Laboratory corefloods were performed to investigate the effects of CO2 injection rate, reservoir dip, and the use of a drive gas on the cyclic CO2 stimulation process. Experiments were conducted in 6 foot long Berea sandstone cores using Timbalier Bay, a light oil, under immiscible conditions (500 psig and 78 °F). Process performance was maximized at moderate injection rates. Oil recovery efficiencies and gas utilization factors were poorer at very high or low injection rates. The inclination of the core and the site of injection substantially influenced oil recovery efficiencies and gas utilization factors. Process performance was favored when CO2 was injected into the lower end of a core tilted at a 45 or 90 degree angle. The use of a horizontal core or injection into the top of a tilted core yielded a poorer response. The benefits of a nitrogen drive (or chase) gas were evaluated by comparing the results of injecting CO2 followed by nitrogen with injection of CO2 or nitrogen alone. First cycle injection of a certain mass of CO2 followed by nitrogen yielded over twice as much oil as injection of that mass of CO2 alone. In the second injection cycle, the drive gas experiment recovered over three times as much oil as recovered by CO2 alone.

This paper pr.sents r.sults of an experimental and numerical inv••tigation of the CO:z huff ' n' puff proc.s. for the enhanced

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