Chasing the Upper Jurassic Alpine-Type Reservoir: Recent Exploration Success in the National Petroleum Reserve, Alaska

Gregory C. Wilson¹, Jerry H. Veldhuis¹, Erik Keskula¹, David B. Bannan¹, and Gregory F. Hebertson^2
1 ConocoPhillips Alaska, Inc, Anchorage, AK
² Anadarko Petroleum, The Woodlands, TX

Alaska’s North Slope has seen a resurgence of exploration activity following discovery of the 429 MMBO Alpine Field (Jurassic Kingak Formation) in 1994 and resumption of leasing in the adjacent National Petroleum Reserve – Alaska (NPR-A) in 1999. ConocoPhillips and Anadarko Petroleum, the Alpine Field co-owners, have recently been the most active explorers in the NPR-A. Together they have announced oil or gas and condensate in eight wells that have penetrated Upper Jurassic reservoirs, including four flow tests.

Much of the exploration success is a result of high-resolution 3D seismic and the recognition of reservoir facies directly from that data, with an accompanying understanding of ancestral topography at the time of transgression. Sandstone reservoirs were locally deposited during transgression of an incised surface with as much as 200 feet of erosional relief. Traps are exclusively stratigraphic. Reservoir in the two Lookout wells is interpreted to have developed in a deep but relatively narrow incision. Most of the reservoir facies in the remaining discoveries appear to have been deposited in normal marine shoreface settings in areas of modest accommodation flanking erosional topography. Reworking of proximal parts of the sandy siltstone substrate almost certainly provided some of the quartzose framework grains for the glauconitic reservoirs.

Commercial evaluation is underway and an environmental impact process has been initiated. The Lookout accumulation, for which an appraisal well tested at a stimulated rate of 4000 BOPD and 8 MMCFD of natural gas, could be the first commercial oil production from the NPR-A.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005