A method for predicting the location of casing deformation induced by fracturing based on multi-dimensional information

Abstract

The present invention provides a method for predicting the position of casing deformation induced by fracturing based on multi-dimensional information, comprising the following steps: establishing a fine geostress field of a block; establishing a finite element model of geology-fracturing engineering-cement ring-casing integration, and calculating the initial stress distribution of the casing string before fracturing; calculating the change of the geostress field after reservoir fracturing and the stress distribution of the casing string; performing casing deformation analysis combining geology-cementing-casing of horizontal wells; predicting the position of the abnormal bulge of the gamma curve, the position of the abnormal cementing homogeneity, the maximum shear load point caused by the fracturing section where the construction pressure peak is located, and the outer edge of the formation crushing zone caused by fracturing as the position of the casing deformation. The present invention predicts the position of casing deformation induced by fracturing by combining multiple factors, with a high prediction rate and strong operability.

Description

Technical Field

[0001] The present invention relates to the technical field of shale gas development, and in particular to a method for predicting the position of casing deformation induced by fracturing based on multi-dimensional information. Background Art

[0002] The shale gas geological structure is complex in high-stress areas such as the Sichuan Basin in my country and similar structures. The maximum horizontal principal stress of the reservoir is close to or even higher than the overlying rock pressure. Affected by multiple factors and the superposition of multiple factors, the probability of casing deformation is relatively large, and the fracturing process is the most intuitive manifestation.

[0003] In the existing technology, although relevant research on casing deformation has been carried out at home and abroad, most of them adopt a single factor, or emphasize geological factors, or emphasize design factors. The conclusions formed are relatively simple and limited, and the accuracy of predicting the casing deformation position is not high.

[0004] For example, the patent application document entitled "A method and device for determining the deformation area of ​​a fracturing casing" and published on December 7, 2016 and with the publication number CN 106199712 A records a method and device for determining the deformation area of ​​a fracturing casing. The method determines the shear wave velocity of the strata in the preset study area and the constraints between the shear wave velocity and the stratum density and the longitudinal wave velocity by establishing a rock physics model that matches the seismic elements of the preset study area, and uses the constraints to perform prestack elastic parameter inversion on the seismic data to determine the plane distribution of the maximum curvature attribute, and finally determines the deformation area of ​​the fracturing casing based on the plane distribution. The method inverts the seismic data to infer the deformation area of ​​the fracturing casing, but the seismic data is easily disturbed by geological factors, and the analysis results have certain errors, and it is impossible to judge the accuracy of the predicted casing deformation area.

[0005] The patent application document entitled "Calculation Method for Wellbore Casing Variables of Hydraulically Fractured Horizontal Wells in Naturally Fractured Shale Formations" and published on November 24, 2020 with the publication number CN 111980697 A describes a method for calculating wellbore casing variables of hydraulically fractured horizontal wells in naturally fractured shale formations. The method is based on a complex function method to establish an analytical model of the I-II composite fracture displacement field with superimposed fluid pressure to obtain the tangential relative displacement of the fracture, and then determine the wellbore casing variables based on the tangential relative displacement of the fracture. However, the patent application only provides a method for calculating casing variables using the model, and does not provide specific technical measures to reduce casing variables.

[0006] The scale of shale gas exploitation in high geostress areas is not very large internationally, and there is little research on fracturing-induced casing deformation in the area, which also leads to low accuracy in predicting casing deformation.

[0007] Therefore, it is necessary to form a set of prediction methods for the deformation position of shale gas casing in high-stress areas in order to propose practical technical measures and develop technical solutions for casing deformation prediction and prevention. Summary of the invention

[0008] The purpose of the present invention is to solve at least one of the above-mentioned deficiencies in the prior art. For example, the purpose of the present invention is to provide a method for predicting the deformation position of shale gas casing in high geostress areas (e.g., Sichuan Basin or similar areas) based on multi-dimensionality.

[0009] In order to achieve the above-mentioned purpose, the present invention provides a method for predicting the position of casing deformation induced by fracturing based on multi-dimensional information, comprising the following steps: based on the well logging data of the target block, obtaining the geological analysis results of a single well and the direction angle of the maximum horizontal principal stress, and establishing a fine geostress field of the block; based on the fine geostress field of the block, establishing a finite element model integrating geology, fracturing engineering, cement sheath and casing, performing three-dimensional finite element deformation and stress analysis on the casing string of the entire horizontal section of the horizontal well, and obtaining the initial stress distribution of the casing string before fracturing; performing three-dimensional finite element deformation and stress analysis on the casing string after fracturing the reservoir, calculating the changes in the geostress field caused by fracturing, and finding the position where the shear load is applied to the casing. distribution; conducting an integrated casing deformation analysis combining geology, cementing and casing of horizontal wells, the analysis includes gamma curve distribution analysis of the horizontal section of the well trajectory, cementing quality and acoustic amplitude curve distribution analysis of the horizontal section of the well trajectory, fracturing construction pressure curve analysis of the horizontal section of the well trajectory, microseismic monitoring results analysis of the horizontal well, and simulated calculation of the change of shear force outside the wellbore in the horizontal section of the well trajectory; predicting the position of casing deformation induced by fracturing based on the results of the casing deformation analysis, the position of the casing deformation includes the position of the local abnormal protrusion of the gamma curve, the position of the cementing homogeneity anomaly, the maximum shear load point caused by the fracturing section where the construction pressure peak is located, and the outer edge of the formation crushing zone caused by fracturing.

[0010] In an exemplary embodiment of the present invention, the establishment of a fine geostress field of a block may include the following steps: according to the technical method of "well-seismic combination", based on seismic wave data, combined with single well layer information, a three-dimensional geological model of the target block is established; according to the logging data of a single well in the target block, rock mechanical parameters are calculated, and single well geomechanical analysis is performed on other logging data and rock mechanical parameters to obtain single well geological analysis results; comprehensive analysis of information on the world stress map, single well measurement information of existing wells, and microseismic monitoring information of horizontal well fracturing in the target block is performed to obtain the maximum horizontal principal stress direction angle in the target block; a three-dimensional geological model is introduced to establish a finite element model of the geostress field of the target block, and based on the single well geological analysis results and the microseismic measurement results of the existing wells during the fracturing construction, the simulation results of the geostress field of the target block are verified, and the verified qualified numerical solution of the geostress field is constructed as a fine geostress field of the block.

[0011] In an exemplary embodiment of the present invention, the three-dimensional geological model of the target block is established based on the seismic wave data and combined with the single well layer information, which may include: establishing the grid geometry of the geological model according to the three-dimensional seismic wave data, dividing the strata and defining the grid unit size of each stratum, wherein the grid unit of the stratum where the reservoir is located is smaller than the grid unit of other strata.

[0012] In an exemplary embodiment of the present invention, the ratio of the grid unit thickness of the formation where the reservoir is located to the grid unit thickness of the other formations may be 1:18 to 1:30.

[0013] In an exemplary embodiment of the present invention, the other logging data may include gamma rays, compression acoustic wave duration and density of the formation, and the rock mechanics parameters may include Young's modulus, Poisson's ratio, cohesion and internal friction angle.

[0014] In an exemplary embodiment of the present invention, the single well geological analysis results may include geostress results obtained by indirect analysis using other logging data and geostress results obtained by direct calculation using rock mechanics parameters.

[0015] In an exemplary embodiment of the present invention, the comprehensive analysis of the information of the world stress map, the single well measurement information of the existing wells, and the microseismic monitoring information of the horizontal well fracturing in the target block to obtain the maximum horizontal principal stress direction angle in the target block may include: using the world stress map to determine the maximum horizontal principal stress direction angle in the area to which the target block belongs, and clarifying the interval range to which the maximum horizontal principal stress direction angle in the target block belongs; judging the interval range to which the maximum horizontal principal stress direction angle in different structural parts in the target block belongs based on the information measured by the single well, and clarifying the change law of the maximum horizontal principal stress direction angle in the target block with the terrain; analyzing the microseismic monitoring information, and verifying and correcting the value of the maximum horizontal principal stress direction angle in the target block summarized by using the world stress map and the single well measurement information in combination with the analysis results of the microseismic monitoring information, and / or supplementing and correcting the value of the maximum horizontal principal stress direction angle in the target block in the area omitted by using the world stress map and the single well measurement information.

[0016] In an exemplary embodiment of the present invention, the analysis of microseismic monitoring information may include: determining the position where a single-color strip distribution appears in the microseismic event points of the horizontal wells in the target block as a fracture network strip generated by the same fracturing stage, and determining the direction angle of the fracture network strip as the direction angle of the maximum horizontal principal stress at the position; determining the position where a color strip composed of multiple colors appears in the microseismic event points of the horizontal wells in the target block and the event point distribution exceeds the reservoir range as the position of a natural fracture; determining the situation where microseismic response points appear in the microseismic event points of the horizontal wells in the target block in a sheet-like or cluster-like distribution as the position where the maximum horizontal principal stress directionality is not obvious, and the minimum horizontal principal stress direction is close to the vertical principal stress direction.

