Numerical Modeling of CO2 Mineralisation during Storage in Deep Saline Aquifers

Simulations are performed to evaluate the feasibility of a potential site within the Rotliegend sandstone formation in the Dutch subsurface at a depth of around 3000 m for CO2 sequestration using the numerical simulator CMG-GEM. Three CO2 storage trapping mechanisms are studied: (1) mobility trapping, (2) solubility trapping, and (3) mineral trapping. Results show that the injected CO2 initially migrates towards the top of the reservoir due to gravity segregation. Then the CO2 spreads laterally and dissolves in the formation water (brine). Due to the dissolution of CO2 the density of the brine increases, which then results in fingering due to gravity. Further, the effect of mineralisation is included in the simulation. It is found in this study that considerable amounts of CO2 are stored mainly by solubility and mobile trapping. The contribution of mineral trapping is insignificant. Additionally, the effect of varying the permeability and the residual gas saturation on the CO2 storage-capacities are studied. It is found that a random permeability field enhances CO2 capturing by means of solubility trapping, while a higher residual gas saturation enhances the CO2 storage by means of mobility trapping. (C) 2011 Published by Elsevier Ltd.