A New Integrated Resource Assessment and Exploration Charge Risk Model for the North Slope of Alaska

Carolyn Lampe¹, Kenneth E. Peters², Leslie B. Magoon², and Kenneth J. Bird^2
1 IES, Integrated Exploration Systems, Ritterstr. 23, 52072 Aachen, Germany, [email protected]
² U.S. Geological Survey, 345 Middlefield Road, MS 969, Menlo Park, CA 94025, USA, [email protected]

The North Slope of Alaska, including the adjacent Beaufort Sea and Chukchi Sea, is thought to hold significant undiscovered petroleum resources. To reconstruct and assess the petroleum systems development, burial history, thermal evolution, migration, accumulation and preservation of oil and gas in the study area requires understanding and modeling of the tectonic and sedimentologic evolution through time on a regional scale. This study is based on PetroMod^® 3D compositional petroleum systems modeling.

The model is based on a regional 2D seismic grid, contour maps, and about 400 wells. It includes available geophysical, geochemical, and geological data to define the main characteristics of the identified and prospective petroleum systems in the region. Four major source rocks occur within the Paleozoic to Mesozoic Ellesmerian, Beaufortian, and Brookian Sequences, namely the Shublik Formation, Kingak Shale, pebble shale unit (PBS), and Hue Shale-gamma ray zone (GRZ), which cover most of the North Slope. The maturation and expulsion history of these source rocks depends on both the present-day and the paleo-geometry of the study area. Thus, rather than using a stratigraphic subdivision of the Brookian sequence, timelines of prograding foresets were mapped to allow for time-transgressive changes in geometry. Reconstructions of eroded overburden reach up to ~4000 m in the southwestern part of the region. The eroded section controls burial depth and thermal maturity of the source rocks and the geometry of migration pathways through time.

Understanding the basin geometry as well as the temperature, maturation and migration history through time is a prerequisite to account for the occurrence of multiple petroleum systems and their complex petroleum migration histories as depicted by the charging of multiple reservoir rocks. A three-dimensional, PVT-controlled, n-component, 3-phase petroleum migration model is presented to demonstrate the migration history and present-day petroleum distribution that resulted from the complex geometry and thermal history development of the Alaska North Slope through time.

 

AAPG Search and Discover Article #90066©2007 AAPG Hedberg Conference, The Hague, The Netherlands