Dynamic and static coupling simulation method for hydraulic-detonation combined fracturing transformation

Abstract

The invention belongs to the field of oil and gas development and energy utilization, particularly relates to a dynamic and static coupling simulation method for hydraulic-detonation combined fracturing transformation, and aims at solving the problem that in the prior art, the transformation effect is poor when fracturing transformation is conducted on deep-ultra-deep reservoirs. The method comprises the following steps: constructing a hydraulic-detonation fracturing transformation dynamic and static coupling numerical calculation model; through a discontinuous calculation method, the expansion process of the hydraulic fracturing main fracture under the static condition is simulated, and after the preset main fracture length is reached, static simulation is ended; keeping the model stress and the geometrical shape of the main fracture unchanged, loading detonation shock waves in a preset detonation area, converting a static boundary condition into a dynamic boundary condition, performing detonation pressure fracture network expansion process simulation under the dynamic condition, and after a preset simulation time is reached, ending the dynamic simulation and outputting a fracture network spatial configuration. By means of hydraulic-detonation fracturing dynamic and static coupling simulation calculation, the effect of deep-ultra-deep reservoir fracturing transformation is improved.

Description

Technical Field

[0001] The invention belongs to the field of oil and gas development and energy utilization, and specifically relates to a dynamic and static coupling simulation method and system for hydraulic-detonation combined fracturing transformation. Background Art

[0002] Unconventional energy reservoirs (shale oil and gas, tight oil and gas, etc.) have low permeability of the reservoir rock itself, so artificial fracturing transformation technology must be used to create cracks in the reservoir to form a dense seepage network in order to achieve effective development of oil and gas resources. Hydraulic fracturing technology is the most commonly used reservoir fracturing transformation method. Previous applications and research have shown that hydraulic fracturing can effectively fracture shale oil and gas reservoirs and greatly increase the permeability of the reservoir. Therefore, hydraulic fracturing technology has promoted the application and rapid development of unconventional energy such as shale oil and gas.

[0003] In recent years, due to the gradual depletion of the remaining shallow oil and gas resources, it is no longer sufficient to support the rapid development of the social economy. The newly added oil and gas reserves mainly come from unconventional oil and gas reservoirs at a depth of more than 4,500 meters. Due to the large ground stress, the deep-ultra-deep reservoirs are more compact, the rock is less brittle, and the compressibility is poor, which requires higher requirements for reservoir fracturing transformation. The exploration and development of deep shale oil and gas reservoirs have shown that it is difficult to form a dense artificial fracture network like shallow reservoirs by using traditional hydraulic fracturing technology to transform deep reservoirs. The reservoir transformation range is effective, the main fractures and branch fractures are difficult to form, or the fractures are easy to close after formation, and the transformation effect is poor. Therefore, in order to achieve the effective development of deep-ultra-deep oil and gas resources, the traditional hydraulic fracturing technology system must be upgraded. Among them, on the basis of hydraulic fracturing, the chemical reaction of liquid explosives is used to generate detonation shock waves inside the fractures, thereby fracturing the reservoir. This is a very potential deep-ultra-deep reservoir fracturing transformation technology. The hydraulic-detonation combined fracturing reconstruction method takes advantage of hydraulic fracturing in creating main fractures, and uses static water pressure to promote the formation of macroscopically wide advantageous seepage channels inside the reservoir; it takes advantage of detonation fracturing in creating complex small-scale complex fracture networks, and uses high-pressure dynamic detonation shock waves to force rocks to break around the main fractures, ultimately forming a high-permeability fracture network with main fractures and complex branch fracture networks around the main fractures in series. Therefore, due to the unique concept of dynamic and static reservoir reconstruction, the hydraulic-detonation combined fracturing reconstruction method may become a key technical means for the transformation of reservoir reconstruction technology system.

[0004] At present, there is no available numerical simulation software for hydraulic-detonation combined fracturing in the world, which seriously restricts the further application of this technology. Traditional hydraulic fracturing simulation methods and software (such as MEYER, GOHFER, etc.) are aimed at the main fracture expansion problem under static water pressure conditions and cannot be directly applied to dynamic detonation fracturing simulation. In addition, hydraulic-detonation combined fracturing is a continuous physical process. Its geometric model, fracture morphology, boundary conditions, etc. need to be transferred between the static analysis of hydraulic fracturing and the dynamic analysis of detonation fracturing. Therefore, if different simulation methods are used to simulate hydraulic fracturing and detonation fracturing respectively, the information transmission will cause unnecessary operations, which may bring errors and seriously affect the calculation efficiency. However, it is difficult to consider the static fracturing of hydraulic fracturing and the dynamic fracturing of detonation fracturing under the framework of a unified calculation method, and to realize the dynamic-static coupling simulation for a unified numerical model. There is no mature solution at present. Therefore, if a dynamic-static coupling simulation method for hydraulic-detonation combined fracturing can be proposed, it will greatly promote the application of this technology.

