Proppant migration simulation method and device based on CFD-DEM model

Abstract

The invention discloses a propping agent migration simulation method and device based on a CFD-DEM model, and the method comprises the steps: obtaining the fracture parameters of channel fracturing and the basic parameters of a laminating propping agent, and building a fracture physical model in a propping agent conveying process; calculating the simulated fracture flow velocity of the fracture physical model according to the pump injection displacement; performing grid division on the fracture physical model to obtain a plurality of grid units; constructing a fracturing liquid phase control equation set; calculating the fluid velocity in each grid unit; solving to obtain the linear velocity and the angular velocity of the film-coated proppant; inputting into finite element analysis software, and carrying out propping agent migration simulation on the basis of a CFD-DEM (Cyclic Frequency Division-Digital Elevation Model); the total volume of the sand bank is calculated according to the conveying process of the film-coated proppant, and the channel rate is calculated; and the pump injection displacement is adjusted, propping agent migration simulation is repeatedly conducted, the channel rate corresponding to each pump injection displacement is obtained, and the pump injection displacement corresponding to the maximum channel rate serves as the optimal pump injection displacement.

Description

Technical Field

[0001] The embodiments of the present invention relate to the technical field of oil and gas field production enhancement and transformation, and in particular to a proppant migration simulation method and device based on a CFD-DEM model. Background Art

[0002] As the development of conventional oil and gas resources enters the later stage, unconventional oil and gas reservoirs have become the main force in oil and gas production. In order to solve the problem of low permeability of unconventional reservoirs, mines use hydraulic fracturing technology to increase the production of oil and gas wells and achieve large-scale development. Schlumberger has developed channel fracturing technology based on conventional fracturing technology. This technology replaces continuous sand paving with non-uniform clustered sand paving, which can construct dispersed infinite diversion channels in fractures. The formation and maintenance of non-uniform clusters of proppants are the key to the success of channel fracturing. In mine operations, the method of injecting fibers and combining pulse sanding is usually used to promote the formation of proppants. Although this method is low-cost, the fiber has poor sand binding performance. In the long-term production process, the clusters in the fractures are easily dispersed, which in turn affects the later conductivity. Non-curing viscous resin coated proppant is a new fracturing material. It will gradually become sticky after soaking, can automatically agglomerate during transportation, and the clusters are highly stable after the fracture is closed. The hydrophobic properties of the coating layer can reduce the adsorption of fracturing fluid and reduce the erosion of reservoir fluid, thereby maintaining a certain compressive strength and ensuring long-term conductivity.

[0003] The existing technology simulates the transport process of proppant in conventional fracturing through numerical calculation. However, the transport process of film-coated proppant in channel fracturing and the evaluation of sand-laying effect are not clear enough. Unlike the transport process of conventional fracturing proppant, the proppant in channel fracturing will be accompanied by the agglomeration of film-coated proppant during transport. The proppant laying situation directly determines the diversion effect of the fracture. Therefore, it is necessary to simulate the bonding contact force of the film coating on the proppant surface in order to predict and simulate the transport process of film-coated proppant in channel fracturing. Summary of the invention

[0004] In view of the above problems, embodiments of the present invention are proposed to provide a proppant migration simulation method and device based on a CFD-DEM model that overcomes the above problems or at least partially solves the above problems.

[0005] According to one aspect of an embodiment of the present invention, a proppant migration simulation method based on a CFD-DEM model is provided, the method comprising:

[0006] Step S10, obtaining fracture parameters of channel fracturing and basic parameters of coated proppant, and establishing a fracture physical model of proppant transport process;

[0007] Step S20, calculating the simulated fracture mouth flow rate of the fracture physical model according to the pumping displacement and the simulation data of the fracture physical model;

[0008] Step S30, meshing the fracture physical model to obtain a plurality of mesh units;

[0009] Step S40, constructing a group of control equations for the fracturing liquid phase to determine the transport process of the coated proppant; the group of control equations for the fracturing liquid phase includes a continuity equation and a momentum conservation equation;

[0010] Step S50, calculating the fluid velocity in each grid cell based on the time step;

[0011] Step S60, solving the linear velocity and angular velocity of the coated proppant according to the motion equation of the coated proppant and the contact force equation of the coated proppant;

[0012] Step S70, inputting the simulated seam flow velocity, the fluid velocity in each grid unit, the linear velocity and the angular velocity of the coated proppant into the finite element analysis software, and performing proppant migration simulation based on the CFD-DEM model;

[0013] Step S80, calculating the total volume of the sand bank according to the coated proppant conveying process, and calculating the channel rate according to the total volume of the sand bank;

[0014] Step S90, adjusting the pumping displacement, repeating steps S20-S80 to perform proppant migration simulation to obtain the channel rate corresponding to each pumping displacement, and taking the pumping displacement corresponding to the maximum channel rate as the optimal pumping displacement.

