Shale gas horizontal well staged fracturing perforation parameter optimization method considering hole abrasion

Abstract

The invention provides a shale gas horizontal well staged fracturing perforation parameter optimization method considering hole abrasion, belongs to the technical field of hydraulic fracturing, and solves the problems that an existing method cannot consider completely and cannot meet field requirements. Comprising the steps that S1, geological data and a fracturing construction scheme of a target well are obtained, and an initial perforation parameter combination and an initial crack unit are set; s2, a crack tip stress intensity factor is calculated, the crack initiation condition is judged, and the crack extension length is determined; s3, the fluid pressure, the crack unit width and the perforation hole diameter in all hydraulic crack units in the fracturing construction process are calculated in an extended mode; s4, according to an expansion calculation result, a hydraulic fracture uniformity coefficient is calculated, and on the basis of the hydraulic fracture uniformity coefficient, the initial perforation parameter combination is optimized and adjusted by selecting and modifying the perforation parameter combination; according to the method, the optimal perforation scheme can be determined, a basis is provided for fracturing construction and perforation scheme design, and efficient development of shale gas resources is promoted.

Description

Technical Field

[0001] The invention belongs to the technical field of hydraulic fracturing, is applied in the process of shale gas development, and specifically is a method for optimizing perforation parameters of shale gas horizontal well staged fracturing taking hole erosion into consideration. Background Art

[0002] At present, volume fracturing is the main means of shale gas development. Its purpose is to achieve effective reservoir transformation by shortening the cluster spacing and reducing the seepage distance from the matrix to the fracture through horizontal well segmented multi-cluster fracturing technology. Therefore, how to ensure the effective expansion of each cluster in the case of multiple clusters is the key issue in optimizing the multi-cluster fracturing technology.

[0003] During the fracturing process, under the influence of reservoir heterogeneity and stress shadow, the cracks in the same fracturing section will expand non-uniformly, and a dominant flow channel will be formed in the section. The perforation holes at the dominant flow channel will be more obviously eroded, which will increase the hole size at the dominant fracture, increase the liquid inflow, and further aggravate the non-uniform expansion of the fracture. This situation will significantly reduce the effect of fracturing transformation and is not conducive to the efficient development of shale gas. Adjusting the perforation parameters and controlling the distribution of fracture flow have become the main means to improve the uniformity of hydraulic fractures; the reasonable selection of perforation parameters is also of great significance to improving the effect of fracturing transformation.

[0004] In the prior art, the method of optimizing perforation parameters is mainly to establish a numerical model of fracture extension, consider the influence of different rock mechanics or engineering parameters on fracture extension to study the law, so as to guide the optimization of perforation parameters. The document "Optimization Design of Multi-stage Cluster Perforation in Horizontal Wells" established a fracture extension model considering the friction resistance of the hole to analyze the influence of the friction resistance of the hole on the fracturing effect; however, this method ignores the dynamic change of the hole diameter, and therefore lacks the analysis of the difference in the initiation of fracture in each cluster caused by the difference between the holes after abrasion.

[0005] The document "A New Method for Optimal Design of Perforation Parameters Based on Optimal Penetration Analysis" established a productivity model with skin coefficient after perforation to analyze the influence of skin coefficient on productivity, so as to optimize perforation parameters; however, this method was not combined with the fracturing model and did not consider the dynamic changes in the fracturing section caused by the fracturing process. It can be seen that the existing method does not consider the change of perforation diameter caused by hole abrasion during the fracturing process, and does not use the actual engineering parameters for simulation, so the perforation parameter optimization results obtained by it cannot meet the actual needs of the site. Summary of the invention

[0006] The present invention solves the problem that the prior art is not well considered during the perforation parameter optimization process and cannot meet the on-site needs, and proposes a method for optimizing the perforation parameters of shale gas horizontal well staged fracturing considering perforation abrasion. The present invention combines the displacement discontinuity method with the perforation perforation abrasion model, establishes a multi-fracture expansion model considering the dynamic changes of the perforation, obtains the hydraulic fracture uniformity coefficient under different perforation parameters through simulation calculation, and thus determines the optimal perforation scheme, providing a basis for fracturing construction and perforation scheme design, and promoting the efficient development of shale gas resources.

