Multi-fracture inter-well interference simulation method and device for three-dimensional well fracturing

Abstract

The invention relates to the field of petroleum three-dimensional well fracturing, in particular to a three-dimensional well fracturing multi-fracture optimization method and device.According to the method, firstly, a single-cluster hydraulic fracture propagation calculation function program package is developed, and then multi-cluster hydraulic fracture synchronous simulation is carried out; then, single-well multi-stage and multi-cluster fracturing fractures and multi-well multi-stage and multi-cluster fracturing hydraulic fractures are subjected to extension simulation, then the number of three-dimensional wells, horizontal section three-dimensional space distribution, well cluster design, reservoir lithology and ground stress are set, and multiple different fracturing modes of the three-dimensional wells are determined; and finally selecting a target three-dimensional well fracturing mode from the multiple different fracturing modes by taking the maximum total area of fracturing cracks of the multiple three-dimensional wells as a target function, and forming a well group fracturing design optimization strategy. According to the method, qualitative upgrading and expansion in any sequence and any layout space of the fracturing time are realized, and the fracturing fracture interference interaction characteristics among multiple wells can be fully considered.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of three-dimensional well fracturing, and particularly to a three-dimensional well fracturing multi-fracture optimization method and device. BACKGROUND

[0002] The shale oil technology in China has a recoverable resource of 5.5 billion tons, which is gradually becoming a key force for oil and gas production in China. The unconventional oil and gas reservoir has very high tightness, and it is necessary to use reservoir reconstruction methods such as hydraulic fracturing to build a large area and complex fracture network in the tight oil and gas reservoir, so as to connect the underground tight reservoir and make the oil and gas seep from the reservoir through the artificial fracture to the wellbore, and then develop an industrial oil and gas flow. In the development process of unconventional oil and gas reservoir, long horizontal well section combined with "dense cutting" volume fracture network fracturing has become the main way of unconventional reservoir reconstruction. The well factory mode of multiple horizontal wells is used for comprehensive fracturing to realize three-dimensional development, and well group fracturing has gradually become the core technology of shale oil reservoir reconstruction.

[0003] However, compared with single well fracturing, the interwell interfracture interference process of well group fracturing is more complex. In the three-dimensional well fracturing operation, not only is there strong interference between the hydraulic fractures of each level and each section of the interwell, but also the existing hydraulic fractures of the other three-dimensional well group have serious interference on the hydraulic fractures that are currently being fractured and expanded. In the process of three-dimensional well cooperative fracturing, both in the time dimension and the space dimension, complex interference characteristics are presented.

[0004] The three-dimensional well fracturing effect is affected by multiple factors, including reservoir mechanical properties, stratified stress characteristics, three-dimensional well number, spatial position distribution, segment cluster distribution, fracturing construction parameters, and three-dimensional well fracturing mode sequence. At present, there is a problem of blindness and unclear main control factors in fracturing construction, and the three-dimensional well group fracturing process and construction method need to be optimized. SUMMARY

[0005] In order to solve the above technical problems, the present application provides a three-dimensional well fracturing multi-fracture interwell interference simulation method and device for solving the problems in the prior art.

[0006] According to one aspect of the present application, a three-dimensional well fracturing multi-fracture interwell interference simulation method is provided, comprising the following steps:

[0007] Step S1, based on a single cluster three-dimensional hydraulic fracture expansion fluid-solid coupling mathematical calculation model, a single cluster hydraulic fracture expansion calculation function program package is developed;

[0008] S2: based on the single cluster hydraulic fracture expansion calculation function program package, multi-cluster hydraulic fracture synchronous simulation is carried out to obtain multi-cluster hydraulic fracture expansion simulation results;

[0009] S3: based on the multi-cluster hydraulic fracture propagation simulation results, the single well multi-stage multi-cluster fracturing fracture and multi-well multi-stage multi-cluster hydraulic fracture are simulated to obtain the shape, fracture width, induced stress and pressure change of each cluster fracture of each level of the well in the whole fracturing process;

[0010] Step S4, setting the number of three-dimensional wells, horizontal segment three-dimensional space distribution, each well cluster design, reservoir lithology and ground stress, and determining the multiple different fracturing modes of the three-dimensional well;

[0011] Step S5, taking the maximum total area of the multi-well fracturing fracture as the objective function, selecting the target three-dimensional well fracturing mode from the multiple different fracturing modes, and forming the well group fracturing design optimization strategy.

