Coarse-Scale 3D Geological Model Upscaling via Transmissivity Reduction
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Solution Overview
Problem
Current methods for modeling subsurface reservoirs struggle to accurately represent complex sedimentary structures, particularly thin shale layers, which impact permeability, leading to increased computational complexity and inefficiency in simulations due to the need for extensive grid cell adjustments.
Innovation Solution
A method involving the formation of a coarse-scale three-dimensional geological model using triangular meshed sedimentary surfaces and tetrahedral cells, with transmissivity reduction coefficients to represent thin shale layers, allowing for more precise attribution of petrophysical parameters and upscaling of permeability values through fluid flow computations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If parametric surfaces are added to represent thin shale layers, then the accuracy of representing local heterogeneities is improved, but the number of surfaces and grid cells increases greatly, making computations more complex
Solution Approach 1:
The patent extracts the function of representing thin impermeable layers from the geometric representation (surfaces) and transfers it to a property assignment (transmissivity reduction coefficient). Instead of adding surfaces to represent thin shale layers, the invention assigns a transmissivity reduction coefficient to existing grid cells or interfaces, thereby capturing the effect of thin layers without increasing the number of geometric elements.
Solution Approach 2:
The patent changes the parameter representation from geometric (adding surfaces) to physical property-based (transmissivity reduction coefficient). By modifying the transmissivity parameter of existing cells or interfaces rather than adding new geometric elements, the invention maintains model simplicity while accurately representing the impact of thin shale layers on fluid flow.
2Manufacturing precision
If a fine-scale model with millions of grid cells is created to precisely characterize reservoir heterogeneity, then the accuracy of reservoir characterization is improved, but the computational time for simulations becomes unacceptable
Solution Approach 1:
The patent segments the computational domain into coarse-scale control volumes rather than using fine-scale grid cells. By dividing the reservoir into larger control volumes and applying transmissivity reduction coefficients at interfaces, the method captures heterogeneity effects without requiring millions of grid cells, thus reducing computational time while maintaining accuracy.
Solution Approach 2:
The patent introduces transmissivity reduction coefficients as intermediary parameters that mediate between fine-scale heterogeneity and coarse-scale simulation. These coefficients act as a bridge, allowing the coarse-scale model to account for the presence of thin impermeable layers and local heterogeneities without requiring fine-scale grid resolution, thereby reducing computational time while preserving accuracy.
3Ease of manufacture
If cubic grid cells with constant dimensions are used for modeling, then the simplicity of the model structure is maintained, but the ability to represent complex sedimentary structures with non-horizontal or vertical boundaries is lost
Solution Approach 1:
The patent moves from representing sedimentary boundaries as geometric surfaces in 3D space to representing them as interfaces between control volumes with assigned transmissivity properties. By changing the dimension of representation from spatial geometry to property assignment, the method maintains the simplicity of the grid structure while accurately representing complex sedimentary boundaries through parameter variation rather than geometric complexity.
Data Source
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AI summary
The invention discloses a method for forming a coarse-scale three-dimensional geological model of sedimentary structures, the method being implemented by a computer, and comprising: - forming a fine-scale three dimensional model of the sedimentary structures, by implementing steps of: o modeling a plurality of meshed sedimentary surfaces, the plurality of meshed sedimentary surfaces delimiting superposed layers of lithology, o forming an unstructured grid comprising a plurality of cells, wherein each cell extends between at least two sedimentary surfaces, o attributing petrophysical parameters to each cell of the grid, and o attributing, to at least some of the sedimentary surfaces, a transmissivity reduction coefficient, and - upscaling the fine-scale three dimensional model to obtain a coarse- scale three dimensional model comprising a plurality of cells, wherein each cell is associated to petrophysical parameters determined from the petrophysical parameters of the fine-scale model, and from the transmissivity reduction coefficient of the sedimentary surfaces.