AUTHOR=Fu Lei , Diao Yujie , Zheng Changyuan , Ma Xin , Zhang Chenglong , Liu Ting , Jin Xiaolin , Shao Wei 

TITLE=Caprock self-sealing effect due to CO2 leakage from geologic carbon sequestration reservoirs: a case study at Ping’an, China

JOURNAL=Frontiers in Energy Research

VOLUME=Volume 10 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/energy-research/articles/10.3389/fenrg.2022.955465

DOI=10.3389/fenrg.2022.955465

ISSN=2296-598X

ABSTRACT=As a bottom technology for carbon emission reduction, geological CO2 storage has attracted great attention from geologists, but there are few reports on the research of the caprock self-sealing effect due to CO2 leakage from geologic carbon sequestration reservoirs. Ping'an is a natural CO2 leakage site, which can be compared to the leakage scenarios of geological CO2 storage. The vertical veins developed in the travertine platform confirm the existence of the self-sealing effect of the caprock. Morphological and geochemical characterizations show that the studied veins have experienced four self-sealing actions. Based on the water quality test results and geological observation data, the numerical simulation of geochemistry is carried out. The results show that: First, gypsum dissolves and calcite precipitates during the migration of CO2-rich water to the surface. This process presents a self-sealing effect, and the closer to the surface, the more obvious the self-sealing phenomenon; Second, the self-sealing effect is formed rapidly. The simulation sets the crack width to 0.3 m and the single-width flow rate to 2 L/s. It takes 390.66 days for the top to achieve self-sealing, and 814.89 days for the bottom; Third, according to the flow monitoring of the spring, the fluid gas-liquid ratio is about 0.8. It is speculated that the leakage of CO2 from a single-width crack before self-sealing is about 140813.3 m3, or about 251.28 tons.