[0017] In an exemplary embodiment of the present invention, the establishment of a finite element model of the geostress field of the target block may include: setting the unit used in the geological model grid to a three-dimensional 8-node linear unit, setting the load of the geostress field finite element model to a gravity load, setting the boundary conditions of the four sides and the bottom of the geostress field finite element model to normal displacement constraints, setting the boundary conditions of the top to a free boundary, and setting the initial geostress parameters and the initial pore pressure parameters to initial conditions.

[0018] In an exemplary embodiment of the present invention, the initial geostress parameters may include the triaxial geostress principal components and the maximum horizontal principal stress direction angle obtained by single well geomechanical analysis.

[0019] In an exemplary embodiment of the present invention, the simulation results of the geostress field of the target block are verified based on the geological analysis results of the single well and the actual microseismic measurement results of the existing wells during the fracturing construction, and the verified numerical solution of the geostress field is constructed as a fine geostress field of the block, which may include: for each single well in the target block, using the geostress results obtained by indirect analysis of other logging data and the geostress results obtained by direct calculation using rock mechanics parameters as initial geostress parameters, performing numerical simulation of the geostress field of the target block, and obtaining the corresponding numerical solution of the geostress field; comparing the errors between the above two numerical solutions of the geostress field and the actual measured values ​​of the geostress field of the existing well fracturing construction, and taking the numerical solution with the smaller error with the actual measured value of the geostress field as the fine geostress field of the block.

[0020] In an exemplary embodiment of the present invention, a basis for determining whether the gamma curve has a local abnormal protrusion is that the local gamma value is greater than 200 GAPI.

[0021] In an exemplary embodiment of the present invention, the determination basis of abnormal cementing homogeneity may be that the local acoustic amplitude is higher than the interface with poor cement bonding, and the local evaluation result of cementing quality is poor.

[0022] In an exemplary embodiment of the present invention, the maximum shear load point caused by the fracturing section where the construction pressure peak value is located may be determined based on the fact that the pressure curve surges or drops by more than 10 MPa / min and the pressure curve is not a straight line.

[0023] In an exemplary embodiment of the present invention, the location of the formation fracture zone caused by the fracturing can be determined by geological data before the fracturing and / or numerical simulation of reservoir fracturing.

[0024] Compared with the prior art, the beneficial effects and advantages of the present invention include at least one of the following:

[0025] (1) The present invention inputs the well logging data and rock mechanics parameters of a single well into the geostress field model for simulation calculation, and repeatedly compares and verifies the simulation results with the microseismic data during the actual fracturing, thereby obtaining a fine geostress field that can more realistically reproduce the geostress field distribution and fracture direction of the target block;

[0026] (2) The present invention uses the block's fine geostress field as input data for subsequent fracturing and casing deformation simulation, eliminating the uncertainty of model input parameters caused by large logging data errors or insufficient measured parameters in the prior art, ensuring the accuracy of the input geostress field and improving the accuracy of predicting casing deformation position using the finite element model of geology-fracturing engineering-cement sheath-casing integration;

[0027] (3) The present invention comprehensively analyzes various factors that affect the deformation of the fracturing casing, organically links various factors of casing deformation, conducts a comprehensive integrated analysis, and predicts the location of casing deformation induced by fracturing in high ground stress areas in a targeted manner, which is conducive to the subsequent proposal of practical technical measures and the development of casing deformation prediction and prevention technical solutions;

[0028] (4) The prediction method of the present invention is based on well logging data and has good operability;

[0029] (5) The prediction method of the present invention is used to analyze the location of casing deformation, and the prediction results are consistent with more than 85% of fracturing casing deformation cases, with high accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A calculation flow chart of a method for predicting the position of casing deformation induced by fracturing based on multi-dimensional information in an exemplary embodiment of the present invention is shown.

[0031] Figure 2 A calculation flow chart for establishing a block detailed geostress field in an exemplary embodiment of the present invention is shown.

[0032] Figure 3 A schematic structural diagram of a three-dimensional geological model of the Wei 202 block in an exemplary embodiment of the present invention is shown.

[0033] Figure 4A A diagram showing the well logging data of the Wei 202 vertical well in an exemplary embodiment of the present invention is shown; Figure 4B A rock mechanical parameter diagram of the Wei 202 vertical well in an exemplary embodiment of the present invention is shown.

[0034] Figure 5 A single well geological analysis result diagram of the Wei 202 vertical well in an exemplary embodiment of the present invention is shown.

[0035] Figure 6 The diagram shows the distribution of the maximum horizontal principal stress direction angles on 13 single wells in the Weiyuan area in an exemplary embodiment of the present invention.

[0036] Fig. 7A A microseismic information diagram of the Wei 202 well area in an exemplary embodiment of the present invention is shown; Figure 7B A microseismic information diagram of the Wei 204 well area in an exemplary embodiment of the present invention is shown; Figure 7C A diagram showing the fracturing microseismic information of the Wei 202H10-3 horizontal well in an exemplary embodiment of the present invention is shown; Fig.7D The microseismic monitoring information of Wei 204H1-5 in an exemplary embodiment of the present invention is shown.

[0037] Figure 8 A mesh diagram of a finite element model of the geostress field of the Wei 202 block in an exemplary embodiment of the present invention is shown.

[0038] Fig. 9 A distribution diagram of the maximum horizontal principal compressive stress direction in the Wufeng Formation-Longmaxi Formation of the Wei 202 block in an exemplary embodiment of the present invention is shown.

[0039] Fig. 10A A distribution diagram of the minimum horizontal principal stress direction in the Wufeng Formation-Longmaxi formation in the Wei 202 block in an exemplary embodiment of the present invention is shown; Fig. 10B The distribution diagram of the intermediate principal stress direction in the Wufeng Formation-Longmaxi formation in the Wei 202 block is shown; Fig. 10C The three-dimensional vector direction distribution map of the intermediate principal stress in the Wufeng Formation-Longmaxi formation in the Wei 202 block is shown.

[0040] Fig.11 A distribution cloud diagram of the three-dimensional numerical solution of the geostress field of the reservoir unit of the Wei 202 vertical well in an exemplary embodiment of the present invention is shown.

[0041] Fig.12 A casing damage curve and a gamma logging curve diagram in an exemplary embodiment of the present invention are shown.

[0042] Fig.13 A cementing quality acoustic amplitude and evaluation diagram in an exemplary embodiment of the present invention is shown.

[0043] Fig.14 A fracturing operation curve diagram in an exemplary embodiment of the present invention is shown.

[0044] Fig.15 A well ant body diagram is shown in one exemplary embodiment of the present invention. DETAILED DESCRIPTION

[0045] Hereinafter, the method for predicting the position of casing deformation induced by fracturing based on multi-dimensional information of the present invention will be described in detail in conjunction with exemplary embodiments and accompanying drawings.

[0046] In an exemplary embodiment of the present invention, the present invention provides a method for predicting the location of casing deformation induced by fracturing based on multi-dimensional information.

[0047] In this embodiment, Figure 1 The calculation flow chart of the method for predicting the location of casing deformation induced by fracturing based on multi-dimensional information is shown in Figure 2. Figure 1 As shown, a method for predicting the location of casing deformation induced by fracturing based on multi-dimensional information may include the following steps:

[0048] Step S1: Based on the well logging data of the target block, the single well geological analysis results and the maximum horizontal principal stress direction angle are obtained to establish a fine geostress field of the block.

[0049] Here, if Figure 2 As shown, analyzing the well logging data of the target block and establishing the fine geostress field of the block may include the following steps:

[0050] Step S11, according to the technical method of "well-seismic combination" (i.e., the combination of well logging and seismic), based on the seismic wave data and combined with the single well layer information, a three-dimensional geological model of the target block is established.

[0051] Specifically, in combination with the structural undulation characteristics of the target block, on the basis of three-dimensional seismic wave data, the overall geometry and grid size of the target block can be constructed, and then combined with the single well stratigraphic information of the existing wells in the target block, the stratigraphic information of the target block can be delineated, the geometry and grid size of the stratum where the reservoir is located and other strata outside the reservoir can be determined, and a three-dimensional geological model of the target block can be obtained.

[0052] Here, the specific implementation of establishing a three-dimensional geological model of the target block may include: establishing the grid geometry of the geological model according to the three-dimensional seismic wave data, dividing the strata and defining the grid unit size of each stratum, wherein the grid unit of the stratum where the reservoir is located is smaller than the grid unit of other strata. The ratio of the grid unit thickness of the stratum where the reservoir is located to the grid unit thickness of the other strata may be 1:18 to 1:30. For example, the grid unit thickness of other strata may be 20 times the grid unit thickness of the stratum where the reservoir is located.

