Mechanistic modelling of non-equilibrium interphase mass transfer during solvent-aided thermal recovery processes of bitumen and heavy oil

Abstract One of the important mechanisms involved in solvent-aided thermal recovery processes is interphase-mass transfer phenomenon. However, in current reservoir simulation models a local equilibrium is commonly assumed such that a simulation grid block is at instantaneous equilibrium. The assumption of local equilibrium often fails at larger scales or in situations where flow velocities are considerable compared to that of mass or heat transfer which results in significant discrepancies between reservoir simulation predictions and field scale observations. In this work, solvent-aided gravity drainage of bitumen was simulated with propane as a solvent. The effect of non-equilibrium mass transfer was included in the model to simulate the process using a kinetic approach. The results show that the assumption of the local instantaneous equilibrium results in lower oil recovery for the typical field scale simulation models. The analysis shows that this mismatch can be mitigated fairly through the inclusion of the non-equilibrium interphase mass transfer. Correlations for the non-equilibrium interphase mass transfer coefficients for propane/bitumen mixture were developed which can be used as guidelines for field scale modeling of solvent-aided thermal recovery processes.