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Joint Meeting Pacific Section, AAPG & Cordilleran Section GSA April 29–May 1, 2005, San José, California

Bristol Bay, Frontier Basin, Alaska Peninsula: Hydrocarbon Resources, Petroleum Reservoir Characterization, and Source Potential

Rocky R. Reifenstuhl and Emily S. Finzel
Energy Section, Alaska Div of Geol & Geophysical Surveys, 3354 College Road, Fairbanks, AK 99709-3707, [email protected]

More than 20 wells have been drilled on the Alaska Peninsula; most reported oil and gas shows, but none has produced. A three-year collaboration between the Alaska Division of Geological & Geophysical Surveys, the Alaska Division of Oil and Gas, the University of Alaska Fairbanks, the Bristol Bay Native Corporation, and the Alaska Energy Technology Development Laboratory has been established with the goal of reassessing this frontier basin. State lease sales are scheduled for 2005.

New outcrop data (2004) addressing hydrocarbon resource estimates encompassing state-owned onshore and three-mile-limit waters of Bristol Bay basin and Alaska Peninsula suggest reserves of 300–500 million barrels oil and 3–5 TCF gas. Unconventional gas resource evaluation (coalbed methane) awaits high-pressure gas adsorption.

Federal offshore waters reserve estimates are 230 million barrels of oil and natural gas liquids, and 6.8 TCF gas (mean values: U.S. Minerals Management Service report, Sherwood, 2000).

Oil seeps (½ BOPD, API ~18) from the Jurassic Shelikof Formation, and the associated gas seep at Oil Creek is 91% methane, 7% nitrogen, and 2% carbon dioxide. Kamishak Formation (Triassic; shallow-water biohermal limestone) yields TOC to 2.4%; HI of 598 and 474, and OI averaging 21.5. Porosity and permeability for the Tertiary age presumptive reservoir rock, Miocene Bear Lake and Pliocene Milky River Formations, range from 5 to 35 percent porosity and 0.009 to 500 milidarcies permeability, respectively. The lower part of the Upper Jurassic Naknek Formation locally yields good porosity and permeability, 2 to 8 percent and 0.005 to 300 milidarcies. Other important hydrocarbon-related notes are that lower Naknek Formation has tens of meters of section that contain dead oil; the Miocene Bear Lake Formation contains hundreds of meters of reservoir-quality sandstone in marginal marine, fluvial, and estuarine depositional environments; the gas seep at the Port Moller hot springs is 98% biogenic-origin methane; and numerous coals in the Miocene, Oligocene, and Upper Cretaceous units are possible gas sources for biogenic gas in the subsurface basin.

Posted with permission of The Geological Society of America; abstract also online (http://gsa.confex.com/gsa/2005CD/finalprogram/abstract_85693.htm). © Copyright 2005 The Geological Society of America (GSA).