A perforation optimization method for deep shale horizontal well multi-cluster fracture synchronous initiation

Abstract

The application discloses a perforation optimization method for synchronous initiation of multiple clusters of fractures of a deep shale horizontal well, and comprises the following steps: calculating Young's modulus and Poisson's ratio at positions of each cluster of perforations according to logging parameters of a target horizontal well; calculating a formation stress field and rock tensile strength at the positions of each cluster of perforations according to the Young's modulus and Poisson's ratio at the positions of each cluster of perforations and reservoir geologic parameters of the target horizontal well; calculating fracturing pressure at the positions of each cluster of perforations according to a pore pressure calculation formula and a fracturing pressure calculation formula; calculating fracturing fluid flow rate distributed to each cluster of fractures during fracturing according to a horizontal well fracturing multiple cluster of fractures flow distribution equation; calculating original hole friction at the positions of each cluster of perforations by using a hole friction equation; and optimizing the number of perforation holes or the diameter of the perforation holes according to a synchronous initiation perforation parameter optimization model. The application can quickly and accurately calculate perforation process parameters for synchronous initiation of multiple clusters of fractures according to fracturing site construction parameters.

Description

Technical Field

[0001] This invention relates to a perforation optimization method for synchronous fracturing of multiple clusters of fractures in deep shale horizontal wells, belonging to the field of shale gas development technology. Background Technology

[0002] In recent years, with the widespread application of horizontal well segmented and clustered fracturing technology, commercial and efficient development of shallow and medium-depth shale gas has been gradually achieved both domestically and internationally. However, more than 60% of shale gas resources are buried in deep formations below 3500m. Compared to shallow and medium-depth formations, deep shale gas formations have complex geological structures, rapid changes in geostress, and significant differences in fracture pressure among different clusters. This results in different fracture initiation times, preventing simultaneous fracture initiation and leading to greater differences in fracture extension rates after initiation, resulting in greater non-uniformity and hindering efficient shale gas extraction.

[0003] Current research on fracture initiation and propagation mainly focuses on conventional shallow and medium-depth shale gas, with limited research on deep shale gas. Simultaneous studies on fracture initiation often neglect changes in geostress. Therefore, there is an urgent need to establish an optimized perforation method for simultaneous initiation of multiple fracture clusters in deep shale horizontal wells. This method should fully consider the different fracture pressures caused by changes in geostress, establish an optimized perforation parameter model for simultaneous initiation, and quickly and accurately calculate the perforation process parameters for simultaneous initiation of multiple fracture clusters based on on-site fracturing parameters. This would avoid non-uniform propagation of individual fracture clusters and lay a theoretical foundation for optimized fracturing design in deep shale gas. Summary of the Invention

[0004] In order to overcome the defects in the existing technology, the present invention aims to provide a perforation optimization method for simultaneous fracture initiation of multiple fracture clusters in deep shale horizontal wells.

[0005] The technical solution provided by this invention to solve the above-mentioned technical problems is: a perforation optimization method for simultaneous fracture initiation in multi-cluster fractures in deep shale horizontal wells, comprising:

[0006] Step S1: Calculate the Young's modulus and Poisson's ratio at each cluster perforation location based on the logging parameters of the target horizontal well;

[0007] Step S2: Calculate the formation stress field and rock tensile strength at each cluster perforation location based on Young's modulus and Poisson's ratio at each cluster perforation location and the geological parameters of the target horizontal well reservoir;

[0008] Step S3: Calculate the rupture pressure at each cluster perforation location according to the pore pressure calculation formula and the rupture pressure calculation formula;

[0009] Step S4: Calculate the fracturing fluid flow rate of each cluster of fractures during the fracturing process based on the multi-cluster fracture flow rate distribution equation of horizontal well fracturing.

[0010] Step S5: Calculate the original aperture friction at each cluster firing aperture location using the aperture friction equation.

[0011] Step S6: Optimize the number or diameter of perforations based on the synchronous fracturing perforation parameter optimization model.

