Investigation of Low-Density CO2 Injection for Enhanced Oil Recovery

Abstract

The density of the CO2-rich phase in a reservoir would play a crucial role in the performance of an enahcned oil recovery (EOR) scheme. Many oil reservoirs are located in deep formations; hence, they have high temperatures. Moreover, the pressure of reservoirs decreases because of natural depletion. Under the conditions of those reservoirs, CO2 would be a low-density gas. A series of coreflood experiments were performed to evaluate the potential of low-density CO2 EOR. The experiments are intermittent CO2 injection, continuous tertiary and secondary CO2 injection, and water alternating CO2 injection followed by the coinjection of a surfactant and CO2. The same oil and gas were mixed to prepare live oil for all the experiments. The initial rate of oil recovery during secondary waterflood was high, but the efficiency of the process decreased after the breakthrough. Three pore volumes (PVs) of secondary CO2 injection resulted in the recovery of around 50% of the initial oil in place, which was 27% higher tha...