Unstructured Grid Fracture Simulation with Embedded Discrete Modeling
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Solution Overview
Problem
Conventional methods for simulating subterranean regions with complex fracture geometries, such as dual-porosity or dual-permeability models and unstructured grids, are inadequate for accurately modeling large-scale fractures and are computationally expensive, limiting their ability to handle complex fracture geometries effectively.
Innovation Solution
A method and system that utilize non-intrusive embedded discrete fracture modeling combined with element-based finite-volume formulations to create a computational grid that incorporates 2D or 3D geometric elements, allowing for the accurate simulation of subterranean regions with complex fracture geometries by dividing fractures into segments and calculating transmissibility factors, which are then used to simulate fluid flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional dual-porosity or dual-permeability models are used to simulate fractured reservoirs, then small-scale fractures with high density can be modeled, but large-scale fractures like those created during hydraulic fracturing operations cannot be handled explicitly
Solution Approach 1:
The patent segments the fracture network into discrete fracture segments that are explicitly represented within the grid blocks. Each fracture is divided into segments based on the grid block boundaries it intersects, allowing both small-scale and large-scale fractures to be modeled explicitly rather than through averaged dual-continuum parameters.
2Shape
If conventional unstructured gridding methods are used to represent irregular reservoir structures, then flexibility in geometry representation is improved, but computational cost increases exponentially with the number and complexity of fractures
Solution Approach 1:
The patent embeds the discrete fracture segments directly within the existing grid block structure, nesting the fracture geometry representation inside the grid framework. This allows irregular reservoir structures to be represented using unstructured grids while avoiding the need to generate excessively complex gridding around each fracture, thus maintaining computational efficiency.
Solution Approach 2:
The patent applies different levels of geometric detail locally - using 2D geometric elements for 2D grids and 3D geometric elements for 3D grids only where fractures are present. This local refinement approach maintains accuracy in fracture representation while avoiding the computational overhead of fully 3D gridding throughout the entire reservoir model.
3Adaptability or versatility
If conventional unstructured gridding is used for reservoir simulation, then vertical fractures can be modeled, but complex fracture geometries with varying orientations and intersections cannot be efficiently simulated
Solution Approach 1:
The patent transitions from conventional 2D grid-based approaches to supporting both 2D and 3D geometric elements within the same computational framework. This allows fractures with any orientation (vertical, horizontal, inclined, intersecting) to be represented explicitly by choosing the appropriate dimensional element type, without increasing overall system complexity.
Data Source
AI summary
Systems and methods for simulating subterranean regions having fracture geometries. Non-intrusive embedded discrete fracture modeling formulations are applied to two-dimensional and three-dimensional unstructured grids, with mixed elements, using an element-based finite-volume method in conjunction with commercial simulators to model subsurface characteristics in regions having complex hydraulic fractures, complex natural fractures, or a combination of both.