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CO2 Enhanced Oil Recovery: Background

With 50% to 65% of the original oil in place (OOIP) remaining in many reservoirs after primary and secondary recovery, more operators and governments are considering the use of enhanced oil recovery (EOR) processes as an opportunity whose time has come. Additionally, in the face of global warming, the prospect of CO2 sequestration has arisen with the potential of sequestering large quantities of CO2 in depleted oil fields as a means of preventing its release into the atmosphere.

The concept of injecting gas into a formation to stimulate recovery of residual oil is not new. Successful laboratory gas-injection experiments generated a lot of optimism in the 1950s, but by the 1970s field experiments yielded only moderate recoveries of 5% to 10% of the remaining OOIP. Viscous fingering, solvent channeling, and reservoir heterogeneity were found to be the main culprits for the disappointing field performance. Early efforts were directed at developing methods to “improve” the injected gas’s mobility and volumetric sweep efficiency, and included the water-alternating-gas (WAG) process, using foaming agents and polymers. Much of these research efforts continue today in universities and other research laboratories. One concern, however, is that the research favors modeling work rather than experimental development of new concepts and processes.

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