A stress analysis method based on structural deformation

Abstract

The present invention relates to the technical field of structural analysis in oilfield development, and particularly relates to a stress analysis method based on structural deformation, comprising the following steps: S1. Select a profile, and based on the three-dimensional seismic data of the profile, finely interpret the strike-slip fault structure and analyze the geometric shape and structural deformation characteristics; S2. Obtain the line dip angle data and the trace dip angle data of the profile; S3. Calculate the curvature of the formation in combination with the geological background and rock mechanics parameters of the work area to obtain the three-dimensional surface deformation data of the formation; S4. Calculate the tectonic stress field of the formation based on the three-dimensional surface deformation data of the formation; S5. Segmentally describe the stress properties inside the fault-karst body. The present invention can accurately depict the tensile, translational, and compressional-shearing phenomena caused by the superposition of fractures inside the fault-karst body, and can further judge the pull-apart and compressional uplift regions within the same fracture, and is beneficial to the screening of hydrocarbon accumulation sections, which is of great significance for improving the recovery rate of hydrocarbon enrichment units.

Description

Technical Field

[0001] The present invention relates to the technical field of structural analysis in oilfield development, and particularly relates to a stress analysis method based on structural deformation, which is applied to work such as carbonate reservoir prediction and subsequent reservoir development. Background Technique

[0002] Rocks are usually affected by formation stress. When the stress exceeds the compressive strength of the rock itself, fractures will occur in the weak zones of the rock, forming fracture structures, including faults, joints, fissures, etc. Sometimes several forms of fracture structures coexist to form a fracture zone. The development practice of Tahe Oilfield shows that the fracture zone not only has an obvious control effect on hydrocarbon accumulation and reservoir formation, but also the fracture system and associated geological bodies such as compressive folds, thrusts, and torsional deformations, after experiencing the superimposed transformation of karstification, form a karst fracture-vug system with diverse shapes. Later, hydrocarbons vertically migrate along the fracture, and after charging and forming reservoirs, a special type of fault-karst reservoir is formed. Due to the multi-stage tectonic movements experienced by the deep and large fault zone in the Ordovician of Tahe, on the same fault zone, affected by the differences in in-situ stress and karstification, there are obvious segmentations in different sections, the internal structure of the fault-karst reservoir is complex, the reservoir space is extremely heterogeneous vertically and horizontally, and the development characteristics are very different, which affects the development effect. Therefore, with the in-depth development of the oilfield, it is necessary to conduct fine reservoir description and three-dimensional geological modeling for the fault-karst type reservoir.

[0003] For the fault-karst reservoir, a "fault-karst outline and internal structure" characterization technology of "structural tensor + porosity inversion + ant body" has been formed in the early stage. To a certain extent, this method can intuitively display the internal structure information of the fault-karst body. However, development practice shows that the hydrocarbon enrichment degrees in different segments of the same fault zone vary greatly, which is related to the segmentation of the strike-slip fault zone. According to the stress state, strike-slip faults can be divided into three types: tensile segment, compressive segment, and translational segment. For the same fault zone, the tensile segment has the richest hydrocarbons, followed by the compressive segment, and the translational segment is the worst. Moreover, the previous fault-karst body characterization technology is not sufficient to reflect the stress property differences of the fault zone, restricting the fine description level of the fault-karst reservoir.

[0004] Patent CN111814290A discloses a method for identifying the maximum paleo-stress direction during the strike-slip fault development period, which includes the following steps: making a fine interpretation of the strike-slip fault, dividing the strike-slip fault into superimposed uplift segments, superimposed tensile segments and translational segments, selecting typical overlapping segments, identifying the local principal stress direction, and establishing a numerical simulation geological and mechanical model of the stress field for the typical overlapping segments; loading the regional stress field in different directions on the model within the range of the regional stress field direction of the strike-slip fault; determining the direction of the maximum paleo-stress during the strike-slip fault development period. This method identifies the maximum paleo-stress direction during the strike-slip fault development period by establishing the relationship between the strike direction of secondary faults inside the overlapping segments of the strike-slip fault and the corresponding regional stress field direction, which has important guiding significance for understanding the regional tectonic background, analyzing the origin and evolution of the strike-slip fault, and exploring the development law of the derivative fracture and fracture system in different parts of the strike-slip fault and its role in controlling reservoirs and hydrocarbon accumulation. However, the blowout and leakage rate of the fault dissolution body of this method still needs to be improved, and the accuracy of depicting the internal stress of the fault still needs to be improved.