[0007] The present invention adopts the following technical solutions to achieve the purpose:

[0008] A method for optimizing perforation parameters of staged fracturing of shale gas horizontal wells considering perforation erosion, the method comprising the following steps:

[0009] S1. Obtain geological data and fracturing construction plan of the target well, and set the initial perforation parameter combination and initial fracture unit;

[0010] S2. Calculate the stress intensity factor of the crack tip in the initial crack unit based on the initial perforation parameters and the data of the initial crack unit, judge the crack initiation situation, and determine the crack extension length;

[0011] S3. Based on the calculation of the initial fracture unit, the fluid pressure, fracture unit width and perforation hole diameter in all hydraulic fracture units are calculated at a continuous time during the fracturing construction process;

[0012] S4. Calculate the hydraulic fracture uniformity coefficient according to the extended calculation result of step S3; and optimize and adjust the initial perforation parameter combination by selecting and modifying the perforation parameter combination according to the hydraulic fracture uniformity coefficient.

[0013] Specifically, in step S1, among multiple groups of different perforation parameter combinations, one group is selectively set as an initial perforation parameter combination; the parameters in the perforation parameter combination include perforation density and hole diameter.

[0014] Specifically, after executing step S4 under the initial perforating parameter combination, if the hydraulic fracture uniformity coefficient finally calculated does not meet the shale gas well development requirements, the initial perforating parameter combination needs to be optimized and adjusted; the optimization and adjustment method is: from the preset multiple groups of different perforating parameter combinations, select another group set as the initial perforating parameter combination in step S1, and proceed to step S4, calculate the hydraulic fracture uniformity coefficient again and make a judgment until the shale gas development requirements are met.

[0015] Furthermore, in step S1, based on the geological data of the target well and the fracturing construction plan, the perforation density and hole diameter that can be used in the current development process are determined to form multiple groups of different perforation parameter combinations; when setting the initial fracture unit, the number of units and unit length of each cluster of fractures are preset, and the direction of the initial fracture unit is perpendicular to the wellbore.

[0016] Furthermore, in step S2, the boundary element displacement discontinuity method is used to calculate the stress intensity factor at the crack tip; in this process, the stress field formed by each crack unit at the crack end position is superimposed, and the fluid pressure and width in each crack unit are made the same; then, based on the position of the crack unit at the time t0 when fracturing starts, the upper and lower end position coordinates of each cluster of cracks in the global coordinate system are determined and expressed respectively.

[0017] Specifically, when the position coordinates of the crack unit at time t0 are determined, the center of the first crack unit is selected as the origin, and the crack direction is A local coordinate system is established in the direction of the axis, and the position coordinates of all crack endpoints are converted into the position coordinates in the local coordinate system of the first crack unit and expressed respectively, and then the normal discontinuous displacement formed by the first crack unit at the mth crack endpoint at time t0 is calculated.

[0018] Specifically, the same method is used to select the center of the remaining crack unit as the origin, and then the normal discontinuous displacements formed at the mth crack endpoint of all crack units at time t0 are calculated respectively; then, all the normal discontinuous displacements at the mth crack endpoint are superimposed, and the stress intensity factor at the mth crack endpoint at time t0 is obtained by the following formula:

[0019]

[0020] In the formula, is the discontinuous displacement coefficient generated by the e-th fracture unit at the m-th fracture endpoint at time t0; E is the Young's modulus of the reservoir, v is the Poisson's ratio; P F,m is the fracture unit pressure at the end point of the mth fracture at time t0, in MPa; is the stress intensity factor at the mth crack endpoint at time t0, in units of σ h is the minimum horizontal principal stress of the reservoir, in MPa; r m is the half length of the crack unit at the end point of the mth crack, in mm.

[0021] Specifically, the stress intensity factor K at the mth crack endpoint at time t0 is I,m,t0 , and the fracture toughness K of the storage rock IC Compare to determine the crack initiation situation; if ≤KIC , then it is judged that the crack does not expand; if It is judged that the crack has expanded at this endpoint, the number of crack units is increased by 1, and the width of the new crack unit is recorded as 0; the stress intensity factors of the remaining crack tips are continuously calculated and the same judgment is made. When the crack expansion and extension conditions at all crack endpoints are judged, the total number of crack units N and the corresponding crack unit width after the crack expansion at time t0 are obtained.

