Three-dimensional well pattern collaborative fracturing simulation method

Abstract

The present application provides a three-dimensional well network collaborative fracturing simulation method, which relates to the field of oil and gas development technology. The method includes: obtaining the basic parameters of the target reservoir to establish a three-dimensional well network collaborative fracturing model; assigning the basic parameters to the structured fracture grid unit in the three-dimensional network collaborative fracturing model, obtaining the length of the fracture grid unit and the fracture expansion speed to determine the corresponding simulation time step; in each simulation time step, performing a fracturing numerical simulation on the fracturing section of the fracturing well in each well section; after determining that all well sections of the three-dimensional well network have completed the numerical simulation, output the fracturing simulation results of all well sections in the three-dimensional well network, wherein the fracturing simulation results include the fracture expansion morphology, proppant laying morphology, reservoir transformation volume, effective reservoir transformation volume and fracturing induced stress field distribution. The method provided by the present application achieves the technical effect of improving the efficiency of three-dimensional well network collaborative fracturing.

Description

Technical Field

[0001] The present application relates to the technical field of oil and gas development, and in particular to a three-dimensional well network collaborative fracturing simulation method. Background Art

[0002] Horizontal drilling combined with hydraulic fracturing completion is a key technology for the efficient development of unconventional oil and gas reservoirs. In order to expand the available reserves from the local scale of a single well to the global scale of multiple wells or even the entire oil and gas field development, and to improve the oil production rate and recovery rate, the traditional single well fracturing development has gradually shifted to the "multi-layer three-dimensional well network collaborative fracturing development mode", and the three-dimensional well network collaborative fracturing simulation has become a direction with application prospects.

[0003] In the existing technology, the three-dimensional well network collaborative fracturing process is to arrange multiple horizontal wells in the same oil and gas block in a three-dimensional manner, and carry out fracturing and completion operations in each well section in a certain sequence. The purpose is to increase the reservoir transformation volume from a single well or a single layer to a three-dimensional full reservoir scale.

[0004] In the prior art, the stress interference between wells in three-dimensional well network coordinated fracturing is highly complex, and the uncertainty of crack expansion and proppant laying morphology is large. This cannot meet the needs of efficient development of oil and gas reservoirs, and there is a technical problem of low efficiency of three-dimensional well network coordinated fracturing. Summary of the invention

[0005] The present application provides a three-dimensional well network collaborative fracturing simulation method to solve the technical problem of low efficiency of three-dimensional well network collaborative fracturing simulation.

[0006] In a first aspect, the present application provides a three-dimensional well pattern collaborative fracturing simulation method, comprising:

[0007] Obtaining basic parameters of the target reservoir to establish a three-dimensional well pattern collaborative fracturing model; wherein the basic parameters include target reservoir thickness, geomechanical parameters, fracturing construction parameters and penetration distance;

[0008] Assigning basic parameters to the structured fracture grid units in the three-dimensional network collaborative fracturing model, obtaining the length of the fracture grid units and the fracture propagation speed, so as to determine the corresponding simulation time step, wherein the simulation time step is used to indicate the time step of the fracturing simulation process;

[0009] In each simulation time step, a fracturing numerical simulation is performed on the fracturing section of the fracturing well in each well section of the three-dimensional well network, wherein the three-dimensional well network corresponds to multiple fracturing wells, and each fracturing well corresponds to multiple fracturing sections;

[0010] After confirming that all well sections in the three-dimensional well network have completed the fracturing numerical simulation, the fracturing simulation results of all well sections in the three-dimensional well network are output, wherein the fracturing simulation results include the fracture extension morphology, proppant laying morphology, reservoir transformation volume, effective reservoir transformation volume and fracturing induced stress field distribution.

[0011] Optionally, within each simulation time step, a fracturing numerical simulation is performed on the fracturing section of the fracturing well in each well section of the three-dimensional well network, including:

[0012] According to the crack grid unit, the displacement of the crack tip grid unit in the current time step is obtained to determine the crack extension morphology;

[0013] According to the spatial coordinates of the fracture tip grid of the current time step, the merging status of the fracture grid unit is obtained, and according to the displacement of the fracture grid unit of the current time step and the merging status of the fracture grid unit, the target fracture fluid pressure in the fracture grid unit is obtained;

[0014] Determine the proppant volume fraction corresponding to the fracture grid unit according to the fracture propagation morphology, the displacement of the fracture tip grid unit and the target fracture fluid pressure, wherein the proppant volume fraction is used to indicate the proppant concentration in the fracture grid unit;

[0015] Obtaining fracture grid cells containing proppant volume fractions in fracture extension morphology, and determining proppant placement morphology according to the fracture grid cells containing proppant volume fractions;

[0016] After determining that the fracturing numerical simulation of the current fracturing stage is completed, the first fracture area of ​​the fracture grid unit is obtained according to the fracture extension morphology, and the reservoir transformation volume is obtained according to the first fracture area and the permeation distance;

[0017] According to the proppant laying form, the second fracture area of ​​the fracture grid unit containing the proppant volume fraction is obtained, and according to the second fracture area and the penetration distance, the effective reservoir transformation volume is obtained;

[0018] According to the proppant volume fraction and the target fracture fluid pressure, the fracture residual width of the fracture grid unit is obtained, and according to the fracture residual width, the corresponding fracturing induced stress field distribution is obtained, wherein the fracturing induced stress field distribution includes induced normal stress and tangential stress distribution.

[0019] Optionally, according to the crack grid unit, the displacement of the crack tip grid unit at the current time step is obtained to determine the crack extension morphology, including:

[0020] According to the crack grid unit, the displacement of the crack tip grid unit of the current time step is obtained, wherein the displacement of the crack grid unit includes the normal displacement of the crack grid unit and the tangential displacement of the crack grid unit, the normal displacement is used to indicate the current crack width, and the tangential displacement is used to indicate the tangential displacement of the crack in the horizontal direction;

[0021] Obtain the critical value of the normal displacement of the crack tip grid unit at the current time step, compare the normal displacement of the crack grid unit at the current time step with the critical value of the normal displacement, and determine whether the normal displacement of the crack tip grid unit at the current time step exceeds the critical value of the displacement;

[0022] If so, it is determined that the crack has expanded, the crack expansion direction is obtained, and the crack expansion morphology is determined based on the normal displacement and the crack expansion direction.

[0023] Optionally, after obtaining the target fracture fluid pressure in the fracture grid unit according to the fracture grid unit displacement of the current time step and the merging status of the fracture grid units, the method further includes:

[0024] According to the rock mechanical weak plane in the target reservoir, the activation of the rock mechanical weak plane is determined, and the penetration / slip criterion of the interface is established. The rock mechanical weak plane includes the lamination / bedding interface and natural fractures. The penetration / slip criterion of the interface is obtained by the following method:

[0025] τ tip =τ 0 +λ f (σ n -P b )

[0026] Among them, τ tip represents the shear stress at the tip of the rock mechanical weak surface; τ 0 Represents the cementation strength of the rock mechanical weak plane; λ f Represents the friction coefficient of the weak surface of rock mechanics, dimensionless; σ n is the normal stress of the weak surface of rock mechanics; P b is the target fluid pressure in the crack.

[0027] After determining that the laminae / bedding planes are activated, the fluid loss velocity of the bedding planes is obtained. The fluid loss velocity is obtained by:

[0028]

[0029] Among them, C L Bedding plane filtration rate; is the porosity of the bedding, dimensionless; Δy is the length of the filtration zone perpendicular to the bedding direction; w l is the bedding aperture; P lis the fluid pressure at the bedding entrance; u is the fluid viscosity; t is the injection time; t 0 It is the time when the bedding plane starts to filter out.

[0030] After determining that the natural fracture is activated, the extension of the natural fracture is determined according to the mixed fracture intensity factor in the direction of the natural fracture. The extension of the natural fracture is obtained in the following way;

[0031]

[0032] Among them, K eq is the equivalent fracture toughness, θ nf is the intersection angle of the weak plane of natural fracture, K I is the stress intensity factor of mode I crack, K II is the stress intensity factor of type II crack, It is the fracture toughness of the weak plane of natural cracks.

[0033] Optionally, obtaining a target fracture fluid pressure in a fracture grid unit according to the fracture grid unit displacement and the merging status of the fracture grid units in the current time step includes:

[0034] According to the displacement of the mesh unit at the fracture tip of the current time step, the corresponding initial fluid pressure in the fracture is obtained;

[0035] Obtaining the spatial coordinates of the crack tip unit in the crack grid unit, and judging whether the spatial distance between any two target crack units in the crack grid unit is less than the length of the crack grid unit according to the spatial coordinates;

[0036] If so, it is determined that there is a situation where the cracks in the crack grid unit merge and intersect, and the target crack unit is merged to share a space coordinate point;

[0037] If not, it is determined that there is no fracture merging and intersection in the fracture grid unit, and the initial fracture fluid pressure is used as the target fracture fluid pressure.

[0038] Optionally, after merging the target crack units and sharing a space coordinate point, the method further includes:

[0039] The normal displacement of the fracture grid unit at the intersection position is obtained, and the initial fracture fluid pressure is updated according to the normal displacement of the fracture grid unit at the intersection position to obtain the updated target fracture fluid pressure.

