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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 65 (1981)

Issue: 5. (May)

First Page: 944

Last Page: 944

Title: Characteristics of Some Oil Shale, East-Central Uinta Basin, Utah: ABSTRACT

Author(s): C. W. Keighin

Article Type: Meeting abstract


Oil-yield, lithologic, and mineral-distribution data were determined for cores taken from a 152-m drill hole in the upper part of the Parachute Creek Member of the Eocene Green River Formation. The drill hole, in Sec. 3, T12S, R24E, started just below the contact between the Uinta Formation and the underlying Green River Formation, and ended 10 m below the Mahogany oil shale bed (the richest oil shale bed in the interval examined) in the lower part of the Mahogany zone. Most of the interval studied is composed of kerogen- and carbonate-rich, very fine-grained sediments.

Several thin (less than 1 m) oil shale beds which yield as much as 25 gal of oil per ton (104.3 l per metric ton) are above the Mahogany zone, but are probably not of economic interest. The studied sequence contains several tuff beds; the maximum thickness of these beds is about 0.6 m, but the average thickness rarely exceeds 0.2 m. Two oil-saturated tuff beds occur approximately 20 m above the Mahogany oil-shale bed. Although these two tuffs are exposed in nearby surface outcrops, they do not contain oil in these outcrops. The Mahogany zone is approximately 21 m thick at the drill site; the lowermost few feet were not penetrated. The Mahogany zone is covered by 132.6 m of overburden. Fischer assays indicate that 12.9 m of oil shale within the Mahogany zone could yield at least 25 gal of oil per ton (104.3 l per metric tone) from beds at least 3 m thick.

Although analcime is a common accessory mineral in the upper 50 m of the core hole, it was not identified in the Mahogany zone. Illite and mixed-layer clay minerals occur together above the Mahogany zone. The mixed-layer clays decrease in quantity as the Mahogany zone is approached, and no mixed-layer clays are detected in the Mahogany zone. Illite was detected in all samples examined from the Mahogany zone. Examination of X-ray diffraction patterns obtained from bulk rock samples from cores did not reveal the presence of any potentially valuable accessory minerals in the stratigraphic interval studied.

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