[0005] Based on this, the present invention proposes a dynamic-static coupling simulation method for hydraulic-detonation combined fracturing transformation. Summary of the invention

[0006] In order to solve the above-mentioned problems in the prior art, that is, to solve the problem that when the prior art performs fracturing transformation on deep-ultra-deep reservoirs, the reservoir transformation range is effective, the main fractures and branch fractures are difficult to form, or the fractures are easy to close after formation, the transformation effect is poor, and the effective development of oil and gas resources in deep-ultra-deep reservoirs cannot be achieved. In the first aspect of the present invention, a dynamic and static coupling simulation method for hydraulic-detonation combined fracturing transformation is proposed, which is used to simulate the expansion process of the fracture network of deep oil and gas reservoirs under the combined action of hydraulic fracturing-detonation fracturing, and obtain the expansion form of the fracture network; the method comprises: According to the three-dimensional transformation method of deep oil and gas reservoirs, a target simulation area is selected; the target simulation area is network-divided, and then a dynamic-static coupling numerical calculation model of hydraulic-detonation fracturing transformation is constructed; the three-dimensional transformation method includes segmented perforation and segmented fracturing transformation; Combined with the dynamic-static coupling numerical calculation model of hydraulic-detonation fracturing, the overall stress balance of the grid unit under the initial ground stress condition is completed through a discontinuous calculation method, and the fluid injection rate is set to simulate the expansion process of the main hydraulic fracturing crack under static conditions. After the preset main crack length is reached, the static simulation ends; Keeping the model stress and main fracture geometry unchanged, the detonation shock wave is loaded in the preset detonation area, the static boundary conditions are converted into dynamic boundary conditions, and the expansion process of the detonation fracture network under dynamic conditions is simulated. After reaching the preset simulation time, the dynamic simulation ends and the fracture network spatial configuration of the deep oil and gas reservoir, that is, the expansion form of the fracture network, is output.

[0007] In some preferred embodiments, a dynamic-static coupling numerical calculation model of hydraulic-detonation fracturing reformation is constructed by: According to the three-dimensional transformation method of the deep oil and gas reservoir, a single side area of ​​a single perforation cluster of the deep oil and gas reservoir is selected as a target simulation area; According to the fracturing reconstruction range in terms of the fracturing stage spacing and length, the length and width of the target simulation area are determined, and then the target simulation area is gridded; Combined with the target simulation area after grid division, the dynamic-static coupling boundary and the geometric symmetry boundary are defined, the fluid injection point position, boundary stress, maximum principal stress and minimum principal stress are set, and finally, the dynamic-static coupling numerical calculation model of hydraulic-detonation fracturing transformation is generated; wherein, the fluid injection point position is set at the midpoint of the geometric symmetry boundary.

[0008] In some preferred embodiments, dynamic-static coupling boundaries and geometric symmetry boundaries are defined by defining the left boundary, right boundary and upper boundary of the numerical calculation model as dynamic-static coupling boundaries, and the lower boundary as a geometric symmetry boundary; the dynamic-static coupling boundaries are converted between dynamic and static according to the calculation type during the numerical calculation process.

[0009] In some preferred embodiments, the numerical simulation calculation method for the expansion process of the main hydraulic fracture under static conditions is: If the main hydraulic fracturing crack is a tensile crack, the flow velocity along the crack direction is calculated based on the viscosity of the fluid, the opening of the crack, the pressure of the fluid in the crack, and the length coordinate along the crack direction; The maximum tensile stress criterion is used to determine the crack criticality and obtain the normal stress between units, that is, the normal stress between units at the crack tip; Convert the dynamic-static coupling boundary conditions into fixed boundary conditions to obtain the displacements of the nodes on the boundary; The fluid pressure is calculated based on the flow velocity along the fracture direction; a linear solution equation group under the static condition of hydraulic fracturing is constructed by combining the fluid pressure, the normal stress between the units at the fracture tip, and the displacement at the node on the boundary. KD=F , the static expansion form of the hydraulic fracture network, i.e. the main fracture geometry, is obtained by solving ; K represents the stiffness matrix, D represents the displacement vector to be determined, FRepresents the overall load vector acting on the element.

