CN115324558A - Method for predicting fracture-induced casing deformation position based on multi-dimensional information - Google Patents

Abstract

The invention provides a method for predicting the position of casing deformation induced by fracturing based on multi-dimensional information, which includes the following steps: establishing a fine in-situ stress field in a block; model, and calculate the initial stress distribution of the casing string before fracturing; calculate the in-situ stress field change after reservoir fracturing and the stress distribution of the casing string; carry out the combination of geology-cementing-casing casing for horizontal wells Pipe deformation analysis; the position of abnormal bulge of the gamma curve, the position of abnormal cementing homogeneity, the maximum shear load point caused by the fracturing section where the peak value of construction pressure is located, and the fracture area of the formation caused by fracturing are analyzed. The outer edge is predicted to be the location of casing deformation. The invention integrates various factors to predict the casing deformation position induced by fracturing, and has high prediction rate and strong operability.

Description

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

technical field

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

Background technique

For example, the shale gas geological structure in the Sichuan Basin and similar high-stress areas in my country is complex, and the maximum horizontal principal stress of the reservoir is close to or even higher than the pressure of the overlying rock. Due to the influence and superposition of multiple factors, casing deformation occurs. The probability is relatively high, and the fracturing process is the most intuitive manifestation.

In the prior art, although research on casing deformation has been carried out at home and abroad, most of them use a single factor, or emphasize geological factors, or emphasize design factors. The conclusions formed are relatively single and limited, and the accuracy of predicting the casing deformation position is not high. high.

For example, the patent application document published on December 7, 2016 titled a method and device for determining the deformation area of the fracturing casing, and the publication number is CN 106199712 A describes a method for determining the deformation area of the fracturing casing and the device, the method determines the shear wave velocity of the stratum in the preset research area, and the constraints between the shear wave velocity and the formation density and the compressional wave velocity through the established petrophysical model that is compatible with the seismic elements of the preset research area, and The pre-stack elastic parameter inversion of seismic data is carried out using this constraint condition, and the plane distribution of the maximum curvature attribute is determined. Finally, the deformation area of the fracturing casing can be determined according to the plane distribution. This method uses seismic data inversion to infer the deformation area of the fracturing casing, but the seismic data is easily interfered by geological factors, and the analysis results have certain errors, so it is impossible to judge and predict the accuracy of the casing deformation area.

The patent application document named CN 111980697 A published on November 24, 2020, entitled Calculation Method of Wellbore Casing Variables for Hydraulic Fracturing Horizontal Wells in Naturally Fractured Shale Formation, describes a hydraulic fracturing method for natural fractured shale formations. The calculation method of wellbore casing variables in horizontal wells. This method is based on the complex variable function method to establish the I-II composite fracture displacement field analytical model of superimposed fluid pressure to obtain the tangential relative displacement of the fracture, and then according to the tangential relative displacement of the fracture A method for determining wellbore casing variables. However, this patent application only provides a method for calculating the set of variables using the model, and does not provide specific technical measures for reducing the set of variables.

Internationally, the scale of shale gas exploitation in high geostress areas is not very large, and there are few related studies on casing deformation induced by fracturing in this area, which also leads to low accuracy in predicting casing deformation.

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

Contents of the invention

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 (for example, Sichuan Basin or similar areas) based on multiple dimensions.

In order to achieve the above object, the present invention provides a method for predicting the location of casing deformation induced by fracturing based on multi-dimensional information, including the following steps: based on the logging data of the target block, obtaining the single well geological analysis results and the maximum horizontal principal stress Based on the fine in-situ stress field of the block, a finite element model integrating geology-fracturing engineering-cement sheath-casing is established, and the casing string of the entire horizontal section of the horizontal well is analyzed in three dimensions. The finite element deformation and stress analysis is used to obtain the initial stress distribution of the casing string before fracturing; the three-dimensional finite element deformation and stress analysis is carried out on the casing string after fracturing through the reservoir, and the in-situ stress field change caused by fracturing is calculated. Find out the position distribution of the shear load applied to the casing; conduct an integrated casing deformation analysis combining geology-cementing-casing in horizontal wells, the analysis includes the analysis of the gamma curve distribution in the horizontal section of the well trajectory, the well trajectory Analysis of cementing quality and sound amplitude curve distribution in the horizontal section, analysis of fracturing construction pressure curve in the horizontal section of well trajectory, analysis of microseismic monitoring results in horizontal wells, and analysis of shear force changes outside the wellbore in the horizontal section of well trajectory through simulation calculation; Deformation analysis results predict the location of casing deformation induced by fracturing. The location of casing deformation includes the location of local abnormal bulges in the gamma curve, the location of abnormal cementing homogeneity, and the fracturing section where the peak value of the construction pressure is located. The resulting point of maximum shear load, and the outer edge of the fractured zone of the formation due to fracturing.

In an exemplary embodiment of the present invention, the establishment of the block's fine geostress field may include the following steps: according to the "well-seismic combination" technical method, on the basis of seismic wave data, combined with single well horizon information, Establish a 3D geological model of the target block; calculate rock mechanics parameters based on the logging data of a single well in the target block, perform single well geomechanics analysis on other logging data and rock mechanics parameters, and obtain single well geological analysis results; comprehensive analysis World stress map information, single well measurement information of existing wells, and microseismic monitoring information of horizontal well fracturing in the target block, to obtain the maximum horizontal principal stress direction angle in the target block; introduce a 3D geological model to establish the target area Based on the finite element model of the in-situ stress field of the block, and based on the geological analysis results of single wells and the micro-seismic measurement results of existing wells during fracturing construction, the simulation results of the in-situ stress field in the target block will be verified, and the qualified in-situ stress field values will be verified. The solution is constructed as a block fine geostress field.

In an exemplary embodiment of the present invention, the establishment of the three-dimensional geological model of the target block based on the seismic wave data and in combination with the horizon information of a single well may include: establishing the grid geometry of the geological model according to the three-dimensional seismic wave data Size, divide the strata and define the grid cell size of each stratum, where the grid cell of the stratum where the reservoir is located is smaller than the grid cells of other strata.

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˜1:30.

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

In an exemplary embodiment of the present invention, the single well geological analysis results may include in-situ stress results obtained through indirect analysis using other logging data and in-situ stress results obtained through direct calculation using rock mechanics parameters.

In an exemplary embodiment of the present invention, the comprehensive analysis of world stress map information, single well measurement information of existing wells, and microseismic monitoring information of horizontal well fracturing in the target block obtains the The maximum horizontal principal stress direction angle may include: using the world stress map to determine the maximum horizontal principal stress direction angle of the area where the target block belongs, and specifying the range of the maximum horizontal principal stress direction angle in the target block; according to the information measured by a single well , to determine the range of the maximum horizontal principal stress direction angle of different structural parts in the target block, and to clarify the variation law of the maximum horizontal principal stress direction angle with the terrain in the target block; analyze the microseismic monitoring information, and combine the microseismic monitoring information The analysis results verify and correct the value of the maximum horizontal principal stress direction angle in the target block summarized by using the world stress map and single well measurement information, and/or make supplementary corrections to the missing areas by using the world stress map and single well measurement information The value of the maximum horizontal principal stress direction angle in the target block.

In an exemplary embodiment of the present invention, the analysis of the microseismic monitoring information may include: determining the location of the microseismic event points of the horizontal well in the target block that is distributed in a single color stripe as the same fracturing section The generated fracture network strips, and judge the direction angle of the fracture network strips as the direction angle of the maximum horizontal principal stress at this position; the microseismic event points in the horizontal wells in the target block are composed of multiple colors, and The position of the color band whose distribution of event points exceeds the range of the reservoir is judged as the position of natural fractures; the microseismic response points in the microseismic event points of horizontal wells in the target block are judged to be distributed in flakes or clusters. The directionality of the maximum horizontal principal stress at the location is not obvious, and the direction of the minimum horizontal principal stress is close to the direction of the vertical principal stress.

