Predicting the CO2 Footprint in Saline Aquifers: A Numerical-analytical Hybrid Model

Abstract

In this study, we present a hybrid framework in which we combine pore-scale lattice Boltzmann (LB) simulations with a macroscopic analytical model for predicting CO2 plume migration and its residual trapping in saline aquifers. These integrated methods combine the flexibility of a pore-scale simulation method, allowing for implementing the micro-scale properties such as wettability, with the efficiency of an analytical method, for a quick estimation of the CO2 plume extension and its residual trapping during the injection and post-injection stages. The LB model is adopted to perform two-phase flow simulations of CO2/brine in the microstructure of a rock sample of Tuscaloosa sandstone taken from the Cranfield site in Mississippi. Employing the pore-scale LB simulations, we estimate pore-scale properties such as connate brine saturation, CO2 residual saturation, and CO2 end-point relative permeability. Subsequently, these parameters have been used in the analytical model for predicting the macro-scale behavior of CO2 plume during the injection and post-injection periods. To gain a better insight into the effect of wettability on the footprint of CO2 plume and its residual trapping, we run pore-sale simulations in different samples under various wetting conditions and calculate the pore-scale properties as a function of wettability. Thus, incorporating the pore-scale simulation results into the analytical model helps us evaluate the effect of pore-scale properties such as wettability on storage efficiency. We believe that this approach provides an appropriate tool for the estimation of storage efficiency in CO2 sequestration projects.