摘要
Carbon capture and storage in deep geological formations is a method to reduce greenhouse gas emissions.Supercritical CO_(2) is injected into a reservoir and dissolves in the brine.Under the impact of pressure and temperature(P-T)the aqueous species of the CO_(2)-acidified brine diffuse through the cap rock where they trigger CO_(2)-watererock interactions.These geochemical reactions result in mineral dissolution and precipitation along the CO_(2) migration path and are responsible for a change in porosity and therefore for the sealing capacity of the cap rock.This study focuses on the diffusive mass transport of CO_(2) along a gradient of decreasing PeT conditions.The process is retraced with a one-dimensional hydrogeochemical reactive mass transport model.The semigeneric hydrogeochemical model is based on chemical equilibrium thermodynamics.Based on a broad variety of scenarios,including different initial mineralogical,chemical and physical parameters,the hydrogeochemical parameters that are most sensitive for safe long-term CO_(2) storage are identified.The results demonstrate that PeT conditions have the strongest effect on the change in porosity and the effect of both is stronger at high PeT conditions because the solubility of the mineral phases involved depends on PeT conditions.Furthermore,modeling results indicate that the change in porosity depends strongly on the initial mineralogical composition of the reservoir and cap rock as well as on the brine compositions.Nevertheless,a wide range of conditions for safe CO_(2) storage is identified.
基金
We would like to thank the anonymous reviewers for their constructive reviews that considerably improved the manuscript.
