Dzou, Leon1, S. Cheree Stover2, Andy Pepper2
(1) BP America GoM Deepwater Exploration, Houston, TX
(2) BP Exploration and Production Technology Group, Houston, TX
ABSTRACT: Controls on Fluid Distribution in the Alaskan North Slope Petroleum Systems
The prolific North Slope petroleum province contains accumulations ranging from
undersaturated oil to dry gas, distributed among many trap types and reservoir layers.
Historically, the commercially viable product for export has been oil, which has focused
attention on understanding the distribution and quality of the major, chiefly oil-prone
source rocks: Upper Triassic Shublik, Lower Jurassic Kingak and mid-Cretaceous HRZ and
Shale Wall (Hue); a number of additional, volumetrically unimportant source rocks are
present. However, presumably reflecting the bias toward oil exploitation, most models
to-date seem to have ignored the role of the Mississippian Kekiktuk coals.
We constructed a system model which defines the location and extent of expulsion kitchens
through time for both the oil and gas-prone source systems, using an improvised
“two-and-a-half-D” approach (combining 60 calibrated 1-D models with map-based
interpolation/extrapolation); additionally, a few 2-D sections were modeled using
Temispack. Since much of the North Slope is not at maximal thermal stress at the present
day, one particularly important aspect of this work was to restore eroded overburden
carefully.
After calibration of the model against the “forensic” evidence from oil and gas
geochemistry and fluid properties, our main conclusions are: (1) it is impossible to
explain the petroleum distribution without including the Kekiktuk as a major gas source
which “competes” with Shublik, and to a lesser extent HRZ oil to determine the
composition and phase of each trap; (2) major capillary-dominated vertical migration and
leakage occurred locally; and (3) vertical up-fault migration is inconsistent with
geochemical data.
AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.