Simulation Study on the Migration Range of CO_(2) in the Offshore Saline Aquifer

海域盐水层CO_(2)运移范围模拟研究

The geological storage of carbon dioxide(CO_(2)) is a crucial technology for mitigating climate change. Offshore deep saline aquifers have elicited increased attention due to their remarkable potential for storing CO_(2). During long-term storage, CO_(2) migration in a deep saline aquifer needs special attention to prevent it from reaching risk points and leading to security issues. In this paper, a mechanism model is established according to the geological characteristics of saline aquifers in an offshore sedimentary basin in China. The CO_(2) migration over 100 years is simulated considering geological changes such as permeability, dip angle, thickness, and salinity. The effects of injection conditions on the CO_(2) migration range are also investigated. Results reveal that the migration range of CO_(2) in the injection period exceeds 70%, even if the postinjection period's duration is five times longer than that of the injection period. As the values of the above geological parameters increase, the migration range of CO_(2) increases, and permeability has a particularly substantial influence. Moreover, the influences of injection rate and well type are considerable. At high injection rates, CO_(2) has a greater likelihood of displacing brine in a piston-like scheme. CO_(2) injected by long horizontal wells migrates farther compared with that injected by vertical wells. In general, the plane migration range is within 3 000 m, although variations in the reservoir and injection parameters of the studied offshore saline aquifers are considered. This paper can offer references for the site selection and injection well deployment of CO_(2) saline aquifer storage. According to the studied offshore aquifers, a distance of at least 3 000 m from potential leakage points, such as spill points, active faults, and old abandoned wells, must be maintained.