Prediction method of refracturing crack propagation rule and related equipment

Abstract

The invention relates to the field of tight oil development and rock mechanics, and discloses a method and related equipment for predicting the propagation law of refracturing fractures, and the method comprises the steps: determining the geologic characteristics and rock mechanics characteristics of the stratum where the initial fracturing fractures are located; determining the ground stress state of the stratum where the reservoir fracturing crack is located; determining a primary fracture network according to the geological characteristics, the rock mechanical characteristics and the crustal stress state; determining the propagation characteristics of the refracturing crack; and according to the geologic features, the rock mechanical features, the ground stress state and the primary fracture network, combining with the refracturing fracture propagation features to predict the refracturing fracture propagation law. According to the method, the influence of the crustal stress evolution effect on new crack propagation is increased, the prediction accuracy of the crack propagation of the oil well is improved, the efficiency and effect of the oil well refracturing technology are improved, and innovative technical support is provided for efficient development of compact oil reservoirs.

Description

Technical Field

[0001] The invention relates to the field of tight oil development and rock mechanics, and in particular to a method for predicting the expansion law of repeated fracturing cracks and related equipment. Background Art

[0002] In the field of tight oil production, repeated fracturing technology has received widespread attention in recent years as an important means to improve the productivity of oil and gas wells. Although repeated fracturing technology has shown significant results in increasing the production of developed oil and gas wells, it still faces many challenges in practical applications. Among them, the impact of geostress on crack propagation is a key issue. Geostress not only affects the formation and direction of cracks, but also determines the final shape and distribution of cracks and the conductivity, which in turn affects oil and gas production capacity and well group production. Common repeated fracturing technology often ignores the complex effect of heterogeneous geostress on crack propagation, which leads to difficulties in predicting crack behavior and optimizing fracturing design.

[0003] At present, traditional fracture expansion prediction methods often deviate from the actual situation and cannot accurately predict the morphology and distribution of repeated fracturing fractures after the initial fracture network is put into production, which affects the design of repeated fracturing parameters and leads to the failure to achieve the best fracturing effect. In addition, the existing methods are also insufficient in dealing with the complexity and uncertainty of geological data, and it is difficult to adapt to the changing reservoir pressure and stress state. Therefore, it is necessary to develop a new prediction method that can comprehensively consider the influence of geostress and accurately simulate and predict the expansion law of fractures in repeated fracturing. This method should be able to handle complex geostress states, provide a scientific basis for the repeated fracturing design and optimization of oil wells, and ultimately improve the production and economic benefits of oil wells. Summary of the invention

[0004] The purpose of the present invention is to provide a method for predicting the crack expansion law of repeated fracturing and related equipment to solve the technical problem of how to accurately predict the influence of ground stress on crack expansion in repeated fracturing of oil wells.

[0005] The present invention is achieved through the following technical solutions: In a first aspect, the present invention provides a method for predicting the propagation law of repeated fracturing cracks, comprising the following steps: Determine the geological characteristics and rock mechanical characteristics of the formation where the primary fracturing fracture is located; Determine the ground stress state of the formation where the reservoir fracturing cracks are located; Determining the primary fracture network by the geological characteristics and rock mechanical characteristics and the in-situ stress state; Determine the fracture propagation characteristics of repeated fracturing; The repeated fracturing crack expansion law is predicted based on the geological characteristics, rock mechanical characteristics, ground stress state and the initial fracture network combined with the repeated fracturing crack expansion characteristics.

[0006] Preferably, in the step of determining the geological characteristics and rock mechanical characteristics of the formation where the initial fracturing fracture is located, the rock mineral composition is determined by X-ray diffraction, the geological characteristics and rock mechanical characteristics are analyzed based on the rock mineral composition using seismic data and logging data, and a three-dimensional geological model of the reservoir is created based on the geological characteristics and rock mechanical characteristics, wherein the parameters of the three-dimensional geological model include lithology, porosity and permeability.

[0007] Preferably, in the process of determining the ground stress state of the formation where the reservoir fracturing crack is located, the specific process is as follows: The original ground stress is determined by using downhole measurement data and rock mechanics experiments on rock cores, wherein the downhole measurement data includes ground breaking test data and imaging logging data; The in-situ stress state of the stratum where the reservoir fracturing cracks are located is determined based on the original in-situ stress combined with the elastoplastic constitutive equation and the Mohr-Coulomb criterion.

