Petroleum Systems of the Alaskan North Slope—A Progress Report

By

L.B. Magoon, P.G. Lillis, K.J. Bird (U.S. Geological Survey), and C. Lampe (IES, Integrated Exploration Systems)

Seven onshore North Slope petroleum systems are identified and mapped using oil-to-oil and oil-to-source rock correlations, pods of active source rock, and overburden rock packages. In mapping these systems, we assumed that: a) a source rock contains at least 2 wt. % organic carbon (TOC); b) an immature oil-prone source rock has a hydrogen index (HI) greater than 300 (mg HC/gm TOC); c) the top and bottom of the petroleum (oil plus gas) window are marked by vitrinite reflectance values of 0.6% Ro and 1.0% Ro, respectively; and d) most hydrocarbons are expelled within the petroleum window.

Three overburden rock packages determined the time of expulsion and geometry of migration paths: a) a southern package of Early Cretaceous and older rocks structurally-thickened by early Brooks Range thrusting; b) a western package of Early Cretaceous rocks that filled the western part of the foreland basin; and c) an eastern package of Late Cretaceous and Paleogene rocks that filled the eastern part of the foreland basin.

The seven petroleum systems mapped by us include: a) a southern system involving source rock in the Kuna and Otuk Formations that was active during the Late Jurassic and Early Cretaceous; b) three western systems involving source rock in the Shublik Formation, Kingak Shale, and Hue Shale that were active during the Albian; and c) three eastern systems involving the same three source rocks that were active during the Paleogene.

AAPG Search and Discovery Article #90008©2002 AAPG Pacific Section/SPE Western Region Joint Conference of Geoscientists and Petroleum Engineers, Anchorage, Alaska, May 18–23, 2002.