Relative permeability for multiphase flow for oven-dry to full saturation conditions

摘要

Numerical simulation of supercritical CO2 (CO2) injection into deep geologic reservoirs often requires the modeling of multifluid flow and transport. The classical capillary and relative permeability models assume that the residual water is immobile and irreducible. This assumption is not in agreement with the flow process for CO2 injection into a saline aquifer. In this paper, the relative permeability (k(r))-saturation (S) relationships for both the aqueous and non-aqueous phases are derived for oven-dry (i.e., zero liquid saturation) to full saturation conditions by extending the classical k(r)-S relationships. The extended relative permeability models reduce to the corresponding classical forms when the aqueous saturation is higher than the critical value, but deviates from the latter when the aqueous saturation is lower than the critical value. The implementation of the extended models in the STOMP multifluid flow and transport model is demonstrated by the simulation of dry CO2 injection from a vertical well into a homogeneous reservoir. The extended models overcome the limitations of the classical models and can simulate the dry-out processes associated with the residual water. The extended models are expected to simulate CO2 injection and the subsequent processes (e.g., the dry-out of brine and salt precipitation) more accurately than the classical models. (C) 2016 Elsevier Ltd. All rights reserved.