[0012] A further technical solution is that the calculation formula in step S1 is:

[0013]

[0014]

[0015]

[0016] In the formula: E i Let ν be the Young's modulus at the location of the i-th cluster of crack perforations, which is dimensionless; i Δt is the Poisson's ratio at the location of the i-th cluster of fracture perforations, dimensionless; c,i Δt represents the P-wave time difference at the location of the i-th cluster of fracture perforations, in μs / m; s,i ρ represents the transverse wave time difference at the location of the i-th cluster of fracture perforations, in μs / m; b,i The density of the formation at the location of the i-th fracture perforation cluster is expressed in g / cm³. 3 μ i , is the Poisson's ratio correction value for the perforation location of the i-th fracture cluster, dimensionless; i represents the cluster number of each fracture.

[0017] A further technical solution is that the formation stress field includes the formation vertical stress, the minimum horizontal principal stress, and the maximum horizontal principal stress.

[0018] A further technical solution is that the calculation formula in step S2 includes:

[0019] Formula for calculating vertical stress in formations:

[0020]

[0021] In the formula: σ v,i Let h be the vertical stress of the formation at the location of the i-th fracture perforation cluster, in MPa; i ρ represents the vertical depth of the formation at the location of the perforation of the i-th fracture cluster, in meters. b,i The density of the formation at the location of the i-th fracture perforation cluster is expressed in g / cm³. 3 ;

[0022] Formula for calculating minimum horizontal principal stress:

[0023]

[0024] in:

[0025]

[0026] In the formula: σ hmin,i The minimum horizontal principal stress at the location of the i-th fracture perforation cluster is given in MPa; Δt i Let k be the acoustic transit time at the location of the perforation in the i-th cluster of cracks, in μs / m; i Let m and μ be intermediate parameters of the i-th cluster of fracture perforations. i is the Poisson's ratio correction value for the location of the i-th cluster of crack perforations, which is dimensionless;

[0027] The formula for calculating the maximum horizontal principal stress is:

[0028]

[0029] In the formula: σ hmax,i The maximum horizontal principal stress in the formation at the location of the i-th fracture perforation cluster is expressed in MPa.

[0030] The formula for calculating the tensile strength of rock at each cluster perforation location is as follows:

[0031]

[0032] In the formula: σ t,i V represents the tensile strength of the formation rock at the location of the i-th fracture perforation, in MPa; cl,i E represents the clay content (%) in the formation at the location of the i-th fracture perforation cluster. i Let be the Young's modulus at the location of the i-th cluster of crack perforations, which is dimensionless.

[0033] A further technical solution is that the formula for calculating pore pressure in step S3 is:

[0034] P p,i =1.0×10 -6 ρ L ·g·h i

[0035] In the formula: P p,i ρ is the pore fluid pressure in the formation at the location of the i-th fracture perforation, in MPa; L Approximate density of water, kg / m³ 3 g is the acceleration due to gravity, in m / s². 2 h i Let the vertical depth of the formation at the location of the perforation of the i-th fracture cluster be m;

[0036] The formula for calculating the rupture pressure is:

[0037] P F,i =3σ hmin,i -σ hmax,i +σ t -αP p,i

[0038] In the formula: σ hmax,i σ represents the maximum horizontal principal stress in the formation at the location of the i-th fracture perforation cluster, in MPa; hmin,i P represents the minimum horizontal principal stress in the formation at the location of the i-th fracture perforation cluster, in MPa; p,i σ is the pore fluid pressure in the formation at the location of the i-th fracture perforation, in MPa; t For tensile strength, MPa; P F,i Let be the rupture pressure at the perforation location of the i-th cluster of fractures, in MPa; α is the porosity elastic constant, taken as 1, dimensionless.

[0039] A further technical solution is that the friction equation of the aperture is:

[0040]

[0041] In the formula: Δp pf,i n is the frictional pressure drop at the perforation aperture of the i-th cluster of fractures, in MPa; pf,i d represents the number of apertures in the i-th cluster; pf,i Let α be the diameter of the aperture of the i-th cluster, in meters; pf ρ is the orifice flow rate coefficient, taken as 0.8–0.85, dimensionless; ρ is the fracturing fluid density, kg / m³. 3 .