[0010] In some preferred embodiments, the simulation calculation method of the detonation pressure fracture network expansion process under dynamic conditions is: According to the Mohr-Coulomb strength criterion, based on the cohesive strength of rock under static conditions and the cohesive strength of rock under detonation shock wave loading conditions, the dynamic growth factor of rock strength under high strain rate conditions is calculated; According to the changes of cohesion strength and friction angle under high strain rate, combined with the dynamic growth factor of rock strength under the high strain rate condition and the normal stress between the units, the tangential stress between the units is calculated; The conditions of the dynamic-static coupling boundary are converted into a transmission boundary, the transmission phenomenon of the shock wave at the boundary is simulated, and the stiffness matrix correction of the unit on the transmission boundary is obtained; The stiffness matrix of the corresponding unit is corrected based on the stiffness matrix correction amount; combining the stiffness matrix of the corrected unit, the load on the boundary and inside of the unit, and the tangential stress between the units, a linear solution equation group under dynamic detonation shock wave conditions is constructed, and then the dynamic expansion form of the fracture network is solved.

[0011] In some preferred embodiments, the tangential stress between cells is calculated by: ; ; in, s τ is the tangential stress between units, DIF is the dynamic growth factor of rock strength under high strain rate conditions, C n0 is the cohesive strength of rock under static conditions, obtained through shear test, C n The cohesive strength of rock under detonation shock wave loading conditions is obtained by impact testing rock specimens in uniaxial state using a split Hopkinson pressure bar test. is the internal friction angle, s n is the normal stress between elements.

[0012] In some preferred embodiments, the angle of the actual extension direction of the cracks of rock fracture under detonation load is obtained by: ; ; in, represents the hoop stress at the crack tip, The angle that indicates the actual crack expansion direction, Indicates an angle.

[0013] In some preferred embodiments, the stiffness matrix correction amount of the unit on the transmission boundary is calculated as follows: ; in, DK i For unit The stiffness matrix correction of p is the stiffness of the damper set at the transmission boundary, T i is the displacement transformation matrix of the discontinuous calculation method, F is the direction cosine matrix.

[0014] In some preferred embodiments, the linear solution equations under the dynamic detonation shock wave condition are: ; in, M represents the mass matrix of the element, m is the damping matrix, is the acceleration vector, is the velocity vector The second aspect of the present invention proposes a dynamic and static coupling simulation system for hydraulic-detonation combined fracturing reformation, which is used to simulate the expansion process of the fracture network of deep oil and gas reservoirs under the combined action of hydraulic fracturing-detonation fracturing to obtain the expansion form of the fracture network; the system includes: The model building module is configured to select a target simulation area according to a three-dimensional transformation method of a deep oil and gas reservoir; divide the target simulation area into a network, and then build a dynamic and static coupling numerical calculation model of hydraulic-detonation fracturing transformation; the three-dimensional transformation method includes segmented perforation and segmented fracturing transformation; The static simulation module is configured to combine the dynamic-static coupling numerical calculation model of hydraulic-detonation fracturing transformation, complete the overall stress balance of the grid unit under the initial ground stress condition through a discontinuous calculation method, and set the fluid injection rate to simulate the expansion process of the main hydraulic fracturing crack under static conditions. After reaching the preset main crack length, the static simulation ends; The dynamic simulation module is configured to keep the model stress and the main fracture geometry unchanged, load the detonation shock wave in the preset detonation area, convert the static boundary conditions into dynamic boundary conditions, and simulate the expansion process of the detonation fracture network under dynamic conditions. After reaching the preset simulation time, the dynamic simulation ends and outputs the fracture network spatial configuration of the deep oil and gas reservoir, that is, the expansion form of the fracture network.

[0015] Beneficial effects of the present invention: The present invention realizes dynamic and static coupling simulation calculation of hydraulic-detonation fracturing under an established calculation model, a set of grid units, and a set of calculation framework (that is, utilizing the advantages of hydraulic fracturing in creating main fractures, promoting the formation of macroscopically wide advantageous seepage channels inside the reservoir through static water pressure; utilizing the advantages of detonation fracturing in creating complex small-scale complex fracture networks, forcing rocks to break around the main fractures through high-pressure dynamic detonation shock waves, and finally forming a high-permeability fracture network in which the main fractures and complex branch fracture networks around the main fractures are connected in series). Without additional technical means, the whole process simulation of hydraulic-detonation combined fracturing transformation can be realized, thereby improving the effect of deep-ultra-deep reservoir fracturing transformation, improving calculation efficiency, and realizing the effective development of deep-ultra-deep reservoir oil and gas resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Other features, objects and advantages of the present application will become more apparent by reading the detailed description of non-limiting embodiments made with reference to the following drawings.

[0017] Figure 1 It is a schematic flow chart of a dynamic and static coupling simulation method for hydraulic-detonation combined fracturing reformation according to an embodiment of the present invention; Figure 2 It is a schematic diagram of a dynamic-static coupling numerical calculation model of hydraulic-detonation fracturing reformation of a deep oil and gas reservoir according to an embodiment of the present invention; Figure 3 It is a schematic diagram of a process for obtaining the angle of the actual expansion direction of a crack of a rock fracture under a detonation load according to an embodiment of the present invention. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution in the embodiment of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiment is a part of the embodiment of the present invention, not all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] The present application will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the relevant invention, rather than to limit the invention. It is also necessary to explain that, for ease of description, only the parts related to the relevant invention are shown in the accompanying drawings.

