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Abstract: Tertiary Fluvial Hydrocarbon Reservoirs in the Kenai Peninsula Cook Inlet Basin, Alaska

STRICKER, G.D. and R.M. FLORES, U.S. Geological Survey, Denver, CO 80225-0046

Onshore Tertiary rocks in the Kenai Peninsula include the Tyonek, Beluga, and Sterling Formations. These coal-bearing formations contain conglomerates and coarse to fine grained sandstones representing various fluvial-system types. Similar sandstone bodies have produced hydrocarbons both offshore and onshore and a knowledge of sandstone-body architecture may aid in discovery of more hydrocarbons.

The Oligocene-Miocene Tyonek Formation includes sandstone and conlgomeratic bodies deposited in alluvial fans and tidally influenced braided-streams. Alluvial-fan sandstone architecture comprises vertically stacked, erosional-based conglomerates and sandstone successions that range from 40 ft thick and 900 ft wide to 50 ft thick and 1,200 ft in lateral extent. Braided-stream sandstone architecture consists of multi-erosional sandstone bodies, which are >100 ft thick and >5,000 ft in lateral extent. These sandstones are interbedded with burrowed, mud-draped, and flaser-bedded tidal and intertidal deposits.

The Upper Miocene Beluga Formation contains sandstone and conglomeratic sandstone bodies deposited in meandering and anastomosing streams. Three types of reservoir architecture includes (1) multi-erosional and multi-lateral sandstone bodies >250 ft thick and >15,000 ft in lateral extent deposited meandering streams; (2) narrow, multi-erosional sandstone bodies >15 ft thick and >900 ft lateral extent deposited in anastomosing streams; and (3) a combination of both 1 and 2.

The Upper Miocene to Pliocene Sterling Formation consists of sandstone bodies deposited in braided and meandering streams. The architecture includes multi-erosional and multi-lateral sandstone bodies >300 ft thick and >12,000 ft in lateral extent commonly with “feathered” tops. These bodies are often internally partitioned by abandoned channel plugs of fine-grained clastics.

AAPG Search and Discovery Article #90937©1998 AAPG Annual Convention and Exhibition, Salt Lake City, Utah