CO2 sequestration in basalt: Carbonate mineralization and fluid substitution

Basalt rocks contain some of the most reactive minerals when in contact with CO2-water mixtures. The chemical reaction between minerals rich in calcium, magnesium and iron and carbonic acid precipitates carbonates in the pore space. This process would increase the elastic moduli and velocity of the rock. At the same time, the higher compressibility of CO2 over water changes the elastic properties of the rock, decreasing the saturated rock bulk modus and the P-wave velocity. Reservoirs where the rock properties change as a result of fluid or pressure changes are commonly monitored with seismic methods. Here we describe experiments to study the feasibility of monitoring CO2 migration in a reservoir and CO2-rock reactions for a sequestration scenario in basalts. Our goal is to measure the rock's elastic response to mineralization with non-contacting ultrasonic lasers, and the effect of fluid substitution at reservoir conditions at seismic and ultrasonic frequencies.