[0020] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application may be combined with each other.

[0021] A dynamic and static coupling simulation method for hydraulic-detonation combined fracturing reconstruction in the first embodiment of the present invention is used to simulate the expansion process of the fracture network of deep oil and gas reservoirs under the combined action of hydraulic fracturing-detonation fracturing to obtain the expansion form of the fracture network; Figure 1 As shown, the method includes: According to the three-dimensional transformation method of deep oil and gas reservoirs, a target simulation area is selected; the target simulation area is network-divided, and then a dynamic-static coupling numerical calculation model of hydraulic-detonation fracturing transformation is constructed; the three-dimensional transformation method includes segmented perforation and segmented fracturing transformation; Combined with the dynamic-static coupling numerical calculation model of hydraulic-detonation fracturing, the overall stress balance of the grid unit under the initial ground stress condition is completed through a discontinuous calculation method, and the fluid injection rate is set to simulate the expansion process of the main hydraulic fracturing crack under static conditions. After the preset main crack length is reached, the static simulation ends; Keeping the model stress and main fracture geometry unchanged, the detonation shock wave is loaded in the preset detonation area, the static boundary conditions are converted into dynamic boundary conditions, and the expansion process of the detonation fracture network under dynamic conditions is simulated. After reaching the preset simulation time, the dynamic simulation ends and the fracture network spatial configuration of the deep oil and gas reservoir, that is, the expansion form of the fracture network, is output.

[0022] In order to more clearly illustrate the dynamic-static coupling simulation method of hydraulic-detonation combined fracturing reconstruction of the present invention, each step in an embodiment of the method of the present invention is described in detail below with reference to the accompanying drawings.

[0023] The present invention provides a dynamic and static coupled discontinuous numerical simulation method, which can realize the whole process simulation of hydraulic-detonation combined fracturing without additional technical means, and is intended to be used for the optimization design of reservoir transformation and promote the improvement of oil and gas recovery rate. It includes the following steps: According to the three-dimensional transformation method of deep oil and gas reservoirs, a target simulation area is selected; the target simulation area is network-divided, and then a dynamic-static coupling numerical calculation model of hydraulic-detonation fracturing transformation is constructed; the three-dimensional transformation method includes segmented perforation and segmented fracturing transformation; When deep oil and gas reservoirs are fracturing and developed using horizontal wells, segmented perforation and segmented fracturing are generally used to transform the reservoirs in three dimensions. From the perspective of the spatial geometric relationship between horizontal wells and perforations, each perforation and fracturing segment can be considered similar, and the upper and lower segments can be considered symmetrical.

[0024] In this embodiment, when performing numerical simulation calculations on the reservoir transformation problem, a single side area of ​​a single perforation cluster is selected for simulation. The simulation process is as follows: First, the length of the target simulation area is determined according to the fracturing range in terms of the spacing and length of the fracturing stages.L ,Width W The target calculation area is meshed using quadrilateral meshes with a mesh size of dL ; Then, define the left, right and upper boundaries of the numerical calculation model as dynamic-static coupling boundaries, which can be converted into dynamic-static according to the calculation type in the numerical calculation. The lower boundary is a geometric symmetric boundary; secondly, set the fluid injection point to the midpoint of the lower boundary of the model; then, set the boundary stress (ground stress) and maximum principal stress of the model s 1 and the minimum principal stress s 3 ; Finally, a dynamic-static coupling numerical calculation model of hydraulic-detonation fracturing transformation for deep oil and gas reservoirs is generated. Assuming that the length of the dynamic-static coupling numerical calculation model of hydraulic-detonation fracturing transformation is 100m, the width is 200m, and the grid size is 4m, the generated dynamic-static coupling numerical calculation model of hydraulic-detonation fracturing transformation for deep oil and gas reservoirs is as follows: Figure 2 shown.

[0025] Combined with the dynamic-static coupling numerical calculation model of hydraulic-detonation fracturing, the overall stress balance of the grid unit under the initial ground stress condition is completed through a discontinuous calculation method, and the fluid injection rate is set to simulate the expansion process of the main hydraulic fracturing crack under static conditions. After the preset main crack length is reached, the static simulation ends; Among them, the method for obtaining the overall stress balance is: first, set the stress load on the model boundary according to the formation stress conditions, that is, the minimum principal stress and the maximum principal stress, and add them to the boundary conditions of the model. The model is used as an internal load added to the inside of the unit. Secondly, adopt fixed boundary conditions and set the outer boundary of the model as fixed boundary conditions, and no displacement can occur. Then, the overall stiffness matrix and load matrix are constructed to solve the displacement of each unit of the model under the initial stress load. Iterate multiple times until the displacement converges, that is, the overall stress balance of the grid unit is achieved, the unit displacement is cleared, the stress is used as the initial condition, and the result is saved.

