Structured flow-based gridding and upscaling for reservoir simulation

When we construct coarse models for reservoir simulation based on fine grid geocellular descriptions, the use of curvilinear grids enables more efficient representations of important features in the reservoir. Upscaling methods compatible with these grids must also be applied.; In this thesis, we develop and apply gridding and upscaling techniques in the context of structured grids. In 2-D, for grid generation techniques, we first considered streamline-based gridding with Laplacian smoothing to capture high flow regions effectively and with improved grid quality over pure streamline grids. Two other structured gridding methods (the Jacobian-based elliptic method and optimization-based method) were investigated to achieve better local control of grids and incorporate additional information (not necessarily flow-based). Upscaling techniques to compute effective properties for these grids were also implemented. We first developed a new finite element-based method to resolve the coarse cell geometry accurately. We also developed two finite difference-based procedures (permeability upscaling and transmissibility upscaling). They offer an approximate treatment of the coarse cell geometry but display better computational efficiency than the finite element method. We observed similar accuracy in 2-D flow results for the finite element and the finite difference-based methods. We therefore implemented the more efficient finite difference methods in 3-D. The gridding techniques implemented in 3-D include the streamline-based method with Laplacian smoothing and the Jacobian-based elliptic method. We extended permeability upscaling and transmissibility upscaling to 3-D and compared their performance (within the context of multipoint and two-point flux approximations, respectively) for several cases.; We evaluated our gridding and upscaling techniques for various heterogeneous permeability fields and flow scenarios. These flow tests demonstrate that for many cases, the coarse models constructed by combining our gridding and upscaling methods result in considerable improvements over uniform Cartesian models at the same coarsening level. This demonstrates that our gridding procedures correctly resolve the critical features in the reservoir and that our upscaling techniques introduce appropriate effectivizations of subgrid heterogeneity. The tests also show that transmissibility upscaling generally produces better results than permeability upscaling.