With over three decades of oil production, Alaska’s North Slope still provides a significant, yet declining supply of today’s US domestic oil. Although heavy oil has long been recognised in North Slope shallow sands, it has remained largely neglected in favour of the lighter, more easily produced reserves. As light oil declines, an estimated 20 billion barrels of heavy oil represents one of the largest development opportunities in Alaska for the next decade and beyond. Most of the heavy oil occurs in shallow and regionally extensive, fluvio-deltaic reservoirs of the Lower Ugnu M sands, deposited during the Late Cretaceous and Early Tertiary.

High resolution palynology has been a valuable contributor to a multi-disciplinary heavy oil appraisal programme to improve our understanding of Ugnu reservoir architecture and depositional systems (Hulm et al., 2010). Palynological analyses were undertaken on 14 cored Ugnu wells (600 samples from ~2000 ft of core) across the Kuparuk River and Milne Point Units of the central North Slope. This work revealed abundant, diverse and well preserved palynomorph assemblages which enabled the definition and detailed correlation of five regional stratal surfaces (sequence boundaries and flooding surfaces) and an eight-fold palynofacies subdivision of the reservoir succession. Regionally, Ugnu palynofacies record a broad range of environments from upper delta-plain through offshore settings, with the main reservoir intervals being developed predominantly in a lower delta-plain environment.

This work has significantly contributed to our knowledge of the size and nature of the Alaskan North Slope heavy oil resource. It has helped to influence and optimise production pilot drilling and aided selection of the most appropriate heavy oil recovery mechanisms. These activities will continue to build the foundations for exploiting the heavy oil resource and help to sustain Alaska’s petroleum production over the coming decades.

Hulm, E.J., Bernaski, G., Bridge, C., Gromek, P., Kostic, B., Lowe, S., Matson, R.G., Munn, C., Yancey. D.J., and Duncan, A. (2010). Integrated Reservoir Characterisation in Pursuit of a Heavy Oil Giant in the Arctic. Abstract. AAPG Search and Discovery Article #90108 International Convention and Exhibition, Sept 12-15, 2010 Calgary, Alberta, Canada.