An Evaluation of Sharp Interface Models for CO₂‐Brine Displacement in Aquifers

Abstract

Understanding multiphase transport within saline aquifers is necessary for safe and efficient CO2 sequestration. To that end, numerous full-physics codes exist for rigorously modeling multiphase flow within porous and permeable rock formations. High-fidelity simulation with such codes is data- and computation-intensive, and may not be suitable for screening-level calculations. Alternatively, under conditions of vertical equilibrium, a class of sharp-interface models result in simplified relationships that can be solved with limited computing resources and geologic/fluidic data. In this study, the sharp-interface model of Nordbotten and Celia (2006a,2006b) is evaluated against results from a commercial full-physics simulator for a semi-confined system with vertical permeability heterogeneity. In general, significant differences were observed between the simulator and the sharp-interface model results. A variety of adjustments were made to the sharp-interface model including modifications to the fluid saturation and effective viscosity in the two-phase region behind the CO2 -brine interface. These adaptations significantly improved the predictive ability of the sharp interface model while maintaining overall tractability.

A Pseudo‐Vertical Equilibrium Model for Slow Gravity Drainage Dynamics

“…This way, the pseudo-VE model accounts for the pseudo-segregated state of the two fluid phases that can be observed for cases with relative permeability functions with large exponents. A larger residual wetting phase saturation was used by Swickrath et al (2016) as well, leading to improved results compared to full multidimensional models. However, their residual wetting phase saturation is constant in both space and time and has to be fitted by running a full multidimensional model.…”