Modelling of bypassed oil recovery in EOS compositional simulation

The local equilibrium assumption in the conventional composition simulation allows for no bypassing of oil at the sub-grid scale. Oil bypassing by gas, however, always occurs due to micro and macroscopic heterogeneities, gravity, and front instability.;This research presents an efficient two-step method to model bypassed oil recovery in multiphase compositional flow simulation of gas floods. The oil bypassing is first quantified by use of the dual-porosity flow with three dimensionless groups: the bypassed fraction, throughput ratio, and longitudinal Peclet number. To represent bypassed oil recovery in single-porosity flow, a new flow-based fluid characterization is applied to part of the heavy fractions of the fluid model used. Properties for pseudo components are determined based on the throughput ratio estimated in the dual-porosity flow. Case studies for various reservoir/fluid properties show that single-porosity flow with the new method successfully represents bypassed oil recovery observed in core-flooding experiments and fine-scale heterogeneous simulations.