Storing CO2 in buried volcanoes

Abstract

Australia contains rich natural gas resources, but many of Australia’s currently producing and undeveloped gas fields contain relatively high CO2 contents; if not captured and stored, the venting of co-produced CO2 could hinder efforts to meet Australia’s emission reduction targets. The most mature technology for isolating produced CO2 from the atmosphere is by containing it in deep sedimentary formations (e.g. saline aquifers or depleted oil and gas reservoirs). The effectiveness of this approach is dependent on factors such as reservoir capacity, the presence of low-permeability seals that physically impede vertical migration of injected CO2, the chemical reactivity of both reservoir and seal minerals, the risk for leakage, and a gas-entrapping structure. An alternative and attractive mechanism for permanent storage of CO2 is geochemical or mineral trapping, which involves long-term reactions of CO2 with host rocks and the formation of stable carbonate minerals that fill the porosity of the host rock reservoir. Natural mineral carbonation is most efficient in mafic and ultramafic igneous rocks, due to their high reactivity with CO2. Here we review the outcomes from a series of recent pilot projects in Iceland and the United States that have demonstrated high potential for rapid, permanent storage of CO2 in basalt reservoirs, and explore the practicalities of geochemical trapping of CO2 in deeply buried basaltic volcanoes and lava fields, which are found in many basins along the southern (e.g. Gippsland Basin) and northwestern (e.g. Browse Basin) Australian margins, often in close proximity to natural gas fields with high CO2 content.