Experimental and theoretical investigation of the mechanisms of drying during CO(2) injection into saline reservoirs

A viable CO(2) storage resource must have sufficient storage capacity, reliable containment efficiency and adequate well injectivity. Deep saline formations stand out in terms of storage capacity and containment efficiency. However, formation brine dry-out and salt precipitation in the near well region could impair CO(2) injectivity in deep saline reservoirs, thus reducing their potential for CO(2) storage. Core-flood experiments and analytical modelling were used to investigate various mechanisms of external and internal salt precipitation. Particularly, the impact of the extension of the dry-out region on CO(2) injectivity was investigated. It was found that, for high permeability rocks, injection of CO(2) at relatively low injection rates could result in salt cake deposition at the injection inlet especially under high salinity conditions. It was also found that extension of the dry-out region does not have significant impact on CO(2) injectivity. Although the magnitude of CO(2) injectivity impairment increased more than two-fold when initial brine salinity was doubled, real-time changes in CO(2) injectivity during the drying process was found to be independent of initial brine salinity. We have shown that the bundle-of-tubes model could provide useful insight into the process of brine vaporization and salt deposition in the dry-out region during CO(2) injection. This work provides vital understanding of the effect of salt precipitation on CO(2) injectivity.