Vertical well multi-branch fracture fracturing sand adding step optimization method

Abstract

The invention discloses a vertical well multi-branch seam fracturing sand adding step optimization method, and relates to the technical field of oil production engineering. The problems that according to an existing method, the sand adding scale design is not accurate, and the sand adding step before temporary plugging and after temporary plugging of all stages is not accurate are mainly solved. The method comprises the steps that a well suitable for the vertical well multi-branch-joint fracturing technology is selected, and the distance from a crack initiation point of each group of branch joints to a shaft, the crack initiation angle and the steering radius in a digital-analog test are obtained; optimizing fracture parameters of the main fracture of the fractured interval; according to the optimized fracture parameters of the main fracture, the distance between the fracture initiation point of each group of branch fractures of the fractured interval and a shaft, the fracture initiation angle and the steering radius are obtained; optimizing fracture parameters of each group of branch fractures of the fractured interval; the sand adding scale of the fractured interval is optimized; drawing a fracture system form; and optimizing a fracturing interval and adding sand. According to the vertical well multi-branch fracture fracturing sand adding step optimization method, the sand adding scale design is accurate, the sand adding steps before temporary plugging and after temporary plugging of all stages are accurate, and optimal matching of fracture parameters, the sand adding scale, the sand adding steps and a reservoir can be achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil extraction engineering, and particularly relates to a straight well multi-branch fracture fracturing sand adding step optimization method. BACKGROUND

[0002] The straight well multi-branch fracture fracturing technology, the in-fracture temporary plugging and diverting fracturing technology, the straight well artificial fracture and closely cut stratum fracturing technology, and the sand adding step optimization currently have no related research. The support agent dosage of each step before the in-fracture temporary plugging and after the temporary plugging of each level lacks a theoretical basis, and is mainly optimized according to the experience of a fracturing engineer. It is difficult to realize the best matching of the fracture system, the sand adding scale, the sand adding step and the reservoir, resulting in that the support fracture length and the flow conductivity of the main fracture and each level of branch fracture do not match the design, and further affecting the fracturing effect and economic benefits. SUMMARY

[0003] The present application is aimed at the problems of the inaccurate sand adding scale design and the inaccurate sand adding step before the temporary plugging and after the temporary plugging of each level in the existing method in the background technology, and provides a straight well multi-branch fracture fracturing sand adding step optimization method. The straight well multi-branch fracture fracturing sand adding step optimization method has accurate sand adding scale design and accurate sand adding step before the temporary plugging and after the temporary plugging of each level, and can realize the best matching of the fracture parameter, the sand adding scale, the sand adding step and the reservoir.

[0004] The present application solves the problems and can be achieved through the following technical scheme. The straight well multi-branch fracture fracturing sand adding step optimization method comprises the following steps.

[0005] S1: obtaining the three-dimensional stress of a fracturing interval, and judging whether the fracture of the fracturing interval is a vertical fracture;

[0006] S2: judging the applicability of the straight well multi-branch fracture fracturing technology based on the obtained three-dimensional stress of the fracturing interval and the determination of the vertical fracture;

[0007] S3: obtaining the distance from each group of branch fracture initiation point to the wellbore, the initiation angle and the diverting radius of the numerical simulation test for the well suitable for the straight well multi-branch fracture fracturing technology;

[0008] S4: optimizing the fracture parameter of the main fracture of the fracturing interval, and obtaining the distance from each group of branch fracture initiation point to the wellbore, the initiation angle and the diverting radius of the fracturing interval;

[0009] S5: optimizing the fracture parameter of each group of branch fracture of the fracturing interval;

[0010] S6: optimizing the sand adding scale of the fracturing interval based on the optimized fracture parameter of each group of branch fracture of the fracturing interval;

[0011] S7: drawing the fracture system morphology, and optimizing the sand adding step of the fracturing interval.

[0012] The present application can have the following beneficial effects compared with the above background art:

[0013] The present application provides a calculation method of the distance from the initiation point of each branch fracture of the fractured interval to the wellbore, the initiation angle and the turning radius, a calculation method of the fracture parameters of each branch fracture, and a calculation method of the sanding step number and the proppant dosage of each step, solves the problems in the previous design method that the parameters such as the distance from the initiation point of the second and subsequent branch fractures to the wellbore, the initiation angle and the turning radius are inaccurate, the fracture parameters of the second and subsequent branch fractures are the same as those of the first group of branch fractures, the sanding scale design is not accurate, and the proppant dosage optimization of each step lacks theoretical basis, and truly realizes the best matching of the fracture system, the sanding scale and the sanding step with the reservoir; meanwhile, the method is practical, safe and effective. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 is a branch fracture group number and production relationship chart in the embodiment of the present application;

[0015] Figure 2 is a fracture system morphology drawn in the embodiment of the present application. DETAILED DESCRIPTION

[0016] To make the purpose, technical scheme and advantages of the present application clearer, the embodiments of the present application will be further described in detail below with reference to the drawings.

[0017] The present application is a straight well multi-branch fracture sanding step optimization method, comprising the following steps:

[0018] S1: obtaining the three-directional stresses of the fractured interval; determining whether the fractures of the fractured interval are vertical fractures;

[0019] The three-directional stresses of the fractured interval are the minimum horizontal principal stress, the maximum horizontal principal stress and the vertical stress of the fractured interval; the method for obtaining the three-directional stresses of the fractured interval is:

[0020] (11) if there are experimental data of the in-situ stress test of the fractured interval, the experimental data is preferentially selected as the three-directional stresses of the fractured interval;

[0021] (12) if there are no experimental data of the in-situ stress test of the fractured interval, but there are X-mac logging interpretation results, the X-mac logging interpretation results are preferentially selected as the three-directional stresses of the fractured interval;

[0022] (13) if there are no experimental data of the in-situ stress test and X-mac logging interpretation results of the fractured interval, only the conventional logging interpretation results are selected as the three-directional stresses of the fractured interval.

[0023] The method for determining whether the fractures of the fractured interval are vertical fractures is:

[0024] (a) the minimum horizontal principal stress < the maximum horizontal principal stress < the vertical stress, judging the crack as a vertical crack;

[0025] (b) the minimum horizontal principal stress < the vertical stress < the maximum horizontal principal stress, judging the crack as a vertical crack.

[0026] S2: judging the applicability of the straight well multi-branch crack fracturing technology based on the obtained three-directional stresses of the fracturing interval and the determination of the vertical crack; the specific method is:

[0027] if the crack is a vertical crack and the horizontal stress difference of the fracturing interval is less than or equal to 6 MPa, judging that the straight well multi-branch crack fracturing technology is applicable.

[0028] The horizontal stress difference of the fracturing interval is the value of the maximum horizontal principal stress minus the minimum horizontal principal stress.

[0029] S3: for the well to which the straight well multi-branch crack fracturing technology is applicable, obtaining the distance from the branch crack initiation point to the wellbore, the initiation angle and the steering radius of each group of branch cracks in the numerical simulation test; the specific method comprises the following steps: obtaining the first to fifth groups of branch cracks in the numerical simulation test.

[0030] (31) obtaining the distance L1 from the first group of branch crack initiation points to the wellbore, the first group of branch crack initiation angle A1 and the first group of branch crack steering radius r1 in the numerical simulation test:

[0031] L1 = -0.0321x + 14.511x + 6.9, wherein L1 is the distance from the first group of branch crack initiation points to the wellbore, in meters, x is the horizontal stress difference, in MPa; 2

[0032] A1 = -0.3452x - 9.75x + 86.738, wherein A1 is the first group of branch crack initiation angle, in °, x is the horizontal stress difference, in MPa; 2

[0033] r1 = 1.655x - 25.967x + 104.84, wherein r1 is the first group of branch crack steering radius, in meters, x is the horizontal stress difference, in MPa; 2

[0034] (32) obtaining the distance L2 from the second group of branch crack initiation points to the wellbore, the second group of branch crack initiation angle A2 and the second group of branch crack steering radius r2 in the numerical simulation test:

[0035] L2 = 0.7405x + 6.5357x + 5.9667, wherein L2 is the distance from the second group of branch crack initiation points to the wellbore, in meters, x is the horizontal stress difference, in MPa; 2 ​​​​

[0036] A2 = -0.619x 2 -6.7143x + 87.762, where A2 is the second group branch slot initiation angle, in °, and x is the horizontal stress difference, in MPa;