[0012] Preferably, the single-cluster hydraulic fracture propagation calculation function program package is specifically divided into A and B two versions, the A version output variable is the injection point pressure, which is used for iterative solution of each cluster flow Q i =[Q1,Q2,...,Q n ]; the B version is used for sequentially outputting all unit state variables of the fracture propagation under the condition of obtaining the determined cluster flow.

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

[0014] Preferably, 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 update solution of all unit state variables of each fracture.

[0015] Preferably, the solution calculation method of the multi-fracture propagation induced stress term is as follows:

[0016]

[0017] Wherein I, J represent the number of hydraulic fractures, represents the induced stress caused by other fractures (J≠I) and acting on the normal stress vector of fracture I, Pa; H IJ is the influence of fracture J (J≠I) on the normal stress of fracture I; W J represents a column vector composed of all unit fracture widths of the Jth fracture, m; P I represents the fluid pressure at the midpoint of all units of fracture I, Pa; represents the ground stress acting on the normal stress vector of fracture I, Pa; A II represents the stress influence coefficient generated by the opening degree of all units of the Ith fracture on each unit of fracture I; W Im represents a column vector composed of all the unit fracture widths of the first fracture, m.

[0018] Preferably, the iterative solution calculation method of the multi-cluster fracture flow distribution is as follows:

[0019] The pressure value p of the fracture unit closest to the injection point of the heel end of the horizontal well is considered w,fi , the perforation hole friction p pf,fi , and the wellbore friction p cf,fi , and the fracture-induced stress term within the segment The induced stress interference term is added to the elastic equation of the hydraulic fracture;

[0020] The fracture width, flow rate, and pressure at the initial time are set, the time is T, the time step is ΔT, and for all the expanded fractures, it is determined whether the peripheral unit of the fracture tip expands outward at each time step.

[0021] The pressure p of the heel end of the horizontal well in a certain fracturing segment o and the pressure value p of the fracture unit closest to the injection point of the heel end of the horizontal well w,fi , the perforation hole friction p pf,fi , and the wellbore friction 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 , and p cf,fi are functions of Q i . p w,fi is solved by solving P I in equation (5), and p pf,fi , p cf,fi are respectively represented as:

[0024]

[0025]

[0026] where ρ s represents the fluid density, kg / m 3 ; n p,fi represents the number of single-cluster perforation holes, d p,fi represents the hole diameter, m; K d represents the dimensionless throttling coefficient, between 0.5 and 0.9; L represents the fluid wellbore length, m; and λ is the friction coefficient (dimensionless);

[0027] In the A version of the single-cluster hydraulic fracture propagation calculation function program package, formula (5) is written in the form of equation P w,fi = f(Q i ) and is taken as a part of the pressure balance equation, with the pumped injection cluster flow rate Q i = [Q1, Q2,..., Q n ] as the pressure balance equation unknowns, which are solved by the Newton-Raphson formula iteration to obtain the hydraulic fracture inflow flow rate distribution of each cluster; 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;

[0028] Then the loop is cycled to the next time step, the hydraulic fracture is judged to reach the peripheral fracture unit propagation condition, the stress influence coefficient is updated, and the above steps are repeated until the time ends.

[0029] Then the loop is cycled to the next time step, the hydraulic fracture is judged to reach the peripheral fracture unit propagation condition, the stress influence coefficient is updated on the basis of the updated fracture unit, and the above steps are repeated until the time ends.

[0030] 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.

[0031] Preferably, the peripheral fracture unit propagation judgment method adopts an implicit level set or a damage unit method to judge whether the fracture tip unit is open.

[0032] Preferably, in the step S3, in the single-well multi-stage multi-cluster fracture propagation simulation and the multi-well multi-stage multi-cluster hydraulic fracture propagation simulation, the stress interference term which includes: a fracture-induced stress term within a section a fracture-induced stress term between sections an inter-well induced stress term wherein The stress interference term is considered in formula (5) and is solved, so as to obtain the shape, fracture width, induced stress and pressure change of each cluster fracture of each stage of the well in the whole fracturing process.

