A method and device for simulating interwell interference of a multistage fracturing well

Abstract

The present application relates to the field of oil stereo well fracturing, and particularly relates to a stereo well fracturing multi-fracture optimization method and device, the present application firstly develops a single cluster hydraulic fracture expansion calculation function program package, then carries out multi-cluster hydraulic fracture synchronous simulation, then carries out expansion simulation on single well multi-stage multi-cluster fracturing fracture and multi-well multi-stage multi-cluster fracturing hydraulic fracture, then sets stereo well quantity, horizontal section three-dimensional space distribution, each well cluster design, reservoir lithology and ground stress, and determines multiple different fracturing modes of stereo well, finally takes the total area of stereo well fracturing fracture as an objective function, selects a target stereo well fracturing mode from the multiple different fracturing modes, and forms a well group fracturing design optimization strategy; the present application realizes qualitative upgrading and expansion on fracturing time in any order sequence and any layout space, and can fully consider the fracturing fracture interference interaction characteristics between multiple wells.

Description

Technical Field

[0001] This invention relates to the field of three-dimensional well fracturing in oil, and particularly to a method and apparatus for optimizing multiple fractures in three-dimensional well fracturing. Background Technology

[0002] my country's technically recoverable shale oil resources amount to 5.5 billion tons, gradually becoming a key force in the country's oil and gas production. Unconventional oil and gas reservoirs are extremely tight, necessitating reservoir stimulation techniques such as hydraulic fracturing to construct large-area and complex fracture networks within these tight reservoirs. This connects the underground tight reservoirs, allowing oil and gas to seep from the reservoir through artificial fractures to the wellbore, ultimately leading to industrial-scale oil and gas production. In the development of unconventional oil and gas reservoirs, long horizontal well sections combined with densely cut volumetric fracture networks have become the primary method for unconventional reservoir stimulation. The use of a well factory model with multiple horizontal wells for integrated fracturing to achieve three-dimensional development, and well cluster fracturing, are gradually becoming a core technology for shale oil reservoir stimulation.

[0003] However, compared to single-well fracturing, the interference process between wells and fractures in well cluster fracturing is more complex. In multi-well fracturing operations, not only are there strong interferences between hydraulic fractures of different levels and sections between wells, but existing hydraulic fractures in other wells within the multi-well cluster also severely interfere with the hydraulic fractures currently being propagated. During multi-well coordinated fracturing, complex interference characteristics are exhibited in both the temporal and spatial dimensions.

[0004] The effectiveness of fracturing in multi-stage wells is influenced by multiple factors, including reservoir mechanical properties, stratified geostress characteristics, the number of multi-stage wells, their spatial distribution, cluster distribution, fracturing parameters, and the order of fracturing methods. Currently, fracturing operations suffer from significant haphazardness and unclear controlling factors, necessitating optimization of the multi-stage well fracturing process and methods. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method and apparatus for simulating inter-well interference in multi-fracture well fracturing, which solves the problems existing in the prior art.

[0006] According to one aspect of the present invention, a method for simulating inter-well interference in multi-fracture well fracturing is provided, comprising the following steps:

[0007] Step S1: Based on the single-cluster three-dimensional hydraulic fracture propagation fluid-structure interaction mathematical calculation model, develop a single-cluster hydraulic fracture propagation calculation function package;

[0008] S2: Based on the single-cluster hydraulic fracture propagation calculation function package, perform synchronous simulation of multiple cluster hydraulic fractures to obtain simulation results of multi-cluster hydraulic fracture propagation.

[0009] S3: Based on the simulation results of the propagation of the multi-cluster hydraulic fractures, the propagation simulation of multi-stage multi-cluster hydraulic fractures in a single well and multi-stage multi-cluster hydraulic fractures in multiple wells is carried out to obtain the morphology, fracture width, induced stress and pressure changes of each stage and cluster of fractures in the whole process of hydraulic fracturing.

[0010] Step S4: Set the number of 3D wells, the three-dimensional spatial distribution of the horizontal section, the design of each well cluster, the reservoir lithology and geostress, and determine the various fracturing methods for the 3D wells;

[0011] Step S5: Using the maximum total fracture area of ​​multiple three-dimensional wells as the objective function, select the target three-dimensional well fracturing method from the various fracturing methods, and form a well group fracturing design optimization strategy.

[0012] Preferably, the single-cluster hydraulic fracture propagation calculation function package is specifically divided into two versions, A and B. Version A outputs the injection point pressure as the variable, and the injection point pressure is used for the flow rate Q of each cluster. i =[Q1,Q2,...,Q n The iterative solution of []; Version B is used to sequentially output all unit state variables of crack propagation given a certain cluster flow.