[0008] Preferably, in the process of determining the initial fracture network through the geological characteristics and rock mechanics characteristics and the in-situ stress state, the initial fracture morphology is forward modeled by a fracture mechanics method, and the convex sample set and the non-convex sample set are processed by a density-based clustering algorithm of microseismic data to form an inversion morphology of the initial hydraulic fracture network; the initial fracture network is determined by combining the forward modeled initial fracture morphology and the inversion morphology of the initial hydraulic fracture network.

[0009] Furthermore, the change characteristics of pore pressure and ground stress caused by the initial fracture network production are determined, and the change characteristics of pore pressure and ground stress are analyzed to characterize the reservoir fluid-solid coupling characteristics induced by the initial fracture network depressurization production. The calculation formula of the reservoir fluid-solid coupling characteristics is as follows: Seepage state: u = -k / μ * ∇p Solid mechanics constitutive law: σ = C * (ε - α * ∇p) Fluid continuity equation: ∂p / ∂t - ∇p * (k * ∇p) = Q Among them, u is the velocity, unit m / s; k is the permeability, unit m²; μ is the viscosity, unit Pa·s; ∇p is the pressure gradient, unit Pa / m; σ is the total stress, unit Pa; C is the drainage elastic stiffness parameter, unit Pa; ε is the total strain tensor, α is the effective stress coefficient, t is the time, unit s; Q is the fluid inflow or outflow parameter, unit m³ / s·m³.

[0010] Preferably, in the step of determining the crack extension characteristics of repeated fracturing, the specific process is as follows: The propagation behavior of cracks in the evolved complex stress field is simulated by fracture mechanics and extended finite element method; The fracture network is described based on the propagation behavior in a complex stress field, where nodes and edges are used to represent fracture intersections and fracture segments, and the connectivity and distribution characteristics of the fracture network are analyzed; The crack propagation characteristics of repeated fracturing are determined based on the fracture network.

[0011] Preferably, in the process of predicting the expansion law of repeated fracturing cracks according to the geological characteristics, rock mechanical characteristics, ground stress state and the initial fracture network combined with the repeated fracturing crack expansion characteristics, the specific process is as follows: Comparing and calibrating the geological characteristics, rock mechanical characteristics, ground stress state and initial fracture network to determine the expansion effect and fracturing quality; Based on the expansion effect and fracturing quality, repeated fracturing cracks are predicted to determine the optimal repeated fracturing crack morphology and fracturing parameters.

[0012] In a second aspect, the present invention further provides a prediction system for repeated fracturing crack expansion law, comprising: A first data determination module is used to determine the geological characteristics and rock mechanical characteristics of the formation where the primary fracturing crack is located; The second data determination module is used to determine the ground stress state of the formation where the reservoir fracturing crack is located; A first data processing module is used to determine the primary fracture network according to the geological characteristics and rock mechanical characteristics and the ground stress state; A third data determination module is used to determine the repeated fracturing crack expansion characteristics; The second data processing module is used to predict the expansion law of repeated fracturing cracks according to the geological characteristics, rock mechanical characteristics, ground stress state and the initial fracture network combined with the repeated fracturing crack expansion characteristics.

[0013] In a third aspect, the present invention further provides a mobile terminal, characterized in that it comprises a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, it implements the method for predicting the expansion law of repeated fracturing cracks as described above.

[0014] In a fourth aspect, the present invention further provides a computer-readable storage medium, characterized in that the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the method for predicting the repeated fracturing crack expansion law as described above is implemented.

[0015] Compared with the prior art, the present invention has the following beneficial technical effects: The present invention provides a method for predicting the expansion law of re-fracturing cracks. Based on actual reservoir data, initial fracture network and initial fracture network productivity data, the re-fracturing process of oil wells in tight oil reservoirs is simulated, well sections with similar geostress states, fracture network morphology and productivity distribution are classified and quantified, and then re-fracturing crack prediction is performed. On this basis, the influence of geostress evolution on the expansion of new cracks is increased, the accuracy of fracture expansion prediction of oil wells is improved, the efficiency and effect of oil well re-fracturing technology are improved, and innovative technical support is provided for the efficient development of tight oil reservoirs.

[0016] Furthermore, by combining actual reservoir data, initial fracture networks and production capacity data, the present invention can more accurately simulate the repeated fracturing process, thereby more accurately predicting the expansion law of fractures. This prediction method based on actual data has higher accuracy and reliability than traditional theoretical models or empirical formulas.