[0053] The field application of the Wei 202 block, a three-dimensional shale gas block in Weiyuan area, is taken as an example to illustrate.

[0054] The ground structure pattern of the shale gas three-dimensional block in the Weiyuan area is consistent, the structure is simple, the northwest is high and the southeast is low, and the axis is nearly east-west. The Wei I high point is mainly present in the central and northern parts of the three-dimensional block, and the southern part is the southern wing of the Weiyuan structure. Faults are rare and the fault drop is small. From the limb intercalated shale structure of the Shaximiao Formation in the Middle Jurassic System, it can be seen that the structure in the three-dimensional block is simple, the faults are not developed, the central and northern parts are the Wei I high point of the Weiyuan structure, and there are three secondary high points on the Wei I high point, with an axis of nearly east-west; the southern part of the three-dimensional area is the southern wing of the Weiyuan structure. The structure pattern of the ground is generally consistent with the surface, but there are certain changes in local structural details, the folds are relatively enhanced, and the faults are relatively developed. Due to the small drop of the fault, its impact on the initial distribution of the geostress field is not significant. In addition, due to the small drop of the fault, it is difficult to identify the fault through seismic wave data, and some faults with very small drop are difficult to identify.

[0055] According to the field data, the length of the Wei 202 block is 19km and the width is 13.5km. Based on the three-dimensional seismic wave data, the three-dimensional geological model of the Wei 202 block was established. Combined with the stratigraphic sequence of the single well area, the geological model was divided into 7 layers, from top to bottom: the ground to the bottom of the Jialingjiang Formation, the bottom of the Jialingjiang Formation to the bottom of the Feixianguan Formation, the bottom of the Feixianguan Formation to the bottom of the Upper Permian, the bottom of the Upper Permian to the bottom of the Lower Permian, the bottom of the Lower Permian to the bottom of the Wufeng Formation (including the Longmaxi Formation), the bottom of the Wufeng Formation to the bottom of the Cambrian, and the bottom of the Cambrian to an altitude of -5,500 meters. Among them, the reservoir is located in the Wufeng Formation-Longmaxi Formation.

[0056] Considering the optimization of finite element calculation, a denser grid is divided in the Wufeng Formation-Longmaxi Formation (that is, the formation where the reservoir is located) compared with the grids of other formations. That is, the grid of the Wufeng Formation-Longmenxi Formation is 20 layers, with a minimum unit thickness of 1 meter, while other formations use larger unit sizes. The total number of units used in the geological model of the Wei 202 block is 121,068. Due to the influence of stratum denudation, no distinction is made between the Wufeng Formation and the Longmaxi Formation, and the two are regarded as one formation.

[0057] Figure 3 The schematic diagram of the three-dimensional geological model of the Wei 202 block (depth unit, meter) is shown in the figure. The geometric shape and grid of the reservoir are given in the figure, showing a northwest high-southeast low structure. The grids of different depth colors from top to bottom in the figure represent the ground to the bottom of the Jialingjiang Formation, the bottom of the Jialingjiang Formation to the bottom of the Feixianguan Formation, the bottom of the Feixianguan Formation to the bottom of the Upper Permian, the bottom of the Upper Permian to the bottom of the Lower Permian, the bottom of the Lower Permian to the bottom of the Wufeng Formation (including the Longmaxi Formation), the bottom of the Wufeng Formation to the bottom of the Cambrian, and the bottom of the Cambrian to -5500 meters above sea level.

[0058] Step S12: Calculate rock mechanical parameters according to the logging data of a single well in the target block, perform single well geomechanical analysis on other logging data and rock mechanical parameters, and obtain single well geological analysis results.

[0059] The other logging data may include gamma rays, compression acoustic wave duration and density of the formation. The rock mechanical parameters include Young's modulus, Poisson's ratio, cohesion (adhesion) and internal friction angle. Using empirical formulas and related calculation principles, rock mechanical parameters such as Young's modulus can be calculated based on acoustic logging data. For example, the rock mechanical parameters such as Young's modulus can be calculated using the following related formulas (Formula (1) to Formula (4)).

[0060] E=10 3 ρ b· [3(V s / V p ) 2 -4] / Vs 2[(V s / V p ) 2 -1] Formula (1)

[0061] v=0.5[(V s / V p ) 2 -2] / [(V s / V p ) 2 -1] Formula (2)

[0062] C = 4.69433 × 10 7 V p 4 ρ b [(1+v) / (1-v)](1-2v)(1+0.78V sh ) Formula (3)

[0063]

[0064] Where, E is Young's modulus, MPa; ρ b is the rock density, g / cm 3 ; Vs is longitudinal wave, us / m; Vp is transverse wave, us / m; v is Poisson's ratio, dimensionless; C is cohesion, MPa; V sh is the mud content, %; is the internal friction angle, degrees.

[0065] The single well geological analysis results may include the geostress results obtained by indirect analysis using other well logging data and the geostress results obtained by direct calculation using rock mechanics parameters. The geostress results obtained by indirect analysis using other well logging data may include the maximum horizontal principal stress obtained by indirect analysis using other well logging data, the minimum horizontal principal stress obtained by indirect analysis using other well logging data, the vertical principal stress obtained by indirect analysis using other well logging data, and the formation pore pressure obtained by indirect analysis using other well logging data. The geostress analysis results obtained by direct calculation using rock mechanics parameters include the maximum horizontal principal stress obtained by direct calculation using rock mechanics parameters, the minimum horizontal principal stress obtained by direct calculation using rock mechanics parameters, the vertical principal stress obtained by direct calculation using rock mechanics parameters, and the formation pore pressure obtained by direct calculation using rock mechanics parameters.

[0066] The following is an example of the field application of the Weiyuan area shale gas three-dimensional block Wei 202.

[0067] Figure 4A , Figure 4B and Figure 5The single well geological analysis results are obtained after single well geomechanical analysis is performed on the Wei 202 block using the method in step S12. Figure 4A and Figure 4B These are the well logging data of a vertical well in the Wei 202 block and the rock mechanical parameters calculated based on the acoustic logging data. The maximum inclination of the lower well trajectory of this well is 8.6 degrees. Figure 4A The left column is the gamma ray of the formation (unit: API), the second column from the left is the compressed sound wave duration DC (unit: microseconds / foot), the third column from the left is the wellbore (unit: inch hour), the right column is the density (unit: g / cc), and the second column from the right is the sound wave duration (unit: milliseconds / foot). Figure 4B The left column is the value curve of the elastic modulus of the lower section of Wei 202 (unit: Mpsi), the second left column is the value curve of Poisson's ratio, the right column is the bonding strength of the formation material (unit: MPa), and the second right column is the internal friction angle (unit: degree), among which the bonding strength and internal friction angle are the main parameters used to calculate the collapse pressure according to the Mohr-Coulomb condition.

[0068] Figure 5 The single well geological analysis results of Wei 202 vertical well, among which, Figure 5 The left column shows the engineering gradient form of the main component results of the in-situ stress of the Wei 202 vertical well analysis. Figure 5 The right column is a full display of the ground stress analysis results of a single well. The icon corresponding to curve a in the figure is the line segment ShG Elastic (w202), the icon corresponding to curve b is the line segment SHG-ShG-OBG (w202), the icon corresponding to curve c is the line segment SFG Mohr-Coulomb (w202), the icon corresponding to curve d is the line segment PPdt e3 (w202), the icon corresponding to curve e is the line segment OBG rhob (w202), the icon corresponding to point A is the square ShGmin (w202), the icon corresponding to point B is the square SHmax (w202), the icon corresponding to point D is the square PP (w202), and the icon corresponding to point E is the square OBG-m (w202).

[0069] Figure 5The meanings of the icons of the curves in the figure are as follows: the curve OBG rhob (i.e., curve e) represents the calculated vertical stress (i.e., overburden pressure) (i.e., directly calculated using rock mechanics parameters), the square OBG-m (i.e., point E) represents the vertical stress obtained by measurement and analysis (i.e., indirectly analyzed using other well logging data); the curve ShGElastic (i.e., curve a) represents the calculated minimum horizontal principal stress (i.e., directly calculated using rock mechanics parameters), the square ShGmin (i.e., point A) represents the minimum horizontal principal stress measured by the hydraulic fracturing method (i.e., indirectly analyzed using other well logging data); the curve SHG-ShG-OBG (i.e., curve b) represents the calculated maximum horizontal principal stress (i.e., directly calculated using rock mechanics parameters), the square SHmax (i.e., point B) represents the maximum horizontal principal stress obtained by measurement and analysis (i.e., indirectly analyzed using other well logging data); the curve PP dt e3 (i.e. curve d) represents the calculated formation pore pressure (i.e. directly calculated using rock mechanics parameters), and the square PP (i.e. point D) represents the measured and analyzed formation pore pressure (i.e. indirectly analyzed using other logging data). Curve SFG Mohr-Coulomb (i.e. curve c) represents the collapse pressure calculated by the Mohr-Coulomb plastic yield condition (i.e. directly calculated using rock mechanics parameters), i.e. the lower limit of the mud density window.

