Three-dimensional unstructured gridding for complex wells and geological features in subsurface reservoirs, with CVD-MPFA discretization performance

Grid generation for reservoir simulation, must honour classical key geological features and multilateral wells. The to be honoured are classified into two groups; (1) involving layers, faults, pinchouts fractures, (2) well distributions. In the former, control-volume boundary aligned grids (BAGs) required, while in latter, control-point (defined as centroid of control-volume) (WAGs) required. Depending on discretization method type formulation, a choice is made, i.e. cell-centered primal grid cells act control-volumes, otherwise vertex-centered dual-grid control-volumes. Novel three-dimensional unstructured methods proposed that automate alignment control point complex wells, yielding essentially perpendicular bisector (PEBI) meshes either with respect or dual-cells depending type. Both types use tetrahedra, pyramids, prisms hexahedra elements. Primal-cell feature generated using special surface protection techniques together constrained trajectory alignment. Dual-cell from underlying primal-meshes, whereby protected such dual-cell faces interior boundaries, (control point) novel presented enable practical application both 3-D first time. dual here demonstrate gridding methods, comparative performance study cell-vertex versus distributed multi-point flux approximation (CVD-MPFA) finite-volume formulations equivalent mesh resolution challenging problems 3-D. Pressure fields computed by CVD-MPFA schemes compared contrasted relative respective degrees freedom employed, benefits each Stability limits also explored. For given uses approximately fifth unknowns used proves most beneficial accuracy efficiency. Numerical results show outperform method.