CO_(2)enhanced oil recovery plays an important role in carbon storage and utilization.However,the incomplete understanding of the underlying microscopic convection–diffusion mechanisms in complex pore structures has ...CO_(2)enhanced oil recovery plays an important role in carbon storage and utilization.However,the incomplete understanding of the underlying microscopic convection–diffusion mechanisms in complex pore structures has constrained the broader industrial application of CO_(2)geo-sequestration.This work develops a pore-scale numerical model considering molecular convection–diffusion to investigate CO_(2)-oil miscible displacement in two-and three-dimensional porous structures of conglomerate rocks.The effects of CO_(2)injection rates and pore structure properties on convection–diffusion are analyzed.By reconstructing the distribution of unexploited pores,the CO_(2)sweep efficiency is quantitatively evaluated.Furthermore,a sequestration factor is proposed to evaluate the CO_(2)storage capacity during miscible displacement.Convection significantly enhances the CO_(2)mass fraction in fractures with high flow rates.Subsequently,CO_(2)gradually diffuses into matrix pores without velocity distribution.Both convection and diffusion contribute to improving CO_(2)displacement efficiency.Diffusion facilitates the dissolution of CO_(2)into oil within small-diameter pores,and convection effectively mobilizes oil in large pore bodies.Developed and homogeneous pore structures enhance CO_(2)displacement efficiency,whereas CO_(2)flows along the main flow channels in heterogeneous pore structures,resulting in lower displacement efficiency.Diffusion plays a crucial role in CO_(2)storage within porous media.At low injection rates,dissolved CO_(2)is trapped in poorly connected and blind-end pores.The injection rate is negatively correlated with the sequestration factor.展开更多
基金supported by National Natural Science Foundation of China(42172159,52404048)China Postdoctoral Science Foundation(2023M743870)+1 种基金Postdoctoral Fellowship Program of CPSF(GZB20230864)Frontier Interdisciplinary Exploration Research Program of China University of Petroleum,Beijing(2462024XKQY002).
文摘CO_(2)enhanced oil recovery plays an important role in carbon storage and utilization.However,the incomplete understanding of the underlying microscopic convection–diffusion mechanisms in complex pore structures has constrained the broader industrial application of CO_(2)geo-sequestration.This work develops a pore-scale numerical model considering molecular convection–diffusion to investigate CO_(2)-oil miscible displacement in two-and three-dimensional porous structures of conglomerate rocks.The effects of CO_(2)injection rates and pore structure properties on convection–diffusion are analyzed.By reconstructing the distribution of unexploited pores,the CO_(2)sweep efficiency is quantitatively evaluated.Furthermore,a sequestration factor is proposed to evaluate the CO_(2)storage capacity during miscible displacement.Convection significantly enhances the CO_(2)mass fraction in fractures with high flow rates.Subsequently,CO_(2)gradually diffuses into matrix pores without velocity distribution.Both convection and diffusion contribute to improving CO_(2)displacement efficiency.Diffusion facilitates the dissolution of CO_(2)into oil within small-diameter pores,and convection effectively mobilizes oil in large pore bodies.Developed and homogeneous pore structures enhance CO_(2)displacement efficiency,whereas CO_(2)flows along the main flow channels in heterogeneous pore structures,resulting in lower displacement efficiency.Diffusion plays a crucial role in CO_(2)storage within porous media.At low injection rates,dissolved CO_(2)is trapped in poorly connected and blind-end pores.The injection rate is negatively correlated with the sequestration factor.