[0017] Furthermore, the present invention classifies and quantifies well sections with similar geostress states, fracture network morphology, and production capacity distribution. This classification method helps to identify the commonalities and differences between different well sections, thereby formulating more specific fracturing strategies and optimization plans for different types of well sections. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a flow chart of the method for predicting the expansion law of repeated fracturing cracks in the present invention; Figure 2 This is a diagram showing the effect of repeated fracturing cracks under the action of the stress field in the present invention; Figure 3 It is a schematic diagram of the strip representation of the prediction of the morphology of repeated fracturing cracks in the present invention; Figure 4 This is a schematic diagram of the structure of a prediction system for repeated fracturing crack expansion rules of the present invention; In the figure: 1-first data determination module; 2-second data determination module; 3-first data processing module; 4-third data determination module; 5-second data processing module. DETAILED DESCRIPTION

[0019] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0020] The present invention is further described in detail below in conjunction with the accompanying drawings: The purpose of the present invention is to provide a method for predicting the crack expansion law of repeated fracturing and related equipment to solve the technical problem of how to accurately predict the influence of ground stress on crack expansion in repeated fracturing of oil wells.

[0021] See also Figure 1 and Figure 2 The present invention provides a method for predicting the expansion law of repeated fracturing cracks, comprising the following steps: Step 1, determining the geological characteristics and rock mechanical characteristics of the formation where the primary fracturing fracture is located; Specifically, in the step of determining the geological characteristics and rock mechanical characteristics of the formation where the primary fracturing crack is located, the rock mineral composition is determined by X-ray diffraction, and the geological characteristics and rock mechanical characteristics are analyzed based on the rock mineral composition using seismic data and logging data, and a three-dimensional geological model of the reservoir is created based on the geological characteristics and rock mechanical characteristics, wherein the parameters of the three-dimensional geological model include lithology, porosity and permeability.

[0022] Among them, X-ray diffraction is an effective means of analyzing the mineral composition of rocks. When X-rays are irradiated on rock samples, diffraction occurs, forming specific diffraction patterns. By analyzing these patterns, the mineral composition and content of the rock can be determined.

[0023] In the fusion analysis of seismic and well logging data, seismic data can provide large-scale structural information of the strata, such as faults, folds and other structural features. This information is crucial for understanding the overall structure and stress distribution of the strata.

[0024] Well logging data can reveal the small-scale characteristics of the formation, such as reservoir parameters such as porosity and permeability. These parameters directly affect the expansion of fractures and the flow of oil and gas.

[0025] By fusing and analyzing seismic data and well logging data, we can have a more comprehensive understanding of the geological characteristics and rock mechanical characteristics of the strata, providing accurate basic data for the subsequent creation of three-dimensional geological models and prediction of fracture extension.

[0026] Among them, the three-dimensional geological model can intuitively display the spatial distribution and key parameters of the strata. In the prediction of fracture expansion, the model can be used to simulate the fracture expansion process and analyze the key parameters such as the fracture expansion direction, length, width, etc.

[0027] By comparing the crack expansion under different parameters, the fracturing strategy and construction parameters can be optimized to improve the fracturing effect and oil and gas recovery rate.

[0028] Step 2, determining the ground stress state of the formation where the reservoir fracturing crack is located; Specifically, in the process of determining the ground stress state of the formation where the reservoir fracturing crack is located, the specific process is as follows: The original ground stress is determined by using downhole measurement data and rock mechanics experiments on rock cores, wherein the downhole measurement data includes ground breaking test data and imaging logging data; The in-situ stress state of the stratum where the reservoir fracturing cracks are located is determined based on the original in-situ stress combined with the elastoplastic constitutive equation and the Mohr-Coulomb criterion.

[0029] The downhole measurement data in the present invention includes ground breaking experimental data and imaging logging data. The ground breaking experimental data is obtained by performing a specific pressure test downhole, observing and recording the pressure value when the rock breaks, and thus calculating the original ground stress of the formation. The imaging logging data is obtained by scanning the formation through the logging instrument to obtain information such as the structure and crack distribution of the formation, which can also indirectly reflect the stress state of the formation.

