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December 4 @ 4:00 pm - 5:00 pm

Weimer Distinguished Lecture

Saturday, December 4, 2021, 4:00PM, Student Center Grand Ballroom/ Virtual

Speaker: David W. Houseknecht, United States Geological Survey

Topic: Cretaceous Renaissance in Arctic Alaska – Huge Stratigraphic Oil Accumulations Hidden in Plain Sight in a Giant Cretaceous Clinothem

Abstract: Between 1944 and 2013, more than 150 exploration wells penetrated the shallow Aptian to Cenomanian Nanushuk Formation, mostly on the way to deeper objectives in some of the most prospective areas of the Alaska North Slope. Although oil was discovered in a few Nanushuk stratigraphic and structural traps, recoverable volumes were insufficient to elevate the formation to “primary objective” status. That perspective changed abruptly when an apparent 2013 discovery (by Denver’s Armstrong Oil and Gas) defined by a 3-D seismic amplitude anomaly on the Colville River delta was followed by two significant tests of the reservoir in 2015 – a vertical well flowed 2,160 barrels of 30° API oil per day (BOPD) and a nearby 2,000 ft lateral flowed at rates as high as 4,600 BOPD, both from a Nanushuk stratigraphic trap at only ~4,100 ft depth. Three-dimensional (3-D) seismic mapping and subsequent delineation drilling confirmed the presence of an oil pool more than 40 miles long and generally less than 3 miles wide containing a 650 ft thick oil column; recoverable oil in this Pikka-Horseshoe accumulation likely exceeds one billion barrels.

Prompted by this success and following up on a 2002 “show well” 30 miles west of Pikka-Horseshoe, a 2016 discovery and subsequent delineation drilling in the National Petroleum Reserve in Alaska (NPR-A) found ~400 to 750 million barrels of recoverable oil in the Willow and West Willow stratigraphic traps. Two additional discoveries were made in Nanushuk stratigraphic traps in 2020.

The regional geologic setting of these discoveries is well understood. A giant Aptian to Cenomanian clinothem, comprising nonmarine to shallow marine topset facies of the Nanushuk Formation and moderate to deep-water foreset-bottomset facies of the Torok Formation, covers about 150,000 mi2 of the western Alaska North Slope and adjacent Beaufort and Chukchi shelves. Oil-prone source rocks and the clinothem are draped across the Barrow arch, a structural hinge between the Colville foreland basin and Beaufort Sea rifted margin.

The Nanushuk-Torok clinothem comprises sediment derived from the Chukotka (northeast Siberia) and Brooks Range orogens. Chukotkan sediment was routed longitudinally eastward in the Colville foreland basin, building east-facing shelf margins, and Brooks Range sediment was routed northward and mostly sequestered in the high-accommodation foredeep. As the foreland basin filled progressively eastward, the depositional system overstepped the relict rift shoulder to the north (near the Barrow arch) and formed north-facing shelf margins in the Beaufort Sea shelf. In the foreland basin, mainly progradational shelf margin trajectories in the west change abruptly at mid-clinothem to “sawtooth” trajectories (progradational-retrogradational-aggradational) in the east, the result of reduced sediment influx and greater marine influence. Two end-member stratigraphic trap types are recognized in lowermost Nanushuk topsets in the eastern part of the clinothem: (1) lowstand systems tracts, inferred to reflect forced regression, include a narrow, thick progradational stacking pattern perched on a sequence boundary on the upper slope; and (2) highstand progradational systems tracts include a broad, thin wedge of shingled parasequences above a toplap surface. Both trap types include sandstone reservoirs that pinch out up-dip onto sequence-bounding unconformities and seals formed by transgressive mudstone.

The extent of the Nanushuk shelf-margin stratigraphic fairway has not been defined and dozens of untested 3-D seismic anomalies suggest the potential for billions of barrels of undiscovered oil. Nanushuk stratigraphic traps lie in a favorable thermal maturity domain along multiple migration pathways across 10,000 to 20,000 mi2 onshore and both stratigraphic and structural (i.e., growth fault) traps remain untested offshore. Although a spectrum of geological, geotechnical, societal, and policy uncertainties exist, the petroleum-systems framework, recent exploration success rate, and prolific flow tests suggest significant upside potential.

Biography: Dave Houseknecht is a senior research geologist with the U.S. Geological Survey (USGS) in Reston, Virginia with a focus on basin analysis, geological controls of petroleum resource occurrence, and petroleum resource assessment. This work mainly is concentrated in Arctic Alaska and adjacent regions. He frequently represents the USGS scientific perspective on petroleum resources in the Arctic National Wildlife Refuge, National Petroleum Reserve in Alaska, other areas of Alaska, and the global Arctic to the Administration and Congress. Dave joined the USGS in 1992, serving as Energy Program Manager through 1998 and then moving to a research position. Previously, Houseknecht was a professor of geology at the University of Missouri – Columbia (1978-1992) and consultant to the oil industry, working on domestic and international projects. He received geology degrees from Penn State University (Ph.D. 1978, B.S. 1973) and Southern Illinois University (M.S. 1975).

This lecture is scheduled in a hybrid format. If you would like to join the presentation, please follow the Zoom meeting details: (capitalizations are important) bit.ly/WeimerLecture | Password: 016309

There will be a reception from 3:30-4pm and from 5-5:30pm.

Masks are required regardless of vaccination status unless actively eating meals and drinking. Lecture will be followed by an open reception to meet and visit with Dr. Houseknecht.


Berthoud Hall
1516 Illinois St.
Golden, CO 80401 United States
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