Compositional and Black Oil Reservoir Simulation

Summary This paper describes a three-dimensional (3D), three-phase reservoir simulation model for black oil and compositional applications. Both implicit pressure, explicit saturation/concentration (IMPES) and fully implicit formulations are included. The relaxed volume balance concept effectively conserves mass and volume and reduces Newton iterations in both formulations. A new implicit well rate calculation method improves IMPES stability. It approximates wellbore crossflow effects with high efficiency and relative simplicity in both IMPES and fully implicit formulations. Multiphase flow in the tubing and near-well non-Darcy gas flow effects are treated implicitly. Initial saturations are calculated as a function of water/oil and gas/oil capillary pressures, which are optionally dependent upon the Leverett J function. A normalization of the relative permeability and capillary pressure curves is used to calculate these terms as a function of rock type and gridblock residual saturations. Example problems are presented, including several of the SPE comparative solution problems and field simulations.