[0070] As can be seen from the figure, the value of the block OBG-m (i.e. the vertical stress obtained by indirect analysis using other logging data) is significantly smaller than the value of the curve OBG (i.e. the vertical stress obtained by direct calculation using rock mechanics parameters), with a relative error of about 10%. The value of the curve SHG at a vertical depth of about 2560 meters (i.e. the maximum horizontal principal stress obtained by direct calculation using rock mechanics parameters) coincides with the value of the block SHG-max (i.e. the maximum horizontal principal stress obtained by indirect analysis using other logging data), indicating that the result of this SHG curve is reasonable. The value of the curve ShG at a vertical depth of about 2560 meters (i.e. the minimum horizontal principal stress obtained by direct calculation using rock mechanics parameters) coincides with the value of the block ShGmin (i.e. the minimum horizontal principal stress obtained by indirect analysis using other logging data), indicating that the result of this ShG curve is reasonable. The value of curve PP at a vertical depth of about 2560 meters (that is, the formation pore pressure obtained by directly calculating the rock mechanics parameters) coincides with the value of block PP (that is, the formation pore pressure obtained by indirectly analyzing other logging data), indicating that the result of this PP curve is reasonable.

[0071] according to Figure 5Based on the single-well geomechanical results, it can be considered that the vertical stress amplitude in the formation near the Wei-202 vertical well is in the middle of the three principal stress components, and therefore belongs to the "strike-slip fault stress format".

[0072] Step S13, comprehensively analyzing the information of the World Stress Map (WSM), the single well measurement information of existing wells, and the microseismic monitoring information of horizontal well fracturing in the target block, to obtain the maximum horizontal principal stress direction angle in the target block.

[0073] Here, the specific implementation method of the comprehensive analysis of the information of the world stress map, the single well measurement information of the existing wells, and the microseismic monitoring information of the horizontal well fracturing in the target block refers to: first, using the world stress map to determine the maximum horizontal principal stress direction angle in the area to which the target block belongs, and clarifying the interval range to which the maximum horizontal principal stress direction angle in the target block belongs; then, based on the information of the single well measurement, determine the interval range to which the maximum horizontal principal stress direction angle in different structural parts in the target block belongs, and clarify the change law of the maximum horizontal principal stress direction angle in the target block with the terrain; finally, analyze the microseismic monitoring information, and verify and correct the value of the maximum horizontal principal stress direction angle in the target block summarized by the above two types of information in combination with the analysis results of the microseismic monitoring information, or supplement the value of the maximum horizontal principal stress direction angle in the target block in certain areas omitted by the above two types of information.

[0074] In this embodiment, the analysis of microseismic monitoring information may include: determining the position where a single-color strip distribution appears in the microseismic event points of the horizontal wells in the target block as a fracture network strip generated by the same fracturing stage, and determining the direction angle of the fracture network strip as the direction angle of the maximum horizontal principal stress at the position; determining the position where a color strip composed of multiple colors appears in the microseismic event points of the horizontal wells in the target block and the event point distribution exceeds the reservoir range as the position of a natural fracture; determining the situation where microseismic response points appear in the microseismic event points of the horizontal wells in the target block in a sheet-like or cluster-like distribution as the maximum horizontal principal stress directionality at the position is not obvious, and the minimum horizontal principal stress direction is close to the vertical principal stress direction.

[0075] The following is an example of the field application of the Weiyuan area shale gas three-dimensional block Wei 202.

[0076] The information in the World Stress Map WSM shows that the regional geostress format of the Sichuan Basin is mainly characterized by thrust faults and strike-slip fault stress patterns. The direction of the maximum horizontal principal stress in the region is mainly east-west, and other directions such as northeast-southwest and northwest-southeast also exist.

[0077] Figure 6The maximum principal stress distribution of the Wufeng Formation-Longmaxi Formation in the upper reservoir of the single well location of 13 wells in the Weiyuan area. This information is a combination of stress orientation analysis results such as microseismic monitoring and cross-dipole array acoustic logging analysis. Figure 6 The first dotted line A on the left refers to the altitude of -1400m, the second dotted line B refers to the altitude of -2400m, and the third dotted line C refers to the altitude of -3100m. Figure 6 As shown in the figure, the information measured by a single well shows that the maximum horizontal principal stress shows a certain regular trend of change in different structural parts of the block. The entire Weiyuan shale gas block can be divided into: the top gentle zone between the upper left boundary and the dotted line A, the middle steep zone between the dotted line A and the dotted line B, the lower right gentle zone between the dotted line B and the dotted line C, and the near-sag gentle zone between the dotted line C and the lower right boundary. The maximum horizontal principal stress direction angle of the top gentle zone is 130°, the maximum horizontal principal stress direction angle of the middle steep zone is 95°~105° (variable range 10°), the maximum horizontal principal stress direction angle of the lower right gentle zone is 85°~95° (variable range 10°), and the maximum horizontal principal stress direction angle of the near-sag gentle zone is 65°~95° (variable range 30°). From the above information, it can be seen that the maximum horizontal geostress in the Wufeng Formation-Longmaxi Formation reservoir in the Weiyuan block varies in a complex manner, not only changing with the horizontal position (from 130° to 65°~90°), but also changing by 30° with the depth in the reservoir.

[0078] Fig. 7A , Figure 7B , Figure 7C and Fig.7D It is the microseismic monitoring information of some existing horizontal wells in Weiyuan Block. Fig. 7A Microseismic information of Wei 202 well area, Figure 7B Microseismic information map of Weiwei 204 well area, Figure 7C The fracturing microseismic information of Weiwei 202H10-3 horizontal well, Fig.7D Microseismic monitoring information of Weiwei 204H1-5.

[0079] Since the location of the microseismic event point depends on two factors: the direction of the maximum principal stress and the distribution of natural fractures, Fig. 7A , Figure 7B , Figure 7C and Fig.7D The different colors in the figure represent the microseismic events generated at different times / fracture stages. When each color is distributed in a single color strip, it means that this is the fracture network strip generated by the same fracturing stage, and the orientation angle of this fracture network strip is the orientation angle of the maximum horizontal principal stress at this location. Fig. 7A , Figure 7B , Figure 7C and Fig.7DThe solid line in the figure is drawn according to this principle, and it represents the direction of the maximum horizontal principal stress. When the color strip representing the microseismic event is composed of multiple colors and the event point distribution exceeds the reservoir range, this time, the color strip represents the location of the natural fracture. Fig. 7A , Figure 7B , Figure 7C and Fig.7D Indicated by dotted line segments.

[0080] That is to say, Fig. 7A , Figure 7B , Figure 7C and Fig.7D In the figure, the solid line segment indicates the direction of the maximum horizontal principal stress in the fracture network strip generated by the same fracturing stage, and the dotted line segment indicates the location of the natural fracture. Fig. 7A The dotted line in the figure refers to the natural fracture location. Figure 7C and Fig.7D The distribution of microseismic events in Fig.7D It can be seen that the microseismic event point exceeds the target layer box and is a natural fracture-related event. The direction angle of natural fractures depends on the direction of geological tectonic movement, which is often inconsistent with the current formation principal stress direction angle, and generally has no clear analytical relationship.

[0081] In addition, Fig. 7A , Figure 7B , Figure 7C and Fig.7D In the figure, the microseismic response points are distributed in clusters, indicating that the directionality of the maximum horizontal principal stress is not obvious, and the directions of the two principal stresses (minimum horizontal principal stress and vertical principal stress) are close. As shown in the figure, the microseismic monitoring information of horizontal well fracturing in the target block shows that the direction of the maximum principal stress in the middle of the block is mainly along the east-west direction; the directions of the maximum principal stresses on both sides of the block deviate to the upper sides of their respective sides; on the left side of the Wei 202 block, the maximum direction angle can reach 110°.

[0082] Fig. 7A The microseismic event points in the dotted circle in the figure are distributed in a sheet-like manner, indicating that the two horizontal principal stresses here are close in magnitude and there is no obvious dominant principal stress direction. Figure 6 The maximum horizontal principal stress direction angle information of a single well in Figure 6 At locations where the principal stress direction angle varies greatly, microseismic events are distributed in sheets / clusters without obvious horizontal principal directions.