[0005] Patent CN112817043A discloses a method for identifying weak strike-slip faults based on the tectonic lithology stress field, which includes the following steps: S1 establishing the relational expressions of curvature, lithology parameters, tectonic deformation and stress field; S2 establishing the connection between the in-well P-S wave data and seismic attributes to obtain the Poisson's ratio data volume and Young's modulus data volume, where the Young's modulus is E and the Poisson's ratio is ν; S3 taking the derivative of the 3D seismic data volume to obtain the 3D curvature bodies with curvatures of Kx, Ky, and Kxy respectively; S4 substituting the Poisson's ratio data volume and Young's modulus data volume obtained in step S2 and the 3D curvature bodies obtained in step S3 into the formula obtained in step S1 to obtain the 3D tectonic lithology stress field data volume; and S5 identifying weak strike-slip faults based on the tectonic lithology stress field data volume obtained in step S4. By establishing the curvature-strain-stress formula, the organic combination of well-seismic information and tectonic stress field is realized, and by means of multiple linear fitting, the tectonic stress field can be quickly obtained. However, the tectonic stress field obtained by this method is a two-dimensional plane stress field.

[0006] Therefore, based on the above-mentioned prior art, the present application proposes a stress analysis method based on tectonic deformation, which forms a set of methods for describing the internal stress properties of faults by subdividing the internal structure of the main fault, the relationship between secondary faults and the main fault, and screening of local favorable hydrocarbon accumulation segments, so as to improve the accuracy of depicting the fault dissolution body. Summary of the Invention

[0007] In order to solve the above problems, the present invention provides a stress analysis method based on tectonic deformation, aiming to analyze the tectonic stress field of typical fault dissolution bodies, distinguish the stress properties inside the faults, analyze the influence of different stress backgrounds on the characterization of the effective reservoir space of the fault dissolution bodies, macroscopically compare and analyze the main faults and secondary faults, and then qualitatively judge the scale of the reservoir body.

[0008] To achieve the above object, the technical solution of the present invention is as follows:

[0009] A stress analysis method based on structural deformation includes the following steps:

[0010] S1. Select a profile perpendicular to the strike of the fault-solution body development zone in the work area where the fault-solution body develops. According to the three-dimensional seismic data of the profile, finely interpret the strike-slip fault structure and analyze the pull-apart, translation, and compressional-shear morphologies of the strike-slip fault;

[0011] S2. Combine the structural interpretation information and lithology information, and use the dip scanning technology to obtain the line dip data and trace dip data of the profile;

[0012] S3. Combine the geological background and rock mechanics parameters of the work area to calculate the curvature of the formation and obtain the three-dimensional surface deformation data of the formation;

[0013] S4. Based on the three-dimensional surface deformation data of the formation, use different bin grids to test the stress parameters of the fault-solution body and calculate the tectonic stress field of the formation;

[0014] S5. Combine the tectonic stress field of the formation and conduct a sectional description of the stress nature inside the fault-solution body.

[0015] Preferably, step S1 includes:

[0016] S11. Select a profile perpendicular to the strike of the fault-solution body development zone in the work area where the fault-solution body develops, and extract the prestack depth migration data of the profile;

[0017] S12. According to the structural deformation characteristics of different parts, divide the strike-slip fault into superimposed uplift segments, superimposed pull-apart segments, and translation segments, and determine the segmentation of the fault and the overlapping form between adjacent segments.

[0018] Preferably, step S2 includes:

[0019] S21. Construct a geometric model according to the geometric morphologies of superimposed tension, translation, and compressional-shear;

[0020] S22. Combine the geometric model with the rock velocity and rock density of the strike-slip fault, and use the dip scanning technology to conduct a structural gradient detection on the prestack depth migration data of the profile to obtain the line dip data and trace dip data of the formation.

[0021] Preferably, step S3 includes:

[0022] S31. According to the geological background of the work area, determine the mechanical parameters of the surrounding rock in the work area;

[0023] S32. Use the minimum QR decomposition algorithm to calculate the structural curvature of the formation and obtain the three-dimensional curvature data of the formation.

[0024] S33. According to Hooke's law and the linear relationship between stress and strain, obtain the three-dimensional surface deformation model of the formation.

[0025] Preferably, step S4 includes:

[0026] S41. Divide the three-dimensional surface deformation model into surface element grids.

[0027] S42. Apply a certain stress σ1 to the three-dimensional surface deformation model.

[0028] S43. Calculate the three-dimensional tectonic stress field A1 of the formation.

