Flue gas injection is becoming more attractive as a feasible and environmentally friendly process for improving oil recovery from light oil reservoirs. When obtained from surface sources, the flue gas process has an added advantage of preventing carbon dioxide (CO2), a greenhouse gas, from being disposed into the atmosphere. Flue gas can also be generated in-situ by the spontaneous ignition of oil when air, a readily available gas, is injected into high temperature, high pressure (light oil) reservoirs. The availability of flue gas and/or air and the observed high oil recovery potential make the flue gas process an economically attractive process. Oil recovery efficiency and displacement characteristics were studied in the laboratory with nitrogen and two flue gas compositions having CO2 content of 16% and 30% and two light oils obtained from two different reservoirs. The recombined light oils were displaced by the flue gases in a 2.44 m long, 5.1 cm diameter Berea sandstone core at irreducible brine saturation. The studies were conducted at reservoir pressures up to 41.58 MPa and temperatures of 80.6°C and 116°C, corresponding to the reservoir temperature of the oils studied. The experimental data was history-matched with a fully compositional simulator and the results show that oil recovery efficiency has a direct relationship to the paraffin and naphthene content of the oil. It was found during the core flood that the displacement of the oil with lower paraffin (higher naphthene) content produced more oil than the displacement with higher paraffin at one pore volume of flue gas injected, even at lower operating pressure.

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