reduction ratio, For the frictional pressure difference of clear water, This represents the pressure differential of the fracturing fluid flow.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) This invention combines the FENE-P viscoelastic constitutive equation with Fluent numerical simulation and uses UDF to achieve coupled solution of the FENE-P equation and NS equation, which makes up for the deficiency that the existing Fluent non-Newtonian fluid model cannot characterize the elastic behavior of fracturing fluid. It can accurately capture the deformation field information of viscoelastic fracturing fluid and make the simulation results more consistent with the actual flow state of fracturing fluid.

[0028] (2) This invention constructs an integrated drag reduction performance evaluation system of "experimental testing + numerical simulation + mechanism analysis". First, the basic rheological data of fracturing fluid is obtained by rheometer testing. Then, numerical simulation is carried out in combination with the fitted viscoelastic parameters. Finally, the drag reduction performance is evaluated from multiple dimensions such as drag reduction rate, velocity distribution, turbulent kinetic energy distribution and flow field trace. The evaluation results are comprehensive and accurate, providing precise data support for the optimization of fracturing fluid formulation.

[0029] (3) This invention can not only realize the quantitative calculation of the drag reduction rate of fracturing fluid, but also reveal the drag reduction mechanism of fracturing fluid from a microscopic perspective, clarify the regulation law of viscoelasticity on turbulence, and provide a reliable theoretical basis for the research and development of new drag reduction agents and the optimization of fracturing construction technology. Attached Figure Description

[0030] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 A flowchart illustrating the evaluation method provided by this invention;

[0032] Figure 2 The rheological test curve of the fracturing fluid provided in the embodiment of the present invention;

[0033] Figure 3 A geometric model diagram of a flat plate crack jet channel provided in an embodiment of the present invention;

[0034] Figure 4 A graph showing the dimensionless axial average velocity distribution along the normal direction of water and fracturing fluid provided in an embodiment of the present invention.

[0035] Figure 5 Turbulent kinetic energy distribution curves of water and fracturing fluid provided for embodiments of the present invention;

[0036] Figure 6 The flow field trace diagrams of water and fracturing fluid provided in the embodiments of the present invention. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to represent selected embodiments of the invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] To address the problems of existing technologies failing to accurately characterize the elastic behavior of fracturing fluids and exhibiting large deviations in drag reduction performance evaluation, such as... Figure 1 As shown, this invention provides a method for evaluating the drag reduction performance of fracturing fluid considering viscoelasticity, which includes the following steps:

[0039] S1. Prepare fracturing fluid samples and test their rheological properties: Add a certain mass fraction of drag-reducing agent to clean water, stir evenly to prepare fracturing fluid samples; use a rheometer to shear the fracturing fluid samples within a certain shear rate range to obtain shear stress-shear rate related characteristic parameters.

[0040] S2. Determine viscoelastic parameters based on the FENE-P constitutive equation: The FENE-P constitutive equation is used to characterize the rheological behavior of fracturing fluid. The rheological parameters obtained in step S1 are used for linear fitting to determine the key viscoelastic parameters of the FENE-P constitutive equation.

[0041] S3. Write UDF and implement the coupling of FENE-P equations with Fluent software: Based on the macro definition function of UDF, write the compilation code for the unsteady terms, convection terms, source terms of user-defined scalar transport equations and elastic stress terms in momentum equations respectively, load the FENE-P equations into Fluent software, and realize the coupled solution of FENE-P equations and NS equations.

[0042] S4. Construct a flat plate fracture jet channel model and perform mesh generation: A flat plate fracture jet channel model is constructed using numerical simulation software, with several inlets set in the flow direction to simulate perforation holes; the flat plate fracture jet channel model is structurally meshed using ICEM software, and the mesh is refined for the near-wellbore jet region and near-wall boundary layer.

[0043] S5. Set boundary conditions and perform numerical calculations of the model: Import the mesh model from step S4 into Fluent software, load the UDF from step S3, set boundary conditions, perform numerical calculations of the model, and evaluate the drag reduction performance and conduct mechanism analysis based on the calculation results.