[0033] According to another aspect of the present application, a three-dimensional well fracturing multi-fracture inter-well interference simulation device is provided, which adopts the three-dimensional well fracturing multi-fracture inter-well interference simulation method described above, and the device comprises:

[0034] A program package construction module develops a single-cluster hydraulic fracture propagation calculation function program package based on a single-cluster three-dimensional hydraulic fracture propagation fluid-solid coupling mathematical calculation model;

[0035] A multi-cluster hydraulic fracture simulation module, based on the single-cluster hydraulic fracture propagation calculation function package, carries out synchronous simulation of multi-cluster hydraulic fractures, and obtains multi-cluster hydraulic fracture propagation simulation results;

[0036] A multi-stage multi-cluster fracturing fracture simulation module, based on the multi-cluster hydraulic fracture propagation simulation results, carries out propagation simulation of single-well multi-stage multi-cluster fracturing fractures and multi-well multi-stage multi-cluster hydraulic fractures, and obtains the shape, fracture width, induced stress and pressure change of each cluster fracture of each stage of the well in the whole fracturing process;

[0037] A fracturing mode determination module is used to set 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 determine the multiple different fracturing modes of the three-dimensional wells.

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

[0039] The present application provides a three-dimensional well group fracturing simulation and optimization method, which first develops a single-cluster hydraulic fracture propagation calculation function package based on a single-cluster three-dimensional hydraulic fracture propagation fluid-solid coupling mathematical calculation model, then carries out synchronous simulation of multi-cluster hydraulic fractures based on the single-cluster hydraulic fracture propagation calculation function package, obtains multi-cluster hydraulic fracture propagation simulation results, then carries out propagation simulation of single-well multi-stage multi-cluster fracturing fractures and multi-well multi-stage multi-cluster hydraulic fractures based on the multi-cluster hydraulic fracture propagation simulation results, and obtains the shape, fracture width, induced stress and pressure change of each cluster fracture of each stage of the well in the whole fracturing process; then set 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 determine the multiple different fracturing modes of the three-dimensional wells, and finally take the maximum total area of the fracturing fractures of the multiple three-dimensional wells as the objective function, select the target three-dimensional well fracturing mode from the multiple different fracturing modes, and form a well group fracturing design optimization strategy; The present application overcomes the problems of large blindness and unclear main control factors in the prior art, and provides a scientific basis for the optimization of three-dimensional well development schemes in the unconventional tight reservoir well yard mode. Compared with the usual single-well single-stage multi-cluster fracture propagation simulation, which only considers the fracture interference in the same time and close distance local space within a single fracturing section, the simulation method proposed by the present application is based on the single function of the original simulation method, and realizes the qualitative upgrading and expansion in the fracturing time sequence and arbitrary layout space through the algorithm construction of the arbitrary combination of multiple single-stage multi-clusters in time and space, can fully consider the fracturing fracture interference interaction characteristics between multiple wells, and upgrades to multi-well multi-stage multi-cluster simulation, and then can maximize the total area of all fracturing fractures of all wells as the optimization target, and further provides a solid foundation for the optimization of three-dimensional well spacing, fracturing sequence, fracturing construction parameters, interwell channeling prevention and other parameters in a large range of reservoir regions. BRIEF DESCRIPTION OF DRAWINGS

[0040] In order to more clearly illustrate the technical solutions in the specific embodiments or prior art of the present application, the drawings required to be used in the description of the specific embodiments or prior art will be briefly introduced. Obviously, the drawings described below are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0041] Figure 1 is a flowchart of a three-dimensional well fracturing multi-fracture well interference simulation method provided by an embodiment of the present application;

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

[0043] Figure 3 is an induced stress superposition diagram provided by an embodiment of the present application;

[0044] Figure 4 is a multi-cluster fluid flow pressure balance distribution diagram provided by an embodiment of the present application;

[0045] Figure 5 is a sequential fracturing schematic diagram provided by an embodiment of the present application;

[0046] Figure 6 is a synchronous fracturing schematic diagram provided by an embodiment of the present application;

[0047] Figure 7 is a straight fracturing schematic diagram provided by an embodiment of the present application. DETAILED DESCRIPTION

[0048] In order to make the objects, technical solutions and advantages of the present application clearer, the technical solutions of the present application will be described clearly and completely. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0049] Referring to Figure 1 , Figure 1 is a flowchart of a three-dimensional well fracturing multi-fracture well interference simulation method provided by an embodiment of the present application, which will be described with reference to the steps shown in Figure 1 . As shown in Figure 1 , a three-dimensional well fracturing multi-fracture well interference simulation method comprises the following steps:

[0050] 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.

[0051] In some embodiments, hydraulic fracture propagation refers to the process during hydraulic fracturing, whereby high-pressure fluid (fracturing fluid) is injected into the formation, causing the formation rock to fracture and form cracks, with the cracks then continuously extending and expanding under the action of pressure. This process is influenced by a variety of factors, such as the distribution of in-situ stresses (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, displacement, injection rate, etc.), and perforation parameters.

