The Petroleum Systems of the North Slope, Alaska—a Volumetric Paradox

By

C. Cornford and R. Kelly (Integrated Geochemical Interpretation Ltd)

Sixty years of northern Alaskan exploration and thirty years of petroleum geochemistry leaves us with enigmatic petroleum system(s) evidenced by:

• Huge volumes of oil (14.4 X 10⁹ bbl) and large volumes of gas (33tcf)

• Widespread oil staining,

• Adequate maturity, but

• A distinct lack of plausible source rock.

The phrase “plausible source rock” here means a source rock of the right richness at the required levels of maturity and present in sufficient volumes and appropriately located to charge the observed super-giant accumulations.

A review of a vast data set from the Mackenzie Delta to the Chukchi Sea, and north of the Brooks Range suggests the major kitchen that sourced the North Slope fields lay over the now-inverted (and post-mature) ANWR area (Shublik Mountains). The evidence derives from trends of increasing source rock richness, burial history modelling of the thermal and hence generation history, and the timing of uplift relative to charging of the traps. A kitchen-reservoir volumetric balance also favours this model. Charges from source rock kitchens both north and south of the North Slope are considered, along with the implications for hydrocarbon prospectivity of the entire arctic torus.

The contributions of Mark Groves-Gidney, Paul Bathurst and Bob Standley to the geological underpinnings for this work, and the support of Exploration Geosciences Ltd. and their sponsors are gratefully acknowledged.

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.