Supercritical CO2 sequestration and enhanced gas recovery in tight gas reservoirs: Feasibility and factors that influence efficiency

Tight gas reservoirs always have a low natural gas recovery because of the poor reservoir properties. Effective means on achieving enhanced gas recovery (EGR) in this type of reservoir remain a challenging task. In this study, experimental investigations on supercritical carbon dioxide (SCCO2) sequestration and EGR in tight gas reservoirs were presented. Results of phase behavior testing revealed that the adsorption capacity of SCCO2 in tight sandstone is more than 50 % higher than that of natural gas in tight sandstone, and the diffusion coefficient of SCCO2 in natural gas is too low (<11.3 x 10(8) m(2) s(-1)) for two-phase mixing in reservoir formation. Along with higher density and viscosity of SCCO2, near-piston displacement can be achieved in the case of SCCO2 injection in tight gas reservoirs, and this makes SCCO2 sequestration and EGR in tight gas reservoirs feasible. Long-core experiments using natural cores from a Dong Sheng tight gas reservoir demonstrated that SCCO2 injection can achieve significant EGR (18.9 %) based on gas depletion in tight cores, and effective storage of CO2 can be achieved simultaneously. Furthermore, several sensitivity experiments were performed, and the results demonstrated that SCCO2 EGR efficiency and the CO 2 storage capacity are higher in tight gas reservoirs with lower permeability, higher water saturation, and greater dip angle.

Automated summary

The study presents experimental investigations on supercritical carbon dioxide (SCCO2) sequestration and enhanced gas recovery (EGR) in tight gas reservoirs. Results show that SCCO2 has higher adsorption capacity in tight sandstone, leading to significant EGR effects, especially in tight gas reservoirs with lower permeability, higher water saturation, and greater dip angle.