The impact of the aquifer dip angle and groundwater flow have been investigated in the field of carbon dioxide (CO) storage efficiency and security. However, no consideration has been given to the significance of the direction of groundwater flow in aquifers on the CO plume migration and the storage performance. In this study, we analyse the effect of the direction of groundwater flow on CO plume migration in the subsurface, implementing a numerical modelling approach. We compare the early plume migration in storage aquifers of various dip angles when the groundwater flows downdip with when it flows updip. We estimate the injected plume size, and the instantaneous velocity of the leading tip of the plume. When the groundwater flows downdip, against the direction of CO plume migration, the plume becomes more stretched, its greater extent and thus height causing it to accelerate during its updip migration due to the increase in buoyancy. By contrast, the plume decelerates over time when groundwater flows updip. This is because of a decrease in the size of the mobile CO plume due to enhanced residual and dissolution trapping at its trailing edge, reducing buoyancy, and hence decreasing the risk of CO leakage during its early migration.

中文翻译：

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下倾和上倾地下水流对倾斜蓄水层早期CO2运移的比较

在二氧化碳（CO）储存效率和安全领域研究了含水层倾角和地下水流量的影响。然而，没有考虑到含水层地下水流方向对二氧化碳羽流迁移和储存性能的重要性。在本研究中，我们采用数值模拟方法分析了地下水流方向对地下二氧化碳羽流迁移的影响。我们比较了地下水下倾流动和上倾流动时不同倾角蓄水层中的早期羽流运移。我们估计注入的羽流大小以及羽流前导尖端的瞬时速度。当地下水沿着与二氧化碳羽流迁移方向相反的方向下倾流动时，羽流变得更加拉伸，其范围更大，因此高度也更大，导致其在上倾迁移过程中由于浮力的增加而加速。相比之下，当地下水向上倾斜时，羽流会随着时间的推移而减速。这是因为，由于其后缘的残留和溶解捕获增强，可移动的二氧化碳羽流的尺寸减小，从而降低了浮力，从而降低了早期迁移过程中二氧化碳泄漏的风险。