Prudhoe Bay: New Eyes on a Mature Giant

Steve Jones¹, Jim Copen¹, Lisa Towery¹, Mark Scheihing², Ron Thompson², Sterling Helwick³, Robert Lorenzen¹, Stephen Bergbauer¹, Sholan Ramnath¹, and Jonathan L. Konkler^1
1 BP Exploration (Alaska) Inc, Anchorage, AK
² ConocoPhillips
³ ExxonMobil

Prudhoe Bay, on the North Slope of Alaska, is the largest non-heavy oilfield in North America. It is co-owned by ExxonMobil, Conoco-Phillips, and BP and throughout its 30 year production history, opinion has differed and evolved on the optimum way to operate and manage the field because of the different reservoir interpretations and models used by each of the Working Interest Owners.

In 2004, the Owners decided to jointly rebuild the fullfield model to provide a tool for guiding major development decisions during the mature phase of field life. Results will also provide a natural extension of the consensus working reservoir description developed and maintained by the Owners.

Our understanding of the reservoir and its behavior continually evolves, and our interpretation is continually refined with data from more than 2500 wells, countless well tests and production histories, and 3D seismic surveys. The structural description of Prudhoe is largely based on 3-D seismic data. New seismic 3D's, acquired in 2003 and 2004, and reprocessed 3D seismic data have significantly improved the structural image of the field.

The layering scheme in the current reservoir description consists of seven predominantly fluvial-deltiac tectono-stratigraphic sequences, consistent with the regional setting. These are subdivided by a blend of chronostratigraphic and lithostratigraphic surfaces - a pragmatic approach to integrating new interpretations with prior lessons.

Advances in computing capability and modeling software enabled higher resolution of description and fluid flow dynamics. The current description integrates some 30 years of petrophysical, sedimentological and stratigraphic reservoir characterization work into a single stratigraphic framework which forms the basis for the flow simulation model.