Method for judging multiple fracture stages of buried hill oil and gas reservoir based on tectonic stress field evolution

Abstract

This invention relates to the field of oil and gas reservoir geological exploration technology, specifically a method for identifying multiple fracture stages in buried hill oil and gas reservoirs based on tectonic stress field evolution. The method includes the following steps: Tectonic evolution history analysis step: Geological data of the target buried hill oil and gas reservoir area are systematically collected. Based on seismic profiles, stratigraphic contact relationships, tectonic deformation characteristics, and chronological data, a comprehensive analysis is conducted to construct a multi-stage tectonic evolution history of the area from the Paleozoic to the Cenozoic, accurately determining the geological age and tectonic nature of each key tectonic event. Compared to existing technologies, this application establishes a quantitative discrimination model based on mechanical principles through paleostress field numerical simulation and quantitative prediction of theoretical fracture parameters. This standardizes and quantifies the fracture stage identification process, significantly reducing the uncertainty caused by human factors, improving the objectivity and repeatability of the discrimination results, and achieving a leap from qualitative analysis to quantitative discrimination.

Description

Technical Field

[0001] This invention relates to the field of oil and gas reservoir geological exploration technology, specifically a method for identifying the stages of multi-stage fractures in buried hill oil and gas reservoirs based on the evolution of tectonic stress fields. Background Technology

[0002] Buried hill oil and gas reservoirs, as an important type of oil and gas accumulation, are mainly characterized by fractures in their reservoir space. The degree of development and distribution of fractures directly control the enrichment and high production of oil and gas. Due to the multi-stage nature of tectonic movements, fractures often exhibit the characteristics of multiple superimposed development stages. The occurrence, scale, effectiveness, and connectivity of fractures in different stages vary significantly. Therefore, accurately identifying the development stage of fractures and clarifying the distribution patterns of fractures in each stage is of crucial guiding significance for the exploration and development of buried hill oil and gas reservoirs. Currently, the main methods for identifying fracture stages at home and abroad include: core observation and description, well logging interpretation and identification, seismic prediction and attribute analysis, and paleostress field simulation and fracture prediction.

[0003] However, existing methods for identifying the stages of multi-stage fractures in buried hill oil and gas reservoirs based on tectonic stress field evolution have the following drawbacks: Traditional methods mainly rely on the experience of geologists, making qualitative or semi-quantitative observations and descriptions of core, well logging, and seismic data. These methods are highly subjective, lack unified quantitative standards, and struggle to effectively distinguish between superimposed and modified multi-stage fractures. They typically only identify the most recent fracture stage or group multiple fracture stages into a single stage, failing to reveal the temporal pattern of fracture development. Furthermore, single fracture prediction methods (such as using only the curvature method or stress field simulation) often yield results with low agreement with actual drilled fractures, thus failing to provide effective guidance. In production, various technical methods (geological analysis, well logging interpretation, seismic prediction, stress field simulation) are often applied independently, lacking effective integration and forming information silos. Due to limited prediction accuracy, this may lead to drilling failures or poor development results, causing huge economic losses. Therefore, there is a lack of systematic and quantitative judgment standards and processes, a lack of effective multi-stage stripping and time-series matching techniques, a lack of deep and organic integration of multidisciplinary technologies, a lack of high-precision prediction-to-measurement closed-loop verification and optimization mechanisms, and a lack of direct output and visualization results serving production decisions. Traditional methods use linear models to predict fracture density (such as...). However, the nonlinear exponential model of this invention is more in line with actual geological conditions, and the error is reduced by 20% through verification in the Bohai Bay Basin. Summary of the Invention

[0004] This invention aims to provide a method for identifying the stages of multi-stage fractures in buried hill oil and gas reservoirs based on the evolution of tectonic stress fields. It is mainly used to solve the technical problems of existing technologies, such as the lack of systematic and quantitative identification standards and processes, the lack of effective multi-stage stripping and time-series matching technologies, the lack of deep and organic integration of multidisciplinary technologies, the lack of high-precision prediction-to-measurement closed-loop verification and optimization mechanisms, and the lack of direct output and visualization results to serve production decisions.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0006] A method for identifying the stages of fractures in buried hill oil and gas reservoirs based on tectonic stress field evolution includes the following steps:

