Effects of physical sorption and chemical reactions of CO2 in shaly caprocks

Abstract

A comprehensive experimental approach has been used to assess the interrelation of CO2-mediated chemical reactions and transport properties in pelitic rocks. Sorption values on shale samples (P<20 MPa, 50 {ring operator}C) were high with maximum amounts of ∼44 kg/t. These capacities did not correlate with the organic carbon content, indicating sorption on and/or reaction with mineral components. Further, crushed shale samples were exposed to CO2 in the presence of water at 15 MPa and 50 {ring operator}C for different time periods, showing significant changes in mineral composition. Reaction equilibrium was reached within periods of less than a month. Some of the caprock lithotypes could represent a significant sink for CO2 deposited in the subsurface and could reduce the risk of leakage to the surface. © 2009 Elsevier Ltd. All rights reserved.