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

[0053]

[0054] Where q is the flow velocity of the fracturing fluid in the fracture, p is the fluid pressure, w is the crack width in each crack unit, and μ is the viscosity of the fracturing fluid; is the gradient operator along the path within the crack;

[0055] The mass balance equation of the incompressible fracturing fluid flowing in the hydraulic fracture can be expressed as:

[0056]

[0057] Where t is time, Q I is the fracturing fluid inflow term, δ is the Dirac delta function representing the point source;

[0058] Considering the balance of fracturing fluid flow (flux) flowing into and out of each crack unit volume, the finite volume method can be used to 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 are the crack width of the current time unit and the crack width of the previous time unit, respectively, Δt is the time unit step, and B is the coefficient of the fluid lubrication equation;

[0061] Based on this, a single-cluster three-dimensional hydraulic fracture expansion fluid-solid coupling mathematical calculation model is constructed. The above functional relationship is programmed and implemented and encapsulated into a single-cluster hydraulic fracture expansion calculation function package. This package can be used as an independent module to facilitate subsequent multi-fracture simulation calls.

[0062] It is worth emphasizing that the program package is specifically divided into two versions A and B, the output variable of version A is injection point pressure, which is used to calculate the cluster flow rate Q i = [Q1, Q2,..., Q n ] iterative solution; version B is used to sequentially output all unit state variables of fracture propagation, including fracture width W I , pressure distribution P I , etc. under the condition of obtaining the cluster flow rate.

[0063] S2: based on the single-cluster hydraulic fracture propagation calculation function program package, carrying out multi-cluster hydraulic fracture synchronous simulation to obtain multi-cluster hydraulic fracture propagation simulation results;

[0064] Wherein, the multi-cluster hydraulic fracture propagation simulation results include iterative solution of multi-cluster fracture flow rate distribution at each time step, solution of multi-fracture propagation induced stress term, and update solution of all unit state variables of each fracture;

[0065] Wherein, the all unit state variables of each fracture include fracture width and pressure;

[0066] Wherein, the solution calculation method of multi-fracture propagation induced stress term is as follows:

[0067]

[0068]

[0069] Wherein, I and J represent the number of hydraulic fractures, represents the induced stress caused by other fractures (J≠I) and acting on the normal stress vector of fracture I, Pa; H IJ is the influence of fracture J (J≠I) on the normal stress of fracture I; W J represents the column vector of all unit fracture widths of the Jth fracture, m; P I represents the fluid pressure at the midpoint of all units of fracture I, Pa; represents the normal stress vector of fracture I acted by the ground stress, Pa; A II represents the stress influence coefficient generated by the opening degree of all units of the Ith fracture on each unit of fracture I; W I represents the column vector of all unit fracture widths of the Ith fracture, m.

[0070] Further, the iterative solution calculation method of multi-cluster fracture flow rate distribution is as follows:

[0071] Considering the pressure value p w,fi of the injection point fracture unit closest to the heel end of the horizontal well, the perforation hole friction p pf,fi and the wellbore friction p cf,fiand the induced stress term in the segment The induced stress interference term is added to the elastic equation of hydraulic fracture;

[0072] Set the initial time of the fracture width, flow and pressure, set the time T, time step ΔT, for all the expanding fracture, each time step to determine whether the crack tip peripheral unit outward expansion;

[0073] The pressure p of the near heel of the horizontal well fracture section o The pressure value p of the injection point fracture unit closest to the heel of the horizontal well w,fi , perforation hole friction p pf,fi And the wellbore friction 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 are functions of Q i . p w,fi Solve P I in equation (5), p pf,fi , p cf,fi are expressed as:

[0076]

[0077] Where ρ s represents the fluid density, kg / m 3 ; n p,fi represents the number of single cluster perforation hole, d p,fi represents the hole diameter, m; K d represents the dimensionless throttling coefficient, between 0.5-0.9; L represents the fluid wellbore length, m; λ is the along the way resistance coefficient (dimensionless);

[0078] In the A version of the single cluster hydraulic fracture expansion calculation function package, equation (5) is written as the form of equation P w,fi =f(Q i ) and as part of the pressure balance equation, with each perforation cluster flow Q i =[Q1,Q2,...,Q nAs the unknown of the pressure balance equation, the Newton-Raphson formula is used for iterative solution, so as to obtain the inflow distribution of each cluster of hydraulic fractures; 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, including the fracture width W I , the pressure distribution P I , etc.