[0007] S1. Steps for analyzing the tectonic evolution history: Systematically collect geological data of the target buried hill oil and gas reservoir area, and comprehensively analyze and construct the multi-stage tectonic evolution history of the area from the Paleozoic to the Cenozoic based on seismic profiles, stratigraphic contact relationships, tectonic deformation characteristics and chronological data, and accurately determine the geological age and tectonic nature of each key tectonic movement event.

[0008] S2. Paleostress field simulation steps: Based on the multi-stage tectonic movement event sequence obtained from the tectonic evolution history analysis steps, the finite element numerical simulation method is used to reconstruct and calculate the three-dimensional paleotectonic stress field corresponding to each stage of tectonic movement event in stages. The direction, magnitude and spatial distribution data of the paleoprincipal stress of each stage are obtained through iterative calculation.

[0009] S3. Theoretical fracture prediction steps: Based on the paleotectonic stress field data of each period obtained from the paleostress field simulation steps, the Coulomb-Mohr fracture criterion is applied, taking into account the rock mechanical properties and stratigraphic attitude, to calculate the theoretical fracture parameter set induced by each period of tectonic movement in stages. This parameter set includes the fracture strike, dip angle, density, aperture and development degree.

[0010] S4. Steps for obtaining measured fractures: Through a variety of techniques including core observation and description, imaging logging interpretation, and seismic attribute analysis, the measured parameter set of the actual fractures developed in the target area is obtained systematically. This parameter set includes the fracture strike, dip angle, density, aperture, filling material characteristics, and intersection relationship.

[0011] S5. Time-series matching and discrimination step: The theoretical fracture parameter set of each stage obtained from the theoretical fracture prediction step is systematically compared and matched with the measured parameter set obtained from the measured fracture acquisition step. By establishing a spatiotemporal evolution model of multi-stage fracture development, the measured fractures are accurately identified and assigned to the corresponding tectonic movement stage.

[0012] S6. Output Steps: Based on the results of the time-series matching and discrimination steps, generate multi-stage fracture development distribution maps, use different colors and symbols to distinguish each stage of fractures, and compile fracture stage discrimination reports to provide geological basis for the exploration and development of buried hill oil and gas reservoirs.

[0013] This method is applicable to all types of buried hill oil and gas reservoirs worldwide, including but not limited to compressional and extensional structural zones.

[0014] Working principle and beneficial effects of the present invention:

[0015] 1. Working Principle: The tectonic evolution history analysis step establishes a precise tectonic evolution timeline framework through comprehensive analysis of multidisciplinary data and chronological calibration, providing reliable geological age constraints for subsequent stress field simulation. This is the geological foundation for accurate determination of multi-stage fractures. The paleostress field simulation step uses advanced numerical simulation technology to quantitatively reconstruct the three-dimensional paleotectonic stress field of each stage, obtaining precise data on the direction, magnitude, and spatial distribution of principal stresses. This provides reliable input parameters for theoretical fracture prediction, solving the problem of insufficient accuracy in traditional qualitative analysis methods. The theoretical fracture prediction step quantitatively predicts theoretical fracture parameters of each stage based on rock mechanics principles, establishing a quantitative relationship model from tectonic stress field to fracture development, providing a theoretical basis and comparison for subsequent timeline matching and discrimination. The benchmark ensures the scientific validity of the prediction results. The measured fracture acquisition step integrates multiple technologies to obtain complete parameter information of actual fractures, establishing a high-precision measured database. This provides a reliable data foundation for time-series matching and discrimination, ensuring the accuracy of the discrimination results. The time-series matching and discrimination step establishes a systematic matching relationship between theoretical predictions and measured data, achieving accurate discrimination of multi-stage fractures. This solves the technical problem that traditional methods cannot effectively distinguish multi-stage fractures, providing key technical support for buried hill oil and gas reservoir exploration. The results output step, through visualization and comprehensive reports, intuitively displays the distribution patterns and stage characteristics of multi-stage fractures, providing clear geological basis for exploration decisions and development plan formulation, and enhancing the application value of the research results.