[0040] Optionally, after determining the proppant volume fraction corresponding to the fracture grid unit according to the fracture extension morphology, the fracture grid unit displacement and the target fracture fluid pressure, the method further includes:

[0041] Obtaining the pumping volume threshold of the current fracturing stage, and determining whether the proppant volume fraction of the current fracturing stage exceeds the pumping volume threshold;

[0042] If not, the simulation time step is re-determined to repeat the fracturing numerical simulation for the fracturing wells and fracturing sections of each well section in the three-dimensional well network;

[0043] If yes, the fracturing numerical simulation of the current fracturing stage is stopped.

[0044] Optionally, according to the proppant volume fraction and the target fracture fluid pressure, the fracture residual width of the fracture grid unit is obtained, including:

[0045] After determining that the fracturing numerical simulation of the current fracturing stage is finished, the fracture grid units are divided into unpropped fracture units without proppant volume fraction and propped fracture units with proppant volume fraction according to the fracture closure status and proppant volume fraction;

[0046] According to the change of the fluid pressure in the target fracture in the unsupported fracture unit, the changed target fracture fluid pressure is obtained, and according to the supported fracture unit, the extrusion stress corresponding to the proppant sand pile in the supported fracture unit is obtained;

[0047] The residual width of the fracture grid unit is obtained according to the changed target fracture fluid pressure in the unsupported fracture unit and the extrusion stress in the supported fracture unit.

[0048] Optionally, after obtaining the corresponding fracturing induced stress field distribution according to the residual width of the crack, the method further includes:

[0049] When performing fracturing numerical simulation in the next fracturing stage, the fracturing induced stress corresponding to the residual width in the first fracturing fracture is obtained, wherein the first fracturing fracture is the fracture of all fracturing stages before the next fracturing stage;

[0050] According to the fracturing induced stress corresponding to the residual width of the first fracture in the previous fracturing stage and the induced stress of the extended fracture in the next fracturing stage, the target induced stress for the fracture extension in the next fracturing stage is obtained.

[0051] In a second aspect, the present application provides a three-dimensional well pattern collaborative fracturing simulation device, comprising:

[0052] Establishing a module for obtaining basic parameters of the target reservoir to establish a three-dimensional well pattern collaborative fracturing model; wherein the basic parameters include target reservoir thickness, geomechanical parameters, fracturing construction parameters and penetration distance;

[0053] The first processing module is used to assign basic parameters to the structured fracture grid units in the three-dimensional network collaborative fracturing model, obtain the length of the fracture grid unit and the fracture propagation speed, so as to determine the corresponding simulation time step, wherein the simulation time step is used to indicate the time step of the fracturing simulation process;

[0054] The second processing module is used to perform fracturing numerical simulation on the fracturing section of the fracturing well in each well section of the three-dimensional well network within each simulation time step, wherein the three-dimensional well network corresponds to multiple fracturing wells, and each fracturing well corresponds to multiple fracturing sections;

[0055] The output module is used to output the fracturing simulation results of all well sections in the three-dimensional well network after confirming that all well sections in the three-dimensional well network have completed the fracturing numerical simulation, wherein the fracturing simulation results include the fracture extension morphology, proppant laying morphology, reservoir transformation volume, effective reservoir transformation volume and fracturing induced stress field distribution.

[0056] Optionally, the second processing module is further used for:

[0057] According to the crack grid unit, the displacement of the crack tip grid unit in the current time step is obtained to determine the crack extension morphology;

[0058] According to the spatial coordinates of the fracture tip grid of the current time step, the merging status of the fracture grid unit is obtained, and according to the displacement of the fracture grid unit of the current time step and the merging status of the fracture grid unit, the target fracture fluid pressure in the fracture grid unit is obtained;

[0059] Determine the proppant volume fraction corresponding to the fracture grid unit according to the fracture propagation morphology, the displacement of the fracture tip grid unit and the target fracture fluid pressure, wherein the proppant volume fraction is used to indicate the proppant concentration in the fracture grid unit;

[0060] Obtaining fracture grid cells containing proppant volume fractions in fracture extension morphology, and determining proppant placement morphology according to the fracture grid cells containing proppant volume fractions;

[0061] After determining that the fracturing numerical simulation of the current fracturing stage is completed, the first fracture area of ​​the fracture grid unit is obtained according to the fracture extension morphology, and the reservoir transformation volume is obtained according to the first fracture area and the permeation distance;

[0062] According to the proppant laying form, the second fracture area of ​​the fracture grid unit containing the proppant volume fraction is obtained, and according to the second fracture area and the penetration distance, the effective reservoir transformation volume is obtained;

[0063] According to the proppant volume fraction and the target fracture fluid pressure, the fracture residual width of the fracture grid unit is obtained, and according to the fracture residual width, the corresponding fracturing induced stress field distribution is obtained, wherein the fracturing induced stress field distribution includes induced normal stress and tangential stress distribution.

[0064] Optionally, the second processing module is further used for:

[0065] According to the crack grid unit, the displacement of the crack tip grid unit of the current time step is obtained, wherein the displacement of the crack tip grid unit includes the normal displacement of the crack tip grid unit and the tangential displacement of the crack grid unit, the normal displacement is used to indicate the current crack width, and the tangential displacement is used to indicate the tangential displacement of the crack in the horizontal direction;

[0066] Obtaining the critical value of the normal displacement of the crack tip grid unit at the current time step, comparing the normal displacement of the crack tip grid unit at the current time step with the critical value of the normal displacement, and determining whether the normal displacement of the crack tip grid unit at the current time step exceeds the critical value of the displacement;

[0067] If so, it is determined that the crack has expanded, the crack expansion direction is obtained, and the crack expansion morphology is determined based on the normal displacement and the crack expansion direction.

[0068] Optionally, the second processing module is further used for:

[0069] According to the rock mechanical weak plane in the target reservoir, the activation of the rock mechanical weak plane is determined, and the penetration / slip criterion of the interface is established. The rock mechanical weak plane includes the lamination / bedding interface and natural fractures. The penetration / slip criterion of the interface is obtained by the following method:

[0070] τ tip =τ 0 +λ f (σ n -P b )

[0071] Among them, τ tip represents the shear stress at the tip of the rock mechanical weak surface; τ 0 Represents the cementation strength of the rock mechanical weak plane; λ f Represents the friction coefficient of the weak surface of rock mechanics, dimensionless; σ n is the normal stress of the weak surface of rock mechanics; P b is the fluid pressure in the seam;

[0072] After determining that the laminae / bedding planes are activated, the fluid loss velocity of the bedding planes is obtained. The fluid loss velocity is obtained by:

[0073]

[0074] Among them, C L Bedding plane filtration rate; is the porosity of the bedding, dimensionless; Δy is the length of the filtration zone perpendicular to the bedding direction; w l is the bedding aperture; P l is the fluid pressure at the bedding entrance; u is the fluid viscosity; t is the injection time; t 0 is the time when the bedding plane begins to filter out;

[0075] After determining that the natural fracture is activated, the extension of the natural fracture is determined according to the mixed fracture intensity factor in the direction of the natural fracture. The extension of the natural fracture is obtained in the following way:

[0076]

[0077] Among them, K eq is the equivalent fracture toughness, θ nf is the intersection angle of the weak plane of natural fracture, K I is the stress intensity factor of mode I crack, K II is the stress intensity factor of type II crack, It is the fracture toughness of the weak plane of natural cracks.

[0078] Optionally, the second processing module is further used for:

[0079] According to the displacement of the fracture grid unit in the current time step, the corresponding initial fracture fluid pressure is obtained;

[0080] Obtaining the spatial coordinates of the crack tip unit in the crack grid unit, and judging whether the spatial distance between any two target crack units in the crack grid unit is less than the length of the crack grid unit according to the spatial coordinates;

[0081] If so, it is determined that there is a situation where the cracks in the crack grid unit merge and intersect, and the target crack unit is merged to share a space coordinate point;

[0082] If not, it is determined that there is no fracture merging and intersection in the fracture grid unit, and the initial fracture fluid pressure is used as the target fracture fluid pressure.

[0083] Optionally, the second processing module is further used for:

[0084] The normal displacement of the fracture grid unit at the intersection position is obtained, and the initial fracture fluid pressure is updated according to the normal displacement of the fracture grid unit at the intersection position to obtain the updated target fracture fluid pressure.

[0085] Optionally, the second processing module is further used for:

[0086] Obtaining the pumping volume threshold of the current fracturing stage, and determining whether the proppant volume fraction of the current fracturing stage exceeds the pumping volume threshold;

[0087] If not, the simulation time step is re-determined to repeat the fracturing numerical simulation for the fracturing wells and fracturing sections of each well section in the three-dimensional well network;

[0088] If yes, the fracturing numerical simulation of the current fracturing stage is stopped.

