ABSTRACT
The Almy sands in Sublette County, Wyoming have some 19 years of volumetric sweep improvement history. In an effort to reduce residual oil saturation in the swept area, the first field-wide alkaline flood was initiated in September, 1980 at the Isenhour Unit.
Based on core testing, crude oil-alkaline agent screening determined that soda ash (Na2C03) and anionic polymer would be most beneficial in reducing interfacial tension (IFT) and mobilizing residual oil. Core flooding indicated that alkaline agent could be injected into the high clay content Almy sand. A significant decrease in oil saturation on a percent pore volume basis was predicted.
This paper details flood performance up to January 1, 1988. Injection is now 67.2% of the total pore volume. A cationic and anionic polyacrylamide spearhead preceded the addition of the alkaline agent. Anionic polyacrylamide followed for mobility control. The program utilized a tripolyphosphate-anionic polymer blend for long-term wettability control and alkaline slug stability. Fresh water injection continues this date. Recovery to-date is 26.4% of the 00IP. Oil production inclined at a rate of 20% per year since the start of the polymer augmented alkaline flood to 1985. Oil production then declined at approximately 35% per year until mid-1987 with the drilling of #15 for the southwestern expansion of the reservoir.
