Deep shale gas horizontal well perforation cluster point position optimization regulation and control fracture equilibrium extension simulation method

Abstract

The invention relates to a deep shale gas horizontal well perforation cluster point position optimization regulation and control fracture equilibrium extension simulation method, and belongs to the technical field of shale gas development. The invention discloses a deep shale gas horizontal well perforation cluster point position optimization regulation and control fracture equilibrium extension simulation scheme. The scheme comprises the steps that the full-well-section fracture pressure of a deep shale gas horizontal well is obtained; obtaining well depth positions of all perforation cluster points of the horizontal well section under the uniform perforation cluster arrangement of the deep shale gas horizontal well; the position of the perforation cluster point in each fractured well section is optimized and adjusted by taking the minimization of the fracture pressure difference at each cluster point in each fractured well section as a target; calculating a non-uniform stress field under fracture induced stress interference; and hydraulic fracture extension simulation before and after perforation cluster point position optimization of the fractured well section is carried out, and hydraulic fracture length variation coefficients before and after perforation cluster point position optimization are calculated. The method solves the problem of unbalanced extension of hydraulic fractures of all clusters in the fracturing section of the deep shale gas horizontal well, and improves the fracturing yield increasing effect of the deep shale gas horizontal well.

Description

Technical Field

[0001] The present invention relates to a simulation method for optimizing the position of perforation cluster points in horizontal wells of deep shale gas to control the balanced extension of fractures, and belongs to the technical field of shale gas development. Background Technique

[0002] Deep shale gas has strong heterogeneity. The in-situ stress, rock mechanical properties, natural fracture distribution density, and lithology at different perforation cluster points in the fracturing interval are different, resulting in large differences in the breakdown pressures at different perforation cluster points in the deep shale reservoir. When the breakdown pressure at a perforation cluster point is relatively small, the fractures in this cluster initiate and extend preferentially, thus inhibiting the increase in the bottom-hole pressure of this fracturing interval. The fractures in the perforation cluster with a larger breakdown pressure are difficult to initiate and extend or even cannot initiate, ultimately resulting in the perforation points with a larger breakdown pressure in this fracturing interval being ineffective cluster points, and the fractures in each cluster in the interval do not initiate and extend evenly. Aiming at the problem that it is difficult for the fractures in each cluster to initiate and extend evenly during the hydraulic fracturing of deep shale horizontal wells, in the hydraulic fracturing operation of horizontal wells, by adopting a non-uniform perforation clustering strategy and fully considering the influence of the breakdown pressure on the subsequent initiation and extension of fractures, the difference in the breakdown pressures of each perforation cluster point in the interval is minimized, which is conducive to improving the effectiveness of perforation cluster fracturing and the balanced initiation and extension of fractures in each cluster in the interval, and has guiding significance for the design of clustered perforation in deep shale gas horizontal wells in the field.

[0003] At present, most oil and gas fields usually adopt the empirical method for sectional clustering for specific blocks, without fully considering the negative effect of the breakdown pressure difference on the balanced initiation and extension of fractures. Previous studies have done a series of related research on how to conduct sectional clustering of horizontal wells. For example, Robin Slocombe et al. proposed a method for geometric sectional clustering of the horizontal section. Cipolla and Weng et al. believed that perforation should be carried out at positions where the minimum horizontal principal stresses in the interval are not very different. Askar Atanayev et al. designed the fracturing sections according to the reservoir quality and well completion quality. Nagel et al. optimized the well completion strategy considering the stress shadow between multiple clusters of fractures. Lu Cong and Guo Jianchun et al. established an interference model of stress between fractures and a criterion for determining fracture spacing based on the discontinuous displacement method. Yin Jian et al. established a model for characterizing the induced stress field of hydraulic fractures and optimized the criterion for fracture turning. However, the above studies have not fully considered the influence mechanism of the breakdown pressure on the initiation and extension of perforation clusters, nor have they specifically proposed corresponding technological countermeasures, and thus cannot quantitatively characterize and predict the improvement of the fracturing effect by optimizing the position of perforation cluster points.