[0079] Then, the process is looped to the next time step, it is judged whether the hydraulic fracture reaches the peripheral fracture element expansion condition, the stress influence coefficient is updated, and the above steps are repeated until the time ends.

[0080] Among them, the implicit level set or damage element method is used to judge whether the crack tip element is open.

[0081] Then, the process is looped to the next time step, it is judged whether the hydraulic fracture reaches the peripheral fracture element expansion condition, the stress influence coefficient is updated, and the above steps are repeated until the time ends.

[0082] S3: Based on the multi-cluster hydraulic fracture propagation simulation result, the single-well multi-stage multi-cluster fracturing fracture and the multi-well multi-stage multi-cluster hydraulic fracture are simulated to obtain the shape, fracture width, induced stress and pressure change of each cluster of fractures at each stage of the well in the whole fracturing process.

[0083] In some embodiments, multi-stage multi-cluster fracturing is an important application mode of hydraulic fracturing technology in oil and gas well stimulation. "Multi-stage" means that fracturing is carried out in multiple stages in different well sections of a well, and each stage forms a group of fractures; "multi-cluster" means that in each fracturing stage, perforation is carried out simultaneously or sequentially at multiple positions in the same well section, thereby forming multiple groups of fracture clusters. This fracturing method can greatly increase the seepage area of the oil and gas reservoir and improve the oil and gas flow channel, and is 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 sections, and each fracturing section is arranged with 3-5 perforation clusters for fracturing to improve the production of the oil and gas well.

[0084] It should be noted that for multi-well multi-stage multi-cluster hydraulic fracture simulation, in addition to considering the interaction of fractures at each stage and each cluster in a single well, the mutual influence between multiple wells is also focused on. The fractures generated by fracturing in different wells will cause changes in the stress field and seepage field in a larger range, which will affect the expansion of fractures in other wells. By incorporating the fracturing process of each well into a unified simulation framework, the stress interference and fluid flow coupling between multiple wells are comprehensively considered, the expansion process of multi-well multi-stage multi-cluster hydraulic fractures is simulated, and the changes of various parameters of each stage and each cluster of fractures in the well group in the whole fracturing process are comprehensively mastered, thereby providing detailed and accurate data for fracturing design optimization.

[0085] In this step, the single well multi-stage multi-cluster fracture propagation simulation and the multi-well multi-stage multi-cluster hydraulic fracture propagation simulation are carried out, and the stress interference term also needs to be considered It includes: intra-segment fracture-induced stress term Inter-segment fracture-induced stress term Inter-well induced stress term Among them Add the induced stress interference term to the formula (5) of the hydraulic fracture, so as to obtain the shape, fracture width, induced stress and pressure change of each cluster fracture of each stage of the well in the whole fracturing process.

[0086] Step S4, setting the number of three-dimensional wells, horizontal segment three-dimensional space distribution, each well cluster design, reservoir lithology and ground stress, and determining the multiple different fracturing modes of the three-dimensional well.

[0087] The setting of the number of three-dimensional wells needs to comprehensively consider the factors such as the scale of the oil and gas reservoir, the reserve abundance, and the development cost. Generally speaking, for the oil and gas reservoir with rich reserves and large area, the number of wells can be appropriately increased to improve the mining efficiency, but at the same time, the mutual interference and cost increase caused by the dense well spacing should be avoided. The design of the horizontal segment three-dimensional space distribution should be based on the geological structure and oil and gas distribution characteristics of the reservoir, for example, in the inclined reservoir, the inclination angle and the position of the horizontal segment are reasonably adjusted to make it better pass through the oil and gas enrichment area.

[0088] The design of each well cluster includes determining the cluster spacing, perforation parameters, etc. The selection of the cluster spacing needs to consider the stress interference range and the mutual influence of fracture propagation, so as to avoid the excessive mutual interference of fractures caused by too small cluster spacing, which affects the fracturing effect; the perforation parameters (perforation number, angle, diameter, etc.) directly affect the initiation and propagation of the fracture, and reasonable perforation design can improve the opening efficiency and propagation quality of the fracture.

[0089] Combined with the reservoir lithology and ground stress data, through theoretical analysis, numerical simulation and experience summary, multiple different three-dimensional well fracturing modes are determined. For example, according to the brittleness index of the reservoir, the appropriate fracturing fluid type and additive are selected; according to the direction of the maximum horizontal principal stress, the fracturing sequence and the fracture propagation direction are designed; by adjusting the parameters such as the fracturing fluid injection rate and displacement, different fracturing construction schemes are formed to provide diversified choices for subsequent optimization.

