In the past air injection has found a wide application as a recovery method of heavy oil. Air injection into light oil reservoirs is a different process than heavy oil combustion. Significant increase in light oil production under air injection can be achieved with enhancement to the economics. The main agent of the process is air which can be regarded as an inexpensive and easily available. A total consumption of 5 to 10% of the remaining oil in place can be expected to maintain a propagation of the in-situ oxidation process. The flue gas and steam generated at the combustion front are stripping, swelling and heating contacted oil. The light oil is displaced at near-miscible conditions with complete utilization of injected oxygen. The process can lead to a high recovery within a relatively short period of time. The process can potentially result in all remaining oil in place being produced. The propagation of the combustion and displacement fronts in the reservoir can be sometimes uncertain. Monitoring and control of combustion front movement is important.

The potential of air injection process for an offshore field in the North Sea was evaluated. A simulation reservoir model accounting for chemical reactions, stochiometry and thermal aspects of the combustion process was used. History match simulations of the combustion tube experiments calibrated the fluid description in the simulation model. Application of air injection as primary, secondary and tertiary oil recovery process was evaluated. The simulation results showed a high efficiency of air injection if applied at a late stage of field production. Secondary air injection potential to improve oil recovery after depletion was estimated at 10% of STOOIP in comparison with secondary waterflooding, while tertiary air injection was estimated to improve waterflooding by additional 5% of STOOIP. Air injection in the light oil reservoirs at late or mature production stage will increase oil recovery at low extra cost and extend the economic life of the fields.

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