Hybrid Grid Intersection Cell Resizing for Two-Phase Flow Simulation
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Solution Overview
Problem
Existing methods for simulating fluid flow in fractured geological media, such as petroleum reservoirs, are inadequate for accurately modeling two-phase flow due to the simplification of intersection cells, leading to imprecise results and excessive computational costs.
Innovation Solution
A hybrid, locally non-matching grid system is introduced, where intersection cells are resized to avoid approximations, allowing for precise simulation of fluid flow characteristics by redistributing grid portions and calculating split flow properties, thereby enabling more efficient time stepping and reduced computational intensity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If intersection cells are removed and Y-A approximation is used, then computational efficiency is improved, but accuracy for two-phase flow simulation deteriorates
Solution Approach 1:
The patent applies local quality by creating a hybrid grid where intersection cells are retained and enlarged only in specific locations where fractures intersect, while maintaining a coarser grid structure elsewhere. This localized refinement allows accurate simulation of two-phase flow at critical intersection points without compromising the computational efficiency gained from the overall coarse grid structure.
Solution Approach 2:
The patent segments the grid into different types of cells: standard matrix blocks, fracture cells, and specially enlarged intersection cells. This segmentation allows the model to treat different regions differently - using coarse approximation for most areas while using refined geometry at intersections where it matters most for accurate two-phase flow characterization.
2Measurement precision
If time step is reduced to capture intersection block characteristics, then simulation accuracy is improved, but computational cost increases excessively
Solution Approach 1:
The patent implements dynamic time step adjustment based on local grid characteristics. The time step is calculated separately for different cell types, with intersection cells using their own time step criteria while surrounding matrix blocks can use larger time steps. This dynamic approach allows the simulation to capture accurate flow characteristics at intersections without forcing the entire model to use excessively small time steps.
Solution Approach 2:
By segmenting the grid into different cell types with different time step requirements, the patent allows each segment to be simulated with appropriate temporal resolution. Intersection cells maintain small time steps for accuracy, while the coarser matrix blocks can progress with larger time steps, significantly reducing overall computational cost.
3Device complexity
If grid blocks at fracture intersections are removed, then model complexity is reduced, but flow approximation accuracy deteriorates
Solution Approach 1:
The patent applies local quality by retaining intersection cells with proper geometry only where fractures intersect, while using simplified approximations for fracture cells that do not intersect. This localized approach maintains geometric accuracy at critical points without unnecessarily complicating the entire grid structure.
Solution Approach 2:
The patent merges the representation of multiple fractures into a single enlarged intersection cell, combining the geometry and flow characteristics of intersecting fractures into one integrated cell. This merging approach maintains accuracy for multi-phase flow at intersections while simplifying the overall grid structure compared to representing each fracture separately with multiple small cells.
Data Source
AI summary
Systems, methods, and computer-readable media are provided for modeling a fractured medium. The method includes generating, using a processor, a grid for the fractured medium, the fractured medium defining a first fracture and a second fracture, with the first fracture and the second fracture each represented by fracture cells in the grid. The method also includes determining a location where the first and second fractures intersect, the location being at least partially represented by an intersection cell of the fracture cells of the grid. The method further includes redistributing areas of the intersection cell and at least one other fracture cell, such that a size of the intersection cell is increased.