[0083] Step S14: introduce a three-dimensional geological model, establish a finite element model of the geostress field of the target block, and verify the simulation results of the geostress field of the target block based on the geological analysis results of the single well and the microseismic measurement results of the existing wells during the fracturing construction, and construct the qualified numerical solution of the geostress field into a fine geostress field of the block.

[0084] Specifically, the triaxial geostress principal components obtained from the single well geological analysis results in step S12 and the maximum horizontal principal stress direction angle obtained in the analysis in step S13 are first input as model setting parameters into the three-dimensional geological model of the target block obtained in step S11, and a finite element model of the geostress field of the target block can be established; then a numerical simulation of the geostress field of the target block is performed, and the numerical simulation results of the geostress field are compared and verified with the microseismic measurement results of the existing wells during the fracturing construction and the single well geological analysis results, and the model setting parameters are adjusted, and the verified finite element model of the geostress field is used as a numerical model that can truly simulate the geostress field of the target block, and the three-dimensional fine geostress field numerical solution of the target block obtained can be used as input data for subsequent fracturing and casing deformation simulation.

[0085] For example, the specific implementation of establishing the finite element model of the geostress field of the target block may include: the unit used in the geological model grid is a three-dimensional 8-node linear unit. Among them, the stratum where the reservoir is located is set as the C3D8RP-pore pressure coupling unit, and other strata are set as the C3D8R displacement unit. Among them, C3D8RP and C3D8R refer to the unit type in the software Abaqus, C represents the solid unit, 3D represents the three-dimensional, 8 is the number of nodes of this unit, R means that this unit is a reduced integration unit, and P refers to the three-line pore pressure. The model load is set as a gravity load. The boundary conditions of the four sides and the bottom of the model are set as normal displacement constraints, and the boundary conditions of the top are set as free boundaries. The initial conditions input the initial geostress parameters and the initial pore pressure parameters, wherein the initial geostress parameters include the triaxial geostress principal components (i.e., the maximum horizontal principal stress, the minimum horizontal principal stress and the vertical principal stress) and the maximum horizontal principal stress direction angle.

[0086] For each single well in the target block, the in-situ stress results obtained by indirect analysis using other logging data and the in-situ stress results obtained by direct calculation using rock mechanics parameters can be input as initial in-situ stress parameters, and numerical simulation of the in-situ stress field of the target block can be performed to obtain the corresponding numerical solution of the in-situ stress field. Then, the errors of the above two numerical solutions of the in-situ stress field and the actual measured values ​​of the in-situ stress field of the existing well fracturing construction are compared, and the numerical solution with the smaller error with the actual measured value of the in-situ stress field is constructed as the fine in-situ stress field of the block, and used as the input data for subsequent fracturing and casing deformation simulation.

[0087] For example, we can compare and analyze whether the maximum horizontal principal stress direction distribution of the reservoir obtained from the two simulations is consistent with the microseismic measurement results of existing wells during fracturing construction, whether the stress format of the reservoir is consistent with the geomechanical analysis results of a single well, and whether the distribution law of the reservoir's geostress field is consistent with the microseismic measurement results of existing wells during fracturing construction. The geostress analysis results with smaller errors in the two simulations are judged to be more suitable for setting as simulation parameters for the block geostress field that reproduces the actual fracturing construction process, and the numerical solution of the geostress field obtained is also more suitable as input data for subsequent fracturing and casing deformation simulation. Considering that the main purpose of the model numerical results is for the subsequent "casing deformation prediction caused by fracturing", the model parameter preparation mainly emphasizes that the minimum principal stress result of the numerical solution is close to the measured value, that is, the principle of "giving priority to ensuring that the minimum principal stress result of the numerical solution is closest to the measured value, and taking into account the trend of the maximum horizontal principal stress direction angle numerical solution and the measured value intermediate value is consistent" is used to ensure the rationality of the model.

[0088] It should be noted that the purpose of single-well geomechanical analysis is to analyze the extension direction of the crack. Since the crack always extends in the direction perpendicular to the minimum horizontal principal stress, the orientation of the crack extension can be predicted by determining the orientation of the geostress. The local geological structural details of different well sections vary to a certain extent, so the geostress analysis results suitable for simulating the vertical well are also different. By using the geostress results obtained by indirect analysis using other logging data and the geostress results obtained by direct calculation using rock mechanics parameters as initial geostress parameters, numerical simulations of the geostress field of the target block are performed respectively, and the simulation accuracy of the two sets of geostress data can be judged, so as to select the initial input parameters of the geostress field simulation that are most suitable for simulating the vertical well. In this way, for all vertical wells in the target block, the geostress analysis results with the most suitable simulation parameters for the block geostress field that are set to reproduce the actual fracturing construction process (i.e., the minimum error) can be repeatedly found, which can improve the overall simulation accuracy of the geostress field model, thereby establishing a fine geostress field, and ensuring that the simulated fracture extension direction is close to the real fracture state during subsequent fracturing and casing deformation simulation.

[0089] The following is an example of the field application of the Weiyuan area shale gas three-dimensional block Wei 202.

[0090] The single well geological analysis result in step S12 and the maximum horizontal principal stress direction angle in step S13 are input as initial conditions into the geostress field model of this step.

[0091] Table 1 is a list of model elastic parameters based on the above single well geological analysis results and experience. The elastic modulus varies with depth. The calculation model uses abaqus user subroutine to realize its TVD depth (TVD refers to vertical depth) dependence characteristics.

[0092] Table 1 List of model elastic parameters based on comprehensive single well analysis results and experience

[0093]

[0094] Calculating formation material parameters (i.e., rock mechanics parameters) such as Young's modulus and initial geostress-related parameters based on the logging data of a single well can reduce the uncertainty of model input parameters caused by insufficient measured parameters and ensure the accuracy of the initial input parameters of the fine geostress field model.

[0095] In addition, the collapse pressure (e.g. Figure 5 The curve c) in the figure can be compared and corrected with the simulation result of the geostress field model in this step, and it is not necessary to input the geostress field model.

[0096] like Figure 8 The figure shows the finite element model mesh of the geostress field of the Wei 202 block, which comes from the geological model mesh established in step S11. The unit used is a three-dimensional 8-node linear unit, a C3D8RP displacement-pore pressure coupling unit in the reservoir, and a C3D8R displacement unit outside the reservoir. The long side direction is taken as the x-axis direction. The load of the model is the gravity load. The boundary conditions are the normal displacement constraints of the four sides and the normal displacement constraints at the bottom; the top is the ground, a free boundary.

[0097] use Figure 8 The 3D finite element mesh model in the target block is used to set the initial conditions and establish the finite element model of the geostress field. The initial conditions include the initial geostress field and the initial pore pressure field. The pore pressure field only exists in the target layer Wufeng Formation-Longmaxi Formation. The pore pressure coefficient of Wei 202 Block is 1.4g / cc. The initial geostress field is set according to Figure 5 The given single well geostress components are used to set the geostress component parameters of each formation.

[0098] The distribution direction of the maximum horizontal principal compressive stress in the Wufeng Formation-Longmaxi Formation in the Wei 202 block obtained by numerical calculation is as follows: Fig. 9 As shown. Fig. 9 It can be seen that the maximum horizontal principal stress in the numerical results is about 130° in the gentle zone in the upper left part of the Wei 202 block; the maximum horizontal principal stress direction in the lower right part of the block gradually transitions to 90° close to the east-west direction. This result is consistent with Figure 6 Direction angle measurement analysis results are given.

[0099] Fig. 10A and Fig. 10B The directions of the minimum horizontal principal compressive stress and the intermediate principal stress in the Wufeng Formation-Longmaxi Formation of the Wei 202 block are given respectively. Fig. 10Cis the three-dimensional vector direction distribution diagram of the intermediate principal stress. Fig. 10A , Fig. 10B and Fig. 10C It can be seen that in the lower right / southeast position of the Wei 202 block, the intermediate principal stress is nearly vertical. This indicates that the vertical stress at these locations is the intermediate principal stress component, and the stress format belongs to the "strike-slip fault stress format". This result is consistent with Figure 5 The single well geomechanical results.

[0100] Fig.11 This is a distribution cloud diagram of the three-dimensional numerical solution of the geostress field of the reservoir unit of the Wei 202 vertical well (TVD=2550m). The side length of the unit is 275 meters. The symbol convention in the figure follows the symbol convention of solid mechanics, that is, tensile stress is positive and compressive stress is negative. It can be seen from the figure that the amplitude of stress gradually increases from northwest to southeast. At the same time, Table 2 gives a comparison of the numerical solution and measured values ​​of the geostress of the Wei 202 vertical well. It can be seen from Table 2 that the amplitudes of the two horizontal principal stresses in the numerical results are very close to the measured values, and the error between the vertical stress and the measured value is relatively large, which is 6.37%.

