Foam-Assisted Air Injection in Ultralow-Temperature Tight Oil Reserviors: Experimental Study and Pilot Test

Abstract

Foam-assisted air injection is widely used for enhanced oil recovery (EOR) in reservoirs of China. However, its application to ultralow-temperature tight oil reservoirs is poorly studied. In this paper, the dynamic and static oxidation characteristics in Chang 6 tight oil reservoirs are studied experimentally. A mechanism for the physical and oxidation processes is proposed based on the experimental data. The results show that the oxidation rate increases at high pressure so that oxygen consumption increases and CO₂ production decreases. The CO₂ production rate under static oxidation conditions is 0.66% as compared with 0.31 % for dynamic conditions at a reservoir temperature of 28 °C. Foam is found to prevent oxidation although increasing pressure can diminish this effect. The oxygen concentration under dynamic oxidation conditions decreases to 10% in 3600 to 2400 hr at pressures of 4-14 MPa. Pilot tests show that the well water-cut drops from 87.13 to 66.15% whereas the daily oil production increases from 0.22 to 0.46 m³. The results confirm that foam-assisted air injection is promising for EOR in ultralow-temperature tight oil reservoirs.