Characteristics and description of cores from the USGS core hole CRU-1, Parachute Creek Member, Green River Formation, east-central Uinta Basin, Utah

Oil-yield, lithologic, and mineral distribution data were determined for cores taken from a 497.7-foot drill hole in the upper part of the Parachute Creek Member of the Eocene Green River Formation. The drill hole, 1050 feet FEL, 700 feet FNL, sec. 3, T. 12 S., R. 24 E., Uintah County, Utah, started slightly below the contact between the Uinta Formation, also of Eocene age, and the underlying Green River Formation. It ended 32 feet below the base of the Mahogany bed (the richest oil-shale bed between A groove and B groove--which define the upper and lower boundaries, respectively, of the Mahogany zone). Most of the interval studied is kerogen- or carbonate-rich, commonly tuffaceous, and is very fine grained.

Several thin (<3 feet) oil-shale beds which yield as much as 25 gallons of oil per ton occur above the Mahogany zone, but are probably not of economic interest. The cored sequence contains several tuff beds. The thickest of these beds is approximately 2 feet thick; the average thickness is rarely greater than 0.5 feet. Two oil-saturated tuff beds occur approximately 65 feet above the Mahogany oil-shale bed. Although these two tuffs are exposed on nearby surface outcrops, no evidence of oil is seen on outcrop. The Mahogany zone is approximately 69 feet thick at the drill site; the lowermost few feet were not penetrated. At the site cored, the Mahogany zone is overlain by 435 feet of overburden. Fischer assays indicate that 42.3 feet of oil shale within the Mahogany zone could yield at least 25 gallons of oil per ton from beds at least 10 feet thick.