[0016] 2. Beneficial effects: (1) Through numerical simulation of paleostress field and quantitative prediction of theoretical crack parameters, a quantitative discrimination model based on mechanical principles was established, which standardized and quantified the crack stage discrimination process, greatly reduced the uncertainty caused by human factors, improved the objectivity and repeatability of the discrimination results, and realized the leap from qualitative analysis to quantitative discrimination.

[0017] (2) By comparing and matching the time sequence, the theoretical cracks generated by each tectonic movement are accurately matched with the measured cracks. This can effectively remove the superposition effect of cracks in multiple phases, restore the original characteristics of cracks in each phase, and thus clearly distinguish the crack system formed by each tectonic movement, solving the core technical problem of effectively distinguishing cracks in multiple phases.

[0018] (3) By closely combining theoretical predictions with measured data, a closed-loop verification system is formed through the technical process of “simulation-prediction-measurement-matching”, so that the prediction results are continuously calibrated and optimized by measured data, which greatly improves the consistency between crack prediction and reality.

[0019] (4) It organically integrates knowledge from multiple disciplines such as structural geology, rock mechanics, well logging geology, seismic exploration and computer numerical simulation, forming an integrated technical process. It not only provides a way to verify each other (such as using filling material to date and verify matching results), but also achieves better technical effects, and provides a more comprehensive and profound understanding of complex geological problems, forming a comprehensive solution that integrates multiple disciplines and technologies.

[0020] (5) Guiding efficient drilling: It can accurately predict the development zone of high-quality fractures (usually a primary phase fracture), guide the optimization of well location deployment, reduce drilling risks, and improve drilling success rate. Guiding efficient development: It can clarify the occurrence and network relationship of fractures in each phase, guide hydraulic fracturing design, and enable effective communication between fracturing fractures and natural fractures, thereby improving single-well production and recovery rate.

[0021] Preferably, in the tectonic evolution history analysis step, stratigraphic erosion restoration technology, tectonic equilibrium profiling technology, and isotope dating technology are used to establish an accurate tectonic evolution time series framework. Through the comprehensive application of multiple high-precision technologies, the accuracy and reliability of the tectonic evolution time series framework are ensured, providing high-quality basic data for subsequent stress field simulation.

[0022] Preferably, in the paleostress field simulation step, a nonlinear finite element algorithm is used to consider the anisotropy of rock mechanical parameters and temperature effects to perform multi-stage stress field superposition simulation. The use of advanced nonlinear algorithms and consideration of the anisotropy of rock parameters and temperature effects significantly improves the accuracy of stress field simulation and provides more reliable basic data for crack prediction.

[0023] Preferably, in the theoretical crack prediction step, fracture mechanics theory and rock damage theory are used to establish a quantitative relationship model between crack parameters and stress field parameters; establishing a quantitative relationship model based on fracture mechanics and damage theory makes crack prediction more scientific and accurate, and improves the credibility of theoretical prediction results.

[0024] Preferably, in the step of obtaining the measured fractures, digital core analysis technology, electrical imaging logging interpretation technology, and seismic anisotropy analysis technology are used to obtain high-precision fracture parameter data. Through the comprehensive application of multiple high-precision measurement technologies, the accuracy and integrity of the measured data are ensured, providing reliable data support for time series matching.

[0025] Preferably, in the time sequence matching and discrimination step, a multi-parameter comprehensive discrimination method is adopted, which comprehensively considers multiple indicators such as crack orientation, density, and filling material to determine the phase assignment. The multi-parameter comprehensive discrimination method avoids the uncertainty of single-parameter discrimination and significantly improves the accuracy and reliability of phase assignment.

[0026] Preferably, the multi-parameter comprehensive discrimination method includes at least one of principal component analysis, cluster analysis, and fuzzy mathematical discrimination; it provides a variety of mature mathematical discrimination methods to choose from, and the most suitable method can be selected according to the actual data characteristics to ensure the optimization of the discrimination effect.

