Analysis of the Migration of Carbon Dioxide in Deep Saline Fractured Aquifer

Abstract

In order to control greenhouse gases and protect the environment, carbon dioxide emission reduction has become a global research hotspot. Fractures in the deep saline aquifer enhance the heterogeneity of the aquifer, and have an important effect on CO2 migration, thus the detailed description and characterization of fractures in geological structure are very important. Existing research on the impact of fractures on CO2 migration, however, ignores the role that the fractures' characteristics play in this process. This work aims at addressing this gap. Based on the embedded discrete fractured model (EDFM), we quantified the role of the fractures in the mechanism of CO2 migration and studied the length, aperture, and orientation of the fractures. It is found that the CO2 plume takes the fracture as its preferred channel and changes the migration direction. The longer the fracture length and wider the fracture aperture, the faster the CO2 migration rate is. The change in fracture orientation mainly affects the migration direction of the CO2 plume. Due to the different angles of the plume entering the fracture, the influences on the CO2 migration rate are also different. When the orientation is 45°, the CO2 migration rate is the fastest, while it is the slowest at 135°. When there is a complex fracture network in the aquifer, the heterogeneity of the aquifer is enhanced. Compared with the non-fractured aquifer, the direction and rate of CO2 migration are greatly changed, and the instability of CO2 sequestration is increased.