Brookian Clinoform Play Within Deepwater Torok Formation, Northeast NPRA, Alaska

M. Royhan Gani and Nahid D. Gani
Energy & Geoscience Institute, University of Utah, Salt Lake City, UT

In recent years, there has been an increased focus on oil exploration of Brookian strata in the North Slope, Alaska. Torok Formation of the Brookian strata represents a total petroleum system, hence became an immediate exploration target. Public domain data of USGS and AOGCC, including cores, well logs, and 2D seismic, were used in this study. The study identifies basic Torok facies in cores, determines reservoir quality from thin-section petrography, and shows regional depo-systems variability by correlating Torok strata in the subsurface from production to non-production wells.

Facies analysis of seven cores indicates that Torok Formation consists of four facies association: basin plain, base-of-slope, lower slope, and upper slope. Reservoir-potential facies is the amalgamated and localized deepwater sandstones occurring as both channelized and un-confined deposits in basin plain to base-of-slope setting. Basinward (southwestward) progradation of the Torok Formation is characterized by distinct clinoform packages. Shelf-slope-break trajectory, as traced in the seismic sections, reflects interplay between relative sea-level fluctuations and sediment supply, hence potentially guide the localization of sandbodies at the base-of-slope and beyond.

QFL plot shows that sandstones are mostly feldspathic litharenite, where porosity is significantly destroyed with depth by late diagenetic calcite cementation. Isopach mapping indicates that the understanding the paleobasin topography during deposition of Torok strata could be crucial in successful hydrocarbon exploration.

AAPG Search and Discovery Article #90078©2008 AAPG Annual Convention, San Antonio, Texas