William R. Morris1,
Douglas S. Hastings2,
Steve R. Moothart2,
Kenneth P. Helmold2,
Micheal J. Faust2
(1) Arco Alaska, Anchorage, AK
(2) Arco Alaska
Abstract: Sequence Stratigraphic Development and Depositional Framework of Deep Water Slope Apron Systems, Tarn Reservoir, North Slope, Alaska
The Cenomanian Tarn reservoir occurs along the base of slope within the Brooks Range foreland basin, and represents confined and unconfined slope-apron systems. Sediment supplied to these systems temporally ranges from mud-rich to mixed sediment and sand-rich sources. Early lowstand deposits consist of muddy unconfined slope aprons that contain slump blocks and lobes of debris flow and slurry flow deposits. At maximum lowstand slope gullies fed two separate, but contemporaneous, slope apron systems. The southern slope apron consists of four main stages (mixed sediment systems- 1-3, sandy system-4). The first two stages are confined to a small (2 by 3 mile) sub-basin and consist largely of lobe deposits fed by small leveed channels. The third stage is in an unconfined setting, and consists of extensive leveed channels and small lobes which prograded up to 5 miles into the basin. The final stage is a sandy system deposited in a proximal setting and consists largely of lobe to amalgamated lobe deposits. The northern slope apron is in an unconfined basin setting. It contains three stages (mixed sediment supply), that have prograded up to 4 miles basinward and consists of leveed channels feeding small lobes.
Reservoir distribution and characteristics appears to be largely controlled by the depositional elements and sedimentary facies within these systems. The sand-rich systems have the best reservoir quality and connectivity. In mixed sediment systems, reservoir quality decreases from channel to lobe to levee deposits. Slope aprons confined in a sub-basin show greater reservoir connectivity than in unconfined settings.
AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana