PNNL

Abstract

Numerical simulation of supercritical CO2 (scCO2) injection into deep geologic reservoirs often requires the modeling of multifluid flow and transport. The classical retention and relative permeability models assume that the residual water is immobile and irreducible. This assumption is not in agreement with the flow process for scCO2 injection into a saline aquifer. In this paper, the relative permeability – saturation relations for both the wetting and non-wetting phases are derived for oven-dry to full saturation conditions. 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 extended models can be easily incorporated into numerical simulators. The implementation in the STOMP multifluid flow and transport model is demonstrated by the simulation of dry scCO2 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 more accurately than the classical models.