Exploration and Hydrocarbon Potential of Interior Basins, Alaska

William J. Grether, Kirk A. Morgan

During the early 1980s, ARCO Alaska, Inc., conducted an extensive hydrocarbon exploration program in the Alaskan Interior. The study focused on several basinal areas: Middle Tanana, Minchumina, Holitna, Yukon Flats, and Kandik. Other basinal areas (Upper Tanana, Lower Tanana, and Yukon-Koyukuk) have been reported in the literature to have lower hydrocarbon potential and were not as extensively studied. Several geological and geophysical techniques, including gravity, aeromagnetic, and CDP seismic surveys, were used to establish sediment thickness, basin volume, morphology, and structural style. Analytical data were collected for hydrocarbon source, reservoir potential, and thermal history. Specialized structural and biostratigraphic studies were conducted in some areas.

The Middle Tanana and Kandik basins have the highest hydrocarbon potential. A 6-mi wide by 26-mi long half-graben within the Middle Tanana basin contains 20,000 ft of section. The 1984 ARCO Totek Hills 1 well penetrated 3,015 ft of Tertiary (Pliocene to Eocene) section unconformably overlying metamorphic basement. Because it was drilled on the basin flank, the well tested only the uppermost section within the half-graben. Sandstones averaged 17% porosity and 11 md permeability. Claystones containing type II kerogen showed good oil-generating potential (pyrolysis S1 + S2 values average 17 mg/g). The Kandik basin contains excellent source rocks in the Triassic Glenn Shale (S2 averaging 16 mg/g). Hydrocarbon thermal maturation changes from immature to postmature in a stepwise fashion acr ss thrust faults from southeast to northwest. Solid residue of migrated hydrocarbons occurs in formations of Devonian, Pennsylvanian, Permian, and Triassic age.

AAPG Search and Discovery Article #91030©1988 AAPG Annual Convention, Houston, Texas, 20-23 March 1988.