[0089] Optionally, the second processing module is further used for:

[0090] After determining that the fracturing numerical simulation of the current fracturing stage is finished, the fracture grid units are divided into unpropped fracture units without proppant volume fraction and propped fracture units with proppant volume fraction according to the fracture closure status and proppant volume fraction;

[0091] According to the change of the fluid pressure in the target fracture in the unsupported fracture unit, the changed target fracture fluid pressure is obtained, and according to the supported fracture unit, the extrusion stress corresponding to the proppant sand pile in the supported fracture unit is obtained;

[0092] The residual width of the fracture grid unit is obtained according to the changed target fracture fluid pressure in the unsupported fracture unit and the extrusion stress in the supported fracture unit.

[0093] Optionally, the second processing module is further used for:

[0094] When performing fracturing numerical simulation in the next fracturing stage, the fracturing induced stress corresponding to the residual width in the first fracturing fracture is obtained, wherein the first fracturing fracture is the fracture of all fracturing stages before the next fracturing stage;

[0095] According to the fracturing induced stress corresponding to the residual width of the first fracture in the previous fracturing stage and the induced stress of the extended fracture in the next fracturing stage, the target induced stress for the fracture extension in the next fracturing stage is obtained.

[0096] In a third aspect, the present application provides a three-dimensional well network collaborative fracturing simulation device, comprising:

[0097] Processor and memory;

[0098] Memory stores computer-executable instructions;

[0099] The processor executes the computer execution instructions stored in the memory, so that the three-dimensional well network collaborative fracturing simulation device executes any one of the three-dimensional well network collaborative fracturing simulation methods in the first aspect.

[0100] In a fourth aspect, the present application provides a computer-readable storage medium, in which computer execution instructions are stored. When the computer execution instructions are executed by a processor, they are used to implement a three-dimensional well network collaborative fracturing simulation method as described in any one of the first aspects.

[0101] In a fifth aspect, the present application provides a computer program product, which, when executed by a processor, is used to implement a three-dimensional well network collaborative fracturing simulation method as described in any one of the first aspects.

[0102] The present application provides a three-dimensional well network collaborative fracturing simulation method, which obtains the basic parameters of the target reservoir to establish a three-dimensional well network collaborative fracturing model; assigns the basic parameters to the structured fracture grid units in the three-dimensional network collaborative fracturing model, obtains the length of the fracture grid units and the fracture propagation speed to determine the corresponding simulation time step; within each simulation time step, performs a fracturing numerical simulation on the fracturing section of the fracturing well in each well section; after determining that all well sections in the three-dimensional well network have completed the numerical simulation, outputs the fracturing simulation results of all well sections in the three-dimensional well network, wherein the fracturing simulation results include the fracture propagation morphology, proppant The laying morphology, reservoir transformation volume, effective reservoir transformation volume and fracturing induced stress field distribution are obtained, so that the hydraulic fracture expansion, proppant migration in the fracture and the evolution of the induced stress field in the multi-layer three-dimensional well network fracturing development process are simulated through the numerical simulation method, which ensures the authenticity and reliability of the simulation results and improves the accuracy of the simulation results. At the same time, the basic parameters can be further optimized through the simulation results to improve the fracturing effect, reduce the development cost of the actual fracturing work, solve the technical problem of low efficiency of three-dimensional well network collaborative fracturing simulation, and achieve the technical effect of improving the efficiency of three-dimensional well network collaborative fracturing simulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0103] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0104] Figure 1 The process of the three-dimensional well network collaborative fracturing simulation method provided in the embodiment of the present application Figure 1 ;

[0105] Figure 2 A schematic diagram of the division of a three-dimensional well pattern fracturing crack grid unit provided in an embodiment of the present application;

[0106] Figure 3 A top view schematic diagram of the three-dimensional well pattern arrangement and coordinated fracturing completion sequence provided in the embodiment of the present application;

[0107] Figure 4 A schematic diagram of the fracture expansion morphology of the three-dimensional well pattern coordinated fracturing provided in the embodiment of the present application;

[0108] Figure 5 A schematic diagram of the proppant placement in the three-dimensional well pattern coordinated hydraulic fracture provided in the embodiment of the present application;

[0109] Figure 6 A schematic diagram of the evolution of the stress field induced by the coordinated fracturing of a three-dimensional well pattern provided in an embodiment of the present application;

[0110] Figure 7 The process of the three-dimensional well network collaborative fracturing simulation method provided in the embodiment of the present application Figure 2 ;

[0111] Figure 8 The process of the three-dimensional well network collaborative fracturing simulation method provided in the embodiment of the present application Figure 3 ;

[0112] Fig. 9 The process of the three-dimensional well network collaborative fracturing simulation method provided in the embodiment of the present application Figure 4 ;

[0113] Fig.10 A schematic diagram of the intersection and merging of crack grid units provided in an embodiment of the present application;

[0114] Fig.11 A schematic diagram of the structure of a three-dimensional well pattern collaborative fracturing simulation device provided in an embodiment of the present application;

[0115] Fig.12 This is a hardware structure diagram of the three-dimensional well network collaborative fracturing simulation device provided in an embodiment of the present application.

[0116] The above drawings have shown clear embodiments of the present application, which will be described in more detail later. These drawings and text descriptions are not intended to limit the scope of the present application in any way, but to illustrate the concept of the present application to those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0117] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The implementations described in the following exemplary embodiments do not represent all implementations consistent with the present application. Instead, they are merely examples of devices and methods consistent with some aspects of the present application as detailed in the appended claims.

[0118] In the prior art, the stress interference between wells in three-dimensional well network coordinated fracturing is highly complex, and the uncertainty of crack expansion and proppant laying morphology is large. This cannot meet the needs of efficient development of oil and gas reservoirs, and there is a technical problem of low efficiency of three-dimensional well network coordinated fracturing.

[0119] The present application provides a three-dimensional well network collaborative fracturing simulation method, which simulates the hydraulic fracture expansion, proppant migration in the fracture and induced stress field evolution in the multi-layer three-dimensional well network fracturing development process through a numerical simulation method, thereby ensuring the authenticity and reliability of the simulation results and improving the accuracy of the simulation results. At the same time, the basic parameters can be further optimized through the simulation results to improve the fracturing effect, reduce the development cost of the actual fracturing work, solve the technical problem of low efficiency of three-dimensional well network collaborative fracturing simulation, and achieve the technical effect of improving the efficiency of three-dimensional well network collaborative fracturing simulation.

[0120] The technical solution of the present application and how the technical solution of the present application solves the above-mentioned technical problems are described in detail below with specific embodiments. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments. The embodiments of the present application will be described below in conjunction with the accompanying drawings.

[0121] Figure 1 The process of the three-dimensional well network collaborative fracturing simulation method provided in the embodiment of the present application Figure 1 .like Figure 1 As shown, the three-dimensional well pattern collaborative fracturing simulation method provided in the embodiment of the present application includes:

[0122] S101, obtaining basic parameters of the target reservoir to establish a three-dimensional well pattern collaborative fracturing model;

[0123] In this embodiment, the basic parameters include target reservoir thickness, geomechanical parameters, fracturing construction parameters and penetration distance. The penetration distance is used to indicate the maximum distance for oil and gas to flow from the target reservoir to the fracture. The three-dimensional well network collaborative fracturing model is a mathematical model constructed by software.

[0124] The basic parameters of the target reservoir, including target reservoir thickness, geomechanical parameters, fracturing construction parameters and penetration distance, are obtained. Based on these basic parameters, a three-dimensional well network collaborative fracturing model corresponding to the target reservoir is established.

[0125] S102, assigning basic parameters to structured fracture grid units in the three-dimensional network collaborative fracturing model, obtaining the length of the fracture grid unit and the fracture propagation speed, so as to determine the corresponding simulation time step;

[0126] In this embodiment, the simulation time step is used to indicate the time step of the fracturing simulation process.

[0127] The schematic diagram of the structured fracture grid unit division in the three-dimensional network collaborative fracturing model is shown in Figure 2 After assigning the basic parameters to the corresponding fracture grid cells, the time step Δt is calculated according to the ratio of the grid cell length to the fracture propagation velocity.

[0128] S103, within each simulation time step, performing a fracturing numerical simulation on the fracturing section of the fracturing well in each well section of the three-dimensional well network;

[0129] In this embodiment, the three-dimensional well pattern corresponds to a plurality of fracturing wells, and each fracturing well corresponds to a plurality of fracturing stages.

[0130] In each pressure simulation time step, the fracturing section of the fracturing well in each well section is numerically simulated according to the fracture grid units in the three-dimensional well network. After the numerical simulation is completed, the fracture extension morphology, proppant laying morphology, fracture transformation volume, effective transformation volume and fracturing induced stress field distribution in the three-dimensional well network are obtained.

[0131] Specifically, in each simulation time step, according to the fracture grid unit, Figure 3 The arrangement of the three-dimensional well network and the coordinated fracturing completion sequence are shown in the figure. The fracturing section of the fracturing wells in each well section of the three-dimensional well network is simulated numerically to obtain the corresponding fracture extension morphology, proppant laying morphology, fracture stimulation volume, effective stimulation volume and fracturing induced stress field distribution.

[0132] S104. After confirming that all well sections in the three-dimensional well network have completed the fracturing numerical simulation, output the fracturing simulation results of all well sections in the three-dimensional well network, wherein the fracturing simulation results include the fracture extension morphology, proppant laying morphology, reservoir transformation volume, effective reservoir transformation volume and fracturing induced stress field distribution.