[0042] A further technical solution is that the optimization model for the synchronous fracturing perforation parameters is as follows:

[0043]

[0044] In the formula: P k,i S represents the inlet fracture pressure at the perforation location of the i-th cluster of fractures, in MPa; a,b Δp is the crack initiation coefficient. pf,i P is the frictional pressure drop at the perforation aperture of the i-th cluster of fractures, in MPa; F,i P represents the fracture pressure at the perforation location of the i-th cluster of fractures, in MPa; k,a P is the inlet fracture pressure at the perforation location of the a-th fracture cluster, in MPa; k,b Let be the inlet rupture pressure at the location of the b-th fracture perforation cluster, in MPa; a and b are the number of fracture perforation clusters, respectively.

[0045] A further technical solution is that the specific process of step S6 is as follows:

[0046] Step S61: Calculate the original orifice inlet rupture pressure of each cluster perforation based on the original orifice friction at each cluster perforation location and the synchronous fracturing perforation parameter optimization model.

[0047] Step S62: Sort the original orifice inlet rupture pressures of each cluster of perforations, and determine the original perforation parameters of the perforation corresponding to the original orifice inlet rupture pressure of the middle one as a constant value.

[0048] Step S63: Then, based on the synchronous fracturing perforation parameter optimization model, determine the number of orifices or the orifice diameter of other cluster perforations respectively.

[0049] A further technical solution is that, in step S63, when determining the number of perforations of other cluster perforations, the original perforation diameter of each cluster perforation is a constant value. Then, the perforation friction is adjusted by optimizing the number of perforations, the crack initiation coefficient is calculated, and the crack initiation coefficient meets the given error range.

[0050] A further technical solution is that, in step S63, when determining the aperture diameter of other clustered firing holes, the number of apertures of each clustered firing hole is a constant value. Then, the aperture friction is adjusted by optimizing the aperture diameter, the crack initiation coefficient is calculated, and the crack initiation coefficient meets the given error range. The aperture diameter is selected according to the type of perforating projectile.

[0051] This invention has the following beneficial effects: Addressing the problem that in deep shale gas horizontal wells, the formation stress conditions at different locations within the well section vary significantly during fracturing, leading to the inability of fractures at different perforation clusters to initiate synchronously, this invention establishes a perforation parameter optimization model for synchronous fracturing in deep shale horizontal wells. This results in a perforation optimization method for synchronous fracturing of multiple fracture clusters, which can quickly and accurately calculate the perforation process parameters for synchronous fracturing of multiple fracture clusters based on the on-site fracturing parameters. Attached Figure Description

[0052] Figure 1 This is a flowchart of the calculation process of the method of the present invention;

[0053] Figure 2 This is a graph showing the calculation results of optimizing the number of perforations in each cluster of the target well in the example embodiment;

[0054] Figure 3 This is a graph showing the calculation results of the optimized perforation diameter of each cluster perforation in the target well of the embodiment;

[0055] Figure 4 This is a heat map of the fracturing coefficient for optimizing the number of perforations in the target well in the example embodiment;

[0056] Figure 5 This is a heat map of the fracture initiation coefficient for optimizing the perforation diameter of the target well in the embodiment. Detailed Implementation

[0057] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0058] like Figure 1 As shown, the present invention provides an optimized perforation method for simultaneous fracture initiation in multiple clusters of fractures in deep shale horizontal wells, comprising the following steps:

[0059] Step S1: Calculate the Young's modulus and Poisson's ratio at each cluster perforation location based on the logging parameters of the target horizontal well (formation density, shear wave transit time, longitudinal wave transit time, sonic transit time, clay content);

[0060]

[0061]

[0062]

[0063] In the formula: E i Let ν be the Young's modulus at the location of the i-th cluster of crack perforations, which is dimensionless; i Δt represents the Poisson's ratio of the formation at the location of the perforation of the i-th fracture cluster, which is dimensionless; c,i Δt represents the P-wave time difference at the location of the i-th cluster of fracture perforations, in μs / m; s,i ρ represents the transverse wave time difference at the location of the i-th cluster of fracture perforations, in μs / m; b,i The density of the formation at the location of the i-th fracture perforation cluster is expressed in g / cm³. 3 μ i , is the Poisson's ratio correction value for the perforation location of the i-th fracture cluster, dimensionless; subscript: i indicates the cluster number of each fracture cluster.