[0022] Furthermore, in step S3, based on the total number N of fracture units at time t0 and the width of the corresponding fracture units, a fracture extension model that takes into account the loss of fracturing fluid is selected as the fracture flow model that takes into account the pore abrasion; after determining the initial conditions and boundary conditions of the model, a numerical solution is performed to obtain the width of each fracture unit at time t1, the fracture pressure of each fracture unit, the pore diameter of each cluster of fractures, the liquid inflow of each cluster of fractures, and the pore flow coefficient of each cluster of fractures; all the obtained parameters are substituted into the process of steps S2 and S3 again to calculate the corresponding parameters at time t2; the calculation is repeated until the fracturing ends at time t end At this time, the loop calculation ends and all the obtained parameter results are substituted into step S4.

[0023] Further, in step S4, according to the fracturing end time t end The hydraulic fracture uniformity coefficient K is calculated based on the corresponding parameters; when K≤0.08, it means that the current development requirements of shale gas wells can be met, and there is no need to optimize and adjust the initial perforation parameter combination selected in step S1; on the contrary, when K>0.08, it means that the requirements are not met, and a new perforation parameter combination needs to be selected for recalculation.

[0024] In summary, due to the adoption of this technical solution, the beneficial effects of the present invention are as follows:

[0025] The present invention establishes a multi-fracture expansion model that takes into account the dynamic changes of perforations based on the perforation hole abrasion model; in this part, when considering the changes in the perforation hole diameter caused by perforation hole abrasion during the fracturing process, the present invention combines the displacement discontinuity method with the perforation hole abrasion model to establish a multi-fracture expansion model that takes into account the dynamic changes of the perforations; subsequently, the present invention obtains the hydraulic fracture uniformity coefficient under different perforation parameters through simulation calculation, thereby determining the optimal perforation parameter scheme, providing a basis for fracturing construction and perforation scheme design, and promoting the efficient development of shale gas resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the overall process of the method of the present invention;

[0027] Figure 2 This is the original fracture parameter diagram at the end of the fracturing simulation of Well Y1;

[0028] Figure 3 This is the original fracture morphology diagram at the end of the fracturing simulation of Well Y1;

[0029] Figure 4 This is the hydraulic fracture parameter diagram of Well Y1 after adjusting the perforation parameters;

[0030] Figure 5 This is the hydraulic fracture morphology diagram of Well Y1 after adjusting the perforating parameters. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0032] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] Example 1

[0034] like Figure 1 As shown, a method for optimizing perforation parameters of staged fracturing of shale gas horizontal wells considering hole abrasion is provided. This embodiment will introduce the specific content of each step in full detail according to the execution order of the steps of the method.

[0035] 1. Obtain the geological parameters and engineering parameters of the target well reservoir and add initial fracture units.

[0036] Based on the geological data of the target well and the fracturing construction plan, the following basic information can be determined: Young's modulus E of the reservoir; Poisson's ratio v; maximum horizontal principal stress σ H ; Minimum horizontal principal stress σ h ; Perforation density M p ; Hole diameter D p ; Cluster number L frac ; Cluster length L c ; Cluster spacing S frac ; From this, we can get the number of perforations per cluster N p =M p ×L c .

[0037] In this embodiment, a plurality of different perforation parameter combinations are preset as shown in Table 1 below, and the perforation parameters in combination number 1 are selected as the initial perforation density and hole diameter of this embodiment.

[0038] Table 1 Perforation parameter combination table

[0039]

[0040] Next, the initial fracture units of the hydraulic fractures are set. In this embodiment, the number of initial fracture units of each fracture cluster is set to 3, each fracture unit is 1 m long, and the direction of the initial fracture unit is perpendicular to the wellbore; the number of fracture units will increase in the subsequent process as the fractures expand.

[0041] In this embodiment, the total number of hydraulic fracture endpoints is 2×L frac , the fracture endpoint is numbered m; the total number of fracture units is N; the fracture unit is numbered e; the fluid pressure in the e-th fracture unit is R F,e ; The width of the e-th crack unit is w F,e .

[0042] 2. Calculate the stress intensity factor at the crack tip, determine the crack initiation situation, and determine the crack extension length.

[0043] In this embodiment, the boundary element displacement discontinuity method is used to obtain the stress intensity factor at the crack tip. This method requires superimposing the stress field formed by each crack unit at the crack end position.

[0044] First, the fluid pressure and width of each fracture unit are set to be the same. According to the position of the fracture unit at the start time t0 of fracturing, the upper and lower end point coordinates of each cluster of fractures in the global coordinate system are determined, which are expressed as (x1, y1)…(x m ,y m ).