[0101] Table 2 Comparison of numerical solution and measured values ​​of in-situ stress in Wei-202 vertical well

[0102]

[0103] Analyzing the above simulation results, it is found that the numerical solution of the magnitude and direction of the principal stress has a certain error with the measured value. One of the reasons is that the simplified model used in the calculation may deviate from the actual situation in terms of local structural details. In addition, the principal direction angle given by the measured value is a range, while the principal stress value is an average value. This shows that the measured value itself is also an average value with an error range.

[0104] Taking into account that the main purpose of the model numerical results is to predict the casing deformation caused by fracturing later, the model parameters were prepared with the main emphasis on the proximity of the minimum principal stress results of the numerical solution to the measured values. That is, the principle of “giving priority to ensuring that the minimum principal stress results of the numerical solution are closest to the measured values, while taking into account the consistency of the trend of the intermediate value between the numerical solution and the measured values ​​of the maximum horizontal principal stress direction angle” was used to ensure the rationality of the model.

[0105] Therefore, after comprehensive analysis and consideration, it is believed that the above numerical results of the geostress field can be constructed as a refined geostress field of the Wei 202 block, and thus used as input data for subsequent fracturing and casing deformation simulation.

[0106] Step S2: Based on the fine geostress field of the block, a finite element model of geology-fracturing engineering-cement sheath-casing integration is established, and a three-dimensional finite element deformation and stress analysis is performed on the casing string of the entire horizontal section of the horizontal well to obtain the initial stress distribution of the casing string before fracturing.

[0107] Specifically: On the basis of the finite element model of the geostress field of the block in step S1, the geometric models of the well, cement sheath and casing are established, and the model data of the fracturing construction is set to obtain a finite element model of geology-fracturing engineering-cement sheath-casing integration, and the numerical simulation results of the fine geostress field of the block are used as input data for fracturing and casing deformation simulation.

[0108] For example, the establishment of a finite element model of geology-fracturing engineering-cement sheath-casing integration may include the following: first establish a geometric model of the well, then set the model data, the model data includes reservoir thickness distribution, horizontal section logging data, ground stress field distribution, designed fracturing construction parameters, perforation parameters, formation pressure coefficient, ground stress parameters, rock mechanics parameters, and finally consider a variety of materials (including formation materials, cement sheath materials and casing materials), a variety of geometric shapes (including formation geometry, cement sheath geometry and casing geometry), two physical fields of structural deformation and physical seepage, fluid pressure load, ground stress load, gravity load, elastic mechanics model, and plastic mechanics model to establish a three-dimensional finite element model of the well. For the mathematical model of geology-fracturing engineering-cement sheath-casing integration for predicting casing deformation, its basic theoretical model is the plastic loading yield criterion of metals, including the Tresca yield criterion of formula (5) and the von Mises yield criterion of formula (6). Both are yield criteria based on shear strength. In other words, the plastic deformation of metal materials is shear plastic deformation.

[0109] τ max =K Formula (5)

[0110] (σ1-σ2) 2 +(σ2-σ3) 2 +(σ3-σ1) 2 =2σ s 2 =6K 2 Formula (6)

[0111] Among them, σ1, σ2, σ3 are three principal stresses, MPa, σ s is the yield stress, MPa, and K is the shear yield strength of the material, MPa.

[0112] The tensile plasticity of the casing appears to be tensile plastic deformation at a macroscopic level, but the microscopic mechanism is shear plastic slip of metal crystals. Based on this, considering the environment in which the casing is located, it is believed that during fracturing construction, along the horizontal axis, if there are defects (for example, defects with gamma anomalies and defects with poor cementing quality) at the places where the shear load is the largest around the casing, then there is a high risk of casing deformation at these defects. These places should be avoided from falling into the area with the largest shear load.

[0113] The final "geology-fracturing engineering-cement sheath-casing integration" model includes:

[0114] 1) Various materials and geometric shapes;

[0115] 2) Two physical fields: structural deformation and seepage;

[0116] 3) Fluid pressure load, ground stress load, gravity load;

[0117] 4) Elasticity constitutive model and plasticity constitutive model.

[0118] The mechanical behavior of this complex model can be summarized by the following formula:

[0119] K(u)·u=F

[0120] The variables here are defined as:

[0121] K is the system stiffness matrix, which represents the material properties of the model including elastic constitutive and plastic constitutive properties, as well as geometric characteristics; u is the motion vector, including the displacement and pore pressure of each point in the model; F is the load vector, which represents the various loads involved in the model.

[0122] Step S3, performing three-dimensional finite element deformation and stress analysis on the casing string after the reservoir is fractured, calculating the change of the ground stress field caused by the fracturing, and finding the position distribution of the shear load applied to the casing.

[0123] Specifically, model parameters can be set for the target layer section of the casing string in the finite element model of the geology-fracturing engineering-cement sheath-casing integration according to the designed fracturing construction parameters, and numerical simulation of reservoir fracturing can be performed to calculate the changes in the ground stress field caused by the fracturing construction of the target layer section, and find the position distribution of the shear load applied to the casing.

[0124] Step S4, performing an integrated casing deformation analysis combining geology, cementing and casing of the horizontal well, the analysis includes gamma curve distribution analysis of the horizontal section of the well trajectory, cementing quality and acoustic amplitude curve distribution analysis of the horizontal section of the well trajectory, fracturing construction pressure curve analysis of the horizontal section of the well trajectory, microseismic monitoring result analysis of the horizontal well, and simulated calculation of the change analysis of the external shear force of the wellbore in the horizontal section of the well trajectory.

[0125] Step S5: predict the location of casing deformation induced by fracturing based on the casing deformation analysis results, wherein the location of casing deformation includes the location of the local abnormal protrusion of the gamma curve, the location of the cementing homogeneity anomaly, the maximum shear load point caused by the fracturing section where the construction pressure peak is located, and the outer edge of the formation crushing zone caused by fracturing.

[0126] Based on a large amount of research, the present invention confirms three major influencing factors of fracturing-induced casing deformation, namely geological factors, cementing factors and construction engineering factors.

[0127] Among them, geological factors refer to the asymmetric formation stiffness and obvious local changes. The casing in this area is subject to greater external shear force than other locations, so the probability of casing deformation is high. Before fracturing construction, the gamma logging curve can be analyzed to identify the locations where the formation stiffness is asymmetric and the local changes are obvious in the horizontal section of the well trajectory. For example, when a local abnormal bulge appears in the gamma logging curve of the horizontal section of the well trajectory, it can be considered that the information of the feature identification is asymmetric formation stiffness and abnormal local changes. The basis for determining the local abnormal bulge of the gamma curve can be that the local gamma value is greater than 200GAPI.

[0128] In addition, at the outer edge of the formation fracture zone produced by fracturing, there are also situations where the formation stiffness is asymmetric and the local stiffness changes significantly, and the casing located at this position is more likely to be deformed. However, this position can only be discovered after the construction (during the fracturing construction process or after the fracturing construction is completed) by obtaining the corresponding logging data. Therefore, in order to predict the outer edge of the formation fracture zone produced by fracturing in advance, and identify the position where the formation in the horizontal section of the well trajectory is prone to asymmetric stiffness and significant changes in local stiffness after fracturing construction, the present invention can analyze the corresponding casing deformation here by numerical simulation of reservoir fracturing during the fracturing construction design stage. The shear localization zone caused by fracturing can be obtained in the numerical simulation results of reservoir fracturing, and the shear localization zone can be regarded as the formation fracture zone caused by fracturing. Here, the shear localization zone refers to the area where the shear strain is concentrated under the joint action of the pore pressure injected into the formation and the ground stress field. The formation load on the casing located in this area is significantly higher than the formation load at other locations, so the probability of deformation of the casing located in this area is also higher than that at other locations. In order to verify the accuracy and precision of the shear localization zone obtained by simulation, the location of the outer edge of the formation fracture zone caused by fracturing can be determined by combining the analysis of the microseismic monitoring results of the horizontal well.

[0129] For example, before fracturing, the possible natural fracture areas can be determined through geological ant body data, well leakage data, etc., and the possible formation fracture areas can be predicted through the fracture areas.

[0130] Cementing factors refer to abnormal cementing homogeneity, that is, large local variations in cementing quality and local points of poor quality. The cementing cement in this area is uncemented or partially cemented and has poor shear resistance, so the probability of casing deformation is high. Before fracturing construction, the location of poor cementing quality in the horizontal section of the well trajectory can be identified by analyzing the cementing quality and the acoustic amplitude curve. For example, when the cementing quality and acoustic amplitude curve of the horizontal section of the well trajectory show obvious local changes in the cementing acoustic amplitude, the information of the feature identification can be considered to be abnormal cementing homogeneity. The basis for determining the abnormal cementing homogeneity can be that the local acoustic amplitude value is higher than the interface with poor cement bonding, and the local evaluation result of cementing quality is poor.