[0133] After confirming that all well sections in the three-dimensional well network have completed numerical simulation, the fracturing simulation results corresponding to all well sections in the three-dimensional well network are collected and output. Among them, the simulation results of fracture propagation morphology, proppant placement in fractures and induced stress field evolution obtained in the three-dimensional well network are shown as follows: Figure 4 , Figure 5 as well as Figure 6 shown.

[0134] The present application provides a three-dimensional well network collaborative fracturing simulation method, which obtains the basic parameters of the target reservoir to establish a three-dimensional well network collaborative fracturing model; assigns the basic parameters to the structured fracture grid units in the three-dimensional network collaborative fracturing model, obtains the length of the fracture grid units and the fracture propagation speed to determine the corresponding simulation time step; within each simulation time step, performs a fracturing numerical simulation on the fracturing section of the fracturing well in each well section; after determining that all well sections in the three-dimensional well network have completed the numerical simulation, outputs the fracturing simulation results of all well sections in the three-dimensional well network, wherein the fracturing simulation results include the fracture propagation morphology, proppant The laying morphology, reservoir transformation volume, effective reservoir transformation volume and fracturing induced stress field distribution are obtained, so that the hydraulic fracture expansion, proppant migration in the fracture and the evolution of the induced stress field in the multi-layer three-dimensional well network fracturing development process are simulated through the numerical simulation method, which ensures the authenticity and reliability of the simulation results and improves the accuracy of the simulation results. At the same time, the basic parameters can be further optimized through the simulation results to improve the fracturing effect, reduce the development cost of the actual fracturing work, solve the technical problem of low efficiency of three-dimensional well network collaborative fracturing simulation, and achieve the technical effect of improving the efficiency of three-dimensional well network collaborative fracturing simulation.

[0135] Figure 7 The process of the three-dimensional well network collaborative fracturing simulation method provided in the embodiment of the present application Figure 2 .like Figure 7 As shown, this embodiment, based on the above embodiment, describes in detail the fracturing numerical simulation process of the fracturing section of the fracturing well in each well section, including:

[0136] S701, obtaining the displacement of the crack tip grid unit at the current time step according to the crack grid unit to determine the crack extension morphology;

[0137] In this embodiment, the displacement of the crack grid unit includes normal displacement and tangential displacement. The normal displacement is used to indicate the current crack width, and the tangential displacement is used to indicate the tangential displacement in the horizontal direction of the crack. A crack grid unit includes a normal displacement discontinuity and two mutually orthogonal tangential displacement discontinuities.

[0138] According to the fracture grid unit, the normal displacement and tangential displacement of the fracture grid unit in the current time step are calculated by the hydraulic fracture fluid-solid coupling equation. According to the normal displacement and tangential displacement of the current time step obtained, the fracture extension morphology is further determined.

[0139] Specifically, the fluid-solid coupling equations consist of the fluid flow in the fracture and the rock solid deformation equations. The fluid flow in the fracture is represented by the mass conservation equation, and the rock solid deformation is represented by the three-dimensional displacement discontinuity method.

[0140] The mass conservation equation of fluid flow in hydraulic fractures can describe the relationship between the fluid pressure in the fracture and the fracture width:

[0141]

[0142] Where w is the crack width, t is the time, P is the fluid pressure in the crack, C L is the fluid loss rate, Q is the liquid pump displacement, δ is the Kronecker symbol, u is the fluid viscosity, To consider the dimensionless function of proppant concentration on fluid motion, x is the coordinate of any grid unit, x inj To inject the unit coordinates, the mass conservation equation of fluid flow is discretized by the finite volume method based on the structured rectangular grid unit:

[0143]

[0144] Among them, x and y are spatial coordinates, and i and j are grid unit coordinates. L is the fluid loss term, τ i，j is the time when the cell with coordinates (i, j) starts to filter out.

[0145] The rock solid deformation equation induced by hydraulic fracture is described by three-dimensional displacement discontinuity method. The fracture element normal D 3 and tangential displacement discontinuity D 1 , D 2 It is expressed as:

[0146]

[0147] Among them, u i is (x 1 ,x 2 ,x 3 ) The displacement in three directions in the three-dimensional coordinate system;

[0148] For any fracture grid unit, the normal stress and tangential stress induced by its displacement discontinuity at any point in the reservoir are:

[0149]

[0150] where σ kk , σ kl are the induced normal stress and tangential stress in the local coordinate system, respectively, and C r for:

[0151]

[0152] Where G is the shear modulus, v is Poisson's ratio, and I is the kernel function for a rectangular constant displacement discontinuous grid unit:

[0153]

[0154] I ,k , I ,kl , I ,klm They are respectively the kernel function I in the local coordinate system x 1 , x 2 , x 3 According to the principle of induced stress superposition, the induced stress at any point or any grid unit i is the superposition of the induced stresses generated by all crack units. After the local coordinate system and the global coordinate system are transformed, the induced stress of the grid unit i can be expressed by the following matrix:

[0155]

[0156] Among them, σ nn is the induced normal stress in global coordinates, σ sL , σ sH is the induced tangential stress in the global coordinate system, N is the number of activated fracture grid cells, A is the influence coefficient matrix, i,j is the grid cell index, indicating that the i-th grid cell is subjected to the induced stress of N cells, which can be deduced from formula (4). Considering that the fracture is a non-planar fracture, that is, the fracture does not deflect in the fracture height direction, then σ sH and D 2 are all 0, and formula (7) can be further simplified.

[0157] After establishing the relationship between crack width and induced stress according to the above three-dimensional displacement discontinuity method, the pressure balance condition for any crack grid unit can be expressed as:

[0158]

[0159] In addition, the fluid flow equation is further coupled, where the fluid pressure in the fracture can be calculated from the three-dimensional displacement discontinuity matrix:

[0160] P=σ n +A nn,sL D 1 +A nn,nn D 3 (9)

[0161] Substituting equation (9) into equation (2), we can get the value of the current crack width w n (w n Equal to the crack normal displacement discontinuity D 3 ;w s is the tangential displacement of the crack in the horizontal direction, equal to D 1 ) Calculate the grid cell width w for the next time step n+1:

[0162] w n+1 -w n =ΔtM(w n )(σ n +A nn,sL D 1 +A nn,nn D 3 )+S (10)

[0163] Where M is the coefficient matrix and S is the source-sink function, both of which can be obtained from formula (2).

[0164] The new crack width w n+1 , that is, D 3 , substituting into the three-dimensional displacement discontinuity equation (3), we can obtain:

[0165] P s =A sL,sL D 1 +A sL,nn D 3 (11)

[0166] Among them, P s is the tangential stress of the fracture mesh element.

[0167] The tangential displacement discontinuity D corresponding to the crack grid unit can be calculated by iteratively solving the linear equations. 1 , that is, w s+1 ; By obtaining the displacement of the crack grid unit in the next time step, the crack extension morphology in the next time step is determined.

[0168] S702, obtaining the merging status of the fracture grid unit according to the spatial coordinates of the fracture tip grid of the current time step, and obtaining the target fracture fluid pressure in the fracture grid unit according to the fracture grid unit displacement and the merging status of the fracture grid unit of the current time step, and determining the proppant volume fraction corresponding to the fracture grid unit according to the fracture extension morphology, the fracture tip grid unit displacement and the target fracture fluid pressure;

[0169] In this embodiment, the proppant volume fraction is used to indicate the proppant concentration in the fracture grid unit.

[0170] After obtaining the target fluid pressure in the fracture grid cell in the current time step, the proppant volume fraction corresponding to all grid cells is calculated using the proppant migration mass conservation equation in the fracture in combination with the fracture grid cell displacement:

[0171]

[0172] It should be noted that after discretizing the equation using the same finite volume method as the mass conservation equation for fluid flow in the discrete fracture, in order to meet the stability condition of numerical calculation, the current time step is further divided into α·Δt, and then the proppant volume concentration distribution in the fracture is calculated.

[0173] S703, obtaining fracture grid cells containing proppant volume fractions in the fracture extension morphology, and determining the proppant placement morphology according to the fracture grid cells containing proppant volume fractions;

[0174] According to the determined fracture propagation morphology, the fracture grid cells containing the proppant volume fraction distribution are screened out, and according to the fracture grid cells containing the proppant volume fraction, the corresponding proppant laying morphology is determined.

[0175] S704, after determining that the fracturing numerical simulation of the current fracturing stage is completed, obtaining the first fracture area of ​​the fracture grid unit according to the fracture extension morphology, and obtaining the reservoir transformation volume according to the first fracture area and the permeation distance;

[0176] In this embodiment, the first fracture area is used to indicate the fracture area after the fracture is expanded, and the reservoir transformation volume is used to indicate the maximum volume of oil and gas that can be used in the numerical simulation of fracturing.

[0177] After the fracturing numerical simulation of the current fracturing section is completed, the fracture area after fracture expansion is determined according to the fracture extension morphology, and the reservoir transformation volume is calculated according to the product of the fracture area and the penetration distance.

[0178] S705. Obtain the second fracture area of ​​the fracture grid unit containing the proppant volume fraction according to the proppant laying form, and obtain the effective reservoir transformation volume according to the second fracture area and the penetration distance.