[0013] Preferably, all unit state variables of the crack propagation include the crack width W. I Pressure distribution P I .

[0014] Preferably, in step S2, the simulation results of multi-cluster hydraulic fracture propagation include iterative solutions for the flow distribution of multi-cluster fractures at each time step, solutions for the multi-cluster fracture propagation induced stress term, and updated solutions for the state variables of all elements of each fracture.

[0015] Preferably, the calculation method for solving the multi-crack propagation induced stress term is as follows:

[0016]

[0017] Where I and J represent the numbers of the hydraulic fractures. This represents the induced stress caused by other cracks (J≠I) and acting on the normal stress vector of crack I, in Pa; H. IJ The influence of crack J (J≠I) on the normal stress of crack I; W J P represents the column vector consisting of the widths of all elements in the J-th crack, m; I This represents the fluid pressure at the midpoint of all elements in crack I, in Pa; This represents the normal stress vector acting on crack I, expressed in Pa; A. II W represents the stress influence coefficient generated by the opening degree of all elements in crack I on each element of crack I; ILet m represent the column vector formed by the widths of all elements of the I-th crack.

[0018] Preferably, the iterative calculation method for the flow distribution of multiple crack clusters is as follows:

[0019] Consider the pressure value p of the fracture element at the injection point closest to the horizontal wellhead. w,fi Friction of the perforation hole p pf,fi and the frictional resistance along the wellbore p cf,fi and the stress induced by cracks within the segment Add the induced stress interference term to the elastic equation of the hydraulic fracture;

[0020] Set the crack width, flow rate, and pressure at the initial time. Let the time be T and the time step be ΔT. For all expanding cracks, determine whether the outer unit of the crack tip is expanding outward at each time step.

[0021] Pressure p near the heel of a fractured section in a horizontal well o The pressure value p of the fracture element at the injection point closest to the horizontal wellhead w,fi Friction of the perforation hole p pf,fi and the frictional resistance along the wellbore p cf,fi satisfy:

[0022] p o =p w,fi +p pf,fi +p cf,fi (6)

[0023] Where p w,fi p pf,fi p cf,fi All about Q i The function. p w,fi By solving P in formula (5) I Find p pf,fi p cf,fi They are represented as follows:

[0024]

[0025]

[0026] Where ρ s This indicates the fluid density, expressed in kg / m³. 3 ;n p,fi d represents the number of apertures in a single cluster. p,fi Indicates the diameter of the aperture, in meters (m); K d λ represents the dimensionless throttling coefficient, ranging from 0.5 to 0.9; L represents the fluid wellbore friction length, in meters; λ is the friction resistance coefficient (dimensionless).

[0027] In version A of the single-cluster hydraulic fracture propagation calculation function package, formula (5) is written as equation P. w,fi =f(Q) i In the form of ), and as part of the pressure balance equation, the flow rate Q of each perforation cluster pumped is... i =[Q1,Q2,...,Q n As an unknown in the pressure balance equation, the fluid inflow distribution for each cluster of hydraulic fractures is obtained by iteratively solving the Newton-Raphson formula. Based on this, version B of the single cluster hydraulic fracture propagation calculation function package is called to sequentially output all the unit state variables of the fracture propagation.

[0028] Then, the loop continues to the next time step, determining whether the hydraulic fracture has reached the expansion condition of the outer fracture element, updating the stress influence coefficient, and repeating the above steps until the time ends.

[0029] Then, the loop continues to the next time step to determine whether the hydraulic fracture has reached the expansion condition of the outer fracture element. Based on the updated fracture element, the stress influence coefficient is updated, and the above steps are repeated until the time ends.

[0030] Based on this, version B of the single-cluster hydraulic fracture propagation calculation function package is called to sequentially output all element state variables of the fracture propagation.

[0031] Preferably, the method for determining the expansion of peripheral crack elements uses implicit level sets or damage element methods to determine whether the crack tip element has opened.

[0032] Preferably, in step S3, when conducting simulations of multi-stage, multi-cluster fracturing fracture propagation in a single well and multi-stage, multi-cluster fracturing hydraulic fracture propagation in multiple wells, stress interference terms also need to be considered. It includes: intra-segment crack-induced stress term Inter-segment crack induced stress term Inter-well induced stress term Among them are The overflow stress interference term is considered in formula (5) and solved to obtain the morphology, fracture width, induced stress and pressure change of each cluster of fractures at each level of the well during the entire fracturing process.

[0033] According to another aspect of the present invention, a three-dimensional well fracturing multi-fracture inter-well interference simulation device is provided. This device employs the aforementioned three-dimensional well fracturing multi-fracture inter-well interference simulation method, and the device comprises:

[0034] The package building module is based on a single-cluster three-dimensional hydraulic fracture propagation fluid-structure interaction mathematical calculation model, and develops a single-cluster hydraulic fracture propagation calculation function package.