[0030] In the rock mechanics experiment of the core, the present invention takes out the core sample from the stratum by a coring tool, and then performs rock mechanics experiments under laboratory conditions, such as uniaxial compression experiments, triaxial compression experiments, etc., to measure the mechanical parameters of the rock, such as elastic modulus, Poisson's ratio, compressive strength, etc. These parameters can be used to infer the original ground stress of the stratum.

[0031] The present invention uses the elastic-plastic constitutive equation to obtain a mathematical equation of the stress-strain relationship of the material during the stress process. For formation rocks, the stress process often includes both elastic deformation and plastic deformation, so the elastic-plastic constitutive equation is needed to describe its stress-strain relationship.

[0032] The Mohr-Coulomb criterion is used to determine whether shear failure of rock occurs. It is based on parameters such as rock tensile strength, compressive strength and internal friction angle, and can deduce the failure conditions of rock under a specific stress state.

[0033] By combining the original geostress with the elastoplastic constitutive equation and the Mohr-Coulomb criterion, the stress distribution and changes of the formation during the fracturing process can be calculated, thereby determining the geostress state of the formation where the reservoir fracturing cracks are located.

[0034] Step 3, determining the initial fracture network according to the geological characteristics, rock mechanical characteristics and the ground stress state; In the process of determining the initial fracture network through the geological characteristics, rock mechanics characteristics and the in-situ stress state, the initial fracture morphology is forward modeled by fracture mechanics method, and the convex sample set and the non-convex sample set are processed by the density-based clustering algorithm of microseismic data to form the initial fracture network inversion morphology; the initial fracture network is determined by combining the forward modeled initial fracture morphology and the initial fracture network inversion morphology.

[0035] Specifically, the fracture mechanics method uses geological characteristics, rock mechanics characteristics and ground stress state as input parameters in the forward modeling of the initial fracture morphology.

[0036] Application of fracture mechanics theory, such as the KI opening or K-II sliding fracture mechanics model, to calculate the crack propagation path, morphology and size under specific stress conditions.

[0037] The results of the forward modeling provide a first-pass prediction of fracture morphology, that is, a preliminary understanding of how fractures are distributed and propagated in the subsurface.

[0038] Specifically, the method for determining the fracture network inversion morphology is as follows: Determine the direct correlation density at a point: δ(x) = |{p ∈ X | dist(x, p) ≤ ε}| This formula computes the directly reachable density of a point x, that is, the number of points in its ε neighborhood.

[0039] Determine the core point: C(x) = {p ∈ X | δ(p) ≥ minPts} This formula defines core points as points whose directly reachable density is greater than or equal to minPts.

[0040] Determine the boundary points: B(x) = {p ∈ X | ∃q ∈ C(x) such that dist(x, q) ≤ ε} This formula defines boundary points as points within the ε neighborhood of a core point, but not the core point itself.

[0041] Quantization noise: N = X \ (C(X) ∪ B(X)) This formula defines noise as the set of points that are neither core points nor boundary points. These points are considered not to belong to any cluster.

[0042] Reachability representation: reach(p, q) =∀r ∈ X between p and q, δ(r) ≥ minPts This formula defines the reachability between two points p and q. If there is a path between q and p, and every point on the path is either a core point or directly reachable from a core point, then q is reachable from p.

[0043] Determine the cluster: cluster(p) = {q ∈ X | reach(p, q) ∨ reach(q, p)} This formula identifies the cluster to which point p belongs. All points that are reachable from p or can reach p are considered part of the same cluster.

[0044] Among them, the change characteristics of pore pressure and ground stress caused by the initial fracture network production are determined, and the change characteristics of pore pressure and ground stress are analyzed to characterize the reservoir fluid-solid coupling characteristics induced by the initial fracture network depressurization production. The calculation formula of the reservoir fluid-solid coupling characteristics is as follows: Seepage state: u = -k / μ * ∇p Solid mechanics constitutive law: σ = C * (ε - α * ∇p) Fluid continuity equation: ∂p / ∂t - ∇p * (k * ∇p) = Q Among them, u is the velocity, unit m / s; k is the permeability, unit m²; μ is the viscosity, unit Pa·s; ∇p is the pressure gradient, unit Pa / m; σ is the total stress, unit Pa; C is the drainage elastic stiffness parameter, unit Pa; ε is the total strain tensor, α is the effective stress coefficient, t is the time, unit s; Q is the fluid inflow or outflow parameter, unit m³ / s·m³.

