Rapid porosity and permeability changes of calcareous sandstone due to CO2-enriched brine injection

Reservoir injectivity and storage capacity are the main constraints for geologic CO2 sequestration, subject to safety and economic considerations. Brine acidification following CO2 dissolution leads to fluid-rock interactions that alter porosity and permeability, thereby affecting reservoir storage capacity and injectivity. Thus, we determined how efficiently CO2-enriched brines could dissolve calcite in sandstone cores and how this affects the petrophysical properties. During computerized tomography monitored flow-through reactor experiments, calcite dissolved at a rate largely determined by the rate of acid supply, even at high flow velocities which would be typical near an injection well. The porosity increase was accompanied by a significant increase in rock permeability, larger than that predicted using classical porosity-permeability models. This chemically driven petrophysical change might be optimized using injection parameters to maximize injectivity and storage.