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Peters, Kenneth E.1, Kenneth J. Bird1, Leslie B. Magoon1, Carolyn Lampe2, Paul G. Lillis3, Mahendra K. Verma3
(1) U.S. Geological Survey, Menlo Park, CA 
(2) Integrated Exploration Systems, Jülich, Germany 
(3) U.S. Geological Survey, Denver, CO

ABSTRACT: Modeling Petroleum Systems on the North Slope of Alaska

Our objectives were to (1) locate pods of active source rock, (2) determine critical moments when petroleum was expelled, (3) identify migration pathways, and (4) predict volumes, phases, and compositions of major accumulations within a 620 by 250 km area on the prolific North Slope of Alaska. Source rocks for four significant petroleum systems include the Mesozoic Shublik Formation, Kingak Shale, pebble shale unit, and Hue-gamma ray zone. Input for modeling using PetroMod software included maps of reconstructed hydrogen index and total organic carbon, activation energy distributions for the source rocks, and heat flow histories calibrated using vitrinite reflectance and corrected bottom hole temperatures. 
Progradation of the Cretaceous-Tertiary Brookian sequence from west (120 Ma) to east (33 Ma) resulted in western and eastern depocenters. Petroleum generation began during the Early Cretaceous in the southwest. Changing geometry resulted in a complex migration history. Deposition of Nanushuk Group-Torok Formation induced subsidence in the southwest that drove petroleum to the east. Accumulations remained on highs in the Prudhoe Bay and Simpson Peninsula areas, fed by petroleum charge from the south. Beginning about 40 Ma, subsidence in the eastern depocenter drove migrating petroleum to the west toward Prudhoe Bay. Liquid accumulations in the west degassed to form free gas phases due to uplift and pressure release. Fully PVT-controlled n-component migration modeling allowed simulation of phase behavior for all components during each time step. Phases and compositions were predicted for each major accumulation for both in situ and surface conditions and compared to known accumulations.

 

AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.