A Parallel
Black
Oil
and Compositional Multiphase Flow Simulator for Unstructured 3-D Finite Element Grids
Abstract
We present a massively parallelized reservoir simulator for both black
oil
and fully compositional three-phase flow. The simulator is built on higher-order finite element methods that are well suited to parallelization and provide maximum flexibility in conforming the computational grid to any geological formation geometry. We consider gas,
oil
, and water phases. Phase compositions and fluid properties can be described by either a
black
oil
model (for greater computational efficiency) or a fully compositional equation-of-state model (for more challenging problems, such as enhanced
oil
recovery by CO2 injection). We adopt an implicit-pressure-explicit-saturation/composition scheme. Mass conservation equations are solved explicitly by a local discontinuous Galerkin (DG) method, which allows a higher-order approximation of phase compositions within each element. The DG method is locally mass conserving and readily parallelizable. Phase-split calculations are computationally expensive, but strictly local and also trivially parallelized. Finally, we use a mixed hybrid finite element (MHFE) method to simultaneously solve for globally continuous pressure and velocity fields. The MHFE pressure update is implicit and results in a non-trivial parallelization problem involving domain decomposition. This is particularly challenging for fully unstructured grids, such as tetrahedralizations. We present a number of complex large-scale simulation results that demonstrate the robustness, accuracy, and scalability of our parallel finite element reservoir simulation model.
AAPG Datapages/Search and Discovery Article #90216 ©2015 AAPG Annual Convention and Exhibition, Denver, CO., May 31 - June 3, 2015