Investigation on porosity and permeability change of Mount Simon sandstone (Knox County, IN, USA) under geological CO 2 sequestration conditions: a numerical simulation approach

A numerical model was developed to simulate reactive transport with porosity and permeability change of Mount Simon sandstone (samples from Knox County, IN, USA) after 180 days of exposure to CO 2 ‐saturated brine under CO 2 sequestration conditions. The model predicted formation of a high‐porosity zone adjacent to the surface of the sample in contact with bulk brine, and a lower porosity zone just beyond that high‐porosity zone along the path from the sample/bulk brine interface to sample core. The formation of the high porosity zone was attributed to the dissolution of quartz and muscovite/illite, while the formation of the lower porosity zone adjacent to the high porosity zone was attributed to precipitation of kaolinite and feldspar. The model predicted a 40% permeability increase for the Knox sandstone sample after 180 days of exposure to CO 2 ‐saturated brine, which was consistent with laboratory‐measured permeability results. Model‐predicted solution chemistry results were also found to be consistent with laboratory‐measured solution chemistry data. Initial porosity, initial feldspar content, and the exponent n value (determined by pore structure and tortuosity) used in permeability calculations were three important factors affecting permeability evolution of sandstone samples under CO 2 sequestration conditions.