A method for determining boundary conditions in numerical simulation of tectonic stress field

Abstract

The present invention discloses a method for determining boundary conditions of numerical simulation of tectonic stress field based on an adaptive algorithm. On the basis of establishing a geomechanical model, the method includes the following steps: clarifying the test range of the direction and magnitude of the external force applied to the heterogeneous geomechanical model according to the magnitude and direction of the measured ground stress of a single well; selecting a number of test points at equal intervals within the test range to carry out numerical simulation and obtain the error between the simulation result of the single well and the measured data under each boundary condition; determining whether the minimum error of the obtained simulation result meets the research needs and determining whether the force application direction needs to be adjusted; carrying out numerical simulation with the optimal boundary conditions and obtaining the relevant parameters of the tectonic stress field. The method disclosed by the present invention can be widely used in determining the optimal boundary conditions for numerical simulation of tectonic stress field, and mainly relies on the command stream execution of the numerical simulation software, with less manual participation and high operability.

Description

Technical Field

[0001] The invention relates to the field of geological reservoir geomechanics, and in particular to a method and system for determining boundary conditions for numerical simulation of a tectonic stress field. Background Art

[0002] Stress field simulation based on the finite element method has been widely and effectively used in the numerical simulation of paleostress field and geostress field, as well as the prediction of reservoir fractures and low-order faults (Liu, JS, Ding, WL, Yang, HM, Liu, Y., 2021. Quantitative Multiparameter Prediction of Fractured TightSandstone Reservoirs: A Case Study of the Yanchang Formation of the OrdosBasin, Central China. Spe Journal. 26 (5), 3342-3373. https: / / doi.org / 10.2118 / 205495-pa). At present, the simulation of stress field based on the finite element method must be carried out according to the following steps: establish a geological model, establish a mechanical model, establish a mathematical model, and use numerical simulation software such as ANSYS software to perform numerical simulation of stress field. When establishing a mechanical model, the determination of rock mechanical parameters can be based on empirical values ​​given by sedimentary facies and tectonic units (Ding Wenlong, Zeng Weite, Wang Ruyue, et al., Simulation of tectonic stress field and prediction method of fracture distribution in shale reservoirs and their applications [J]. Earth Science Frontiers, 2016, 23(02): 63-74. DOI: 10.13745 / j.esf.2016.02.008). Recently, some scholars have used seismic inversion and other methods to obtain heterogeneous rock mechanical parameters (Liu, JS, Zhang, GJ, Bai, JP, Ding, WL, Yang, HM, Liu, Y., 2022. Quantitative prediction of the drilling azimuth of horizontal wells in fractured tight sandstone based on reservoir geomechanics in the Ordos Basin, central China. Marine and Petroleum Geology. 136, 22. https: / / doi.org / 10.1016 / j.marpetgeo.2021.105439).At present, when constructing mechanical models, there are few quantitative studies on the determination of boundary conditions. Most of them are based on the direction of regional tectonic stress in the geological history period of numerical simulation to qualitatively determine the direction of external force, and obtain the principal stress applied by the mechanical model based on the sample acoustic emission experiment. As for reducing the error between the numerical simulation results and the measured data of a single well, it can only be reduced by manually debugging the magnitude and direction of the horizontal stress applied to the model. The workload is large and the operation is cumbersome, which makes the improvement of numerical simulation efficiency encounter bottlenecks. Although predecessors have used ANSYS parameterized programming language APDL to realize the compilation of adaptive programs, they are limited to comparing the simulated value and measured value of the stress magnitude of a single well (Zheng Ruosi. Research on the Current Ground Stress of Yi 176 Block in Bonan Oilfield [D]. China University of Petroleum (East China), 2018. DOI: 10.27644 / d.cnki.gsydu.2018.000463), and the direction of the ground stress of a single well is not constrained by adaptive programs. Therefore, in general, the research foundation of adaptive algorithms for obtaining optimal mechanical boundary conditions based on numerical simulation software is weak, making it difficult to improve the efficiency and accuracy of numerical simulation. Summary of the invention

[0003] Based on this, the embodiments of the present application provide a method and system for determining boundary conditions for numerical simulation of tectonic stress fields, so as to solve the technical problem in the prior art that the optimal boundary conditions of the model for numerical simulation of stress fields are difficult to determine efficiently and accurately.

[0004] In a first aspect, a method for determining boundary conditions for numerical simulation of tectonic stress field is provided, the method comprising:

[0005] S1. According to the magnitude and direction of the measured ground stress in a single well, the test range of the direction and magnitude of the external force applied to the heterogeneous geomechanical model is clarified;

[0006] S2. Select several test points at equal intervals within the test range to carry out numerical simulation and obtain the error between the single well simulation result and the measured data under each boundary condition;

[0007] S3, determining whether the minimum error of the obtained simulation results meets the research needs and deciding whether the force direction needs to be adjusted;

[0008] S4. Carry out numerical simulation using optimal boundary conditions and obtain relevant parameters of the tectonic stress field.

[0009] Optionally, step S1 includes:

[0010] S11. Taking the average of the azimuths of the measured horizontal maximum principal stresses of all single wells as the direction of application of the horizontal maximum principal stress of the geomechanical model, the direction perpendicular to the direction of application of the horizontal maximum principal stress is the direction of application of the horizontal minimum principal stress;

[0011] S12, the maximum horizontal principal stress σ measured from all single wells H and the magnitude of the minimum horizontal principal stress σ h The maximum and minimum values ​​are obtained respectively, and the maximum horizontal principal stress σ H The maximum value of σ H-max , the minimum value is σ H-min , the minimum horizontal principal stress σ h The maximum value of σ h-max , the minimum value is σ h-min ;

[0012] S13, determining the test range of the horizontal principal stress of the geomechanical model according to the maximum and minimum values ​​of the measured horizontal maximum principal stress of the single well and the maximum and minimum values ​​of the measured horizontal minimum principal stress;

[0013] S14, when Bound σH-LOWER or Bound σH-UPPER With σ H-max and σ H-min When they are different in positive and negative, they are taken as 0. σh-LOWER or Bound σh-UPPER With σ h-max and σ h-min When the numbers are different in positive and negative, they are also 0;

[0014] Among them, Bound σH-LOWER Indicates the lower limit of the force test range in the direction of the maximum horizontal principal stress. σH-UPPER Indicates the lower limit of the force test range in the direction of the maximum horizontal principal stress. σh-LOWER Indicates the lower limit of the force test range in the horizontal minimum principal stress direction, Bound σh-UPPER Indicates the upper limit of the test range of force magnitude in the horizontal minimum principal stress direction.

[0015] Optionally, in step S13, according to the parameter σ obtained in step S12 H-max , σ H-min , σ h-max and σ h-min ;

[0016] The lower limit of the force test range of the geomechanical model in the direction of the maximum horizontal principal stress is Bound σH-LOWER Set as σ H-min +(σ H-max -σ H-min ) / 4, upper limit Bound σH-UPPER Set as

[0017] σ H-max +(σ H-max -σH-min ) / 4, the lower limit of the force test range of the geomechanical model in the horizontal minimum principal stress direction is Bound σh-LOWER Set as σ h-min -(σ h-max -σ h-min ) / 4, upper limit Bound σh-UPPER Set as σ h-max -(σ h-max -σ h-min ) / 4.

[0018] Optionally, step S2 includes:

[0019] S21. Test range of maximum principal stress applied horizontally Bound σH-LOWER To Bound σH-UPPER According to the research accuracy requirements, m test points σ are selected at equal intervals. H-i , that is, i is an integer from 1 to m;

[0020] S22, Test range of minimum principal stress applied horizontally Bound σh-LOWER To Bound σh-UPPER According to the research accuracy requirements, m test points σh-j are selected at equal intervals, that is, j is an integer from 1 to m;

[0021] S23, the combination of m test values ​​of the maximum horizontal principal stress and m test values ​​of the minimum horizontal principal stress can form a total of m 2 The boundary conditions of applying external force are realized by using the command flow of numerical simulation software. 2 The boundary conditions for applying external forces (σ H-i, σ h-j ) and obtain the error between the simulated value and the measured value under each boundary condition.