[0045] Then, the center of the first crack unit is selected as the origin, and the crack direction is Axis direction, establish local coordinate system The position coordinates of all crack endpoints are converted to the position coordinates in the local coordinate system of the first crack unit, which are expressed as On this basis, the normal discontinuous displacement formed by the first crack unit at the end point of the mth crack at time t0 is calculated according to the following three formulas:

[0046]

[0047]

[0048]

[0049] In the above formulas, is the coordinate of the mth crack endpoint in the local coordinate system of the first crack unit; a1 is the half length of the first crack unit, in m; f a(1,m) 、f b(1,m) 、f c(1,m) , A xc(1,m) , A yy(1,m) , A xy(1,m) is the intermediate function in the calculation process; v is the Poisson's ratio of the reservoir rock; is the Young's modulus of the reservoir rock, in GPa; α1 is the local coordinate system of the first fracture unit The angle between the axis and the x-axis of the global coordinate system; w m is the width of the crack unit where the mth crack endpoint is located, in mm; That is, it is the discontinuous displacement coefficient generated by the first crack unit at the end point of the mth crack at time t0.

[0050] By using the above method, the discontinuous displacement coefficients generated by all crack units at the mth crack endpoint at time t0 are continued to be calculated. All normal discontinuous displacements at the mth crack endpoint are superimposed, and then the stress intensity factor at the mth endpoint at time t0 is obtained by the following calculation:

[0051]

[0052] In the formula, is the discontinuous displacement coefficient generated by the e-th crack unit at the m-th crack endpoint at time t0; P F,m is the fracture unit pressure at the end point of the mth fracture at time t0, in MPa; is the stress intensity factor at the mth crack endpoint at time t0, in units of σ h is the minimum horizontal principal stress of the reservoir, in MPa; r m is the half length of the crack unit at the end point of the mth crack, in mm.

[0053] The stress intensity factor at the mth crack endpoint at time t0 is and the fracture toughness K of reservoir rock IC Compare; judge the expansion of the crack, if The crack does not expand; if The crack expands at this end point, the number of crack units increases by 1, and the width of the new crack unit is 0. Continue to calculate the stress intensity factor of the next crack tip and make the same judgment on its expansion as above.

[0054] After the crack extension and extension at all crack endpoints are judged, the total number of crack units N after crack extension at time t0 and the width of the e-th crack unit at time t0 are obtained.

[0055] 3. Calculate the fluid pressure in the fracture unit, the width of the fracture unit and the diameter of the perforation hole during the fracturing process.

[0056] Based on the number of fracture units and the width of fracture units after fracture expansion obtained in the second part, combined with the fracture flow model considering the pore friction resistance, the fluid pressure and fracture unit width in the hydraulic fracture unit at time t1 during the fracturing construction process are obtained.

[0057] In this embodiment, for the in-fracture flow model considering the pore friction resistance, the "fracture extension model considering fracturing fluid loss" in the prior art is selected; this model comes from the document "Experimental Research and Numerical Analysis on Temporary Plugging and Diversion of Staged Fracturing in Horizontal Wells". This embodiment will no longer introduce the specific content of the model, but will explain in detail the parameters and calculation formulas involved in the method of this embodiment.

[0058] First, consider the fracture propagation model of fracturing fluid loss, as follows:

[0059]

[0060] In the formula, μ w is the viscosity of the fracturing fluid, in mPa·s; w F is the hydraulic fracture width, in m; Q is the flow rate of fracturing fluid entering the fracture, in m 3 / s;h F is the height of hydraulic fracture, in m; δ F is the source term coefficient, which takes the value of 1 when the fracture unit passes through the wellbore and takes the value of 0 when it does not pass through the wellbore; E is the Young's modulus of the reservoir rock, in MPa; v is the Poisson's ratio of the reservoir rock.

[0061] In this embodiment, the following initial conditions are set:

[0062]

[0063] In the formula, w F,L,t＝0 is the initial crack width before fracturing construction begins, in m; Q t＝0 The pumping flow rate before fracturing construction begins, in m 3 / s.