In an exemplary embodiment of the present invention, the establishment of the finite element model of the in-situ stress field of the target block may include: setting the unit used in the geological model grid as a three-dimensional 8-node linear unit, and the finite element model of the in-situ stress field The load is set as gravity load, the boundary conditions of the four sides and the bottom of the ground stress field finite element model are set as normal displacement constraints, the boundary conditions of the top are set as free boundaries, and the initial ground stress parameters and initial pore pressure parameters are set as initial condition.

In an exemplary embodiment of the present invention, the initial in-situ stress parameters may include triaxial in-situ stress principal components and maximum horizontal principal stress direction angle obtained from single-well geomechanics analysis.

In an exemplary embodiment of the present invention, the verification of the simulation results of the in-situ stress field in the target block based on the geological analysis results of a single well and the micro-seismic measurement results of the existing wells during fracturing construction will verify the qualified geological The numerical solution of the stress field is constructed as a fine in-situ stress field in the block, which may include: 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. The stress result is used as the initial in-situ stress parameter, and the numerical simulation of the in-situ stress field in the target block is carried out to obtain the corresponding in-situ stress field numerical solution; compare the above two in-situ stress field numerical solutions with the actual measurement of the in-situ stress field in the fracturing construction of the existing well Value error, and the numerical solution with smaller error from the actual measured value of the in-situ stress field is taken as the fine in-situ stress field of the block.

In an exemplary embodiment of the present invention, the basis for judging that the gamma curve is locally abnormally convex may be that the local gamma value is greater than 200GAPI.

In an exemplary embodiment of the present invention, the basis for judging the cementing homogeneity abnormality may be that the local acoustic amplitude is higher than the interface with poor cement bonding, and the local evaluation result of the cementing quality is poor.

In an exemplary embodiment of the present invention, the basis for judging the maximum shear load point caused by the fracturing section where the construction pressure spike is located may be that the magnitude of the pressure curve surge or drop is greater than 10 MPa/min, and the pressure The curve is not a straight line.

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

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

(1) In the present invention, the well logging data and rock mechanical parameters of a single well are respectively input into the in-situ stress field model for simulation calculation, and the simulation results are repeatedly compared and verified with the microseismic data when the fracturing is actually implemented, thereby obtaining a relatively Realistically reproduce the in-situ stress field distribution of the target block and the fine in-situ stress field of fracture direction;

(2) The present invention uses the fine in-situ stress field of the block as the 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 , which ensures the accuracy of the input in-situ stress field and improves the accuracy of predicting the casing deformation position using the integrated finite element model of geology-fracturing engineering-cement sheath-casing;

(3) The present invention comprehensively analyzes the various factors affecting the deformation of the fracturing casing, organically links various factors of the casing deformation, conducts a comprehensive integrated analysis, and has a targeted effect on the fracturing induced casing in the high geostress area. Prediction of the pipe deformation position is conducive to the subsequent proposal of feasible technical measures, and the development of casing deformation prediction and prevention technical solutions;

(4) The prediction method of the present invention is based on logging data and analysis basis, and has good operability;

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

Description of drawings

Fig. 1 shows a calculation flowchart of a method for predicting casing deformation positions induced by fracturing based on multi-dimensional information in an exemplary embodiment of the present invention.

Fig. 2 shows a calculation flow chart for establishing a block fine geostress field in an exemplary embodiment of the present invention.

Fig. 3 shows a schematic structural diagram of a three-dimensional geological model of Block Wei 202 in an exemplary embodiment of the present invention.

Fig. 4A shows the well logging data map of Wei 202 vertical well in an exemplary embodiment of the present invention; Fig. 4B shows the rock mechanics parameter map of Wei 202 vertical well in an exemplary embodiment of the present invention.

Fig. 5 shows a graph of single well geological analysis results of vertical well Wei 202 in an exemplary embodiment of the present invention.

Fig. 6 shows the maximum horizontal principal stress direction angle distribution diagram of 13 single wells in the Weiyuan area in an exemplary embodiment of the present invention.

Fig. 7 A shows the microseismic information map of Wei 202 well area in an exemplary embodiment of the present invention; Fig. 7 B shows the microseismic information map of Wei 204 well area in an exemplary embodiment of the present invention; Fig. 7C Fig. 7D shows the microseismic monitoring information of Wei 204H1-5 in an exemplary embodiment of the present invention .

Fig. 8 shows a grid diagram of the finite element model of the in-situ stress field of block Wei 202 in an exemplary embodiment of the present invention.

Fig. 9 shows the distribution diagram of the maximum horizontal principal compressive stress direction in the formation of Wufeng Formation-Longmaxi Formation in block Wei 202 in an exemplary embodiment of the present invention.

Figure 10A shows the distribution 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; Figure 10B shows the Wufeng Formation-Longmaxi formation in the Wei 202 block Figure 10C shows the three-dimensional vector direction distribution of the intermediate principal stress in the Wufeng Formation-Longmaxi formation in block Wei 202.

Fig. 11 shows a three-dimensional numerical solution distribution cloud diagram of the in-situ stress field of the Wei 202 vertical well reservoir unit in an exemplary embodiment of the present invention.

Figure 12 shows casing damage curves and gamma log curves in an exemplary embodiment of the present invention.

Fig. 13 shows the sound amplitude and evaluation diagram of cementing quality in an exemplary embodiment of the present invention.

Figure 14 shows a graph of a fracturing application in an exemplary embodiment of the invention.

Figure 15 shows a diagram of a well ant body in an exemplary embodiment of the present invention.

Detailed ways

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

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.

In this embodiment, FIG. 1 is a calculation flowchart of a method for predicting casing deformation positions induced by fracturing based on multi-dimensional information. As shown in Figure 1, a method for predicting the location of casing deformation induced by fracturing based on multi-dimensional information may include the following steps:

Step S1, based on the logging data of the target block, the single well geological analysis results and the maximum horizontal principal stress direction angle are obtained, and the fine in-situ stress field of the block is established.

Here, as shown in Figure 2, the analysis of the logging data of the target block and the establishment of the fine geostress field of the block may include the following steps:

Step S11, according to the technical method of "well-seismic combination" (that is, the combination of well logging and seismic), on the basis of seismic wave data and combined with single well horizon information, a three-dimensional geological model of the target block is established.

Specifically, combined with the structural fluctuation characteristics of the target block, on the basis of 3D seismic wave data, the overall geometry and grid size of the target block can be constructed, and then combined with the single well horizon information of existing wells in the target block, the Delineate the layer information of the target block, determine the geometric shape and grid size of the formation where the reservoir is located and other formations other than the reservoir, and obtain the three-dimensional geological model of the target block.

Here, the specific implementation of establishing the three-dimensional geological model of the target block may include: establishing the grid geometric size 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 stratum where the reservoir is located The grid cells are smaller than those of other strata. 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˜1:30. For example, the grid unit thickness of other formations may be 20 times the grid unit thickness of the formation where the reservoir is located.

Taking the field application of Wei 202 block, a three-dimensional shale gas block in Weiyuan area, as an example to illustrate.

