Method and system for CO2 enhanced oil recovery

A method and system 40 of Enhanced Oil Recovery (EOR) from an oil reservoir 2 is provided. A well stream 3 from the reservoir is produced and the well stream is separated into a liquid phase 9 and a gas phase 26 with a first gas/liquid separator 16, where the gas phase comprises both carbon dioxide (CO2) gas and hydrocarbon gas. The gas phase is then cooled with a first cooler 34 and compressing using a first compressor 27 into a compressed stream 11. The compressed stream is then mixed with an external source 12 of CO2 to form an injection stream 13 and then injected into the reservoir. In alternative embodiments there is provided a second gas/liquid separator (Figure 4, 44) to separate a second gas phase from the liquid phase and where the first and second gas phases are combined prior to injection into the reservoir. In a further embodiment, part of the compressed gas phase is recycled into the well stream upstream the gas/liquid separator or into the gas phase downstream the gas/liquid separator.