[0026] In this embodiment, based on the constructed dynamic-static coupling numerical calculation model of hydraulic-detonation fracturing transformation, combined with the discontinuous calculation framework (the discontinuous method is a numerical calculation method different from the traditional continuous method (finite element, finite difference, finite volume method, etc.), which can easily simulate the separation and slip between units, realize the simulation of crack expansion, and can achieve seamless conversion between dynamic and static) to realize the numerical simulation calculation of the hydraulic fracturing crack expansion process under static conditions. The details are as follows: In the present invention, it is assumed that the main fracture of hydraulic fracturing is a tensile fracture, and its internal flow process satisfies: (1) in, qis the flow velocity along the fracture direction, m is the viscosity of the fluid, oh is the opening of the crack, p is the pressure of the fluid in the crack, l is the length coordinate along the crack direction.

[0027] The maximum tensile stress criterion is used for critical fracture judgment, that is, when the normal stress between units at the fracture tip reaches the tensile stress strength of the rock, the fracture expands: (2) in, s n is the normal stress between units at the crack tip, that is, the normal stress between units, T 0 is the tensile stress strength of rock.

[0028] The dynamic-static coupling boundary conditions in the dynamic-static coupling numerical calculation model of deep oil and gas reservoir hydraulic-detonation fracturing transformation are converted into fixed boundary conditions during the static calculation of hydraulic fracturing, that is, (3) in, u i represents the displacement at the node on the boundary, i Represents coordinates, in two dimensions i The quantity is 2.

[0029] Under the static condition of hydraulic fracturing, ignoring the influence of inertia and viscous damping, a linear solution equation group is established to obtain the static expansion form of the hydraulic fracture network, that is, the main fracture geometry. The linear solution equation group under the static condition of hydraulic fracturing is as follows: KD=F (4) in, K Represents the stiffness matrix, which is the overall stiffness matrix here, and is related to the elastic parameters of the rock, displacement boundary conditions, etc.; D represents the displacement vector to be sought; F Represents the overall load vector acting on the element.

[0030] Keeping the model stress and main fracture geometry unchanged, the detonation shock wave is loaded in the preset detonation area, the static boundary conditions are converted into dynamic boundary conditions, and the expansion process of the detonation fracture network under dynamic conditions is simulated. After reaching the preset simulation time, the dynamic simulation ends and the fracture network spatial configuration of the deep oil and gas reservoir, that is, the expansion form of the fracture network, is output.

[0031] In this embodiment, based on the constructed dynamic-static coupling numerical calculation model of hydraulic-detonation fracturing, the numerical simulation calculation of the expansion process of the detonation fracture network under dynamic conditions is realized based on the discontinuous calculation framework, as follows: Under high strain rate conditions, rock fracture is a high-speed fracture behavior in a short period of time, which is correlated with time and strain rate. In the discontinuous calculation framework, this technical solution introduces the strain rate-related Mohr-Coulomb strength criterion to describe the fracture behavior of rock and define the dynamic growth factor: (5) Where DIF is the dynamic growth factor of rock strength under high strain rate conditions; C n0 is the cohesive strength of rock under static conditions, obtained through shear tests; C n The cohesive strength of rock under detonation shock wave loading conditions can be obtained by impact testing rock specimens under uniaxial conditions using a split Hopkinson pressure bar test. Using the defined dynamic growth factor DIF, the Mohr-Coulomb criterion is modified by considering that the cohesive strength is enhanced under high strain rates and the friction angle remains basically unchanged.

[0032] (6) in, s τ is the tangential stress between elements, C n0 is the cohesive strength of rock in static state, is the internal friction angle; s n is the normal stress between units. Using the above formula, a strength criterion that takes strain rate dependency into account can be obtained. In the calculation program, only the cohesion needs to be modified to facilitate calculation.

[0033] The modified criterion based on Mohr-Coulomb can be used to identify rock fractures under detonation loads. However, the crack propagation trajectory cannot be identified with high precision. When using the discontinuous method to simulate crack propagation under detonation loads, the model needs to be divided into grid units. Traditional methods generally believe that cracks only occur between units that meet the fracture criterion. However, since the singularity of the stress at the crack tip cannot be reflected, the simulation accuracy of the crack trajectory is not high.

[0034] The present invention proposes a high-precision method for determining crack propagation trajectories under detonation loads. First, a coordinate system is established at the crack tip unit, and the annular stress at the crack tip is obtained based on the unit stress distribution. s θθ With Angle i The distribution of the actual crack expansion direction is i 0satisfy: (7) (8) According to the above formula, the actual crack extension direction can be determined i 0 , determine the expansion path. Then, optimize the division of the crack tip unit. i 0 Direction will expand the cells on the trajectory Oh Split into two, become Oh 1 and Oh 2 , so that the crack can pass through the unit ( Figure 3 ). The above method avoids high-resolution meshing and can greatly improve the calculation accuracy and efficiency of the trajectory of a large number of crack extensions under detonation loads.

[0035] For the dynamic and static coupling boundary conditions in the dynamic and static coupling numerical calculation model of hydraulic-detonation fracturing transformation of deep oil and gas reservoirs, they are converted into transmission boundaries during the dynamic calculation of detonation fracturing to simulate the transmission phenomenon of shock waves at the boundary and prevent shock wave reflection. When the unit is located on the transmission boundary, its unit stiffness matrix is ​​modified as follows: (9) in, DK i For unit The stiffness matrix correction of p is the stiffness of the damper set at the transmission boundary, T i is the displacement transformation matrix of the discontinuous calculation method, F is the direction cosine matrix. The stiffness matrix of the corresponding unit is modified based on the stiffness matrix correction amount.

[0036] Under the condition of dynamic detonation shock wave, the influence of inertia and time-related transient processes must be considered, and a linear solution equation group must be established and solved to obtain the dynamic expansion form of the fracture network. The linear solution equation group under the condition of dynamic detonation shock wave is shown as follows: (10) in, M represents the mass matrix of the element, m is the damping matrix, is the acceleration vector, is the velocity vector, K Represents the stiffness matrix, here it is the stiffness matrix of the element.

[0037] In summary, the present invention can realize the dynamic and static coupling simulation calculation of hydraulic-detonation fracturing under the establishment of a calculation model, a set of grid units, and a set of calculation frameworks. That is, a dynamic and static coupling numerical calculation model of hydraulic-detonation fracturing transformation is first constructed. Then, under the non-continuous calculation system, the overall stress balance of the grid unit under the initial ground stress condition is first completed. Secondly, the fluid injection rate is set to simulate the expansion process of the main fracture of hydraulic fracturing under static conditions. After reaching the preset main fracture length, the static simulation ends. After that, the model stress, the main fracture geometry, etc. are kept unchanged, the explosion shock wave is loaded in the preset detonation area, the static boundary conditions are converted into dynamic boundary conditions, the time step is set to dt, and the detonation fracturing process is simulated. Finally, after reaching the preset simulation time, the simulation ends, and the fracture network spatial configuration is output. The whole process simulation of hydraulic-detonation combined fracturing transformation can be realized without additional technical means, which is convenient for the optimization design of fracturing parameters and the characterization of fracture network morphology, thereby improving the reservoir transformation effect and oil and gas recovery rate.

[0038] A dynamic and static coupling simulation system for hydraulic-detonation combined fracturing reformation in the second embodiment of the present invention is used to simulate the expansion process of the fracture network of deep oil and gas reservoirs under the combined action of hydraulic fracturing-detonation fracturing to obtain the expansion form of the fracture network; Figure 2 As shown, the system includes: The model building module is configured to select a target simulation area according to a three-dimensional transformation method of a deep oil and gas reservoir; divide the target simulation area into a network, and then build a dynamic and static coupling numerical calculation model of hydraulic-detonation fracturing transformation; the three-dimensional transformation method includes segmented perforation and segmented fracturing transformation; The static simulation module is configured to combine the dynamic-static coupling numerical calculation model of hydraulic-detonation fracturing transformation, complete the overall stress balance of the grid unit under the initial ground stress condition through a discontinuous calculation method, and set the fluid injection rate to simulate the expansion process of the main hydraulic fracturing crack under static conditions. After reaching the preset main crack length, the static simulation ends; The dynamic simulation module is configured to keep the model stress and the main fracture geometry unchanged, load the detonation shock wave in the preset detonation area, convert the static boundary conditions into dynamic boundary conditions, and simulate the expansion process of the detonation fracture network under dynamic conditions. After reaching the preset simulation time, the dynamic simulation ends and outputs the fracture network spatial configuration of the deep oil and gas reservoir, that is, the expansion form of the fracture network.

[0039] It should be noted that the above embodiment provides a dynamic-static coupling simulation system for hydraulic-detonation combined fracturing reform, which is only illustrated by the division of the above functional modules. In practical applications, the above functions can be assigned to different functional modules as needed, that is, the modules or steps in the embodiments of the present invention can be decomposed or combined. For example, the modules in the above embodiments can be combined into one module, or further divided into multiple sub-modules to complete all or part of the functions described above. The names of the modules and steps involved in the embodiments of the present invention are only for distinguishing the modules or steps, and are not regarded as improper limitations of the present invention.

