Design of subsurface CO₂ storage sites largely relies on numeric simulation-based predictions of plume extent and progressive immobilization. In most cases, sensitivity analyses are performed with corner-point grid representations of the geo-model and first-order IFD methods using two-point flux approximation (TPFA). Here, we have conducted a comprehensive analysis of the impact of the vertical resolution of such grids on the predicted plume extent and capacity in a simplified layered aquifer system. Four different CO₂ mobility and buoyancy scenarios were analyzed. To minimize grid-orientation effects, the analysis was performed for predominantly grid-axes parallel flow through regularly gridded cross-sectional models with uniform cell size and variable cell width-over-height ratios. The analysis of the role of vertical grid resolution indicates a first-order correlation between plume extent and this parameter. The results also reveal that capillary forces reduce plume extent and enhance aquifer storage for low permeability contrasts between layers. Furthermore, model sensitivity to grid resolution scales with the magnitude of the permeability contrast between layers. Inspection of these results reveals that an underestimation of CO₂ mobility at the top of the plume is the root cause of the observed plume retardation. A comparison with two alternative simulators that discretize mobility as piecewise linear within cells as opposed to piecewise constant and are less resolution sensitive confirms this interpretation.

地下CO ₂储存位点的设计在很大程度上取决于基于数值模拟的羽状流度和渐进固定化预测。在大多数情况下，使用两点通量逼近（TPFA），使用地理模型的角点网格表示法和一阶IFD方法进行敏感性分析。在这里，我们对这种网格的垂直分辨率对简化分层含水层系统中预测羽流范围和容量的影响进行了全面分析。四种不同的CO ₂分析了流动性和浮力情况。为了最大程度地降低网格方向的影响，主要通过规则网格化的横截面模型对网格轴平行流动进行分析，这些横截面模型具有均匀的单元尺寸和可变的单元宽高比。对垂直网格分辨率作用的分析表明，羽流程度与该参数之间存在一阶相关性。结果还表明，毛细作用力降低了羽流程度，并增强了含水层的存储能力，从而降低了层之间的渗透率。此外，模型对网格分辨率的敏感性随层之间渗透率对比的大小而定。检查这些结果表明，CO ₂的估算偏低羽流顶部的流动性是观察到的羽流滞后的根本原因。与两个替代模拟器的比较，该模拟器将流动性离散为单元内的分段线性，而不是分段常数，并且对分辨率的敏感性较低，这证实了这种解释。