[0035] The multi-cluster hydraulic fracture simulation module, based on the single-cluster hydraulic fracture propagation calculation function package, performs synchronous simulation of multiple cluster hydraulic fractures to obtain simulation results of multi-cluster hydraulic fracture propagation.

[0036] The multi-stage multi-cluster fracturing fracture simulation module, based on the multi-cluster hydraulic fracture propagation simulation results, performs propagation simulations of multi-stage multi-cluster fracturing fractures in a single well and multi-well multi-stage multi-cluster fracturing hydraulic fractures, and obtains the morphology, fracture width, induced stress and pressure changes of each stage and cluster of fractures in the whole fracturing process.

[0037] The fracturing method determination module is used to set the number of 3D wells, the three-dimensional spatial distribution of horizontal sections, the design of each well cluster, reservoir lithology and geostress, and to determine various fracturing methods for the 3D wells.

[0038] The present invention has the following technical effects:

[0039] This invention provides a method for simulating and optimizing fracturing in a three-dimensional well cluster. First, based on a single-cluster three-dimensional hydraulic fracture propagation fluid-structure interaction mathematical calculation model, a single-cluster hydraulic fracture propagation calculation function package is developed. Then, based on the single-cluster hydraulic fracture propagation calculation function package, simultaneous simulation of multi-cluster hydraulic fractures is performed to obtain the multi-cluster hydraulic fracture propagation simulation results. Next, based on the multi-cluster hydraulic fracture propagation simulation results, propagation simulations are performed on multi-stage, multi-cluster fracturing fractures in a single well and multi-stage, multi-cluster fracturing fractures in multiple wells, obtaining the morphology and fracture characteristics of each stage and cluster of fractures throughout the entire fracturing process. The study investigates the width, induced stress, and pressure changes of the fractures. It then sets the number of 3D wells, the three-dimensional spatial distribution of horizontal sections, the design of each well cluster, reservoir lithology, and geostress, and determines various fracturing methods for the 3D wells. Finally, using the maximum total fracture area from multiple 3D wells as the objective function, it selects the target 3D well fracturing method from the various fracturing methods, forming a well cluster fracturing design optimization strategy. This overcomes the problems of high blindness in fracturing construction and unclear controlling factors in existing technologies, providing a scientific basis for the optimal selection of 3D well development schemes under unconventional tight reservoir well factory models. Compared to the usual simulation that only considers the propagation of multiple clusters of fractures in a single well section, this study only considers the interference between fractures within a single fracturing section at the same time and distance within a limited space. The simulation method proposed in this invention is based on the single function of the original simulation method. By constructing an algorithm for arbitrary combination of multiple single segments and multiple clusters in time and space, it achieves a qualitative upgrade and expansion regardless of the arbitrary sequence of fracturing time and arbitrary layout space. It can fully consider the interference and interaction characteristics of fracturing fractures between multiple wells, and upgrade to the simulation of multiple wells, multiple segments and multiple clusters. Furthermore, by maximizing the total area of ​​all fracturing fractures in all wells as the optimization objective, it provides a solid foundation for the optimization of parameters such as three-dimensional well layout, fracturing sequence, fracturing construction parameters, and inter-well anti-channeling in large reservoir areas. Attached Figure Description

[0040] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0041] Figure 1 This is a schematic flowchart of a method for simulating inter-well interference in multi-fracture well fracturing according to an embodiment of the present invention;

[0042] Figure 2 This is a conceptual diagram of three-dimensional well fracturing provided in an embodiment of the present invention;

[0043] Figure 3 This is the induced stress superposition diagram provided in the embodiments of the present invention;

[0044] Figure 4 This is a multi-cluster fluid flow and pressure balance distribution diagram provided in an embodiment of the present invention;

[0045] Figure 5 This is a schematic diagram of sequential fracturing provided in an embodiment of the present invention;

[0046] Figure 6 This is a schematic diagram of simultaneous fracturing provided in an embodiment of the present invention;

[0047] Figure 7 This is a schematic diagram of direct pressure fracturing provided in an embodiment of the present invention. Detailed Implementation

[0048] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0049] See Figure 1 , Figure 1 This is a flowchart illustrating a method for simulating inter-well interference in multi-fracture well fracturing according to an embodiment of the present invention, which will be combined with... Figure 1 The steps shown are explained. For example... Figure 1 As shown, a method for simulating inter-well interference in multi-fracture well fracturing includes the following steps:

[0050] Step S1: Based on the single-cluster three-dimensional hydraulic fracture propagation fluid-structure interaction mathematical calculation model, develop a single-cluster hydraulic fracture propagation calculation function package.