[0022] Optionally, in step S21, the horizontal maximum principal stress test range Bound σH-LOWER To Bound σH-UPPER Divided into (m-1) parts on average, i.e. the i-th test value σ of the horizontal maximum principal stress H-i for:

[0023]

[0024] Wherein i is an integer from 1 to m.

[0025] Optionally, in step S22, the horizontal minimum principal stress test range Bound σh-LOWER To Bound σh-UPPER Divide into (m-1) parts on average, i.e. the jth test value σ of the horizontal minimum principal stress h-j for:

[0026]

[0027] Wherein j is an integer from 1 to m.

[0028] Optionally, in step S23, each numerical simulation can obtain the maximum horizontal principal stress and the minimum horizontal principal stress, and then obtain the simulated values ​​of the maximum horizontal principal stress and the minimum horizontal principal stress of a single well;

[0029] Assuming that the total number of wells is n, the measured value and simulated value of the horizontal maximum principal stress of the kth well are σ H-mea-k and σ H-sim-k , the measured and simulated values ​​of the horizontal minimum principal stress are σ h-mea-k and σ h-sim-k , then the boundary condition (σ H-I , σ h-j ) The error between the simulated value and the measured value of the stress magnitude σ(σH-i, σh-j) for:

[0030]

[0031] Among them, Error σ(σH-i, σh-j) Used to characterize the boundary conditions (σ H-I , σ h-j ) The error between the simulated value and the measured value of the stress magnitude corresponding to each numerical simulation can obtain the sum of the components of the horizontal principal stress on the X-axis and Y-axis. Assuming that the sum of the components of the simulated value of the horizontal principal stress of the kth well on the X-axis and Y-axis are denoted as σ X-k and σ Y-k , assuming that the simulated value of the azimuth of the horizontal maximum principal stress is α sim-k , then we have:

[0032]

[0033] If the azimuth of the measured maximum horizontal principal stress is α mea-k , then with the boundary condition (σ H-i , σ h-j ) The error between the simulated value and the measured value of the horizontal maximum principal stress azimuth α(σH-i, σh-j) Defined as:

[0034]

[0035] Using alpha sim-k The tangent value of is used to calculate the error of the simulated value of the horizontal maximum principal stress azimuth angle; α sim-k With α mea-k The absolute value of the difference |α sim-k -αmea-k | directly reflects the error of the simulation value, and the tangent value of the difference tan(|α sim-k -α mea-k |) is:

[0036]

[0037] The tangent value E of the error between the simulated value and the measured value of the maximum principal stress azimuth rror ` tanα(σH-I, σh-j) Defined as:

[0038]

[0039] |α sim-k -α mea-k | Available through arctan[Error` tanα(σH-i, σh-j) ] is solved, and |α sim-k -α mea-k The ratio of the average value of | to 45° can reflect the error rate between the simulated value and the measured value of the horizontal maximum principal stress azimuth Error`` α(σH-i, σh-j) ,Right now:

[0040]

[0041] The above tanα sim-k Substitute the formula into this formula to get:

[0042]

[0043] Error rate between the simulated value and the measured value of the comprehensive horizontal maximum principal stress azimuth Error`` α(σH-i, σh-j) Error between simulated and measured stress values σ(σH-i, σh-j) The comprehensive error determination formula of stress magnitude and direction can be obtained, namely Error (σH-i, σh-j) equal:

[0044]

[0045] Among them, Error (σH-i, σh-j) Used to characterize the error between the simulated value and the measured value of stress magnitude.

[0046] Optionally, step S3 includes:

[0047] S31. Get Error (σH-i, σh-j) The minimum value of Error min and the corresponding (σ H-i , σ h-j ); Error (σH-i, σh-j) It is used to characterize the error between the simulated value and the measured value of stress magnitude;

[0048] S32. If Error (σH-i, σh-j) The minimum value of Error min The upper limit of the error allowed by the study has been met, so the corresponding (σ H-i , σ h-j ) can be used as the optimal boundary condition, and go to step S4; if the minimum value Errormin exceeds the upper limit of the error allowed by the study and the minimum value Error min The corresponding boundary conditions (σ H-i , σ h-j ) H-i Not equal to Bound σH-LOWER or Bound σH-UPPER , and σ h-j Not equal to Bound σh-LOWER or Bound σh-UPPER , which indicates that the optimal boundary condition (σ H-i ,σ h-j ) is not at the boundary of the test range, the error does not need to be reduced by adjusting the horizontal principal stress applied to the model, but by adjusting the direction of application of the horizontal principal stress, and then go to step S33. min The error limit allowed by the research is exceeded, and at least one of the following four conditions is met: (1) Minimum Error min The corresponding boundary conditions (σ H-i , σ h-j ) H-i Equal to Bound σH-LOWER ; (2) Minimum Error min The corresponding boundary conditions (σ H-i , σ h-j ) H-i Equal to Bound σH-UPPER ; (3) Minimum Error min The corresponding boundary conditions (σ H-i , σ h-j ) h-j Equal to Bound σh-LOWER ; (4) Minimum Error min The corresponding boundary conditions (σ H-i , σ h-j ) h-j Equal to Bound σh-UPPER ; This indicates that the optimal boundary condition (σ H-i , σ h-j ) is at the boundary of the test range, the error needs to be reduced by adjusting the horizontal principal stress applied to the model, and the process goes to step S34;

[0049] S33, the difference between the average value of the simulated value of the horizontal maximum principal stress azimuth at each well location and the average value of the measured value △α (σ H-i , σ h-j )for:

[0050]

[0051] The azimuth angle currently used in step S11 to apply the horizontal maximum principal stress to the model Add △α(σ H-i , σ h-j ) is used as the adjusted azimuth angle of the maximum horizontal principal stress applied to the model, that is, As the new azimuth angle for applying the maximum horizontal principal stress to the model, the azimuth angle perpendicular to the direction is the azimuth angle for applying the minimum horizontal principal stress to the model, and the process goes to step S12 and is executed in sequence;

[0052] S34, taking one of the following measures corresponding to the four situations in step S32: σH-LOWER -(σ H-max -σ H-min ) instead of Bound σH-LOWER As the lower limit of the force test range of the model in the direction of the maximum horizontal principal stress, use Bound σH-UPPER -(σ H-max -σ H-min ) instead of Bound σH-UPPER As the upper limit of the test range; (2) Use Bound σH-LOWER +(σ H-max -σ H-min ) instead of Bound σH-LOWER As the lower limit of the force test range of the model in the direction of the maximum horizontal principal stress, use Bound σH-UPPER +(σ H-max -σ H-min ) instead of Bound σH-UPPER As the upper limit of the test range; (3) Use Bound σh-LOWER -(σ h-max -σ h-min ) instead of Bound σh-LOWER As the lower limit of the force test range of the model in the horizontal minimum principal stress direction, use Bound σh-UPPER -(σ h-max -σ h-min ) instead of Bound σh-UPPER As the upper limit of the test range; (4) Use Bound σh-LOWER +(σ h-max -σ h-min ) instead of Bound σh-LOWERAs the lower limit of the force test range of the model in the horizontal minimum principal stress direction, use Bound σh-UPPER +(σ h-max -σ h-min ) instead of Bound σh-UPPER As the upper limit of the test range; go to step S14 and execute in sequence.

[0053] Optionally, in step S4, the optimal boundary condition (σ H-j , σ h-j ) Carrying out numerical simulation of stress field can obtain the best numerical simulation results and conduct research on stress magnitude and direction.

