--> ABSTRACT: Timing of Source-Rock Maturation Along Two Regional Transects in the National Petroleum Reserve, Alaska (NPRA), by E. L. Rowan, K. J. Bird, P. H. Nelson, and D. O. Hayba; #90906(2001)
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E.L. Rowan1, K.J. Bird1, P.H. Nelson2, D.O. Hayba3

(1) U.S. Geological Survey, Menlo Park, CA
(2) U.S.Geological Survey, Lakewood, CO
(3) U. S. Geological Survey, Reston, VA

ABSTRACT: Timing of Source-Rock Previous HitMaturationTop Along Two Regional Transects in the National Petroleum Reserve, Alaska (NPRA)

Two-dimensional burial/uplift, and thermal histories have been constructed for two regional transects as part of a new petroleum resource assessment of the NPRA by the USGS. The transects, one oriented north-south and the other east-west, were developed from reprocessed seismic reflection profiles (see Bird, Kumar, and Taylor, this volume). Each transect extends over more than 100 miles.

The evolution of thermal maturity over time was calculated for potential source rocks (Shublik Fm., Kingak Shale, Hue Shale, and Torok Fm.) based upon reconstructions of sedimentation, uplift and erosion history. Compaction curves were constructed from sonic logs in offshore wells where uplift and erosion are minimal. These curves, combined with porosity-thermal conductivity functions, were used to determine bulk rock thermal conductivities that were essential to the time-temperature and thermal maturity calculations applied throughout both transects. Confidence in the calculations is based on good agreement between measured and calculated vitrinite reflectance and bottom-hole temperatures.

Our results show that from approximately 120 - 110 Ma the distal portions of the Shublik and Kingak were thermally matured to within or beyond the petroleum window (0.6 - 1.2 Ro%). At about 60 Ma, uplift and deformation occurred within the foreland basin, resulting in shifting of depocenters northward and eastward (offshore). By this time, most of the Hue, some of the lower Torok, and the proximal portions of the Shublik and Kingak were also thermally mature. This work provides a framework for analysis of the major petroleum systems in the NPRA.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado