Filling History of the Kuparuk Field Reservoir, Alaskan North Slope: Results of an Integrated Petroleum Systems Approach

By

L. Dzou and A. Pepper (BP Upstream Technology Group)

Kuparuk is a giant oilfield located on the Colville-Prudhoe High, west of the Prudhoe Bay Field, in the Alaskan Arctic plain. Bulk and molecular geochemical characteristics of the high molecular weight fraction of the Kuparuk oils suggests derivation from a single source rock: the Triassic Shublik Formation.We revisited the geochemistry of the Kuparuk field within the context of a regional evaluation of North Slope petroleum systems. We paid particular attention to the compositional filling history, phase behavior and interpretation of solution gas—rather than just the oil—geochemistry. Integration of these additional data constrain the possible interpretations of the oil geochemistry, as follows: (1) Kuparuk oil is under-saturated by 200 psi at current reservoir conditions (2) charge GORs were lower during the earlier charge history; (3) gas isotope data show that part of the Kuparuk solution gas is lignin-derived. These interpretations are consistent with the results of a proprietary light hydrocarbon classification scheme, which in contrast to Thompson’s scheme places emphasis on source rock organofacies than rather than maturity or phase segregation. Using Thompson’s (1987) light hydrocarbon scheme in isolation, one would interpret Kuparuk as the residue from repeated episodes of phase segregation and gas-cap leakage. Our integrated study suggests a very simple charge / filling model, in which the Kuparuk reservoir has remained single phase throughout. Lipid-derived oil and solution gas from the Shublik, together with lignin-derived gas and naphthenic-aromatic condensate from Kekiktuk coals shared a common migration path into Kuparuk.

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.