[0015] According to another aspect of an embodiment of the present invention, a proppant migration simulation device based on a CFD-DEM model is provided, comprising:

[0016] Model building module, suitable for obtaining fracture parameters of channel fracturing and basic parameters of coated proppant, and building fracture physical model of proppant transport process;

[0017] A slot flow rate module, adapted to calculate the simulated slot flow rate of the fracture physical model according to the pumping displacement and the simulation data of the fracture physical model;

[0018] A meshing module, suitable for meshing the fracture physical model to obtain multiple mesh units;

[0019] The transport process module is suitable for constructing a set of control equations for the fracturing liquid phase to determine the transport process of the coated proppant; the set of control equations for the fracturing liquid phase includes a continuity equation and a momentum conservation equation;

[0020] Fluid velocity module, suitable for calculating the fluid velocity in each grid cell based on the time step;

[0021] Linear angular velocity module, suitable for solving the linear velocity and angular velocity of the coated proppant according to the motion equation of the coated proppant and the contact force equation of the coated proppant;

[0022] A simulation module, suitable for inputting the simulated seam flow velocity, the fluid velocity in each grid unit, the linear velocity and angular velocity of the coated proppant into the finite element analysis software, and performing proppant migration simulation based on the CFD-DEM model;

[0023] A channel rate module, which is suitable for calculating the total volume of the sand bank according to the transport process of the coated proppant, and calculating the channel rate according to the total volume of the sand bank;

[0024] The adjustment module is suitable for adjusting the pumping displacement, and repeatedly executes the seam flow rate module-channel rate module to simulate the proppant migration to obtain the channel rate corresponding to each pumping displacement, and the pumping displacement corresponding to the maximum channel rate is used as the optimal pumping displacement.

[0025] According to another aspect of an embodiment of the present invention, there is provided a computing device, comprising: a processor, a memory, a communication interface and a communication bus, wherein the processor, the memory and the communication interface communicate with each other via the communication bus;

[0026] The memory is used to store at least one executable instruction, and the executable instruction enables the processor to execute operations corresponding to the above-mentioned proppant migration simulation method based on the CFD-DEM model.

[0027] According to another aspect of an embodiment of the present invention, a computer storage medium is provided, wherein the storage medium stores at least one executable instruction, and the executable instruction enables a processor to perform operations corresponding to the above-mentioned proppant migration simulation method based on the CFD-DEM model.

[0028] According to another aspect of an embodiment of the present invention, a computer program product is provided, comprising at least one executable instruction, wherein the executable instruction enables a processor to perform operations corresponding to the above-mentioned proppant migration simulation method based on the CFD-DEM model.

[0029] According to the proppant migration simulation method and device based on the CFD-DEM model provided by the embodiment of the present invention, the actual fracture parameters of the channel fracturing and the basic parameters of the coated proppant are obtained to establish a fracture physical model of the proppant transportation process, the pumping displacement is converted to the simulated seam flow rate, the grid units are divided, the discrete fracturing liquid phase control equations are determined to determine the transportation process, the fluid velocity is solved, the linear velocity and angular velocity of the coated proppant are solved, the migration and laying are carried out based on the CFD-DEM model, the total volume of the sand bank and the channel rate are calculated, the pumping displacement is changed and the calculation is repeated to determine the optimal pumping displacement. By introducing the contact force of the coated proppant, the transportation process of the coated proppant of the channel fracturing is predicted and simulated, so that the simulation results are consistent with the actual situation, and a basis is provided for the optimization of the construction parameters of the channel fracturing.

[0030] The above description is only an overview of the technical solution of the embodiment of the present invention. In order to more clearly understand the technical means of the embodiment of the present invention, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the embodiment of the present invention more obvious and easy to understand, the specific implementation method of the embodiment of the present invention is specifically listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the embodiments of the present invention. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0032] Figure 1 A flow chart of a proppant migration simulation method based on a CFD-DEM model according to an embodiment of the present invention is shown;

[0033] Figure 2 A schematic diagram of the Hertz-Mindlin (no-slip) contact model for multi-spherical particles is shown;

[0034] Figure 3 A comparison chart of the sand bank passage rate of the coated proppant in the fracture and the passage rate of the physical experiment is shown;

[0035] Figure 4 The schematic diagram of the distribution of coated proppant in the seam under different pumping rates is shown;

[0036] Figure 5 A schematic diagram showing the effect of different pumping rates on the channel rate of sand bank formed by coated proppant;

[0037] Figure 6 A schematic structural diagram of a proppant migration simulation device based on a CFD-DEM model according to an embodiment of the present invention is shown;

[0038] Figure 7 A schematic diagram of the structure of a computing device according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0039] The exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present invention and to enable the scope of the present invention to be fully communicated to those skilled in the art.

[0040] First, the terms involved in one or more embodiments of the present application are explained.

[0041] CFD (Computational Fluid Dynamics) model: used to simulate and analyze fluid flow phenomena. CFD models approximate actual fluid flow conditions by numerically solving the differential equations that control fluid flow.

[0042] DEM (Digital Elevation Model) model: A digital simulation of the ground terrain is achieved through limited terrain elevation data. DEM is a physical ground model that represents the ground elevation in the form of a set of ordered numerical arrays (X, Y and Z). By discretizing the earth's surface into regular grids, the elevation value corresponding to each grid point is the altitude of the terrain surface.

[0043] The Navier-Stokes equations (NS equations for short) are a set of partial differential equations that describe the motion of viscous fluids, which were independently derived by Claude-Louis Navier and George Gabriel Stokes in 1821 and 1845 respectively. The NS equations reflect the basic mechanical laws of the flow of viscous fluids (also known as real fluids).