The shale gas three-dimensional block in the Weiyuan area has the same surface and underground structural pattern, simple structure, high in the northwest and low in the southeast, and the axis is nearly east-west. In the central and northern part of the three-dimensional block, there are mainly Wei Ⅰ high points, and the south is the southern wing of the Weiyuan structure, with few faults and small fault drop. It can be seen from the structure of the phyllophyll shale in the Shaximiao Formation of the Middle Jurassic that the structure in the three-dimensional block is simple and the faults are not developed. It is a sub-first-order high point, and the axis is nearly east-west; the southern part of the three-dimensional area is the southern wing of the Weiyuan structure. The structural pattern of the subterranean area is generally consistent with that of the surface, but the local structural details have some changes, the folds are relatively strengthened, and the faults are relatively developed. Due to the small fault drop, it has little influence on the distribution of the initial in-situ stress field. In addition, due to the small fault drop, it is more difficult to identify faults through seismic wave data, and some faults with small drop are difficult to identify.

According to the field data, the block Wei 202 is 19km long and 13.5km wide. Based on the 3D seismic wave data, the 3D geological model of Block Wei 202 was established, combined with the stratigraphic sequence in the area where the single well is located, the geological model is divided into 7 horizons, from top to bottom: the ground to the bottom of the Jialingjiang Formation , Jialingjiang Formation bottom to Feixianguan Formation bottom, Feixianguan Formation bottom to Upper Permian bottom, Upper Permian bottom to Lower Permian bottom, Lower Permian bottom to Wufeng Formation bottom boundary (including the Longmaxi Formation), the bottom boundary of the Wufeng Formation to the bottom boundary of the Cambrian System, and the bottom boundary of the Cambrian System to -5500 meters above sea level. Among them, the reservoir is located in the Wufeng Formation-Longmaxi Formation formation.

Considering the optimization of the amount of finite element calculation, compared with the grids of other strata, the formation of Wufeng Formation-Longmaxi Formation (that is, the formation where the reservoir is located) is divided into a denser grid. That is, the Wufeng Formation-Longmenxi Formation grid has 20 layers, and the minimum unit thickness is 1 meter, while other strata adopt larger unit sizes. The geological model of Block Wei 202 uses a total of 121,068 units. Due to the impact of formation denudation, no distinction is made between the Wufeng Formation and the Longmaxi Formation, and the two are regarded as one formation.

Figure 3 shows the schematic diagram of the three-dimensional geological model of block Wei 202 (depth unit, meter), which shows the geometric shape and grid of the reservoir, showing a structure of high in the northwest and low in the southeast. The grids in different depths 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, and the bottom of the Upper Ermian. From the bottom of the Stramian to the bottom of the Lower Permian, from the bottom of the Lower Permian to the bottom of the Wufeng Formation (including the Longmaxi Formation), from the bottom of the Wufeng Formation to the bottom of the Cambrian, from the bottom of the Cambrian to the altitude -5500 meters.

Step S12 , calculating rock mechanical parameters according to the logging data of a single well in the target block, performing single well geomechanical analysis based on other logging data and rock mechanical parameters, and obtaining single well geological analysis results.

The other well logs may include gamma rays, compression sonic durations and densities of the formation. The rock mechanics parameters include Young's modulus, Poisson's ratio, cohesion (cohesion) and internal friction angle. Rock mechanical parameters such as Young's modulus can be calculated based on acoustic logging data using empirical formulas and related calculation principles. For example, rock mechanical parameters such as Young's modulus can be calculated by using the following related formulas (Equation (1) to Equation (4)).

E＝10 ³ ρ _b· [3(V _s /V _p ) ² -4]/Vs ² [(V _s /V _p ) ² -1] Formula (1)

v＝0.5[(V _s /V _p ) ² -2]/[(V _s /V _p ) ² -1] Formula (2)

C＝4.69433×10 ⁷ V _p ⁴ ρ _b [(1+v)/(1-v)](1-2v)(1+0.78V _sh ) Formula (3)

为内摩擦角，度。In the formula, E is Young's modulus, MPa; ρ _b is rock density, g/cm ³ ; Vs is longitudinal wave, us/m; Vp is transverse wave, us/m; v is Poisson's ratio, dimensionless; Cohesion, MPa; V _sh is mud content, %;

is the internal friction angle, in degrees.

The single well geological analysis results may include in-situ stress results obtained through indirect analysis using other well logging data and in-situ stress results obtained through direct calculation using rock mechanics parameters. The in-situ stress results obtained through indirect analysis using other logging data may include the maximum horizontal principal stress obtained through indirect analysis using other logging data, the minimum horizontal principal stress obtained through indirect analysis using other logging data, and the indirect horizontal principal stress obtained using other logging data. The vertical principal stress obtained through analysis, and the formation pore pressure obtained through indirect analysis using other logging data. The ground stress analysis results obtained by direct calculation of rock mechanics parameters include the maximum horizontal principal stress obtained by direct calculation of rock mechanics parameters, the minimum horizontal principal stress obtained by direct calculation of rock mechanics parameters, and the vertical vertical stress obtained by direct calculation of rock mechanics parameters. The principal stress and the formation pore pressure obtained by direct calculation using rock mechanics parameters.

Still taking the field application of Wei 202 block, a three-dimensional shale gas block in Weiyuan area, as an example.

Fig. 4A, Fig. 4B and Fig. 5 are the single well geological analysis results obtained after the single well geomechanical analysis of Wei 202 block by the method of step S12. Among them, Fig. 4A and Fig. 4B respectively show the logging data of a straight well in Block Wei 202 and the rock mechanical parameters calculated based on the acoustic logging data. The lower well trajectory of this well has a maximum inclination of 8.6 degrees. The left column of Fig. 4A is the gamma ray of the formation (unit: API), the left second column is the compression sound wave duration DC (unit: microsecond/foot), the left third column is the borehole diameter (unit: inch), and the right one The column is the density (unit: g/cc), and the second column on the right is the sound wave duration (unit: ms/ft). The left column of Fig. 4B is the value curve (unit: Mpsi) of the elastic modulus of the lower well section of Wei 202, the left two column is the value curve of Poisson's ratio, and the right column is the bond strength (unit: Mpsi) of the formation material : MPa), the second column on the right is the internal friction angle (unit: degree), where the bond strength and internal friction angle are the main parameters used to calculate the collapse pressure according to the Mohr-Coulomb condition.

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

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

It can be seen from the figure that the value of the square OBG-m (that is, the vertical stress obtained by indirect analysis using other logging data) is significantly smaller than the value of the curve OBG (that is, the vertical stress obtained by direct calculation using rock mechanics parameters), The relative error is about 10%. The value of the curve SHG at a vertical depth of about 2560 meters (that is, the maximum horizontal principal stress obtained by direct calculation using rock mechanics parameters) is the same as that of the square SHG-max (that is, the maximum horizontal principal stress obtained by indirect analysis using other logging data). Stress) values coincide, indicating that the SHG curve results are reasonable. The value of the curve ShG at a vertical depth of about 2560 meters (that is, the minimum horizontal principal stress obtained by direct calculation using rock mechanics parameters) and the value of the square ShGmin (that is, the minimum horizontal principal stress obtained by indirect analysis using other logging data) The coincidence of values shows that the result of the 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 direct calculation using rock mechanics parameters) is the same as the value of square PP (that is, the formation pore pressure obtained by indirect analysis using other logging data) The coincidence shows that the result of this PP curve is reasonable.

According to the single well geomechanics results in Fig. 5, 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, so it belongs to the “strike-slip fault stress format”.