[0179] In this embodiment, the effective reservoir transformation volume is used to indicate the actual volume of oil and gas that can be passively applied in the fracturing numerical simulation.

[0180] According to the proppant laying form, the fracture area containing the proppant volume fraction is determined, and the effective reservoir reconstruction volume is calculated according to the product of the fracture area containing the proppant volume fraction and the penetration distance.

[0181] S706, dividing the fracture grid units into unpropped fracture units without proppant volume fraction and propped fracture units with proppant volume fraction according to the fracture closure status and proppant volume fraction;

[0182] After the numerical simulation of the current fracturing stage is completed, the fracturing fluid in the fracture gradually leaks out under the formation closure stress, and the hydraulic fracture gradually closes. According to the proppant concentration laying results, the fracture grid units are divided into unsupported fracture units and supported fracture units.

[0183] S707, according to the change of the target fracture fluid pressure in the unsupported fracture unit, obtaining the changed target fracture fluid pressure, and according to the supported fracture unit, obtaining the extrusion stress corresponding to the proppant sand pile in the supported fracture unit;

[0184] For hydraulic fracture units without proppant placement, the residual width of the fracture is completely supported by the fluid pressure in the fracture, and the change of the fluid pressure in the fracture satisfies the following relationship:

[0185] P=P 0 e -λt (13)

[0186] Among them, P 0 is the target fluid pressure in the fracture when the fracture is closed, and λ is the fitting coefficient, which is determined by parameters such as formation permeability, fluid viscosity, and formation pressure.

[0187] For fracture units with proppant placement, as the fracture closes, the residual width of the fracture gradually changes from being supported by the fluid pressure in the fracture to being supported by the proppant. The compressive stress on the proppant sand pile can be expressed as:

[0188]

[0189] Among them, c p is the proppant laying concentration, η is a constant determined by the proppant stacking morphology, E'=E / (1-v 2 ), w p0 is the initial width of the fracture supported by the proppant sand pile, w p0 =w 0 c p .

[0190] S708, obtaining the residual width of the fracture grid unit according to the changed target fracture fluid pressure in the unsupported fracture unit and the extrusion stress in the supported fracture unit, and obtaining the corresponding fracturing induced stress field distribution according to the residual width of the fracture.

[0191] In this embodiment, the fracturing induced stress field distribution includes induced normal stress and tangential stress distribution.

[0192] According to the mechanical equilibrium condition of the crack surface and the induced stress matrix, the equation can be established:

[0193] P+P p =σ h +cw r (15)

[0194] By iteratively solving the nonlinear equations, the residual width of the crack w can be obtained. r ;

[0195] According to the residual width of the crack, the induced normal stress and tangential stress distribution are calculated by the induced stress matrix established by the three-dimensional displacement discontinuity method:

[0196]

[0197] Among them, P s ' is the induced tangential stress, P n ' is the induced normal stress.

[0198] S709. When performing numerical simulation of fracturing in the next fracturing stage, obtain the fracturing induced stress corresponding to the residual width of the first fracture, and obtain the target induced stress for crack expansion in the next fracturing stage according to the fracturing induced stress corresponding to the residual width of the first fracture in the previous fracturing stage and the induced stress of the extended crack in the next fracturing stage.

[0199] In this embodiment, the first fractures are the fractures of all the fracture stages before the next fracture stage.

[0200] For the subsequent fracturing stage cracks, in addition to the induced stress interference between the synchronously expanding cracks, the crack expansion process is also affected by the stress interference induced by the residual width of the first fracturing crack. Therefore, the stress boundary condition satisfied by the fluid-solid coupling equation in the subsequent crack expansion should be:

[0201] P=σ n +A nn,sL D 1 +A nn,nn D 3 +P n ' (17)

[0202] The present application provides a method for simulating the coordinated fracturing of a three-dimensional well network. By using a numerical simulation method, the method simulates the hydraulic fracture expansion, proppant migration within the fractures, and the evolution of the induced stress field in the process of fracturing development of a multi-layer three-dimensional well network. This method is more in line with the actual physical process of fracture expansion in the coordinated fracturing of a three-dimensional well network, ensures the authenticity and reliability of the simulation results, improves the accuracy of the simulation results, solves the technical problem of low efficiency of the coordinated fracturing simulation of a three-dimensional well network, and achieves the technical effect of improving the efficiency of the coordinated fracturing simulation of a three-dimensional well network.

[0203] Figure 8 The process of the three-dimensional well network collaborative fracturing simulation method provided in the embodiment of the present application Figure 3 ,like Figure 8 As shown, based on the above embodiment, this embodiment provides a supplementary description of the process of determining the crack extension morphology, including:

[0204] S801, obtaining the displacement of the crack grid unit at the current time step according to the crack grid unit;

[0205] In this embodiment, the calculation method of the displacement of the crack grid unit is the same as the calculation method in S701, and will not be repeated in this embodiment.

[0206] S802, obtaining a critical value of the normal displacement of the crack tip grid unit at the current time step, and comparing the normal displacement of the crack tip grid unit at the current time step with the critical value of the normal displacement;

[0207] According to the linear elastic fracture mechanics criterion, obtain the critical value of the normal displacement of the crack tip mesh element in the current time step:

[0208]

[0209] K are respectively the fracture toughness of mode I crack and the stress intensity factor of mode I of the crack tip unit K I and type II stress intensity factor K II Calculated based on the unit displacement discontinuity:

[0210]

[0211] Where a is the half length of the crack grid unit.

[0212] After obtaining the critical value of normal displacement, it is compared with the normal displacement of the crack tip grid cell in the current time step.

[0213] S803, determining whether the normal displacement of the crack tip grid unit at the current time step exceeds the displacement critical value;

[0214] S804, if yes, determine that the crack has expanded, and obtain the crack expansion direction; determine the crack expansion shape according to the normal displacement and the crack expansion direction;

[0215] If the normal displacement of the mesh element at the crack tip in the current time step exceeds the displacement critical value, it is determined that the crack has expanded, and the direction of crack expansion is obtained according to the maximum circumferential stress criterion:

[0216]

[0217] S805, determining the activation of the rock mechanical weak surface according to the rock mechanical weak surface in the target reservoir, and establishing the penetration / slip criterion of the interface;

[0218] In this embodiment, the rock mechanical weak plane includes the lamination / bedding interface and the natural fracture, and the interface penetration / slip criterion is obtained by the following method:

[0219] τ tip =τ 0 +λ f (σ n -P b) (twenty one)

[0220] Among them, τ tip represents the shear stress at the tip of the rock mechanical weak surface; τ 0 Represents the cementation strength of the rock mechanical weak plane; λ f Represents the friction coefficient of the weak surface of rock mechanics, dimensionless; σ n is the normal stress of the weak surface of rock mechanics; P b is the target fluid pressure in the crack.

[0221] The laminae / bedding interfaces and natural fractures in the target reservoir are regarded as weak surfaces in rock mechanics. Considering that shear slip at the tip of the weak surface needs to overcome the friction force applied by the formation and the inherent cementation strength of the interface, the interface penetration / slip criterion is established according to the Mohr-Coulomb theory:

[0222] S806, after determining that the lamination / bedding plane is activated, obtaining the fluid loss velocity of the bedding plane;

[0223] In this embodiment, the fluid loss velocity is obtained by the following method:

[0224]

[0225] Among them, C L Bedding plane filtration rate; is the porosity of the bedding, dimensionless; Δy is the length of the filtration zone perpendicular to the bedding direction; w l is the bedding aperture; P l is the fluid pressure at the bedding entrance; u is the fluid viscosity; t is the injection time; t 0 It is the time when the bedding plane starts to filter out.

[0226] After the laminae / bedding planes are activated by hydraulic fractures, the bedding slip range satisfies the elliptical shape, and the fluid loss velocity of the bedding plane is calculated using the pipe flow model.

[0227] S807. After determining that the natural fracture is activated, determine the expansion of the natural fracture according to the mixed fracture intensity factor in the direction of the natural fracture.

[0228] In this embodiment, the expansion of natural fractures is obtained by:

[0229]

[0230] Among them, K eq is the equivalent fracture toughness, θ nf is the intersection angle of the weak plane of natural fracture, K I is the stress intensity factor of mode I crack, K II is the stress intensity factor of type II crack, It is the fracture toughness of the weak plane of natural cracks.

[0231] After the natural fractures are activated by hydraulic fractures, the extension of the natural fractures is determined based on the mixed fracture intensity factor in the direction of the natural fractures.

[0232] The present application provides a three-dimensional well network collaborative fracturing simulation method, which simulates the crack propagation process in the three-dimensional well network fracturing by a numerical simulation method, and takes into account the influence of the lamination bedding interface and natural cracks on the hydraulic fracture propagation, thereby ensuring the authenticity and reliability of the simulation results, while improving the accuracy of the simulation results, solving the technical problem of low efficiency of the three-dimensional well network collaborative fracturing simulation, and achieving the technical effect of improving the efficiency of the three-dimensional well network collaborative fracturing simulation.

