Enhanced Oil Recovery with Air Injection: Effect of the Temperature Variation with Time

Abstract

Gas-based enhanced oil recovery (EOR) processes rely on the injection of gases, such as carbon dioxide, nitrogen, and natural gas, into heavy oil reservoirs to reduce native oil viscosity. Although these processes are very promising, they face the problem of limited and costly gas supply. This paper investigates the conditions, specifically of temperature variation, under which freely available air at low temperatures and low pressures and in a non-reactive environment may be used for EOR. To that end, experiments are carried out by injecting air into a lab-scale heavy oil reservoir at different pressures (0.169, 0.286, 0.403, and 0.514 MPa absolute) and temperatures in the range of 25–90 °C. Reservoirs of four different permeabilities (40, 87, 204, and 427 darcy) are used in experiments, which demonstrate heavy oil recovery of up to 58.2% original oil in place (OOIP) with constant temperature air injection. When air is injected with a periodic temperature variation between 75 and 90 °C that has an average of 78 °C, the recovery is found to increase to 69.1% OOIP. This is an improvement of 18.6% over that using constant temperature air injection at the maximum temperature of 90 °C.