[0090] Step S5, taking the maximum total area of the multi-well fracturing fractures as the objective function, selecting the target three-dimensional well fracturing mode from the multiple different fracturing modes, and forming the well group fracturing design optimization strategy.

[0091] In some embodiments, an optimization algorithm such as a genetic algorithm, a particle swarm optimization algorithm, etc. is used to evaluate and optimize the multiple fracturing modes determined in step S5. The objective function is used as the evaluation standard, and the objective function value corresponding to each fracturing mode is calculated. Through iterative search of the algorithm, the optimal target three-dimensional well fracturing mode is gradually screened out.

[0092] After the optimal fracturing mode is determined, the actual engineering conditions and constraints are combined to refine the specific well group fracturing design optimization strategy, including specific parameter settings of fracturing construction (such as fracturing fluid formula, injection pressure, displacement, etc.), construction sequence arrangement, monitoring scheme development, etc. to form a complete fracturing design scheme that can guide the field construction, and realize efficient fracturing of three-dimensional development well groups and effective development of oil and gas resources.

[0093] Thus, the present application provides a three-dimensional well group fracturing simulation and optimization method, which overcomes the problems of blindness in fracturing construction, unclear main control factors, etc. in the prior art, and provides a scientific basis for three-dimensional well development scheme optimization under the unconventional tight reservoir well yard mode. Compared with the conventional single-well single-stage multi-cluster fracture expansion simulation, only the fracture interference in the same time and close distance local space within a single fracturing stage is considered. The simulation method proposed in the present application is based on the single function of the original simulation method, and is constructed by an algorithm for any combination of multiple single-stage multi-clusters in time and space, realizes qualitative upgrading and expansion in any sequence of fracturing time and any layout space, can fully consider the fracture interference interaction characteristics between multiple wells, upgrades to multi-well multi-stage multi-cluster simulation, and can further provide a solid foundation for three-dimensional well pattern, fracturing sequence, fracturing construction parameter, and interwell channeling prevention parameter optimization in a large range of reservoir regions by taking the maximization of the total area of all fracturing fractures of all wells as the optimization target.

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

[0095] Figure 3 is an induced stress superposition diagram provided by the present embodiment, which shows the intra-stage fracture induced stress term inter-stage fracture induced stress term inter-well induced stress term demonstrates the intra-stage, inter-stage, and inter-well unit superimposed induced stress on a specific unit.

[0096] Figure 4 is a multi-cluster fluid flow pressure balance distribution diagram provided by the present embodiment, Figure 4The fluid flow distribution and pressure distribution between the main fracture and the branch fracture in the multi-cluster fracture system are shown, and the fluid flow and pressure balance mechanism between the fractures is embodied.

[0097] In this example, as shown in FIG. 1, wells A, B and C are taken as examples. Each well has three clusters, and sequential fracturing is shown. The arrangement combination of the fracturing sequence of each cluster of each well can be subdivided into ABC, ACB, BAC, BCA, CAB and CBA, and the fracturing of the next layer is performed after the fracturing of the previous layer is completed. Figure 5

[0098] In this example, as shown in FIG. 2, synchronous fracturing is shown. The fracturing of each cluster of each layer in wells A, B and C is performed simultaneously, and the fracturing of the next layer is performed after the fracturing of the previous layer is completed. Figure 6

[0099] In this example, as shown in FIG. 3, straight fracturing is shown. The fracturing of each cluster of each well in wells A, B and C is performed in the order from top to bottom, and the arrangement combination of the fracturing sequence of each well can be subdivided into ABC, ACB, BAC, BCA, CAB and CBA. Figure 7

[0100] Through the combination of the above-mentioned fracturing modes, a plurality of fracturing schemes are obtained. Taking the maximum total area of the fracturing cracks of the vertical well fracturing as the objective function, the best vertical well fracturing scheme is optimized, and the optimized well group fracturing design process and method are formed.

[0101] In embodiment 2, the application further provides a device for simulating the interference between multi-fracture wells in vertical well fracturing, which adopts the method for simulating the interference between multi-fracture wells in vertical well fracturing in embodiment 1. The device comprises:

[0102] A program package construction module, which develops a single-cluster hydraulic fracture expansion calculation function program package based on a single-cluster three-dimensional fluid-solid coupling mathematical calculation model of hydraulic fracture expansion;

[0103] A multi-cluster hydraulic fracture simulation module, which carries out synchronous simulation of multi-cluster hydraulic fractures based on the single-cluster hydraulic fracture expansion calculation function program package, and obtains multi-cluster hydraulic fracture expansion simulation results;

[0104] A multi-stage multi-cluster fracturing fracture simulation module, which carries out expansion simulation of 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 expansion simulation results, and obtains the shape, fracture width, induced stress and pressure change of each cluster of each level of the well in the whole fracturing process;

[0105] A fracturing mode determination module, which is used for setting the number of vertical wells, the three-dimensional spatial distribution of horizontal sections, the cluster design of each well, the reservoir lithology and the ground stress, and determining a plurality of different fracturing modes of the vertical wells.

