Air Injection - Cost Effective IOR Method to Improve Oil Recovery from Depleted and Waterflooded Fields

摘要

In the past air injection has found a wide application as arnrecovery method of heavy oil. Air injection into light oilrnreservoirs is a different process than heavy oil combustion.rnSignificant increase in light oil production under air injectionrncan be achieved with enhancement to the economics. The mainrnagent of the process is air which can be regarded as anrninexpensive and easily available. A total consumption of 5 torn10% of the remaining oil in place can be expected to maintain arnpropagation of the in-situ oxidation process. The flue gas andrnsteam generated at the combustion front are stripping, swellingrnand heating contacted oil. The light oil is displaced at nearmisciblernconditions with complete utilization of injected oxygen.rnThe process can lead to a high recovery within a relativelyrnshort period of time. The process can potentially result in allrnremaining oil in place being produced. The propagation of therncombustion and displacement fronts in the reservoir can bernsometimes uncertain. Monitoring and control of combustionrnfront movement is important.rnThe potential of air injection process for an offshore field in thernNorth Sea was evaluated. A simulation reservoir modelrnaccounting for chemical reactions, stochiometry and thermalrnaspects of the combustion process was used. History matchrnsimulations of the combustion tube experiments calibrated thernfluid description in the simulation model. Application of airrninjection as primary, secondary and tertiary oil recoveryrnprocess was evaluated. The simulation results showed a highrnefficiency of air injection if applied at a late stage of fieldrnproduction. Secondary air injection potential to improve oilrnrecovery after depletion was estimated at 10% of STOOIP inrncomparison with secondary waterflooding, while tertiary airrninjection was estimated to improve waterflooding by additionalrn5% of STOOIP. Air injection in the light oil reservoirs at late orrnmature production stage will increase oil recovery at low extrarncost and extend the economic life of the fields.