[0044] Further, in step S1, a certain mass fraction of drag-reducing agent is added to clean water, and the mixture is placed on a magnetic stirrer and stirred thoroughly to obtain a fracturing fluid sample; using a German HAAKE MARS III rheometer, a shear test is performed on the fracturing fluid sample for 20 minutes in the range of shear rate from 0.1 s⁻¹ to 500 s⁻¹, and shear stress and shear rate data are continuously collected during the shear process to form the shear viscosity curve of the fracturing fluid.

[0045] Furthermore, in step S2, the FENE-P constitutive equation is used to characterize the rheological behavior of the fracturing fluid. The FENE-P constitutive equation can predict the relationship between shear stress and shear rate through polymer relaxation time, maximum molecular elongation, and solute viscosity, while also characterizing the apparent viscosity change and elastic behavior of the polymer solution. Based on the rheological test results of step S1, the data is processed, and a linear equation is fitted based on the FENE-P model to determine key viscoelastic parameters such as solute viscosity, polymer relaxation time, and maximum molecular elongation in the model.

[0046] Furthermore, in step S3, since the total stress of a viscoelastic fluid is the sum of Newtonian fluid stress and elastic stress terms, the transport equation of the momentum equation in tensor form and the molecular deformation rate tensor of the viscoelastic fluid are constructed based on this. Using the UDF function of Fluent software, the compilation code for loading the source terms of the transport equation and the user-defined scalar equation is defined.

[0047] For the total stress tensor of a viscoelastic fluid, an elastic stress term needs to be added to the Newtonian fluid stress. ,Right now:

[0048] (7)

[0049] In the formula, For the total stress tensor, For solvent viscosity stress tensor, This is the polymer elastic stress tensor.

[0050] (8)

[0051] In the formula, For polymer viscosity, The polymer relaxation time, For the finite stretching correction function of the FENE-P model, For configuration tensors, The symbol is Kronecker, with a value of 1 when i=j and a value of 0 when i≠j.

[0052] (9)

[0053] In the formula, This represents the dimensionless maximum tensile length of the polymer. For configuration tensor The traces.

[0054] The momentum equation of a viscoelastic fluid in tensor form is:

[0055] (10)

[0056] In the formula, For fluid density, , For fluid velocity components, For time, , For spatial coordinate components, For hydrostatic pressure, This represents the solvent viscosity.

[0057] Deformation rate tensor of viscoelastic fluid molecules The transport equation is:

[0058] (11)

[0059] In the formula, For fluid velocity components, For spatial coordinate components, is the configuration tensor diffusion coefficient.

[0060] In Fluent software, UDF stands for User-Defined Function, which allows users to extend the functionality of Fluent by writing C language code to meet specific simulation needs. In this step, the ability to define and load source terms of the transport equation and user-defined scalar equations within the UDF is used to load the FENE-P equations into Fluent and couple them with the NS equations for solution, thereby performing numerical simulation analysis of viscoelastic fluid flow.

[0061] In UDF, the general form of the user-defined scalar transport equation is shown in Equation (12), from left to right of the equation are the unsteady term, convection term, diffusion term and source term.

[0062] (12)

[0063] In the formula, Allow users to define scalars (such as concentration, temperature, component mass fraction, etc.). For the convective flux vector components, The source term for the scalar.

[0064] Among them, the unsteady terms are written using the DEFINE_UDS_UNSTEADY macro, the convection terms are written using the DEFINE_UDS_FLUX macro, the diffusion terms are loaded by defining the stress diffusion coefficient in the material properties, and the source terms and the elastic stress terms of the momentum equation are both written using the DEFINE_SOURCE macro.

[0065] Loading the UDF that has been written above into Fluent software enables the coupled solution of the FENE-P equation and the NS equation, laying the foundation for numerical simulation of viscoelastic fluid flow.

[0066] Furthermore, in step S4, a geometric model of the flat-plate fracture jet channel is constructed based on the fracture characteristics of the actual fracturing operation; several square inlets are set in the flow direction; structural meshing is performed using ICEM software, and the mesh is refined in the near-wellbore jet region and near-wall boundary layer to improve simulation accuracy.

