How to Co-optimize Oil Recovery and CO2 Storage during CO2 EOR - A Laboratory Study

Abstract

This paper presents experimental observations that delineate co-optimisation of CO2 EOR and CO2 storage. Supercritical CO2 was injected into a homogeneous Bentheimer sandstone sample under various miscibility conditions. A two-component hydrocarbon system (65% hexane and 35% decane) was used to represent the oil phase. Three experiments were run at the same temperature (70oC) but different pressures (1,300, 1,700 and 2,100 psi). These pressures were determined using a PCT simulator before the experiments in order to obtain immiscible, near miscible and miscible conditions. Oil recovery and CO2 saturation were recorded during experiments. A co-optimisation function is defined and was calculated using the measured data for each experiment. Experimental observations demonstrate that oil recovery during miscible and near miscible displacement is almost the same while it is 20% less in the immiscible displacement. We note that heavier hydrocarbons produced from miscible and near miscible displacements are much higher than the immiscible displacement. On the other hand, CO2 is stored in the rock sample more efficiently during the near miscible displacement. The co-optimisation function also suggests that the near miscible displacement offers the best performance for coupling CO2 EOR and storage.