[0131] The construction engineering factor refers to the excessive pressure of the fracturing construction, which exceeds the permitted range. The local external shear force borne by the casing in this area is significantly higher than that in other locations, so the probability of casing deformation is high. During the fracturing construction process, the location where the construction pressure is too high in the horizontal section of the well trajectory can be identified by analyzing the fracturing construction pressure curve. For example, when there is an obvious local peak in the construction pressure curve, it may be due to a surge in pressure caused by sand plugging. It can be considered that the information of the feature identifier is that the pressure of the fracturing construction exceeds the permitted range. Here, the peak value of the construction pressure curve refers to a surge or drop in pressure, which causes obvious fluctuations in the pressure curve. The basis for determining the maximum shear load point caused by the fracturing section where the peak value of the construction pressure curve is located is that the pressure surge or drop is greater than 10MPa / min, and the pressure change curve is not a straight line.

[0132] That is to say, before fracturing construction, the location of casing deformation induced by fracturing can be predicted by the following methods:

[0133] (1) Analyze the gamma logging curve of the horizontal section of the well trajectory of the target well, find out the location of the casing string in the horizontal section of the well trajectory where the local gamma value of the gamma logging curve is greater than 200 GAPI, and predict it as the location of the casing deformation induced by fracturing.

[0134] (2) Analyze the cementing quality and acoustic amplitude curve of the horizontal section of the target well trajectory, find out the location of the casing string in the horizontal section of the well trajectory where the local acoustic amplitude value is higher than the interface with poor cement bonding in the cementing quality and acoustic amplitude curve and the local evaluation result of cementing quality is poor, and predict it as the location of casing deformation induced by fracturing.

[0135] (3) The parameters in the fracturing construction design phase are used to perform numerical simulation of reservoir fracturing on the target well, calculate the changes in the ground stress field caused by fracturing, predict the shear localization zone caused by fracturing, and predict the position of the casing string in the horizontal section of the well trajectory corresponding to the shear localization zone as the position of the casing deformation induced by fracturing.

[0136] During and after the fracturing construction, the maximum shear loading points (MSLP) caused by the fracturing section where the construction pressure peak is located can be found by analyzing the fracturing construction pressure curve of the horizontal section of the target well trajectory, and this MSLP point can be predicted as the location of the fracturing-induced casing deformation.

[0137] For the target well, the above four methods can be used to analyze and predict the possible locations of casing deformation before and during fracturing, and the predicted locations of casing deformation can be calibrated on the casing to obtain a prediction map of the locations of casing deformation induced by fracturing.

[0138] For example, the field application of the 204H12-5 well section in the three-dimensional shale gas block in Weiyuan area is taken as an example.

[0139] Fig.12 The following are the curves and gamma logging curves of casing damage (i.e. casing deformation) in well 204H12-5. Fig.12 Curve a is the maximum inner diameter, curve b is the average inner diameter, and curve c is the minimum inner diameter. Fig.13 This is the acoustic amplitude and evaluation diagram of cementing quality of well 204H12-5. Fig.13 Curve A is the casing coupling value, curve B is the wellbore value, and curve C is the natural gamma value.

[0140] Before fracturing, the gamma log curve of target well 204H12-5 was analyzed (e.g. Fig.12 It was found that the gamma values ​​at the depths of 3100m and 3200m suddenly increased from 70API to 190API, indicating that these two points are abnormally protruding locations of the gamma curve, which may be the locations of casing deformation. At the same time, the cementing quality and acoustic amplitude curve of the target well 204H12-5 were analyzed (as shown in Figure 2). Fig.13 It was found that the acoustic amplitude showed a significant local change at the depth of 3200m, that is, the acoustic amplitude showed a large fluctuation, which showed that the cementing quality of the external interface at this location was poorly homogeneous, and it might be the location of casing deformation. Therefore, based on the comprehensive analysis of logging data, natural fracture distribution data, and fracturing operation parameters, it was found that the formation stiffness at the location of 3200m downhole depth was asymmetric and the cementing quality was poor, which was prone to casing deformation, and it was predicted to be the location where casing deformation was induced by fracturing.

[0141] During the actual production application of the target well 204H12-5, it was found that the casing string at the predicted position was deformed. Fig.12As shown in the figure, at a depth of about 3200m, the minimum inner diameter (curve c), average inner diameter (curve b) and maximum inner diameter (curve a) of the casing decrease sharply, that is, 3200m downhole is the location where the casing deformation occurs. Fig.13 It can also be seen that after the depth of 3100m underground, the wellbore curve (i.e., curve B) changes from being flat to fluctuating up and down, which indicates that casing deformation occurs after 3100m underground.

[0142] This shows that the locations where the gamma curve local abnormal protrusions and cementing homogeneity abnormalities appear in the logging data can be predicted as the locations where fracturing induced casing deformation.

[0143] For another example, take the field application of the Yang 105H3-2 well section in the Taiyang tectonic area as an example.

[0144] Fig.14 This is the fracturing construction curve of the 7th section (2935-2855m underground) of Jingyang 105H3-2. Fig.14 Curve a in the figure is the well pressure of Yang 105H3-2, curve b is the construction displacement, and curve c is the sand concentration.

[0145] During the fracturing operation of the 7th section (2935-2855m below the surface) of the target well Yang 105H3-2, the fracturing operation curve (such as Fig.14 As shown in the figure, it can be found that during the entire construction period, there are multiple abnormal peaks in the construction pressure above the dotted line, which shows that the construction pressure of the 7th section is too high and exceeds the allowable range during the construction process, which may be the location of casing deformation. At the same time, the simulation calculation of the reservoir fracturing with water in the 7th section of the fracturing construction parameters is used. The simulation results show that the 7th section is located in the shear localization zone, which may be the location of casing deformation. Therefore, the comprehensive analysis of logging data, natural fracture distribution data and fracturing construction parameters shows that the location of 2935-2855m downhole depth is the formation fragmentation zone caused by fracturing, and the construction pressure is too high, exceeding the allowable range, and casing deformation is prone to occur. It is predicted to be the location of casing deformation induced by fracturing.

[0146] During actual production application of the target well 204H12-5, it was found that the target well encountered resistance at a well depth of 2761m when pumping the bridge plug in the 8th section, indicating that the casing in the 7th section was deformed.

[0147] This shows that the location where the abnormal peak value appears in the construction pressure curve and the location where the shear localization zone appears in the numerical simulation of reservoir fracturing can be predicted as the location where fracturing-induced casing deformation occurs.

[0148] For another example, take the field application of the 202H14-3 well section in the three-dimensional shale gas block in Weiyuan area as an example.

[0149] Before fracturing construction, the well ant body map of well 202H14-3 can be analyzed to determine the possible natural fracture areas, and the possible formation fracture areas can be predicted through the fracture areas. Fig.15 This is the well ant body diagram of well 202H14-3. Fig.15 As shown in the figure, it can be seen that at the 21st to 23rd section, that is, the position of 3068-3340m downhole (the position of the dotted circle), there is a natural fracture zone in the wellbore, and the casing at this position is in the formation fracture zone. At the same time, using the simulation calculation of the fracturing operation parameters of well 202H14-3, the simulation results show that the 21st to 23rd section is located in the shear localization zone, which verifies the position of 3068-3340m downhole (that is, Fig.15 The dotted circle (the position of the dotted circle) is the natural fracture zone and the broken zone, which is prone to casing deformation.

[0150] During actual production application of the target well 202H14-3, it was found that after the 10th section (i.e. 4017-4084m underground) was constructed, the pumping of the bridge plug encountered resistance at 3290.81m, indicating that the casing at the position of 3068-3340m underground was deformed.

[0151] This shows that the location of the shear localization zone in the numerical simulation of reservoir fracturing can be predicted as the location of the casing deformation induced by fracturing.

[0152] In summary, the beneficial effects and advantages of the present invention include at least one of the following:

[0153] (1) The present invention inputs the logging data and rock mechanics parameters of a single well into the geostress field model for simulation calculation, and repeatedly compares and verifies the simulation results with the microseismic data during the actual fracturing, thereby obtaining a fine geostress field that can more realistically reproduce the geostress field distribution and fracture direction of the target block.

[0154] (2) The present invention uses the block's fine geostress field as input data for subsequent fracturing and casing deformation simulation, eliminating the uncertainty of model input parameters caused by large errors in logging data or insufficient measured parameters in the prior art, ensuring the accuracy of the input geostress field and improving the accuracy of predicting the casing deformation position using the integrated finite element model of geology-fracturing engineering-cement sheath-casing.