[0067] Furthermore, in step S5, the structured mesh model constructed in step S4 is imported into Fluent software, the UDF written in step S3 is loaded, and then the boundary conditions for simulation are set to complete the initialization of the calculation parameters; then iterative calculations can be carried out according to the numerical simulation calculation process of the FENE-P model.

[0068] The specific process of iterative calculation includes:

[0069] (1) Initialize the calculation model using panel input values ​​or default values;

[0070] (2) Call the UDF to perform secondary initialization of the user-defined scalar field;

[0071] (3) Enter the iterative loop and solve the momentum equations in the x, y, and z directions in sequence;

[0072] (4) Solve the continuity equation and update the fluid velocity;

[0073] (5) Solve the 6 user-defined scalar equations;

[0074] (6) Check whether the calculation results are converged according to the preset convergence criteria. If converged, exit the loop and complete the calculation. If not converged, return to step (3) to continue iterating until the convergence requirements are met.

[0075] For clean water, the SST k-ω model is used, while for fracturing fluid, the FENE-P viscoelastic model is loaded using the UDF method. By changing the viscoelastic parameters of the FENE-P model, the flow numerical simulation of different fracturing fluids can be achieved. Based on the calculation results, the drag reduction performance can be further evaluated and the drag reduction mechanism can be analyzed. Based on the flow pressure difference between clean water and fracturing fluid at the same flow distance obtained from the simulation, the drag reduction rate of the fracturing fluid is obtained by calculation formula (6). Based on the dimensionless axial average velocity distribution and turbulent kinetic energy distribution data in the simulation results, the distribution curve is plotted, and the flow field trace diagrams of clean water and fracturing fluid are generated simultaneously, so that their flow characteristics can be analyzed. Specifically, by combining the velocity distribution, turbulent kinetic energy distribution and flow field trace diagrams, the flow characteristics of fracturing fluid in the viscous sublayer, buffer layer and logarithmic layer can be analyzed, which can clarify the regulatory effect of the viscoelasticity of fracturing fluid on the turbulent eddy energy and explore the drag reduction mechanism.

[0076] According to the method provided by the present invention, a specific application example is provided, and the specific steps are as follows:

[0077] S1. Prepare fracturing fluid samples and test their rheological properties.

[0078] Add 0.03% (w / w) of emulsion drag reducer to clean water, place the mixture in a magnetic stirrer, and stir at 300 r / min for 10 min to obtain a homogeneous fracturing fluid sample. Using a German HAAKE MARS III rheometer, with a shear rate range of 0.1 s⁻¹ to 500 s⁻¹, conduct continuous shear tests on the fracturing fluid sample for 20 min, collect shear stress-shear rate data, and plot the shear viscosity curve of the fracturing fluid, as shown below. Figure 2 As shown.

[0079] S2. Determining viscoelastic parameters based on the FENE-P constitutive equation

[0080] The rheological behavior of PAM solution was characterized by the FENE-P constitutive equation (Equation (1)-Equation (5)). Based on the FENE-P constitutive equation, the rheological parameters obtained in step S1 were linearly fitted to determine the key viscoelastic parameters of the FENE-P model: polymer relaxation time is 0.74 s, maximum molecular elongation is 100, and solute viscosity is 0.0017 Pa·s.

[0081] S3. Write a UDF and couple the FENE-P equations with Fluent software.

[0082] The Fluent UDF program was written in C language. The unsteady terms, convection terms, source terms and elastic stress terms were written by using the macros DEFINE_UDS_UNSTEADY, DEFINE_UDS_FLUX and DEFINE_SOURCE respectively. The completed UDF file was compiled and loaded into the Fluent software to realize the coupled solution of the FENE-P equation and the NS equation.

[0083] S4. Construct a model of the jet channel in a flat plate crack and perform mesh generation.

[0084] A geometric model of the flat-plate fracture jet channel was constructed using SpaceClaim software. The model is 3m long, 0.3m high, and 1cm wide, with three square inlets of 1cm each in the flow direction. Figure 3 As shown, the geometric model was imported into ICEM software for structural mesh generation. The near-well jet region was refined in the x and z directions, and the boundary layer near the wall was refined in the y direction. Finally, a structured mesh with 1000 meshes in the x direction, 167 meshes in the z direction, and 20 meshes in the y direction was generated, with a total of 3.34 million meshes and a mesh quality greater than 0.85.