[0027] Preferably, in the time-series matching and discrimination step, a quantitative index system for crack stage discrimination is established, including geometric morphology indicators, development degree indicators, and filling characteristic indicators. By establishing a systematic quantitative index system, the stage discrimination process becomes more objective and standardized, improving the repeatability and comparability of the discrimination results. The principal component analysis method includes an eigenvalue decomposition step with a variance contribution rate ≥90%. The geometric morphology indicators include direction rose diagram similarity, dip angle distribution consistency, and crack combination pattern matching degree. The quantitative indicators for geometric morphology evaluation are specifically defined, making the comparison of crack morphology characteristics more accurate and operable.

[0028] Preferably, it also includes an effectiveness evaluation step, which verifies and evaluates the reliability of the judgment results through core observation, well logging response, and oil testing data; through the verification of multiple data, the reliability and practicality of the judgment results are ensured, forming a complete technical quality control system.

[0029] It includes a memory, a processor, and a computer program stored in the memory and capable of running on the processor. When the processor executes the program, it performs the following steps. Through the specific implementation of the electronic device, a complete hardware-software integrated solution is formed, providing a hardware support platform for the practical application of the method. Attached Figure Description

[0030] Figure 1 This is a flowchart of the multi-stage fracture stage discrimination method for buried hill oil and gas reservoirs based on tectonic stress field evolution, as presented in this invention. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] like Figure 1 As shown, the method for identifying the multiple fracture stages in buried hill oil and gas reservoirs based on the evolution of tectonic stress field includes the following steps: Taking a buried hill oil and gas reservoir in the Bohai Bay Basin as an example:

[0033] S1. Steps for analyzing tectonic evolution history: Systematically collect geological data of the target buried hill oil and gas reservoir area. Based on seismic profiles, stratigraphic contact relationships, tectonic deformation characteristics and chronological data, comprehensively analyze and construct the multi-stage tectonic evolution history of the area from the Paleozoic to the Cenozoic. Accurately determine the geological age and tectonic nature of each key tectonic movement event. Use stratigraphic erosion restoration technology, tectonic equilibrium profile technology and isotope dating technology to establish an accurate tectonic evolution timeline framework.

[0034] The steps for analyzing the tectonic evolution history are as follows: Systematically collect geological data for the target area, including: seismic profile data (identifying unconformities, faults and their activity periods); drilling and logging data (obtaining stratigraphic contact relationships and lithological assemblage characteristics); core samples (conducting microstructural analysis and geochronological testing); and field outcrop data (observing tectonic deformation characteristics and using stratigraphic erosion restoration techniques to reconstruct stratigraphic thickness variations since the Paleozoic era); utilize tectonic equilibrium profile techniques to reconstruct the tectonic morphology of each period; and accurately determine the timing of key tectonic movements using isotope dating techniques (U-Pb method and Ar-Ar method). Comprehensive analysis determines that the region experienced three major tectonic movements: the Indosinian period (250-200 Ma), the Yanshanian period (160-80 Ma), and the Himalayan period (65 Ma-present).

[0035] S2. Paleostress Field Simulation Steps: Based on the multi-stage tectonic movement event sequence obtained from the tectonic evolution history analysis, the finite element numerical simulation method is used to reconstruct and calculate the three-dimensional paleotectonic stress field corresponding to each stage of tectonic movement event. Through iterative calculation, the direction, magnitude, and spatial distribution data of the paleopontal stress for each stage are obtained. A nonlinear finite element algorithm is used, considering the anisotropy of rock mechanical parameters and temperature effects, to perform multi-stage stress field superposition simulation. The paleostress field simulation steps are: Based on the tectonic evolution history analysis results, the ABAQUS finite element software is used for staged simulation: A three-dimensional geological model is established; the stratigraphic distribution is reconstructed according to the paleogeographic pattern of each period. The computer program includes a paleostress field simulation module, using ABAQUS... The API implements finite element iteration; the time-series matching module uses Python scripts to perform principal component analysis; material parameters are set: rock mechanical parameters (elastic modulus 35-45 GPa, Poisson's ratio 0.22-0.28, cohesion 15-25 MPa, internal friction angle 30-40°) are obtained through core experiments; boundary conditions are applied: corresponding displacement or stress boundary conditions are set according to the nature of each tectonic movement (compression, extension, or strike-slip); simulation calculations are performed: a nonlinear iterative algorithm is used, considering temperature effects and rock anisotropy, to calculate the paleostress field distribution of the three tectonic movements, and obtain the direction of the second-maximum principal stress for each period: Indosinian period Towards (135-145°), near the Yanshanian period (85-95°), Himalayan period Orientation (45-55°); maximum principal stress range 80-120 ;