[0029] S44. Apply certain stresses σ2, σ3, σ4... σ n to the three-dimensional surface deformation model respectively, and correspondingly calculate the three-dimensional tectonic stress fields A2, A3, A4... A n .

[0030] Preferably, step S5 includes:

[0031] S51. Extract the stress plane field of the layer to be analyzed from the tectonic stress field to obtain the tensile stress, tensor thickness and comprehensive characterization map of the ant body of the layer to be analyzed.

[0032] S52. Qualitatively determine the development area of high-quality reservoirs and favorable hydrocarbon accumulation sections according to the comprehensive characterization map.

[0033] S53. Analyze the influence of different stress backgrounds on the characterization of the effective reservoir space of fault dissolution bodies according to the comprehensive characterization maps under different stress backgrounds, and qualitatively determine the segmentation within the same fault, the superimposed tensile segment and the superimposed compression uplift segment.

[0034] Preferably, the dip angle scanning technique in step S22 is a scanning method based on the gradient structure tensor.

[0035] Preferably, the mechanical parameters of the surrounding rock in step S31 include formation velocity, Young's modulus, Poisson's ratio, formation density and internal friction coefficient.

[0036] Preferably, the surface element grid in step S41 is one of 100 m × 100 m, 300 m × 300 m, and 600 m × 600 m.

[0037] Compared with the prior art, the beneficial effects of the present invention are:

[0038] The present invention comprehensively utilizes the three-dimensional tectonic stress field and the planar stress field, combines the simulations of different surface element meshes and different stress backgrounds to form a set of three-dimensional tectonic stress field data, which can accurately depict the distribution of the local stress field within the fault zone, and further can judge the pull-apart and compression uplift regions within the same fault, and is conducive to the screening of oil and gas enrichment sections, which is of great significance for improving the recovery rate of oil and gas enrichment units. The tensile stress background is one of the characteristics of the favorable reservoirs of fault dissolution bodies. Combined with the productivity analysis of characteristic wells, it is applied in the main fault zone of TH12518, the main fault zone of S94-1, and the well area of TH12402. This technology provides technical support for fault dissolution body fracture carving, well pattern adjustment, water injection and gas injection. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a flowchart of the method of the present invention.

[0040] Figure 2 It is a schematic diagram of the pre-stack depth migration data of the section described in the present invention.

[0041] Figure 3 It is a schematic diagram of the line dip angle of the formation described in the present invention.

[0042] Figure 4 It is a schematic diagram of the trace dip angle of the formation described in the present invention.

[0043] Figure 5 It is a schematic diagram of the three-dimensional tectonic stress field of the formation described in the present invention.

[0044] Figure 6 It is a comprehensive characterization diagram of the layer to be analyzed in the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0045] The technical solutions of the present invention will be clearly described below in conjunction with the drawings. Obviously, the described embodiments are not all the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention. It should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0046] As Figure 1 shown, the present invention provides a stress analysis method based on tectonic deformation, including the following steps:

[0047] S1. Select a profile perpendicular to the strike of the fault-karst body development zone in the work area. Based on the 3D seismic data of the profile, conduct a detailed interpretation of the strike-slip fault structure and analyze the pull-apart, translational, and compressional-torsional morphologies of the strike-slip fault;

[0048] Specifically include:

[0049] S11. Select a profile perpendicular to the strike of the fault-karst body development zone in the work area and extract the pre-stack depth migration data of the profile;

[0050] S12. According to the structural deformation characteristics of different parts, divide the strike-slip fault into superposed uplift segments, superposed pull-apart segments, and translational segments, determine the segmentation of the fault and the overlapping form between adjacent segments.

[0051] S2. Combine the structural interpretation information and lithology information, and use the dip scanning technique to obtain the line dip data and trace dip data of the profile;

[0052] Specifically include:

[0053] S21. Construct a geometric model according to the geometric morphologies of superposed tension, translation, and compressional torsion;

[0054] S22. Combine the geometric model with the rock velocity and rock density of the strike-slip fault, and use the dip scanning technique to conduct a structural gradient detection on the pre-stack depth migration data of the profile to obtain the line dip data and trace dip data of the formation.

[0055] S3. Combine the geological background of the work area and the rock mechanics parameters to calculate the curvature of the formation and obtain the three-dimensional surface deformation data of the formation;

[0056] Specifically include:

[0057] S31. According to the geological background of the work area, determine the mechanical parameters of the surrounding rock in the work area;

[0058] S32. Use the minimum QR decomposition algorithm to calculate the structural curvature of the formation and obtain the three-dimensional curvature data of the formation;

[0059] S33. According to Hooke's law and the linear relationship between stress and strain, obtain the three-dimensional surface deformation model of the formation.

