Transient Flow Simulation in Complex Subsurface Fracture Geometries
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Solution Overview
Problem
Current methods for simulating fluid flow in subterranean formations with complex fracture geometries, such as those created during hydraulic fracturing, are limited by their inability to accurately model non-orthogonal and nonplanar fractures, leading to inefficiencies and inaccuracies in reservoir analysis and production optimization.
Innovation Solution
A method and system that refine gridblocks near fractures, calculate intersections between gridblocks and fractures, and generate simulations using embedded discrete fracture modeling (EDFM) formulations, allowing for the accurate representation of complex fracture geometries and improved transient flow modeling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional dual-porosity or dual-permeability models are used to simulate fluid flow in fractured reservoirs, then small-scale fractures with high density can be modeled, but large-scale fractures created during hydraulic fracturing operations cannot be handled and complex fracture geometries cannot be dealt with explicitly
Solution Approach 1:
The reservoir is divided into two distinct systems: a fracture system representing large-scale fractures created during hydraulic fracturing, and a matrix system representing the rock matrix. This segmentation allows the model to explicitly handle complex fracture geometries while maintaining the ability to model fluid flow interactions between fractures and matrix, resolving the contradiction between handling different fracture scales and maintaining modeling accuracy.
Solution Approach 2:
The patent transitions from conventional two-dimensional dual-porosity models to a three-dimensional explicit fracture network model. By representing fractures as three-dimensional discrete structures with varying geometries (planar, non-planar, orthogonal, non-orthogonal), the model can accurately capture complex fracture geometries and their impact on fluid flow, thereby improving both adaptability and reliability simultaneously.
2Adaptability or versatility
If unstructured gridding is used to handle complex fracture geometries, then fracture representation capability is improved, but computational cost increases significantly and the methods are limited to vertical fractures only
Solution Approach 1:
Instead of using complex unstructured gridding throughout the entire reservoir model, the patent applies a simplified structured grid approach with localized fracture representations. The fracture network is explicitly modeled using discrete fracture objects that can be superimposed on a regular grid, maintaining computational efficiency while enabling accurate representation of complex fracture geometries including non-orthogonal and non-planar fractures.
Solution Approach 2:
The patent introduces an intermediary representation method where fractures are modeled as discrete geometric objects with defined properties (aperture, conductivity, geometry) that can be independently defined and interpolated onto the grid. This intermediary approach allows complex fracture geometries to be represented without requiring complex gridding algorithms, thereby maintaining computational efficiency while improving fracture representation capability.
3Ease of manufacture
If corner point grids are used to represent reservoir geometry, then flexible definition of block geometries is achieved, but it is difficult and unrealistic to explicitly grid all fractures in such a manner
Solution Approach 1:
The patent segments the fracture representation from the grid structure. Corner point grids are used to define the reservoir geometry and matrix blocks, while fractures are represented as discrete objects that can be independently positioned and configured. This segmentation allows the corner point grid to maintain its flexibility in defining complex reservoir geometries while avoiding the complexity of attempting to explicitly grid all fractures within the grid structure.
Solution Approach 2:
Instead of attempting to fit fractures within the grid structure (the conventional approach), the patent inverts the approach by allowing fractures to define the grid structure. Fractures are modeled as discrete objects that can be superimposed on the grid, and the grid is adjusted to accommodate the fracture network. This inversion simplifies the overall model complexity while maintaining the ability to represent complex fracture geometries accurately.
Data Source
AI summary
Systems and methods for simulating subterranean regions having multi-scale fracture geometries. Non-intrusive embedded discrete fracture modeling formulations are applied in conjunction with commercial simulators to efficiently and accurately model subsurface transient flow characteristics in regions having complex hydraulic fractures, complex natural fractures, or a combination of both, and geometries including corner point grids.