A review of the supercritical CO<inf>2</inf> fluid applications for improved oil and gas production and associated carbon storage

Supercritical fluids find use in various areas in oil and gas production operations due to their unique properties. Supercritical CO2 (sc-CO2) with its reduced viscosity, increased diffusivity, and liquid like density, is attractive for enhanced hydrocarbon recovery, shale gas fracturing and drilling (especially in underbalanced condition). Apart from enhanced hydrocarbon recovery CO2 injection is also desirable due to associated CO2 storage through various trapping mechanisms. CO2-EOR/EGR and storage processes are affected by coupled geochemical, petrophysical and geomechanical alterations due interaction of sc-CO2 with reservoir rock/fluids Along with diffusion/dispersion of sc-CO2 in the fluid filled pore spaces. CO2-monitoring combined with lifecycle analysis can help to ensure safety and optimize the CO2-EOR/storage project, considering the environment. However, many technical, financial and policy challenges need to be overcome to realize the success of the CO2-EOR/storage project and achieve carbon neutrality. This review paper discusses such challenges, the current mitigation practice, gaps and future direction of research. This holistic review would help gain insights into the sc-CO2-EOR/storage mechanisms, selection criteria, various limitations, mitigation and optimizations while applying the method for unconventional reservoirs with heterogeneity and varying fluid properties.