[0004] Therefore, it is urgent to establish a simulation method for optimizing the position of perforation cluster points in horizontal wells of deep shale gas to control the balanced extension of fractures, which will help to further improve the scientificity and pertinence of deep shale gas fracturing design and improve the fracturing stimulation effect of deep shale gas horizontal wells. Summary of the Invention

[0005] The object of the present invention is to provide a simulation method for optimizing and regulating the balanced extension of fractures at the perforation cluster points of a horizontal well in deep shale gas, aiming at the problems existing in the prior art.

[0006] The technical solution provided by the present invention to solve the above technical problems is: a simulation method for optimizing and regulating the balanced extension of fractures at the perforation cluster points of a horizontal well in deep shale gas, which obtains the logging data, geological parameters, and construction parameters of the target deep shale gas;

[0007] Interpret the logging data to obtain the fracture pressure of the entire well section of the deep shale gas horizontal well;

[0008] Obtain the positions of all perforation cluster points in the horizontal well section under uniform perforation clustering of the deep shale gas horizontal well;

[0009] Taking the minimization of the fracture pressure difference at each cluster point within the fracturing well section as the target, optimize and adjust the positions of the perforation cluster points within each fracturing well section;

[0010] Calculate the non-uniform stress field under the interference of fracture-induced stress;

[0011] Carry out simulation of the hydraulic fracture extension before and after the optimization of the perforation cluster point positions in the fracturing well section according to the deep shale gas hydraulic fracture extension model, and calculate the coefficient of variation of the hydraulic fracture length before and after the optimization of the perforation cluster point positions respectively.

[0012] A further technical solution is that the geological parameters include the minimum horizontal principal stress of the formation, the maximum horizontal principal stress of the formation, Young's modulus, and Poisson's ratio; the construction parameters include displacement, fracturing fluid volume, fracturing time, fracturing fluid viscosity, fracturing fluid filtration coefficient, fracturing fluid density, average concentration of proppant injected during fracturing, number of perforation clusters, number of perforation holes in a single cluster, and diameter of perforation holes.

[0013] A further technical solution is that the fracture pressure of the entire well section of the deep shale gas horizontal well is the fracture pressure of the reservoir at every 0.125 m well depth from the A target point to the B target point in the horizontal section of the deep shale gas.

[0014] A further technical solution is that the specific method for obtaining the positions of all perforation cluster points in the horizontal well section under uniform perforation clustering of the deep shale gas horizontal well is: combining the cluster spacing between sections, the number of clusters in each fracturing section, and the well depth of the B target point under the uniform perforation clustering scheme, calculate the corresponding well depths from the first cluster in the first section to the last cluster in the last section in sequence.

[0015] A further technical solution is that the calculation formula for the well depth is:

[0016]

[0017] L2 = L1 - C1 ...............

[0019] L n = L n-1 - C1

[0020] ...............

[0022] Where: L1 represents the well depth of the first cluster, m; L2 represents the well depth of the second cluster, m; n represents the number of clusters in the first section, dimensionless; L n represents the well depth of the nth cluster, m; L n+1 represents the first cluster in the second section, i.e., the well depth of the (n + 1)th cluster, m.

[0023] A further technical solution is that, aiming at minimizing the fracture pressure difference at each cluster point within the fracturing well section, the specific steps for optimizing and adjusting the perforation cluster point positions within each fracturing well section are as follows:

[0024] Step 1: According to the fracture pressure profile of the entire well section of the deep shale gas horizontal well, obtain the fracture pressures at each cluster point in the first section, sort the fracture pressures of each cluster point from small to large, and then obtain the median of the fracture pressures of each cluster point;

[0025] Step 2: Search for the fracture pressure within the well depth range of 2 m before and after the first cluster in the first section to make it closest to the median of the fracture pressures;

[0026] Step 3: After the fracture pressure of the first cluster is updated, re-obtain the median of the fracture pressures of each cluster point in the first section. If the median of the fracture pressures does not change, search for the fracture pressure within the well depth range of 2 m before and after the second cluster to make it closest to the median of the fracture pressures. If the median of the fracture pressures remains unchanged, until the fracture pressure search within the well depth range of 2 m before and after all cluster points in the first section is completed;

[0027] Step 4: If the median of the fracture pressures changes, repeat Step 2 and Step 3, and re-search for the fracture pressure within the well depth range of 2 m before and after the first cluster in this well section to make it closest to the updated median of the fracture pressures, until the fracture pressure search within the well depth range of 2 m before and after all cluster points in the first section is completed;

[0028] Step 5: Record the well depth of the perforation cluster point corresponding to the fracture pressure point searched in the first section;

[0029] Step 6: Repeat Step 1 to Step 5 to update and record the well depths of the perforation cluster points in the entire horizontal well section.