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

Here, the specific implementation of the comprehensive analysis of the information of the world stress map, the single well measurement information of existing wells, and the fracturing microseismic monitoring information of horizontal wells in the target block refers to: firstly use the world stress map to judge the target area According to the maximum horizontal principal stress direction angle of the area to which the block belongs, specify the range of the maximum horizontal principal stress direction angle in the target block; then, according to the information measured by a single well, determine the maximum horizontal principal stress direction angle of different structural parts in the target block The range of the interval to which the maximum horizontal principal stress direction angle varies with the terrain in the target area is clarified; finally, the microseismic monitoring information is analyzed, and the analysis results of the microseismic monitoring information are combined to verify and correct the target area summarized by the above two information The value of the maximum horizontal principal stress orientation angle in the block, or the value of the maximum horizontal principal stress orientation angle in the target block that supplements some areas where the above two types of information are missing.

In this embodiment, the analysis of the microseismic monitoring information may include: judging the positions of the microseismic event points of the horizontal wells in the target block that are distributed in a single color strip as the fracture network strips produced by the same fracturing stage zone, and the direction angle of the fracture network strip is judged as the direction angle of the maximum horizontal principal stress at this position; the microseismic event points of the horizontal wells in the target block are composed of multiple colors, and the distribution of event points exceeds the reservoir The positions of the colored bands in the layer range are judged as the positions of natural fractures; the microseismic response points distributed in sheets or clusters in the microseismic event points of the horizontal wells in the target block are judged as the maximum horizontal main fractures at this position. The stress direction is not obvious, and the minimum horizontal principal stress direction is close to the vertical principal stress direction.

Still taking the field application of Wei 202 block, a three-dimensional shale gas block in Weiyuan area, as an example.

The information in the World Stress Map WSM shows that the regional in-situ stress pattern of the Sichuan Basin is characterized by stress patterns of thrust faults and strike-slip faults. 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.

Fig. 6 shows the distribution of the maximum principal stress direction of the reservoir Wufeng Formation-Longmaxi Formation in single well positions of 13 wells in the Weiyuan area. The information combines the stress azimuth analysis results of microseismic monitoring and cross-dipole array acoustic logging analysis. The first dotted line A on the left in Figure 6 refers to the position of -1400m above sea level, the second dotted line B refers to the position of -2400m above sea level, and the third dotted line C refers to the position of -3100m above sea level. As shown in Fig. 6, the information measured by a single well shows that the maximum horizontal principal stress presents a certain regular changing trend in different structural parts in 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, and the lower right zone between the dotted line B and the dotted line C The gentle oblique belt, and the near-depressed flat belt on the dotted line C and the lower right boundary. Among them, 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° (the variation range is 10°), and the maximum horizontal principal stress direction angle of the lower right gentle zone is The angle is 85°-95° (variation range 10°), and the maximum horizontal principal stress direction angle of the near-sag flat zone is 65°-95° (variation range 30°). From the above information, it can be seen that the maximum horizontal in-situ stress in the Wufeng Formation-Longmaxi Formation reservoirs in the Weiyuan block varies more complicatedly, not only changing with the horizontal position (from 130° to 65° to 90°), but also changing with the horizontal position. There is also a 30° variation with depth within the reservoir.

Figure 7A, Figure 7B, Figure 7C and Figure 7D show the microseismic monitoring information of some existing horizontal wells in the Weiyuan block. Among them, Figure 7A is the microseismic information of Wei 202 well area, Figure 7B is the microseismic information map of Wei 204 well area, Figure 7C is the fracturing microseismic information of Wei 202H10-3 horizontal well, and Figure 7D is the microseismic information of Wei 204H1-5 monitoring information.

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, different colors in Figure 7A, 7B, 7C, and 7D represent microseismic events generated at different times/fracturing stages. When each color is distributed in a single color strip, it means that this is a fracture network strip produced by the same fracturing section, and the direction angle of this fracture network strip is the direction angle of the maximum horizontal principal stress at this position. The solid line segment in Fig. 7A, Fig. 7B, Fig. 7C and Fig. 7D is drawn according to this principle, and it represents the direction of the maximum horizontal principal stress here. When the color band representing the microseismic event is composed of multiple colors, and the distribution of event points exceeds the reservoir range, at this time, the color band represents the position of the natural fracture, as shown in Fig. 7A, Fig. 7B, Fig. 7C and Fig. In 7D it is indicated by a dashed line segment.

That is to say, in Fig. 7A, Fig. 7B, Fig. 7C and Fig. 7D, the solid line segment indicates the direction of the maximum horizontal principal stress at the fracture network strip produced by the same fracturing stage, and the dotted line segment indicates the position of the natural fracture. The microseismic event distributions in Fig. 7C and Fig. 7D were referred to when marking the position of the natural fracture indicated by the dotted line segment in Fig. 7A. It can be seen from Figure 7D that the microseismic event point is beyond the box of the target layer, which belongs to the event related to natural fractures. The direction angle of natural fractures depends on the direction of geological structure movement, which is often inconsistent with the current principal stress direction angle of the formation, and generally there is no clear analytical relationship.

In addition, in Figure 7A, Figure 7B, Figure 7C and Figure 7D, the microseismic response points are distributed in clusters, indicating that the directionality of the maximum horizontal principal stress is not obvious, and the two principal stresses (minimum horizontal principal stress and vertical principal stress) The direction is approaching. 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 upper side deviates; on the left side of Wei 202 block, the maximum direction angle can reach 110°.

The microseismic event points in the dotted circles in Figure 7A are distributed in sheets, indicating that the two horizontal principal stresses here are close in magnitude, and there is no obvious dominant principal stress direction. This is consistent with the maximum horizontal principal stress direction angle information of a single well in Fig. 6. In the position where the principal stress direction angle in Fig. 6 varies widely, the microseismic events are distributed in sheets/clusters without obvious horizontal principal directions.

Step S14, introducing a three-dimensional geological model, establishing a finite element model of the in-situ stress field of the target block, and verifying the in-situ stress field of the target block based on the geological analysis results of a single well and the microseismic measurement results of existing wells during fracturing construction. Based on the simulation results, the verified numerical solution of the in-situ stress field is constructed as a block fine in-situ stress field.

Specifically, the principal components of the triaxial geostress obtained from the single well geological analysis results in step S12 and the maximum horizontal principal stress direction angle obtained from the analysis in step S13 are input as model setting parameters into the target block obtained in step S11. The three-dimensional geological model can establish the finite element model of the in-situ stress field of the target block; then carry out the numerical simulation of the in-situ stress field of the target block, and compare the numerical simulation results of the in-situ stress field with the microseismic measurement results of the existing wells during fracturing construction By comparing and verifying the geological analysis results of single wells, and adjusting the model setting parameters, the finite element model of the in-situ stress field after verification is used as a numerical model that can truly simulate the in-situ stress field of the target block. The numerical solution of the stress field can be used as input data for subsequent fracturing and casing deformation simulations.

For example, the specific implementation manner of establishing the finite element model of the in-situ stress 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 formation where the reservoir is located is set as the C3D8RP-pore pressure coupling unit, and the other formations are set as the C3D8R displacement unit. Among them, C3D8RP and C3D8R refer to the unit types in the software Abaqus, C means solid unit, 3D means three-dimensional, 8 is the number of nodes in this unit, R means that this unit is a reduced integration unit, P means a three-line pore pressure. The model loads are set to gravity loads. The boundary conditions on the four sides and the bottom of the model are set as normal displacement constraints, and the boundary conditions on the top are set as free boundaries. Initial conditions input the initial in-situ stress parameters and initial pore pressure parameters, where the initial in-situ stress parameters include the principal components of the triaxial in-situ stress (ie, the maximum horizontal principal stress, the minimum horizontal principal stress, and the vertical principal stress) and the maximum horizontal principal stress direction angle .