[0044] Figure 1 FIG. 4 shows a flow chart of a proppant migration simulation method based on a CFD-DEM model according to an embodiment of the present invention. Figure 1 As shown, the method comprises the following steps:

[0045] Step S10, obtaining fracture parameters of channel fracturing and basic parameters of coated proppant, and establishing a fracture physical model of the proppant transport process.

[0046] According to the actual operation conditions, the fracture parameters of the channel fracturing and the basic parameters of the coated proppant during the actual operation can be obtained. The fracture parameters include fracture height, fracture width, fracture length, fracture shear modulus, fracture Poisson's ratio, etc. The basic parameters of the coated proppant include the density of the coated proppant, the diameter of the coated proppant, the volume concentration of the coated proppant, the shear modulus of the coated proppant, the Poisson's ratio of the coated proppant, etc.

[0047] A fracture physical model of proppant transport process can be established based on similarity criteria.

[0048] Step S20, calculating the simulated fracture mouth flow rate of the fracture physical model according to the pumping displacement and the simulation data of the fracture physical model.

[0049] According to the pumping displacement and the simulation data of the fracture physical model, the simulated fracture mouth flow rate of the fracture physical model can be calculated as follows:

[0050]

[0051] Among them, Q 1 is the pumping displacement, which is determined according to the actual operation conditions; h 1 The crack height and W are the crack parameters. f1 The crack width and h are the crack parameters. 2 is the simulated fracture height of the fracture physical model, W f2 is the simulated peak width of the crack physical model, v 2 is the simulated fracture mouth flow velocity of the fracture physical model, which is calculated based on the similarity criterion.

[0052] Step S30, meshing the fracture physical model to obtain a plurality of mesh units.

[0053] The flow field controls the volume discretization, and the fracture physical model is meshed. Specifically, it can be divided into hexahedral meshes. For example, 100, 2, and 30 meshes are sequentially divided in each direction of the fracture physical model with a length, width, and height of 300×2×60mm. The total number of meshes is 6000, and the sizes of the length, width, and height of each mesh do not need to be the same. The above data are for example, and are set according to the implementation situation, and are not limited here.

[0054] Step S40, constructing a group of control equations of the fracturing fluid phase to determine the transport process of the coated proppant.

[0055] In the Euler framework, based on the continuous medium hypothesis, the Navier-Stokes control equation is used to determine the transport process of the coated proppant, and the control equations of the fracturing liquid phase in the transport process of the coated proppant are established. The control equations of the fracturing liquid phase include the continuity equation and the momentum conservation equation, which are used to determine the transport process of the coated proppant.

[0056] The control equations of the fracturing fluid phase are as follows:

[0057]

[0058]

[0059]

[0060]

[0061] Among them, ρ l is the density of the fracturing fluid phase; ε l is the volume fraction of fracturing liquid phase; is the movement velocity of the fracturing liquid phase; P is the flow field pressure; is the stress in the fracturing fluid phase; μ l is the viscosity coefficient of the fracturing fluid phase; g is the gravitational acceleration; is the momentum exchange term between the fracturing fluid phase and the coated proppant phase; V p,i is the volume of the coated proppant i. In this embodiment, the coated proppant is the proppant in the no-slip contact model. The volume of each coated proppant i is accumulated to calculate ε l ; V cell is the volume of the grid cell of the local fluid.

[0062] The momentum exchange term between the fracturing liquid phase and the coated proppant phase realizes the two-phase momentum exchange through the liquid-solid phase momentum exchange source term, that is, the force of the particles on the fluid is equivalent to the reaction force of the fluid on the particle drag force. Based on the Gidaspow drag model, the liquid-solid two-phase momentum exchange is realized as shown below:

[0063]

[0064]

[0065]

[0066]

[0067]

[0068] in, is the momentum exchange term between the fracturing fluid phase and the coated proppant phase, N is the total number of proppant particles in the calculation grid, V cell is the volume of the local fluid grid unit; F drag,i V is the drag force of the fracturing fluid on the coated proppant i; p is the volume fraction of particle phase; ρ f is the proppant density; η is the two-phase exchange coefficient; C Dis the particle drag coefficient; d p is the solid particle diameter; Re is the particle phase Reynolds number; ρ is the fluid density; μ f is the viscosity coefficient of the fluid; ε l is the volume fraction of fracturing liquid phase; μ l is the viscosity coefficient of the fracturing fluid phase; is the velocity of fracturing fluid phase, v p,i is the linear velocity of the coated proppant i, which is subsequently solved according to the motion equation of the coated proppant and the contact force equation of the coated proppant.

[0069] Step S50, calculating the fluid velocity in each grid cell based on the time step.

[0070] SIMPLE algorithm (Semi-Implicit Method for Pressure Linked Equations) is used to solve the fluid velocity in each grid unit at each time step based on the following discrete equations. The discrete equations are constructed based on the density of the fracturing fluid phase, the volume fraction of the fracturing fluid phase, the momentum exchange term between the fracturing fluid phase and the coated proppant phase, and the total area and volume in all directions of the fracture physical model, as shown below:

[0071]

[0072] in, is the fluid velocity in each grid unit at each time step, that is, the movement velocity of the fracturing fluid phase; Δt is the time step, and the specific value can be set according to the implementation situation; ρ l is the density of the fracturing fluid phase; l is the volume fraction of the fracturing liquid phase; A is the total area of ​​the fracture physical model in different directions such as x, y, and z; is the stress under the fracturing liquid phase; P is the flow field pressure; g is the gravitational acceleration; is the momentum exchange term between the fracturing fluid phase and the coated proppant phase; V is the control volume of the fracture physical model.

