Subsurface Facies Architecture and Sequence Stratigraphy of the Eileen Sandstone, Shublik Formation, and Sag River Formation, Arctic Alaska

By

E.J. Hulm (BP Sunbury)

The Upper Triassic through Lower Jurassic on Alaska’s North Slope is a critical stratigraphic interval underlying a major sequence boundary between pre-rift and syn-rift mega-sequences. This work is a subsurface analysis of the units immediately underlying this boundary to better understand the paleogeography and depositional history, depositional controls, and regional character and distribution of a major source rock unit (Shublik Formation) and minor reservoir rock intervals (Eileen sandstone and Sag River Sandstone).

 Well data from across the North Slope were utilized to describe and interpret the facies architecture, depositional setting, and

sequence stratigraphy of the Eileen sandstone, Shublik Formation, and Sag River Sandstone. The Upper Triassic was subdivided into 15 depositional facies that are interpreted to represent marginal marine and shelf depositional settings. Analysis of facies stacking patterns, resulted in the identification of four facies associations, which are interpreted to define progradational, aggradational, and retrogradational packages deposited in response to fluctuations in relative sea level. The facies associations were used in conjunction with biostratigraphic data and key surfaces to subdivide the Eileen through Sag River interval into two complete third-order depositional sequences and a partial third-order sequences.

AAPG Search and Discovery Article #90008©2002 AAPG Pacific Section/SPE Western Region Joint Conference of Geoscientists and Petroleum Engineers, Anchorage, Alaska, May 18–23, 2002.