[0060] S4. Based on the three-dimensional surface deformation data of the formation, use different bin meshes to test the stress parameters of the fault-karst body and calculate the tectonic stress field of the formation;

[0061] Specifically include:

[0062] S41. Divide bin meshes for the three-dimensional surface deformation model;

[0063] S42. Apply a certain stress σ1 to the three-dimensional surface deformation model;

[0064] S43. Calculate the three-dimensional tectonic stress field A1 of the formation;

[0065] S44. Apply certain stresses σ2, σ3, σ4... σ n to the three-dimensional surface deformation model respectively, and correspondingly calculate the three-dimensional tectonic stress fields A2, A3, A4... A n .

[0066] S5. Combine the tectonic stress field of the formation and conduct a stress property sectional description of the inside of the fault-karst body;

[0067] Specifically, it includes:

[0068] S51. Extract the stress plane field of the layer to be analyzed from the tectonic stress field to obtain the tensile stress, tensor thickness and comprehensive ant body characterization map of the layer to be analyzed;

[0069] S52. Qualitatively determine the high-quality reservoir development area and favorable hydrocarbon accumulation section according to the comprehensive characterization map;

[0070] S53. Analyze the influence of different stress backgrounds on the characterization of the effective reservoir space of the fault-karst body according to the comprehensive characterization maps under different stress backgrounds, and qualitatively determine the sectional properties, superimposed tensile sections and superimposed compressive uplift sections within the same fault.

[0071] Preferably, in step S22, the dip angle scanning technology is a scanning method based on the gradient structure tensor.

[0072] Preferably, the surrounding rock mechanical parameters in step S31 include formation velocity, Young's modulus, Poisson's ratio, formation density and internal friction coefficient.

[0073] Preferably, the surface element grid in step S41 is one of 100 m × 100 m, 300 m × 300 m, and 600 m × 600 m.

[0074] Example

[0075] In this example, the geology of the western contiguous area of Tahe Oilfield is selected as an example to analyze the changes in the characterization of the effective reservoir space of the fault-karst body under different stress backgrounds. The specific method is as follows:

[0076] 1) Select the work area where the fault-karst body develops as the application work area, and select a typical profile T76 layer perpendicular to the strike of the fault-karst body development zone in the work area for analysis. As Figure 2Shown is the pre-stack depth migration data profile of the said section, from which the strike-slip fault structure is interpreted in detail to analyze the geometric morphology and tectonic deformation characteristics; under the action of compressive and torsional forces, the strike-slip fault forms a uplifted morphology; in the state of tensile force, the fault is a sunken morphology; if neither of them exists, it is in a translational state. The strike-slip fault can be divided into superimposed uplifted segments, superimposed tensile segments and translational segments according to different deformation characteristics, and the segmentation of the fault and the overlapping form between adjacent segments can be determined.

[0077] 2) Based on the elastic thin plate theory, combined with structural interpretation information and lithological information such as rock velocity and density, through the formation dip scanning technology, the structural gradient of the pre-stack depth migration data is detected to obtain line dip data and trace dip data. As Figures 3 - 4 shown, the line dip data and trace dip data can better depict the spatial morphology and distribution characteristics of the fault structure.

[0078] 3) Using the surface fitting least QR decomposition algorithm, the line dip and trace dip data are used to simulate the tectonic stress field to obtain curvature body data; the curvature distribution is used to evaluate the bending degree of the structure. The more severely the formation is deformed under stress, the greater its degree of fracture, and the greater the curvature value.

[0079] 4) The obtained spatial curvature deformation body is divided by a surface element grid of 300×300 m. Other surface element grids can also be used. A certain stress is applied to the spatial curvature deformation body of the divided grid to calculate the three-dimensional tectonic stress field of the Tahe fault-karst body, as Figure 5 shown;

[0080] 5) Extract the stress plane field of the T76 horizon to obtain the comprehensive characterization map of the T76_T80 tensile stress, tensor thickness and ant body as shown in Figure 6 shown. It can be seen that within the boundary of the fault-karst body, the change in the degree of internal fragmentation of the fault-karst body and the distribution of high-quality reservoirs are clearly depicted, and there is a good matching relationship between the area with high degree of strong dissolution and fragmentation and the area where high-quality reservoirs are developed, and local favorable hydrocarbon accumulation segments can be screened. Repeat steps 4 and 5, apply different stresses to the spatial curvature deformation body, different stress fields can be obtained, and then the influence of different stress backgrounds on the spatial characterization of the fault-karst body can be analyzed. From the analysis of the reservoir development of the actual drilled wells, the prediction results are in good agreement with the actual drilling, which conforms to the geological understanding law.

