Abstract: The present invention provides a process of preparing of a gas composition suitable for the injection in an oil-containing field to increase the degree of recovery and simultaneously reduce the discharge of CO2 to the atmosphere. However, injection of a gas composition containing large amounts of oxygen will result in a degraded submarine formation which is not desirable. The present invention relates to a process for the production of a gas composition comprising N2, CO2, minor parts of NOx, VOC (volatile organic compounds) and about 0-2.0 mole % O2 from an oxygen containing exhaust gas, wherein a stream of an exhaust gas from the combustion of air and natural gas in a gas turbine containing 18% by weight O2 or less, is combusted with natural gas, whereupon the desired gas composition is discharged as a flue gas. Further, a process of recovering oil from submarine formations is also described, where said gas composition is compressed and injected into a submarine formation.