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The AAPG/Datapages Combined Publications Database

AAPG Special Volumes


Pub. Id: A031 (1985)

First Page: 85

Last Page: 94

Book Title: SG 20: Alaska North Slope Oil-Rock Correlation Study: Analysis of North Slope Crude

Article/Chapter: Alaskan North Slope Oils and Source Rocks: BASIC SOURCE ROCK EVALUATION AND CARBON ISOTOPE

Subject Group: Geochemistry, Generation, Migration

Spec. Pub. Type: Studies in Geology

Pub. Year: 1985

Author(s): J. E. Keal, W. G. Dow


Routine geochemical techniques are used to study 15 rock samples and 9 crude oils from the North Slope of Alaska. Results indicate that the Cretaceous pebble shale unit, the Jurassic Kingak, and the Triassic Shublik formations may contain locally effective or expended oil source beds but most often contain primarily gas-generating organic matter. Organic facies variations occur within formations, and many of the rock samples have matured beyond the oil preservation limit. This makes oil-rock correlation difficult, if not impossible. Some of the oils analyzed are biodegraded, making typing and correlation even more difficult. Most oil samples, however, appear to fall into two groups: a Prudhoe Bay type, possibly related to Kingak and Shublik source beds, and an Umiat type, which may have originated in pebble shale or even Torok source beds. The Simpson oils are possibly mixtures of both basic types, and the Dalton oil may be largely but not entirely indigenous to the Lisburne limestone.

Despite the presence of thick, organic-rich, and thermally mature shales throughout the study area, oil convertibilities are very low and none of the samples analyzed represent a significant source sequence. This may explain the almost complete absence of oil production in the National Petroleum Reserve area. The source or sources of the Prudhoe Bay oil accumulation were not identified by the samples analyzed in this study.

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