[0106] ​​​The fracturing mode selection module is used for selecting a target fracturing mode of the multi-well fracturing from the multiple different fracturing modes and forming a well group fracturing design optimization strategy with the maximum total area of the multi-well fracturing cracks as a target function.

[0107] It should be noted that the description of the device embodiments of the present application is similar to the description of the above method embodiments, and has similar beneficial effects as the method embodiments, and thus is not described in detail. For technical details not disclosed in the device embodiments, please refer to the description of the method embodiments of the present application for understanding.

[0108] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the technical solutions of the embodiments of the present application.

Claims

1. A method for simulating the interference between wells in a three-dimensional well fracturing process with multiple fractures, characterized in that: The following steps are involved: Step S1, developing a single-cluster hydraulic fracture expansion calculation function package based on a single-cluster three-dimensional hydraulic fracture expansion fluid-solid coupling mathematical calculation model; S2: Based on the single-cluster hydraulic fracture propagation calculation function package, a multi-cluster hydraulic fracture synchronous simulation is performed to obtain a multi-cluster hydraulic fracture propagation simulation result; S3: Based on the multi-cluster hydraulic fracture propagation simulation results, a single-well multi-stage multi-cluster hydraulic fracture propagation simulation is performed for each well and a multi-well multi-stage multi-cluster hydraulic fracture propagation simulation is performed for each well to obtain the morphology, fracture width, induced stress, and pressure changes of each well and each cluster during the entire fracturing process; Step S4, setting the number of stereoscopic wells, the three-dimensional spatial distribution of horizontal sections, the design of each well cluster, reservoir lithology and ground stress, and determining multiple different fracturing methods for the stereoscopic wells; Step S5 , taking the maximum total area of ​​the fracturing cracks in the multiple three-dimensional wells as the objective function, selecting a target three-dimensional well fracturing method from the multiple different fracturing methods, and forming a well group fracturing design optimization strategy.

2. The method for simulating the interference between wells in a three-dimensional well fracturing with multiple fractures according to claim 1, characterized in that: The single cluster hydraulic fracture expansion calculation function package is specifically divided into two versions, A and B. The output variable of version A is the injection point pressure, and the injection point pressure is used to calculate the flow rate Q of each cluster. i =[Q1,Q2,...,Q n ] is an iterative solution; version B is used to sequentially output all unit state variables of crack extension when the flow rate of each cluster is determined.

3. The method for simulating the interference between wells in a three-dimensional well fracturing with multiple fractures according to claim 2, characterized in that: All unit state variables of the crack extension include the crack width W I , pressure distribution P I .

4. The method for simulating the interference between wells in a three-dimensional well fracturing with multiple fractures according to claim 2, characterized in that: In step S2, the simulation results of the multi-cluster hydraulic fracture expansion include iterative solution of multi-cluster fracture flow distribution at each time step, solution of multi-cluster fracture expansion induced stress terms, and update solution of all unit state variables of each fracture.

5. The method for simulating the interference between wells in a three-dimensional well fracturing with multiple fractures according to claim 4, characterized in that: The calculation method for solving the stress term induced by multiple crack extension is as follows: Where I and J represent the numbers of hydraulic fractures. represents the induced stress caused by other cracks (J≠I) and acting on the normal stress vector of crack I, Pa; H IJ is the effect of crack J (J≠I) on the normal stress of crack I; W J represents the column vector consisting of all unit crack widths of the Jth crack, m; P I represents the fluid pressure at the midpoint of all elements in fracture I, Pa; Indicates the normal stress vector of the ground stress acting on the crack I, Pa; A II W represents the stress influence coefficient of each unit on the crack I caused by the opening of all units of the crack I; I Represents the column vector composed of all unit crack widths of the I-th crack, m.