[0051] In some embodiments, hydraulic fracture propagation refers to the process during hydraulic fracturing where high-pressure fluid (fracturing fluid) is injected into the formation, causing the formation rock to fracture and form cracks, which then extend and propagate under pressure. This process is influenced by various factors, such as the distribution of geostress (including maximum horizontal principal stress, minimum horizontal principal stress, and vertical stress), rock mechanical properties (elastic modulus, Poisson's ratio, tensile strength, etc.), fracturing fluid properties (viscosity, flow rate, injection rate, etc.), and perforation parameters.

[0052] In the mathematical calculation model of fluid-structure interaction for the propagation of a single-cluster three-dimensional hydraulic fracture, the viscous fluid flow within the hydraulic fracture follows Poiseuille's law, and the fluid velocity within the hydraulic fracture can be expressed as:

[0053]

[0054] In the formula, q is the flow velocity of the fracturing fluid in the fracture, p is the fluid pressure, w is the fracture width in each crack element, and μ is the viscosity of the fracturing fluid. The gradient operator is used along the path within the crack;

[0055] The mass balance equation for incompressible fracturing fluid flowing within a hydraulic fracture can be expressed as:

[0056]

[0057] In the formula, t is time, and Q is... I For fracturing fluid inflow, δ is the Dirac delta function representing the point source;

[0058] Considering the balance of fracturing fluid flow rate (flux) entering and exiting each crack element volume, based on the finite volume method, we can obtain:

[0059] w t -w t-1 =Δt[B(w t )p]+ΔtQ I δ (3)

[0060] In the above formula, w t and w t-1 These are the crack widths of the current time unit and the previous time unit, respectively; Δt is the time unit step size; and B is the coefficient of the fluid lubrication equation.

[0061] Based on this, a single-cluster three-dimensional hydraulic fracture propagation fluid-structure interaction mathematical calculation model is constructed. The above functional relationship is implemented in a program and encapsulated into a single-cluster hydraulic fracture propagation calculation function package. This package can be used as an independent module for convenient subsequent multi-fracture simulation.

[0062] It is worth emphasizing that this package is specifically divided into two versions, A and B. Version A outputs the injection point pressure as the variable, which is used to measure the flow rate Q of each cluster. i =[Q1,Q2,...,Q n Iterative solution; Version B is used to sequentially output all element state variables of crack propagation, including crack width W, given a fixed cluster flow rate. I Pressure distribution P I wait.

[0063] S2: Based on the single-cluster hydraulic fracture propagation calculation function package, perform synchronous simulation of multiple cluster hydraulic fractures to obtain simulation results of multi-cluster hydraulic fracture propagation.

[0064] The simulation results of multi-cluster hydraulic fracture propagation include iterative solutions for the flow distribution of multi-cluster fractures at each time step, solutions for the multi-cluster fracture propagation induced stress term, and updated solutions for the state variables of all elements of each fracture.

[0065] Among them, the state variables of all elements of each crack include the crack width and pressure;

[0066] The calculation method for solving the stress term induced by multi-crack propagation is as follows:

[0067]

[0068]

[0069] Where I and J represent the numbers of the hydraulic fractures. This represents the induced stress caused by other cracks (J≠I) and acting on the normal stress vector of crack I, in Pa; H. IJ The influence of crack J (J≠I) on the normal stress of crack I; W J P represents the column vector consisting of the widths of all elements in the J-th crack, m; I This represents the fluid pressure at the midpoint of all elements in crack I, in Pa; This represents the normal stress vector acting on crack I, expressed in Pa; A. II W represents the stress influence coefficient generated by the opening degree of all elements in crack I on each element of crack I; I Let m represent the column vector formed by the widths of all elements of the I-th crack.

[0070] Furthermore, the iterative solution calculation method for the flow distribution of multiple crack clusters is as follows:

[0071] Consider the pressure value p of the fracture element at the injection point closest to the horizontal wellhead. w,fi Friction of the perforation hole p pf,fi and the frictional resistance along the wellbore p cf,fiand the stress induced by cracks within the segment Add the induced stress interference term to the elastic equation of the hydraulic fracture;

[0072] Set the crack width, flow rate, and pressure at the initial time. Let the time be T and the time step be ΔT. For all expanding cracks, determine whether the outer unit of the crack tip is expanding outward at each time step.