[0064] Step S2: Calculate the vertical stress, minimum horizontal principal stress, maximum horizontal principal stress, and rock tensile strength at each cluster perforation location based on Young's modulus and Poisson's ratio at each cluster perforation location and the geological parameters (formation depth) of the target horizontal well reservoir.

[0065] Formula for calculating vertical stress:

[0066]

[0067] In the formula: σ v,i Let h be the vertical stress of the formation at the location of the i-th fracture perforation cluster, in MPa; i Let the vertical depth of the formation at the location of the perforation of the i-th fracture cluster be m;

[0068] The formula for calculating the minimum horizontal principal stress is:

[0069]

[0070] in:

[0071]

[0072] In the formula: σ hmin,i The minimum horizontal principal stress at the location of the i-th fracture perforation cluster is given in MPa; Δt i denoted as the acoustic transit time at the location of the perforation in the i-th cluster of cracks, in μs / m; k is an intermediate parameter, in m.

[0073] The formula for calculating the maximum horizontal principal stress is:

[0074]

[0075] In the formula: σ hmax,i The maximum horizontal principal stress in the formation at the location of the i-th fracture perforation cluster is expressed in MPa.

[0076] The formula for calculating the tensile strength of rock at each cluster perforation location is as follows:

[0077]

[0078] In the formula: σ t,i V represents the tensile strength of the formation rock at the location of the i-th fracture perforation, in MPa; cl,i , where is the clay content (%) in the stratum at the location of the i-th fracture perforation cluster;

[0079] Step S3: Calculate the rupture pressure at each cluster perforation location according to the pore pressure calculation formula and the rupture pressure calculation formula;

[0080] The formula for calculating the burst pressure at each cluster perforation location is as follows:

[0081] P p,i =1.0×10 -6 ρ L ·g·h i (9)

[0082] P F,i =3σ hmin,i -σ hmax,i +σ t -αP p,i (10)

[0083] In the formula: P p,i ρ is the pore fluid pressure in the formation at the location of the i-th fracture perforation, in MPa; L Approximate density of water, kg / m³ 3 g is the acceleration due to gravity, in m / s². 2 ;P F,idenoted as the rupture pressure at the perforation location of the i-th cluster of fractures, in MPa; α is the porosity elastic constant, typically taken as 1, dimensionless.

[0084] Step S4: Collect the target horizontal well fracturing parameters (fracturing flow rate, fracturing fluid density) and original perforation parameters (number of clusters, number of perforations, perforation diameter, and perforation flow coefficient). Calculate the fracturing fluid flow rate allocated to each cluster of fractures during the fracturing process based on the multi-cluster fracture flow distribution equation for horizontal well fracturing.

[0085] The perforation flow distribution equation is:

[0086]

[0087] In the formula: q i Let m be the total flow rate of the i-th cluster of fracture perforations. 3 / s;N w为 Total number of horizontal well clusters; Q total The total fracturing flow rate is m 3 / s;

[0088] Step S5: Calculate the original aperture friction at each cluster firing aperture location using the aperture friction equation.

[0089] The formula for calculating the friction of the orifice is:

[0090]

[0091] In the formula: Δp pf,i n is the frictional pressure drop at the perforation aperture of the i-th cluster of fractures, in MPa; pf d represents the number of apertures in the i-th cluster; pf Let α be the diameter of the aperture of the i-th cluster, in meters; pf ρ is the orifice flow rate coefficient, typically taken as 0.8–0.85, dimensionless; ρ is the fracturing fluid density, kg / m³. 3 ;

[0092] Step S6: Calculate the original orifice inlet rupture pressure of each cluster perforation based on the original orifice friction at each cluster perforation location and the synchronous fracturing perforation parameter optimization model.

[0093] The optimization model for synchronous fracturing perforation parameters is as follows:

[0094]

[0095] In the formula: P k,i S represents the inlet fracture pressure at the perforation location of the i-th cluster of fractures, in MPa; a,b Let S be the crack initiation coefficient. a,b When the value is between 0.98 and 1.02, it is considered that the crack clusters a and b can achieve synchronous crack initiation, which is dimensionless.