[0064] Next, the boundary conditions corresponding to the model are as follows:

[0065]

[0066] In the formula, Qt＞0 It is the pumping flow rate after the fracturing construction starts, in m 3 / s;P F,z,i is the pressure at the opening of the i-th crack, in MPa; P Fric,i is the friction resistance of the i-th crack hole, unit: MPa; P wF is the bottom hole pressure, unit: MPa; Q i is the liquid inflow into the i-th crack, m 3 / s; β is the unit conversion coefficient; D p,i is the hole diameter of the i-th fracture, in m; ρ is the density of the fracturing fluid, in kg / m 3 ; N p,i is the number of holes in the i-th crack; C d,i is the hole flow coefficient of the i-th crack, ranging from 0.6 to 0.95; C pc is the proppant concentration, in kg / m 3 ; is the maximum hole flow coefficient of the ith crack, which is 0.95.

[0067] Based on the above information, the fracturing model can be numerically solved to obtain the parameters at time t1: the width of each fracture unit The pressure inside each fracture unit The diameter of each crack cluster Liquid inflow per crack cluster and the perforation discharge coefficient of each cluster of fractures

[0068] The parameters at time t1 are processed again in the second and third parts of the method of this embodiment to further calculate the width of the fracture unit, the pressure inside the fracture unit, and the total number of hydraulic fracture units at time t2 = t1 + 1s, thereby realizing a cyclic calculation process under a continuous time. Finally, when the time reaches the end time of fracturing t end After that, the loop calculation ends and you can enter the fourth part of the method.

[0069] 4. Calculate the uniformity coefficient of hydraulic fractures.

[0070] After fracturing, t end The number of hydraulic fracture units in the i-th time is Since the length of the fracture units pre-set in the first part of this embodiment is 1 m, the length of the i-th hydraulic fracture is

[0071] Therefore, the hydraulic fracture uniformity coefficient K can be calculated according to the length of each cluster of cracks as follows:

[0072]

[0073] In this embodiment, if K≤0.08, the uniformity of the hydraulic fracture can meet the development requirements of the shale gas well, and there is no need to adjust the number of perforation holes and the perforation hole diameter; if K>0.08, the perforation parameters need to be adjusted to the perforation density and hole diameter of combination number 2 in the first part.

[0074] According to the adjusted perforation density and hole diameter, repeat the second and third parts of the method of this embodiment, calculate the length of each cluster of cracks after the fracturing is completed, and then use the formula to calculate the hydraulic fracture uniformity coefficient K again, and judge whether the fracture uniformity meets the requirements. If the requirements are met, the perforation parameters at this time are optimal, and the optimization adjustment process is completed; if the requirements are still not met, select the next perforation parameter combination for calculation.

[0075] Example 2

[0076] On the basis of Example 1, this example applies the method of Example 1, and illustrates the application of the present invention through experimental data in an actual shale gas well development scenario.

[0077] This example uses the perforation parameter optimization method to perform simulation calculations and draw Figures 2 to 5 The fracture comparison diagram before and after adjusting the perforation parameters is shown in FIG. 1 . By optimizing the perforation parameters, the fracture uniformity is improved. The calculation steps for the shale gas well in this embodiment are performed as follows.

[0078] 1. Optimization steps.

[0079] (1) According to the geological data and fracturing construction plan of Well Y1, the Young's modulus of the reservoir is determined to be 35 GPa; Poisson's ratio is 0.21; the maximum horizontal principal stress is 108 MPa; the minimum horizontal principal stress is 96 MPa; the number of clusters is 7; the cluster length is 1 m; and the cluster spacing is 10 m. According to the perforation parameters of Combination 1 in Table 1 of Example 1, the perforation density is 16 holes / m; the hole diameter is 10 mm. The initial number of fracture units is 3; the total number of hydraulic fracture endpoints is 14; the total number of initial fracture units is 21; and the fluid pressure in the fracture unit is P F,1 ,P F,1 ,…,P F,21 ; The width of the crack unit is w F,1 ,w F,1 ,…,w F,21 .

[0080] (2) Using the obtained parameters, the stress intensity factor at the two tips of the first crack at t0 = 0s is obtained by the formula in the second part of Example 1: Determine the expansion of the two ends of the first crack at t0 = 0s. If the crack expands, add a crack unit at this end; if the crack expansion condition is not met, the crack length remains unchanged. Calculate the stress intensity factors of the two ends of the second to seventh cracks in turn to determine the expansion. In this way, the parameters of each crack at t0 = 0s are obtained.

