This paper reports findings of coreflooding limestone with co-injected carbon dioxide (CO2) and brine at reservoir pressure and temperature. Metal chlorides were added as tracer components to the injection brine and appeared in quantities well above natural levels in deposited carbonates. Core segment porosity and permeability are reported to indicate dissolution and deposition. Finally, the core was sectioned and analyzed by chemical and back-scattered electron imaging (BSEI) and chemical titration for compositional changes.
Porosity and permeability increased and decreased corresponding to suspected dissolution and precipitation. Qualitative and quantitative analyses confirmed the deposition of trace metals within deposited carbonate material, providing direct evidence of deposition. These phenomena can occur during CO2 injection into carbonate geological formations, whether for improved oil recovery (IOR) or greenhouse gas sequestration. With IOR the concern is for injectivity changes, while the issues for sequestration are long-term storage capacity and seal integrity.