[0054] In a second aspect, a system for determining boundary conditions for numerical simulation of tectonic stress fields is provided, the system comprising:

[0055] A determination module is used to determine the test range of the direction and magnitude of the external force applied to the heterogeneous geomechanical model according to the magnitude and direction of the measured ground stress in a single well;

[0056] An acquisition module is used to select a number of test points at equal intervals within the test range to carry out numerical simulation and obtain the error between the single well simulation result and the measured data under each boundary condition;

[0057] A determination module is used to determine whether the minimum error of the obtained simulation results meets the research needs and decide whether the force direction needs to be adjusted;

[0058] The simulation module conducts numerical simulations with optimal boundary conditions and obtains relevant parameters of the tectonic stress field.

[0059] Compared with the prior art, the advantages of the present invention are as follows: the present invention is based on the geological model and rock mechanics parameters that have been determined in the numerical simulation of the stress field, and uses the programming language APDL of the ANSYS software as a means to determine the test range of the boundary conditions through the measured data of the direction and magnitude of the ground stress of a single well, and select test points at equal intervals to carry out numerical simulation, obtain the error between the simulated value and the measured value under different boundary conditions, and determine the boundary condition corresponding to the minimum error that meets the research needs as the optimal boundary condition of the geological model. The method can be widely used in the determination of boundary conditions for numerical simulation of stress fields, and can be automatically operated by writing the programming language APDL, thereby improving the efficiency and accuracy of numerical simulation, and having high operability and application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] In order to more clearly illustrate the implementation methods of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the implementation methods or the description of the prior art. Obviously, the drawings in the following description are only exemplary, and for ordinary technicians in this field, other implementation drawings can be derived from the provided drawings without creative work.

[0061] Figure 1 is a flow chart of a method for determining boundary conditions for numerical simulation of tectonic stress field according to an embodiment of the present invention;

[0062] Figure 2 is a plane distribution diagram of Young's modulus and Poisson's ratio according to an embodiment of the present invention;

[0063] Figure 3 is a plan view of a geomechanical model and boundary condition settings according to an embodiment of the present invention;

[0064] Figure 4 It is a schematic diagram of setting the test range of the horizontal maximum principal stress and the horizontal minimum principal stress of the model in an embodiment of the present invention;

[0065] Figure 5 is a distribution diagram of the average value of the horizontal principal stress error, the average value of the tangent value of the horizontal maximum principal stress azimuth error, the average value of the azimuth error and the average value of the comprehensive error of the test model 1 according to the embodiment of the present invention (the meaning of the horizontal axis and the vertical axis of the distribution diagram can be found in the attached figure). Figure 4 );

[0066] Figure 6 is a distribution diagram of the average value of the horizontal principal stress error, the average value of the tangent value of the horizontal maximum principal stress azimuth error, the average value of the azimuth error and the average value of the comprehensive error of the test model 2 according to the embodiment of the present invention (the meaning of the horizontal axis and the vertical axis of the distribution diagram can be found in the attached figure). Figure 4 );

[0067] Figure 7 is a distribution diagram of the average value of the horizontal principal stress error, the average value of the tangent value of the horizontal maximum principal stress azimuth error, the average value of the azimuth error and the average value of the comprehensive error of the test model 3 according to the embodiment of the present invention (the meaning of the horizontal axis and the vertical axis of the distribution diagram can be found in the attached figure). Figure 4 );

[0068] Figure 8 is a distribution diagram of the average value of the horizontal principal stress error, the average value of the tangent value of the horizontal maximum principal stress azimuth error, the average value of the azimuth error and the average value of the comprehensive error of the test model 4 according to the embodiment of the present invention (the meaning of the horizontal axis and the vertical axis of the distribution diagram can be found in the attached figure). Figure 4 );

[0069] Fig. 9is a distribution diagram of the average value of the horizontal principal stress error, the average value of the tangent value of the horizontal maximum principal stress azimuth error, the average value of the azimuth error and the average value of the comprehensive error of the test model 5 according to the embodiment of the present invention (the meaning of the horizontal axis and the vertical axis of the distribution diagram can be found in the attached figure). Figure 4 );

[0070] Fig.10 The model horizontal maximum principal stress, horizontal minimum principal stress and horizontal maximum principal stress azimuth obtained by numerical simulation of ground stress under optimal boundary conditions according to an embodiment of the present invention;

[0071] Fig.11 It is a system block diagram for determining boundary conditions for numerical simulation of a tectonic stress field according to an embodiment of the present invention. DETAILED DESCRIPTION

[0072] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0073] Attached Figure 1 A method for determining boundary conditions for numerical simulation of tectonic stress field based on an adaptive algorithm according to an embodiment of the present invention is shown, comprising the following steps:

[0074] S1. According to the magnitude and direction of the measured ground stress in a single well, the test range of the direction and magnitude of the external force applied to the heterogeneous geomechanical model is clarified;

[0075] S2. Select several test points at equal intervals within the test range to carry out numerical simulation and obtain the error between the single well simulation result and the measured data under each boundary condition;

[0076] S3, determining whether the minimum error of the obtained simulation results meets the research needs and deciding whether the force direction needs to be adjusted;

[0077] S4. Carry out numerical simulation using optimal boundary conditions and obtain relevant parameters of the tectonic stress field.

[0078] The present invention is based on the determination of the geomechanical model in the numerical simulation of geostress based on ANSYS software, and is based on the programming language APDL in ANSYS software. By setting the test range of the direction of application of the maximum horizontal principal stress, the magnitude of the maximum horizontal principal stress, and the magnitude of the minimum horizontal principal stress, the ANSYS software can automatically carry out multiple simulations and calculate the error between the simulated value and the measured value of the magnitude of the horizontal stress of a single well and the direction of the maximum horizontal principal stress under each test condition, and obtain the geostress simulation boundary condition with the minimum error according to the research accuracy standard. This method can be widely used in determining the optimal boundary conditions for numerical simulation of geostress. However, the existing method for determining the optimal boundary conditions for numerical simulation of geostress is mainly based on the magnitude and direction of the stress applied to the model boundary by manual debugging, and the work efficiency is low and it is difficult to meet the needs of high-precision research.

[0079] In one embodiment, a geomechanical model is constructed using heterogeneous rock mechanical parameters. The plane distributions of Young's modulus parameters and Poisson's ratio parameters required for constructing the geomechanical model are as follows: Figure 2 a and Figure 2 As shown in b.

[0080] In one embodiment, step S1 includes:

[0081] S11. Taking the average of the azimuths of the measured horizontal maximum principal stresses of all single wells as the direction of application of the horizontal maximum principal stress of the geomechanical model, the direction perpendicular to the direction of application of the horizontal maximum principal stress is the direction of application of the horizontal minimum principal stress;

[0082] S12, the maximum horizontal principal stress σ measured from all single wells H and the magnitude of the minimum horizontal principal stress σ h The maximum and minimum values ​​are obtained respectively, and the maximum horizontal principal stress σ H The maximum value of σ H-max , the minimum value is σ H-min , the minimum horizontal principal stress σ h The maximum value of σ h-max , the minimum value is σ h-min ;

[0083] S13, determining the test range of the horizontal principal stress of the geomechanical model according to the maximum and minimum values ​​of the measured horizontal maximum principal stress of the single well and the maximum and minimum values ​​of the measured horizontal minimum principal stress;

[0084] S14. Since the stress magnitudes of different wells in the same area are different but of the same nature, usually σ H-max and σ H-min Same positive or negative, σ h-max and σ h-min Same positive or negative. σH-LOWERor Bound σH-UPPER With σ H-max and σ H-min When they are both positive and negative, they are 0. σh-LOWER or Bound σh-UPPER With σ h-max and σ h-min When the numbers are both positive and negative, the value is 0.

