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.
Highlights
Greenhouse effect mainly due to anthropogenic CO2 emissions has caused a series of global environmental problems, CO2 emission reduction has become hot issues of general concern [1,2,3]
Based on China Shenhua CCS project, some studies have found that very small amount of CO2 will enter into the caprock from the reservoir during long-term storage process, resulting in changes in caprock permeability. They have evaluated the leakage risk with the updated Oldenburg’s Screening and Ranking Framework (SRF) [18,19,20]. These results show that the reaction of CO2–water–caprock minerals induces the mineral alteration, which affect the porosity, permeability, capillary pressure and mineral wettability of the caprock
We have developed a one-dimensional vertical model using geochemical modeling software of TOUGHREACT based on the available site-specific data in the Jianghan Basin, China
Summary
Greenhouse effect mainly due to anthropogenic CO2 emissions has caused a series of global environmental problems, CO2 emission reduction has become hot issues of general concern [1,2,3]. It is generally accepted that CO2 geological storage is the most promising method for reducing atmospheric CO2 emissions [4,5,6,7,8]. Local CO2 leakage could lead to acidification of groundwater, which seriously cause suffocation of surface creatures. It could cause the increase of CO2 concentration in atmosphere, and even lead to gas explosion [9,10,11,12]. As a barrier to prevent CO2 leakage, caprock has become the focus of research
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