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Subsurface stratigraphic picks of the Middle-Upper Triassic Shublik Formation, Alaska North Slope

May 15, 2020

The Middle-Upper Triassic Shublik Formation is the main source rock for Arctic Alaska oil and gas accumulations, including the supergiant Prudhoe Bay field. A revised stratigraphic framework recently has been developed in outcrop for the Shublik and related strata that delineates three large-scale stratigraphic units: 1) the lower clastic (LC) unit, 2) the middle carbonate-chert (MCC) unit, and 3) the upper clastic-carbonate (UCC) unit. The three stratigraphic units were interpreted to comprise five transgressive-regressive (T-R) sequences (LC1, MCC1, MCC2, MCC3, and UCC1). This outcrop-based framework has been extended to the subsurface of the Alaska North Slope using gamma-ray logs from 161 exploration wells. Subsurface stratigraphic picks of the five T-R sequences within the Shublik Formation for each well are documented herein.