Relative Permeability Experiments of Carbon Dioxide Displacing Brine and Their Implications for Carbon Sequestration

To continue running our civilization on fossil fuels while avoiding global warming and ocean acidification, anthropogenic carbon dioxide must be diverted from atmospheric release. For geologic carbon sequestration, the injection of CO 2 into the lithosphere, to operate at the necessary large scale requires an understanding of the multiphase flow properties of high-pressure CO 2 displacing brine in porous media. A laboratory-scale core flooding reactor has been built to measure flow properties at in situ pressures, salinities, and temperatures. The reported set of experiments was designed to measure CO 2 relative permeability for CO 2 displacing brine at residual brine saturation. Endpoint drainage CO 2 relative permeability was found to be tightly clustered around 0.35-0.4. These values indicate that CO 2 is not strongly nonwetting, and are characteristic of weakly water-wetting or intermediate wetting flow. Based on these results, CO 2 injectivity will be reduced, pressure-limited reservoirs will have reduced capacity, and inclined area-limited reservoirs will have increased capacity. Future reservoir-scale modeling efforts should incorporate sensitivity to relative permeability. Assuming the majority of reservoirs are pressure limited and if the experimental results reported here are found to apply to other lithologies as well, geologic carbon sequestration at scale will require approximately twice the number of storage sites, wells, reservoirs, and the related infrastructure, personnel, and cost.