[0085] In one embodiment, in step S11, there are 6 wells Well 1 to 6 in the study area, and their locations are as shown in the following figure. Figure 2 The measured data of the horizontal maximum principal stress, horizontal minimum principal stress and horizontal maximum principal stress azimuth of the six wells are shown in Table 1. From the measured values ​​of the horizontal maximum principal stress azimuth of the wells, it can be seen that the average value is NE 50.17°, so the horizontal maximum principal stress direction of the geomechanical model can be set as NE 50° and SW 230°, and the horizontal minimum principal stress direction can be set as SE 140° and NW 320° (see Appendix). Figure 3 a). Use ANSYS software to mesh the geomechanical model and then encrypt the area near the fault, so that the number of grids near the fault is larger and the calculation is more accurate, as shown in the attached figure. Figure 3 As shown in b.

[0086] Table 1 Horizontal principal stress and maximum horizontal principal stress direction measured in drilling in one embodiment

[0087]

[0088] In one embodiment, in step S12, the maximum principal stress magnitude σ of all single wells measured horizontally is obtained from Table 1. H and the magnitude of the minimum horizontal principal stress σ h The maximum and minimum values ​​are obtained respectively, and the maximum horizontal principal stress σ H The maximum value of σ H-max =125 MPa, the minimum value is σ H-min =118 MPa, minimum horizontal principal stress σ h The maximum value of σ h-max =83 MPa, the minimum value is σ h-min =73 MPa.

[0089] In one embodiment, in step S13, according to the parameter σ obtained in step S12 H-max , σ H-min , σ h-max and σ h-min , set the lower limit of the force test range of model 1 in the horizontal maximum principal stress direction Bound σH-LOWER Set as σ H-min +(σ H-max -σH-min ) / 4 is 119.75 MPa, the upper limit Bound σH-UPPER Set as σ H-max +(σ H-max -σ H-min ) / 4, that is, 126.75 MPa, the lower limit of the force test range of the geomechanical model in the horizontal minimum principal stress direction is Bound σh-LOWER Set as σ h-min -(σ h-max -σ h-min ) / 4 is 70.5 MPa, the upper limit Bound σh-UPPER Set as σ h-max -(σ h-max -σ h-min ) / 4 that is 85.5MPa.

[0090] In one embodiment, step S2 includes:

[0091] S21. Test range of maximum principal stress applied horizontally Bound σH-LOWER To Bound σH-UPPER According to the research accuracy requirements, m test points σ are selected at equal intervals. H-i , that is, i is an integer from 1 to m;

[0092] S22, Test range of minimum principal stress applied horizontally Bound σh-LOWER To Bound σh-UPPER According to the research accuracy requirements, m test points σ are selected at equal intervals. h-j , that is, j is an integer from 1 to m;

[0093] S23, the combination of m test values ​​of the maximum horizontal principal stress and m test values ​​of the minimum horizontal principal stress can form a total of m 2 The boundary conditions of applying external force are realized by using the command flow of numerical simulation software. 2 The boundary conditions for applying external forces (σ H-i , σ h-j ) and obtain the error between the simulated value and the measured value under each boundary condition.

[0094] In one embodiment, in step S21, the horizontal maximum principal stress test range Bound σH-LOWER To Bound σH-UPPER Divided into 9 parts on average, i.e. the i-th test value σ of the horizontal maximum principal stress H-i for:

[0095]

[0096] Where i is an integer from 1 to 10. The Bound σH-LOWER To Bound σH-UPPER Substituting into the above formula, we can get the i-th test value σ H-i for:

[0097]

[0098] In one embodiment, in step S22, the horizontal minimum principal stress test range Bound σh-LOWER To Bound σh-UPPER Divided into 9 parts on average, i.e. the jth test value σ of the horizontal minimum principal stress h-j for:

[0099]

[0100] Wherein j is an integer from 1 to 10. The Bound obtained in step S13 σh-LOWER To Bound σh-UPPER Substituting into the above formula, we can get the jth test value σ h-j for:

[0101]

[0102] In one embodiment, in step S23, there are 10 test points for the maximum horizontal principal stress and 10 test points for the minimum horizontal principal stress, so a total of 10×10 or 100 simulations can be performed, as shown in the attached figure. Figure 4 As shown. Each numerical simulation can obtain the maximum horizontal principal stress and the minimum horizontal principal stress, and then obtain the simulated values ​​of the maximum horizontal principal stress and the minimum horizontal principal stress of a single well. The total number of wells is 6, and the measured value and simulated value of the maximum horizontal principal stress of the kth well are σ H-mea-k and σ H-sim-k , the measured and simulated values ​​of the horizontal minimum principal stress are σ h-mea-k and σ h-sim-k , then with the boundary condition (σ H-I , σ h-j ) The error between the simulated value and the measured value of the stress magnitude σ(σH-i, σh-j) for:

[0103]

[0104] According to the numerical simulation results, the above formula is used to calculate the stress error, and it can be obtained that the model 1 has different boundary conditions (σ H-i , σ h-j The average error of the horizontal principal stress under Figure 5As shown in Figure a, when i is equal to 7 and j is equal to 8, the average error of the horizontal principal stress of model 1 reaches the minimum value, which is 0.0276, and when i and j are both equal to 1, the error value reaches the maximum value, which is 0.1006.

[0105] Among them, Error σ(σH-i, σh-j) Used to characterize the boundary conditions (σ H-I , σ h-j ) The error between the simulated value and the measured value of the stress magnitude corresponding to each numerical simulation can obtain the sum of the components of the horizontal principal stress on the X-axis and Y-axis. Assuming that the sum of the components of the simulated value of the horizontal principal stress of the kth well on the X-axis and Y-axis are denoted as σ X-k and σ Y-k , assuming that the simulated value of the azimuth of the horizontal maximum principal stress is α sim-k , then we have:

[0106]

[0107] If the azimuth of the measured maximum horizontal principal stress is α mea-k , then with the boundary condition (σ H-i , σ h-j ) The error between the simulated value and the measured value of the horizontal maximum principal stress azimuth α(σH-i, σh-j) Defined as:

[0108]

[0109] It is not easy to use α in ANSYS's programming language APDL. sim-k The tangent value of α is directly solved sim-k , so α is used directly here sim-k The error calculation of the simulated value of the horizontal maximum principal stress azimuth is performed using the tangent value of α sim-k With α mea-k The absolute value of the difference |α sim-k -α mea-k | directly reflects the error of the simulation value, and the tangent value of the difference tan(|α sim-k -α mea-k |) is:

[0110]

[0111] When |α sim-k -α mea-k The lower |, the greater the tan(|α sim-k -α mea-k |) is closer to 0, so the tangent value of the error between the simulated value and the measured value of the modified horizontal maximum principal stress azimuth is Error' tanα(σH-I, σh-j) Defined as:

[0112]

[0113] The distribution of the tangent value of the error between the simulated value and the measured value of the horizontal maximum principal stress azimuth of model 1 is shown in the attached figure. Figure 5 As shown in Figure b, it can be seen that when i is equal to 10 and j is equal to 1, the error is the smallest, which is only 0.1701, and when i is equal to 1 and j is equal to 10, the error is the largest, reaching 0.3351.

[0114] |α sim-k -α mea-k | Available through arctan[Error' tanα(σH-i, σh-j) ] is solved, and |α sim-k -α mea-k The ratio of the average value of | to 45° can reflect the error rate between the simulated value and the measured value of the horizontal maximum principal stress azimuth Error'' α(σH-i, σh-j) ,Right now:

[0115]

[0116] The above tanα sim-k Substitute the formula into this formula to get:

[0117]

[0118] The error rate distribution between the simulated value and the measured value of the horizontal maximum principal stress azimuth of model 1 is shown in the attached figure. Figure 5 As shown in c, it can be seen that when i is equal to 10 and j is equal to 1, the error is the smallest, which is 9.6556°, and when i is equal to 1 and j is equal to 10, the error is the largest, reaching 18.5244°.

