A Parallel Multiblock Black-Oil Model in Multimodel Implementation

Abstract

Summary In this paper we discuss the multiblock algorithm for an implicit black-oil model as implemented in the multiphase simulator framework of IPARS (Integrated Parallel Accurate Reservoir Simulator). The multiblock algorithm decomposes the simulation domain into multiple nonoverlapping subdomains, or blocks, according to the geometric, geological, and physical/chemical properties, and well distribution. Each block can have its own grid system, and the grids of the neighboring blocks can be nonmatching on the interface, which allows for local grid refinement, or discrete fault or fracture modeling. Adjacent blocks are coupled across the interface by a set of conditions imposing a continuity of both primary variables and component mass fluxes that is realized through the use of special interface mortar variables. The resulting system is solved by an interface Newton procedure. Regularization techniques and preconditioners are proposed to improve the performance of the solver. The multiblock technique is effective and scalable, as shown by our numerical experiments. In addition, we present how the multiblock black-oil model has been used in the coupling of different physical models.