For each single well in the target block, the in-situ stress results obtained by indirect analysis of other logging data and the in-situ stress results obtained by direct calculation of rock mechanics parameters can be input as the initial in-situ stress parameters, and the in-situ stress results of the target block can be calculated. Field numerical simulation, to obtain the corresponding numerical solution of the stress field. Then compare the above two numerical solutions of the in-situ stress field with the errors of the actual measured value of the in-situ stress field in the fracturing operation of the existing well, and construct the numerical solution with a smaller error with the actual measured value of the in-situ stress field as the fine in-situ stress field of the block , and used as input data for subsequent fracturing and casing deformation simulations.

For example, it is possible to compare and analyze whether the distribution of the maximum horizontal principal stress direction of the reservoir obtained from the two simulations conforms to the microseismic measurement results of the existing well during the fracturing operation, whether the stress format of the reservoir conforms to the single well geomechanics analysis result, and whether the distribution of the in-situ stress field of the reservoir conforms to the micro-seismic measurement results of existing wells during fracturing construction, etc., and the in-situ stress analysis results with smaller errors in the two simulations are judged to be more suitable for setting to reproduce actual fracturing The simulation parameters of the in-situ stress field in the block during the construction process, and the numerical solution of the in-situ stress field obtained by it are also more suitable as input data for subsequent fracturing and casing deformation simulations. Considering that the main purpose of the numerical results of the model is for the follow-up “prediction of casing deformation caused by fracturing”, the preparation of the model parameters mainly emphasizes that the minimum principal stress result of the numerical solution is close to the measured value, that is, the minimum principal stress of the numerical solution is given priority. The principal stress results are closest to the measured values, and the numerical solution of the maximum horizontal principal stress direction angle is consistent with the trend of the middle value of the measured values” to ensure the rationality of the model.

It should be noted that the purpose of single-well geomechanics analysis is to analyze the extension direction of fractures. Since fractures always extend along the direction perpendicular to the minimum horizontal principal stress, determining the orientation of in-situ stress can predict the orientation of fracture extension. The details of the geological local structure in different well sections vary to some extent, so the in-situ stress analysis results suitable for simulating the vertical well are also different. By using the in-situ stress results obtained by indirect analysis of other logging data and the in-situ stress results obtained by direct calculation of rock mechanics parameters as the initial in-situ stress parameters, the numerical simulation of the in-situ stress field in the target block can be carried out respectively, and the two groups of in-situ stresses can be judged. The simulation accuracy of the stress data is used to select the initial input parameters of the in-situ stress field simulation that are most suitable for simulating the vertical well. In this way, for all the vertical wells in the target block, repeatedly looking for the in-situ stress analysis results of the simulation parameters of the in-situ stress field in the block that is most suitable for reproducing the actual fracturing construction process (that is, the smallest error) can improve the accuracy of the in-situ stress field model. The overall simulation accuracy is improved, so as to establish a fine in-situ stress field to ensure that the simulated fracture extension is close to the real fracture state during subsequent fracturing and casing deformation simulations.

Still taking the field application of Wei 202 block, a three-dimensional shale gas block in Weiyuan area, as an example.

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

Table 1 is a list of elastic parameters of the model after combining the above single well geological analysis results and experience. The modulus of elasticity varies with depth. The abaqus user subroutine is used in the calculation model to realize its TVD depth (TVD means vertical depth) dependent feature.

Table 1. List of elastic parameters of the model after comprehensive single well analysis results and experience

Calculating formation material parameters (that is, rock mechanical parameters) such as Young's modulus and initial in-situ stress-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 precise The accuracy of the initial input parameters of the stress field model.

In addition, the collapse pressure calculated according to the Mohr-Coulomb plastic yield condition in step S12 (such as curve c in Fig. 5) can be compared with the simulation results of the in-situ stress field model in this step, and the in-situ stress field does not have to be input Model.

As shown in Fig. 8, the finite element model grid of the in-situ stress field in block Wei 202 comes from the geological model grid established in step S11. The unit used is a three-dimensional 8-node linear unit, which is 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 loads of the model are gravity loads. The boundary conditions are the normal displacement constraints on the four sides and the normal displacement constraints on the bottom; the top is the ground and the free boundary.

Using the 3D finite element grid model in Figure 8, set the initial conditions, and establish the finite element model of the in-situ stress field of the target block. The initial conditions include the initial in-situ stress field and the initial pore pressure field. The pore pressure field only exists in the Wufeng Formation-Longmaxi Formation formation in the target formation, and the pore pressure coefficient in Block Wei 202 is 1.4g/cc. The initial in-situ stress field is set according to the in-situ stress components of a single well shown in Fig. 5, and the in-situ stress component parameters of each formation are set.

The distribution of the maximum horizontal principal compressive stress direction in the Wufeng Formation-Longmaxi Formation strata in the Wei 202 block obtained through numerical calculation is shown in Fig. 9 . It can be seen from Figure 9 that the direction of the maximum horizontal principal stress in the numerical results is about 130° in the upper left gentle zone of the Wei 202 block; the direction of the maximum horizontal principal stress in the lower right part of the block gradually transitions to an east-west direction 90°. This result is consistent with the azimuth angle measurement analysis results given in Fig. 6.

Figure 10A and Figure 10B respectively show the directions of the minimum horizontal principal compressive stress and the intermediate principal stress in the Wufeng Formation-Longmaxi Formation formation in Block Wei 202, and Figure 10C is the three-dimensional vector direction distribution diagram of the intermediate principal stress. From Fig. 10A, Fig. 10B and Fig. 10C, it can be seen that in the lower right/southeast position of block Wei 202, the intermediate principal stress is close to the vertical direction. 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 the single well geomechanics results in Fig. 5.

Fig. 11 is a cloud map of the three-dimensional numerical solution distribution of in-situ stress field in the reservoir unit of Well Wei 202 (TVD=2550m). The side length of the unit is 275 meters. The sign convention in the figure follows the sign convention of solid mechanics, that is, the tensile stress is positive and the compressive stress is negative. It can be seen from the figure that the magnitude of the stress gradually increases from northwest to southeast. At the same time, Table 2 shows the comparison between the numerical solution and the measured value of the in-situ stress in Well Wei 202. It can be seen from Table 2 that the magnitudes 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%.

Table 2 Comparison of numerical solutions and measured values of in-situ stress in vertical well Wei 202

Analyzing the above simulation results, it is found that the numerical solution of the magnitude and direction of the principal stress has certain errors from the measured values. 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 main 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 a margin of error.

Considering that the main purpose of the numerical results of the model is for the subsequent "prediction of casing deformation caused by fracturing", the preparation of the model parameters mainly emphasizes that the minimum principal stress result of the numerical solution is close to the measured value, that is, the minimum principal stress of the numerical solution is given priority. The principal stress results are closest to the measured values, and the numerical solution of the maximum horizontal principal stress direction angle is consistent with the trend of the middle value of the measured values” to ensure the rationality of the model.

Therefore, after comprehensive analysis and consideration, it is believed that the numerical results of the above-mentioned in-situ stress field can be constructed as a fine in-situ stress field in Block Wei 202, which can be used as input data for subsequent fracturing and casing deformation simulations.

Step S2. Based on the fine in-situ stress field of the block, establish a finite element model integrating geology-fracturing engineering-cement sheath-casing, and conduct three-dimensional finite element deformation and stress analysis on the casing string in the entire horizontal section of the horizontal well, and obtain Initial stress distribution of the casing string before fracturing.

Specifically: on the basis of the finite element model of the in-situ stress field of the block in step S1, the geometric models of the well, cement sheath, and casing are established, and the model data of fracturing construction are set to obtain the geology-fracturing engineering-cement sheath -The finite element model of the casing integration, and the numerical simulation results of the fine ground stress field of the block are used as the input data for the simulation of fracturing and casing deformation.