[0073] Solve the above discrete equations to obtain the fluid velocity in each grid cell at each time step.

[0074] Step S60, solving the motion equation of the coated proppant and the contact force equation of the coated proppant to obtain the linear velocity and angular velocity of the coated proppant.

[0075] Based on the Lagrangian framework and using Newton's second law, the motion equation of the coated proppant particle phase is established, and the linear velocity and angular velocity of the coated proppant are obtained by solving it. The motion equation of the coated proppant is as follows:

[0076]

[0077]

[0078] Among them, m p,i is the mass of coated proppant i, v p,i is the linear velocity of the coated proppant i; F drag,i F is the drag force of the fracturing fluid on the coated proppant i; c is the collision contact force of the coated proppant particles, which is obtained by solving the contact force equation of the coated proppant; I p,i is the moment of inertia of the coated proppant i; w p,i is the angular velocity of the coated proppant i; is the drag torque of the fracturing fluid on the coated proppant i; is the collision contact torque of the coated proppant.

[0079] Based on the multivariate spherical particle contact model, the contact force equation of the coated proppant is established to obtain the collision contact force of the coated proppant particles. The contact force equation of the coated proppant is as follows:

[0080]

[0081] in, is the contact force of the coated proppant, i.e. the contact force between adjacent coated proppant particles i and j, is the normal force between coated proppants i and j; is the normal damping force between coated proppants i and j; is the tangential force between coated proppants i and j; is the tangential damping force between coated proppants i and j; It is the physical adhesion between particles.

[0082] The principle of agglomeration of coated proppants is the solvation effect of the fracturing fluid on the surface resin. When the fracturing fluid penetrates into the surface coated resin, the particles absorb water and gradually soften, changing from the original solid condensed state to the coated viscoelastic state. The surface resin coating hydration layer exhibits a viscoelastic state with a bonding effect, which can enable the coated proppant particle system to maintain an aggregated state. After contact with the fracturing fluid, the softening of the coated proppant mainly occurs within the first ten minutes, and then tends to be stable, which can be expressed by needle penetration. According to the measurement of the bonding force of the heterocyclic coated particles after contact to form agglomerations, the bonding force increases from 1.3mN to 9mN. The multi-spherical particle contact model is as follows Figure 2 As shown, there are three coordinate axes: x, y, and z, where Figure 2 The adjacent coated proppants are recorded as i and j respectively. For example, the green one is coated proppant i, with a radius of R i , red is the coated proppant j, and the radius is R j .

[0083] The normal force between coated proppants i and j and the normal damping force between coated proppants i and j are calculated as follows:

[0084]

[0085]

[0086]

[0087]

[0088]

[0089]

[0090] Among them, E * is the equivalent Young's modulus, E i is the Young's modulus of proppant i; E j is the Young's modulus of proppant j; R * is the equivalent radius of the model particle; R i is the model particle radius of proppant i; R j is the model particle radius of proppant j; v i is the velocity of proppant i; v j is the velocity of proppant j; δ n is the normal overlap; β is the parameter of the restitution coefficient; S n is the normal stiffness; m * is the equivalent mass; is the normal component of the relative velocity; Y * is the yield strength of proppant i; e is the recovery coefficient.

[0091] The calculation of the tangential force between the coated proppants i and j and the tangential damping force between the coated proppants i and j is as follows:

[0092]

[0093]

[0094]

[0095] Among them, S t is the tangential stiffness; δ t is the tangential overlap; β is the parameter of the coefficient of restitution; m * is the equivalent mass; is the tangential component of the relative velocity; R * is the equivalent radius of the model particle; G * is the equivalent tangent modulus.

[0096] The inter-particle bonding force is calculated as follows:

[0097]

[0098]

[0099] Where K is the bonding energy density; R * is the equivalent radius of the model particle; δ n is the normal overlap; P' is the needle penetration value, P' = 7.6118ln(t) + 22.435 is the maximum needle penetration; P max is the maximum flow field pressure; F vismax is the maximum bonding force between particles, 9mN; R max * is the maximum value of the equivalent radius of the model particle; δ nmax is the maximum value of normal overlap.

[0100] After the contact force of the coated proppant is obtained by solving the above formula, it is substituted into the motion equation of the coated proppant to obtain the linear velocity and angular velocity of the coated proppant.

[0101] Step S70, inputting the simulated seam flow velocity, the fluid velocity in each grid unit, the linear velocity and the angular velocity of the coated proppant into the finite element analysis software, and performing proppant migration simulation based on the CFD-DEM model.

[0102] The simulated seam flow velocity, the fluid velocity in each grid unit, the linear velocity and the angular velocity of the coated proppant obtained by solving steps S20-S60 are input into the finite element analysis software Fluent, and the proppant migration simulation is performed based on the CFD-DEM model.

