Surface to Subsurface Correlation of the Shublik Formation: Implications for Triassic Paleoceanography and Source Rock Accumulation in Northern Alaska

Eric M. Hutton
University of Alaska Fairbanks, Department of Geology and Geophysics Fairbanks, Alaska, United States of America
[email protected]

The Middle to Late Triassic Shublik Formation in northern Alaska is the dominant source rock for Prudhoe Bay, the largest conventional hydrocarbon accumulation in North America, and is now being studied as an unconventional reservoir because of recent shale oil exploitation in North America. The Shublik Formation was deposited on a stable continental margin that deepened to the south-southwest and consists of four zones and fifteen different facies including claystones, sandstones, limestones, and phosphatic rocks. The unit is subdivided into four lithologically and geophysically distinct units (D through A) interpreted from the gamma-ray signature in the Prudhoe Bay area. This study analyzes the resource potential of the Shublik Formation by combining various data-acquisition and reservoir-characterization techniques such as outcrop spectral gamma ray, petrophysical well logs, core analysis and sedimentary petrography to correlate outcrop exposures to the subsurface.

Using thin section petrography and geochemistry the depositional features and bottom water oxygenation will be investigated to understand organic matter dilution, preservation and lateral extent. Depositional processes such as erosional surfaces and fining upward cycles indicate sediment transportation by gravity or storm driven mechanisms. These processes are tied with eustatic changes in sea level, shelf bathymetry and sedimentlogy to model the organic matter accumulation and preservation within the Shublik Formation. The cyclic nature of these events will allow a higher frequency sequence stratigrahic framework to be applied to the broader scale sequences identified in the Early to Late Triassic deposits of northern Alaska.

AAPG Search and Discovery Article #90157©2012 AAPG Foundation 2012 Grants-in-Aid Projects