Oil recovery is a term involves methods used for increasing the amount of crude oil that can be extracted from a petroleum reservoir.Recovery methods are classified as primary, secondary and tertiary.
Carbon dioxide ( CO2) flooding is a tertiary oil recovery method in which carbon dioxide is injected into an oil reservoir in order to increase the output while extracting crude oil.Injecting carbon dioxide into the pore spaces of a rock help move crude oil out as it has two characteristics that make it suitable for oil recovery: it is miscible with crude oiland less expensive than other miscible fluids.
Flooding a reservoir with CO2 can occur either miscibly or immiscibly.
field, and a meter measures the volumes of the gas purchased.
CO2 is injectedat its MMP or above into the reservoir using injection wells to free the trapped oil.
CO2 enters the reservoir, moves through the pore spaces of the rock and mixes with the crude oil miscibly reducing the viscosity of the trapped oil so that it flows more easily.
Water is injected in alternating cycles with CO2 to sweep the oil to the producing wells; the water may mix with the oil causing the recovered liquid to become mostly water which had to be separated from the oil.
Production wells pump the oil, CO2, produced water and any natural gas to the surface.
The CO2 and associated natural gas are separated, and then CO2 is recompressed for reinjection with additional newly-purchased amounts.
CO2 Flooding is consideredto be the greenest way to recover oil as carbon dioxide frees the oil easily and affordably.After the oil has been recovered, the CO2 is trapped in the reservoirin a solution called "carbon capture and sequestration."
The high mobility of CO2 is a main problem in CO2 flooding. Also, the relative low density and viscosity of CO2 compared to reservoir oil causes gravity tonguing and viscous fingering – the interface of the two fluids does not remain flat but the less viscous fluid moves faster than the more viscous one deforming the interface and making fingered profile