[0030] A further technical solution is that the specific calculation process of the non-uniform stress field under the interference of fracture-induced stress is as follows:

[0031] Step 1: Establish a stress equilibrium equation set of the discrete fracture unit under the action of all fracture units and the stress boundary conditions of the discrete fracture unit;

[0032] Step 2: Solve for the normal strain (α n ) i and the tangential strain (α t ) i of the crack according to the stress boundary conditions of the crack discrete element;

[0033] Step 3: Substitute the normal strain and tangential strain of the crack into the non-uniform stress field solution equation to calculate the induced stress components caused by the crack at any point in the coordinate plane domain;

[0034] Step 4: Use the superposition principle to calculate the non-uniform in-situ stress field before fracturing and the current stress tensor at any point in the formation.

[0035] A further technical solution is that the deep shale hydraulic fracture extension model includes a fracture aperture equation, a fluid flow equation in a single fracture, a material balance equation for single fracture extension, a fracture height equation, fracture extension boundary conditions and initial conditions.

[0036] A further technical solution is that the simulation of hydraulic fracture extension includes the following steps:

[0037] Step 1: Calculate the extension length, height, and pressure inside the fracture of each hydraulic fracture during the fracturing process of a deep shale gas horizontal well according to the deep shale hydraulic fracture extension model;

[0038] Step 2: Based on the cluster point well depth and corresponding fracture initiation pressure parameters under uniform perforation clustering, calculate the fracture length variation coefficient of the hydraulic fractures in the fracturing well section by using the extension length of each hydraulic fracture in the fracturing well section.

[0039] A further technical solution is that the calculation formula for the fracture length variation coefficient of the hydraulic fracture is:

[0040]

[0041] In the formula: CV represents the fracture length variation coefficient, dimensionless; σ fLi represents the standard deviation of the fracture lengths of each cluster of fractures in the section, dimensionless; represents the average value of the fracture lengths of each cluster of fractures in the section, m; i represents the number of clusters in the section, dimensionless; f Li represents the fracture length of each cluster of fractures in the section, m.

[0042] The present invention has the following beneficial effects:

[0043] 1. This method specifically addresses the problem of uneven initiation and extension of multiple clusters of fractures in deep shale horizontal wells, considers the influence mechanism of fracture initiation pressure on fracture initiation and extension, ensures the minimization of the fracture initiation pressure difference between each perforation cluster point in the section, and thus proposes a simulation method for optimizing the position of perforation cluster points in deep shale gas horizontal wells to control the balanced extension of fractures;

[0044] 2. This method adheres to the concept of integrated geology and engineering for deep shale gas fracturing, fully considers the influence mechanism of reservoir geological characteristics on perforating parameters, and can conduct refined optimization design of the perforation cluster point positions according to the fracture pressure profile of the entire well section of the actual deep shale gas horizontal well. This will help further improve the scientificity and pertinence of deep shale gas fracturing design, solve the problem of uneven extension of hydraulic fractures in each cluster within the fracturing section of deep shale gas horizontal wells, and improve the fracturing stimulation effect of deep shale gas horizontal wells. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is a schematic diagram of the calculation process of the present invention;

[0046] Figure 2 It is a flow chart for optimizing the well depth position of perforation clusters;

[0047] Figure 3 It is a fracture pressure profile of the horizontal section of the well in the embodiment;

[0048] Figure 4 It is a distribution diagram of perforation clusters before and after optimization in the well of the embodiment;

[0049] Figure 5 It is a comparison diagram of the fracture pressure difference in each well section before and after optimizing the perforation clusters in the well of the embodiment;

[0050] Figure 6 It is a fracture extension diagram before optimizing the perforation clusters in the well of the embodiment;

[0051] Figure 7 It is a fracture extension diagram after optimizing the perforation clusters in the well of the embodiment;