[0045] Step 4, determining the crack extension characteristics of repeated fracturing; Specifically, in the step of determining the crack extension characteristics of repeated fracturing, the specific process is as follows: The propagation behavior of cracks in the evolved complex stress field is simulated by fracture mechanics and extended finite element method; Among them, fracture mechanics theory, such as linear elastic fracture mechanics or elastoplastic fracture mechanics, is used to analyze the expansion behavior of cracks in complex stress fields. This includes calculating parameters such as the stress intensity factor and J integral at the crack tip to evaluate the expansion trend and stability of the crack.

[0046] The extended finite element method (XFEM) is used to simulate the crack propagation process. XFEM is a powerful numerical simulation method that can simulate static and dynamic crack propagation while taking into account the nonlinearity and damage evolution of the material. Through XFEM, the crack propagation path, morphology and speed in a complex stress field can be intuitively observed.

[0047] The fracture network is described based on the propagation behavior in a complex stress field, where nodes and edges are used to represent fracture intersections and fracture segments, and the connectivity and distribution characteristics of the fracture network are analyzed; Nodes and edges are used to represent crack intersections and crack segments. Nodes represent the intersections or endpoints of cracks, while edges represent crack segments, i.e., the connecting parts between two nodes.

[0048] Analyze the connectivity and distribution characteristics of the fracture network. Connectivity describes the connection relationship between each fracture segment in the fracture network, such as whether they intersect or are parallel. Distribution characteristics describe the distribution of the fracture network in space, such as the density, direction, and length of the fractures.

[0049] The crack propagation characteristics of repeated fracturing are determined based on the fracture network.

[0050] Among them, based on the description and analysis of the fracture network, the expansion characteristics of repeated fracturing fractures are determined. These characteristics may include the expansion direction, expansion speed, fracture morphology (such as planar expansion, non-planar expansion, vertical expansion, etc.), complexity and connectivity of the fracture network, etc.

[0051] By comparing the fracture extension characteristics under different conditions, the fracturing effect can be evaluated, and the fracturing strategy and construction parameters can be optimized to increase oil and gas recovery.

[0052] In the present invention, crack propagation simulation is carried out, and the propagation behavior of cracks in the evolved complex stress field is simulated by using fracture mechanics method and extended finite element method. On this basis, crack network analysis is carried out, and the graph theory method in complex network theory is applied to describe the crack network: nodes and edges are used to represent crack intersections and crack segments, and their connectivity and distribution characteristics are analyzed.

[0053] The specific process is as follows: With the extended finite element method, the standard finite element approximation is enriched by including additional functions that capture the behavior near the fracture tip.

[0054] The locations of cracks are defined by a level set function and used to determine the enrichment domain.

[0055] Use uniform partitioning to ensure smooth blending of rich and standard displacement fields.

[0056] The weak form of the equilibrium equations is used to derive a system of equations that will solve for the nodal displacements.

[0057] The crack propagation timing and path are determined by using the fracture mechanics crack propagation criterion. Crack propagation is determined based on the energy release rate at the fracture tip.

[0058] The level set function is updated at each time step to reflect the current propagation status of the refracturing fracture.

[0059] Step 5, predicting the propagation law of repeated fracturing cracks according to the geological characteristics, rock mechanical characteristics, ground stress state and the initial fracture network combined with the repeated fracturing crack propagation characteristics.

[0060] Specifically, in the process of predicting the expansion law of repeated fracturing cracks according to the geological characteristics, rock mechanics characteristics, ground stress state and the initial fracture network combined with the repeated fracturing crack expansion characteristics, the specific process is as follows: Comparing and calibrating the geological characteristics, rock mechanical characteristics, ground stress state and initial fracture network to determine the expansion effect and fracturing quality; Based on the expansion effect and fracturing quality, repeated fracturing cracks are predicted to determine the optimal repeated fracturing crack morphology and fracturing parameters.