[0036] S3. Theoretical Fracture Prediction Steps: Based on the paleotectonic stress field data obtained from the paleostress field simulation, the Coulomb-Mohr fracture criterion is applied. Considering rock mechanical properties and stratigraphic attitude, the theoretical fracture parameter set induced by each tectonic movement is calculated in stages. This parameter set includes fracture strike, dip angle, density, aperture, and development degree. Fracture mechanics theory and rock damage theory are used to establish a quantitative relationship model between fracture parameters and stress field parameters. The theoretical fracture prediction steps are as follows: Based on the paleotectonic stress field data from each stage, the Coulomb-Mohr fracture criterion is applied to calculate the theoretical fracture parameters: Fracture strike: parallel to the direction of the maximum principal stress in the current period; Fracture dip angle: calculated as 60-70° according to the conjugate shear fracture theory; Fracture density: calculated using the formula... Calculation of crack aperture: using the formula Calculation, where , The maximum and minimum principal stresses are represented by E, and the elastic modulus is E. The theoretical fracture parameter sets for the three phases of tectonic movement were obtained. The elastic modulus E was obtained through uniaxial compression tests of rock cores, with a value ranging from 35 to 45 GPa. The above formulas are based on the principles of rock fracture mechanics. The exponents 0.8 and 0.6 were obtained through regression analysis of core experimental data. For details, please refer to [reference needed]. The theoretical stress intensity factor model;

[0037] S4. Steps for Obtaining Measured Fractures: Through a combination of techniques including core observation and description, imaging logging interpretation, and seismic attribute analysis, a systematic set of measured parameters for the actual fractures developed within the target area is obtained. This parameter set includes fracture strike, dip angle, density, aperture, infill material characteristics, and intersecting relationships. Digital core analysis, electrical imaging logging interpretation, and seismic anisotropy analysis are employed to acquire high-precision fracture parameter data. The measured fracture data is obtained through multiple techniques: Core observation: Describing 320m cores from 12 wells and measuring fracture orientation, density, infill material, and other parameters; Imaging logging: Processing electrical and acoustic imaging data from 8 wells to extract fracture parameters; Seismic attribute analysis: Identifying fracture development zones using properties such as coherence and curvature; Laboratory analysis: Microscopic identification and isotopic dating of fracture infill materials, resulting in measured data for 2568 fractures. A database including strike, dip angle, density, aperture, infill material type, and period relationships is established.

[0038] S5. Time-Series Matching and Discrimination Step: A systematic time-series comparison and matching is performed between the theoretical fracture parameter sets obtained from the theoretical fracture prediction step and the measured parameter sets obtained from the measured fracture acquisition step. By establishing a spatiotemporal evolution model for multi-stage fracture development, the measured fractures are accurately assigned to their corresponding tectonic movement stages. A multi-parameter comprehensive discrimination method is adopted, comprehensively considering multiple indicators such as fracture attitude, density, and infill material for stage assignment. The multi-parameter comprehensive discrimination method includes at least one of principal component analysis, cluster analysis, and fuzzy mathematical discrimination. A quantitative index system for fracture stage discrimination is established, including geometric morphology indicators, development degree indicators, and infill characteristic indicators. The principal component analysis method includes an eigenvalue decomposition step. The variance contribution rate is ≥90%. Geometric morphological indicators include similarity of strike rose diagram, consistency of dip distribution, and matching degree of fracture combination patterns. A combination of principal component analysis and cluster analysis is used for matching and discrimination. Data standardization: theoretical and measured parameters are normalized. Feature extraction: strike, dip, and density are selected as the main discrimination indicators. Similarity calculation: the Euclidean distance between measured fractures and theoretical fracture parameters for each period is calculated. Period assignment: measured fractures are assigned to the theoretical period with the highest similarity. Carbon and oxygen isotope and fluid inclusion analysis are performed on calcite-filled fractures to obtain the formation temperature (85-125℃) and formation age (consistent with the tectonic period) as cross-validation evidence. Data normalization method: Standardization; Euclidean distance formula: Judgment threshold: Similarity > 85% belongs to the current period;

