Abstract: Geochemical Classification of Oils from Chukchi Sea, Northwest Alaska

Arthur C. Banet, Jr.

Comparisons of geochemical analyses of hydrocarbons recovered from the Shell Exploration and Production Burger (OCS-Y-1413 #1) and Klondike (OCS-Y-1482 #1) wells shows that they have similar chemical compositions. Chromatograms and m/z 217 and 191 fragmentograms show that these oils are derived from marine source rocks. The oil and rock extracts have low sulfur and metal contents, with high pristane:phytane ratios and API gravities, that are similar to the Umiat Oil Type. By contrast, the ratios of rearranged:regular (S:R) steranes, the content of tricyclic terpanes and the distribution of pentacyclic terpanes are similar to those of the Prudhoe Oil Type. ¹³C isotopes and saturated alkane contents are variable.

Besides having some similarities to both the Prudhoe and Umiat oil types, the Chukchi oils have sufficient differences that indicate they are a unique Type, rather than a mixture. These hydrocarbons correlate best to the Pebble Shale Unit, the Kingak Shale, and Torok Formation, for probable sources.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994