West Sak and Ugnu sands: low-gravity oil zones of the Kuparuk River area, North Slope, Alaska
Low-gravity oil in Upper Cretaceous and Tertiary shallow marine and deltaic sands of the North Slope have been known since 1969. The majority of the oil occurs in two intervals informally named the West Sak sands (Maestrichtian) and the overlying Ugnu sands Maestrichtian-Paleocene). These zones are oil-bearing primarily in the Kuparuk River and Milne Point units where they occur at depths ranging from 2000 to 4500 fr (610 to 1370 m) subsea. The West Sak consists of very fine-grained, unconsolidated sands with interbedded siltstone and mudstone that were deposited in an inner-shelf to delta-front environment. The oil in the West Sak is a less heavy to intermediate crude with gravities ranging 16/sup 0/-22/sup 0/ API. The Ugnu consists of fine to medium-grained, unconsolidated sands with interbedded siltstone, mudstone, and coal that were deposited in fluvial and delta-plain environments. The oil in the Ugnu sands is bitumen and extra heavy crude with gravities between 8/sup 0/ and 12/sup 0/ API. The total oil in place in the West Sak and Ugnu sands is estimated to be as large as 40 billion bbl. Geochemical work on these oils indicates that they have the same source as the oils in the deeper Kuparuk and Sadlerochit reservoirs but have been biodegraded.
- Research Organization:
- ARCO Alaska Inc., Anchorage
- OSTI ID:
- 5961679
- Report Number(s):
- CONF-8505215-
- Journal Information:
- Am. Assoc. Pet. Geol., Bull.; (United States), Journal Name: Am. Assoc. Pet. Geol., Bull.; (United States) Vol. 69:4; ISSN AAPGB
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
020200* -- Petroleum-- Reserves
Geology
& Exploration
ALASKA
ALASKAN NORTH SLOPE
CARBONACEOUS MATERIALS
CENOZOIC ERA
CHEMISTRY
COAL
CRETACEOUS PERIOD
ENERGY SOURCES
FEDERAL REGION X
FOSSIL FUELS
FUELS
GEOCHEMISTRY
GEOLOGIC AGES
GEOLOGIC DEPOSITS
GEOLOGIC FORMATIONS
GEOLOGY
MATERIALS
MESOZOIC ERA
MINERAL RESOURCES
NORTH AMERICA
PETROLEUM DEPOSITS
RESOURCES
ROCKS
SANDSTONES
SEDIMENTARY ROCKS
SILTSTONES
SOURCE ROCKS
TERTIARY PERIOD
USA