[0103] Take a channel fracturing well in a certain block as an example. The fracture length of the well is 150m, the fracture height is 30m, and the fracture width is 2mm. The model width is consistent with the actual fracture width. The fracture length and fracture height are geometrically similar. A small-scale rectangular flat plate model with a length of 300mm, a height of 60mm, and a width of 2mm is established to characterize the fracture. The flow condition meets the Reynolds number similarity criterion. According to the basic parameters such as the fracture morphology formed by the actual operation of the channel fracturing on site and the properties of the coated proppant used, the pump injection displacement is used to simulate the transport process of the coated proppant in the fracture using the above steps. The total simulation time can be set to 50s, for example, to calculate the transport process of the coated proppant.

[0104] Step S80, calculating the total volume of the sand bank according to the coated proppant conveying process, and calculating the channel rate according to the total volume of the sand bank.

[0105] According to the sand bank of the cracks formed during the transport of the coated proppant, the channel rate of each sand bank is further calculated. Specifically, the total volume of the sand bank is calculated according to the left boundary grid, right boundary grid, grid length, height from the boundary grid of the sand bank to the lower end of the crack, and simulated crack width during the transport of the coated proppant, as shown below:

[0106]

[0107] Among them, V t is the total volume of the sand bank; g L , g R are the left and right boundary grids of the sand bank respectively; l is the grid length; H is the height from the boundary grid of the sand bank to the lower end of the crack; w is the crack width. The above parameters can be obtained based on finite element analysis software.

[0108] The channel ratio is calculated based on the total volume of the sand bank, the volume of all particles that make up the sand bank, and the porosity of the accumulated particles as follows:

[0109]

[0110] Where C is the channel rate; V t is the total volume of the sand bank; V p is the volume of all particles constituting the sand bank; ε is the porosity of the particles when stacked, which is taken as 0.6.

[0111] like Figure 3 As shown, when the proppant migration simulation is performed, sand banks are formed in the cracks, and the positions of the sand banks are respectively the front, middle, tail, and average positions. The channel rate simulated by the present invention is similar to the channel rate obtained by physical experiments, thereby verifying the correctness and accuracy of the present invention.

[0112] Step S90, adjusting the pumping displacement, repeating steps S20-S80 to perform proppant migration simulation to obtain the channel rate corresponding to each pumping displacement, and taking the pumping displacement corresponding to the maximum channel rate as the optimal pumping displacement.

[0113] When the simulation time is 15s, the distribution of the coated proppant in the fracture is different for different pumping rates. Figure 4 As shown in the figure, the pump displacement Q is Q = 4m 3 / min, Q=5m 3 / min, Q=6m 3 / min, Q=7m 3 / min, the distribution of coated proppant in the fracture. The pumping displacement determines the migration speed of the coated proppant and the formation of coated proppant clusters, and the effect is obvious. The channel rate is calculated based on the final distribution of the coated proppant in the fracture within the simulation time of 50s, as shown in Figure 5As shown, the horizontal axis is the pumping displacement, and the vertical axis is the channel rate. The channel rate increases first and then decreases with the increase of the pumping displacement. This is because when the injection speed is low, the liquid sand carrying capacity is limited, and most of the particles settle at the front end and adhere to the surface of the sand bank, so that the coated proppant clusters that migrate to the fingertips of the sand bank are small, and the channel area formed by accumulation is also small. At high flow rates, although the fluidization effect of the liquid on the settled clusters is enhanced, the erosion of the settled cluster sand bank by the fracturing fluid also increases accordingly, which compacts the pores at the front end of the sand bank, resulting in a decrease in the channel rate. Therefore, too high a pumping displacement is not conducive to the transport of the coated proppant. Considering the above problems, the proppant migration simulation can be performed by adjusting the pumping displacement and repeating steps S20-S80 to obtain the channel rate corresponding to each different pumping displacement. Compare the channel rates, and take the pumping displacement corresponding to the maximum channel rate as the optimal pumping displacement to improve the transport of the coated proppant.

[0114] According to the proppant migration simulation method based on the CFD-DEM model provided by the embodiment of the present invention, the fracture parameters of the actual channel fracturing and the basic parameters of the coated proppant are obtained to establish a fracture physical model of the proppant transportation process, the pumping displacement is converted to the simulated seam flow rate, the grid units are divided, the discrete fracturing liquid phase control equations are determined to determine the transportation process, the fluid velocity is solved, the linear velocity and angular velocity of the coated proppant are solved, the migration and laying are carried out based on the CFD-DEM model, the total volume of the sand bank and the channel rate are calculated, the pumping displacement is changed and the calculation is repeated to determine the optimal pumping displacement. By introducing the contact force of the coated proppant, the transportation process of the coated proppant of the channel fracturing is predicted and simulated, so that the simulation results are consistent with the actual situation, providing a basis for the optimization of the channel fracturing construction parameters.

