The impact of background water flow on the early migration of a CO2 plume in a tilted aquifer during the post-injection period
- 本研究对具有水体通量的倾斜储存含CO2气泡迁移的数值建模进行了分析，考虑了CO2的残留和溶解封存。分析旨在研究水体流量速度对CO2气泡在注入后期迁移的影响，考虑了不同速度下地下水流动在含水层模型中的情况。通过估计CO2气体的分布、运移距离和速度，以及可移动CO2的范围，以确定羽流随时间传播的速度和距离。
- 研究结果表明，增加水体通量速度导致气泡向上游移动更远，随着时间推移气体的分布高度减少。在较大的背景流速下，可移动CO2体积减少，减少了CO2泄漏风险。此外，随着停止注入，CO2气泡减速、垂直上升，气泡厚度减少。随着时间延长，气泡在横向迁移的初始阶段加速，随后前沿迁移速度快于后沿，直到溶解封存足以减少自由相CO2的体积以阻止其进一步迁移。
Abstract:
The study presents a numerical modelling analysis on CO2 plume migration in a dipping storage aquifer with background flux, which incorporates residual and dissolution trapping of CO2. The purpose of this analysis is to investigate the effect of the background flow velocity on the CO2 plume migration during the early post-injection period. Different velocities of groundwater flow from low to high were considered in the aquifer model. The distribution, migration distance and velocity of the injected CO2 plume as well as the remaining mobile CO2 plume extent are estimated to determine how fast and far the plume propagates with time. Comparison of the results indicate that increasing the background flux velocity causes the plume to migrate longer distances up-dip, while it reduces the height distribution of the plume with time. This reduces the volume of mobile CO2 in the storage aquifer at larger velocities of background flux, hence decreasing the leakage risk of CO2 to the surface. In addition, the CO2 plume decelerates immediately after cessation of injection as its bottom rises vertically and the buoyancy force reduces as the thickness of the plume reduces. However, the plume then accelerates during the initial period of its subsequent lateral migration, as the plume becomes extended, and the buoyancy forces increases somewhat. The degree of lateral extension increases with increasing background water flow velocity, with the leading tip of the plume migrating faster than the trailing edge, until residual and dissolution trapping sufficiently reduce the volume of free phase CO2 that its migration is arrested.