[0096] Step S7: Sort the original inlet rupture pressures of each cluster of perforations and determine the original perforation parameters of the perforation corresponding to the middle original inlet rupture pressure as a constant value.

[0097] Step S8: Then, based on the synchronous fracturing perforation parameter optimization model, determine the number or diameter of other cluster perforations respectively;

[0098] When determining the number of perforations for other cluster perforations, the original perforation diameter of each cluster perforation is a constant value. Then, the perforation friction is adjusted by optimizing the number of perforations, the crack initiation coefficient is calculated, and the crack initiation coefficient is made to meet the given error range.

[0099] When determining the orifice diameter of other cluster perforations, the number of perforations in each cluster perforation is a constant value. Then, the orifice friction is adjusted by optimizing the orifice diameter, the crack initiation coefficient is calculated, and the crack initiation coefficient is made to meet the given error range. The orifice diameter is selected according to the perforation projectile model, and different orifice diameters are selected (as shown in Table 1).

[0100] Table 1 Correspondence between Perforation Projectile Types and Orifice Diameters

[0101]

[0102]

[0103] Example

[0104] The geophysical test data of the target horizontal well in a certain shale gas reservoir area are shown in Table 2; the fracturing and perforation data are shown in Table 3.

[0105] Table 2 Geophysical test data of target horizontal wells in a deep shale gas reservoir area

[0106]

[0107] Table 3. Fracturing data of target horizontal wells in a deep shale gas reservoir area.

[0108]

[0109] The specific implementation is as follows:

[0110] First, based on the geophysical test data of the target horizontal well, the Young's modulus of the formation at each cluster perforation location is calculated using equation (1); the Poisson's ratio of the formation at each cluster perforation location is calculated using equation (2), and the Poisson's ratio is corrected using equation (3).

[0111] Subsequently, based on the calculated Young's modulus and Poisson's ratio of the strata at the location of the i-th cluster perforation, the vertical stress, maximum horizontal principal stress and minimum horizontal principal stress of the strata at each cluster perforation location are calculated using equations (4) to (7); the tensile strength of the strata at each cluster perforation location is calculated using equation (8).

[0112] Subsequently, based on the formation stress field distribution, the fracturing pressure at each cluster perforation location was calculated using equations (9) to (10); and the fracturing fluid flow rate of each cluster fracture was calculated using equation (11).

[0113] Subsequently, the original aperture friction at each cluster firing position was calculated using equation (12);

[0114] Using equation (13), the original orifice inlet rupture pressure at each cluster firing orifice location is calculated (as shown in Table 4).

[0115] The original orifice inlet rupture pressures of the seven clusters were sorted, and the original orifice inlet rupture pressure of cluster No. 3 was determined as the median value. Thus, the perforation parameters of cluster No. 3 were determined as constant values, namely, the orifice diameter was 9.5 mm and the number of perforations was 6.

[0116] Then, the perforation friction is adjusted by optimizing the number or diameter of perforations in other clusters, and the crack initiation coefficient between each cluster is calculated so that the crack initiation coefficient meets the given error range.

[0117] That is, using, such as Figure 1 The flowchart of the calculation process of the present invention shown is used to perform example calculations, and based on the calculation results, output the following tables: perforation number optimization result table (as shown in Table 5), perforation number optimization crack initiation coefficient table (as shown in Table 6), perforation diameter optimization result table (as shown in Table 7), and perforation diameter optimization crack initiation coefficient table (as shown in Table 8). Heat maps of the perforation number optimization crack initiation coefficient are also plotted (e.g., ...). Figure 4 (As shown), a hotspot diagram of the crack initiation coefficient for optimized perforation hole diameter (as shown) Figure 5 (As shown).