[0085] S5. Set boundary conditions and perform numerical calculations for the model.

[0086] Import the mesh model into Fluent software and load the compiled UDF; set the boundary conditions: the inlet is a velocity inlet with a jet velocity of 2.8 m / s; the outlet is a pressure outlet with a gauge pressure of 0 Pa; the wall is a solid wall with no slip boundary; the SSTk-ω model is selected as the turbulence model, and the PISO algorithm is selected as the solution algorithm.

[0087] During numerical iterative calculations, the computational model and user-defined scalar field are first initialized. Then, the momentum equations in the x, y, and z directions are solved sequentially, the continuity equation is solved, and the velocity is updated. Subsequently, six user-defined scalar equations are solved. The convergence criterion is set to ensure that all residuals are less than 10. -6 If the calculation result meets the convergence requirement, stop the iteration and exit the loop. The calculation time step is set to 0.001s, the number of time steps is 10000, and the maximum number of iterations is 50.

[0088] In order to avoid the influence of the inlet on the flow field and to allow the fluid flow to develop fully, the yz cross section at a distance of x1=1.5 m and x2=2.9 m from the inlet in the flow direction was selected as the pressure measurement position. The pressure type was selected as area weighted average pressure. The drag reduction rate was calculated according to formula (6) as shown in Table 1.

[0089] Table 1. Calculation results of drag reduction rates for water and fracturing fluid

[0090]

[0091] The simulated frictional pressure difference of clear water is 297 Pa, and the flowing pressure difference of the fracturing fluid is 167 Pa. The calculated drag reduction rate is 43.8%.

[0092] Figure 4 It is the curve graph of the dimensionless axial average velocity of clear water and the fracturing fluid along the normal direction at the test section. It can be seen that the axial average velocity of the fracturing fluid in the viscous sublayer (y+<5) basically coincides with that of clear water. In the buffer layer (5<y+<30), the velocity increases rapidly and exceeds that of clear water. In the logarithmic layer (y+>30), it shows a logarithmic law distribution, and the velocity in the logarithmic region is significantly higher than that of clear water. Figure 5 It is the distribution curve of the turbulent kinetic energy of clear water and the fracturing fluid. The turbulent kinetic energy of the fracturing fluid in the turbulent core region is significantly lower than that of clear water. The flow field trace is smoother than that of clear water, and there is no obvious distortion and chaos phenomenon.

[0093] Figure 6 It is the trace map of clear water and the fracturing fluid (the upper part is the trace map of clear water, and the lower part is the trace map of the fracturing fluid). It can be seen that in the near-well jet region, the streamline of clear water is extremely distorted and chaotic, and there are also many vortex structures. As the flow distance increases, it gradually changes to a laminar flow regime. The viscoelasticity of the fracturing fluid stores part of the energy of the turbulent vortices in the polymer network structure in the form of elasticity, reduces the kinetic energy consumption of the turbulent vortices, makes the small-scale turbulent vortices decrease, the proportion of large-scale vortices increase, and the streamline smoothness enhance, thus achieving a significant drag reduction effect.

[0094] It can be seen from this that the present invention provides a method for evaluating the flow drag reduction performance of a fracturing fluid considering viscoelasticity. By preparing a fracturing fluid sample and testing the rheological characteristic parameters through a rheometer, the viscoelasticity parameters are determined by fitting with the FENE-P constitutive equation. Then, based on UDF, the FENE-P equation and the N-S equation are coupled and loaded into the Fluent software, a geometric model of a flat plate fracture jet channel is established and the mesh division, initial conditions and boundary conditions are set. Finally, the flow of the fracturing fluid in the flat plate fracture is numerically simulated, the drag reduction rate is calculated through the flow pressure difference, and the drag reduction mechanism of the fracturing fluid is analyzed by combining the dimensionless axial average velocity distribution, turbulent kinetic energy distribution and flow field trace, which can accurately capture the elastic behavior and deformation field information of the viscoelastic fracturing fluid, and provide reliable theoretical and data support for the analysis of the flow characteristics and drag reduction mechanism of the fracturing fluid.