[0081] (3) Using the number of fracture units after fracture expansion, the fracture unit width, and the reservoir parameters of Well Y1, the width w of each fracture unit at t1 = 1 s is obtained by the calculation method of the third part of Example 1. F,e,1s , the pressure inside each fracture unit P F,e,1s , the hole diameter D of each cluster of cracks P,i,1s , the amount of liquid inflow per cluster of cracks Q i,1s and the perforation flow coefficient C of each cluster of cracks d,i,1s By means of a cyclic calculation method, the parameters obtained in this calculation are again substituted into the second and third parts of Example 1 to perform the calculation at the next time step t2 = 2s. The calculation is cyclically calculated until the fracturing ends at time t end =60min.

[0082] (4) The length L of each cluster of fractures is obtained by using the number of units of each fracture after the fracturing simulation is completed. F , calculate the hydraulic fracture uniformity coefficient K1 by the formula in the fourth part of Example 1, and evaluate whether the perforation parameters meet the fracture uniformity requirements of Well Y1. If not, repeat the above contents by selecting the fracture parameters of Combination 2 in Table 1, and calculate the fracture uniformity coefficient K2 in Combination 2 according to the simulation calculation results. If it still cannot meet the requirements, select the next perforation parameter combination for calculation. Finally, the simulation obtains the hydraulic fracture uniformity coefficient K2 that meets the requirements. n , then the best perforation parameters are the optimal result.

[0083] 2. Optimize results and analysis.

[0084] The fracturing simulation results obtained by selecting combination 1 in Table 1, the fracture parameters and morphology can be found in Figure 2 , Figure 3 ; the lengths of the 7 fractures are 119m, 89m, 71m, 57m, 71m, 87m and 117m respectively; the calculation formula shows that the hydraulic fracture uniformity coefficient K1=0.2428 at this time, so the perforation parameters of combination 1 cannot meet the fracture uniformity requirements of well Y1.

[0085] The final simulation results of the fracturing under combination 4 are obtained. The fracture parameters and morphology can be found in Figure 3 , Figure 4Schematic diagram; the lengths of the 7 cracks are 89m, 99m, 95m, 91m, 93m, 97m and 87m respectively; the calculation formula shows that the hydraulic fracture uniformity coefficient K = 0.043 at this time, so the optimal perforation parameters can be determined as: perforation density 16 holes / m; hole diameter 8.8mm.

Claims

1. A method for optimizing perforation parameters of staged fracturing of shale gas horizontal wells considering perforation erosion, characterized in that: The method comprises the following steps: S1. Obtain geological data and fracturing construction plan of the target well, and set the initial perforation parameter combination and initial fracture unit; S2. Calculate the stress intensity factor of the crack tip in the initial crack unit based on the initial perforation parameters and the data of the initial crack unit, judge the crack initiation situation, and determine the crack extension length; S3. Based on the calculation of the initial fracture unit, the fluid pressure, fracture unit width and perforation hole diameter in all hydraulic fracture units are calculated at a continuous time during the fracturing construction process; S4. Calculate the hydraulic fracture uniformity coefficient according to the extended calculation result of step S3; and optimize and adjust the initial perforation parameter combination by selecting and modifying the perforation parameter combination according to the hydraulic fracture uniformity coefficient.

2. The method for optimizing perforation parameters of shale gas horizontal well staged fracturing considering hole erosion according to claim 1, characterized in that: In step S1, among multiple groups of different perforation parameter combinations, one group is selectively set as an initial perforation parameter combination; the parameters in the perforation parameter combination include perforation density and hole diameter.

3. The method for optimizing perforation parameters of shale gas horizontal well staged fracturing considering hole erosion according to claim 2, characterized in that: After executing step S4 under the initial perforating parameter combination, if the hydraulic fracture uniformity coefficient finally calculated does not meet the shale gas well development requirements, the initial perforating parameter combination needs to be optimized and adjusted; the optimization and adjustment method is: from the preset multiple groups of different perforating parameter combinations, select another group set as the initial perforating parameter combination in step S1, and proceed to step S4, calculate the hydraulic fracture uniformity coefficient again and make a judgment until the shale gas development requirements are met.

