Stress Inversion via Boundary Element Method
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Solution Overview
Problem
Current tectonic stress mapping methods struggle to accurately model complex fault networks and account for variations in stress fields caused by active faulting and paleostress in geologic environments, particularly in structurally complex reservoirs, leading to uncertainties in seismic interpretation and drilling operations.
Innovation Solution
A method utilizing a geomechanical framework that incorporates the boundary element method (BEM) for modeling three-dimensional stress fields, including characterization and modeling of subseismic fractures, and multi-dimensional fault modeling to create accurate representations of present-day heterogeneous stress fields, facilitated by software frameworks like PETREL and iBem3D, which integrates data from seismic, logging, and geophysical data to simulate geologic environments and optimize drilling decisions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional tectonic stress mapping methods are used, then the modeling process is simpler, but the accuracy of stress field representation deteriorates in complex reservoirs
Solution Approach 1:
The patent segments the continuous stress field into discrete elements using the boundary element method. The geological formation is divided into boundary elements that can individually represent different stress conditions, allowing complex stress fields to be modeled through composition of simpler elemental responses. This segmentation enables accurate representation of heterogeneous stress fields while maintaining computational tractability.
Solution Approach 2:
The patent transitions from traditional two-dimensional stress mapping to three-dimensional stress field modeling. By incorporating the third dimension (depth and vertical stress components), the model can represent complex reservoir geometries and stress variations more accurately. The boundary element method naturally extends to 3D, allowing representation of volumetric stress states and complex fault geometries that cannot be captured in 2D.
2Reliability
If detailed fault network modeling is implemented, then the geological model accuracy improves, but the computational resources and time required increase
Solution Approach 1:
The patent uses boundary elements as simplified representations (copies) of complex geological features. Instead of modeling every detail of fault networks with full geometric complexity, the method creates boundary element copies that capture the essential stress-field-affecting characteristics of faults and fractures. This copying approach maintains model accuracy while significantly reducing computational complexity compared to full detailed modeling.
Solution Approach 2:
The patent changes the parameter representation from detailed geometric descriptions of fault networks to stress field parameters derived from boundary element solutions. By transforming the problem from modeling fault geometry in detail to computing stress parameters from boundary elements, the method achieves accurate stress field representation with reduced computational burden. Key parameters such as principal stress directions and magnitudes are computed directly from the boundary element model.
3Measurement precision
If subseismic fractures are characterized and modeled, then the fracture distribution accuracy improves, but the data processing complexity increases
Solution Approach 1:
The patent introduces boundary elements as an intermediary representation between raw fracture data and the final stress field model. Subseismic fractures, which are too small to be directly observed, are represented through boundary elements that infer their presence and orientation from seismic data and geological knowledge. This intermediary approach allows characterization of subseismic fracture networks without requiring direct observation of each fracture, thereby improving fracture distribution accuracy while managing data processing complexity.
Data Source
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AI summary
A method (710) can include receiving data for fractures associated with a geologic environment (712); performing stress inversion, based at least in part on a portion of the data and assignment of different mechanical fracture types to different populations of the fractures, to recover tectonic stress (716); and outputting the tectonic stress (720).