[0095] The above are only the preferred embodiments of the present invention, and are not used to limit the scope of implementation of the present invention; if the present invention is modified or equivalently replaced without departing from the spirit and scope of the present invention, it should be covered within the protection scope of the claims of the present invention.

Claims

1. A method for evaluating the drag reduction performance of fracturing fluid considering viscoelasticity, characterized in that, Includes the following steps: S1. Prepare fracturing fluid samples and test their rheological properties: Add a certain mass fraction of drag-reducing agent to clean water, stir evenly to prepare fracturing fluid samples; use a rheometer to shear the fracturing fluid samples within a certain shear rate range to obtain shear stress-shear rate related characteristic parameters. S2. Determine viscoelastic parameters based on the FENE-P constitutive equation: The FENE-P constitutive equation is used to characterize the rheological behavior of fracturing fluid. The rheological parameters obtained in step S1 are used for linear fitting to determine the key viscoelastic parameters of the FENE-P constitutive equation. S3. Write UDF and implement the coupling of FENE-P equations with Fluent software: Based on the macro definition function of UDF, write the compilation code for the unsteady terms, convection terms, source terms of user-defined scalar transport equations and elastic stress terms in momentum equations respectively, load the FENE-P equations into Fluent software, and realize the coupled solution of FENE-P equations and NS equations. S4. Construct a flat plate fracture jet channel model and perform mesh generation: A flat plate fracture jet channel model is constructed using numerical simulation software, with several inlets set in the flow direction to simulate perforation holes; the flat plate fracture jet channel model is structurally meshed using ICEM software, and the mesh is refined for the near-wellbore jet region and near-wall boundary layer. S5. Set boundary conditions and perform numerical calculations of the model: Import the mesh model from step S4 into Fluent software, load the UDF from step S3, set boundary conditions, perform numerical calculations of the model, and evaluate the drag reduction performance and conduct mechanism analysis based on the calculation results.

2. The method for evaluating the drag reduction performance of fracturing fluid considering viscoelasticity according to claim 1, characterized in that, In step S1, the drag-reducing agent has a mass fraction of 0.01% to 0.3%, a shear rate range of 0.1 s⁻¹ to 500 s⁻¹, and a shear time of 20 min.

3. The method for evaluating the drag reduction performance of fracturing fluid considering viscoelasticity according to claim 1, characterized in that, In step S2, the FENE-P constitutive equation includes: （1） （2） （3） （4） （5） In the formula: , , ,and Let be the solution viscosity, solvent viscosity, polymer viscosity, and zero-shear viscosity of the solution, in Pa·s; The polymer relaxation time is in seconds. The shear rate is 1 / s; This represents the dimensionless maximum tensile length of the polymer.

4. The method for evaluating the drag reduction performance of fracturing fluid considering viscoelasticity according to claim 1, characterized in that, In step S2, the key viscoelastic parameters include solute viscosity, polymer relaxation time, and maximum molecular elongation.

5. The method for evaluating the drag reduction performance of fracturing fluid considering viscoelasticity according to claim 1, characterized in that, In step S4, the near-wellbore jet region and near-wall boundary layer are meshed, including: with the fracture length direction as the x-direction, the fracture width direction as the y-direction, and the fracture height direction as the z-direction, the near-wellbore jet region is meshed in the x-direction and z-direction, and the boundary layer near the wall is meshed in the y-direction.

6. The method for evaluating the drag reduction performance of fracturing fluid considering viscoelasticity according to claim 1, characterized in that, In step S5, setting boundary conditions includes: setting the inlet as a velocity inlet and jet velocity, the outlet as a pressure outlet, and the wall as a solid wall with no slippage.

7. The method for evaluating the drag reduction performance of fracturing fluid considering viscoelasticity according to claim 1, characterized in that, In step S5, the drag reduction performance evaluation includes calculating the drag reduction rate, and the formula for calculating the drag reduction rate is: （6） In the formula, For drag reduction ratio, For the frictional pressure difference of clear water, This represents the pressure differential of the fracturing fluid flow.

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