Assessment of CO₂ Sequestration Operation in an Offshore Sandstone Formation in the Pearl River Mouth Basin, South China Sea

Offshore operations have been done in several aquifers globally, but there remain uncertainties on the injection strategy and fraction that is mineralized over a given time scale. Here, using reactive transport modeling, we examine the potential for a China offshore CO2 sequestration operation in a shallow subsea feldspar-quartz sandstone formation located in the Pearl River Mouth Basin in the South China Sea. The results from the model demonstrate that the offshore CO2 sequestration in this feldspar-quartz sandstone formation is possible and showcase that given the initial aquifer composition and minerals, dissolution of K-feldspar occurs. A dynamic reactive behavior occurs at the front edge of the CO2 plume where the dissolved CO2, in the form of bicarbonate ions, reacts with divalent cations in the aquifer water to yield carbonate mineral precipitates, which is subsequently dissolved when the acidified water in the plume passes the prior front location.