Corner-point mesh for accurate petroleum migration modeling
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Solution Overview
Problem
Conventional grid-based models for subsurface oil and gas flow simulation are crude and fail to accurately represent real-world petroleum systems, leading to distorted migration pathways and loss of important details due to averaging or omission of thin features with high impedance.
Innovation Solution
A corner-point mesh system is used to model reactant migration, where nodes represent points in space and physical characteristics like fluid pressure, water fraction, and gas fraction are calculated to determine reactant migration, allowing for partial filling of elements and more accurate representation of subsurface structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a regular orthogonal grid is imposed on the subsurface model, then the model structure is simple and easy to implement, but the model becomes crude and fails to accurately represent thin features with high impedance to migration
Solution Approach 1:
The model divides the subsurface into discrete grid cells with explicit tracking of migration pathways through individual cells. Each cell can independently represent thin features, and migration is calculated cell-by-cell through explicit pressure gradient computations, allowing accurate representation of impedance variations without requiring the entire grid to be refined.
Solution Approach 2:
The model applies different properties and calculations to individual grid cells based on their local characteristics. Thin features with high impedance can be accurately represented in specific cells while maintaining coarser representation elsewhere. The migration calculation adapts to local pressure gradients and rock properties, providing locally accurate flow representation without global refinement.
2Productivity
If grid cells are used to represent subsurface structures, then the model is computationally efficient, but thin features with high impedance to migration are averaged out or omitted entirely
Solution Approach 1:
The model segments the subsurface into discrete grid cells where each cell's properties are explicitly defined. Thin features are represented as individual cells or small sequences of cells with specific impedance values, preventing averaging. Migration is calculated through explicit cell-to-cell flow equations that preserve detail in each segment.
Solution Approach 2:
The model creates a digital representation of the subsurface where thin features are copied into the grid structure with their specific geometric and petrophysical properties preserved. Each thin feature is represented by grid cells containing its exact thickness, permeability, and other properties, allowing accurate migration simulation without physical scaling issues.
3Device complexity
If internal inclined planes are converted into horizontal planes in staircase configuration, then the grid structure is simplified, but natural directions of flow and internal watersheds are poorly approximated
Solution Approach 1:
The model dynamically calculates migration pathways based on local pressure gradients and rock properties rather than following fixed grid directions. Flow can move in any direction through the grid based on the steepest descent of pressure, naturally capturing watershed divides and flow directions without requiring the grid geometry to match the flow paths.
Solution Approach 2:
The model uses pressure gradient as the controlling parameter for migration direction rather than grid orientation. By calculating pressure fields and deriving flow directions from gradients, the model can represent inclined planes and complex topography through parameter variations (pressure, permeability, saturation) rather than requiring the grid structure itself to be inclined or complex.
Data Source
AI summary
A method for modelling the migration of reactant in a subsurface petroleum system is described. The method comprises in part generating a mesh for an area of the petroleum system. The mesh comprises a plurality of nodes, with each node representing a point in space in the area. The method also comprises calculating one or more variables representing one or more physical characteristics at each node in the area and determining the migration of reactant in the petroleum system based on the one or more variables. The method can also handle multiple reactant phases and non-static meshes.