[0052] Figure 8 It is a comparison diagram of the coefficient of variation of fracture length after optimizing the perforation clusters in the well of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0053] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0054] As Figure 1 shown, a method for optimizing the position of perforation clusters in a deep shale gas horizontal well to regulate the balanced extension of fractures provided by the present invention includes the following steps:

[0055] Step S10. Obtain the logging data, geological parameters, and construction parameters of the target deep shale gas;

[0056] Wherein the geological parameters include the minimum horizontal principal stress of the formation, the maximum horizontal principal stress of the formation, Young's modulus, and Poisson's ratio;

[0057] The construction parameters include displacement, fracturing fluid volume, fracturing time, fracturing fluid viscosity, fracturing fluid filtration coefficient, fracturing fluid density, average concentration of proppant injected during fracturing, number of perforation clusters, number of perforation holes in a single cluster, and perforation hole diameter;

[0058] Step S20: Interpret the fracture pressure of the entire well section of the deep shale gas horizontal well based on logging data, that is, the reservoir fracture pressure at every 0.125 m well depth from the A target point to the B target point in the horizontal section obtained by logging data interpretation;

[0059] Step S30: Obtain the positions of all perforation cluster points in the horizontal well section under uniform perforation clustering of the deep shale gas horizontal well;

[0060] The well depth positions of all perforation cluster points in the horizontal well section under uniform perforation clustering of the deep shale gas horizontal well can be calculated based on the cluster spacing between segments of each fracturing well section, the number of clusters in each fracturing segment, and the well depth of the B target point;

[0061]

[0062] In the formula: L1 represents the well depth of the first cluster, in m; L2 represents the well depth of the second cluster, in m; n represents the number of clusters in the first segment, dimensionless; L n represents the well depth of the nth cluster, in m; L n+1 represents the first cluster in the second segment, that is, the well depth of the (n + 1)th cluster, in m;

[0063] Step S40: Optimize and adjust the positions of perforation cluster points in each fracturing well section with the goal of minimizing the difference in fracture pressure at each cluster point within the fracturing well section;

[0064] Step S41: Obtain the fracture pressure at each cluster point in the first segment according to the fracture pressure profile of the entire well section of the deep shale gas horizontal well, sort the fracture pressures of each cluster point from smallest to largest, and then obtain the median of the fracture pressures of each cluster point;

[0065] Step S42: Search for the fracture pressure within the range of 2 m before and after the first cluster in the first segment to make it closest to the median of the fracture pressures;

[0066] After the fracture pressure of the first cluster is updated, re-obtain the median of the fracture pressures of each cluster point in the first segment. If the median of the fracture pressures remains unchanged, search for the fracture pressure within the range of 2 m before and after the second cluster to make it closest to the median of the fracture pressures. If the median of the fracture pressures remains unchanged, until the search for the fracture pressure within the range of 2 m before and after all cluster points in the first segment is completed;

[0067] Step S44: If the median fracture pressure changes, repeat Step S42 and Step S43 to re-search for the fracture pressure within the range of 2 m before and after the first cluster in this well section to make it closest to the updated median fracture pressure until the fracture pressure search within the range of 2 m before and after all cluster points in the first stage is completed;

[0068] Step S45: Record the well depth of the perforation cluster point corresponding to the fracture pressure point searched in the first stage;

[0069] Step S46: Repeat Step S41 to Step S45 to update and record the well depths of the perforation cluster points in the entire horizontal well section

[0070] Step S50: Calculate the non-uniform stress field under the interference of fracture-induced stress;

[0071] Based on the elastic mechanics theoretical model, use the displacement discontinuity method (DDM) to calculate the induced stress field generated by the hydraulic fracture.