[0073] Pressure p near the heel of a fractured section in a horizontal well o The pressure value p of the fracture element at the injection point closest to the horizontal wellhead w,fi Friction of the perforation hole p pf,fi and the frictional resistance along the wellbore p cf,fi satisfy:

[0074] p o =p w,fi +p pf,fi +p cf,fi (6)

[0075] Where p w,fi p pf,fi p cf,fi All about Q i The function. p w,fi By solving P in formula (5) I Find p pf,fi p cf,fi They are represented as follows:

[0076]

[0077] Where ρ s This indicates the fluid density, expressed in kg / m³. 3 ;n p,fi d represents the number of apertures in a single cluster. p,fi Indicates the diameter of the aperture, in meters (m); K d λ represents the dimensionless throttling coefficient, ranging from 0.5 to 0.9; L represents the fluid wellbore friction length, in meters; λ is the friction resistance coefficient (dimensionless).

[0078] In version A of the single-cluster hydraulic fracture propagation calculation function package, formula (5) is written as equation P. w,fi =f(Q) i In the form of ), and as part of the pressure balance equation, the flow rate Q of each perforation cluster pumped is... i =[Q1,Q2,...,Q nAs an unknown in the pressure balance equation, the flow rate distribution for each cluster of hydraulic fractures is obtained through iterative solutions using the Newton-Raphson formula. Based on this, version B of the single-cluster hydraulic fracture propagation calculation function package is called to sequentially output all element state variables of the fracture propagation, including the fracture width W. I Pressure distribution P I wait;

[0079] Then, the loop continues to the next time step, determining whether the hydraulic fracture has reached the expansion condition of the outer fracture element, updating the stress influence coefficient, and repeating the above steps until the time ends.

[0080] Among them, the method for judging the expansion of the outer crack element adopts the implicit level set or the damage element method to judge whether the crack tip element has opened.

[0081] Then, the loop continues to the next time step to determine whether the hydraulic fracture has reached the expansion condition of the outer fracture element. Based on the updated fracture element, the stress influence coefficient is updated, and the above steps are repeated until the time ends.

[0082] S3: Based on the simulation results of the multi-cluster hydraulic fracture propagation, the propagation simulation of multi-stage multi-cluster hydraulic fractures in a single well and multi-stage multi-cluster hydraulic fractures in multiple wells is carried out to obtain the morphology, fracture width, induced stress and pressure changes of each stage and cluster of fractures in the whole process of hydraulic fracturing.

[0083] In some embodiments, multi-stage, multi-cluster fracturing is an important application of hydraulic fracturing technology in oil and gas well production enhancement operations. "Multi-stage" refers to fracturing operations performed in multiple stages across different sections of a well, with each stage forming a group of fractures. "Multi-cluster" refers to perforating at multiple locations within the same well section simultaneously or sequentially during each fracturing stage, thereby forming multiple clusters of fractures. This fracturing method can significantly increase the permeability area of ​​oil and gas reservoirs and improve oil and gas flow pathways, making it particularly suitable for the development of low-permeability oil and gas reservoirs. For example, in a horizontal well, the horizontal section can be divided into 5-10 fracturing stages, with 3-5 perforation clusters arranged in each stage for fracturing to increase the well's production.

[0084] It should be noted that for multi-well, multi-stage, and multi-cluster fracturing hydraulic fracture simulation, in addition to considering the interaction between fractures of different stages and clusters within a single well, the mutual influence between multiple wells must also be emphasized. Fractures generated by fracturing in different wells will cause changes in the stress field and seepage field over a larger area, and these changes will affect the propagation of fractures in other wells. By incorporating the fracturing process of each well into a unified simulation framework, comprehensively considering the stress interference and fluid flow coupling between multiple wells, the propagation process of multi-well, multi-stage, and multi-cluster fracturing hydraulic fractures can be simulated. This allows for a comprehensive understanding of the parameter changes of each stage and cluster of fractures in the well group throughout the entire fracturing process, providing detailed and accurate data for fracturing design optimization.

[0085] In this step, when conducting simulations of multi-stage, multi-cluster fracturing fracture propagation in a single well, as well as simulations of hydraulic fracture propagation in multiple wells with multi-stage, multi-cluster fracturing, stress disturbance terms also need to be considered. It includes: intra-segment crack-induced stress term Inter-segment crack induced stress term Inter-well induced stress term Among them are The induced stress interference term is added to the formula (5) for hydraulic fractures to obtain the morphology, fracture width, induced stress and pressure changes of each level and cluster of fractures in the well throughout the fracturing process.

[0086] Step S4: Set the number of 3D wells, the three-dimensional spatial distribution of the horizontal section, the design of each well cluster, the reservoir lithology and geostress, and determine the various fracturing methods for the 3D wells.