[0061] Example 1 Taking a well in a tight oil reservoir X as an example, this embodiment provides a method for predicting the propagation law of repeated fracturing cracks, and the specific implementation steps are as follows: S1: Determine the three-dimensional distribution of minerals, porosity, permeability, saturation, and rock mechanical parameters of the reservoir in the work area to form an initial three-dimensional model. Take this modeling as an example: The stratified porosity columns are: [0.0334, 0.1131, 0.1239, 0.0587, 0.0854, 0.0873,0.0650, 0.0939, 0.0222, 0.0236]; The stratified permeability series is: [7.49, 2.26, 5.33, 4.80, 3.18, 4.28, 3.80, 6.72, 3.78, 5.17]; The stratified saturation series is: [0.85, 0.81, 0.78, 0.76, 0.75, 0.76, 0.87, 0.77, 0.81, 0.80]; The series of layered elastic modulus is: [35.19, 32.49, 33.21, 30.26, 39.04, 39.93, 36.87, 41.69, 40.93, 29.22]; The layered brittleness series is: [0.74, 0.61, 0.75, 0.66, 0.79, 0.64, 0.80, 0.73, 0.60, 0.66].

[0062] S2: Establish a geostress model, collect 20 sets of core rock mechanics experimental data and imaging logging data from adjacent wells in the work area, totaling 1 well, establish an initial geostress model of the work area (thickness 100m, area 10km2), and judge that the work area is a strike-slip fault stress mechanism.

[0063] S3: The initial fracture network size and affected range are characterized by inversion of initial fracturing operation data and microseismic data, as shown in Table 1;

[0064] Table 1 Characterization of initial seam network size and affected range S4: Collect the production history data of a well in the X tight oil reservoir, and characterize the degree and range of pressure drop and ground stress changes by combining the reservoir fluid-solid coupling model.

[0065] S5: Determine the re-fracturing time and segment cluster location, perform re-fracturing crack prediction, and evaluate the fracturing effect, such as Figure 3 shown.

[0066] S6: Compare and calibrate the extension path and morphology of repeated fracturing cracks with rock mechanics and geomechanics models to clarify the extension effect and fracturing quality.

[0067] S7: Repeat the repeated fracturing crack prediction in S5, and finally determine the optimal repeated fracturing crack morphology and fracturing parameters. The final ground stress results are shown in Table 2.

[0068]

[0069] Table 2 Ground stress results In summary, this embodiment provides a method for predicting the expansion law of repeated fracturing cracks. Based on actual reservoir data, initial fracture network and initial fracture network productivity data, the repeated fracturing process of oil wells in tight oil reservoirs is simulated, and well sections with similar geostress states, fracture network morphology and productivity distribution are classified and quantified, and then repeated fracturing cracks are predicted. On this basis, the influence of geostress evolution on the expansion of new fractures is increased, the accuracy of fracture expansion prediction of oil wells is improved, the efficiency and effect of oil well repeated fracturing technology are improved, and innovative technical support is provided for the efficient development of tight oil reservoirs.

[0070] Example 2 according to Figure 4 As shown, this embodiment also provides a prediction system for repeated fracturing crack expansion law, including: The first data determination module 1 is used to determine the geological characteristics and rock mechanical characteristics of the formation where the primary fracturing crack is located; The second data determination module 2 is used to determine the ground stress state of the formation where the reservoir fracturing crack is located; A first data processing module 3, used to determine the primary fracture network according to the geological characteristics and rock mechanical characteristics and the ground stress state; The third data determination module 4 is used to determine the crack extension characteristics of repeated fracturing; The second data processing module 5 is used to predict the expansion law of repeated fracturing cracks according to the geological characteristics, rock mechanical characteristics, ground stress state and the initial fracture network combined with the repeated fracturing crack expansion characteristics.

[0071] Example 3 The present invention also provides a mobile terminal, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, such as a prediction program for repeated fracturing crack expansion rules.

[0072] When the processor executes the computer program, the steps of the method for predicting the propagation law of repeated fracturing cracks are implemented, for example: Determine the geological characteristics and rock mechanical characteristics of the formation where the primary fracturing fracture is located; Determine the ground stress state of the formation where the reservoir fracturing cracks are located; Determining the primary fracture network by the geological characteristics and rock mechanical characteristics and the in-situ stress state; Determine the fracture propagation characteristics of repeated fracturing; The repeated fracturing crack expansion law is predicted based on the geological characteristics, rock mechanical characteristics, ground stress state and the initial fracture network combined with the repeated fracturing crack expansion characteristics.

[0073] Alternatively, when the processor executes the computer program, the functions of each module in the above system are realized, for example: The first data determination module 1 is used to determine the geological characteristics and rock mechanical characteristics of the formation where the primary fracturing crack is located; The second data determination module 2 is used to determine the ground stress state of the formation where the reservoir fracturing crack is located; A first data processing module 3, used to determine the primary fracture network according to the geological characteristics and rock mechanical characteristics and the ground stress state; The third data determination module 4 is used to determine the crack extension characteristics of repeated fracturing; The second data processing module 5 is used to predict the expansion law of repeated fracturing cracks according to the geological characteristics, rock mechanical characteristics, ground stress state and the initial fracture network combined with the repeated fracturing crack expansion characteristics.