[0072] First, establish the stress equilibrium equations of the discrete fracture element under the action of all fracture elements:

[0073]

[0074] Then the stress boundary condition of the discrete fracture element is:

[0075] (σ t ) i =0 (4)

[0076] (σ n ) i =-P fnet =-(P fluid -σ n ) (5)

[0077] In the formula: σ t represents the tangential stress on the fracture element, MPa; σ n represents the normal stress on the fracture element, MPa; (κ tt ) ij is the tangential stress component caused by the tangential displacement discontinuity of the j element on the i element; (κ tn ) ij represents the tangential stress component caused by the normal displacement discontinuity of the j element on the i element; (κ nt ) ij represents the normal stress component caused by the tangential displacement discontinuity of the j element on the i element; (κ nn ) ij represents the normal stress component caused by the normal displacement discontinuity of the j element on the i element; α t represents the tangential strain of the fracture j element in the local coordinate system, m; αn denotes the normal strain of crack element j in the local coordinate system, m; N denotes the number of crack elements; P fnet denotes the net pressure of the fluid in the crack, MPa;

[0078] According to the stress boundary conditions of the crack discrete element, solve for the normal strain of the crack (D n ) i and the tangential strain (D t ) i . Among them, the normal strain of the crack element (D n ) i is the aperture of the crack element.

[0079] Substitute the normal strain and tangential strain of the crack into the non-uniform stress field solution equation to calculate the induced stress components caused by the crack at any point in the coordinate plane domain;

[0080] The specific calculation equation is:

[0081]

[0082] Δσ zz = ν(Δσ xx + Δσ yy ) (9)

[0083] In the formula: Δσ xx , Δσ yy , Δσ zz , Δσ xy denote the induced stress components of the fault, MPa; C denotes the shear modulus of the reservoir rock, MPa; ν denotes the Poisson's ratio of the reservoir rock, dimensionless; α n , α t denote the horizontal offset and strike offset of the fault, m; ξ denotes the value of x in the global coordinate system converted to the local coordinate system; ζ denotes the value of y in the global coordinate system converted to the local coordinate system; m and n are the cosine values of the angles between the ζ axis of the local coordinate system and the x axis and y axis of the global coordinate system respectively; D3, D4, D5 denote the partial derivative equations of the Papkovitch function;

[0084] Since both the original in-situ stress field and the crack-induced stress field are three-dimensional second-order tensor fields, their components can be linearly superimposed.

[0085] Therefore, after calculating the induced stress, the pre-compression non-uniform in-situ stress field can be calculated using the superposition principle, and the current stress tensor at any point in the formation can be expressed as:

[0086]

[0087] In the formula: σ xx (0) , σ yy(0) , σ zz (0) , σ xy (0) , σ yz (0) , σ xz (0) represent the components of the original in-situ stress value, MPa; σ xx , σ yy , σ zz , σ xy , σ yz , σ xz represent the components of the in-situ stress value near the fault, MPa.

[0088] Step S60: According to the deep shale hydraulic fracture propagation model, carry out the simulation of the hydraulic fracture propagation before and after the optimization of the perforation cluster point positions in the fracturing interval, and calculate the coefficient of variation of the hydraulic fracture length before and after the optimization of the perforation cluster point positions respectively;

[0089] Step S61: Calculate the propagation length, height of each hydraulic fracture, and the pressure inside the fractures during the fracturing process of the horizontal well for deep shale gas according to the deep shale hydraulic fracture propagation model;

[0090] The deep shale hydraulic fracture propagation model includes a fracture aperture equation, a fluid flow equation in a single fracture, a material balance equation for the propagation of a single fracture, a fracture height equation, fracture propagation boundary conditions and initial conditions.

[0091] The fracture aperture equation is:

[0092]

[0093] In the formula: ω i (S, T) represents the aperture of the i-th fracture element at the length of S at the moment of T, m; H i (S, T) represents the height of the i-th fracture element at the length of S at the moment of T, m; P i (S, T) represents the fluid pressure inside the fracture of the i-th fracture element at the length of S at the moment of T, m; ν represents the Poisson's ratio, dimensionless; E represents the Young's modulus, Pa;

[0094] The fluid flow equation in a single fracture is:

[0095]

[0096] In the formula: P i (S, T) represents the fluid pressure at the position of S in the i-th fracture at the moment of T, Pa; Q i (S, T) represents the flow rate at the position of S in the i-th fracture at the moment of T, m 3 / s; H i(S, T) represents the height at the position S of the i-th crack at time T, m; ω i (S, T) represents the aperture at the position S of the i-th crack at time T, m; S i represents the coordinate in the length direction of the i-th crack, m; μ represents the viscosity of the fracturing fluid, Pa·s;

[0097] The material balance equation for the extension of a single crack is:

[0098]

