3D Hybrid Grid Generation for Reservoir Simulation
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Solution Overview
Problem
Current hybrid grid generation methods for simulating fluid flows in heterogeneous reservoirs with geometric discontinuities, such as wells and fractures, fail to create a transition grid with intermediate cell sizes between well and reservoir grids, limiting the accuracy and realism of 3D simulations.
Innovation Solution
A method that automatically generates a 3D hybrid grid by defining a minimum cavity size and constructing a transition grid with constraints like conformity, convexity, and orthogonality, using algorithms like Delaunay triangulation and power diagrams to ensure self-centering and orthogonality, while optimizing the grid quality based on numerical scheme criteria.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a structured grid is used for the reservoir, then the grid is easy to generate and compute, but it cannot accurately represent geometric discontinuities such as wells and fractures
Solution Approach 1:
The grid is divided into multiple zones: a structured reservoir grid for the bulk formation, a structured well grid for individual wells, and unstructured transition grids connecting them. This segmentation allows each zone to be optimized for its specific function while maintaining overall system coherence.
Solution Approach 2:
Different grid types are applied locally to different regions: structured grids in areas requiring regularity and computational efficiency, and unstructured grids in areas requiring geometric flexibility. The transition zones use unstructured grids to bridge between structured regions, allowing each local area to have the grid quality appropriate to its requirements.
2Manufacturing precision
If an unstructured grid is used to represent complex geometry, then geometric accuracy is improved, but the grid generation becomes more complex and computationally intensive
Solution Approach 1:
The domain is segmented into regions where unstructured grids are only generated in necessary transition zones rather than throughout the entire reservoir. This limits the complexity of unstructured grid generation to specific localized areas while maintaining structured grids in the majority of the domain.
Solution Approach 2:
Transition grids act as intermediaries between structured reservoir and well grids. These unstructured transition grids provide the necessary geometric flexibility to connect structured grids of different orientations and resolutions, serving as a mediator that resolves the incompatibility between different structured grid systems.
3Measurement precision
If the transition grid cell size is too small, then the representation of radial flow directions is more accurate, but the computational cost increases significantly
Solution Approach 1:
The transition grid uses non-uniform cell sizing where smaller cells are concentrated in the immediate vicinity of wells where radial flow accuracy is critical, while larger cells are used in regions farther from wells where flow patterns are less sensitive to grid resolution. This local refinement strategy maintains accuracy where needed while controlling overall computational cost.
Data Source
AI summary
A method, having application for hydrocarbon reservoir simulation, generates a hybrid grid, in order to carry out simulations in accordance with a defined numerical scheme, in three dimensions in a numerical scheme, of a heterogeneous formation crossed by at least one geometric discontinuity such as, an underground formation where at least one well has been drilled, or a fractured formation, by combining structured grids and unstructured grids. The hybrid grid includes a first structured grid for gridding the heterogeneous medium with second structured grids for gridding a zone around each discontinuity. A cavity of minimum size is automatically generated, with cells of the transition grid being an intermediate size between the size of the cells of the first grid and the size of the cells of the second grids.