This paper introduces a new method to screen crude oils for applicability of the air-injection/in-situ combustion process. Testing is performed at reservoir conditions, up to 41.4 MPa, with a specially modified accelerating-rate calorimeter (ARCTM). ARC results are shown for four medium- and high-gravity oils, combustion-tube data is presented, and air-injection field data are discussed and compared. We interpret that the continuity of the ARC trace ties in kinetics, combustion-tube, and field air-injection results. Thus, a method is available to delimit the envelope of applicability of air-injection/in-situ combustion to those oil reservoirs where the probability of technical and economic success is greatest.
Air Injection for Crude-Oil Recovery. Air injection can offer unique economic and technical opportunities for improved oil recovery in many candidate reservoirs. Air injection is an efficient oil recovery process because only a small amount of the in-place oil is consumed while the rest is displaced, banked, and eventually produced. It has often been applied to heavy oils (for viscosity reduction owing to heat release) and sometimes to light oils. In the economically advantaged class of light-oil reservoirs, potential process benefits include the following.
1. Excellent displacement efficiency and mobilization of extra, combustion oil.
2. Reservoir pressurization.
3. Flue gas stripping of the reservoir oil.
4. Oil swelling.
5. Injection-gas substitution.
For air injection into high-pressure, hot reservoirs, the following additional benefits may accrue: spontaneous oil ignition and complete oxygen utilization, operation above the critical point of water with possible superextraction benefits, and near-miscibility of the generated flue gas and the oil.