[0119] Error rate between the simulated value and the measured value of the comprehensive horizontal maximum principal stress azimuth Error`` α(σH-i, σh-j) Error between simulated and measured stress values σ(σH-i, σh-j) The comprehensive error determination formula of stress magnitude and direction can be obtained, namely Error (σH-i, σh-j) equal:

[0120]

[0121] Among them, Error (σH-i, σh-j) Used to characterize the error between the simulated value and the measured value of stress magnitude.

[0122] The comprehensive error distribution of model 1 is shown in the attached figure. Figure 5 As shown in d, it can be seen that when i is equal to 10 and j is equal to 1, the error is the smallest, which is 0.1501, and when i is equal to 1 and j is equal to 10, the error is the largest, reaching 0.2272.

[0123] In one embodiment, step S3 includes:

[0124] S31. Get Error (σH-i, σh-j) The minimum value of Error min and the corresponding (σ H-i , σ h-j ); Error (σH-i, σh-j) It is used to characterize the error between the simulated value and the measured value of stress magnitude;

[0125] S32. If Error (σH-i, σh-j) The minimum value of Error min The upper limit of the error allowed by the study has been met, so the corresponding (σ H-i , σ h-j ) can be used as the optimal boundary condition and go to step S4; if the minimum value Error min The error limit allowed by the study and the minimum value Error min The corresponding boundary conditions (σ H-i , σ h-j ) H-i Not equal to Bound σH-LOWER or Bound σH-UPPER , and σ h-j Not equal to Bound σh-LOWER or Bound σh-UPPER , which indicates that the optimal boundary condition (σ H-i ,σ h-j ) is not at the boundary of the test range, the higher error does not need to be reduced by adjusting the horizontal principal stress applied to the model, but by adjusting the direction of application of the horizontal principal stress, and then go to step S33; if the minimum value Error min The error limit allowed by the research is exceeded, and at least one of the following four conditions is met: (1) Minimum Error min The corresponding boundary conditions (σ H-i ,σ h-j ) H-i Equal to Bound σH-LOWER ; (2) Minimum Error min The corresponding boundary conditions (σ H-i , σ h-j ) H-i Equal to Bound σH-UPPER ; (3) Minimum Error min The corresponding boundary conditions (σ H-i , σ h-j ) h-j Equal to Bound σh-LOWER ; (4) Minimum Error min The corresponding boundary conditions (σ H-i , σh-j ) h-j Equal to Bound σh-UPPER ; This indicates that the optimal boundary condition (σ H-i , σ h-j ) is at the boundary of the test range, the higher error needs to be reduced by adjusting the horizontal principal stress applied to the model, and the process goes to step S34;

[0126] S33, the difference between the average value of the simulated value of the horizontal maximum principal stress azimuth at each well location and the average value of the measured value △α (σ H-i , σ h-j )for:

[0127]

[0128] The azimuth angle currently used in step S11 to apply the horizontal maximum principal stress to the model Add △α(σ H-i , σ h-j ) is used as the adjusted azimuth angle of the maximum horizontal principal stress applied to the model, that is, As the new azimuth angle for applying the maximum horizontal principal stress to the model, the azimuth angle perpendicular to the direction is the azimuth angle for applying the minimum horizontal principal stress to the model, and the process goes to step S12 and is executed in sequence;

[0129] S34: Take one of the following measures corresponding to the four situations in step S32: (1) Use Bound σH-LOWER -(σ H-max -σ H-min ) instead of Bound σH-LOWER As the lower limit of the force test range of the model in the direction of the maximum horizontal principal stress, use Bound σH-UPPER -(σ H-max -σ H-min ) instead of Bound σH-UPPER As the upper limit of the test range; (2) Use Bound σH-LOWER +(σ H-max -σ H-min ) instead of Bound σH-LOWER As the lower limit of the force test range of the model in the direction of the maximum horizontal principal stress, use Bound σH-UPPER +(σ H-max -σ H-min ) instead of Bound σH-UPPER As the upper limit of the test range; (3) Use Bound σh-LOWER -(σ h-max -σ h-min ) instead of Bound σh-LOWER As the lower limit of the force test range of the model in the horizontal minimum principal stress direction, use Boundσh-UPPER -(σ h-max -σ h-min ) instead of Bound σh-UPPER As the upper limit of the test range; (4) Use Bound σh-LOWER +(σ h-max -σ h-min ) instead of Bound σh-LOWER As the lower limit of the force test range of the model in the horizontal minimum principal stress direction, use Bound σh-UPPER +(σ h-max -σ h-min ) instead of Bound σh-UPPER As the upper limit of the test range; go to step S14 and execute in sequence.

[0130] In one embodiment, in step S31, Error (σH-i, σh-j) The minimum value of 0.1501 corresponds to (σ H-i , σ h-j ) is (126.75 MPa, 70.5 MPa).

[0131] In one embodiment, in step S32, the minimum value of the comprehensive error 0.1501 exceeds the upper limit of 0.1 allowed by the research, so the boundary conditions need to be adjusted to reduce the error. It can be seen that in the optimal boundary conditions of model 1 (126.75 MPa, 70.5 MPa), the maximum horizontal principal stress applied to the model is equal to the upper limit of the test range Bound σH-UPPER That is 126.75 MPa. At the same time, the minimum horizontal principal stress applied to the model is equal to the lower limit of the test range. σh-LOWER That is 70.5 MPa, so go to step S34.

[0132] In one embodiment, in step S34, (126.75 MPa, 70.5 MPa) satisfies both situations (2) and (3), and the countermeasures for situation (2) or (3) can be taken first. The countermeasure for situation (3) is taken first, that is, using Bound σh-LOWER +(σ h-max -σ h-min ) instead of Bound σh-LOWER As the lower limit of the force test range of the model in the horizontal minimum principal stress direction, use Bound σh-UPPER -(σ h-max -σ h-min ) instead of Bound σh-UPPER As the upper limit of the test range, the lower limit of the force magnitude test range in the new horizontal minimum principal stress direction is Bound σh-LOWER =70.5-15=55.5MPa, the upper limit is Boundσh-UPPER =85.5-15=70.5 MPa, the adjusted model is defined as Model 3, and the process goes to step S14 and is executed sequentially.

[0133] The error analysis results of Model 2 are shown in the attached figure. Figure 6 As shown in the figure, it can be seen that the minimum value of the average value of the horizontal principal stress error is 0.0855, and the corresponding i and j are 7 and 10 respectively (see Appendix Figure 6 a); The maximum value of the average value of the horizontal principal stress magnitude error is 0.1928, and the corresponding i and j are 1 and 1 respectively (see Appendix Figure 6 a); The minimum value of the average value of the sine error of the difference between the simulated value and the measured value of the horizontal maximum principal stress azimuth is 0.1030, corresponding to i and j are 10 and 1 respectively, and the maximum value is 0.1949, corresponding to i and j are 1 and 10 respectively (Appendix Figure 6 b); The minimum value of the average difference between the simulated value and the measured value of the horizontal maximum principal stress azimuth is 5.8784°, and the corresponding i and j are 10 and 1 respectively, and the maximum value is 11.0285°, and the corresponding i and j are 1 and 10 respectively (Appendix Figure 6 c); The minimum value of the comprehensive error is 0.1492, corresponding to i and j are 10 and 7 respectively, and the maximum value is 0.1729, corresponding to i and j are 1 and 10 respectively (Appendix Figure 6 d).