[0115] Figure 6 FIG. 1 shows a schematic diagram of the structure of a proppant migration simulation device based on a CFD-DEM model provided by an embodiment of the present invention. Figure 6 As shown, the device comprises:

[0116] Model building module 610, adapted to obtain fracture parameters of channel fracturing and basic parameters of coated proppant, and to establish a fracture physical model of proppant transport process;

[0117] The slot flow rate module 620 is adapted to calculate the simulated slot flow rate of the fracture physical model according to the pumping displacement and the simulation data of the fracture physical model;

[0118] A meshing module 630 is adapted to mesh the fracture physical model to obtain a plurality of mesh units;

[0119] The transport process module 640 is adapted to construct a set of control equations for the fracturing fluid phase to determine the transport process of the coated proppant; the set of control equations for the fracturing fluid phase includes a continuity equation and a momentum conservation equation;

[0120] A fluid velocity module 650, adapted to calculate the fluid velocity within each grid cell based on a time step;

[0121] Linear angular velocity module 660, adapted to obtain the linear velocity and angular velocity of the coated proppant according to the equation of motion of the coated proppant and the contact force equation of the coated proppant;

[0122] A simulation module 670, adapted to input the simulated seam flow velocity, the fluid velocity in each grid cell, the linear velocity and the angular velocity of the coated proppant into the finite element analysis software, and perform proppant migration simulation based on the CFD-DEM model;

[0123] A channel rate module 680 is adapted to calculate the total volume of the sand bank according to the coated proppant delivery process, and calculate the channel rate according to the total volume of the sand bank;

[0124] The adjustment module 690 is suitable for adjusting the pumping displacement, and repeatedly executes the slot flow rate module 620-channel rate module 680 to perform proppant migration simulation to obtain the channel rate corresponding to each pumping displacement, and takes the pumping displacement corresponding to the maximum channel rate as the optimal pumping displacement.

[0125] Optionally, the model building module 610 is further adapted to:

[0126] Obtain the fracture parameters of channel fracturing and the basic parameters of the coated proppant, the fracture parameters include fracture height, fracture width, fracture length, fracture shear modulus, and fracture Poisson's ratio; the basic parameters of the coated proppant include coated proppant density, coated proppant diameter, coated proppant volume concentration, coated proppant shear modulus, and coated proppant Poisson's ratio;

[0127] A fracture physical model of proppant transport process is established based on similarity criteria.

[0128] Optionally, the slot flow rate module 620 is further adapted to:

[0129] According to the pumping displacement, fracture height and width of fracture parameters, simulated fracture height and simulated peak width of the fracture physical model, the simulated fracture mouth flow rate of the fracture physical model is calculated based on the similarity criterion.

[0130] Optionally, the fluid velocity module 650 is further adapted to:

[0131] The semi-implicit method of the pressure coupling equations is used to solve the fluid velocity in each grid unit at each time step based on the discrete equations; the discrete equations are constructed according to the fracturing fluid phase density, fracturing fluid phase volume fraction, the momentum exchange term between the fracturing fluid phase and the coated proppant phase, the total area in all directions of the fracture physical model, and the control volume.

[0132] Optionally, the linear angular velocity module 660 is further adapted to:

[0133] Based on the multi-element spherical particle contact model, the contact force equation of the coated proppant is established, and the collision contact force of the coated proppant particles is obtained;

[0134] The phase motion equation of the coated proppant particles is established based on the Lagrangian framework and Newton's second law. The linear velocity and angular velocity of the coated proppant are solved according to the collision contact force of the coated proppant particles.

[0135] Optionally, the channel rate module 680 is further adapted to:

[0136] The total volume of the sand bank is calculated according to the left boundary grid, right boundary grid, grid length, height from the boundary grid of the sand bank to the lower end of the crack, and simulated crack width during the transport of the coated proppant.

[0137] The channel ratio was calculated based on the total volume of the sand bank, the volume of all particles constituting the sand bank, and the porosity of the deposited particles.

[0138] The description of each module above refers to the corresponding description in the method embodiment and will not be repeated here.

[0139] An embodiment of the present invention further provides a non-volatile computer storage medium, which stores at least one executable instruction, and the executable instruction can execute operations corresponding to the proppant migration simulation method based on the CFD-DEM model in any of the above method embodiments.

[0140] An embodiment of the present application provides a computer program product, which includes at least one executable instruction or computer program, which enables a processor to perform operations corresponding to the proppant migration simulation method based on the CFD-DEM model in any of the above-mentioned method embodiments.

[0141] Figure 7 A schematic diagram of the structure of a computing device according to an embodiment of the present invention is shown, and the specific implementation of the embodiment of the present invention does not limit the specific implementation of the computing device.

[0142] like Figure 7 As shown, the computing device may include: a processor 702 , a communication interface 704 , a memory 706 , and a communication bus 708 .

[0143] in:

[0144] The processor 702 , the communication interface 704 , and the memory 706 communicate with each other via a communication bus 708 .

[0145] The communication interface 704 is used to communicate with other devices such as clients or other servers.

[0146] The processor 702 is used to execute the program 710, and specifically can execute the relevant steps in the above-mentioned embodiment of the proppant migration simulation method based on the CFD-DEM model.

[0147] Specifically, the program 710 may include program codes, which include computer operation instructions.

[0148] The processor 702 may be a central processing unit (CPU), or an application-specific integrated circuit (ASIC), or one or more integrated circuits configured to implement the embodiments of the present invention. The one or more processors included in the computing device may be processors of the same type, such as one or more CPUs; or processors of different types, such as one or more CPUs and one or more ASICs.

