Investigation of Foamy Oil Phenomena in Heavy Oil Reservoirs

Abstract The so-called "Foamy Oil" phenomenon is associated with primary cold production from heavy-oil reservoirs producing under solution-gas drive. A number of heavy oil solution gas drive reservoirs show anomalously good primary performance and high oil production rates. Example are: Lindbergh, Frog Lake, Lloydminster, and Edam in Saskatchewan. The nature of gas dispersion in oil distinguishes "foamy" oil behavior from conventional heavy oil behavior. Moreover, the important issues that distinguish foamy oil from conventional heavy oil are: the amount of dispersed gas in oil, and the time for which gas bubbles remain dispersed in the oil. These reservoirs are characterized by slower decline in reservoir pressure, lower than expected GORs, higher critical gas saturation (35% to 40%), foamy produced crude oil, and higher ultimate recovery in primary production phase. Production rates from cold production wells can be many times higher than the rate predicted by Darcy equation which does not account for sand production and the "foamy" oil behavior. Several possible causes for the anomalous production behavior have been suggested by investigators. These include the formation of wormholes and cavities around the wellbore, sand dilation, enhancement of oil mobility by nucleation of large number of microbubbles, in-situ formation of oilcontinuous foam, influx of bottom water, and non-Newtonian flow. The work presented in this paper will review modeling foamy oil behavior by investigating the nucleation of microbubbles and the formation of in-situ oil-continuous foam. The study will focus on a critical evaluation of previous work performed by other investigators. A new experimental design coupled with an analytical approach were undertaken to unravel the problem forthmentioned.