Abstract
In this paper we present the results of an integrated field and experimental study on the geochemical reactions in a sandstone reservoir at Nagaoka, Japan, where the first Japanese pilot project of CO 2 geological storage is underway. Prior to the CO 2 injection, we collected formation water and rock samples from the reservoir, and conducted laboratory experiments to investigate the geochemical reactions when injecting CO 2 into the reservoir. About 1 year after stopping the CO 2 injection, we again collected formation fluid using a Cased Hole Dynamics Tester (CHDT) at one of the three observation wells where CO 2 breakthrough was confirmed by time-lapse well logging. Chemical analyses of the post-CO 2 injection samples indicate a high HCO 3 − concentration compared to original formation water. Concentrations of Ca, Mg, Fe, Mn and Si also increased. The field results were quite similar to the laboratory experiments on CO 2–water–rock reactivity. Our results demonstrated the potential of CO 2 storage by formation water dissolution and mineral trapping of CO 2.
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