Mapping Geo-Cellular Models to Unstructured Simulation Grids

To date, while there are a wide variety of property modeling tools for structured grids, one of the main obstacles to reservoir simulation on unstructured grids is how to transfer these from the geo-cellular grid to an unstructured grid in a consistent and conservative fashion. This needs to be accomplished while honoring layer boundaries, unconformities and faults.

This contribution presents a new method designed to populate unstructured, adaptively refined tetrahedral finite element meshes with highly resolved petrophysical properties from a commercial property modeling tool. Properties from volumetric as well as surface meshes embedded into the 3D domains, are mapped to corresponding tetrahedral and triangular meshes using a barycentric mesh traversal scheme. Solving Laplace equation on the unstructured grid using the modeled property values as constraints, allows us to interpolate them to tetrahedra that do not contain geo-cellular data. The results are of high quality as is indicated by a statistical analysis comparing original with mapped property histograms and variograms. Integral values such as pore volume and original oil in place show a high quality match when compared with an evaluation of the geo-cellular model. The method is demonstrated for the well-known Clyde model including simulations with an original hybrid finite-element finite-volume method. Download paper here