[0149] The memory 706 is used to store the program 710. The memory 706 may include a high-speed RAM memory, and may also include a non-volatile memory (non-volatile memory), such as at least one disk memory.

[0150] Program 710 can be specifically used to enable processor 702 to execute the proppant migration simulation method based on CFD-DEM model in any of the above method embodiments. The specific implementation of each step in program 710 can refer to the corresponding description in the corresponding steps and units in the above proppant migration simulation embodiment based on CFD-DEM model, which will not be repeated here. Those skilled in the art can clearly understand that for the convenience and simplicity of description, the specific working process of the above-described equipment and modules can refer to the corresponding process description in the above-mentioned method embodiment, which will not be repeated here.

[0151] The algorithm or display provided herein is not inherently related to any particular computer, virtual system or other device. Various general purpose systems can also be used together with the teachings based on this. According to the above description, it is obvious that the structure required for constructing such systems. In addition, the embodiment of the present invention is not directed to any specific programming language either. It should be understood that various programming languages ​​can be utilized to realize the content of the embodiment of the present invention described herein, and the description of the above specific language is to disclose the preferred implementation of the embodiment of the present invention.

[0152] In the description provided herein, a large number of specific details are described. However, it is understood that embodiments of the present invention can be practiced without these specific details. In some instances, well-known methods, structures and techniques are not shown in detail so as not to obscure the understanding of this description.

[0153] Similarly, it should be understood that in order to streamline the embodiments of the present invention and to aid in understanding one or more of the various inventive aspects, in the above description of the exemplary embodiments of the present invention, the various features of the embodiments of the present invention are sometimes grouped together into a single embodiment, figure, or description thereof. However, the disclosed method should not be interpreted as reflecting the following intention: that the claimed embodiments of the present invention require more features than the features explicitly recited in each claim. More specifically, as reflected in the claims below, the inventive aspects lie in less than all the features of the single embodiment disclosed above. Therefore, the claims that follow the specific embodiment are hereby expressly incorporated into the specific embodiment, wherein each claim itself serves as a separate embodiment of the present invention.

[0154] Those skilled in the art will appreciate that the modules in the devices in the embodiments may be adaptively changed and arranged in one or more devices different from the embodiments. The modules or units or components in the embodiments may be combined into one module or unit or component, and in addition they may be divided into a plurality of submodules or subunits or subcomponents. Except that at least some of such features and / or processes or units are mutually exclusive, all features disclosed in this specification (including the accompanying claims, abstracts and drawings) and all processes or units of any method or device disclosed in this manner may be combined in any combination. Unless otherwise expressly stated, each feature disclosed in this specification (including the accompanying claims, abstracts and drawings) may be replaced by an alternative feature providing the same, equivalent or similar purpose.

[0155] In addition, those skilled in the art will appreciate that, although some embodiments herein include certain features included in other embodiments but not other features, the combination of features of different embodiments is meant to be within the scope of the present invention and form different embodiments. For example, in the claims below, any one of the claimed embodiments may be used in any combination.

[0156] Each component embodiment of the present invention can be implemented in hardware, or in software modules running on one or more processors, or in a combination thereof. Those skilled in the art should understand that a microprocessor or a digital signal processor (DSP) can be used in practice to implement some or all of the functions of some or all of the components according to the embodiments of the present invention. Embodiments of the present invention can also be implemented as a device or apparatus program (e.g., a computer program and a computer program product) for executing part or all of the methods described herein. Such a program implementing embodiments of the present invention can be stored on a computer-readable medium, or can be in the form of one or more signals. Such signals can be downloaded from an Internet website, or provided on a carrier signal, or in any other form.

[0157] It should be noted that the above embodiments illustrate the embodiments of the present invention rather than limit the present invention, and those skilled in the art can design alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word "comprising" does not exclude the presence of elements or steps not listed in the claim. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. Embodiments of the present invention can be implemented by means of hardware including several different elements and by means of a suitably programmed computer. In the unit claims listing several devices, several of these devices can be embodied by the same item of hardware. The use of the words first, second, and third, etc. does not denote any order. These words can be interpreted as names. The steps in the above embodiments, unless otherwise specified, should not be construed as limiting the order of execution.

Claims

1. A proppant migration simulation method based on CFD-DEM model, characterized in that: Methods include: Step S10, obtaining fracture parameters of channel fracturing and basic parameters of coated proppant, and establishing a fracture physical model of proppant transport process; Step S20, calculating the simulated seam flow rate of the fracture physical model according to the pumping displacement and the simulation data of the fracture physical model; Step S30, meshing the fracture physical model to obtain a plurality of mesh units; Step S40, constructing a group of control equations for the fracturing liquid phase to determine the transport process of the coated proppant; the group of control equations for the fracturing liquid phase includes a continuity equation and a momentum conservation equation; Step S50, calculating the fluid velocity in each grid cell based on the time step; Step S60, solving the linear velocity and angular velocity of the coated proppant according to the motion equation of the coated proppant and the contact force equation of the coated proppant; Step S70, inputting the simulated seam flow velocity, the fluid velocity in each grid unit, the linear velocity and the angular velocity of the coated proppant into the finite element analysis software, and performing proppant migration simulation based on the CFD-DEM model; Step S80, calculating the total volume of the sand bank according to the coated proppant conveying process, and calculating the channel rate according to the total volume of the sand bank; Step S90, adjusting the pumping displacement, repeating steps S20-S80 to perform proppant migration simulation to obtain the channel rate corresponding to each pumping displacement, and taking the pumping displacement corresponding to the maximum channel rate as the optimal pumping displacement.

