Capillary management: A framework for improving CO₂ geological storage efficiency

Abstract

CO₂ geological storage in saline formations faces a persistent challenge of low storage efficiency (typically ~3%–10%), limiting effective pore space utilization. This limitation mainly arises from capillary-controlled multiphase flow, where pore-scale processes govern plume distribution and trapping. However, capillarity is commonly treated as an intrinsic rock–fluid property rather than a controllable parameter. This perspective introduces a capillary management framework that enables process-dependent control of interfacial tension and wettability to optimize both drainage and imbibition. By engineering capillary conditions, the framework enhances pore accessibility during injection and promotes residual trapping during fluid redistribution. Recent laboratory studies, together with analytical evaluation, indicate that modifying relative permeability through capillary control could potentially improve storage efficiency from ~5% to ~7%–8% under representative conditions. Analytical evaluation further indicates that these improvements result from reduced mobility ratio and enhanced saturation states. Capillary management therefore provides a new pathway for actively controlling subsurface multiphase flow and improving the performance of geological CO₂ storage.