[0081] The above specific implementation manners are only used to illustrate the technical solutions of the present invention rather than to limit them. Although the present invention has been described in detail with reference to the examples, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A stress analysis method based on structural deformation, characterized in that It includes the following steps: S1. Select a profile perpendicular to the strike of the fault dissolution body development zone in the work area where the fault dissolution body develops. Based on the 3D seismic data of the profile, finely interpret the strike-slip fault structure, and analyze the pull-apart, translation, and compressional-shear forms of the strike-slip fault; S2. Combine the structural interpretation information and lithology information, and use the dip scanning technique to obtain the line dip data and trace dip data of the profile; S3. Combine the geological background of the work area and the rock mechanics parameters to calculate the curvature of the formation, and obtain the 3D surface deformation data of the formation; S4. Based on the 3D surface deformation data of the formation, use different bin grids to test the stress parameters of the fault dissolution body, and calculate the tectonic stress field of the formation; S5. Combine the tectonic stress field of the formation to describe the stress properties of different segments inside the fault dissolution body; Step S3 includes: S31. Determine the mechanical parameters of the surrounding rock in the work area according to the geological background of the work area; S32. Use the minimum QR decomposition algorithm to calculate the tectonic curvature of the formation, and obtain the 3D curvature data of the formation; Use the surface fitting minimum QR decomposition algorithm to simulate the tectonic stress field for the line dip and trace dip data, and obtain the curvature volume data; S33. Based on Hooke's law, according to the linear relationship between stress and strain, obtain the 3D surface deformation model of the formation.

2. The stress analysis method based on structural deformation according to claim 1, wherein Step S1 includes: S11. Select a profile perpendicular to the strike of the fault dissolution body development zone in the work area where the fault dissolution body develops, and extract the pre-stack depth migration data of the profile; S12. According to the structural deformation characteristics of different parts, divide the strike-slip fault into superimposed uplift segments, superimposed pull-apart segments, and translation segments, and determine the segmentation of the fault and the overlapping form between adjacent segments.

3. The stress analysis method based on structural deformation according to claim 1, wherein Step S2 includes: S21. Construct a geometric model according to the overlapping part, overlapping form, and geometric parameters; S22. Combine the geometric model with the rock velocity and rock density of the strike-slip fault, and use the dip scanning technique to detect the structural gradient of the pre-stack depth migration data of the profile, and obtain the line dip data and trace dip data of the formation.

4. The stress analysis method based on structural deformation according to claim 1, characterized in that Step S4 includes: S41. Divide bin grids for the 3D surface deformation model; S42. Apply a certain stress σ1 to the 3D surface deformation model; S43. Calculate the 3D tectonic stress field A1 of the formation; S44. Apply certain stresses σ2, σ3, σ4... σ to the three-dimensional surface deformation model respectively n , and correspondingly calculate the three-dimensional tectonic stress fields A2, A3, A4... A of the formation n .

5. The stress analysis method based on structural deformation according to claim 1, wherein Step S5 includes: S51. Extract the stress plane field of the layer to be analyzed from the tectonic stress field to obtain the tensile stress, tensor thickness, and comprehensive characterization map of the ant body of the layer to be analyzed; S52. Qualitatively determine the development area of high-quality reservoirs and favorable hydrocarbon accumulation sections according to the comprehensive characterization map; S53. According to the comprehensive characterization map under different stress backgrounds, analyze the influence of different stress backgrounds on the characterization of the effective reservoir space of the fault dissolution body, and qualitatively determine the segmentation within the same fault and the superimposed pull-apart segments and superimposed compressional uplift segments.

6. The stress analysis method based on structural deformation according to claim 3, wherein The dip scanning technique in step S22 is a scanning method based on the gradient structure tensor.

7. The stress analysis method based on structural deformation according to claim 1, characterized in that The mechanical parameters of the surrounding rock in step S31 include formation velocity, Young's modulus, Poisson's ratio, formation density, and internal friction coefficient.

8. The stress analysis method based on structural deformation according to claim 4, characterized in that The bin grids in step S41 are one of 100 m × 100 m, 300 m × 300 m, and 600 m × 600 m.

9. The stress analysis method based on structural deformation according to claim 8, wherein, The surface element grid is 300 meters × 300 meters.

Images