[0134] It can be seen that for model 2, the optimal boundary condition corresponding to the minimum value of the comprehensive error is (126.75 MPa, 65.5 MPa), where 126.75 MPa is equal to the upper limit of the test range. σH-UPPER Therefore, it is necessary to implement the response plan of measure (2), that is, to use Bound σH-LOWER +(σ H-max -σ H-min ) instead of Bound σH-LOWER As the lower limit of the force test range of the model in the direction of the maximum horizontal principal stress, use Bound σH-LOWER -(σ H-max -σ H-min ) instead of Bound σH-UPPER As the upper limit of the test range, the lower limit of the force magnitude test range in the new horizontal maximum principal stress direction is Bound σH-LOWER =119.75+7=126.75 MPa, the upper limit is Bound σH-UPPER =126.75+7=133.75 MPa, the adjusted model is defined as Model 3, and the process goes to step S14 and is executed sequentially.

[0135] The error analysis results of Model 2 are shown in the attached figure. Figure 7As shown in the figure, the minimum value of the average value of the error of the horizontal principal stress is 0.0857, and the corresponding i and j are 1 and 10 respectively (see Appendix Figure 7 a); The maximum value of the average value of the error of the horizontal principal stress magnitude is 0.2043, and the corresponding i and j are 10 and 1 respectively (Appendix Figure 6 a); The minimum value of the average value of the sine error of the difference between the simulated value and the measured value of the horizontal maximum principal stress azimuth is 0.0930, corresponding to i and j are 10 and 1 respectively, and the maximum value is 0.1701, corresponding to i and j are 1 and 10 respectively (Appendix Figure 7 b); The minimum value of the average difference between the simulated value and the measured value of the horizontal maximum principal stress azimuth is 5.3120°, and the corresponding i and j are 10 and 1 respectively, and the maximum value is 9.6556°, and the corresponding i and j are 1 and 10 respectively (Appendix Figure 7 c); The minimum value of the comprehensive error is 0.1488, corresponding to i and j are 2 and 8 respectively, and the maximum value is 0.1612, corresponding to i and j are 10 and 1 respectively (Appendix Figure 7 d).

[0136] It can be seen that for model 3, the optimal boundary condition corresponding to the minimum value of the comprehensive error is (127.5278 MPa, 67.1667 MPa). 127.5278 MPa is not equal to the lower limit or upper limit of the force size test range of model 3 in the horizontal maximum principal stress direction, and 67.1667 MPa is not equal to the lower limit or upper limit of the force size test range of model 3 in the horizontal minimum principal stress direction. However, the comprehensive error of 0.1488 at this time still does not meet the upper limit of 0.1, so it is necessary to go to step S33; in model 3, the △α(σ H-i , σ h-j ) ranges from -5.3120° to -9.6556°, that is, the simulated horizontal maximum principal stress azimuth is generally lower than the measured value, so it is necessary to apply the horizontal maximum principal stress azimuth used in models 1 to 3 to the model. =50° plus △α(σ H-i , σ h-j ) is used as the adjusted azimuth for applying the horizontal maximum principal stress to the model. Here, 50°+10°=60° is used as the new azimuth for applying the horizontal maximum principal stress to the model, and the azimuth perpendicular to this direction is the azimuth for applying the horizontal minimum principal stress to the model. Go to step S12 and execute in sequence.

[0137] 60° is used as the azimuth angle for applying the maximum horizontal principal stress to the model, and 119.75 MPa is used as the Bound σH-LOWER , with 126.75 MPa as Bound σH-UPPER , with 70.5 MPa as Boundσh-LOWER , with 85.5 MPa as Bound σh-UPPER The model is defined as Model 4. The error analysis results of Model 4 are shown in the attached Figure 8 As shown in the figure, the minimum value of the average value of the error of the horizontal principal stress is 0.0285, and the corresponding i and j are 7 and 8 respectively (see Appendix Figure 8 a); The maximum value of the average value of the error of the horizontal principal stress magnitude is 0.1001, and the corresponding i and j are 1 and 1 respectively (Appendix Figure 8 a); The minimum value of the average value of the sine error of the difference between the simulated value and the measured value of the horizontal maximum principal stress azimuth is 0.0223, corresponding to i and j are 2 and 10 respectively, and the maximum value is 0.1659, corresponding to i and j are 10 and 1 respectively (Appendix Figure 8 b); The minimum value of the average difference between the simulated value and the measured value of the horizontal maximum principal stress azimuth is 1.2799°, corresponding to i and j of 2 and 10 respectively, and the maximum value is 9.4179°, corresponding to i and j of 10 and 1 respectively (Appendix Figure 8 c); The minimum value of the comprehensive error is 0.0342, corresponding to i and j are 3 and 10 respectively, and the maximum value is 0.1471, corresponding to i and j are 10 and 1 respectively (Appendix Figure 8 d).

[0138] It can be seen that for model 4, the optimal boundary condition corresponding to the minimum value of the comprehensive error is (121.3055 MPa, 85.5 MPa), where 85.5 MPa is equal to the upper limit of the test range. σh-UPPER Therefore, it is necessary to implement the response plan of measure (4), that is, Replace Bound σh-LOWER As the lower limit of the force magnitude test range of the model in the horizontal minimum principal stress direction, Replace Bound σh-UPPER As the upper limit of the test range, the lower limit of the force magnitude test range in the new horizontal minimum principal stress direction is Bound σh-LOWER =70.5+15=85.5MPa, the upper limit is Bound σh-UPPER =85.5+15=100.5 MPa, the adjusted model is defined as Model 5, and the process goes to step S14 and is executed sequentially.

[0139] The error analysis results of Model 5 are shown in the attached figure. Fig. 9 As shown in the figure, the minimum value of the average value of the horizontal principal stress error is 0.0304, and the corresponding i and j are 7 and 1 respectively (see Appendix Fig. 9 a); The maximum value of the average value of the error of the horizontal principal stress magnitude is 0.1131, and the corresponding i and j are 1 and 10 respectively (Appendix Fig. 9a); The minimum value of the average value of the sine error of the difference between the simulated value and the measured value of the horizontal maximum principal stress azimuth is 0.0223, corresponding to i and j are 2 and 1 respectively, and the maximum value is 0.2840, corresponding to i and j are 1 and 10 respectively (Appendix Fig. 9 b); The minimum value of the average difference between the simulated value and the measured value of the horizontal maximum principal stress azimuth is 1.2799°, and the corresponding i and j are 2 and 1 respectively, and the maximum value is 15.8556°, and the corresponding i and j are 1 and 10 respectively (Appendix Fig. 9 c); The minimum value of the comprehensive error is 0.0320, corresponding to i and j are 5 and 2 respectively, and the maximum value is 0.2327, corresponding to i and j are 1 and 10 respectively (Appendix Fig. 9 d).

[0140] It can be seen that for model 5, the optimal boundary condition corresponding to the minimum comprehensive error is (122.8611 MPa, 87.1667 MPa), where 122.8611 MPa and 87.1667 MPa are not equal to the upper and lower limits of the horizontal principal stress test range, and the lowest comprehensive error of 0.0320 is also less than the maximum allowable error of 0.1. Therefore, when the horizontal principal stress applied to the model is (122.8611 MPa, 87.1667 MPa) and 60° is used as the azimuth angle for applying the horizontal maximum principal stress to the model, the error between the simulation results and the measured results is the lowest, and the above is taken as the optimal boundary condition.

[0141] In one embodiment, in step S4, the optimal boundary conditions (122.8611 MPa, 87.1667 MPa) are used to carry out numerical simulation of the stress field, which can obtain the best numerical simulation results and conduct research on the magnitude and direction of stress. The obtained horizontal maximum principal stress, horizontal minimum principal stress and horizontal maximum principal stress azimuth are shown in the attached figure. Fig.10 In the simulation results, the simulated values ​​of the horizontal maximum principal stress, horizontal minimum principal stress and the azimuth of the horizontal maximum principal stress of Wells 1 to 6 are shown in Table 2, and the errors between the simulated values ​​and the measured values ​​are shown in Table 3. It can be seen that the errors of the horizontal stress magnitude are less than 10% except for a few that are greater than 10%, and the errors of the horizontal maximum principal stress azimuth are generally less than 3°, which shows that the reliability of the numerical simulation results is very high.