[0155] (3) The present invention comprehensively analyzes various factors that affect the deformation of the fracturing casing, organically links various factors of casing deformation, conducts a comprehensive integrated analysis, and predicts the location of casing deformation induced by fracturing in high ground stress areas in a targeted manner, which is conducive to the subsequent proposal of practical technical measures and the development of casing deformation prediction and prevention technical solutions.

[0156] (4) The prediction method of the present invention is based on well logging data and analysis, and has good operability.

[0157] (5) The prediction method of the present invention is used to analyze the location of casing deformation, and the prediction results are consistent with more than 85% of fracturing casing deformation cases, with high accuracy.

[0158] Although the present invention has been described above in conjunction with the exemplary embodiments and the accompanying drawings, it should be apparent to those skilled in the art that various modifications may be made to the above-described embodiments without departing from the spirit and scope of the claims.

Claims

1. A method for predicting the location of casing deformation induced by fracturing based on multi-dimensional information, characterized in that: The following steps are involved: Based on the well logging data of the target block, the geological analysis results of the single well and the maximum horizontal principal stress direction angle are obtained to establish the fine geostress field of the block; Based on the detailed geostress field of the block, a finite element model integrating geology, fracturing engineering, cement sheath and casing was established. The three-dimensional finite element deformation and stress analysis of the casing string in the entire horizontal section of the horizontal well was performed to obtain the initial stress distribution of the casing string before fracturing. Conduct three-dimensional finite element deformation and stress analysis on the casing string after fracturing the reservoir, calculate the changes in the ground stress field caused by fracturing, and find out the location distribution of the shear load applied to the casing; Conducting an integrated casing deformation analysis combining geology, cementing and casing for horizontal wells, including gamma curve distribution analysis of horizontal well trajectory sections, cementing quality and acoustic amplitude curve distribution analysis of horizontal well trajectory sections, fracturing pressure curve analysis of horizontal well trajectory sections, microseismic monitoring results analysis of horizontal wells, and simulated calculation of wellbore external shear force variation analysis of horizontal well trajectory sections; According to the analysis results of casing deformation, the location of casing deformation induced by fracturing is predicted, and the location of casing deformation includes the location of the local abnormal bulge of the gamma curve, the location of cementing homogeneity abnormality, the maximum shear load point caused by the fracturing section where the construction pressure peak value is located, and the outer edge of the formation crushing zone caused by fracturing; The establishment of a fine geostress field of the block includes the following steps: according to the technical method of "well-seismic combination", based on seismic wave data, combined with single well layer information, a three-dimensional geological model of the target block is established; according to the logging data of a single well in the target block, rock mechanical parameters are calculated, and single well geomechanical analysis is performed on other logging data and rock mechanical parameters to obtain single well geological analysis results; comprehensive analysis of information on the world stress map, single well measurement information of existing wells, and microseismic monitoring information of horizontal well fracturing in the target block is performed to obtain the maximum horizontal principal stress direction angle in the target block; a three-dimensional geological model is introduced to establish a finite element model of the geostress field of the target block, and based on the single well geological analysis results and the microseismic measurement results of the existing wells during the fracturing construction, the simulation results of the geostress field of the target block are verified, and the verified qualified numerical solution of the geostress field is constructed as a fine geostress field of the block; The method verifies the simulation result of the geostress field of the target block based on the geological analysis result of the single well and the actual microseismic measurement result of the existing well during the fracturing construction, and constructs the verified numerical solution of the geostress field as the fine geostress field of the block, including: for each single well in the target block, respectively using the geostress result obtained by indirect analysis of other well logging data and the geostress result obtained by direct calculation using rock mechanics parameters as initial geostress parameters, performing numerical simulation of the geostress field of the target block, and obtaining the corresponding numerical solution of the geostress field; comparing the errors of the above two numerical solutions of the geostress field with the actual measured values ​​of the geostress field of the existing well during the fracturing construction, and taking the numerical solution with the smaller error with the actual measured value of the geostress field as the fine geostress field of the block.

2. The method for predicting the position of casing deformation induced by fracturing based on multi-dimensional information according to claim 1, characterized in that: The method of establishing a three-dimensional geological model of the target block based on the seismic wave data and combining the single well layer information includes: establishing the grid geometry of the geological model according to the three-dimensional seismic wave data, dividing the strata and defining the grid unit size of each stratum, wherein the grid unit of the stratum where the reservoir is located is smaller than the grid unit of other strata.

3. The method for predicting the position of casing deformation induced by fracturing based on multi-dimensional information according to claim 2, characterized in that: The ratio of the grid unit thickness of the formation where the reservoir is located to the grid unit thickness of the other formations is 1:18-1:

30.

4. The method for predicting the position of casing deformation induced by fracturing based on multi-dimensional information according to claim 1, characterized in that: The other logging data include gamma rays, compression acoustic wave duration and density of the formation, and the rock mechanics parameters include Young's modulus, Poisson's ratio, cohesion and internal friction angle.

5. The method for predicting the position of casing deformation induced by fracturing based on multi-dimensional information according to claim 1, characterized in that: The single well geological analysis results include in-situ stress results obtained by indirect analysis using other logging data and in-situ stress results obtained by direct calculation using rock mechanics parameters.

6. The method for predicting the position of casing deformation induced by fracturing based on multi-dimensional information according to claim 1, characterized in that: The comprehensive analysis of the information of the world stress map, the single well measurement information of the existing wells, and the microseismic monitoring information of the horizontal well fracturing in the target block to obtain the maximum horizontal principal stress direction angle in the target block includes: Use the world stress map to determine the maximum horizontal principal stress direction angle in the target block area, and clarify the range of the maximum horizontal principal stress direction angle in the target block; Based on the information measured by a single well, determine the range of the maximum horizontal principal stress direction angle in different structural parts of the target block, and clarify the change pattern of the maximum horizontal principal stress direction angle in the target block with the terrain; Analyze the microseismic monitoring information, and verify and correct the value of the maximum horizontal principal stress direction angle in the target block summarized by the world stress map and single well measurement information in combination with the analysis results of the microseismic monitoring information, and / or supplement and correct the value of the maximum horizontal principal stress direction angle in the target block in the area omitted by the world stress map and single well measurement information.

7. The method for predicting the position of casing deformation induced by fracturing based on multi-dimensional information according to claim 6, characterized in that: The analysis of microseismic monitoring information includes: The locations where the microseismic event points of the horizontal wells in the target block appear in a single color strip distribution are determined as the fracture network strips generated by the same fracturing stage, and the direction angle of the fracture network strips is determined as the direction angle of the maximum horizontal principal stress at the location; The locations where color strips composed of multiple colors appear in the microseismic event points of the horizontal wells in the target block and the event points are distributed beyond the reservoir range are determined as the locations of natural fractures; The situation where the microseismic response points in the microseismic event points of the horizontal wells in the target block are distributed in sheets or clusters is judged as the direction of the maximum horizontal principal stress at this location is not obvious, and the direction of the minimum horizontal principal stress is close to the direction of the vertical principal stress.

8. The method for predicting the position of casing deformation induced by fracturing based on multi-dimensional information according to claim 1, characterized in that: The method of establishing a finite element model of the geostress field of the target block includes: setting the unit used in the geological model grid to a three-dimensional 8-node linear unit, setting the load of the finite element model of the geostress field to a gravity load, setting the boundary conditions of the four sides and the bottom of the finite element model of the geostress field to normal displacement constraints, setting the boundary conditions of the top to a free boundary, and setting the initial geostress parameters and the initial pore pressure parameters to initial conditions.

9. The method for predicting the position of casing deformation induced by fracturing based on multi-dimensional information according to claim 8, characterized in that: The initial geostress parameters include the triaxial geostress principal components and the maximum horizontal principal stress direction angle obtained by single well geomechanical analysis.

10. The method for predicting the position of casing deformation induced by fracturing based on multi-dimensional information according to claim 1, characterized in that: The basis for determining whether the gamma curve has a local abnormal protrusion is that the local gamma value is greater than 200 GAPI.

11. The method for predicting the position of casing deformation induced by fracturing based on multi-dimensional information according to claim 1, characterized in that: The determination basis of abnormal cementing homogeneity is that the local acoustic amplitude is higher than the interface with poor cement bonding, and the local evaluation result of cementing quality is poor.

12. The method for predicting the position of casing deformation induced by fracturing based on multi-dimensional information according to claim 1, characterized in that: The basis for judging the maximum shear load point caused by the fracturing section where the construction pressure peak value is located is that the amplitude of the pressure curve surge or drop is greater than 10 MPa / min, and the pressure curve is not a straight line.

13. The method for predicting the position of casing deformation induced by fracturing based on multi-dimensional information according to claim 1, characterized in that: The location of the formation fracture zone caused by the fracturing is determined by geological data before the fracturing and / or numerical simulation of the reservoir fracturing.

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