[0074] Exemplarily, the computer program may be divided into one or more modules / units, which are stored in the memory and executed by the processor to implement the present invention. The one or more modules / units may be a series of computer program instruction segments capable of implementing specific functions, which are used to describe the execution process of the computer program in the mobile terminal.

[0075] For example, the computer program may be divided into a first data determination module 1, a second data determination module 2, a first data processing module 3, a third data determination module 4 and a second data processing module 5, and the specific functions of each module are as follows: The first data determination module 1 is used to determine the geological characteristics and rock mechanical characteristics of the formation where the primary fracturing crack is located; The second data determination module 2 is used to determine the ground stress state of the formation where the reservoir fracturing crack is located; A first data processing module 3, used to determine the primary fracture network according to the geological characteristics and rock mechanical characteristics and the ground stress state; The third data determination module 4 is used to determine the crack extension characteristics of repeated fracturing; The second data processing module 5 is used to predict the expansion law of repeated fracturing cracks according to the geological characteristics, rock mechanical characteristics, ground stress state and the initial fracture network combined with the repeated fracturing crack expansion characteristics.

[0076] The mobile terminal may be a computing device such as a desktop computer, a notebook, a palm computer, a cloud server, etc. The mobile terminal may include, but is not limited to, a processor and a memory.

[0077] The processor may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor, etc. The processor is the control center of the mobile terminal, and uses various interfaces and lines to connect various parts of the entire mobile terminal.

[0078] The memory may be used to store the computer programs and / or modules, and the processor implements various functions of the mobile terminal by running or executing the computer programs and / or modules stored in the memory and calling the data stored in the memory.

[0079] The memory may mainly include a program storage area and a data storage area, wherein the program storage area may store an operating system, an application required for at least one function (such as a sound playback function, an image playback function, etc.), etc.; the data storage area may store data created according to the use of the mobile phone (such as audio data, a phone book, etc.), etc. In addition, the memory may include a high-speed random access memory, and may also include a non-volatile memory, such as a hard disk, a memory, a plug-in hard disk, a smart memory card (SmartMediaCard, SMC), a secure digital (SecureDigital, SD) card, a flash card (FlashCard), at least one disk storage device, a flash memory device, or other volatile solid-state storage devices.

[0080] Example 4 The present invention also provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the method for predicting the expansion law of repeated fracturing cracks are implemented.

[0081] If the module / unit integrated in the mobile terminal is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium.

[0082] Based on such understanding, the present invention implements all or part of the processes in the above method, and can also be completed by instructing related hardware through a computer program, and the computer program can be stored in a computer-readable storage medium, and when the computer program is executed by a processor, the steps of the above method for predicting the expansion law of repeated fracturing cracks can be implemented. Wherein, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form, etc.

[0083] The computer-readable medium may include: any entity or device capable of carrying the computer program code, recording medium, USB flash drive, mobile hard disk, magnetic disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signal, telecommunication signal and software distribution medium, etc.

[0084] It should be noted that the content contained in the computer-readable medium can be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, computer-readable media does not include electrical carrier signals and telecommunication signals.

[0085] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for predicting the propagation law of repeated fracturing cracks, characterized in that: The steps include: Determine the geological characteristics and rock mechanical characteristics of the formation where the primary fracturing fracture is located; Determine the ground stress state of the formation where the reservoir fracturing cracks are located; Determine the primary fracture network through the geological characteristics, rock mechanical characteristics and ground stress state; Determine the fracture propagation characteristics of repeated fracturing; The repeated fracturing crack expansion law is predicted based on the geological characteristics, rock mechanical characteristics, ground stress state and initial fracture network in combination with the repeated fracturing crack expansion characteristics.

2. The method for predicting the expansion law of repeated fracturing cracks according to claim 1, characterized in that: In the step of determining the geological characteristics and rock mechanical characteristics of the formation where the primary fracturing crack is located, the rock mineral composition is determined by X-ray diffraction, the geological characteristics and rock mechanical characteristics are analyzed based on the rock mineral composition using seismic data and logging data, and a three-dimensional geological model of the reservoir is created based on the geological characteristics and rock mechanical characteristics, wherein the parameters of the three-dimensional geological model include lithology, porosity and permeability.

