Houman Borouchaki

Hex-dominant mesh generation for basin modeling with complex geometry

Basin modeling aims to reconstruct the geological history of a basin and its oil system by means of fluid flow simulations, which is done by using a series of meshes describing basin geometry at each geological instant. These meshes are preferably hexahedral rather than tetrahedral in virtue for better numerical results. The basin can simply consist of geological layers delimited one from another by horizons. It can be geometrically complex with one or more faults interrupting the layers, which is barely studied but increasingly demanded. This paper exposes an automatic method which generates hex-dominant meshes for basin modeling with complex geometry. Firstly, based on their triangulations at the latest instant, 3D surface grids are generated with identical topology for all the horizons, and with some quadrilaterals being split across the diagonals to adapt to fault traces. Afterwards, all instants are iterated to generate corresponding meshes by firstly applying horizon and fault displacement on the mesh generated for precedent instant; the method then connects the bottom and top surface grids of the new layer along corresponding nodes, and splits certain cells along faults when necessary. Simulations have been carried out on generated meshes with satisfactory results.

Hybrid Mesh Generation for Reservoir Flow Simulation in CPG Grids

In this paper, we introduce a new method to generate a hybrid mesh from a CPG (Corner Point Geometry) reservoir grid and a radial mesh around a well. The method is an extension of the approach proposed in [1] to the case of CPG grids with high level of deformation. This ensures a fully functional mesh generation for realistic cases. The main idea is first to construct a mapping between the real space containing the CPG grid along with the radial mesh of the well and a virtual space where the CPG reservoir grid becomes a Cartesian grid. Then, because this mapping damages the circular property of the radial mesh, an appropriate radial mesh is built in the virtual space and the initial mapping is modified by taking into account the new radial mesh in the virtual space. To this end, an optimization technique using mesh refinement procedures is applied. The mapping combined with the mentioned deformation allows us to generate an unstructured polyhedral transition mesh (between the reservoir grid and the radial mesh) in the virtual space using the algorithm proposed in [1]. Finally, coming back to the real space, the obtained hybrid mesh may require a post processing step to recover the requested finite volume properties.