[0099] Where:

[0100]

[0101] In the formula: C L represents the filtration coefficient of the fracturing fluid, m / s 0.5 ; T represents the fracturing time, s; τ i represents the filtration start time at the position S of the i-th crack, s;

[0102] The crack height equation is:

[0103]

[0104] In the formula: K IC represents the fracture toughness of the formation rock, Pa·m 0.5 ; σ n represents the minimum horizontal principal stress of the formation, Pa;

[0105] The crack extension boundary condition and initial condition equation are:

[0106]

[0107] In the formula: Q i (T) represents the flow rate at the crack mouth of the i-th crack at time T, m 3 / min; L i (T) represents the half-length of the i-th crack at time T, m; Q T represents the fracturing displacement, m 3 / min;

[0108] Step S62: Based on the cluster point well depth and the corresponding fracture pressure parameters under uniform perforation clustering, calculate the coefficient of variation of the hydraulic fracture length in the fracturing well section using the extension lengths of each hydraulic fracture in the fracturing process of the horizontal well in deep shale gas;

[0109]

[0110] In the formula: CV represents the coefficient of variation of the crack length, dimensionless; σ fLi represents the standard deviation of the crack lengths of each cluster of cracks in the section, dimensionless; It represents the average fracture length of each cluster within the section, in m; i represents the number of clusters within the section, dimensionless; f Li represents the fracture length of each cluster within the section, in m.

[0111] Example

[0112] Given that the well depth of the cluster points and the corresponding breakdown pressures of a typical deep shale gas horizontal well in the entire well section are shown in Table 1, and the actual geological engineering parameters of the well in the field are shown in Table 2. According to Figure 1 the process, carry out example calculations:

[0113] Table 1 Well depth of cluster points and corresponding breakdown pressures of a deep shale gas horizontal well in the entire well section

[0114]

[0115]

[0116]

[0117]

[0118]

[0119] Table 2 Table of actual geological engineering parameters of a deep shale gas well in the field

[0120]

[0121] First, use well logging data interpretation to obtain the reservoir breakdown pressure at every 0.125 m well depth from target point A to target point B in the horizontal section.

[0122] Subsequently, calculate the well depth positions of all perforation cluster points in the horizontal well section under uniform perforation cluster arrangement according to the cluster spacing of each fracturing well section, the number of clusters in each fracturing section, and the well depth of target point B;

[0123] The specific steps are as follows: Use formula (1), combined with the cluster spacing of each fracturing well section, the number of clusters in each fracturing section, and the well depth of target point B under uniform perforation cluster arrangement, and calculate the corresponding well depths from the first cluster of the first section to the last cluster of the last section in sequence.

[0124] Subsequently, with the goal of minimizing the breakdown pressure difference at each cluster point within the fracturing well section, optimize and adjust the perforation cluster point positions within each fracturing well section. The optimization results are shown in Table 3.

[0125] Table 3 Well depth and corresponding breakdown pressures of optimized cluster points in the entire well section of a deep shale gas horizontal well

[0126]

[0127]

[0128]

[0129]

[0130]

[0131]

[0132] Subsequently, by simultaneously solving equations (2) to (10) and combining with the fluid pressure in the fracture obtained in the next step, the non-uniform stress field and fracture aperture under the interference of fracture-induced stress are calculated.

[0133] Subsequently, a hydraulic fracture propagation model for deep shale is established, which includes a fracture aperture equation, a fluid flow equation in a single fracture, a material balance equation for a single fracture propagation, a fracture height equation, fracture propagation boundary conditions and initial conditions.

[0134] The specific steps are as follows: By coupling and simultaneously solving formulas (11) to (16), a hydraulic fracture propagation model for deep shale gas is established to calculate the propagation lengths and heights of each hydraulic fracture and the pressure inside the fractures during the fracturing process of a horizontal well in deep shale gas. The fracture aperture has been calculated in the previous step.

[0135] Subsequently, based on the cluster point well depth and corresponding fracture pressure parameters under uniform perforation cluster layout in Table 1, and using the propagation lengths of each hydraulic fracture in a section during the fracturing process of a horizontal well in deep shale gas, the variation coefficient of the hydraulic fracture length in this fracturing section is calculated by combining with formula (17).

