Experimental Results and Simulation of Bench-Scale CO2 Flow and Transport in Geologic Media

We developed and conducted both laboratory experiments and computer model simulations of CO₂ injection and flow through saturated geologic media, to explore the complex physical and chemical interactions between the CO₂, pore brine, and rock matrix under specific pressure and temperature conditions. Our ultimate goal is to evaluate the viability, risks, and optimal locations of sequestering CO₂ in geologic strata proximal to power plants. Apparent dissolution and precipitation were observed in our recent CO₂-brine core flow experiments. We used these experiments to calibrate 1- and 2-D simulation models of chemically reactive flow and transport at the core-scale. The flow and chemistry model we used consists of public domain codes, including the Los Alamos Laboratory reactive chemistry simulator TRANS coupled to the Lawrence Berkeley Laboratory flow simulator TOUGH2, also utilizing a specially developed multiphase CO₂ equation of state. Model simulations were designed to mimic experimental rock composition, brine composition, and volumes of brine and CO₂ injected under reservoir conditions. Rock types included a quarried Indiana limestone, a dolomite-anhydrite reservoir core, and a quartz sandstone. Sensitivity analyses considered variations in parameters such as brine pH, brine alkalinity, rock lithology, and spatial/temporal scaling. Simulation results were quantitatively consistent with observed experimental porosity and permeability changes, and component dissolution and precipitation. In specific, varying brine pH and alkalinity resulted in ~5 % difference in mineral volume fraction at time scales of ~1 year, depending upon the mineral assemblage. However, results among different rock types were extremely different, suggesting that CO₂ sequestration targets in some geologic strata may induce dramatic changes in CO₂ mobility and storage potential.