[0118] Table 4 Original Data Table

[0119]

[0120] Table 5 Optimization of the Number of Perforations

[0121]

[0122]

[0123] Table 6. Optimization of Crack Initiation Coefficient for Perforation Hole Quantity

[0124] Cluster 1 1.0000 0.9877 0.9918 0.9889 0.9919 0.9837 0.9910 Cluster 2 1.0000 1.0041 1.0013 1.0043 0.9959 1.0034 Cluster 3 1.0000 0.9972 1.0001 0.9919 0.9993 Cluster 4 1.0000 1.0030 0.9947 1.0021 Cluster 5 1.0000 0.9917 0.9991 Cluster 6 1.0000 1.0075 Cluster 7 1.0000

[0125] Table 7 Optimization of Perforation Hole Diameter

[0126]

[0127]

[0128] Table 8. Optimized Crack Initiation Coefficient for Perforation Hole Diameter

[0129] Cluster 1 1.0000 1.0141 1.0074 1.0045 1.0075 1.0048 1.0134 Cluster 2 1.0000 0.9934 0.9905 0.9935 0.9908 0.9993 Cluster 3 1.0000 0.9972 1.0001 0.9974 1.0060 Cluster 4 1.0000 1.0030 1.0002 1.0088 Cluster 5 1.0000 0.9973 1.0058 Cluster 6 1.0000 1.0086 Cluster 7 1.0000

[0130] The above description is not intended to limit the present invention in any way. 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 art can make some changes or modifications to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the present invention shall still fall within the scope of the present invention.

Claims

1. A perforation optimization method for simultaneous fracture initiation in multiple clusters of fractures in deep shale horizontal wells, characterized in that, include: Step S1: Calculate the Young's modulus and Poisson's ratio at each cluster perforation location based on the logging parameters of the target horizontal well; Step S2: Calculate the formation stress field and rock tensile strength at each cluster perforation location based on Young's modulus and Poisson's ratio at each cluster perforation location and the geological parameters of the target horizontal well reservoir; Step S3: Calculate the rupture pressure at each cluster perforation location according to the pore pressure calculation formula and the rupture pressure calculation formula; The formula for calculating pore pressure is as follows: In the formula: P p,i For the first i Pore ​​fluid pressure in the formation at the location of cluster fracture perforations, MPa; ρ L Approximate density of water, kg / m³ 3 ; g The acceleration due to gravity is m / s². 2 ; h i For the first i Cluster fracture perforation location, vertical depth of formation, m; The formula for calculating the rupture pressure is: In the formula: σ hmax,i For the first i Maximum horizontal principal stress in the formation at the location of cluster fracture perforations, MPa; σ hmin,i For the first i Minimum horizontal principal stress in the formation at the location of cluster fracture perforations, MPa; P p,i For the first i Pore ​​fluid pressure in the formation at the location of cluster fracture perforations, MPa; σ t Tensile strength, MPa; P F,i For the first i The fracture pressure at the location of the cluster fracture perforation, in MPa; α is the porosity elastic constant, taken as 1, which is dimensionless; Step S4: Calculate the fracturing fluid flow rate of each cluster of fractures during the fracturing process based on the multi-cluster fracture flow rate distribution equation of horizontal well fracturing. The perforation flow distribution equation is: In the formula: q i For the first i Total flow rate of clustered fracture perforation holes, m 3 / s; N w This represents the total number of clusters in the horizontal wells. Q total The total fracturing flow rate is m 3 / s; Step S5: Calculate the original aperture friction at each cluster firing aperture location using the aperture friction equation. The equation for the friction of the orifice is: In the formula: Δ p pf,i For the first i Frictional pressure drop at the perforation aperture of the cluster fracture, MPa; n pf,i For the first i Number of cluster apertures; d pf,i For the first i Cluster aperture diameter, in meters; α pf The orifice flow coefficient is taken as 0.8~0.85 and is dimensionless. ρ The density of the fracturing fluid is kg / m³. 3 ; q i For the first i Total flow rate of clustered fracture perforation holes, m 3 / s; Step S6: Optimize the number or diameter of perforations based on the synchronous fracturing perforation parameter optimization model; The optimization model for the synchronous fracturing perforation parameters is as follows: In the formula: P k,i For the first i The inlet fracture pressure at the perforation location of the cluster fracture, in MPa; S a,b This is the crack initiation coefficient; Δ p pf,i For the first i Frictional pressure drop at the perforation aperture of the cluster fracture, MPa; P F,i For the first i The fracture pressure at the location of the cluster fracture perforation, in MPa; P k,a For the first a The inlet fracture pressure at the perforation location of the cluster fracture, in MPa; P k,b For the first b The inlet fracture pressure at the perforation location of the cluster fracture, in MPa; a , b These represent the number of perforation clusters in the fracture.