3. The method for predicting the expansion law of repeated fracturing cracks according to claim 1, characterized in that: In the process of determining the ground stress state of the formation where the reservoir fracturing crack is located, the specific process is as follows: The original ground stress is determined by using downhole measurement data and rock mechanics experiments on rock cores, wherein the downhole measurement data includes ground breaking test data and imaging logging data; The in-situ stress state of the stratum where the reservoir fracturing cracks are located is determined based on the original in-situ stress combined with the elastoplastic constitutive equation and the Mohr-Coulomb criterion.

4. The method for predicting the expansion law of repeated fracturing cracks according to claim 1, characterized in that: In the process of determining the initial fracture network through the geological characteristics and rock mechanical characteristics and the in-situ stress state, the initial fracture morphology is forward modeled by the fracture mechanics method, and the convex sample set and the non-convex sample set are processed by the microseismic data based on the density clustering algorithm to form the initial fracture network inversion morphology; The initial fracture network is determined by combining the forward modeling initial fracture morphology and the inversion morphology of the initial hydraulic fracture network.

5. The method for predicting the propagation law of repeated fracturing cracks according to claim 4, characterized in that: The pore pressure and ground stress change characteristics caused by the initial fracture network production are determined, and the pore pressure and ground stress change characteristics are analyzed to characterize the reservoir fluid-solid coupling characteristics induced by the initial fracture network depressurization production. The calculation formula of the reservoir fluid-solid coupling characteristics is as follows: Seepage state: u = -k / μ * ∇p Solid mechanics constitutive law: σ = C * (ε - α * ∇p) Fluid continuity equation: ∂p / ∂t - ∇p * (k * ∇p) = Q Among them, u is the velocity, unit m / s; k is the permeability, unit m²; μ is the viscosity, unit Pa·s; ∇p is the pressure gradient, unit Pa / m; σ is the total stress, unit Pa; C is the drainage elastic stiffness parameter, unit Pa; ε is the total strain tensor, α is the effective stress coefficient, t is the time, unit s; Q is the fluid inflow or outflow parameter, unit m³ / s·m³.

6. The method for predicting the propagation law of repeated fracturing cracks according to claim 1, characterized in that: In the step of determining the repeated fracturing crack extension characteristics, the specific process is as follows: The propagation behavior of cracks in the evolved complex stress field is simulated by fracture mechanics and extended finite element method; The fracture network is described based on the propagation behavior in a complex stress field, where nodes and edges are used to represent fracture intersections and fracture segments, and the connectivity and distribution characteristics of the fracture network are analyzed; The crack propagation characteristics of repeated fracturing are determined based on the fracture network.

7. The method for predicting the expansion law of repeated fracturing cracks according to claim 1, characterized in that: In the process of predicting the expansion law of repeated fracturing cracks according to the geological characteristics, rock mechanics characteristics, ground stress state and the initial fracture network combined with the repeated fracturing crack expansion characteristics, the specific process is as follows: Comparing and calibrating the geological characteristics, rock mechanical characteristics, ground stress state and initial fracture network to determine the expansion effect and fracturing quality; Based on the expansion effect and fracturing quality, repeated fracturing cracks are predicted to determine the optimal repeated fracturing crack morphology and fracturing parameters.

8. A prediction system for repeated fracturing crack expansion law, characterized in that: include: A first data determination module is used to determine the geological characteristics and rock mechanical characteristics of the formation where the primary fracturing crack is located; The second data determination module is used to determine the ground stress state of the formation where the reservoir fracturing crack is located; A first data processing module is used to determine the primary fracture network according to the geological characteristics and rock mechanical characteristics and the ground stress state; A third data determination module is used to determine the repeated fracturing crack expansion characteristics; The second data processing module is used to predict the expansion law of repeated fracturing cracks according to the geological characteristics, rock mechanical characteristics, ground stress state and the initial fracture network combined with the repeated fracturing crack expansion characteristics.

9. A mobile terminal, characterized in that: The method comprises a memory, a processor and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the method for predicting the expansion law of repeated fracturing cracks as claimed in any one of claims 1 to 7 is implemented.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the method for predicting the repeated fracturing crack extension law according to any one of claims 1 to 7 is implemented.

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