Interactions between CO2 and rock in heterogeneous reservoirs during CO2 storage

Abstract

Reactive transport simulations of CO2 storage in heterogeneous reservoirs are performed using the PHREEQC software by Parkhurst and Apello. When CO2 dissolves in the pore water carbonic acid is formed. These aqueous species can react with the minerals in the reservoir and change the rock properties. Dissolving parts of heterogeneities may change vertical communication in the reservoir, increasing the storage capacity. The heterogeneities are modeled as low permeable layers in both the Frio formation at the Gulf of Mexico, and the Utsira formation in the North Sea. The results are heavily dependent on simulation boundary conditions and on how the pore waters are treated during the carbonation process. Calcite dissolution varying from only minor in one case to large amounts is evident of this. The dissolution of minerals in general seems to be highly dependent on pH, but apart from the calcite case, only minor dissolution occurred at the small time span of these simulations (<60 days). There was however observed minor precipitation of dawsonite.