[0087] The number of wells in a three-dimensional formation needs to be determined by comprehensively considering factors such as reservoir size, reserve abundance, and development costs. Generally, for reservoirs with abundant reserves and large areas, the number of wells can be appropriately increased to improve production efficiency, but at the same time, excessively close well spacing should be avoided to prevent mutual interference and increased costs. The three-dimensional spatial distribution design of the horizontal sections should be based on the reservoir's geological structure and oil and gas distribution characteristics. For example, in inclined reservoirs, the dip angle and azimuth of the horizontal sections should be reasonably adjusted to better traverse oil and gas enrichment areas.

[0088] Each well cluster design includes determining the cluster spacing and perforation parameters. The selection of cluster spacing should consider the mutual influence of stress interference range and fracture propagation, avoiding excessive interference between fractures due to excessively small cluster spacing, which would affect the fracturing effect; perforation parameters (number of perforations, angle, diameter, etc.) directly affect fracture initiation and propagation, and a reasonable perforation design can improve fracture initiation efficiency and propagation quality.

[0089] By combining reservoir lithology and geostress data, and through theoretical analysis, numerical simulation, and empirical summarization, various fracturing methods for three-dimensional wells are determined. For example, based on the reservoir's brittleness index, appropriate fracturing fluid types and additives are selected; based on the direction of the maximum horizontal principal stress, the fracturing sequence and fracture propagation direction are designed; and by adjusting parameters such as fracturing fluid injection rate and displacement, different fracturing construction schemes are formed, providing diverse options for subsequent optimization.

[0090] Step S5: Using the maximum total fracture area of ​​multiple three-dimensional wells as the objective function, select the target three-dimensional well fracturing method from the various fracturing methods, and form a well group fracturing design optimization strategy.

[0091] In some embodiments, optimization algorithms, such as genetic algorithms and particle swarm optimization algorithms, are used to evaluate and optimize the various fracturing methods determined in step S5. Using the objective function as the evaluation criterion, the objective function value corresponding to each fracturing method is calculated. Through iterative search of the algorithm, the optimal target well fracturing method is gradually selected.

[0092] After determining the optimal fracturing method, it is refined into specific well group fracturing design optimization strategies based on actual engineering conditions and constraints. This includes specific parameter settings for fracturing operations (such as fracturing fluid formulation, injection pressure, and displacement), construction sequence arrangement, and monitoring scheme formulation, forming a complete fracturing design scheme that can guide on-site construction, thereby achieving efficient fracturing of three-dimensional development well groups and effective development of oil and gas resources.

[0093] Thus, this invention provides a method for simulating and optimizing fracturing in a three-dimensional well cluster, overcoming the problems of blind fracturing operations and unclear controlling factors in existing technologies. It provides a scientific basis for optimizing three-dimensional well development schemes under unconventional tight reservoir well factory models. Compared to the usual simulations that only target the propagation of multiple clusters of fractures in a single well segment, considering only the interference between fractures within a single fracturing segment at the same time and in a limited space within the same well segment, the simulation method proposed in this invention builds upon the single-function foundation of previous methods. By constructing algorithms for arbitrary combinations of multiple single-segment, multi-cluster fracturing operations in time and space, it achieves a qualitative upgrade and expansion regardless of the fracturing time sequence or layout space. It fully considers the characteristics of fracturing interference and interaction between multiple wells, upgrading to the simulation of multiple wells, multiple segments, and multiple clusters. Furthermore, by maximizing the total area of ​​all fracturing fractures in all wells as the optimization objective, it provides a solid foundation for optimizing parameters such as well layout, fracturing sequence, fracturing operation parameters, and inter-well cross-flow prevention in large-scale reservoir areas.

[0094] Figure 2 This is a conceptual diagram of three-dimensional well fracturing, such as... Figure 2 As shown, 1-fracking pump truck; 2-well A; 3-well B; 4-well C; 5-well D; 6-reservoir 1; 7-reservoir 2; 8-cluster; 9-section; 10-separator.

[0095] Figure 3 This is the induced stress overlay diagram provided in this embodiment, which shows the induced stress terms of the crack within the segment. Inter-segment crack induced stress term Inter-well induced stress term It demonstrates the superposition of induced stresses on specific units by intra-segment, inter-segment, and inter-well elements.

[0096] Figure 4 This is a multi-cluster fluid flow and pressure balance distribution diagram provided in this embodiment. Figure 4The figure shows the flow distribution and pressure distribution of fluid between the main fracture and the branch fractures in a multi-cluster fracture system, demonstrating the fluid flow and pressure balance mechanism among multiple fractures.

[0097] In this example, such as Figure 5 As shown, taking wells A, B, and C as examples, each well has three clusters, demonstrating sequential fracturing. The arrangement of fracturing cycles for each cluster in each well can be further subdivided into ABC, ACB, BAC, BCA, CAB, and CBA, with the next fracturing cycle proceeding after the previous one is completed.

