Hex-dominant mesh modeling for sedimentary basin poromechanics
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Solution Overview
Problem
Current basin simulation tools struggle with accurately modeling sedimentary basins featuring thin layers and stratigraphic bevels, leading to numerical instability and poor simulation quality due to the need for high mesh densities and unfavorable geometry, which prevents precise simulation of mechanical behavior and hydrocarbon accumulation.
Innovation Solution
A face-based smoothed finite element method (FS-FEM) is employed to stabilize the numerical simulation of sedimentary basins by subdividing hexahedral meshes into smaller sub-meshes, determining smoothing domains, and calculating deformation and stress fields, allowing for accurate determination of stress and displacement fields even in hexa-dominant meshes with thin layers and bevels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional basin simulation tools are used to model sedimentary basins with thin layers and stratigraphic bevels, then the simulation can be performed with standard mesh densities, but the numerical stability deteriorates and simulation quality becomes poor
Solution Approach 1:
The patent applies segmentation by dividing each hexahedral mesh element into multiple sub-elements (typically 8 sub-elements per parent element). This refinement strategy allows the model to capture thin layers and bevels without requiring excessive mesh density throughout the entire domain, thereby maintaining numerical stability while improving simulation accuracy for complex geological structures.
Solution Approach 2:
The patent implements local quality enhancement by applying selective mesh refinement only in regions containing thin layers or stratigraphic bevels, while maintaining coarser mesh density in other areas. This localized approach improves numerical stability where needed without sacrificing overall simulation productivity, as the refined regions are limited to specific geological features rather than the entire basin model.
2Manufacturing precision
If mesh density is increased to accurately represent thin layers and bevels, then the geometric accuracy improves, but the computational complexity and simulation time increase significantly
Solution Approach 1:
By segmenting parent hexahedral elements into smaller sub-elements, the patent achieves high geometric accuracy for thin layers and bevels without requiring the entire mesh to be densely populated. The segmentation is applied selectively to elements containing geological features of interest, reducing overall mesh complexity while maintaining precision where required.
Solution Approach 2:
The patent addresses geometric accuracy challenges by introducing an additional level of discretization within existing mesh elements through sub-element division. This dimensional approach allows accurate representation of thin features without increasing the number of parent elements, thereby avoiding the computational burden associated with globally dense meshes.
3Ease of manufacture
If standard hexahedral meshes are used for basin simulation, then the mesh generation is simpler and faster, but the simulation accuracy for stress and deformation fields deteriorates in complex geometries
Solution Approach 1:
The patent maintains ease of mesh generation by starting with standard hexahedral elements that can be automatically generated using conventional basin modeling software. The accuracy improvement is achieved through post-generation segmentation of these standard elements into sub-elements, preserving the simplicity of initial mesh creation while enhancing stress and deformation field calculation accuracy through the refined sub-structure.
Solution Approach 2:
The patent applies preliminary action by pre-defining the segmentation scheme and sub-element configuration before running the basin simulation. This preparatory step ensures that the mesh structure is optimized for stress and deformation calculations from the outset, without requiring complex adaptive meshing during the simulation process, thus maintaining ease of implementation while improving measurement precision.
Data Source
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AI summary
The present invention relates to a method for modeling a sedimentary basin by means of a numerical basin simulation that solves at least one poromechanical equilibrium equation using a face-based smoothed finite element method to determine at least one stress field and one strain field. The method according to the invention includes, in particular, the following steps: subdividing the hexahedral cells of a meshed representation of a basin state into at least eight hexahedral subcells; determining a transition relationship between the degrees of freedom of the nodes of the subcells and the degrees of freedom of the nodes of the cell to which the subcells belong; and determining stiffness and nodal forces from at least this transition relationship and a strain-displacement relationship determined for the subcells.