Sequence Stratigraphic Analysis of the Alaska North Slope: from Integrated Approach in Defining Petroleum Prospectivity

Mark B. Redden, Andrew Davies, James Etienne, Mike Simmons, and Peter Sharland
Neftex Petroleum Consultants, Abingdon, United Kingdom.

The North Slope of Alaska is a critical area for future hydrocarbon exploration, not only for the United States but the Arctic region as a whole. A recent appraisal estimates that the Alaskan North Slope contains undiscovered recoverable reserves of 72.7 billion barrels of oil and oil-equivalent natural gas [1].

To improve regional understanding and to glean new insights into the petroleum system and key play elements of the region, we have conducted an analysis of available public domain data from the National Petroleum Reserve, Alaska (NPRA). The data-set comprises a 2D seismic survey of twenty-two lines, supported by fourteen well logs. Within this data-set key biostratigraphically constrained sequence stratigraphic surfaces were identified, allowing a detailed regional chronostratigraphic framework to be developed. In total, thirty-three sequences were identified from the Mississippian through to the Late Cretaceous.

Using the sequence stratigraphic framework a regional chronostratigraphic chart was constructed and used to illustrate the basin evolution and outline changes in sedimentation patterns through time, in order to better understand the large-scale changes in lithofacies across the NPRA. Furthermore this detailed framework facilitates discussions on the relative effects of tectonics and eustasy on sedimentation and the development of gross depositional architectures, not just in Alaska, but the Arctic as a whole. Gross depositional environment maps were also constructed for key stratigraphic surfaces important for generating play elements.

The development of the main source rock intervals and potential reservoir horizons will be outlined using this regional sequence stratigraphic framework. The implications for petroleum prospectivity will be discussed and placed into a wider circum-Arctic context.

[1] Bird, K.J. et al., 2008, Circum-Arctic resource appraisal; estimates of undiscovered oil and gas north of the Arctic Circle, USGS Fact Sheet, 2008-3049, 4 pp.

AAPG Search and Discover Article #90096©2009 AAPG 3-P Arctic Conference and Exhibition, Moscow, Russia