[0142] Table 2 Maximum horizontal principal stress and minimum horizontal principal stress of Wells 1 to 6

[0143] And the simulation results of the horizontal maximum principal stress azimuth

[0144]

[0145] Table 3 Maximum horizontal principal stress and minimum horizontal principal stress of Wells 1 to 6

[0146] And the error between the simulation result and the measured result of the horizontal maximum principal stress azimuth

[0147]

[0148] like Fig.11 The present application also provides a system for determining boundary conditions for numerical simulation of tectonic stress field. The system includes:

[0149] A determination module is used to determine the test range of the direction and magnitude of the external force applied to the heterogeneous geomechanical model according to the magnitude and direction of the measured ground stress in a single well;

[0150] An acquisition module is used to select a number of test points at equal intervals within the test range to carry out numerical simulation and obtain the error between the single well simulation result and the measured data under each boundary condition;

[0151] A determination module is used to determine whether the minimum error of the obtained simulation results meets the research needs and decide whether the force direction needs to be adjusted;

[0152] The simulation module conducts numerical simulations with optimal boundary conditions and obtains relevant parameters of the tectonic stress field.

[0153] The system for determining boundary conditions of numerical simulation of tectonic stress field provided in the embodiment of the present application is used to implement the method for determining boundary conditions of numerical simulation of tectonic stress field mentioned above. The specific definition of the system for determining boundary conditions of numerical simulation of tectonic stress field can refer to the definition of the method for determining boundary conditions of numerical simulation of tectonic stress field mentioned above, which will not be repeated here. The various parts in the system for determining boundary conditions of numerical simulation of tectonic stress field mentioned above can be implemented in whole or in part by software, hardware and a combination thereof. The above modules can be embedded in or independent of the processor in the device in the form of hardware, or can be stored in the memory in the device in the form of software, so that the processor can call and execute the operations corresponding to the above modules.

[0154] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0155] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be construed as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent application shall be subject to the attached claims.

Claims

1. A method for determining boundary conditions for numerical simulation of tectonic stress field, characterized in that: The method comprises: S1. According to the magnitude and direction of the measured ground stress in a single well, the test range of the direction and magnitude of the external force applied to the heterogeneous geomechanical model is clarified; S2. Select several test points at equal intervals within the test range to carry out numerical simulation and obtain the error between the single well simulation result and the measured data under each boundary condition; S3, determining whether the minimum error of the obtained simulation results meets the research needs and deciding whether the force direction needs to be adjusted; S4. Carry out numerical simulation using the optimal boundary conditions and obtain relevant parameters of the tectonic stress field; Step S1 includes: S11. Taking the average of the azimuths of the measured horizontal maximum principal stresses of all single wells as the direction of application of the horizontal maximum principal stress of the geomechanical model, the direction perpendicular to the direction of application of the horizontal maximum principal stress is the direction of application of the horizontal minimum principal stress; S12, the maximum horizontal principal stress σ measured from all single wells H and the magnitude of the minimum horizontal principal stress σ h The maximum and minimum values ​​are obtained respectively, and the maximum horizontal principal stress σ H The maximum value of σ H-max , the minimum value is σ H-min , the minimum horizontal principal stress σ h The maximum value of σ h-max , the minimum value is σ h-min ; S13, determining the test range of the horizontal principal stress of the geomechanical model according to the maximum and minimum values ​​of the measured horizontal maximum principal stress of the single well and the maximum and minimum values ​​of the measured horizontal minimum principal stress; S14, when Bound σH-LOWER or Bound σH-UPPER With σ H-max and σ H-min When they are different in positive and negative, they are taken as 0. σh-LOWER or Bound σh-UPPER With σ h-max and σ h-min When the numbers are different in positive and negative, they are also 0; Among them, Bound σH-LOWER Indicates the lower limit of the force test range in the direction of the maximum horizontal principal stress. σH-UPPER Indicates the lower limit of the force test range in the direction of the maximum horizontal principal stress. σh-LOWER Indicates the lower limit of the force test range in the horizontal minimum principal stress direction, Bound σh-UPPER Indicates the upper limit of the test range of force magnitude in the horizontal minimum principal stress direction.

2. The method according to claim 1, characterized in that In step S13, according to the parameter σ obtained in step S12 H-max , σ H-min , σ h-max and σ h-min ; The lower limit of the force test range of the geomechanical model in the direction of the maximum horizontal principal stress is Bound σH-LOWER Set as σ H-min +(σ H-max -σ H-min ) / 4, upper bound σH-UPPER Set as σ H-max +(σ H-max -σ H-min ) / 4, the lower limit of the force test range of the geomechanical model in the horizontal minimum principal stress direction is Bound σh-LOWER Set as σ h-min -(σ h-max -σ h-min ) / 4, upper bound σh-UPPER Set as σ h-max -(σ h-max -σ h-min ) / 4.

3. The method according to claim 1, characterized in that Step S2 includes: S21. Test range of maximum principal stress applied horizontally Bound σH-LOWER To Bound σH-UPPER According to the research accuracy requirements, m test points σ are selected at equal intervals. H-i , that is, i is an integer from 1 to m; S22, Test range of minimum principal stress applied horizontally Bound σh-LOWER To Bound σh-UPPER According to the research accuracy requirements, m test points σh-j are selected at equal intervals, that is, j is an integer from 1 to m; S23, the combination of m test values ​​of the maximum horizontal principal stress and m test values ​​of the minimum horizontal principal stress can form a total of m 2 The boundary conditions of applying external force are realized by using the command flow of numerical simulation software. 2 The boundary conditions for applying external forces (σ H-i, σ h-j ) and obtain the error between the simulated value and the measured value under each boundary condition.

4. The method according to claim 3, characterized in that In step S21, the horizontal maximum principal stress test range Bound σH-LOWER To Bound σH-UPPER Divided into (m-1) parts on average, i.e. the i-th test value σ of the horizontal maximum principal stress H-i for: Wherein i is an integer from 1 to m.

5. The method according to claim 3, characterized in that: In step S22, the horizontal minimum principal stress test range Bound σh-LOWER To Bound σh-UPPER Divide into (m-1) parts on average, i.e. the jth test value σ of the horizontal minimum principal stress h-j for: Wherein j is an integer from 1 to m.

6. The method according to claim 3, characterized in that In step S23, each numerical simulation can obtain the maximum horizontal principal stress and the minimum horizontal principal stress, and then obtain the simulated values ​​of the maximum horizontal principal stress and the minimum horizontal principal stress of a single well; Assuming that the total number of wells is n, the measured value and simulated value of the horizontal maximum principal stress of the kth well are σ H-mea-k and σ H-sim-k , the measured and simulated values ​​of the horizontal minimum principal stress are σ h-mea-k and σ h-sim-k , then the boundary condition (σ H-I ,σ h-j ) The error between the simulated value and the measured value of the stress magnitude σ(σH-i,σh-j) for: Among them, Error σ(σH-i,σh-j) Used to characterize the boundary conditions (σ H-I ,σ h-j ) The error between the simulated value and the measured value of the stress magnitude corresponding to each numerical simulation can obtain the sum of the components of the horizontal principal stress on the X-axis and Y-axis. Assuming that the sum of the components of the simulated value of the horizontal principal stress of the kth well on the X-axis and Y-axis are denoted as σ X-k and σ Y-k , assuming that the simulated value of the azimuth of the horizontal maximum principal stress is α sim-k , then we have: If the azimuth of the measured maximum horizontal principal stress is α mea-k , then with the boundary condition (σ H-i ,σ h-j ) The error between the simulated value and the measured value of the horizontal maximum principal stress azimuth α(σH-i,σh-j) Defined as: Using alpha sim-k The tangent value of is used to calculate the error of the simulated value of the horizontal maximum principal stress azimuth angle; α sim-k With α mea-k The absolute value of the difference |α sim-k -α mea-k | directly reflects the error of the simulation value, and the tangent value of the difference tan(|α sim-k -α mea-k |) is: Tangent value of the error between the simulated value and the measured value of the maximum principal stress azimuth Error` tanα(σH-I,σh-j) Defined as: |α sim-k -α mea-k | Available through arctan[Error` tanα(σH-i,σh-j) ] is solved, and |α sim-k -α mea-k The ratio of the average value of | to 45° can reflect the error rate between the simulated value and the measured value of the horizontal maximum principal stress azimuth Error`` α(σH-i,σh-j) ,Right now: The above tanα sim-k Substitute the formula into this formula to get: Error rate between the simulated value and the measured value of the comprehensive horizontal maximum principal stress azimuth Error`` α(σH-i,σh-j) Error between simulated and measured stress values σ(σH-i,σh-j) The comprehensive error determination formula of stress magnitude and direction can be obtained, namely Error (σH-i,σh-j) equal: Error (σH-i，σh-j) =(Error σ(σH-i，σh-j) +Error″ α(σH-i，σh-j) ) / 2 Among them, Error (σH-i,σh-j) Used to characterize the error between the simulated value and the measured value of stress magnitude.

7. The method according to claim 1, characterized in that Step S3 includes: S31. Get Error (σH-i,σh-j) The minimum value of Error min and the corresponding (σ H-i ,σ h-j ); Error (σH-i,σh-j) It is used to characterize the error between the simulated value and the measured value of stress magnitude; S32. If Error (σH-i,σh-j) The minimum value of Error min The upper limit of the error allowed by the study has been met, so the corresponding (σ H-i ,σ h-j ) can be used as the optimal boundary condition and go to step S4; if the minimum value Error min The error limit allowed by the study and the minimum value Error min The corresponding boundary conditions (σ H-i ,σ h-j ) H-i Not equal to Bound σH-LOWER or Bound σH-UPPER , and σ h-j Not equal to Bound σh-LOWER or Bound σh-UPPER , which indicates that the optimal boundary condition (σ H-i ,σ h-j ) is not at the boundary of the test range, the error does not need to be reduced by adjusting the horizontal principal stress applied to the model, but by adjusting the direction of application of the horizontal principal stress, and then go to step S33; if the minimum value Error min The error limit allowed by the research is exceeded, and at least one of the following four conditions is met: (1) Minimum Error min The corresponding boundary conditions (σ H-i ,σ h-j ) H-i Equal to Bound σH-LOWER ; (2) Minimum Error min The corresponding boundary conditions (σ H-i ,σ h-j ) H-i Equal to Bound σH-UPPER ; (3) Minimum Error min The corresponding boundary conditions (σ H-i ,σ h-j ) h-j Equal to Bound σh-LOWER ; (4) Minimum Error min The corresponding boundary conditions (σ H-i ,σ h-j ) h-j Equal to Bound σh-UPPER ; This indicates that the optimal boundary condition (σ H-i ,σ h-j ) is at the boundary of the test range, the error needs to be reduced by adjusting the horizontal principal stress applied to the model, and the process goes to step S34; S33, the difference between the average value of the simulated value of the horizontal maximum principal stress azimuth at each well location and the average value of the measured value △α (σ H-i ,σ h-j )for: The azimuth angle currently used in step S11 to apply the horizontal maximum principal stress to the model Add △α(σ H-i ,σ h-j ) is used as the adjusted azimuth angle of the maximum horizontal principal stress applied to the model, that is, As the new azimuth angle for applying the maximum horizontal principal stress to the model, the azimuth angle perpendicular to the direction is the azimuth angle for applying the minimum horizontal principal stress to the model, and the process goes to step S12 and is executed in sequence; S34: Take one of the following measures corresponding to the four situations in step S32: (1) Use Bound σH-LOWER -(σ H-max -σ H-min ) instead of Bound σH-LOWER As the lower limit of the force test range of the model in the direction of the maximum horizontal principal stress, use Bound σH-UPPER -(σ H-max -σ H-min ) instead of Bound σH-UPPER As the upper limit of the test range; (2) Use Bound σH-LOWER +(σ H-max -σ H-min ) instead of Bound σH-LOWER As the lower limit of the force test range of the model in the direction of the maximum horizontal principal stress, use Bound σH-UPPER +(σ H-max -σ H-min ) instead of Bound σH-UPPER As the upper limit of the test range; (3) Use Bound σh-LOWER -(σ h-max -σ h-min ) instead of Bound σh-LOWER As the lower limit of the force test range of the model in the horizontal minimum principal stress direction, use Bound σh-UPPER -(σ h-max -σ h-min ) instead of Bound σh-UPPER As the upper limit of the test range; (4) Use Bound σh-LOWER +(σ h-max -σ h-min ) instead of Bound σh-LOWER As the lower limit of the force test range of the model in the horizontal minimum principal stress direction, use Bound σh-UPPER +(σ h-max -σ h-min ) instead of Bound σh-UPPER As the upper limit of the test range; go to step S14 and execute in sequence.

8. The method according to claim 1, characterized in that: In step S4, the optimal boundary condition (σ H-j ,σ h-j ) Carrying out numerical simulation of stress field can obtain the best numerical simulation results and conduct research on stress magnitude and direction.

9. A system for determining boundary conditions for numerical simulation of tectonic stress field, characterized in that: The system comprises: A determination module is used to determine the test range of the direction and magnitude of the external force applied to the heterogeneous geomechanical model according to the magnitude and direction of the measured ground stress in a single well; An acquisition module is used to select a number of test points at equal intervals within the test range to carry out numerical simulation and obtain the error between the single well simulation result and the measured data under each boundary condition; A determination module is used to determine whether the minimum error of the obtained simulation results meets the research needs and decide whether the force direction needs to be adjusted; The simulation module uses the optimal boundary conditions to carry out numerical simulation and obtain relevant parameters of the tectonic stress field; The modules are determined to include: The average azimuth of all measured horizontal maximum principal stresses of single wells is taken as the direction of application of horizontal maximum principal stress of geomechanics model, and the direction perpendicular to the direction of application of horizontal maximum principal stress is the direction of application of horizontal minimum principal stress; From the maximum horizontal principal stress σ measured in all single wells H and the magnitude of the minimum horizontal principal stress σ h The maximum and minimum values ​​are obtained respectively, and the maximum horizontal principal stress σ H The maximum value of σ H-max , the minimum value is σ H-min , the minimum horizontal principal stress σ h The maximum value of σ h-max , the minimum value is σ h-min ; According to the maximum and minimum values ​​of the measured horizontal maximum principal stress of a single well, as well as the maximum and minimum values ​​of the measured horizontal minimum principal stress, the test range of the horizontal principal stress of the geomechanical model is determined; When Bound σH-LOWER or Bound σH-UPPER With σ H-max and σ H-min When they are different in positive and negative, they are taken as 0. σh-LOWER or Bound σh-UPPER With σ h-max and σ h-min When the numbers are different in positive and negative, they are also 0; Bound σH-LOWER Indicates the lower limit of the force test range in the direction of the maximum horizontal principal stress. σH-UPPER Indicates the lower limit of the force test range in the direction of the maximum horizontal principal stress. σh-LOWER Indicates the lower limit of the force test range in the horizontal minimum principal stress direction, Bound σh-UPPER Indicates the upper limit of the test range of force magnitude in the horizontal minimum principal stress direction.

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