[0233] Fig. 9 The process of the three-dimensional well network collaborative fracturing simulation method provided in the embodiment of the present application Figure 4 ,like Fig. 9 As shown, this embodiment provides a supplementary explanation of the process of determining the proppant laying form based on the above embodiment, including:

[0234] S901, obtaining the corresponding initial fluid pressure in the fracture according to the displacement of the fracture tip grid unit in the current time step;

[0235] In this embodiment, the initial fluid pressure in the slit is calculated in the same manner as the fluid pressure in the slit in formula (9) of S701, and will not be described in detail in this embodiment.

[0236] S902, obtaining the spatial coordinates of the crack tip unit in the crack grid unit;

[0237] A three-dimensional coordinate system is established according to the crack grid unit, and the three-dimensional space coordinates of the crack tip unit in the crack grid unit are obtained.

[0238] S903, judging whether the spatial distance between any two target crack units in the crack grid unit is less than the length of the crack grid unit according to the spatial coordinates;

[0239] Obtain the three-dimensional spatial coordinates of the crack tip units in any two crack grid units, determine the corresponding spatial distance, and judge whether the spatial distance between any two target crack units in the crack grid unit is less than the length of the crack grid unit;

[0240] S904, if yes, determine that there is a situation where the fractures in the fracture grid unit merge and intersect, and merge the target fracture unit to share a space coordinate point; obtain the normal displacement of the fracture grid unit at the intersection position, and update the initial fracture fluid pressure according to the normal displacement of the fracture grid unit at the intersection position to obtain the updated target fracture fluid pressure;

[0241] If the spatial distance between any two target crack units in the grid unit and the length of the crack grid unit satisfy the following relationship, it is determined that there are cracks merging and intersecting in the crack grid unit:

[0242]

[0243] Merge two crack grid cells and share the same spatial coordinate point. The merged crack grid cell is as follows: Fig.10 As shown;

[0244] Considering the fluid volume exchange between different clusters of fractures at the intersection, the geometric conductivity coefficient is established according to the normal displacement of the fracture unit at the intersection position, and the fluid flow equation in the fracture of the grid unit at the intersection position is corrected to obtain the corrected target fracture fluid pressure:

[0245]

[0246] S905, if not, determining that there is no fracture merging and intersection in the fracture grid unit, and using the initial fracture fluid pressure as the target fracture fluid pressure;

[0247] If the spatial distance between any two target fracture units in the grid unit is greater than the fracture grid unit length, it is determined that there is no fracture merging and intersection in the fracture grid unit, and the initial fracture fluid pressure is determined as the target fracture fluid pressure.

[0248] S906, determining the proppant volume fraction corresponding to the fracture grid unit according to the fracture extension morphology, the fracture grid unit displacement and the target fracture fluid pressure;

[0249] In this embodiment, the calculation method of the proppant volume fraction has been mentioned in S702 and will not be repeated in this embodiment.

[0250] S907, obtaining a pumping volume threshold of the current fracturing stage, and determining whether the proppant volume fraction of the current fracturing stage exceeds the pumping volume threshold;

[0251] The pumping volume threshold of the current fracturing stage is obtained, and the proppant volume fraction of the current fracturing stage is compared with the pumping volume threshold to determine whether the proppant volume fraction of the current fracturing stage exceeds the pumping volume threshold.

[0252] S908, if not, re-determine the simulation time step to repeat the fracturing numerical simulation for the fracturing wells and fracturing sections of each well section in the three-dimensional well network;

[0253] If the proppant volume fraction of the current fracturing section does not exceed the pumping volume threshold, the simulation time step is re-determined according to the length of the grid unit and the crack propagation speed in the three-dimensional well network, and the fracturing numerical simulation is repeated for the fracturing wells and fracturing sections of each well section in the three-dimensional well network according to the new simulation time step.

[0254] S909, if yes, stop the fracturing numerical simulation of the current fracturing stage; obtain the fracture grid cells containing the proppant volume fraction in the fracture extension morphology, and determine the proppant laying morphology according to the fracture grid cells containing the proppant volume fraction.

[0255] In this embodiment, the proppant placement morphology is used to indicate the corresponding fracture morphology of the fracture grid unit containing the proppant volume fraction in the fracture extension morphology.

[0256] If the proppant volume fraction of the current fracturing section exceeds the pumping volume threshold, the fracturing numerical simulation of the current fracturing section is stopped. After the simulation is determined to be finished, the fracture grid cells containing the proppant volume fraction in the fracture extension morphology are obtained, and based on these fracture grid cells, the proppant laying morphology of the current fracturing section is obtained.

[0257] The present application provides a three-dimensional well network collaborative fracturing simulation method, which uses a numerical simulation method to perform fracturing simulation on the process of obtaining the proppant laying morphology in the three-dimensional well network fracturing, and combines the intersection and merging of hydraulic fractures, fluid exchange, and the gradual closing of fractures after the completion of the fracturing section construction to optimize the simulation results of the proppant laying morphology, thereby ensuring the adaptability and flexibility of the simulation results under different conditions, improving the accuracy of the simulation results, solving the technical problem of low efficiency of three-dimensional well network collaborative fracturing simulation, and achieving the technical effect of improving the efficiency of three-dimensional well network collaborative fracturing simulation.

[0258] Fig.11 This is a schematic diagram of the structure of the three-dimensional well network collaborative fracturing simulation device provided in the embodiment of the present application. The device of this embodiment can be in the form of software and / or hardware. Fig.11 As shown, the three-dimensional well pattern collaborative fracturing simulation device 1100 provided in the embodiment of the present application includes: an establishment module 1101, a first processing module 1102, a second processing module 1103, and an output module 1104:

[0259] Establishing module 1101, for obtaining basic parameters of the target reservoir to establish a three-dimensional well pattern collaborative fracturing model; wherein the basic parameters include target reservoir thickness, geomechanical parameters, fracturing construction parameters and penetration distance;

[0260] The first processing module 1102 is used to assign basic parameters to the structured fracture grid units in the three-dimensional network collaborative fracturing model, obtain the length of the fracture grid unit and the fracture propagation speed, so as to determine the corresponding simulation time step, wherein the simulation time step is used to indicate the time step of the fracturing simulation process;

[0261] The second processing module 1103 is used to perform fracturing numerical simulation on the fracturing section of the fracturing well in each well section of the three-dimensional well network within each simulation time step, wherein the three-dimensional well network corresponds to multiple fracturing wells, and each fracturing well corresponds to multiple fracturing sections;

[0262] Output module 1104 is used to output the fracturing simulation results of all well sections in the three-dimensional well network after determining that all well sections in the three-dimensional well network have completed the fracturing numerical simulation, wherein the fracturing simulation results include crack extension morphology, proppant laying morphology, reservoir transformation volume, effective reservoir transformation volume and fracturing induced stress field distribution.

[0263] In a possible implementation, the second processing module 1103 is further configured to:

[0264] According to the crack grid unit, the displacement of the crack tip grid unit in the current time step is obtained to determine the crack extension morphology;

[0265] According to the spatial coordinates of the fracture tip grid of the current time step, the merging status of the fracture grid unit is obtained, and according to the displacement of the fracture grid unit of the current time step and the merging status of the fracture grid unit, the target fracture fluid pressure in the fracture grid unit is obtained;

[0266] Determine the proppant volume fraction corresponding to the fracture grid unit according to the fracture propagation morphology, the displacement of the fracture tip grid unit and the target fracture fluid pressure, wherein the proppant volume fraction is used to indicate the proppant concentration in the fracture grid unit;

[0267] Obtaining fracture grid cells containing proppant volume fractions in fracture extension morphology, and determining proppant placement morphology according to the fracture grid cells containing proppant volume fractions;

[0268] After determining that the fracturing numerical simulation of the current fracturing stage is completed, the first fracture area of ​​the fracture grid unit is obtained according to the fracture extension morphology, and the reservoir transformation volume is obtained according to the first fracture area and the permeation distance;

[0269] According to the proppant laying form, the second fracture area of ​​the fracture grid unit containing the proppant volume fraction is obtained, and according to the second fracture area and the penetration distance, the effective reservoir transformation volume is obtained;

[0270] According to the proppant volume fraction and the target fracture fluid pressure, the fracture residual width of the fracture grid unit is obtained, and according to the fracture residual width, the corresponding fracturing induced stress field distribution is obtained, wherein the fracturing induced stress field distribution includes induced normal stress and tangential stress distribution.

[0271] In a possible implementation, the second processing module 1103 is further configured to:

[0272] According to the crack grid unit, the displacement of the crack tip grid unit of the current time step is obtained, wherein the displacement of the crack tip grid unit includes the normal displacement of the crack tip grid unit and the tangential displacement of the crack grid unit, the normal displacement is used to indicate the current crack width, and the tangential displacement is used to indicate the tangential displacement of the crack in the horizontal direction;

[0273] Obtaining the critical value of the normal displacement of the crack tip grid unit at the current time step, comparing the normal displacement of the crack tip grid unit at the current time step with the critical value of the normal displacement, and determining whether the normal displacement of the crack tip grid unit at the current time step exceeds the critical value of the displacement;

[0274] If so, it is determined that the crack has expanded, the crack expansion direction is obtained, and the crack expansion morphology is determined based on the normal displacement and the crack expansion direction.

