An environmentally-friendly process for improved recovery from light oil reservoirs

The injection of flue gas is a promising cost-effective process for improving recovery from light oil reservoirs. The flue gas could be obtained directly from power plants or other surface sources. It could also be indirectly generated in situ from the spontaneous ignition of oil when air is injected into a high temperature, high pressure (light oil) reservoir. When operating at high pressures commonly found in deep light oil reservoirs, the flue gas may become miscible with the oil, thereby displacing it more efficiently. The efficiency of oil recovery during flue gas injection in light oil reservoirs was studied by flue gas displacements of light oil in a 2.44-m long Berea sandstone core at pressures up to 41.58 MPa and temperature of 116 degrees C in the laboratory. The laboratory results were history-matched using a compositional simulator. This study attempts to understand and explain the success achieved in field high pressure air injection projects in light oil reservoirs. The high oil recovery obtained from this study suggests that flue gas injection is a promising process for enhanced oil recovery from light oil reservoirs. The results show that the level of oil recovery was accompanied by the level of approach to miscibility between the flue gas and the oil. Both were found to increase with an increase in reservoir pressure, as well as an increase in the carbon dioxide content of the flue gas. When injected from a surface source, the sequestration of the carbon dioxide component of the flue gas (a greenhouse gas) makes the flue gas injection process an environmentally-friendly process.