[0136] Based on the cluster point well depth and corresponding fracture pressure parameters after optimizing the perforation cluster points in Table 3, and using the propagation lengths of each hydraulic fracture in a section during the fracturing process of a horizontal well in deep shale gas, the variation coefficient of the hydraulic fracture length after optimizing the cluster point positions in this fracturing section is calculated by combining with formula (17).

[0137] Among them, by simulating and calculating the fracture pressure and the variation coefficient of the hydraulic fracture length before and after optimizing the perforation cluster point positions of this well, after optimizing the perforation cluster points, the average fracture pressure difference of the whole well section is reduced from 7.04 MPa to 1.03 MPa, the average variation coefficient of the fracture length of all well sections is reduced from 0.22 to 0.09, the variation coefficient of the fracture length of each well section decreases, and all cluster point fractures in each well section are initiated.

[0138] The above description is not intended to impose any form of limitation on the present invention. Although the present invention has been disclosed through the above embodiments, it is not intended to limit the present invention. Any person skilled in the relevant art can make some changes or modifications to form equivalent embodiments by using the technical content disclosed above within the scope of the technical solution of the present invention. However, as long as it does not depart from the technical solution of the present invention, any simple modification, equivalent change, and modification made to the above embodiments based on the technical essence of the present invention shall fall within the scope of the technical solution of the present invention.

Claims

1. A simulation method for optimizing and regulating the balanced extension of fractures at the perforation cluster points in horizontal wells of deep shale gas, characterized in that, It includes the following steps: Obtain the logging data, geological parameters, and construction parameters of the target deep shale gas; Interpret the logging data to obtain the fracture pressure of the entire well section of the deep shale gas horizontal well; Obtain the positions of all perforation cluster points in the horizontal well section under uniform perforation clustering of the deep shale gas horizontal well; With the goal of minimizing the fracture pressure difference at each cluster point within the fracturing well section, optimize and adjust the positions of the perforation cluster points within each fracturing well section; Calculate the non-uniform stress field under the interference of fracture-induced stress; Carry out hydraulic fracture propagation simulations before and after optimizing the positions of the perforation cluster points in the fracturing well section according to the deep shale hydraulic fracture propagation model, and calculate the coefficient of variation of the hydraulic fracture length before and after optimizing the positions of the perforation cluster points respectively.

2. A simulation method for optimizing and regulating the balanced extension of fractures at the perforation cluster points in a deep shale gas horizontal well according to claim 1, characterized in that, The geological parameters include the minimum horizontal principal stress of the formation, the maximum horizontal principal stress of the formation, Young's modulus, and Poisson's ratio; the construction parameters include displacement, fracturing fluid volume, fracturing time, fracturing fluid viscosity, fracturing fluid filtration coefficient, fracturing fluid density, average concentration of proppant injected during fracturing, number of perforation clusters, number of perforation holes in a single cluster, and diameter of perforation holes.

3. A simulation method for optimizing and regulating the balanced extension of fractures at the perforation cluster points in a deep shale gas horizontal well according to claim 1, characterized in that, The fracture pressure of the entire well section of the deep shale gas horizontal well is the fracture pressure of the reservoir at every 0.125 m well depth from target point A to target point B in the horizontal section of the deep shale gas.

4. A simulation method for optimizing and controlling the balanced extension of fractures at the perforation cluster point positions in a deep shale gas horizontal well according to claim 1, characterized in that The specific method for obtaining the positions of all perforation cluster points in the horizontal well section under uniform perforation clustering of the deep shale gas horizontal well is as follows: Combine the cluster spacing of each fracturing well section, the number of clusters in each fracturing section, and the well depth of target point B under the uniform perforation clustering scheme, and calculate the corresponding well depths from the first cluster of the first section to the last cluster of the last section in sequence.

5. A simulation method for optimizing and controlling the balanced extension of fractures at the perforation cluster points in a deep shale gas horizontal well according to claim 4, characterized in that The calculation formula for the well depth is: L2 = L1 - C1 ............... L n = L n-1 - C1 ............... Where: L1 represents the depth of the first cluster of wells, in m; L2 represents the depth of the second cluster of wells, in m; n represents the number of clusters in the first stage, dimensionless; L n represents the depth of the nth cluster of wells, in m; L n+1 represents the first cluster in the second stage, i.e., the depth of the (n + 1)th cluster of wells, in m.

