Abstract: High-Resolution Stratigraphic Framework for the Kuparuk River Formation "A" Sandstone, Kuparuk River Unit, Alaska

Gregory Wilson, Henry W. Posamentier

A detailed stratigraphic framework and a depositional systems model have been established for the Kuparuk River Formation "A" sandstone within the Kuparuk River Field using well log and core data. Six units recording regression and transgression in a southeastward offlapping pattern have been observed. Deposition in this area is interpreted to represent predominantly lowstand and transgressive systems tract deposits. Within these two systems tracts two types of depositional units are described: seaward-stepping and internally shingled regressive sandstones and mudstones deposited during progradational events, and landward-stepping, onlapping sandstones and mudstones deposited during transgressive events. The former represent lowstand and possibly some highstand systems tract depositio , whereas the latter represent healing phase deposits of the transgressive systems tract.

The geologic model is that of a beheaded or truncated wave-dominated shoreface succession with some influence by fluvial-deltaic processes. Transgressive shoreface erosion is inferred to have removed an indeterminate amount of sediment off the top of each regressive unit during subsequent transgression, removing all delta-plain/coastal plain-sediments, leaving only sediments of the lower shoreface to offshore transition. Bioturbated grit zones containing the coarsest grain size observed within the Kuparuk "A" comprise reworked transgressive lag deposits overlying transgressive surfaces. Transgressive surfaces and maximum flooding surfaces along with sequence boundaries (expressed here as correlative conformities) represent the key bounding surfaces. These surfaces serve to define basi reservoir compartments upon which field exploitation is based.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994