Reservoir heterogeneity and its role in long-term CO₂ storage performance: A case study of Air Benakat formation

Indonesia’s strategy for attaining net-zero emissions by 2050 is contingent upon carbon capture and storage (CCS). The long-term CO₂ storage performance of Air Benakat formation in the South Sumatra Basin was assessed in this study, with a particular emphasis on the influence of reservoir heterogeneity. We compared the behavior of CO₂ (trapping mechanisms and migration) under homogeneous and heterogeneous conditions by utilizing reservoir modeling. Sequential Gaussian simulation (SGS) was implemented to represent spatial variability in porosity and permeability. Increased degrees of heterogeneity are quantified by Lorenz coefficients of permeability ( Lk ) of 0.0, 0.2, 0.4, and 0.6. The simulation results over a 1000-year period indicate that pressure accumulation during the 30-year injection phase is reduced, and pressure dissipation is enhanced post-injection as a consequence of increased heterogeneity. The distribution of permeability substantially impacts the trapping mechanisms for CO₂, including free-phase (supercritical), residual (trapped), and dissolved. Heterogeneous models exhibit greater long-term dissolution as a result of flow redistribution, whereas homogeneous models retain a larger amount of free-phase and trapped CO₂. Moreover, the consequences of heterogeneity are further illustrated by plume migration patterns. With the increase in Lk values, lateral migration becomes more asymmetric and fragmented, and the plume area expands by up to 23.4 % in comparison to the homogeneous case. Heterogeneity redirects CO₂ into additional strata without altering the maximal height, as evidenced by vertical plume analysis, with occupancy differences reaching up to 9.2 %. Overall, results highlight that ignoring heterogeneity leads to overestimations in CO₂ storage efficiency, particularly in trapped CO 2 capacity. • Permeability heterogeneity reduces CO₂ injection pressure by 3.7 %. • Heterogeneity enhances CO₂ dissolution trapping by 72 % over 1 000 years. • Plume footprint expands by 23.4 % under increased formation heterogeneity. • CO₂ migration extends into additional strata, altering plume occupancy.