[0040] An electronic device according to the third embodiment of the present invention comprises: at least one processor; and a memory connected to the at least one processor in communication; wherein the memory stores instructions executable by the processor, and the instructions are used to be executed by the processor to implement the above-mentioned dynamic-static coupling simulation method of hydraulic-detonation combined fracturing transformation.

[0041] A computer-readable storage medium according to a fourth embodiment of the present invention stores computer instructions, and the computer instructions are used to be executed by a computer to implement the above-mentioned dynamic-static coupling simulation method for hydraulic-detonation combined fracturing transformation.

[0042] Technicians in the technical field can clearly understand that, for the convenience and brevity of description, the specific working process and related instructions of the electronic device and computer-readable storage medium described above can refer to the corresponding process in the aforementioned method example and will not be repeated here.

[0043] Those skilled in the art should be able to appreciate that the modules and method steps of each example described in conjunction with the embodiments disclosed herein can be implemented with electronic hardware, computer software, or a combination of the two, and the programs corresponding to the software modules and method steps can be placed in random access memory (RAM), memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disks, removable disks, CD-ROMs, or any other form of storage medium known in the technical field. In order to clearly illustrate the interchangeability of electronic hardware and software, the composition and steps of each example have been generally described in the above description according to the function. Whether these functions are performed in electronic hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of the present invention.

[0044] The terms "first", "second", etc. are used to distinguish similar objects rather than to describe or indicate a particular order or sequence.

[0045] The term "comprise" or any other similar term is intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus / device that includes a list of elements includes not only those elements but also other elements not expressly listed, or also includes elements inherent to such process, method, article, or apparatus / device.

[0046] So far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

Claims

1. A dynamic and static coupling simulation method for hydraulic-detonation combined fracturing reconstruction, used to simulate the expansion process of the fracture network of deep oil and gas reservoirs under the combined action of hydraulic fracturing-detonation fracturing, and obtain the expansion form of the fracture network; characterized in that, The method includes: According to the three-dimensional transformation method of deep oil and gas reservoirs, a target simulation area is selected; the target simulation area is network-divided, and then a dynamic-static coupling numerical calculation model of hydraulic-detonation fracturing transformation is constructed; the three-dimensional transformation method includes segmented perforation and segmented fracturing transformation; Combined with the dynamic-static coupling numerical calculation model of hydraulic-detonation fracturing, the overall stress balance of the grid unit under the initial ground stress condition is completed through a discontinuous calculation method, and the fluid injection rate is set to simulate the expansion process of the main hydraulic fracturing crack under static conditions. After the preset main crack length is reached, the static simulation ends; Keeping the model stress and main fracture geometry unchanged, the detonation shock wave is loaded in the preset detonation area, the static boundary conditions are converted into dynamic boundary conditions, and the expansion process of the detonation fracture network under dynamic conditions is simulated. After reaching the preset simulation time, the dynamic simulation ends and the fracture network spatial configuration of the deep oil and gas reservoir, that is, the expansion form of the fracture network, is output.

2. The dynamic-static coupling simulation method of hydraulic-detonation combined fracturing reconstruction according to claim 1 is characterized in that: The dynamic and static coupling numerical calculation model of hydraulic-detonation fracturing transformation is constructed by: According to the three-dimensional transformation method of the deep oil and gas reservoir, a single side area of ​​a single perforation cluster of the deep oil and gas reservoir is selected as a target simulation area; According to the fracturing reconstruction range in terms of the fracturing stage spacing and length, the length and width of the target simulation area are determined, and then the target simulation area is gridded; Combined with the target simulation area after grid division, the dynamic-static coupling boundary and the geometric symmetry boundary are defined, the fluid injection point position, boundary stress, maximum principal stress and minimum principal stress are set, and finally, the dynamic-static coupling numerical calculation model of hydraulic-detonation fracturing transformation is generated; wherein, the fluid injection point position is set at the midpoint of the geometric symmetry boundary.

3. The dynamic-static coupling simulation method of hydraulic-detonation combined fracturing reconstruction according to claim 2 is characterized in that: Define dynamic-static coupling boundaries and geometric symmetry boundaries as follows: The left boundary, the right boundary and the upper boundary of the numerical calculation model are defined as dynamic-static coupling boundaries, and the lower boundary is a geometric symmetry boundary; the dynamic-static coupling boundaries are converted into dynamic-static according to the calculation type during the numerical calculation process.

