Regional High-Resolution Biosequence Stratigraphy, Kuparuk Sandstone and Associated Strata, Central North Slope, Alaska

Robert L. Ravn and David K. Goodman
IRF Group, Anchorage, AK

The Kuparuk Sandstone forms the reservoir unit at the giant Kuparuk Oil Field and several smaller producing fields on the Alaska North Slope, and continues to be an important exploration target as well. The sands and coeval shales comprise a complex deposit ranging from Valanginian to Barremian (Early Cretaceous) in age, subdivided into two major units bounded by the regional Lower Cretaceous Unconformity (LCU), Each of these informally designated member units consists of individual disconformable sand and shale bodies of locally variable character that affect reservoir characteristics in complicated ways relating to paleoenvironment, syndepositional local tectonism and sediment provenance. Detailed palynostratigraphic analyses, using whole-population statistical techniques, reveal a consistent series of “event signatures” through the Kuparuk interval and associated strata the recognition of which can be important for both exploration and development strategies.

The complexity of the individual episodes of sediment deposition characterizing this interval is most clearly revealed through regional reconstruction and comparison of the most complete stratal packages from field to field across the North Slope area.