6. The method for simulating the interference between wells in a three-dimensional well fracturing with multiple fractures according to claim 5, characterized in that: The iterative solution calculation method for multi-cluster fracture flow distribution is as follows: Consider the pressure value p of the fracture unit at the injection point closest to the end of the horizontal well. w,fi , perforation hole friction resistance p pf,fi And the friction resistance along the wellbore p cf,fi and the intra-segment crack-induced stress term Add the induced stress interference term into formula (5); Set the crack width, flow rate, and pressure at the initial time, set the time as T, and the time step as ΔT. For all the propagating cracks, determine whether the peripheral units at the crack tip expand outward at each time step. The pressure p near the end of a fracture section in a horizontal well o The pressure value p of the fracture unit at the injection point closest to the end of the horizontal well w,fi , perforation hole friction resistance p pf,fi And the friction resistance along the wellbore p cf,fi satisfy: p o =p w,fi +p pf,fi +p cf,fi (6) where p w,fi 、p pf,fi 、p cf,fi It's all about Q i The function of p w,fi By solving the P in formula (5) I Find, p pf,fi , p cf,fi Respectively expressed as: where ρ s Indicates fluid density, kg / m 3 ;n p,fi represents the number of perforations in a single cluster, d p,fi Indicates the hole diameter, m; K d It represents the dimensionless throttling coefficient, which is between 0.5 and 0.9; L represents the length of the fluid wellbore, m; λ is the resistance coefficient along the path; In version A of the single-cluster hydraulic fracture propagation calculation function package, the formula (5) after adding the induced stress interference term is written as equation P w,fi =f(Q i ) and as part of the pressure balance equation, the pumped flow rate per perforation cluster Q i =[Q1,Q2,...,Q n ] is used as the unknown number in the pressure balance equation and solved iteratively through the Newton-Raphson formula to obtain the distribution of the inflow flow rate of each cluster of hydraulic fractures; on this basis, the B version of the single cluster hydraulic fracture expansion calculation function package is called to output all the unit state variables of the fracture expansion in sequence; Then loop to the next time step, determine whether the hydraulic fracture reaches the peripheral fracture unit expansion condition, update the stress influence coefficient, and repeat the above steps until the time ends; Then loop to the next time step to determine whether the hydraulic fracture reaches the expansion condition of the peripheral fracture unit. On the basis of updating the fracture unit, update the stress influence coefficient and repeat the above steps until the time ends.

7. The method for simulating well interference between multiple fractures in a three-dimensional well fracturing according to claim 6, characterized in that: The peripheral crack unit expansion judgment method uses implicit level set or damage element method to determine whether the crack tip unit is open.

8. The method for simulating the interference between wells in a three-dimensional well fracturing with multiple fractures according to claim 6, characterized in that: In step S3, when carrying out the single-well multi-stage multi-cluster hydraulic fracture propagation simulation and the multi-well multi-stage multi-cluster hydraulic fracture propagation simulation, the stress interference term needs to be considered. It includes: intra-segment crack induced stress term Intersegment crack-induced stress term Interwell induced stress term Among them are The interference term of the surplus stress is considered and solved in formula (5), thereby obtaining the morphology, width, induced stress and pressure changes of each cluster of fractures at each level in the well during the whole fracturing process.

9. A device for simulating the interference between wells in a three-dimensional well fracturing process with multiple fractures, characterized in that: The device adopts the method for simulating the interference between wells of multiple fractures in a three-dimensional well fracturing according to any one of claims 1 to 8, and the device comprises: The program package building module is used to develop a single-cluster hydraulic fracture expansion calculation function package based on the fluid-solid coupling mathematical calculation model of single-cluster three-dimensional hydraulic fracture expansion; A multi-cluster hydraulic fracture simulation module, based on the single-cluster hydraulic fracture expansion calculation function package, performs a synchronous simulation of multiple hydraulic fractures to obtain simulation results of multiple hydraulic fracture expansion; A multi-stage and multi-cluster hydraulic fracture simulation module, based on the multi-cluster hydraulic fracture expansion simulation results, simulates the expansion of multi-stage and multi-cluster hydraulic fractures in a single well and multi-well multi-stage and multi-cluster hydraulic fractures, and obtains the morphology, fracture width, induced stress, and pressure changes of each stage and cluster of fractures in the well during the entire fracturing process; The fracturing method determination module is used to set the number of stereo wells, the three-dimensional spatial distribution of horizontal sections, the design of each well cluster, reservoir lithology and ground stress, and determine various different fracturing methods for stereo wells; The fracturing method selection module is used to select a target three-dimensional well fracturing method from the multiple different fracturing methods with the maximum total area of ​​the fracturing cracks in multiple three-dimensional wells as the objective function, and form a well group fracturing design optimization strategy.

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