4. The dynamic-static coupling simulation method of hydraulic-detonation combined fracturing reconstruction according to claim 3 is characterized in that: The numerical simulation calculation method for the expansion process of the main fracture of hydraulic fracturing under static conditions is: If the main hydraulic fracturing crack is a tensile crack, the flow velocity along the crack direction is calculated based on the viscosity of the fluid, the opening of the crack, the pressure of the fluid in the crack, and the length coordinate along the crack direction; The maximum tensile stress criterion is used to determine the crack criticality and obtain the normal stress between units, that is, the normal stress between units at the crack tip; Convert the dynamic-static coupling boundary conditions into fixed boundary conditions to obtain the displacements of the nodes on the boundary; The fluid pressure is calculated based on the flow velocity along the fracture direction; a linear solution equation group under the static condition of hydraulic fracturing is constructed by combining the fluid pressure, the normal stress between the units at the fracture tip, and the displacement at the node on the boundary. KD= F , the static expansion form of the hydraulic fracture network, i.e. the main fracture geometry, is obtained by solving ; K represents the stiffness matrix, D represents the displacement vector to be determined, F Represents the overall load vector acting on the element.

5. The method for dynamic-static coupling simulation of hydraulic-detonation combined fracturing reconstruction according to claim 4 is characterized in that: The simulation calculation method for the expansion process of the detonation pressure crack network under dynamic conditions is: According to the Mohr-Coulomb strength criterion, based on the cohesive strength of rock under static conditions and the cohesive strength of rock under detonation shock wave loading conditions, the dynamic growth factor of rock strength under high strain rate conditions is calculated; According to the changes of cohesion strength and friction angle under high strain rate, combined with the dynamic growth factor of rock strength under the high strain rate condition and the normal stress between the units, the tangential stress between the units is calculated; The conditions of the dynamic-static coupling boundary are converted into a transmission boundary, the transmission phenomenon of the shock wave at the boundary is simulated, and the stiffness matrix correction of the unit on the transmission boundary is obtained; The stiffness matrix of the corresponding unit is corrected based on the stiffness matrix correction amount; combining the stiffness matrix of the corrected unit, the load on the boundary and inside of the unit, and the tangential stress between the units, a linear solution equation group under dynamic detonation shock wave conditions is constructed, and then the dynamic expansion form of the fracture network is solved.

6. The method for dynamic-static coupling simulation of hydraulic-detonation combined fracturing reconstruction according to claim 5, characterized in that: The tangential stress between elements is calculated as follows: ； ； in, σ τ is the tangential stress between units, DIF is the dynamic growth factor of rock strength under high strain rate conditions, C n0 is the cohesive strength of rock under static conditions, obtained through shear test, C n The cohesive strength of rock under detonation shock wave loading conditions is obtained by impact testing rock specimens in uniaxial state using a split Hopkinson pressure bar test. is the internal friction angle, σ n is the normal stress between elements.

7. The method for dynamic-static coupling simulation of hydraulic-detonation combined fracturing reconstruction according to claim 6, characterized in that: The actual extension direction angle of the cracks in rock fracture under detonation load is obtained as follows: ； ； in, represents the hoop stress at the crack tip, The angle that indicates the actual crack expansion direction, Indicates an angle.

8. The method for dynamic-static coupling simulation of hydraulic-detonation combined fracturing reconstruction according to claim 6, characterized in that: The stiffness matrix correction of the unit on the transmission boundary is calculated as follows: ； in, ΔK i For unit The stiffness matrix correction of p is the stiffness of the damper set at the transmission boundary, T i is the displacement transformation matrix of the discontinuous calculation method, F is the direction cosine matrix.

9. The method for dynamic-static coupling simulation of hydraulic-detonation combined fracturing reconstruction according to claim 8, characterized in that: The linear solution equation group under the dynamic detonation shock wave condition is: ； in, M represents the mass matrix of the element, μ is the damping matrix, is the acceleration vector, is the velocity vector.

10. A dynamic and static coupling simulation system for hydraulic-detonation combined fracturing reformation, used to simulate the expansion process of the fracture network of deep oil and gas reservoirs under the combined action of hydraulic fracturing-detonation fracturing, and obtain the expansion form of the fracture network; characterized in that, The system includes: The model building module is configured to select a target simulation area according to a three-dimensional transformation method of a deep oil and gas reservoir; divide the target simulation area into a network, and then build a dynamic and static coupling numerical calculation model of hydraulic-detonation fracturing transformation; the three-dimensional transformation method includes segmented perforation and segmented fracturing transformation; The static simulation module is configured to combine the dynamic-static coupling numerical calculation model of hydraulic-detonation fracturing transformation, complete the overall stress balance of the grid unit under the initial ground stress condition through a discontinuous calculation method, and set the fluid injection rate to simulate the expansion process of the main hydraulic fracturing crack under static conditions. After reaching the preset main crack length, the static simulation ends; The dynamic simulation module is configured to keep the model stress and the main fracture geometry unchanged, load the detonation shock wave in the preset detonation area, convert the static boundary conditions into dynamic boundary conditions, and simulate the expansion process of the detonation fracture network under dynamic conditions. After reaching the preset simulation time, the dynamic simulation ends and outputs the fracture network spatial configuration of the deep oil and gas reservoir, that is, the expansion form of the fracture network.

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