Subsurface Indications of Oil and Gas in the National Petroleum Reserve, Alaska

By

D.O. Hayba, K.J. Bird, and C. Garrity (U.S. Geological Survey)

To better understand the distribution of hydrocarbons within the National Petroleum Reserve, Alaska, we compiled over 4000 records from public data on oil and gas shows from 70 wells in and near NPRA. For most wells, we extracted data directly from lithologic and mud logs, formation tests, and other reports; data from the early wells (1944–1953) are more limited. We distinguished among a wide range of oil show types including evidence for 1) mobile oil—from drill stem tests or ‘bleeding’ core, 2) staining, 3) fluorescence or visual cut, and 4) dead oil. For gas, the categories include 1) mobile gas, 2) gas show, 3) C2 concentrations >2,000 ppm, and 4) C1 >20,000 ppm. We plotted the depth distribution and type of shows for each well and combined these to create a series of cross-sections. We also mapped the distribution of shows for 15 formations. Within the Ellesmerian sequence, strong oil and gas shows are found only along the Barrow arch and the strength of the shows deceases rapidly southward. Beaufortian rocks show a similar trend with the strongest shows limited to the Point Barrow area. Shows in the Brookian section exhibit significantly different patterns. The strongest oil shows are largely along the eastern margin of NPRA, decreasing to the west. However, strong shows are also present near Point Simpson and Point Barrow. Gas shows within the Brookian are abundant in the central and southern portions of NPRA with moderate shows found in the north.

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.