Geochemical modeling of changes in caprock permeability caused by CO₂–brine–rock interactions under the diffusion mechanism

Abstract

Geologic Carbon Sequestration (GCS) has been widely considered as a significant means for reducing CO2 emissions to address global climate change. The caprock sealing plays a key role in determining permanence and security of carbon dioxide (CO2) storage in geologic formations. This study presents geochemical modeling of CO2–brine–rock interactions in a deep saline aquifer in the Jianghan Basin, which is a potential target for CO2 injection and geological storage. A one-dimensional model was developed to investigate the changes in caprock permeability caused by CO2–brine–rock interactions under the diffusion mechanism. The results show that the dissolution of K-feldspar and albite plays a key role in the variation of caprock permeability, which makes permeability increased by 60% at the bottom of caprock. The caprock permeability is increased with temperature by enhancing the minerals dissolution of caprocks. In addition, the common-ion effect generated by the increased salinity inhibits the minerals dissolution in caprock.

Impact of Exposure to Supercritical Carbon Dioxide on Reservoir Caprocks and Inter-Layers during Sequestration

“…However, the greater precipitation of Ca-smectite and the dissolution of albite in the lower part of the caprock was the opposite to what was happening to these minerals in the top of the caprock. Additionally, Ma et al [115] carried out geochemical modelling to evaluate the change in the caprock permeability due to the evolution of the mineralogy resulting from CO 2 injection, with the outcomes showing that the dissolution of feldspar and albite minerals played a major role in increasing the permeability of the seal. On the other hand, some caprocks do not contain minerals within their pore throats that are sensitive to CO 2 injection (such as carbonate), and therefore no precipitation and dissolution will occur.…”

Subsurface fluid injection and energy storage

“…The caprock sealing performance plays a key role in determining permanence and security of CO 2 geological storage. Ma et al [5] present geochemical modeling of CO 2 -brine-rock interactions in a deep saline aquifer in the Jianghan Basin, Hubei Province, China. Li and Ma [6] reported the influence of pore system change during CO 2 storage on 4D seismic interpretation, and the proposed methodology is expected to be used in China's Shengli Oilfield CO 2 -EOR project.…”