6. The simulation method for optimizing and regulating the balanced extension of fractures at the perforation cluster point positions in a deep shale gas horizontal well according to claim 1, wherein, The specific steps for optimizing and adjusting the positions of the perforation cluster points within each fracturing well section with the goal of minimizing the fracture pressure difference at each cluster point within the fracturing well section include the following steps: Step 1: According to the fracture pressure profile of the entire well section of the deep shale gas horizontal well, obtain the fracture pressure at each cluster point in the first section, sort the fracture pressures of each cluster point from small to large, and then obtain the median of the fracture pressures of each cluster point; Step 2: Search for the fracture pressure within the well depth range of 2 m before and after the first cluster in the first section to make it closest to the median of the fracture pressures; Step 3: After updating the fracture pressure of the first cluster, re-obtain the median of the fracture pressures of each cluster point in the first section. If the median of the fracture pressures remains unchanged, search for the fracture pressure within the well depth range of 2 m before and after the second cluster to make it closest to the median of the fracture pressures. If the median of the fracture pressures remains unchanged, continue until the fracture pressure search within the well depth range of 2 m before and after all cluster points in the first section is completed; Step 4: If the median of the fracture pressures changes, repeat Step 2 and Step 3, and re-search for the fracture pressure within the well depth range of 2 m before and after the first cluster in this well section to make it closest to the updated median of the fracture pressures until the fracture pressure search within the well depth range of 2 m before and after all cluster points in the first section is completed; Step 5: Record the well depths of the perforation cluster points corresponding to the fracture pressure points searched in the first section; Step 6: Repeat Step 1 to Step 5, update and record the well depths of the perforation cluster points in the entire horizontal well section.

7. A simulation method for optimizing and controlling the balanced extension of fractures at the perforation cluster points in a deep shale gas horizontal well according to claim 1, characterized in that, The specific calculation process of the non-uniform stress field under the interference of fracture-induced stress is as follows: Step 1: Establish a stress equilibrium equation set of the discrete fracture unit under the action of all fracture units and the stress boundary conditions of the discrete fracture unit; Step 2: Solve for the normal strain (α n ) i and the tangential strain (α t ) i ; Step 3: Substitute the normal strain and tangential strain of the fracture into the non-uniform stress field solution equation to calculate the induced stress components caused by the fracture at any point within the coordinate plane domain; Step 4: Use the superposition principle to calculate the pre-pressure non-uniform in-situ stress field and the current stress tensor at any point in the formation.

8. A simulation method for optimizing and controlling the balanced extension of fractures at the perforation cluster points in a deep shale gas horizontal well according to claim 1, characterized in that, The deep shale hydraulic fracture propagation model includes a fracture aperture equation, a fluid flow equation within a single fracture, a material balance equation for single fracture propagation, a fracture height equation, fracture propagation boundary conditions, and initial conditions.

9. The simulation method for optimizing and regulating the balanced extension of fractures at the perforation cluster points in a deep shale gas horizontal well according to claim 1, characterized in that, The simulation of hydraulic fracture propagation includes the following steps: Step 1: Calculate the propagation lengths, heights, and pressures within the fractures during the fracturing process of horizontal wells in deep shale gas according to the deep shale hydraulic fracture propagation model; Step 2: Based on the cluster point well depths and corresponding breakdown pressure parameters under uniform perforation clustering, use the propagation lengths of each hydraulic fracture within a fracturing stage during the fracturing process of horizontal wells in deep shale gas to calculate the coefficient of variation of the hydraulic fracture lengths within this fracturing stage.

10. A simulation method for optimizing and regulating the balanced extension of fractures at the perforation cluster points in a deep shale gas horizontal well according to claim 9, characterized in that, The calculation formula for the coefficient of variation of the hydraulic fracture length is: In the formula: CV represents the coefficient of variation of the seam length, dimensionless; σ fLi represents the standard deviation of the crack lengths of each cluster within the section, dimensionless; represents the average crack length of each cluster within the section, m; i represents the number of clusters within the section, dimensionless; f Li represents the crack length of each cluster within the section, m.

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