For example, the establishment of a finite element model for the integration of geology-fracturing engineering-cement sheath-casing may include the following: first establish the geometric model of the well, and then set the model data, the model data includes reservoir thickness distribution, horizontal section logging data , in-situ stress field distribution, designed fracturing parameters, perforation parameters, formation pressure coefficient, in-situ stress parameters, and rock mechanics parameters. Finally, various materials (including formation materials, cement sheath materials, and casing materials), and various Geometry (including formation geometry, cement sheath geometry and casing geometry), structural deformation and physical seepage two physical fields, fluid pressure load, ground stress load, gravity load, elastic mechanics model, and plastic mechanics model, to establish 3D finite element model of the well. For the integrated mathematical model of geology-fracturing engineering-cement sheath-casing to predict casing deformation, its basic theoretical model is the plastic loading yield criterion of metal, including the Tresca yield of formula (5) Criterion and the Mises (von Mises) yield criterion of formula (6). Both are yield criteria based on shear strength. In other words, the plastic deformation of metallic materials is shear plastic deformation.

τ _max ＝K Formula (5)

(σ ₁ -σ ₂ ) ² +(σ ₂ -σ ₃ ) ² +(σ ₃ -σ ₁ ) ² ＝2σ _s ² ＝6K ^2Formula (6)

Among them, σ ₁ , σ ₂ , σ ₃ are the three principal stresses, MPa, σ _s is the yield stress in MPa, and K is the shear yield strength of the material in MPa.

The tensile plasticity of the casing appears to be tensile plastic deformation macroscopically, but the microscopic mechanism is the shear plastic slip of metal crystals. Based on this, considering the environment in which the casing is located, it is considered that: in fracturing construction, along the axis of the horizontal section, if there are defect points around the casing where the shear load is the largest (for example, defect points with gamma anomalies, poor cementing quality defect points), the risk of casing deformation at these defect points is high. These places should avoid falling into the area of maximum shear load.

The final model of "geology-fracturing engineering-cement sheath-casing integration" includes:

1) A variety of materials, a variety of geometric shapes;

2) Two physical fields of structural deformation and seepage;

3) fluid pressure load, ground stress load, gravity load;

4) Elastic mechanics constitutive model, plastic mechanics constitutive model.

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

K(u)·u=F

Here the variables are defined as:

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

Step S3, performing three-dimensional finite element deformation and stress analysis on the casing string after fracturing through the reservoir, calculating the change of the in-situ stress field caused by fracturing, and finding out the position distribution of the shear load applied to the casing.

Specifically, model parameters can be set for the target interval of the casing string in the finite element model of the integrated finite element model of geology-fracturing engineering-cement sheath-casing according to the designed fracturing construction parameters, and reservoir fracturing can be carried out Numerical simulation of the target zone to calculate the change in the in-situ stress field caused by fracturing in the target interval, and find the distribution of the location where the shear load is applied to the casing.

Step S4. Carry out an integrated casing deformation analysis of the combination of geology-cementing-casing of the horizontal well, the analysis includes the distribution analysis of the gamma curve in the horizontal section of the well trajectory, the distribution of the cementing quality and the sound amplitude curve in the horizontal section of the well trajectory Analysis, analysis of fracturing construction pressure curves in the horizontal section of well trajectory, analysis of microseismic monitoring results in horizontal wells, and analysis of shear stress changes outside the wellbore in the horizontal section of well trajectory through simulation calculation.

Step S5. According to the results of casing deformation analysis, predict the position of casing deformation induced by fracturing, and the position of casing deformation includes the position of local abnormal protrusion of gamma curve, the position of abnormal cementing homogeneity, and the peak of construction pressure The point of maximum shear load caused by the fracturing stage where the value is located, and the outer edge of the formation fracture zone caused by fracturing.

On the basis of a large number of studies, the present invention confirms three major influencing factors of casing deformation induced by fracturing, which are respectively geological factors, well cementing factors and construction engineering factors.

Among them, the geological factor refers to the asymmetry of the formation stiffness and obvious local changes. The external shear force of the casing located in this area is greater than that of other locations, so the probability of casing deformation is high. Before the fracturing operation, the location where the formation stiffness is asymmetric and the local variation is obvious in the horizontal section of the well trajectory can be identified by analyzing the gamma ray log curve. For example, when the gamma ray log curve in the horizontal section of the well trajectory has a local anomalous bulge, it can be considered that the information marked by this feature is asymmetric formation stiffness and local variation anomalies. The basis for judging the local abnormal protrusion of the gamma curve may be that the local gamma value is greater than 200GAPI.

In addition, at the outer edge of the formation fragmentation zone caused by fracturing, there is also the situation that the formation stiffness is asymmetrical and the local stiffness changes significantly, and the casing at this position is more likely to be deformed. However, this location can only be found after obtaining corresponding well logging data after construction (during or after fracturing construction). Therefore, in order to predict in advance the outer edge of the stratum fragmentation zone produced by fracturing, and identify the positions where stiffness asymmetry and local stiffness of the stratum in the horizontal section of the well trajectory are likely to occur after fracturing construction, the position where the local stiffness changes significantly, the present invention can be used in the fracturing construction design stage. The corresponding casing deformation here is analyzed by numerical simulation of reservoir fracturing. The shear localized zone caused by fracturing can be obtained from the numerical simulation results of reservoir fracturing, and the shear localized zone can be regarded as the stratum fragmentation 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 formation injection pore pressure and the in-situ stress field. There is also a higher chance of casing deformation in the region than in other locations. In order to verify the accuracy and precision of the shear localization zone obtained by simulation, the position of the outer edge of the formation fracture zone generated by fracturing can be determined by analyzing the results of horizontal well microseismic monitoring.

For another example, before fracturing, it is possible to judge possible natural fracture areas through geological ant body data, lost circulation data, etc., and to predict possible stratum fragmentation areas through the fracture area.

The cementing factor refers to the abnormal cementing homogeneity, that is, the local variation of the cementing quality is large, and there are local poor quality points. The cementing in this area is uncemented or partially cemented and has poor shear resistance. There is a high chance of casing deformation. Before fracturing, the location of poor cementing quality in the horizontal section of the well trajectory can be identified by analyzing the cementing quality and the sound amplitude curve. For example, when the cementing quality and sound amplitude curves in the horizontal section of the well trajectory show local obvious changes in the cementing sound amplitude, it can be considered that the information identified by this feature is abnormal cementing homogeneity. The basis for judging the abnormality of the cementing homogeneity can be that the local acoustic amplitude is higher than the interface with poor cement bonding, and the local evaluation result of the cementing quality is poor.

Construction engineering factors mean that the pressure of fracturing construction is too high, exceeding the allowable range, and the local external shear force of the casing in this area is obviously higher than that of other locations, so the probability of casing deformation is high. During the fracturing construction process, the position 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 the pressure surge caused by sand plugging, and it can be considered that the information identified by this feature is that the pressure of fracturing construction exceeds the allowable range. Here, the peak value of the construction pressure curve refers to a sharp increase or sudden drop in pressure, which causes obvious fluctuations in the pressure curve. The basis for judging 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 sudden drop is greater than 10 MPa/min, and the pressure change curve is not a straight line.

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

(1) Analyze the gamma logging curve of the horizontal section of the well trajectory of the target well, find out the position of the casing string in the horizontal section of the well trajectory corresponding to the local gamma value greater than 200GAPI in the gamma logging curve, and predict it as the pressure location of crack-induced casing deformation.