2. The method according to claim 1, characterized in that The method of obtaining the fracture parameters of the channel fracturing and the basic parameters of the coated proppant and establishing the fracture physical model of the proppant transport process further includes: Obtaining the fracture parameters of the channel fracturing and the basic parameters of the coated proppant, wherein the fracture parameters include fracture height, fracture width, fracture length, fracture shear modulus, and fracture Poisson's ratio; the basic parameters of the coated proppant include coated proppant density, coated proppant diameter, coated proppant volume concentration, coated proppant shear modulus, and coated proppant Poisson's ratio; A fracture physical model of proppant transport process is established based on similarity criteria.

3. The method according to claim 1, characterized in that The step of calculating the simulated seam flow rate of the fracture physical model according to the pumping displacement and the simulation data of the fracture physical model further comprises: The simulated fracture mouth flow rate of the fracture physical model is calculated based on the similarity criterion according to the pumping displacement, the fracture height and the fracture width of the fracture parameters, the simulated fracture height and the simulated peak width of the fracture physical model.

4. The method according to claim 1, characterized in that The calculating of the fluid velocity in each grid unit based on the time step further comprises: The semi-implicit method of the pressure coupling equations is used to solve the fluid velocity in each grid unit at each time step based on the discrete equation; the discrete equation is constructed according to the fracturing liquid phase density, the fracturing liquid phase volume fraction, the momentum exchange term between the fracturing liquid phase and the coated proppant phase, the total area in all directions of the fracture physical model, and the control volume.

5. The method according to claim 1, characterized in that The method of solving the linear velocity and angular velocity of the coated proppant according to the coated proppant motion equation and the coated proppant contact force equation further includes: Based on the multi-element spherical particle contact model, the contact force equation of the coated proppant is established, and the collision contact force of the coated proppant particles is obtained; The phase motion equation of the coated proppant particles is established based on the Lagrangian framework and Newton's second law. The linear velocity and angular velocity of the coated proppant are obtained according to the collision contact force of the coated proppant particles.

6. The method according to claim 1, characterized in that The method of calculating the total volume of the sand bank according to the coated proppant conveying process and calculating the channel rate according to the total volume of the sand bank further includes: The total volume of the sand bank is calculated according to the left boundary grid, right boundary grid, grid length, height from the boundary grid of the sand bank to the lower end of the crack, and simulated crack width during the transportation of the coated proppant. The channel ratio is calculated based on the total volume of the sand bank, the volume of all particles constituting the sand bank, and the porosity of the deposited particles.

7. A proppant migration simulation device based on CFD-DEM model, characterized in that: The device includes: Model building module, suitable for obtaining fracture parameters of channel fracturing and basic parameters of coated proppant, and building fracture physical model of proppant transport process; A slot flow rate module, adapted to calculate the simulated slot flow rate of the fracture physical model according to the pumping displacement and the simulation data of the fracture physical model; A grid division module, adapted to perform grid division on the fracture physical model to obtain a plurality of grid units; A transport process module, adapted to construct a set of control equations for the fracturing liquid phase to determine the transport process of the coated proppant; the set of control equations for the fracturing liquid phase includes a continuity equation and a momentum conservation equation; Fluid velocity module, suitable for calculating the fluid velocity in each grid cell based on the time step; Linear angular velocity module, suitable for solving the linear velocity and angular velocity of the coated proppant according to the motion equation of the coated proppant and the contact force equation of the coated proppant; A simulation module, adapted to input the simulated seam flow velocity, the fluid velocity in each grid unit, the linear velocity and the angular velocity of the coated proppant into a finite element analysis software, and perform proppant migration simulation based on a CFD-DEM model; A channel rate module, adapted to calculate the total volume of the sand bank according to the coated proppant conveying process, and calculate the channel rate according to the total volume of the sand bank; The adjustment module is suitable for adjusting the pumping displacement, repeatedly executing the slot flow rate module-the channel rate module to perform proppant migration simulation to obtain the channel rate corresponding to each pumping displacement, and taking the pumping displacement corresponding to the maximum channel rate as the optimal pumping displacement.

8. A computing device, characterized in that include: A processor, a memory, a communication interface and a communication bus, wherein the processor, the memory and the communication interface communicate with each other via the communication bus; The memory is used to store at least one executable instruction, and the executable instruction enables the processor to perform operations corresponding to the proppant migration simulation method based on the CFD-DEM model as described in any one of claims 1-6.

9. A computer storage medium, characterized in that: The storage medium stores at least one executable instruction, and the executable instruction enables the processor to execute operations corresponding to the proppant migration simulation method based on the CFD-DEM model as described in any one of claims 1 to 6.

10. A computer program product, characterized in that The method comprises at least one executable instruction, wherein the executable instruction enables a processor to execute operations corresponding to the proppant migration simulation method based on a CFD-DEM model as described in any one of claims 1 to 6.

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