Basaltic rocks and their potential to permanently sequester industrial carbondioxide emissions

摘要

Injection of anthropogenic CO_2 into deep aquifers is one of the promising geological storage options being considered for CO_2 sequestration. The retention time and environmental safety of the CO_2 storage depend on the chemical reactions between the injected CO_2, the reservoir fluid and the host rocks. The pH buffer capacity of aquifer water and the acid neutralization potential of the aquifer rocks are important factors for stabilization of the injected CO_2. Mafic rocks such as basalt, which primarily consists of calcium, magnesium silicate minerals provide alkaline earth metals necessary to form solid carbonate minerals. The carbonate minerals formed thus sequester CO_2 in a chemically stable and environmental benign form. We explore the scientific and technical potential of deep basalt formations for long-term storage of CO_2 as an alternative to the more common sedimentary reservoir rocks. The significant global storage capacity onshore as well as offshore and the high potential for secure and permanent sequestration as stable (Ca, Mg, Fe)CO_3 minerals demonstrate the importance of basalt as a potential sequestration target. Small-scale CO_2 injection experiments have been carried out as single well push-pull tests to study CO_2-water-rock reactions under natural in situ conditions. The in situ tests confirm rapid acid neutralization rates and water-rock reactions sufficient for safe and permanent geologic storage of CO_2.