(2) Analyze the cementing quality and sound amplitude curves of the horizontal section of the well trajectory of the target well, find out the interface where the local sound amplitude is higher than the cement bond difference in the cementing quality and sound amplitude curves, and the local evaluation result of the cementing quality is The location of the casing string in the horizontal section of the well trajectory corresponding to the difference is predicted as the location of casing deformation induced by fracturing.

(3) Use the parameters in the fracturing construction design stage to carry out numerical simulation of reservoir fracturing for the target well, calculate the change of in-situ stress field caused by fracturing, predict the shear localization zone caused by fracturing, and localize the shear The location of the casing string in the horizontal section of the well trajectory corresponding to the zone is predicted to be the location of casing deformation induced by fracturing.

During and after the fracturing operation, the maximum shear load point caused by the fracturing section where the peak value of the operating pressure is located can be found by analyzing the fracturing operation pressure curve of the horizontal section of the well trajectory of the target well ( MaximumShear Loading Points, MSLP), and predict this MSLP point as the location of casing deformation induced by fracturing.

For the target well, the above four methods can be used to analyze and predict the possible deformation position of the casing before fracturing and during the fracturing process, and the predicted casing deformation position can be calibrated on the casing to obtain the fracturing induced Predicted plot of casing deformation location.

For example, take the field application of the 204H12-5 well section in the 3D shale gas block in the Weiyuan area as an example.

Fig. 12 is the curve of casing damage (casing deformation) in well 204H12-5 and the analysis graph of gamma logging curve. Among them, curve a in Fig. 12 is the maximum inner diameter, curve b is the average inner diameter, and curve c is the smallest inner diameter. Fig. 13 is the sound amplitude and evaluation diagram of the cementing quality of Well 204H12-5. Among them, curve A in Fig. 13 is the casing collar value, curve B is the borehole diameter value, and curve C is the natural gamma ray value.

Before the fracturing operation, analyzing the gamma logging curve of the target well 204H12-5 (as shown in Figure 12), it was found that the gamma value at the downhole depths of 3100m and 3200m suddenly increased from 70API to 190API, indicating these two points It is the position where the gamma curve is abnormally raised, and it may be the position where the sleeve is deformed. At the same time, analyzing the cementing quality and sound amplitude curve of the target well 204H12-5 (as shown in Figure 13), it is found that the sound amplitude has local obvious changes at the depth after the downhole depth of 3200m, that is, the sound amplitude has large fluctuations Undulation, which shows that the cementing quality of the outer interface at this position is poor in homogeneity, which may be the position of casing deformation. Therefore, the comprehensive analysis of logging data, natural fracture distribution data and fracturing operation parameters shows that the formation stiffness at the downhole depth of 3200m is asymmetrical, and the cementing quality is poor, and casing deformation is prone to occur, which is predicted to be fracturing-induced casing. deformed position.

During the actual production application of the target well 204H12-5, it was found that the casing string at the predicted position was deformed. As shown in Fig. 12, in the region with a downhole depth of about 3200m, the minimum inner diameter (ie curve c), average inner diameter (ie curve b) and maximum inner diameter (ie curve a) of the casing decrease sharply, that is, at 3200m downhole depth is The location where casing deformation occurs. In addition, it can also be seen from Fig. 13 that at the depth position after the downhole depth of 3100m, the borehole diameter curve (ie, curve B) changes from flat to up and down fluctuations, which indicates that casing deformation occurs after the downhole depth of 3100m.

This shows that the position where the local anomalous bulge of the gamma ray curve appears in the logging data and the position where the cementing homogeneity is abnormal can be predicted as the position of the casing deformation induced by fracturing.

As another example, take the field application of the Yang 105H3-2 well section in the sun structure area as an example to illustrate.

Fig. 14 is the fracturing construction curve of the seventh section (downhole 2935-2855m) of Jingyang 105H3-2. Curve a in Figure 14 is the well pressure of Yang 105H3-2, curve b is the construction displacement, and curve c is the sand concentration.

In the process of fracturing the seventh section of the target well Yang 105H3-2 (downhole 2935-2855m), analyzing the fracturing construction curve (as shown in Figure 14), it can be found that: during the entire construction period, at the position above the dotted line , There were multiple abnormal peaks in the construction pressure, which indicated that the construction pressure in the seventh section during the construction process was too large, exceeding the allowable range, and it may be the location where the casing deformed. At the same time, using the fracturing operation parameters of the 7th stage to simulate the fracturing of the water-influent reservoir, the analysis and simulation results show that the 7th stage is located in the shear localization zone, which may be the location of the casing deformation. Therefore, comprehensive analysis of logging data, natural fracture distribution data, and fracturing construction parameters indicates that the position at a downhole depth of 2935-2855m is the formation fragmentation zone caused by fracturing, and the construction pressure is too high, exceeding the allowable range, and casings are prone to occur Deformation, predicted to be the location of fracturing-induced casing deformation.

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

This shows that the location of the abnormal peak value in the construction pressure curve and the location of the shear localization zone in the numerical simulation of reservoir fracturing can be predicted as the location of casing deformation induced by fracturing.

As another example, take the field application of the 202H14-3 well section in the 3D shale gas block in the Weiyuan area as an example.

Before the fracturing operation, the ant body map of the well 202H14-3 can be analyzed to judge the possible natural fracture area, and the possible stratum fragmentation area can be predicted through the fracture area. Figure 15 is a well ant body diagram of well 202H14-3. As shown in Fig. 15, it can be seen that at the 21st-23rd section, that is, the position of 3068-3340m downhole (the position of the dotted circle frame), there is a natural fracture zone in the wellbore, and the casing at this position is in the fractured formation zone. At the same time, using the fracturing operation parameters of well 202H14-3 to simulate and calculate the fracturing of the water-influent reservoir, the analysis and simulation results found that the 21-23 sections are located in the shear localization zone, which verifies the location of 3068-3340m downhole (that is, The position of the dotted circle frame in Figure 15) is the position of the fractured zone of the natural fracture zone, which is prone to casing deformation.

During the actual production application of the target well 202H14-3, it was found that after the construction of the 10th section of the well (that is, the 4017-4084m downhole), the pumping bridge plug was blocked at 3290.81m, indicating that the casing at the 3068-3340m downhole position was blocked. out of shape.

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

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

(1) In the present invention, the well logging data and rock mechanical parameters of a single well are respectively input into the in-situ stress field model for simulation calculation, and the simulation results are repeatedly compared and verified with the microseismic data when the fracturing is actually implemented, thereby obtaining a relatively Realistically reproduce the in-situ stress field distribution of the target block and the fine in-situ stress field of fracture direction.

(2) The present invention uses the fine in-situ stress field of the block as the 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 , which ensures the accuracy of the input in-situ stress field, and improves the accuracy of predicting the casing deformation position using the integrated finite element model of geology-fracturing engineering-cement sheath-casing.

(3) The present invention comprehensively analyzes the various factors affecting the deformation of the fracturing casing, organically links various factors of the casing deformation, conducts a comprehensive integrated analysis, and has a targeted effect on the fracturing induced casing in the high geostress area. Predicting the deformation position of the casing is conducive to the subsequent proposal of feasible technical measures and the development of technical solutions for casing deformation prediction and prevention.

