--> Hydrocarbon Potential of the Nanushuk and Torok Formations on the North Slope, Alaska: Implications for Supersized Oilfield Development

AAPG Pacific Section Convention 2019

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Hydrocarbon Potential of the Nanushuk and Torok Formations on the North Slope, Alaska: Implications for Supersized Oilfield Development

Abstract

Exploration of the Cretaceous sandstone reservoirs in the Nanushuk and Torok formations on the North Slope of Alaska is a hot topic and presents opportunities to oil and gas community because of their shallow depth, vast extent, and scope of development, etc. The consecutive discoveries of the hydrocarbon reservoirs in the Nanushuk and Torok formations by Repsol, Armstrong, and ConocoPhillips in 2015, 2016, and 2017 have only reconfirmed the presence of the vast recoverable resources present at shallow depth on the North Slope, which needs detailed geologic and geophysical characterization. The goal of the project was to characterize the Nanushuk and Torok formations integrating multiple 3D seismic surveys and well-log data. The Nanushuk Formation is expressed as topset reflections, whereas the Torok Formation is expressed as foresets and bottomsets on the seismic data. Seismic-attribute-assisted mapping revealed the presence of prograding shelf-edges, low-stand and high-stand deltas, feeder channels, and basin floor fans, all with significant amplitude anomalies. The shelf-edges continue for 10s-100s of miles. Some of these reservoirs are also bound by faults at places. The internal characters of these reservoirs delineated by well-logs show the presence of four sequences- coarsening upward, fining upward, aggradation, and transgression. Porosity and permeability values in the Nanushuk Formation range from 5% to 35% and 0.1 mD to 1,000 mD, respectively. Although the deltas are predominantly wave-dominated, there is evidence of fluvial influence.