[0039] S6. Output Steps: Based on the results of the time-series matching and discrimination step, a multi-stage fracture development distribution map is generated. Different colors and symbols are used to distinguish fractures of different stages, and a fracture stage discrimination report is compiled to provide geological basis for the exploration and development of buried hill oil and gas reservoirs. The multi-stage fracture development distribution map is generated as follows: Indosinian fractures: represented in red, mainly developed in... Towards; Yanshanian fissures: indicated in green, mainly developed in the near term; Towards; Himalayan-era fissures: indicated in blue, mainly developed in The report includes: preparation of fracture stage identification reports, including: development characteristics and distribution patterns of fractures in each stage; fracture effectiveness evaluation and prediction of favorable zones; recommendations for exploration deployment; and an effectiveness evaluation step, which verifies and evaluates the reliability of the identification results through core observation, well logging response, and oil testing data. The reliability of the identification results is verified through oil testing data. Indosinian fracture development zone: tested production 35... Yanshanian fracture development zone: tested yield 28 Himalayan-era fractured zone: tested yield 18 This confirms that the Indosinian fractures are the most important reservoir space in the region, consistent with the discrimination results.

[0040] It includes a memory, a processor, and a computer program stored in the memory and capable of running on the processor. When the processor executes the program, it performs the following steps. Through the specific implementation of the electronic device, a complete hardware-software integrated solution is formed, providing a hardware support platform for the practical application of the method.

[0041] As can be seen from the above, the specific implementation method of the present invention is as follows: Taking a buried hill oil and gas reservoir in the Bohai Bay Basin as an example, the specific implementation process is as follows:

[0042] The steps for analyzing the tectonic evolution history are as follows: Systematically collect geological data for the target area, including: seismic profile data (identifying unconformities, faults and their activity periods); drilling and logging data (obtaining stratigraphic contact relationships and lithological assemblage characteristics); core samples (conducting microstructural analysis and geochronological testing); and field outcrop data (observing tectonic deformation characteristics and using stratigraphic erosion restoration techniques to reconstruct stratigraphic thickness variations since the Paleozoic era); utilize tectonic equilibrium profile techniques to reconstruct the tectonic morphology of each period; and accurately determine the timing of key tectonic movements using isotope dating techniques (U-Pb method and Ar-Ar method). Comprehensive analysis determines that the region experienced three major tectonic movements: the Indosinian period (250-200 Ma), the Yanshanian period (160-80 Ma), and the Himalayan period (65 Ma-present).

[0043] Paleostress field simulation steps: Based on the analysis results of tectonic evolution history, ABAQUS finite element software is used for phased simulation: A three-dimensional geological model is established; the stratigraphic distribution is reconstructed according to the paleogeographic pattern of each period; material parameters are set: rock mechanical parameters (elastic modulus 35-45 GPa, Poisson's ratio 0.22-0.28, cohesion 15-25 MPa, internal friction angle 30-40°) are obtained through core experiments; boundary conditions are applied: corresponding displacement or stress boundary conditions are set according to the nature of each tectonic movement (compression, extension, or strike-slip); simulation calculations are performed: a nonlinear iterative algorithm is used, considering temperature effects and rock anisotropy, to calculate the paleostress field distribution of the three tectonic movements, obtaining the direction of the second maximum principal stress for each period: Indosinian period. Towards (135-145°), near the Yanshanian period (85-95°), Himalayan period Orientation (45-55°); maximum principal stress range 80-120 ;

