Heavy Oil Production By Carbon Dioxide Injection

Through the use of a carbon dioxide injection simulator, it was found that over the viscosity range of 1 to 1000 mPa x s, carbon dioxide was superior to natural depletion, inert gas injection or waterflooding, for oil viscosities above 70 mPa x s. The gain over waterflooding was as much as 9 percentiles in oil recovery, being greater for the more viscous crudes. Oil saturation was an important variable, as oil recovery decreased rapidly with a decrease in saturation. Another significant factor affecting ultimate oil recovery was the critical gas saturation. Viscous oils showed a 27% increase in recovery as the critical gas saturation varied from 0 to 10%. The blowdown recovery on curtailment of carbon dioxide injection was about 1 percentile; field values are as high as 4 percentiles. Reasons for this discrepancy are outlined. The amount of carbon dioxide left in the reservoir was used as a measure of the efficiency of the process; it was high for low oil saturations, especially for the more viscous oils. An economic analysis of the carbon dioxide injection process showed that the economics are tenuous; a variety of factors in addition to the oil price would determine the economic viabilitymore » of the process.« less