Rock Fracture Hydraulic Aperture Modeling via 2D Flow Segmentation
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Solution Overview
Problem
Existing methods for estimating fracture permeability in rock fractures are inaccurate and inefficient, leading to misleading predictions in hydrocarbon reservoir modeling due to the heterogeneous nature of rock fractures, which include variable aperture, roughness, and tortuosity.
Innovation Solution
A method and system for calculating the 3D hydraulic aperture of fractures by dividing them into 2D cross-sections oriented parallel to the fluid flow direction, classifying segments as Type I and Type II based on aspect ratio and roughness ratio, and determining hydraulic apertures for each segment to calculate the 3D hydraulic aperture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the cubic law based on parallel-plate concept is used to estimate fracture hydraulic properties, then the calculation is simple, but the accuracy deteriorates due to overestimation caused by heterogeneous fracture characteristics
Solution Approach 1:
The fracture is divided into multiple segments along the flow direction, with each segment characterized by its own hydraulic aperture and geometric properties. This segmentation allows the model to capture the heterogeneous nature of fractures while maintaining computational efficiency through modular calculation of each segment's contribution to overall flow.
Solution Approach 2:
Each fracture segment is assigned local hydraulic properties (aperture, roughness, tortuosity) that reflect its specific characteristics. The model calculates hydraulic aperture and flow properties for each segment individually, then aggregates them to obtain the effective fracture permeability, thereby accounting for spatial variability in fracture geometry.
2Measurement precision
If existing methods are used to improve the accuracy of cubic law, then the measurement precision improves, but the device complexity and computational efficiency deteriorate
Solution Approach 1:
The model transforms the complex 3D fracture geometry problem into a series of 2D cross-sectional analyses by introducing the concept of hydraulic aperture as a key parameter. By calculating the hydraulic aperture for each segment based on its geometric properties and flow direction, the model achieves accurate permeability estimation without requiring full 3D numerical simulation.
Solution Approach 2:
The approach reduces the dimensionality of the problem by analyzing 2D cross-sections of the fracture along the flow direction rather than performing full 3D simulation. This dimensional reduction maintains accuracy by capturing essential flow characteristics while significantly simplifying the computational model.
3Measurement precision
If existing methods are used to improve the accuracy of cubic law, then the measurement precision improves, but the productivity deteriorates due to inefficiency
Solution Approach 1:
By dividing the fracture into discrete segments, the model enables parallel computation of hydraulic properties for each segment. The effective permeability is obtained by aggregating segment contributions, which is computationally more efficient than iterative 3D numerical methods while maintaining accuracy for heterogeneous fracture geometries.
Solution Approach 2:
The model automatically determines the flow direction and segment geometry from the input fracture model, eliminating the need for manual parameter specification. The hydraulic aperture and permeability are calculated directly from the geometric properties of each segment, streamlining the workflow and improving computational efficiency.
Data Source
AI summary
Systems and methods for determining a 3D hydraulic aperture of a 3D fracture are disclosed. The method includes, obtaining a geometry of the 3D fracture, determining a fluid flow direction through the 3D fracture, and dividing the 3D fracture into a plurality of 2D cross-sections oriented substantially parallel to the fluid flow direction. The method further includes dividing each 2D cross-section into a plurality of Type I and Type II fracture segments based on a segment aspect ratio and a segment roughness ratio, determining a 2D segment hydraulic aperture for each of the plurality of Type I and Type II fracture segments, and determining the 3D hydraulic aperture of the 3D fracture based, at least in part, on the 2D segment hydraulic apertures of the plurality of Type I and Type II fracture segments.