4. The method for optimizing perforation parameters of shale gas horizontal well staged fracturing considering hole erosion according to claim 1, characterized in that: In step S1, based on the geological data of the target well and the fracturing construction plan, the perforation density and hole diameter that can be used in the current development process are determined to form multiple groups of different perforation parameter combinations; when setting the initial fracture unit, the number of units and unit length of each cluster of fractures are preset, and the direction of the initial fracture unit is perpendicular to the wellbore.

5. The method for optimizing perforation parameters of shale gas horizontal well staged fracturing considering hole erosion according to claim 4, characterized in that: In step S2, the boundary element displacement discontinuity method is used to calculate the stress intensity factor at the crack tip; In this process, the stress field formed by each fracture unit at the fracture end position is superimposed, and the fluid pressure and width in each fracture unit are made the same; Subsequently, according to the position of the fracture unit at the time t0 when the fracturing starts, the upper and lower endpoint position coordinates of each cluster of fractures in the global coordinate system are determined and expressed respectively.

6. The method for optimizing perforation parameters of staged fracturing of shale gas horizontal wells considering hole abrasion according to claim 5, characterized in that: When the position coordinates of the crack unit at time t0 are determined, the center of the first crack unit is selected as the origin and the crack direction is taken as the A local coordinate system is established in the direction of the axis, and the position coordinates of all crack endpoints are converted into the position coordinates in the local coordinate system of the first crack unit and expressed respectively, and then the normal discontinuous displacement formed by the first crack unit at the mth crack endpoint at time t0 is calculated.

7. The method for optimizing perforation parameters of shale gas horizontal well staged fracturing considering hole erosion according to claim 6, characterized in that: Using the same method, the center of the remaining crack unit is selected as the origin, and then the normal discontinuous displacement formed at the mth crack endpoint of all crack units at time t0 is calculated respectively; then, all the normal discontinuous displacements at the mth crack endpoint are superimposed, and the stress intensity factor at the mth crack endpoint at time t0 is obtained by the following formula: In the formula, is the discontinuous displacement coefficient generated by the e-th fracture unit at the m-th fracture endpoint at time t0; E is the Young's modulus of the reservoir, v is the Poisson's ratio; P F,m is the fracture unit pressure at the end point of the mth fracture at time t0, in MPa; is the stress intensity factor at the mth crack endpoint at time t0, in units of σ h is the minimum horizontal principal stress of the reservoir, in MPa; r m is the half length of the crack unit at the end point of the mth crack, in mm.

8. The method for optimizing perforation parameters of staged fracturing of shale gas horizontal wells considering hole erosion according to claim 7, characterized in that: The stress intensity factor at the mth crack endpoint at time t0 is and the fracture toughness K of the storage rock IC Compare to determine the crack initiation situation; if It is judged that the crack does not expand; if It is judged that the crack has expanded at this endpoint, the number of crack units is increased by 1, and the width of the new crack unit is recorded as 0; the stress intensity factors of the remaining crack tips are continuously calculated and the same judgment is made. When the crack expansion and extension conditions at all crack endpoints are judged, the total number of crack units N and the corresponding crack unit width after the crack expansion at time t0 are obtained.

9. The method for optimizing perforation parameters of staged fracturing of shale gas horizontal wells considering hole abrasion according to claim 8, characterized in that: In step S3, based on the total number N of fracture units and the width of the corresponding fracture units at time t0, a fracture extension model that considers fracturing fluid filtration is selected as the fracture flow model that considers pore abrasion; after determining the initial conditions and boundary conditions of the model, a numerical solution is performed to obtain the width of each fracture unit at time t1, the fracture pressure of each fracture unit, the pore diameter of each cluster of fractures, the liquid inflow of each cluster of fractures, and the pore flow coefficient of each cluster of fractures; all the obtained parameters are substituted into the process of steps S2 and S3 again to calculate the corresponding parameters at time t2; the calculation is repeated until the fracturing ends at time t end At this time, the loop calculation ends and all the obtained parameter results are substituted into step S4.

10. The method for optimizing perforation parameters of staged fracturing of shale gas horizontal wells considering hole abrasion according to claim 9, characterized in that: In step S4, according to the fracturing end time t end The hydraulic fracture uniformity coefficient K is calculated based on the corresponding parameters; when K≤0.08, it means that the current development requirements of shale gas wells can be met, and there is no need to optimize and adjust the initial perforation parameter combination selected in step S1; on the contrary, when K>0.08, it means that the requirements are not met, and a new perforation parameter combination needs to be selected for recalculation.

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