Impacts of Carbonated Brine-Rock Reactions on Multiphase Flow Properties in Upper Minnelusa Sandstone: Implication for CO2 Storage

Abstract

The impact of carbonated brine-rock geochemical reactions on porosity, permeability, and multiphase flow responses is relevant to the determination of CO2 storage capacity of deep saline aquifers. In this research, carbonated brine flooding experiments were performed on core samples consisting of poorly sorted, quartz-rich sand with laminated bedding from a target CO2 storage formation in Wyoming. Complementary pre- and post-injection lab measurements were performed. Results showed that both core porosity and permeability increased after a seven-day carbonated brine injection, from 6.2% to 8.4% and 1.6mD to 3.7mD, respectively. These changes were attributed to carbonate mineral dissolution, which was evidenced by the effluent brine geochemistry, pore-throat size distribution and surface area. To be more specific, within the more permeable section of core samples, containing larger pore size, the permeability increment is apparent due to dolomite mineral grains and cements dissolution. However, for the lower permeability section, corresponding to the smaller pore size, mineral precipitation possibly lessened dissolution effects, leading to insignificant petrophysical properties changes. Consequently, the observed heterogeneous carbonated brine-rock interactions resulted in changes of CO2/brine relative permeability. This research provides a fundamental understanding regarding impacts of fluid-rock reactions on changes in multiphase flow properties of eolian sandstones, which lays the foundation for more accurate prediction/simulation of CO2 injection into deep saline aquifers.