[0037] r2 = 1.6783x 2 -27.276x + 114.25, where r2 is the second group branch slot turning radius, in m, and x is the horizontal stress difference, in MPa;

[0038] (33) Obtain the third group branch slot initiation point distance from the wellbore distance L3, the third group branch slot initiation angle A3, and the third group branch slot turning radius r3 in the numerical simulation experiment:

[0039] L3 = 0.6417x 2 + 4.9536x + 0.2976, where L3 is the third group branch slot initiation point distance from the wellbore, in m, and x is the horizontal stress difference, in MPa;

[0040] A3 = -1.2262x 2 - 2.6789x + 89.405, where A3 is the third group branch slot initiation angle, in °, and x is the horizontal stress difference, in MPa;

[0041] r3 = 1.6084x 2 - 27.386x + 119.58, where r3 is the third group branch slot turning radius, in m, and x is the horizontal stress difference, in MPa;

[0042] (34) Obtain the fourth group branch slot initiation point distance from the wellbore distance L4, the fourth group branch slot initiation angle A4, and the fourth group branch slot turning radius r4 in the numerical simulation experiment:

[0043] L4 = 0.906x 2 + 1.175x - 0.7881, where L4 is the fourth group branch slot initiation point distance from the wellbore, in m, and x is the horizontal stress difference, in MPa;

[0044] A4 = -1.6548x 2 + 0.8071x + 88.548, where A4 is the fourth group branch slot initiation angle, in °, and x is the horizontal stress difference, in MPa;

[0045] r4 = 1.4755x 2 - 27.065x + 124.42, where r4 is the fourth group branch slot turning radius, in m, and x is the horizontal stress difference, in MPa;

[0046] (35) acquiring the distance between the fifth group of branch fractures and the wellbore L5, the fifth group of branch fractures initiation angle A5, and the fifth group of branch fractures turning radius r5:

[0047] L5 = 0.9012x 2 -12107x-0.1119, wherein L5 is the distance between the fifth group of branch fractures and the wellbore, in meters, x is the horizontal stress difference, in MPa;

[0048] A5 = -1.8571x 2 +3.0357x+87.697, wherein A5 is the fifth group of branch fractures initiation angle, in °, x is the horizontal stress difference, in MPa;

[0049] r5 = 1.3427x 2 -26.744x+129.25, wherein r5 is the fifth group of branch fractures turning radius, in meters, x is the horizontal stress difference, in MPa.

[0050] S4: optimizing the fracture parameters of the main fracture of the fracturing interval; acquiring the distance between each group of branch fractures and the wellbore, the initiation angle, and the turning radius of the branch fractures of the fracturing interval;

[0051] The method for optimizing the fracture parameters of the main fracture of the fracturing interval is:

[0052] The fracture parameters are the fracture half-length and the conductivity.

[0053] According to the reservoir characteristics of the fracturing interval, an optimization scheme for the main fracture half-length and the conductivity is prepared, and a software is applied to develop a simulation of different main fracture parameters.

[0054] According to the simulation results, a graph of the relationship between the main fracture parameters and the production is prepared, and according to the production inflection point on the graph, the optimal main fracture half-length L 主 and the conductivity D 主 are determined, wherein L 主 is in meters, and D 主 is in um 2 · cm.

[0055] The method for acquiring the distance between each group of branch fractures and the wellbore, the initiation angle, and the turning radius of the branch fractures of the fracturing interval is:

[0056] The main fracture half-length of the numerical simulation is 120 m; according to the similarity principle, the distance between the first group, the second group, the third group, the fourth group, and the fifth group of branch fractures and the wellbore, the initiation angle, and the turning radius of the branch fractures of the fracturing interval are converted in combination with the optimized main fracture half-length of the fracturing interval.

[0057] S5: optimizing the fracture parameters of each group of branch fractures of the fracturing interval; the specific method comprises the following steps:

[0058] (51) On the basis of the main fracture parameter optimization model, according to the reservoir characteristics of the fracturing interval and the distance from the first group of branch fractures to the wellbore, the crack angle, the steering radius, the first group of branch fractures length and conductivity optimization scheme is made, and the branch fracture parameter simulation is carried out according to the optimization scheme by using the software. According to the simulation results, the branch fracture parameter and production relationship chart is made, and the optimal branch fracture length L 分1 and conductivity D 分1 of the first group of branch fractures is determined according to the yield inflection point on the chart, wherein L 分1 is m, and D 分1 is um 2 .cm;

[0059] (52) On the basis of the first group of branch fractures optimization model, according to the reservoir characteristics of the fracturing interval and the distance from the second group of branch fractures to the wellbore, the crack angle, the steering radius, the second group of branch fractures length and conductivity optimization scheme is made, and the branch fracture parameter simulation is carried out according to the optimization scheme by using the software. According to the simulation results, the branch fracture parameter and production relationship chart is made, and the optimal branch fracture length L 分2 and conductivity D 分2 of the second group of branch fractures is determined according to the yield inflection point on the chart, wherein L 分2 is m, and D 分2 is um 2 .cm;

[0060] (53) On the basis of the second group of branch fractures optimization model, according to the reservoir characteristics of the fracturing interval and the distance from the third group of branch fractures to the wellbore, the crack angle, the steering radius, the third group of branch fractures length and conductivity optimization scheme is made, and the branch fracture parameter simulation is carried out according to the optimization scheme by using the software. According to the simulation results, the branch fracture parameter and production relationship chart is made, and the optimal branch fracture length L 分3 and conductivity D 分3 of the third group of branch fractures is determined according to the yield inflection point on the chart, wherein L 分3 is m, and D 分3 is um 2 .cm;

[0061] (54) On the basis of the third group of branch fractures optimization model, according to the reservoir characteristics of the fracturing interval and the distance from the fourth group of branch fractures to the wellbore, the crack angle, the steering radius, the fourth group of branch fractures length and conductivity optimization scheme is made, and the branch fracture parameter simulation is carried out according to the optimization scheme by using the software. According to the simulation results, the branch fracture parameter and production relationship chart is made, and the optimal branch fracture length L 分4 and conductivity D 分4 of the fourth group of branch fractures is determined according to the yield inflection point on the chart, wherein L 分4 is m, and D分4 unit: um 2 .cm;

[0062] (55) On the basis of the fourth group of branch fracture optimization model, according to the reservoir characteristics of the fracturing interval and the fifth group of branch fracture initiation point distance from the wellbore, the initiation angle, the steering radius, the fifth group of branch fracture length and conductivity optimization scheme is made, the software is applied to carry out branch fracture parameter simulation according to the optimization scheme, according to the simulation results, the branch fracture parameter and production relationship graph is made, according to the production inflection point on the graph, the fifth group of branch fracture optimal branch fracture length L 分5 and conductivity D 分5 is determined, wherein L 分5 unit: m, D 分5 unit: um 2 .cm;

[0063] (56) The branch fracture group number and production relationship graph is made, and the optimal branch fracture group number is determined according to the production inflection point on the graph.

[0064] S6: Based on the optimization of the fracture parameters of each group of branch fractures in the fracturing interval, the sanding scale of the fracturing interval is optimized; the specific method includes the following steps:

[0065] (61) The closure pressure of the main fracture, the first group of branch fractures, the second group of branch fractures, the third group of branch fractures, the fourth group of branch fractures and the fifth group of branch fractures is obtained:

[0066] P 闭主 = minimum horizontal principal stress, wherein P 闭主 is the closure pressure of the main fracture, which is rounded to ten digits, and the unit is MPa;

[0067] P 闭分1 =-0.0821x 2 +0.825x+0.0214+minimum horizontal principal stress, wherein P 闭分1 is the closure pressure of the first group of branch fractures, which is rounded to ten digits, and the unit is MPa, and x is the horizontal stress difference, and the unit is MPa;

[0068] P 闭分2 =-0.0702x 2 +0.85x+0.0417+minimum horizontal principal stress, wherein P 闭分2 is the closure pressure of the second group of branch fractures, which is rounded to ten digits, and the unit is MPa, and x is the horizontal stress difference, and the unit is MPa;

[0069] P 闭分3 =-0.0524x 2 +0.8571x+0.0524+minimum horizontal principal stress, wherein P 闭分3The closing pressure of the third group of branch joints is rounded to the nearest ten and is in MPa. x is the horizontal stress difference and is in MPa.

[0070] P 闭分4 = -0.0369x 2 +0.8929x+0.0512+Minimum horizontal principal stress, where P 闭分4 The closing pressure of the fourth group of branch joints is rounded to the nearest ten and is in MPa. x is the horizontal stress difference and is in MPa.

[0071] P 闭分5 = -0.0018x 2 +0.8518x+0.0607+Minimum horizontal principal stress, where P 闭分5 The closing pressure of the fifth group of branch joints is rounded to the nearest ten and is in MPa. x is the horizontal stress difference and is in MPa.

[0072] (62) Obtain the relationship between sand concentration and fracture conductivity under closure pressures of 10MPa, 20MPa, 30MPa, 40MPa, 50MPa, and 60MPa:

[0073] N 10 = 0.1706x - 2.0089, where N 10 The sand concentration is given under a closure pressure of 10 MPa, in kg / m³. 2 x represents the fracture conductivity, in μm. 2 .cm;

[0074] N 20 = 0.2438x - 1.988, where N 20 The sand concentration is given under a closure pressure of 20 MPa, in kg / m³. 2 x represents the fracture conductivity, in μm. 2 .cm;

[0075] N 30 = 0.3879x - 1.9241, where N 30 The sand concentration is given under a closure pressure of 30 MPa, in kg / m³. 2 x represents the fracture conductivity, in μm. 2 .cm;

[0076] N 40 = 0.4876x - 0.8364, where N 40 The sand concentration is given under a closure pressure of 40 MPa, in kg / m³. 2 x represents the fracture conductivity, in μm. 2.cm;

[0077] N 50 = 0.8042x - 0.3572, wherein N 50 is the sanding concentration under the condition of a closure pressure of 50 MPa, in Kg / m 2 , and x is the fracture conductivity, in um 2 .cm;

[0078] N 60 = 1.6267x - 0.0559, wherein N 60 is the sanding concentration under the condition of a closure pressure of 50 MPa, in Kg / m 2 , and x is the fracture conductivity, in um 2 .cm;

[0079] (63) obtaining the sanding concentration required for the main fracture, the first group of branch fractures, the second group of branch fractures, the third group of branch fractures, the fourth group of branch fractures, and the fifth group of branch fractures:

[0080] selecting a sanding concentration calculation formula according to the closure pressure of the main fracture, and substituting the optimized main fracture conductivity into the selected sanding concentration calculation formula to obtain the sanding concentration N 主 required for the main fracture, in Kg / m 2 ;

[0081] selecting a sanding concentration calculation formula according to the closure pressure of the first group of branch fractures, and substituting the optimized main fracture conductivity into the selected sanding concentration calculation formula to obtain the sanding concentration N 分1 required for the first group of branch fractures, in Kg / m 2 ;

[0082] selecting a sanding concentration calculation formula according to the closure pressure of the second group of branch fractures, and substituting the optimized main fracture conductivity into the selected sanding concentration calculation formula to obtain the sanding concentration N 分2 required for the second group of branch fractures, in Kg / m 2 ;

[0083] selecting a sanding concentration calculation formula according to the closure pressure of the third group of branch fractures, and substituting the optimized main fracture conductivity into the selected sanding concentration calculation formula to obtain the sanding concentration N 分3 required for the third group of branch fractures, in Kg / m 2 ;

[0084] selecting a sanding concentration calculation formula according to the closure pressure of the fourth group of branch fractures, and substituting the optimized main fracture conductivity into the selected sanding concentration calculation formula to obtain the sanding concentration N 分4 required for the fourth group of branch fractures, in Kg / m2;

[0085] According to the fifth group branch joint closure pressure selection sanding concentration calculation formula, the optimized main joint conductivity is substituted into the selected sanding concentration calculation formula, and the fifth group branch joint required sanding concentration N is obtained 分5 , unit: Kg / m 2 ;

[0086] (64) Obtain the main joint, the first group branch joint, the second group branch joint, the third group branch joint, the fourth group branch joint, and the fifth group branch joint height:

[0087] According to the reservoir physical property condition, the conventional fracturing joint height G is determined by using the fracturing software, and the main joint, the first group branch joint, the second group branch joint, the third group branch joint, the fourth group branch joint, and the fifth group branch joint height are all G, unit: m;

[0088] (65) Obtain the main joint, the first group branch joint, the second group branch joint, the third group branch joint, the fourth group branch joint, and the fifth group branch joint required sand amount:

[0089] V 主 =(2×L 主 ×G×N 主 ) / ρ 砂 , wherein V 主 is the main joint required quartz sand, unit: m 3 , and ρ 砂 is the proppant density, unit: Kg / m 3 ;

[0090] V 分1 =(4×L 分1 ×G×N 分1 ) / ρ 砂 , wherein V 分1 is the first group branch joint required quartz sand, unit: m 3 , and ρ 砂 is the proppant density, unit: Kg / m 3 ;

[0091] V 分2 =(4×L 分2 ×G×N 分2 ) / ρ 砂 , wherein V 分2 is the second group branch joint required quartz sand, unit: m 3 , and ρ 砂 is the proppant density, unit: Kg / m 3 ;

[0092] V 分3 =(4×L 分3 ×G×N 分3 ) / ρ 砂 , wherein V 分3Vmain= (4 x Lmain x G x Nmain) / p 3 , p 砂 is the proppant density, in Kg / m 3 ;

[0093] V 分4 = (4 x L 分4 x G x N 分4 ) / p 砂 , where V 分4 is the quartz sand required for the fourth group of branch fractures, in m 3 , p 砂 is the proppant density, in Kg / m 3 ;

[0094] V 分5 = (4 x L 分5 x G x N 分5 ) / p 砂 , where V 分5 is the quartz sand required for the fifth group of branch fractures, in m 3 , p 砂 is the proppant density, in Kg / m 3 ;

[0095] (66) Obtain the amount of sand required for the fracturing interval:

[0096] Determine the number of branch fracture groups;

[0097] If the number of branch fracture groups is 0, then V 层 = V 主 , where V 层 is the amount of sand required for the fracturing interval, in m 3 ;

[0098] If the number of branch fracture groups is 1, then Vlayer= Vmain+ Vbranch1, where Vlayeris the amount of sand required for the fracturing interval;

[0099] If the number of branch fracture groups is 2, then Vlayer= Vmain+ Vbranch1+ Vbranch2, where Vlayeris the amount of sand required for the fracturing interval;

[0100] If the number of branch fracture groups is 3, then Vlayer= Vmain+ Vbranch1+ Vbranch2+ Vbranch3, where Vlayeris the amount of sand required for the fracturing interval;

[0101] If the number of branch fracture groups is 4, then Vlayer= Vmain+ Vbranch1+ Vbranch2+ Vbranch3+ Vbranch4, where Vlayeris the amount of sand required for the fracturing interval;

[0102] If the number of branch fracture groups is 5, then Vlayer= Vmain+ Vbranch1+ Vbranch2+ Vbranch3+ Vbranch4+ Vbranch5, where Vlayeris the amount of sand required for the fracturing interval.

[0103] S7: draw fracture system morphology; optimize fracturing layer sanding steps;

[0104] The method for drawing the fracture system morphology comprises the following steps:

[0105] (71) Obtain the main fracture half-length: determine the optimal main fracture half-length L 主 ;

[0106] (72) Obtain the number of branch fracture groups;

[0107] (73) Obtain the distance from the initiation point of each group of branch fractures to the wellbore, the initiation angle, and the turning radius;

[0108] (74) Obtain the length of each group of branch fractures;

[0109] (75) Draw the fracture system morphology:

[0110] Draw the main fracture morphology, with the main fracture half-length being L 主 , and the main fracture extending uniformly around the wellbore;

[0111] Draw the fracture system morphology, and add branch fractures on both sides of the main fracture, with 4 branch fractures in each group, 2 branch fractures on each side of the main fracture, and 1 branch fracture on each wing of the single-sided main fracture, and the distance from the initiation point of each group of branch fractures to the wellbore, the initiation angle, and the turning radius being consistent with step (73).

[0112] The method for optimizing the fracturing layer sanding steps is as follows:

[0113] If the number of branch fracture groups is 0, the wellbore is set as point O, and the end of the main fracture is set as point P, then the sanding step is divided into one step, the first-step sanding amount V1 = (L PO / L PO ) × V 主 , with the unit being m 3 ;

[0114] If the number of branch fracture groups is 1, the wellbore is set as point O, the end of the main fracture is set as point P, and the initiation point of the first group of branch fractures is set as point A, then the sanding step is divided into two steps, the first-step sanding amount V1 = (L PA / L PO ) × V 主 , and the second-step sanding amount V2 = (L AO / L PO ) × V 主 + V 分1 , with the unit being m 3 ;

[0115] If the number of branch fracture groups is 2, the wellbore is set as point O, the end of the main fracture is set as point P, the initiation point of the first group of branch fractures is set as point A, and the initiation point of the second group of branch fractures is set as point B, then the sanding step is divided into three steps, the first-step sanding amount V1 = (L PA / L PO ) x V 主 , the sand volume of the second step V2 = (L AB / L PO ) x V 主 + V 分1 , the sand volume of the third step V3 = (L BO / L PO ) x V 主 + V 分2 , and the unit is m 3 ;

[0116] If the number of branch fracture groups is 3, the wellbore is set as point O, the end of the main fracture is set as point P, the first group of branch fractures is set as point A, the second group of branch fractures is set as point B, and the third group of branch fractures is set as point C, then the sand adding step is divided into four steps, the sand volume of the first step V1 = (L PA / L PO ) x V 主 , the sand volume of the second step V2 = (L AB / L PO ) x V 主 + V 分1 , the sand volume of the third step V3 = (L BC / L PO ) x V 主 + V 分2 , the sand volume of the fourth step V4 = (L CO / L PO ) x V 主 + V 分3 , and the unit is m 3 ;

[0117] If the number of branch fracture groups is 4, the wellbore is set as point O, the end of the main fracture is set as point P, the first group of branch fractures is set as point A, the second group of branch fractures is set as point B, the third group of branch fractures is set as point C, and the fourth group of branch fractures is set as point D, then the sand adding step is divided into five steps, the sand volume of the first step V1 = (L PA / L PO ) x V 主 , the sand volume of the second step V2 = (L AB / L PO ) x V 主 + V 分1 , the sand volume of the third step V3 = (L BC / L PO ) x V 主 + V 分2 , the sand volume of the fourth step V4 = (L CD / L PO ) x V 主 + V 分3 , and the sand volume of the fifth step V5 = (L DO / L PO) x V 主 + V 分4 , unit: m 3 ;

[0118] If the number of branch fracture groups is 5 groups, the wellbore is set as point O, the end of the main fracture is set as point P, the first group of branch fractures is set as point A, the second group of branch fractures is set as point B, the third group of branch fractures is set as point C, the fourth group of branch fractures is set as point D, and the fifth group of branch fractures is set as point E, then the sand adding step is divided into six steps, the first step sand amount V1 = (L PA / L PO ) x V 主 , the second step sand amount V2 = (L AB / L PO ) x V 主 + V 分1 , the third step sand amount V3 = (L BC / L PO ) x V 主 + V 分2 , the fourth step sand amount V4 = (L CD / L PO ) x V 主 + V 分3 , the fifth step sand amount V5 = (L DE / L PO ) x V 主 + V 分4 , and the sixth step sand amount V6 = (L EO / L PO ) x V 主 + V 分5 , unit: m 3 .

[0119] Embodiment 1

[0120] Taking the fracturing layer section of well F as an example, the method for optimizing the sand adding step of the straight well multi-branch fracture fracturing is described, and the specific method is as follows:

[0121] Step 1: Obtain the three-direction stress of the fracturing layer section;

[0122] The fracturing layer section of well F has no experimental data of geostress test, but has X-mac logging interpretation results, so the X-mac logging interpretation results are preferentially selected as the three-direction stress of the fracturing layer section, that is, the minimum horizontal principal stress of the fracturing layer section is 30 MPa, the maximum horizontal principal stress is 35 MPa, and the vertical stress is 38 MPa.

[0123] Step 2: Determine whether the fracture of the fracturing layer section is a vertical fracture;

[0124] The minimum horizontal principal stress of the fractured section of the well F is 30 MPa, the maximum horizontal principal stress is 35 MPa, and the vertical stress is 38 MPa, and the minimum horizontal principal stress is less than the maximum horizontal principal stress, which is less than the vertical stress, and it is judged that the fracture is a vertical fracture.

[0125] Step 3: judging the applicability of the straight well multi-branch fracture fracturing technology;

[0126] The horizontal stress difference of the fractured section is 35 MPa-30 MPa=5 MPa, and the fracture is a vertical fracture, and it is judged that the straight well multi-branch fracture fracturing technology is applicable.

[0127] Step 4: obtaining the distance from the branch fracture initiation point to the wellbore, the initiation angle and the turning radius of each group in the numerical simulation test; specifically as follows:

[0128] (1) obtaining the distance L1 from the branch fracture initiation point to the wellbore, the first group branch fracture initiation angle A1 and the first group branch fracture turning radius r1 of the first group branch fracture in the numerical simulation test:

[0129] L1=-0.0321x 2 +14.511x+6.9=78.7m, wherein L1 is the distance from the branch fracture initiation point to the wellbore, the unit is m, and x is the horizontal stress difference, the unit is MPa;

[0130] A1=-0.3452x 2 -9.75x+86.738=29.4°, wherein A1 is the first group branch fracture initiation angle, the unit is °, x is the horizontal stress difference, the unit is MPa;

[0131] r1=1.655x 2 -25.967x+104.84=16.4m, wherein r1 is the first group branch fracture turning radius, the unit is m, x is the horizontal stress difference, the unit is MPa;

[0132] (2) obtaining the distance L2 from the branch fracture initiation point to the wellbore, the second group branch fracture initiation angle A2 and the second group branch fracture turning radius r2 of the second group branch fracture in the numerical simulation test:

[0133] L2=0.7405x 2 +6.5357x+5.9667=57.2m, wherein L2 is the distance from the branch fracture initiation point to the wellbore, the unit is m, x is the horizontal stress difference, the unit is MPa;

[0134] A2=-0.619x 2 -6.7143x+87.762=38.7°, wherein A2 is the second group branch fracture initiation angle, the unit is °, x is the horizontal stress difference, the unit is MPa;

[0135] r2 = 1.6783x 2 -27.276x + 114.25 = 19.8m, where r2 is the third set of branch slot turning radius, unit is m, x is the horizontal stress difference, unit is MPa;

[0136] (3) Obtain the distance between the third set of branch slot initiation point and the wellbore distance L3, the third set of branch slot initiation angle A3, and the third set of branch slot turning radius r3:

[0137] L3 = 0.6417x 2 + 4.9536x + 0.2976 = 41.1m, where L3 is the third set of branch slot initiation point distance from the wellbore, unit is m, x is the horizontal stress difference, unit is MPa;

[0138] A3 = -1.2262x 2 - 2.6789x + 89.405 = 45.4°, where A3 is the third set of branch slot initiation angle, unit is °, x is the horizontal stress difference, unit is MPa;

[0139] r3 = 1.6084x 2 - 27.386x + 119.58 = 22.9m, where r3 is the third set of branch slot turning radius, unit is m, x is the horizontal stress difference, unit is MPa;

[0140] (4) Obtain the distance between the fourth set of branch slot initiation point and the wellbore distance L4, the fourth set of branch slot initiation angle A4, and the fourth set of branch slot turning radius r4:

[0141] L4 = 0.906x 2 + 1.175x - 0.7881 = 28.2m, where L4 is the fourth set of branch slot initiation point distance from the wellbore, unit is m, x is the horizontal stress difference, unit is MPa;

[0142] A4 = -1.6548x 2 + 0.8071x + 88.548 = 51.2°, where A4 is the fourth set of branch slot initiation angle, unit is °, x is the horizontal stress difference, unit is MPa;

[0143] r4 = 1.4755x 2 - 27.065x + 124.42 = 26.0m, where r4 is the fourth set of branch slot turning radius, unit is m, x is the horizontal stress difference, unit is MPa;

[0144] (5) Obtain the distance between the fifth set of branch slot initiation point and the wellbore distance L5, the fifth set of branch slot initiation angle A5, and the fifth set of branch slot turning radius r5:

[0145] L5 = 0.9012x2 -1.2107x - 0.1119 = 16.4m, where L5 is the fifth group of branch fracture initiation point distance from the wellbore distance, unit m, x is the horizontal stress difference, unit MPa;

[0146] A5 = -1.8571x 2 + 3.0357x + 87.697 = 56.4°, where A5 is the fifth group of branch fracture initiation angle, unit °, x is the horizontal stress difference, unit MPa;

[0147] r5 = 1.3427x 2 - 26.744x + 129.25 = 29.1m, where r5 is the fifth group of branch fracture turning radius, unit m, x is the horizontal stress difference, unit MPa.

[0148] Step 5: Optimize the fracture parameters of the main fracture of the fracturing interval;

[0149] The reservoir permeability of the fracturing interval is 5mD, the porosity is 12.1%, and the sandstone thickness is 4.6m.

[0150] Combined with the historical fracture parameters of the block and experience, the main fracture half-length and conductivity optimization scheme is made, the eclipse software is applied to carry out simulation of different main fracture parameters, according to the simulation results, the main fracture parameter and production relationship chart is made, according to the production inflection point on the chart, the optimal main fracture half-length is determined as 160m, and the conductivity is 20um 2 .cm.

[0151] Step 6: Obtain the branch fracture initiation point distance from the wellbore distance, the initiation angle, and the turning radius of each group of the fracturing interval; the specific method is as follows:

[0152] The main fracture half-length of the numerical simulation test is 120m, the main fracture half-length of the fracturing interval is optimized to 160m, and the conversion is carried out according to the similarity principle;

[0153] The branch fracture initiation point distance from the wellbore distance of the first group of the fracturing interval is 104.9m, the branch fracture initiation angle of the first group is 29.4°, and the branch fracture turning radius of the first group is 21.9m;

[0154] The branch fracture initiation point distance from the wellbore distance of the second group of the fracturing interval is 76.3m, the branch fracture initiation angle of the first group is 38.7°, and the branch fracture turning radius of the first group is 26.4m;

[0155] The branch fracture initiation point distance from the wellbore distance of the third group of the fracturing interval is 54.8m, the branch fracture initiation angle of the first group is 45.4°, and the branch fracture turning radius of the first group is 30.5m;

[0156] The fourth group of branch fractures of the fracturing interval has a distance of 37.6 m from the wellbore to the fracture initiation point, a first group of branch fractures has an initiation angle of 51.2°, and the first group of branch fractures has a turning radius of 34.7 m;

[0157] The fifth group of branch fractures of the fracturing interval has a distance of 21.9 m from the wellbore to the fracture initiation point, a first group of branch fractures has an initiation angle of 56.4°, and the first group of branch fractures has a turning radius of 38.8 m.

[0158] Step 7: optimizing the fracture parameters of each group of branch fractures of the fracturing interval; including the following steps:

[0159] (1) preparing a first group of branch fracture length and conductivity optimization scheme, see Table 1; on the basis of the main fracture parameter optimization model, according to the reservoir characteristics of the fracturing interval, the distance from the wellbore to the fracture initiation point, the initiation angle, and the turning radius of the first group of branch fractures, combined with the historical fracture parameters and experience of the block, the first group of branch fracture length and conductivity optimization scheme is prepared, the eclipse software is applied to carry out branch fracture parameter simulation according to the optimization scheme, according to the simulation results, the branch fracture parameter and production relationship chart is prepared, and according to the production inflection point on the chart, the optimal branch fracture length of the first group of branch fractures is determined as 100 m, and the conductivity is 15um 2 .cm;

[0160] (2) on the basis of the first group of branch fracture optimization model, according to the reservoir characteristics of the fracturing interval, the distance from the wellbore to the fracture initiation point, the initiation angle, and the turning radius of the second group of branch fractures, combined with the historical fracture parameters and experience of the block, the second group of branch fracture length and conductivity optimization scheme is prepared, the eclipse software is applied to carry out branch fracture parameter simulation according to the optimization scheme, according to the simulation results, the branch fracture parameter and production relationship chart is prepared, and according to the production inflection point on the chart, the optimal branch fracture length of the second group of branch fractures is determined as 110 m, and the conductivity is 15um 2 .cm;

[0161] (3) on the basis of the second group of branch fracture optimization model, according to the reservoir characteristics of the fracturing interval, the distance from the wellbore to the fracture initiation point, the initiation angle, and the turning radius of the third group of branch fractures, combined with the historical fracture parameters and experience of the block, the third group of branch fracture length and conductivity optimization scheme is prepared, the eclipse software is applied to carry out branch fracture parameter simulation according to the optimization scheme, according to the simulation results, the branch fracture parameter and production relationship chart is prepared, and according to the production inflection point on the chart, the optimal branch fracture length of the third group of branch fractures is determined as 120 m, and the conductivity is 15um 2 .cm;

[0162] (4) On the basis of the third group of branch fracture optimization model, according to the reservoir characteristics of the fracturing interval and the distance from the fourth group of branch fracture initiation point to the wellbore, the initiation angle and the steering radius, combined with the historical fracture parameters and experience of the block, the fourth group of branch fracture length and conductivity optimization scheme is made, the eclipse software is applied to carry out branch fracture parameter simulation according to the optimization scheme, according to the simulation results, the branch fracture parameter and production relationship chart is made, according to the yield inflection point on the chart, the optimal branch fracture length of the fourth group of branch fracture is determined as 130m, and the conductivity is 15um 2 .cm;

[0163] (5) On the basis of the fourth group of branch fracture optimization model, according to the reservoir characteristics of the fracturing interval and the distance from the fifth group of branch fracture initiation point to the wellbore, the initiation angle and the steering radius, combined with the historical fracture parameters and experience of the block, the fifth group of branch fracture length and conductivity optimization scheme is made, the eclipse software is applied to carry out branch fracture parameter simulation according to the optimization scheme, according to the simulation results, the branch fracture parameter and production relationship chart is made, according to the yield inflection point on the chart, the optimal branch fracture length of the fifth group of branch fracture is determined as 140m, and the conductivity is 15um 2 .cm;

[0164] (6) As shown in Figure 1 , the branch fracture group number and production relationship chart is made, according to the yield inflection point on the chart, the optimal branch fracture group number is determined as 3 groups.

[0165] The eighth step is to optimize the fracturing interval sand scale; specifically including the following steps:

[0166] (1) Obtain the closure pressure of the main fracture, the first group of branch fracture, the second group of branch fracture, the third group of branch fracture, the fourth group of branch fracture and the fifth group of branch fracture:

[0167] P 闭主 = minimum horizontal principal stress = 30MPa, rounding to ten digits, then P 闭主 = 30MPa;

[0168] P 闭分1 = -0.0821x5 2 +0.825x5+0.0214+30=32.1MPa, rounding to ten digits, then P 闭分1 = 30MPa;

[0169] P 闭分2 = -0.0702x5 2 +0.85x5+0.0417+30=32.5MPa, rounding to ten digits, then P 闭分2 = 30MPa;

[0170] P闭分3 = -0.0524 x 5 2 + 0.8571 x 5 + 0.0524 + 30 = 33.0 MPa, rounding the value to ten significant digits, then P 闭分3 = 30 MPa;

[0171] P 闭分4 = -0.0369 x 5 2 + 0.8929 x 5 + 0.0512 = 33.6 MPa, rounding the value to ten significant digits, then P 闭分4 = 30 MPa;

[0172] P 闭分5 = -0.0018 x 5 2 + 0.8518 x 5 + 0.0607 + 30 = 34.3 MPa, rounding the value to ten significant digits, then P 闭分5 = 30 MPa;

[0173] (2) Obtain the relationship between the sanding concentration and the fracture conductivity under the conditions of a closure pressure of 10 MPa, 20 MPa, 30 MPa, 40 MPa, 50 MPa, and 60 MPa:

[0174] N 10 = 0.1706 x - 2.0089, where N 10 is the sanding concentration under the condition of a closure pressure of 10 MPa, in kg / m 2 , and x is the fracture conductivity, in um 2 · cm;

[0175] N 20 = 0.2438 x - 1.988, where N 20 is the sanding concentration under the condition of a closure pressure of 20 MPa, in kg / m 2 , and x is the fracture conductivity, in um 2 · cm;

[0176] N 30 = 0.3879 x - 1.9241, where N 30 is the sanding concentration under the condition of a closure pressure of 30 MPa, in kg / m 2 , and x is the fracture conductivity, in um 2 · cm;

[0177] N 40 = 0.4876 x - 0.8364, where N 40 is the sanding concentration under the condition of a closure pressure of 40 MPa, in kg / m 2 , and x is the fracture conductivity, in um 2.cm;