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

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

Although the invention has been described above with reference to the exemplary embodiments and accompanying drawings, it will 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 (15)

1. A method for predicting fracture-induced casing deformation locations based on multidimensional information, comprising the steps of:

acquiring a single-well geological analysis result and a maximum horizontal principal stress direction angle based on the logging data of a target block, and establishing a block fine geostress field;

establishing a geological-fracturing engineering-cement sheath-casing integrated finite element model based on the block fine geostress field, and performing three-dimensional finite element deformation and stress analysis on the casing string in the full horizontal section of the horizontal well to obtain the initial stress distribution of the casing string before fracturing;

performing three-dimensional finite element deformation and stress analysis on the casing string after the fracturing of the reservoir, calculating the change of a ground stress field caused by the fracturing, and finding out the position distribution of applying a shearing load to the casing string;

performing geological-well cementation-casing combined integrated casing deformation analysis on the horizontal well, wherein the analysis comprises the gamma curve distribution analysis of a horizontal section of a well track, the well cementation quality and sound amplitude curve distribution analysis of the horizontal section of the well track, the fracturing construction pressure curve analysis of the horizontal section of the well track, the microseism monitoring result analysis of the horizontal well and the simulation calculation of the change analysis of the shearing force outside the shaft of the horizontal section of the well track;

and predicting the positions of the fracture-induced casing deformation according to the casing deformation analysis result, wherein the positions of the casing deformation comprise the positions of local abnormal bulges of the gamma curve, the positions of well cementation homogeneity abnormality, the maximum shear load point caused by a fracture section where a construction pressure peak value is located, and the outer edge of a stratum fracture area caused by fracturing.

2. The method of predicting fracture-induced casing deformation locations based on multi-dimensional information of claim 1, wherein the establishing a block-refined geostress field comprises the steps of:

according to a technical method of 'well-seismic combination', on the basis of seismic wave data, a three-dimensional geological model of a target block is established by combining single-well horizon information;

calculating rock mechanical parameters according to the logging data of a single well in the target block, and performing single-well geomechanical analysis on other logging data and rock mechanical parameters to obtain a single-well geomechanical analysis result;

comprehensively analyzing information of a world stress map, single well measurement information of existing wells and horizontal well fracturing microseism monitoring information in a target block to obtain a maximum horizontal principal stress direction angle in the target block;

introducing a three-dimensional geological model, establishing a finite element model of the geostress field of a target block, verifying the simulation result of the geostress field of the target block based on the single well geological analysis result and the actual measurement result of the microseism of the existing well during the fracturing construction period, and constructing a block fine geostress field by solving the numerical value of the geostress field qualified through verification.

3. The method for predicting the location of fracture-induced casing deformation based on multi-dimensional information as claimed in claim 2, wherein the building of the three-dimensional geological model of the target block based on seismic wave data in combination with single-well horizon information comprises: and establishing the grid geometric dimension of a geological model according to the three-dimensional seismic wave data, dividing the stratum and defining the size of grid units of each stratum, wherein the grid units of the stratum where the reservoir is located are smaller than those of other strata.

4. The method for predicting the deformation position of the fracturing-induced casing based on the multidimensional information as claimed in claim 3, wherein the ratio of the thickness of the grid cells of the stratum where the reservoir is located to the thickness of the grid cells of the other strata is 1:18 to 1:30.

5. the method of claim 2, wherein the other log data comprises gamma rays, compressional sonic time duration and density of the formation, and the rock mechanics parameters comprise Young's modulus, poisson's ratio, cohesion and internal friction angle.

6. The method of predicting fracture-induced casing deformation locations based on multidimensional information of claim 2, wherein the single well geological analysis results comprise geostress results obtained by indirect analysis using other well log data and geostress results obtained by direct calculation using rock mechanics parameters.

7. The method for predicting the location of a fracture-induced casing deformation based on multidimensional information as recited in claim 2, wherein the comprehensively analyzing information of a world stress map, single well measurement information of existing wells, and horizontal well fracture micro-seismic monitoring information in a target block to obtain a maximum horizontal principal stress direction angle in the target block comprises:

judging the maximum horizontal principal stress direction angle of the area to which the target block belongs by using a world stress map, and determining the interval range to which the maximum horizontal principal stress direction angle in the target block belongs;

according to the information measured by the single well, the range of the maximum horizontal principal stress direction angles of different structural parts in the target block is judged, and the change rule of the maximum horizontal principal stress direction angles in the target block along with the terrain is determined;

and analyzing the microseism monitoring information, 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 by combining the analysis result of the microseism monitoring information, and/or supplementing and correcting the value of the maximum horizontal principal stress direction angle in the target block of the leakage area lost by using the world stress map and the single-well measurement information.

8. The method of predicting fracture-induced casing deformation locations based on multi-dimensional information of claim 7, wherein the analyzing microseismic survey information comprises:

judging the position of a single color strip distribution in the micro-seismic event points of the horizontal well in the target block as a seam network strip generated by the same fracturing segment, and judging the direction angle of the seam network strip as the direction angle of the maximum horizontal main stress of the position;

determining the position of a color strip which consists of a plurality of colors and is distributed beyond the range of a reservoir layer in the micro-seismic event points of the horizontal well in the target block as the position of a natural fracture;

and judging the condition that micro-seismic response points appear in the micro-seismic event points of the horizontal well in the target block and are distributed in a sheet or a ball shape as that the maximum horizontal principal stress directionality of the position is not obvious, and the direction of the minimum horizontal principal stress is close to the direction of the vertical principal stress.

9. The method for predicting the fracture-induced casing deformation location based on the multi-dimensional information as set forth in claim 2, wherein the establishing a finite element model of the ground stress field of the target block comprises: setting units adopted by a geological model grid as three-dimensional 8-node linear units, setting the load of a ground stress field finite element model as a gravity load, setting boundary conditions of four sides and the bottom of the ground stress field finite element model as normal displacement constraints, setting boundary conditions of the top as a free boundary, and setting initial ground stress parameters and initial pore pressure parameters as initial conditions.

10. The method of predicting fracture-induced casing deformation locations based on multidimensional information of claim 9, wherein the initial geostress parameters comprise triaxial geostress principal components and a maximum horizontal principal stress azimuth angle obtained from single well geomechanical analysis.

11. The method for predicting the fracture-induced casing deformation position based on the multi-dimensional information as claimed in claim 6, wherein the verifying the simulation result of the geostress field of the target block based on the single-well geological analysis result and the actual microseism measurement result of the existing well during the fracture construction, and numerically solving the qualified geostress field into a block fine geostress field comprises the following steps:

for each single well of the target block, respectively utilizing the crustal stress result obtained by indirectly analyzing other logging data and the crustal stress result obtained by directly calculating rock mechanical parameters as initial crustal stress parameters to carry out numerical simulation on the crustal stress field of the target block to obtain a corresponding crustal stress field numerical solution;

and comparing the two kinds of numerical solutions of the geostress field with the errors of the actual measurement values of the geostress field of the existing well fracturing construction, and taking the numerical solution with a smaller error with the actual measurement values of the geostress field as the block fine geostress field.

12. The method for predicting the location of fracture-induced casing deformation based on multidimensional information as recited in claim 1, wherein the local anomalous projections in the gamma curve are determined based on a local gamma value greater than 200GAPI.

13. The method for predicting the fracture-induced casing deformation location based on the multidimensional information as recited in claim 1, wherein the determination of the well cementation homogeneity abnormality is based on an interface with a local acoustic amplitude higher than a poor cement bond and a poor local evaluation result of the well cementation quality.

14. The method for predicting the deformation position of the fracturing-induced casing based on the multidimensional information as claimed in claim 1, wherein the judgment of the maximum shear load point caused by the fracturing section where the construction pressure peak value is located is based on that the amplitude of the sharp increase or the sharp decrease of the pressure curve is more than 10MPa/min and the pressure curve is not a straight line.

15. The method for predicting the location of fracture-induced casing deformation based on multidimensional information of claim 1, wherein the location of the fracture-induced formation fracture zone is determined from pre-fracture geological data and/or numerical simulations of reservoir fracturing.

Images