Effect of Gravity on Near-Miscible CO2 Flooding

Abstract

Abstract Carbon Dioxide (CO2) injection is considered one of the most widely used enhanced oil recovery (EOR) methods due to CO2 availability, applicability. Contributing to its popularity is the ability to perform carbon capturing and storage alongside EOR in which CO2 is stored in reservoirs to mitigate global warming potential. Experiments have been performed to measure oil recovery factor, CO2 storage efficiency, and co-optimization function of a CO2 flood in horizontal cores but none has studied the effect of gravity on all three. This paper presents horizontal and vertical CO2 flooding experiments to quantify the gravity effect on oil recovery and CO2 storage. Irreducible water saturation of 27% represents the initial condition for both experiments. A homogeneous Bentheimer sandstone core is used while a mixture of hexane (65%) and decane (35%) represents the oil phase. The Oil recovery, pressure drop and effluent compositions are recorded during the experiment. It was found that vertical flood exhibited high displacement efficiency but low volumetric sweep efficiency and by eliminating the effect of gravity, not only oil recovery increases, but also CO2 storage efficiency. In the vertical flood, oil recovery, CO2 storage efficiency, and the co-optimization function increase by 24%, 7%, and 15%, respectively, compared to horizontal flood. The stabilized displacement front delays breakthrough and effectively improves oil recovery and storage efficiency.