[0275] In a possible implementation, the second processing module 1103 is further configured to:

[0276] According to the rock mechanical weak plane in the target reservoir, the activation of the rock mechanical weak plane is determined, and the penetration / slip criterion of the interface is established. The rock mechanical weak plane includes the lamination / bedding interface and natural fractures. The penetration / slip criterion of the interface is obtained by the following method:

[0277] τ tip =τ 0 +λ f (σ n -P b )

[0278] Among them, τ tip represents the shear stress at the tip of the rock mechanical weak surface; τ 0 Represents the cementation strength of the rock mechanical weak plane; λ f Represents the friction coefficient of the weak surface of rock mechanics, dimensionless; σ n is the normal stress of the weak surface of rock mechanics; P b is the fluid pressure in the seam;

[0279] After determining that the laminae / bedding planes are activated, the fluid loss velocity of the bedding planes is obtained. The fluid loss velocity is obtained by:

[0280]

[0281] Among them, C L Bedding plane filtration rate; is the porosity of the bedding, dimensionless; Δy is the length of the filtration zone perpendicular to the bedding direction; w l is the bedding aperture; P l is the fluid pressure at the bedding entrance; u is the fluid viscosity; t is the injection time; t 0 is the time when the bedding plane begins to filter out;

[0282] After determining that the natural fracture is activated, the extension of the natural fracture is determined according to the mixed fracture intensity factor in the direction of the natural fracture. The extension of the natural fracture is obtained in the following way:

[0283]

[0284] Among them, K eq is the equivalent fracture toughness, θ nf is the intersection angle of the weak plane of natural fracture, K I is the stress intensity factor of mode I crack, K II is the stress intensity factor of type II crack, It is the fracture toughness of the weak plane of natural cracks.

[0285] In a possible implementation, the second processing module 1103 is further configured to:

[0286] According to the displacement of the fracture grid unit in the current time step, the corresponding initial fracture fluid pressure is obtained;

[0287] Obtaining the spatial coordinates of the crack tip unit in the crack grid unit, and judging whether the spatial distance between any two target crack units in the crack grid unit is less than the length of the crack grid unit according to the spatial coordinates;

[0288] If so, it is determined that there is a situation where the cracks in the crack grid unit merge and intersect, and the target crack unit is merged to share a space coordinate point;

[0289] If not, it is determined that there is no fracture merging and intersection in the fracture grid unit, and the initial fracture fluid pressure is used as the target fracture fluid pressure.

[0290] In a possible implementation, the second processing module 1103 is further configured to:

[0291] The normal displacement of the fracture grid unit at the intersection position is obtained, and the initial fracture fluid pressure is updated according to the normal displacement of the fracture grid unit at the intersection position to obtain the updated target fracture fluid pressure.

[0292] In a possible implementation, the second processing module 1103 is further configured to:

[0293] Obtaining the pumping volume threshold of the current fracturing stage, and determining whether the proppant volume fraction of the current fracturing stage exceeds the pumping volume threshold;

[0294] If not, the simulation time step is re-determined to repeat the fracturing numerical simulation for the fracturing wells and fracturing sections of each well section in the three-dimensional well network;

[0295] If yes, the fracturing numerical simulation of the current fracturing stage is stopped.

[0296] In a possible implementation, the second processing module 1103 is further configured to:

[0297] After determining that the fracturing numerical simulation of the current fracturing stage is finished, the fracture grid units are divided into unpropped fracture units without proppant volume fraction and propped fracture units with proppant volume fraction according to the fracture closure status and proppant volume fraction;

[0298] According to the change of the fluid pressure in the target fracture in the unsupported fracture unit, the changed fluid pressure in the target fracture is obtained, and according to the supported fracture unit, the extrusion stress corresponding to the proppant sand pile in the supported fracture unit is obtained;

[0299] The residual width of the fracture grid unit is obtained according to the changed target fracture fluid pressure in the unsupported fracture unit and the extrusion stress in the supported fracture unit.

[0300] In a possible implementation, the second processing module 1103 is further configured to:

[0301] When performing fracturing numerical simulation in the next fracturing stage, the fracturing induced stress corresponding to the residual width in the first fracturing fracture is obtained, wherein the first fracturing fracture is the fracture of all fracturing stages before the next fracturing stage;

[0302] According to the fracturing induced stress corresponding to the residual width of the first fracture in the previous fracturing stage and the induced stress of the extended fracture in the next fracturing stage, the target induced stress for the fracture extension in the next fracturing stage is obtained.

[0303] The present application provides a three-dimensional well network collaborative fracturing simulation device that can implement the above method embodiment. Its implementation principle and technical effects are similar, and this embodiment will not be repeated here.

[0304] Fig.12 The hardware structure diagram of the three-dimensional well network collaborative fracturing simulation device provided in the embodiment of the present application. Fig.12 As shown, the three-dimensional well network collaborative fracturing simulation device 1200 includes:

[0305] Processor 1201 and memory 1202;

[0306] Memory stores computer-executable instructions;

[0307] The processor executes the computer execution instructions stored in the memory 1202, so that the three-dimensional well network collaborative fracturing simulation device executes the three-dimensional well network collaborative fracturing simulation method as described above.

[0308] It should be understood that the processor 1201 may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), or application-specific integrated circuits (ASIC). A general-purpose processor may be a microprocessor or any conventional processor. The steps of the method disclosed in the invention may be directly implemented as being executed by a hardware processor, or may be implemented by a combination of hardware and software modules in the processor. The memory 1202 may include a high-speed random access memory (RAM), or may also include a non-volatile memory (NVM), such as at least one disk memory, or may be a USB flash drive, a mobile hard disk, a read-only memory, a disk, or an optical disk.

[0309] An embodiment of the present application correspondingly provides a computer-readable storage medium, in which computer-executable instructions are stored. When the computer-executable instructions are executed by a processor, they are used to implement the above-mentioned three-dimensional well network collaborative fracturing simulation method.

[0310] The embodiment of the present application also provides a computer program product accordingly. When the computer program is executed by a processor, it is used to implement the three-dimensional well network collaborative fracturing simulation method as described above.

[0311] It should be noted that, for the aforementioned method embodiments, for the sake of simplicity, they are all expressed as a series of action combinations, but those skilled in the art should be aware that the present application is not limited by the described order of actions, because according to the present application, certain steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also be aware that the embodiments described in the specification are all optional embodiments, and the actions and modules involved are not necessarily required by the present application.

[0312] It should be further noted that, although the various steps in the flowchart are displayed in sequence according to the indication of the arrows, these steps are not necessarily executed in sequence in the order indicated by the arrows. Unless there is a clear description in this article, the execution of these steps is not strictly limited in order, and these steps can be executed in other orders. Moreover, at least a portion of the steps in the flowchart may include multiple sub-steps or multiple stages, and these sub-steps or stages are not necessarily executed at the same time, but can be executed at different times, and the execution order of these sub-steps or stages is not necessarily to be carried out in sequence, but can be executed in turn or alternately with other steps or at least a portion of the sub-steps or stages of other steps.

[0313] It should be understood that the above-mentioned device embodiments are only illustrative, and the device of the present application can also be implemented in other ways. For example, the division of units / modules in the above-mentioned embodiments is only a logical function division, and there may be other division methods in actual implementation. For example, multiple units, modules or components can be combined, or can be integrated into another system, or some features can be ignored or not executed.

[0314] In addition, unless otherwise specified, each functional unit / module in each embodiment of the present application may be integrated into one unit / module, each unit / module may exist physically separately, or two or more units / modules may be integrated together. The above-mentioned integrated unit / module may be implemented in the form of hardware or in the form of a software program module.

[0315] If the integrated unit / module is implemented in the form of hardware, the hardware can be a digital circuit, an analog circuit, etc. The physical implementation of the hardware structure includes but is not limited to transistors, memristors, etc. If not otherwise specified, the processor can be any appropriate hardware processor, such as CPU, GPU, FPGA, DSP, and ASIC, etc. If not otherwise specified, the storage unit can be any appropriate magnetic storage medium or magneto-optical storage medium, such as Resistive Random Access Memory (RRAM), Dynamic Random Access Memory (DRAM), Static Random-Access Memory (SRAM), etc.

[0316] Memory), Enhanced Dynamic Random Access Memory EDRAM (Enhanced Dynamic Random Access

[0317] Memory), high-bandwidth memory HBM (High-Bandwidth Memory), hybrid memory cube HMC (Hybrid Memory Cube), etc.

[0318] If the integrated unit / module is implemented in the form of a software program module and sold or used as an independent product, it can be stored in a computer-readable memory. Based on this understanding, the technical solution of the present application, or the part that contributes to the prior art or all or part of the technical solution, can be embodied in the form of a software product, which is stored in a memory and includes several instructions for a computer device (which can be a personal computer, a server or a network device, etc.) to perform all or part of the steps of the various embodiments of the present application. The aforementioned memory includes: U disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), mobile hard disk, disk or optical disk and other media that can store program codes.