[0098] In this example, such as Figure 6 The diagram illustrates simultaneous fracturing. In wells A, B, and C, each layer and cluster is fracturing simultaneously, with the next layer being fractured after the previous one is completed.

[0099] In this example, such as Figure 7 As shown, this demonstrates direct fracturing. Wells A, B, and C, and each cluster of wells, are fracturing in a top-to-bottom order. The arrangement of the fracturing cycles for each well can be further subdivided into ABC, ACB, BAC, BCA, CAB, and CBA.

[0100] By combining the above fracturing methods, multiple fracturing schemes are obtained. Using the maximization of the total fracture area in the multi-well fracturing as the objective function, the optimal multi-well fracturing scheme is selected, forming an optimized well group fracturing design process and method.

[0101] Example 2: The present invention also provides a three-dimensional well fracturing multi-fracture inter-well interference simulation device. This device adopts the three-dimensional well fracturing multi-fracture inter-well interference simulation method of Example 1. The device includes:

[0102] The package building module is based on a single-cluster three-dimensional hydraulic fracture propagation fluid-structure interaction mathematical calculation model, and develops a single-cluster hydraulic fracture propagation calculation function package.

[0103] The multi-cluster hydraulic fracture simulation module, based on the single-cluster hydraulic fracture propagation calculation function package, performs synchronous simulation of multiple cluster hydraulic fractures to obtain simulation results of multi-cluster hydraulic fracture propagation.

[0104] The multi-stage multi-cluster fracturing fracture simulation module, based on the multi-cluster hydraulic fracture propagation simulation results, performs propagation simulations of multi-stage multi-cluster fracturing fractures in a single well and multi-well multi-stage multi-cluster fracturing hydraulic fractures, and obtains the morphology, fracture width, induced stress and pressure changes of each stage and cluster of fractures in the whole fracturing process.

[0105] The fracturing method determination module is used to set the number of 3D wells, the three-dimensional spatial distribution of horizontal sections, the design of each well cluster, reservoir lithology and geostress, and to determine various fracturing methods for the 3D wells.

[0106] The fracturing method selection module is used to select the target fracturing method from a variety of different fracturing methods, with the objective function being to maximize the total area of ​​the fracturing fractures in multiple 3D wells, and to form a well group fracturing design optimization strategy.

[0107] It should be noted that the description of the device embodiments of the present invention is similar to the description of the method embodiments described above, and has similar beneficial effects to the same method embodiments; therefore, it will not be repeated. For technical details not disclosed in the device embodiments, please refer to the description of the method embodiments of the present invention for understanding.

[0108] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the technical solutions of the embodiments of the present invention.

Claims

1. A method for modeling interwell interference in a multistage fracturing of a vertical well, the method comprising: The method comprises the following steps: Step S1, based on a single cluster three-dimensional hydraulic fracture propagation fluid-structure coupling mathematical calculation model, a single cluster hydraulic fracture propagation calculation function program package is developed; S2: based on the single cluster hydraulic fracture propagation calculation function program package, multi-cluster hydraulic fracture synchronous simulation is carried out to obtain multi-cluster hydraulic fracture propagation simulation results; in the step S2, the multi-cluster hydraulic fracture propagation simulation results include iterative solution of multi-cluster fracture flow distribution at each time step, solution of multi-fracture propagation induced stress term, and solution of update of state variables of all elements of each fracture; the solution of the multi-fracture propagation induced stress term is calculated as follows: ； where is the number of hydraulic fractures, is the number of other fractures induced stress and acts on the fracture normal stress vector, ; is the fracture on the fracture normal stress; is the number of fractures column vector of the fracture I all element aperture, ; is the fracture fluid pressure at the midpoint of all elements, ; is the fracture I normal stress vector of the earth stress, ; is the number of fractures column vector of the fracture I all element aperture, stress influence coefficient generated by the fracture number of fractures column vector of the fracture I all element aperture, ; S3: based on the multi-cluster hydraulic fracture propagation simulation results, carrying out propagation simulation on single well multi-stage multi-cluster fracturing fracture and multi-well multi-stage multi-cluster hydraulic fracture, to obtain the shape, fracture width, induced stress and pressure change of each cluster fracture of each level of well in the whole fracturing process; in the step S3, in carrying out single well multi-stage multi-cluster fracturing fracture propagation simulation and multi-well multi-stage multi-cluster hydraulic fracture propagation simulation, the stress interference term also needs to be considered , which comprises: intra-segment fracture induced stress term , inter-segment fracture induced stress term , inter-well induced stress term , wherein , the stress interference term is considered in formula (5) and solved, so as to obtain the shape, fracture width, induced stress and pressure change of each cluster fracture of each level of well in the whole fracturing process; Step S4, setting the number of three-dimensional wells, the three-dimensional spatial distribution of horizontal sections, the design of each well cluster, the reservoir lithology and the ground stress, and determining multiple different fracturing modes of the three-dimensional wells; Step S5, taking the maximum total area of the fracturing fractures of the multiple three-dimensional wells as the objective function, selecting the target three-dimensional well fracturing mode from the multiple different fracturing modes, and forming a well group fracturing design optimization strategy.