[0178] N 50 = 0.8042x - 0.3572, where N 50 The sand concentration is given under a closure pressure of 50 MPa, in kg / m³. 2 x represents the fracture conductivity, in μm. 2 .cm;

[0179] N 60 = 1.6267x - 0.0559, where N 60 The sand concentration is given under a closure pressure of 50 MPa, in kg / m³. 2 x represents the fracture conductivity, in μm. 2 .cm;

[0180] (3) Obtain the required sand concentration for the main joint, the first group of branch joints, the second group of branch joints, the third group of branch joints, the fourth group of branch joints, and the fifth group of branch joints:

[0181] The closure pressure of the main joint is 30 MPa, and N is selected. 30 =0.3879x-1.9241 is the formula for calculating sand concentration; the optimized main joint conductivity is 20µm. 2 .cm, substitute into the formula to obtain the required sand concentration N for the main joint. 主 =0.3879×20-1.9241=5.8Kg / m 2 ;

[0182] The closure pressure of the first group of branch seams is 30 MPa, and N is selected. 30 =0.3879x-1.9241 is the formula for calculating sand concentration. The optimized first set of branch joint conductivity is 15µm. 2 .cm, substitute into the formula to obtain the required sand concentration N for the main joint. 分1 =0.3879×15-1.9241=3.9Kg / m 2 ;

[0183] The closing pressure of the second set of branch joints is 30 MPa. The formula for calculating the sand concentration is N30 = 0.3879x - 1.9241. The optimized conductivity of the second set of branch joints is 15 μm²·cm. Substituting these values ​​into the formula yields the required sand concentration N for the main joint. 分2 =0.3879×15-1.9241=3.9Kg / m 2 ;

[0184] The closure pressure of the third group of branch fractures is 30 MPa, N30=0.3879x-1.9241 is selected as the sand concentration calculation formula, the optimized third group of branch fractures has a flow conductivity of 15 um2.cm, and the sand concentration N required by the main fracture is obtained by substituting the formula 分3 =0.3879x15-1.9241=3.9 Kg / m 2 ;

[0185] The closure pressure of the fourth group of branch fractures is 30 MPa, N30=0.3879x-1.9241 is selected as the sand concentration calculation formula, the optimized fourth group of branch fractures has a flow conductivity of 15 um2.cm, and the sand concentration N required by the main fracture is obtained by substituting the formula 分4 =0.3879x15-1.9241=3.9 Kg / m 2 ;

[0186] The closure pressure of the fifth group of branch fractures is 30 MPa, N30=0.3879x-1.9241 is selected as the sand concentration calculation formula, the optimized fifth group of branch fractures has a flow conductivity of 15 um2.cm, and the sand concentration N required by the main fracture is obtained by substituting the formula 分5 =0.3879x15-1.9241=3.9 Kg / m 2 ;

[0187] (4) Obtain the height of the main fracture, the first group of branch fractures, the second group of branch fractures, the third group of branch fractures, the fourth group of branch fractures and the fifth group of branch fractures

[0188] According to the reservoir physical property conditions, the conventional fracturing fracture height is 10 m determined by using the oil reservoir software eclipse, and the fracture height of the main fracture, the first group of branch fractures, the second group of branch fractures, the third group of branch fractures, the fourth group of branch fractures and the fifth group of branch fractures is all 10 m;

[0189] (5) Obtain the sand amount required by the main fracture, the first group of branch fractures, the second group of branch fractures, the third group of branch fractures, the fourth group of branch fractures and the fifth group of branch fractures

[0190] V 主 =(2x160m x 10m x 5.8 Kg / m 2 ) / 1600 Kg / m 3 =11.6 m 3 ;

[0191] V 分1 =(4x100m x 10m x 3.9 Kg / m 2 ) / 1600 Kg / m 3 =9.8 m 3 ;

[0192] V 分2= (4 x 110m x 10m x 3.9Kg / m 2 ) / 1600Kg / m 3 = 10.7m 3 ;

[0193] V 分3 = (4 x 120m x 10m x 3.9Kg / m 2 ) / 1600Kg / m 3 = 11.7m 3 ;

[0194] V 分4 = (4 x 130m x 10m x 3.9Kg / m 2 ) / 1600Kg / m 3 = 12.7m 3 ;

[0195] V 分5 = (4 x 140m x 10m x 3.9Kg / m 2 ) / 1600Kg / m 3 = 13.7m 3 ;

[0196] (6) Obtain the amount of sand required for the fracturing interval:

[0197] Determine the optimal branch fracture group number as 3 groups;

[0198] The optimal branch fracture group number is 3 groups, then:

[0199] V 层 = V 主 + V 分1 + V 分2 + V 分3 = 11.6m 3 + 9.8m 3 + 10.7m 3 + 11.7m 3 = 43.8m 3 .

[0200] Step 9: Draw the fracture system morphology; specifically as follows:

[0201] (1) Obtain the optimal main fracture half length: Determine the optimal main fracture half length 160m.

[0202] (2) Obtain the optimal branch fracture group number:

[0203] Determine the optimal branch fracture group number as 3 groups.

[0204] (3) Obtain the distance from the wellbore to the initiation point, the initiation angle, and the turning radius of each group of branch fractures:

[0205] The distance between the first group of branch fractures initiation point and the wellbore is 104.9 m, the first group of branch fractures initiation angle is 29.4°, and the first group of branch fractures turning radius is 21.9 m;

[0206] The distance between the second group of branch fractures initiation point and the wellbore is 76.3 m, the first group of branch fractures initiation angle is 38.7°, and the first group of branch fractures turning radius is 26.4 m;

[0207] The distance between the third group of branch fractures initiation point and the wellbore is 54.8 m, the first group of branch fractures initiation angle is 45.4°, and the first group of branch fractures turning radius is 30.5 m;

[0208] The distance between the fourth group of branch fractures initiation point and the wellbore is 37.6 m, the first group of branch fractures initiation angle is 51.2°, and the first group of branch fractures turning radius is 34.7 m;

[0209] The distance between the fifth group of branch fractures initiation point and the wellbore is 21.9 m, the first group of branch fractures initiation angle is 56.4°, and the first group of branch fractures turning radius is 38.8 m.

[0210] (4) Obtain the optimal length of each group of branch fractures

[0211] The optimal branch fracture length of the first group of branch fractures is 100 m, the optimal branch fracture length of the second group of branch fractures is 110 m, the optimal branch fracture length of the third group of branch fractures is 120 m, the optimal branch fracture length of the fourth group of branch fractures is 130 m, and the optimal branch fracture length of the fifth group of branch fractures is 140 m.

[0212] (5) Draw the fracture system morphology: the number of branch fracture groups is 3, the wellbore is set as point O, the main fracture end is set as point P, the first group of branch fractures initiation point is set as point A, the second group of branch fractures initiation point is set as point B, and the third group of branch fractures initiation point is set as point C. The fracture system morphology is as shown in Figure 2

[0213] Step 10: Optimize the sand adding step of the fracturing interval; specifically as follows:

[0214] The optimization of the sand adding step of the fracturing interval is divided into four steps:

[0215] The first step sand amount V1=(L PA / L PO )×V 主 = (55.1 ÷ 160) × 11.6 = 4.0 m 3 ;

[0216] The second step sand amount V2=(L AB / L PO )×V 主 +V 分1 = (28.6 ÷ 160) × 11.6 + 9.8 = 11.9;​

[0217] Third step sand amount V3 = (L BC / L PO ) x V 主 + V 分2 = (21.5 ÷ 160) x 11.6 + 10.7 = 12.3;

[0218] Fourth step sand amount V4 = (L CO / L PO ) x V 主 + V 分3 = (54.8 ÷ 160) x 11.6 + 11.7 = 15.7, unit: m 3 .

[0219] Table 1

[0220]

[0221] Those skilled in the art will appreciate that the embodiments described herein are presented for the purpose of aiding the reader in understanding the method of implementing the present application, and should be understood as not limiting the scope of protection of the present application to such specific recitations and embodiments. Those skilled in the art can make various other specific modifications and combinations according to the technical inspiration of the present application disclosed, without departing from the essence of the present application, and such modifications and combinations are still within the scope of protection of the present application.