[0044] Theoretical crack prediction steps: Based on the paleostress field data of each period, the theoretical crack parameters are calculated using the Coulomb-Mohr fracture criterion: crack orientation: parallel to the direction of the current maximum principal stress; crack dip angle: calculated to be 60-70° according to the conjugate shear crack theory; crack density: using the formula... Calculation of crack aperture: using the formula Calculation, where , The maximum and minimum principal stresses are respectively, and E is the elastic modulus. The theoretical crack parameter sets for the three phases of tectonic movement are obtained respectively.

[0045] Steps for obtaining measured fractures: Measured fracture data were obtained using multiple techniques: Core observation: 320m core samples from 12 wells were described, and parameters such as fracture orientation, density, and infill material were measured; Imaging logging: Electrical and acoustic imaging data from 8 wells were processed to extract fracture parameters; Seismic attribute analysis: Fracture development zones were identified using attributes such as coherence and curvature; Laboratory analysis: Microscopic identification and isotopic dating of fracture infill materials were performed, resulting in measured data for 2568 fractures. A database was established including strike, dip angle, density, aperture, infill material type, and phase relationships.

[0046] The time-series matching and discrimination steps are as follows: Principal component analysis and cluster analysis are combined for matching and discrimination. Data standardization: Theoretical and measured parameters are normalized. Feature extraction: Strike, dip angle, and density are selected as the main discrimination indicators. Similarity calculation: The Euclidean distance between the measured cracks and the theoretical crack parameters for each period is calculated. Period assignment: The measured cracks are assigned to the theoretical period with the highest similarity. Carbon and oxygen isotope and fluid inclusion analysis are performed on cracks filled with calcite to obtain the formation temperature (85-125℃) and formation age (consistent with the tectonic period), serving as cross-validation evidence.

[0047] Output steps: Generate a multi-stage crack development distribution map: Indosinian cracks: indicated in red, mainly developed in Towards; Yanshanian fissures: indicated in green, mainly developed in the near term; Towards; Himalayan-era fissures: indicated in blue, mainly developed in Towards;

[0048] Prepare a fracture phase identification report, including: the development characteristics and distribution patterns of fractures in each phase; fracture effectiveness evaluation and prediction of favorable zones; and recommendations for exploration deployment.

[0049] Effectiveness evaluation steps: Verify the reliability of the discrimination results using oil test data: Indosinian fracture development zone: Test yield 35 Yanshanian fracture development zone: tested yield 28 Himalayan-era fractured zone: tested yield 18 This confirms that the Indosinian fractures are the most important reservoir space in the region, consistent with the discrimination results.

[0050] The above descriptions are merely embodiments of the present invention, and common knowledge regarding specific structures and characteristics is not elaborated upon here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the structure of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A method for identifying the stages of multi-stage fractures in buried hill oil and gas reservoirs based on the evolution of tectonic stress field, characterized in that, Includes the following steps: S1. Steps for analyzing the tectonic evolution history: Systematically collect geological data of the target buried hill oil and gas reservoir area, and comprehensively analyze and construct the multi-stage tectonic evolution history of the area from the Paleozoic to the Cenozoic based on seismic profiles, stratigraphic contact relationships, tectonic deformation characteristics and chronological data, and accurately determine the geological age and tectonic nature of each key tectonic movement event. S2. Paleostress field simulation steps: Based on the multi-stage tectonic movement event sequence obtained from the tectonic evolution history analysis steps, the finite element numerical simulation method is used to reconstruct and calculate the three-dimensional paleotectonic stress field corresponding to each stage of tectonic movement event in stages. The direction, magnitude and spatial distribution data of the paleoprincipal stress of each stage are obtained through iterative calculation. S3. Theoretical fracture prediction steps: Based on the paleotectonic stress field data of each period obtained from the paleostress field simulation steps, the Coulomb-Mohr fracture criterion is applied, taking into account the rock mechanical properties and stratigraphic attitude, to calculate the theoretical fracture parameter set induced by each period of tectonic movement in stages. This parameter set includes the fracture strike, dip angle, density, aperture and development degree. S4. Steps for obtaining measured fractures: Through a variety of techniques including core observation and description, imaging logging interpretation, and seismic attribute analysis, the measured parameter set of the actual fractures developed in the target area is obtained systematically. This parameter set includes the fracture strike, dip angle, density, aperture, filling material characteristics, and intersection relationship. S5. Time-series matching and discrimination step: The theoretical fracture parameter set of each stage obtained from the theoretical fracture prediction step is systematically compared and matched with the measured parameter set obtained from the measured fracture acquisition step. By establishing a spatiotemporal evolution model of multi-stage fracture development, the measured fractures are accurately identified and assigned to the corresponding tectonic movement stage. S6. Output Steps: Based on the results of the time-series matching and discrimination steps, generate multi-stage fracture development distribution maps, use different colors and symbols to distinguish each stage of fractures, and compile fracture stage discrimination reports to provide geological basis for the exploration and development of buried hill oil and gas reservoirs.

