Displacement efficiency and storage characteristics of CO in low permeability reservoirs: An experimental work

Abstract

Over the past decades, CO 2 flooding in low-permeability porous media has continued to grow. Furthermore, propelled by the current movement toward CO 2 sequestration, the flooding of CO 2 is expected to further increase. Thus, it is of scientific significance to study the mechanism of displacement of CO 2 flooding as well as the CO 2 storage characteristics. In this study, CO 2 miscible/immiscible flooding experiments were conducted on two low permeability samples to study the difference between them. Specifically, the effect of oil displacement and CO 2 storage coefficient for different displacement models were measured and compared. In addition, nuclear magnetic resonance (NMR) tests and frozen pelleting experiments were conducted. The NMR tests clarified the lower limit of pore throat where oil can be displaced by CO 2 miscible/immiscible flooding. Furthermore, the frozen pelleting experiments analyzed the distribution characteristics of the remaining oil before and after CO 2 miscible/immiscible flooding. The investigation showed that the development efficiency of CO 2 miscible flooding is higher than CO 2 immiscible flooding in low permeability reservoirs. The results also indicated that CO 2 miscible flooding increases the recovery of hard-to-produce semi-bound oil phase and CO 2 storage coefficient with CO 2 miscible displacement is more significant than that with CO 2 immiscible flooding. The data from this study is a critical input for reservoir simulation, which sheds light on the CO 2 miscible/immiscible flooding in low permeability reservoirs.