2. The perforation optimization method for simultaneous fracture initiation in multiple clusters of fractures in a deep shale horizontal well according to claim 1, characterized in that, The calculation formula in step S1 is: In the formula: E i For the first i Young's modulus at the location of the cluster crack perforation is dimensionless. ν i For the first i Poisson's ratio at the location of the cluster fracture perforation is dimensionless. Δ t c,i For the first i P-wave time difference at cluster fracture perforation location, μs / m; Δ t s,i For the first i Shear wave time difference at cluster fracture perforation location, μs / m; ρ b,i For the first i Formation density at the location of cluster fracture perforations, g / cm³ 3 ; μ i For the first i Poisson's ratio correction for cluster fracture perforation location, dimensionless; i This indicates the number of each cluster of cracks.

3. The perforation optimization method for simultaneous fracture initiation in multiple clusters of fractures in deep shale horizontal wells according to claim 1, characterized in that, The formation stress field includes the formation vertical stress, minimum horizontal principal stress, and maximum horizontal principal stress.

4. The perforation optimization method for simultaneous fracture initiation in multiple clusters of fractures in deep shale horizontal wells according to claim 3, characterized in that, The calculation formula in step S2 includes: Formula for calculating vertical stress in formations: In the formula: σ v,i For the first i Vertical stress in the formation at the location of cluster fracture perforations, MPa; h i For the first i Cluster fracture perforation location, vertical depth of formation, m; ρ b,i For the first i Formation density at the location of cluster fracture perforations, g / cm³ 3 ; Formula for calculating minimum horizontal principal stress: in: In the formula: σ hmin,i For the first i Minimum horizontal principal stress at cluster fracture perforation location, MPa; Δ t i For the first i Acoustic transit time at cluster fracture perforation location, μs / m; k i For the first i Intermediate parameters of clustered fracture perforations, m; μ i For the first i Poisson's ratio correction for cluster fracture perforation location, dimensionless; The formula for calculating the maximum horizontal principal stress is: In the formula: σ hmax,i For the first i Maximum horizontal principal stress in the formation at the location of cluster fracture perforations, MPa; The formula for calculating the tensile strength of rock at each cluster perforation location is as follows: In the formula: σ t,i For the first i Tensile strength of the formation rock at the location of the cluster fracture perforation, MPa; V cl,i For the first i Clay content in the formation at the location of cluster fracture perforations, % E i For the first i The Young's modulus at the location of the cluster crack perforation is dimensionless.

5. The perforation optimization method for simultaneous fracture initiation in multiple clusters of fractures in a deep shale horizontal well according to claim 1, characterized in that, The specific process of step S6 is as follows: Step S61: Calculate the original orifice inlet rupture pressure of each cluster perforation based on the original orifice friction at each cluster perforation location and the synchronous fracturing perforation parameter optimization model. Step S62: Sort the original orifice inlet rupture pressures of each cluster of perforations, and determine the original perforation parameters of the perforation corresponding to the original orifice inlet rupture pressure of the middle one as a constant value. Step S63: Then, based on the synchronous fracturing perforation parameter optimization model, determine the number of orifices or the orifice diameter of other cluster perforations respectively.

6. The perforation optimization method for simultaneous fracture initiation in multiple clusters of fractures in a deep shale horizontal well according to claim 5, characterized in that, In step S63, when determining the number of perforations for other cluster perforations, the original perforation diameter of each cluster perforation is a constant value. Then, the perforation friction is adjusted by optimizing the number of perforations, the crack initiation coefficient is calculated, and the crack initiation coefficient is made to meet the given error range.

7. The perforation optimization method for simultaneous fracture initiation in multiple clusters of fractures in a deep shale horizontal well according to claim 5, characterized in that, In step S63, when determining the orifice diameter of other clustered firing holes, the number of perforations in each clustered firing hole is a constant value. Then, the orifice friction is adjusted by optimizing the orifice diameter, the crack initiation coefficient is calculated, and the crack initiation coefficient is made to meet the given error range. The orifice diameter is selected according to the type of perforating projectile.

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