Timing of Hydrocarbon Generation in the National
Petroleum Reserve-Alaska (NPRA) from Burial and Thermal History Modeling
By
W.M. Burns, D.O. Hayba, D.W. Houseknecht, and E.L. Rowan (U.S. Geological Survey)
Burial/thermal history modeling
was performed for
Ellesmerian, Beaufortian, and Brookian sequences in the National Petroleum
Reserve-Alaska (NPRA) to determine the timing of hydrocarbon generation from
source rocks within these sequences. One-dimensional and two-dimensional models
were calibrated with vitrinite reflectance, compaction, and surface and
bottom-hole temperature measurements made at wells. These parameters were
interpolated for use at ‘psuedo-wells’ derived from
seismic
sections, greatly
expanding the modeled region. Geochemical data for potential hydrocarbon source
rocks were combined with the modeled thermal histories to derive histories of
hydrocarbon generation. Source rocks modeled include the Triassic Shublik
Formation, shales in the lower portion of the Jurassic Kingak Shale, and the
Cretaceous gamma ray zone. Results were compiled in maps of the NPRA for
multiple time slices.
Timing of hydrocarbon generation in the NPRA
correlates with deposition of the Cretaceous to Tertiary Brookian sequence.
Northeastward progradation of the Brookian shelf margin was delineated
previously by sequence stratigraphic analysis of the Torok and Nanushuk
Formations (Albian to Cenomanian) in seismic
reflection data spanning the NPRA.
The models indicate that hydrocarbon generation was largely driven by prograding
deposition, initiating in the southwest during the Albian and progressing
northeastward across most of the NPRA during the Albian and Cenomanian. In the
northeastern part of the NPRA, initiation of hydrocarbon generation was delayed
until deposition of Turonian to Maastrichtian Brookian strata. Northward
thinning of the Brookian sequence onto the Barrow arch limited the degree of
thermal maturation and led to incomplete hydrocarbon generation on and adjacent
to the arch.
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.