Light-oil air injection is a well-developed technology that has broad applications in deeper, hotter reservoirs that are good gas-injection candidates. Modern air injection technology has been developing for over 30 years and has a record of decades of safe operation. The technique is practiced where the reservoir temperature is at least 75°C and gravity override can be controlled either with low-permeability or gravity stability. As in any gas injection project, it is best to operate with high reservoir pressure so as to maximize solubility of flue gas in the oil.
This is one of the conditions needed to make air or rich-air injection a practical process for heavy oil recovery. The purpose of heavy-oil in-situ combustion is to reduce the oil’s viscosity by heating the oil. However, an oil’s viscosity can be reduced by a factor of ten when gas dissolves in the oil at high-reservoir pressure. This occurs ahead of the heated zone and stops gas override that can caused early oxygen breakthrough in old, shallow, in- situ combustion projects. Performance of deep, in-situ combustion projects can also be improved when water is coinjected with the air because steam generates during combustion the reservoir and expands the low viscosity region. Thus, high-pressure in-situ combustion could have wide application for recovery of deeper or offshore heavy oils.