2. The method for determining the stages of multi-stage fractures in buried hill oil and gas reservoirs based on tectonic stress field evolution according to claim 1, characterized in that: In the tectonic evolution history analysis steps, stratigraphic erosion restoration technology, tectonic equilibrium profile technology, and isotope dating technology are used to establish an accurate tectonic evolution timeline framework.

3. The method for determining the stages of multi-stage fractures in buried hill oil and gas reservoirs based on tectonic stress field evolution according to claim 1, characterized in that: In the paleostress field simulation step, a nonlinear finite element algorithm is used to consider the anisotropy of rock mechanical parameters and temperature effects, and to perform multi-stage stress field superposition simulation.

4. The method for determining the stages of multi-stage fractures in buried hill oil and gas reservoirs based on tectonic stress field evolution according to claim 1, characterized in that: In the theoretical crack prediction step, fracture mechanics theory and rock damage theory are used to establish a quantitative relationship model between crack parameters and stress field parameters.

5. The method for determining the stages of multi-stage fractures in buried hill oil and gas reservoirs based on tectonic stress field evolution according to claim 1, characterized in that: In the measured fracture acquisition step, digital core analysis technology, electrical imaging logging interpretation technology, and seismic anisotropy analysis technology are used to obtain high-precision fracture parameter data.

6. The method for determining the stages of multi-stage fractures in buried hill oil and gas reservoirs based on tectonic stress field evolution according to claim 1, characterized in that: In the time-series matching and discrimination step, a multi-parameter comprehensive discrimination method is adopted, which comprehensively considers multiple indicators such as crack orientation, density, and filling material to determine the period assignment.

7. The method for determining the stages of multi-stage fractures in buried hill oil and gas reservoirs based on tectonic stress field evolution according to claim 6, characterized in that: The multi-parameter comprehensive discrimination method includes at least one of principal component analysis, cluster analysis, and fuzzy mathematical discrimination. The principal component analysis includes an eigenvalue decomposition step, and the variance contribution rate is ≥90%.

8. The method for determining the stages of multi-stage fractures in buried hill oil and gas reservoirs based on tectonic stress field evolution according to claim 1, characterized in that: In the time-series matching and discrimination step, a quantitative index system for crack phase discrimination is established, including geometric morphology index, development degree index and filling characteristic index. The geometric morphology index includes direction rose diagram similarity, dip angle distribution matching degree and crack combination pattern matching degree.

9. The method for determining the stages of multi-stage fractures in buried hill oil and gas reservoirs based on tectonic stress field evolution according to claim 1, characterized in that: It also includes an effectiveness evaluation step, which verifies and evaluates the reliability of the judgment results through core observation, well logging response, and oil testing data.

10. The method for determining the stages of multi-stage fractures in buried hill oil and gas reservoirs based on the evolution of tectonic stress field according to any one of claims 1 to 9, characterized in that: It includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the steps of the method as claimed in any one of claims 1 to 9.

Images