2. The three-dimensional well fracturing multi-fracture well interference simulation method according to claim 1, wherein, The single-cluster hydraulic fracture propagation calculation function program package is specifically divided into two versions A and B, the output variable of version A is injection point pressure, which is used for iterative solution of each cluster flow ; version B is used for sequentially outputting all cell state variables of fracture propagation under the condition of obtaining the determined cluster flow.

3. The method of claim 2, wherein, All the cell state variables of the crack propagation include crack width , pressure distribution .

4. The method of claim 1, wherein, The iterative solution calculation method of the multi-cluster fracture flow distribution is as follows: Consider the pressure value of the injection point fracture cell closest to the toe of the horizontal well , perforation hole friction , and wellbore along-the-hole friction , and the intra- segment fracture induced stress term , add this induced stress interference term to equation (5); Set the initial time under the gap width, flow and pressure, set the time as T, time step is For all the extended cracks, each time step to determine whether the crack tip peripheral unit outward expansion; pressure at the near heel end of a certain fracturing section of a horizontal well pressure value of the fracture cell nearest to the injection point at the heel end of the horizontal well friction of the perforation hole and the friction along the wellbore satisfies: ； wherein , are functions of , are solved by solving for are expressed as: ； wherein represents fluid density, ; represents the number of single cluster shot holes, represents hole diameter, m; represents dimensionless throttling coefficient, between 0.5~0.9; represents fluid wellbore length, m; is the along-the-way resistance coefficient; In the A version of the single-cluster hydraulic fracture propagation calculation function program package, the formula (5) after adding the induced stress interference term is written in the form of equation , and is taken as part of the pressure balance equation, with the flow rate of each perforation cluster pumped as the unknown of the pressure balance equation, and is solved by iteration through the Newton-Raphson formula, so as to obtain the flow rate distribution of each cluster hydraulic fracture; on this basis, the B version of the single-cluster hydraulic fracture propagation calculation function program package is called to sequentially output all the unit state variables of the fracture propagation. Then, loop to the next time step, judge whether the hydraulic fracture reaches the peripheral fracture element expansion condition, update the stress influence coefficient, and repeat the above steps until the time ends; Then, loop to the next time step, judge whether the hydraulic fracture reaches the peripheral fracture element expansion condition, update the stress influence coefficient based on the updated fracture element, and repeat the above steps until the time ends.

5. The method of claim 4, wherein: The peripheral fracture element expansion judgment method uses implicit level set or damage element method to judge whether the fracture tip element is open.

6. An apparatus for modeling interwell interference in a multistage fracturing of a vertical well, the apparatus comprising: The device adopts the three-dimensional well fracturing multi-fracture well interference simulation method of any one of claims 1-5, and the device comprises: A program package building module, which develops a single cluster hydraulic fracture propagation calculation function program package based on a single cluster three-dimensional hydraulic fracture propagation fluid-structure coupling mathematical calculation model; A multi-cluster hydraulic fracture simulation module, which carries out multi-cluster hydraulic fracture synchronous simulation based on the single cluster hydraulic fracture propagation calculation function program package to obtain multi-cluster hydraulic fracture propagation simulation results; A multi-stage multi-cluster fracturing fracture simulation module, which carries out expansion simulation on single-well multi-stage multi-cluster fracturing fractures and multi-well multi-stage multi-cluster fracturing hydraulic fractures based on the multi-cluster hydraulic fracture propagation simulation results to obtain the shape, fracture width, induced stress and pressure change of each cluster fracture at each stage of the well during the whole fracturing process; A fracturing mode determination module, which is used for setting the number of three-dimensional wells, the three-dimensional spatial distribution of horizontal sections, the design of each well cluster, the reservoir lithology and the ground stress, and determining multiple different fracturing modes of the three-dimensional wells; A fracturing mode selection module, which is used for taking the maximum total area of the fracturing fractures of the multiple three-dimensional wells as the objective function, selecting the target three-dimensional well fracturing mode from the multiple different fracturing modes, and forming a well group fracturing design optimization strategy.

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