[0319] In the above embodiments, the description of each embodiment has its own emphasis. For the part not described in detail in a certain embodiment, please refer to the relevant description of other embodiments. The technical features of the above embodiments can be combined arbitrarily. In order to make the description concise, all possible combinations of the technical features in the above embodiments are not described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0320] Those skilled in the art will readily appreciate other embodiments of the present application after considering the specification and practicing the invention disclosed herein. The present application is intended to cover any modification, use or adaptation of the present application, which follows the general principles of the present application and includes common knowledge or customary techniques in the art that are not disclosed in the present application. The specification and examples are intended to be exemplary only, and the true scope and spirit of the present application are indicated by the following claims.

[0321] It should be understood that the present application is not limited to the precise structures that have been described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present application is limited only by the appended claims.

Claims

1. A three-dimensional well pattern collaborative fracturing simulation method, characterized in that: include: Obtaining basic parameters of the target reservoir to establish a three-dimensional well pattern collaborative fracturing model; wherein the basic parameters include target reservoir thickness, geomechanical parameters, fracturing construction parameters and penetration distance; Assigning the basic parameters to the structured fracture grid units in the three-dimensional well pattern collaborative fracturing model, obtaining the length of the fracture grid units and the fracture propagation speed, so as to determine the corresponding simulation time step, wherein the simulation time step is used to indicate the time step of the fracturing simulation process; In each simulation time step, a fracturing numerical simulation is performed on the fracturing section of the fracturing well in each well section of the three-dimensional well network, wherein the three-dimensional well network corresponds to a plurality of fracturing wells, and each fracturing well corresponds to a plurality of fracturing sections; After determining that all well sections of the three-dimensional well network have completed the fracturing numerical simulation, outputting the fracturing simulation results of all well sections in the three-dimensional well network, wherein the fracturing simulation results include the fracture extension morphology, proppant laying morphology, reservoir transformation volume, effective reservoir transformation volume and fracturing induced stress field distribution; The method of performing a fracturing numerical simulation on the fracturing section of the fracturing well in each well section of the three-dimensional well network within each simulation time step includes: According to the crack grid unit, obtaining the displacement of the crack tip grid unit at the current time step to determine the crack extension morphology; According to the spatial coordinates of the fracture tip grid of the current time step, the merging status of the fracture grid unit is obtained, and according to the displacement of the fracture grid unit of the current time step and the merging status of the fracture grid unit, the target fracture fluid pressure in the fracture grid unit is obtained; Determine the proppant volume fraction corresponding to the fracture grid unit according to the fracture extension morphology, the displacement of the fracture tip grid unit and the target fracture fluid pressure, wherein the proppant volume fraction is used to indicate the proppant concentration in the fracture grid unit; Acquire the fracture grid unit containing the proppant volume fraction in the fracture extension morphology, and determine the proppant laying morphology according to the fracture grid unit containing the proppant volume fraction; After determining that the fracturing numerical simulation of the current fracturing stage is finished, obtaining the first fracture area of ​​the fracture grid unit according to the fracture extension morphology, and obtaining the reservoir transformation volume according to the first fracture area and the permeation distance; According to the proppant laying form, obtaining the second fracture area of ​​the fracture grid unit containing the proppant volume fraction, and according to the second fracture area and the permeation distance, obtaining the effective reservoir transformation volume; According to the proppant volume fraction and the target fracture fluid pressure, the fracture residual width of the fracture grid unit is obtained, and according to the fracture residual width, the corresponding fracturing induced stress field distribution is obtained, wherein the fracturing induced stress field distribution includes induced normal stress and tangential stress distribution.

2. The method according to claim 1, characterized in that: The step of obtaining the displacement of the crack tip grid unit at the current time step according to the crack grid unit to determine the crack extension morphology includes: According to the crack grid unit, a crack tip grid unit displacement of the current time step is obtained, wherein the crack tip grid unit displacement includes a normal displacement of the crack tip grid unit and a tangential displacement of the crack grid unit, the normal displacement is used to indicate the current crack width, and the tangential displacement is used to indicate the tangential displacement of the crack in the horizontal direction; Obtaining a critical value of the normal displacement of the crack tip grid unit at the current time step, comparing the normal displacement of the crack tip grid unit at the current time step with the critical value of the normal displacement, and determining whether the normal displacement of the crack tip grid unit at the current time step exceeds the critical value of the displacement; If so, it is determined that the crack has expanded, the crack expansion direction is obtained, and the crack expansion morphology is determined based on the normal displacement and the crack expansion direction.

3. The method according to claim 2, characterized in that After obtaining the target fracture fluid pressure in the fracture grid unit according to the fracture grid unit displacement of the current time step and the merging status of the fracture grid unit, the method further includes: According to the rock mechanical weak surface in the target reservoir, the activation of the rock mechanical weak surface is determined, and the penetration / slip criterion of the interface is established, wherein the rock mechanical weak surface includes the lamination / bedding interface and the natural fracture, and the penetration / slip criterion of the interface is obtained by the following method: in, Represents the shear stress at the tip of the rock mechanical weak plane; Represents the cementation strength of the rock mechanical weak plane; The friction coefficient representing the weak surface of rock mechanics is dimensionless; is the normal stress of the weak surface of rock mechanics; is the fluid pressure in the target seam; After determining that the laminae / bedding plane is activated, the fluid loss velocity of the bedding plane is obtained, and the fluid loss velocity is obtained in the following manner: in, Bedding plane filtration rate; is the porosity of the bedding, dimensionless; is the length of the filtration zone in the direction perpendicular to the bedding; is the bedding aperture; is the fluid pressure at the bedding entrance; is the fluid viscosity; is the injection time; is the time when the bedding plane begins to filter out; After determining that the natural fracture is activated, the extension of the natural fracture is determined according to the mixed fracture intensity factor in the direction of the natural fracture. The extension of the natural fracture is obtained in the following manner: in, is the equivalent fracture toughness, is the intersection angle of the weak planes of natural fractures, is the stress intensity factor of mode I crack, is the stress intensity factor of type II crack, It is the fracture toughness of the weak plane of natural cracks.

4. The method according to claim 1, characterized in that: The step of obtaining the target fracture fluid pressure in the fracture grid unit according to the fracture grid unit displacement of the current time step and the merging status of the fracture grid unit comprises: According to the displacement of the fracture grid unit of the current time step, the corresponding initial fracture fluid pressure is obtained; Acquire the spatial coordinates of the crack tip unit in the crack grid unit, and determine, based on the spatial coordinates, whether the spatial distance between any two target crack units in the crack grid unit is less than the length of the crack grid unit; If yes, it is determined that there is a situation where the cracks in the crack grid unit are merged and intersected, and the target crack unit is merged to share a space coordinate point; If not, it is determined that there is no fracture merging and intersection in the fracture grid unit, and the initial fracture fluid pressure is used as the target fracture fluid pressure.

5. The method according to claim 4, characterized in that After merging the target crack units and sharing a space coordinate point, the method further includes: The normal displacement of the fracture grid unit at the intersection position is obtained, and the initial fracture fluid pressure is updated according to the normal displacement of the fracture grid unit at the intersection position to obtain the updated target fracture fluid pressure.

6. The method according to claim 1, characterized in that After determining the proppant volume fraction corresponding to the fracture grid unit according to the fracture extension morphology, the fracture grid unit displacement and the target fracture fluid pressure, the method further includes: Obtaining a pumping volume threshold of a current fracturing stage, and determining whether the proppant volume fraction of the current fracturing stage exceeds the pumping volume threshold; If not, re-determine the simulation time step to repeat the fracturing numerical simulation for the fracturing wells and fracturing sections of each well section in the three-dimensional well network; If so, the fracturing numerical simulation of the current fracturing stage is stopped.

7. The method according to claim 1, characterized in that The step of obtaining the residual width of the fracture grid unit according to the proppant volume fraction and the target fracture fluid pressure includes: After determining that the fracturing numerical simulation of the current fracturing stage is finished, dividing the fracture grid units into unpropped fracture units without the proppant volume fraction and propped fracture units with the proppant volume fraction according to the fracture closure status and the proppant volume fraction; According to the change of the target fracture fluid pressure in the unpropped fracture unit, the changed target fracture fluid pressure is obtained, and according to the propped fracture unit, the extrusion stress corresponding to the proppant sand pile in the propped fracture unit is obtained; The residual width of the crack of the crack grid unit is obtained according to the changed target crack fluid pressure in the unsupported crack unit and the extrusion stress in the supported crack unit.

8. The method according to claim 1, characterized in that After obtaining the corresponding fracturing induced stress field distribution according to the residual width of the crack, the method further includes: When performing the fracturing numerical simulation in the next fracturing stage, obtaining the fracturing induced stress corresponding to the residual width of the first fracturing crack, wherein the first fracturing crack is the crack of all fracturing stages before the next fracturing stage; According to the fracturing induced stress corresponding to the residual width of the first fracture in the previous fracturing stage and the induced stress of the extended fracture in the next fracturing stage, the target induced stress of the fracture extension in the next fracturing stage is obtained.

9. A three-dimensional well pattern collaborative fracturing simulation device, characterized in that: include: Memory, processor; The memory stores computer-executable instructions; The processor executes the computer-executable instructions stored in the memory, so that the processor executes the three-dimensional well network collaborative fracturing simulation method as described in any one of claims 1-8.

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