Claims

1. A method for optimizing a straight hole multilateral fracturing and sand placement procedure, characterized by: The method comprises the following steps: S1: obtaining three-directional stresses of a fracturing interval; determining whether the fractures of the fracturing interval are vertical fractures; S2: based on the obtained three-directional stresses of the fracturing interval and the determination of the vertical fractures, determining the applicability of the multi-lateral fracture technology of a vertical well; S3: for the well to which the multi-lateral fracture technology of the vertical well is applicable, obtaining the distance from each group of branch fractures to the wellbore, the fracture initiation angle and the turning radius in the numerical simulation test; S4: optimizing the fracture parameters of the main fractures of the fracturing interval; obtaining the distance from each group of branch fractures to the wellbore, the fracture initiation angle and the turning radius of the fracturing interval; S5: optimizing the fracture parameters of each group of branch fractures of the fracturing interval; S6: based on the optimized fracture parameters of each group of branch fractures of the fracturing interval, optimizing the sanding scale of the fracturing interval; S7: drawing the fracture system morphology; and optimizing the sanding steps of the fracturing interval.

2. The method of claim 1, wherein: The method for obtaining the three-directional stresses of the fracturing interval in the step S1 is as follows: The three-directional stresses of the fracturing interval are the minimum horizontal principal stress, the maximum horizontal principal stress and the vertical stress of the fracturing interval; (1) if there are experimental data of the in-situ stress test of the fracturing interval, the experimental data are preferentially selected as the three-directional stresses of the fracturing interval; (2) if there are no experimental data of the in-situ stress test of the fracturing interval, but there are X-mac logging interpretation results, the X-mac logging interpretation results are preferentially selected as the three-directional stresses of the fracturing interval; (3) if there are no experimental data of the in-situ stress test and X-mac logging interpretation results of the fracturing interval, only the conventional logging interpretation results are selected as the three-directional stresses of the fracturing interval.

3. The method of claim 1, wherein: The method for determining whether the fractures of the fracturing interval are vertical fractures in the step S1 is as follows: (1) the minimum horizontal principal stress < the maximum horizontal principal stress < the vertical stress, and it is determined that the fractures are vertical fractures; (2) the minimum horizontal principal stress < the vertical stress < the maximum horizontal principal stress, and it is determined that the fractures are vertical fractures.

4. The method of claim 1 or 2 or 3, wherein: The method for determining the applicability of the multi-lateral fracture technology of the vertical well in the step S2 is as follows: the fractures are vertical fractures, and the horizontal stress difference of the fracturing interval is less than or equal to 6 MPa, and it is determined that the multi-lateral fracture technology of the vertical well is applicable. The horizontal stress difference of the fracturing interval is the value obtained by subtracting the minimum horizontal principal stress from the maximum horizontal principal stress.

5. The method according to claim 1, wherein: The method for obtaining the distance from each group of branch fractures to the wellbore, the fracture initiation angle and the turning radius in the step S3 comprises the following steps: obtaining the first to fifth groups of branch fractures in the numerical simulation test. (1) obtaining the distance L1 from the first group of branch fractures to the wellbore, the first group of branch fractures initiation angle A1 and the first group of branch fractures turning radius r1; (2) obtaining the distance L2 from the second group of branch fractures to the wellbore, the second group of branch fractures initiation angle A2 and the second group of branch fractures turning radius r2; (3) obtaining the distance L3 from the third group of branch fractures to the wellbore, the third group of branch fractures initiation angle A3 and the third group of branch fractures turning radius r3; (4) obtaining the distance L4 from the fourth group of branch fractures to the wellbore, the fourth group of branch fractures initiation angle A4 and the fourth group of branch fractures turning radius r4; (5) obtaining the distance L5 from the fifth group of branch fractures to the wellbore, the fifth group of branch fractures initiation angle A5 and the fifth group of branch fractures turning radius r5.

6. The method according to claim 1, wherein: The step S4 optimizes the fracture parameters of the main fracture of the fracturing interval by the method comprising the following steps: The fracture parameters are the fracture half-length and the conductivity. According to the reservoir characteristics of the fracturing interval, the main fracture half-length and the conductivity optimization scheme are prepared, and the software is applied to develop different main fracture parameter simulation. According to the simulation results, a graph of the main fracture parameter and the production is made, and the optimal main fracture half-length L is determined according to the production inflection point on the graph 主 and the flow conductivity D 主 , wherein L 主 is in m, and D 主 is in um 2 · cm.

7. The method of claim 1 or 6, wherein: The step S4 obtains the distance from the initiation point of each group of branch fractures to the wellbore, the initiation angle, and the turning radius by the method comprising the following steps: The main fracture half-length in the numerical simulation test is 120 m. According to the similarity principle, the distance from the initiation point of the first group, the second group, the third group, the fourth group, and the fifth group of branch fractures to the wellbore, the initiation angle, and the turning radius are converted according to the optimized main fracture half-length of the fracturing interval.

8. The method according to claim 1, wherein: The step S5 optimizes the fracture parameters of each group of branch fractures of the fracturing interval by the method comprising the following steps: (1) Based on the main fracture parameter optimization model, according to the reservoir characteristics of the fracturing section and the distance from the fracture initiation point of the first group of branch fractures to the wellbore, the fracture initiation angle, and the turning radius, an optimization scheme for the length and conductivity of the first group of branch fractures was prepared. The software was used to simulate the fracture parameters of the branch fractures according to the optimization scheme. Based on the simulation results, a graph showing the relationship between the fracture parameters of the branch fractures and the production rate was prepared. Based on the production inflection point on the graph, the optimal branch fracture length L of the first group of branch fractures was determined. 分1 and flow guiding capacity D 分1 L 分1 The unit is m, D 分1 The unit is um 2 .cm; (2) On the basis of the first group of branch fracture optimization model, according to the reservoir characteristics of the fracturing interval and the distance from the wellbore to the second group of branch fracture initiation point, the initiation angle and the steering radius, the second group of branch fracture length and conductivity optimization scheme is made, the software is applied to carry out branch fracture parameter simulation according to the optimization scheme, according to the simulation results, the branch fracture parameter and production relationship chart is made, and the second group of branch fracture optimal branch fracture length L 分2 and conductivity D 分2 is determined according to the inflection point of the production on the chart, wherein L 分2 is m, D 分2 is um 2 .cm; (3) Based on the second set of branch fracture optimization models, according to the reservoir characteristics of the fracturing section and the distance from the fracture initiation point of the third set of branch fractures to the wellbore, fracture initiation angle, and turning radius, an optimization scheme for the length and conductivity of the third set of branch fractures is prepared. The software is used to simulate the fracture parameters of the branch fractures according to the optimization scheme. Based on the simulation results, a graph showing the relationship between the fracture parameters of the branch fractures and the production rate is prepared. Based on the production inflection point on the graph, the optimal branch fracture length L of the third set of branch fractures is determined. 分3 and flow guiding capacity D 分3 L 分3 The unit is m, D 分3 The unit is um 2 .cm; (4) On the basis of the third group of branch fracture optimization model, according to the reservoir characteristics of the fracturing interval and the distance between the fourth group of branch fracture initiation point and the wellbore, the initiation angle and the steering radius, the fourth group of branch fracture length and conductivity optimization scheme is made, the software is applied to carry out branch fracture parameter simulation according to the optimization scheme, according to the simulation results, the branch fracture parameter and production relationship chart is made, and the fourth group of branch fracture optimal branch fracture length L 分4 and conductivity D 分4 is determined according to the inflection point of the production on the chart, wherein L 分4 is m, D 分4 is um 2 .cm; (5) Based on the fourth group of branch fracture optimization models, and according to the reservoir characteristics of the fracturing section and the distance from the fracture initiation point of the fifth group of branch fractures to the wellbore, fracture initiation angle, and turning radius, an optimization scheme for the length and conductivity of the fifth group of branch fractures was prepared. The software was used to simulate the fracture parameters of the branch fractures according to the optimization scheme. Based on the simulation results, a graph showing the relationship between the fracture parameters and production was prepared. Based on the production inflection point on the graph, the optimal branch fracture length L of the fifth group of branch fractures was determined. 分5 and flow guiding capacity D 分5 L 分5 The unit is m, D 分5 The unit is um 2 .cm; (6) A branch fracture group number and production relationship chart is prepared, and the optimal branch fracture group number is determined according to the production inflection point on the chart.

