Characterization of local capillary trap clusters in storage aquifers

• Published in: Energy (Oxford) 2020-02, Vol.193, p.116795, Article 116795
• Main Authors: Ren, Bo, Trevisan, Luca
• Format: Article
• Language: English
• Subjects: Aquifers; Carbon dioxide; Carbon sequestration; Cluster characterization; Clusters; Domains; Geological carbon sequestration; Geology; Heterogeneity; Horizontal orientation; Local capillary trapping; Properties (attributes); Reservoir heterogeneity; Reservoirs; Storage; Trapping; Traps
• ISSN: 0360-5442; 1873-6785
• DOI: 10.1016/j.energy.2019.116795

Local capillary trapping occurs when buoyant CO2 moves upward in a saline aquifer during geologic carbon sequestration. The volumetric capacity of local capillary traps (LCTs) is controlled by reservoir geological heterogeneity. These traps are thus intrinsic to heterogeneous storage aquifers; their volumetric capacities are however largely unknown. To address this issue, this work employs an easily calculated criterion that requires only a static geologic model to estimate the properties of LCT clusters, including size, frequency, and extent. Specifically, this work quantitatively analyzes: i) the properties of the largest LCT cluster; and ii) the impact of reservoir heterogeneity on cluster properties. The key finding of this work is that spatially-correlated reservoir heterogeneity in the horizontal direction causes the largest LCT cluster to laterally span across a given domain even when the horizontal correlation length is small (only 1/25th) compared to the domain width. The overall work sheds useful insights of the dependence of LCT clusters on reservoir heterogeneity and its implication for CO2 trapping quantification. •Systematic assessment on the effect of reservoir heterogeneity on LCT clusters.•The standard deviation and horizontal auto-correlation length of capillary entry pressure increases LCT cluster size.•Large vertical auto-correlation length compromises LCT clusters.