A critical review of ScCO₂-enhanced gas recovery and geologic storage in shale reservoirs

Carbon dioxide-enhanced shale gas recovery (CO₂-ESGR) has been identified as a promising technology for carbon emission mitigation as well as for its additional benefits regarding energy recovery. This review aims to consolidate comprehensive and contemporary findings concerning SC-CO₂ injection in shale formations. These findings indicate that CO₂ has a significantly greater adsorption capacity in shale than CH₄. Moreover, shale reservoirs possess the potential for large-scale carbon sequestration. Additionally, SC-CO₂ injection can lead to various CO₂ uptake-induced physicochemical reservoir rock alterations reflected by multimechanism–adsorption–dissolution–precipitation–transportation–wettability changes. This coupling mechanism can suppress the mechanical properties of shale, causing matrix swelling and crack sprouting, which in turn affects its storage capacity.