9. The method of claim 1 or 8, wherein: The step S6 optimizes the sanding scale of the fracturing interval based on the optimized fracture parameters of each group of branch fractures of the fracturing interval by the method comprising the following steps: (1) The closure pressure of the main fracture, the first group of branch fractures, the second group of branch fractures, the third group of branch fractures, the fourth group of branch fractures, and the fifth group of branch fractures is obtained. (2) The relationship between the sanding concentration and the fracture conductivity under the conditions of the closure pressure of 10 MPa, 20 MPa, 30 MPa, 40 MPa, 50 MPa, and 60 MPa is obtained. (3) The required sanding concentration of the main fracture, the first group of branch fractures, the second group of branch fractures, the third group of branch fractures, the fourth group of branch fractures, and the fifth group of branch fractures is obtained. According to the main joint closure pressure selection sand concentration calculation formula, and the optimization of the main joint diversion capacity into the selected sand concentration calculation formula, the main joint required sand concentration N is obtained 主 , unit: Kg / m 2 ; According to the formula for selecting the sanding concentration of the first group of branch joints, the optimized diversion capacity of the main joint is substituted into the formula for selecting the sanding concentration to obtain the required sanding concentration N of the first group of branch joints 分1 , in Kg / m 2 ; According to the formula for selecting the sanding concentration of the second group of branch joints, the optimized diversion capacity of the main joint is substituted into the formula for selecting the sanding concentration to obtain the required sanding concentration N of the second group of branch joints 分2 , in Kg / m 2 ; According to the third group branch joint closure pressure selection sanding concentration calculation formula, the optimized main joint diversion capacity is substituted into the selected sanding concentration calculation formula, and the required sanding concentration N of the third group branch joint is obtained 分3 , unit: Kg / m 2 ; According to the fourth group branch joint closure pressure selection sand concentration calculation formula, the optimized main joint conductivity is substituted into the selected sand concentration calculation formula, and the required sand concentration N of the fourth group branch joint is obtained 分4 , unit: Kg / m2; According to the fifth group branch joint closing pressure selection sanding concentration calculation formula, the optimized main joint flow conductivity is substituted into the selected sanding concentration calculation formula to obtain the required sanding concentration N of the fifth group branch joint 分5 , unit: Kg / m 2 ; (4) The fracture height of the main fracture, the first group of branch fractures, the second group of branch fractures, the third group of branch fractures, the fourth group of branch fractures, and the fifth group of branch fractures is obtained. According to the reservoir physical property conditions, the conventional fracturing fracture height G is determined by using the fracturing software, and the fracture height of the main fracture, the first group of branch fractures, the second group of branch fractures, the third group of branch fractures, the fourth group of branch fractures, and the fifth group of branch fractures is G, which is in meters. (5) The required sand amount of the main fracture, the first group of branch fractures, the second group of branch fractures, the third group of branch fractures, the fourth group of branch fractures, and the fifth group of branch fractures is obtained. (6) The required sand amount of the fracturing interval is obtained: The branch fracture group number is determined. If the branch fracture group number is 0, then V 层 = V 主 , where V 层 is the required sand volume of the fractured interval, in m 3 ; If the number of branch slit groups is 1 group, V 层 = V 主 + V 分1 , If the number of branch slit groups is 2, V 层 = V 主 + V 分1 + V 分2 ; If the number of branch slit groups is 3, V 层 = V 主 + V 分1 + V 分2 + V 分3 ; If the number of branch slit groups is 4 groups, V 层 = V 主 + V 分1 + V 分2 + V 分3 + V 分4 ; If the number of branch slit groups is 5, V 层 = V 主 + V 分1 + V 分2 + V 分3 + V 分4 + V 分5 ; where: V 层 V is the amount of sand required for fracturing the interval; 主 V 分1 V 分2 V 分3 V 分4 V 分5 V is the amount of sand required for fracturing the main fracture, the first set of branch fractures, the second set of branch fractures, the third set of branch fractures, the fourth set of branch fractures, and the fifth set of branch fractures, respectively.

10. The method of claim 1, wherein: The step S7 draws the fracture system morphology by the method comprising the following steps: (1) Obtain the main fracture half-length: determine the optimal main fracture half-length L 主 ; (2) The branch fracture group number is obtained. (3) The distance from the initiation point of each group of branch fractures to the wellbore, the initiation angle, and the turning radius are obtained. (4) The length of each group of branch fractures is obtained. (5) The fracture system morphology is drawn: Draw the main fracture morphology, the main fracture half-length is L 主 , the main fracture extends uniformly with the wellbore as the center; The fracture system morphology is drawn, the branch fractures are added on both sides of the main fracture, each group of branch fractures is 4, each group of branch fractures has two branch fractures on both sides of the main fracture, each group of branch fractures has one branch fracture on each wing of the single-sided main fracture, and the distance from the initiation point of each group of branch fractures to the wellbore, the initiation angle, and the turning radius are consistent with step (3).

11. The method according to claim 1, wherein: The step S7 optimizes the sanding step of the fracturing interval by the method comprising the following steps: If the branch fracture group number is 0, the wellbore is set as O point, and the main fracture end is set as P point, then the sand adding step is divided into one step, the first step sand amount V1 = (L PO / L PO )×V 主 , unit: m 3 ; wherein: L PO is the distance from O point to P point; If the branch fracture group number is 1 group, the wellbore is set as point O, the main fracture end is set as point P, and the first group of branch fracture initiation point is set as point A, then the sanding step is divided into two steps, the first step sanding amount V1=(L PA / L PO )×V 主 , the second step sanding amount V2=(L AO / L PO )×V 主 +V 分1 , the unit is m 3 ; wherein: L PA is the distance from point A to point P; L AO is the distance from point A to point O; If the branch fracture group number is 2 groups, the wellbore is set as point O, the main fracture end is point P, the first group of branch fracture initiation point is point A, and the second group of branch fracture initiation point is point B, then the sanding step is divided into three steps, the first step sanding amount V1 = (L PA / L PO )×V 主 , the second step sanding amount V2 = (L AB / L PO )×V 主 +V 分1 , the third step sanding amount V3 = (L BO / L PO )×V 主 +V 分2 , the unit is m 3 ; wherein: L AB is the distance from point A to point B; L BO is the distance from point B to point O; If the branch fracture group number is 3 groups, the wellbore is set as point O, the main fracture end is point P, the first group of branch fracture initiation point is point A, the second group of branch fracture initiation point is point B, and the third group of branch fracture initiation point is point C, then the sand adding step is divided into four steps, the first step sand V1 = (L PA / L PO ) × V 主 , the second step sand V2 = (L AB / L PO ) × V 主 + V 分1 , the third step sand V3 = (L BC / L PO ) × V 主 + V 分2 , the fourth step sand V4 = (L CO / L PO ) × V 主 + V 分3 , the unit is m 3 ; wherein: L BC is the distance from point B to point C; L CO is the distance from point C to point O; L AB is the distance from point A to point B; If the branch fracture group number is 4 groups, the wellbore is set as point O, the main fracture end is set as point P, the first group of branch fracture initiation point is set as point A, the second group of branch fracture initiation point is set as point B, the third group of branch fracture initiation point is set as point C, and the fourth group of branch fracture initiation point is set as point D, then the sand adding step is divided into five steps, the first step sand V1=(L PA / L PO )×V 主 , the second step sand V2=(L AB / L PO )×V 主 +V 分1 , the third step sand V3=(L BC / L PO )×V 主 +V 分2 , the fourth step sand V4=(L CD / L PO )×V 主 +V 分3 , and the fifth step sand V5=(L DO / L PO )×V 主 +V 分4 , the unit is m 3 ; wherein: L AO is the distance from point A to point O; L CD is the distance from point C to point D. If the branch fracture group number is 5 groups, the wellbore is set as point O, the main fracture end is point P, the first group of branch fracture initiation point is point A, the second group of branch fracture initiation point is point B, the third group of branch fracture initiation point is point C, the fourth group of branch fracture initiation point is point D, and the fifth group of branch fracture initiation point is point E, then the sand adding step is divided into six steps, the first step sand V1=(L PA / L PO )×V 主 , the second step sand V2=(L AB / L PO )×V 主 +V 分1 , the third step sand V3=(L BC / L PO )×V 主 +V 分2 , the fourth step sand V4=(L CD / L PO )×V 主 +V 分3 , the fifth step sand V5=(L DE / L PO )×V 主 +V 分4 , the sixth step sand V6=(L EO / L PO )×V 主 +V 分5 , the unit is m 3 ; wherein: L DE is the distance from point D to point E.

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