An immiscible CO2 slug and carbonated chase water enhanced oilrecovery process is being investigated at the shallow, light oil Salt Creek Field in Natrona County, Wyoming. This 100-year-old giant has had variousimproved recovery techniques, whose residual effects impact future tertiarypotential. Salt Creek currently produces over 10 HBOPD (1590 m3/d)with a cumulative recovery of about 630 MMBO (1.00 × 108m3).
In an immiscible CO2 process, part of the injected CO2 isabsorbed into the reservoir fluids while some of the CO2 forms afree gas phase in the reservoir. Tertiary recovery of the light crude underthis process is sensitive to the reservoir crude composition, temperature andpressure.
Gravity drainage, gas cycling, and localized excess NGL product injection havecaused significant areal variations in the intermediate hydrocarbon compositionin Salt Creek's major producing zone, the Second Wall Creek (WC2). Structuralrelief of 1,500 feet (457 m) and 33 years of variable temperature waterfloodinghave likewise caused reservoir temperature variations. Finally, althoughwaterflooding has restored the pressure depleted reservoir to near originalconditions, it has caused local pressures to vary, not only with structure, butalso with nearby injection and production bottom hole pressures.
In general, light oil recovery improves under an immiscible CO2process as reservoir pressure increases, reservoir temperature decreases, orthe percentage of intermediates in the oil increases. Thus cooler injectedwater increased reservoir pressure, and high grading of process areas based oncrude composition should improve tertiary performance in the Second WallCreek.
A 17.8-acre (7.20 ha) immiscible CO2 pilot has been designed and isexpected to be initiated in the 1990s. If the: pilot is successful, implementing this tertiary process should improve field recovery and extendfield life.
Salt Creek Field is located in northeastern Natrona County, Wyoming, about 40miles (64 km) north of the city of Casper. Oil at Salt Creek is produced fromtwo distinct domes on a 20 mile (32 km) long anticline. The smaller, southernstructure is best known as Teapot Dome while the larger, northern dome is SaltCreek Field.1 Figure 1 shows the location of the field, a type logand the structural contours of the Second Wall Creek sandstone. Eleven horizonshave been productive at various times in the field's history (see Table 1).Figure 2 summarizes 100 years of all production history for the entire SaltCreek Field.
In 1884 Aughey reported2 oil in the Salt Creek area when he found anoil spring in the bed of Salt Creek - an intermittent stream running throughthe Salt Creek Dome.3 The Salt Creek Field discovery well wasdrilled in late 1889 by P. M. Shannon of the Pennsylvanian Oil and Gas Company, and completed at a rate of 4 BOPD (0.6 m3/d) in the Shannonsandstone.4 This well was located about 1 ¼ miles (2.0 km) north ofthe present day boundary of the Salt Creek Unit (see figure 1).
