Print this pageTabasco Valley, North Slope, Alaska, A Shallow Fluvial/Estuarine Reservoir Mapped with 3D Seismic Data
KONKLER, JON L., DOUG S. HASTINGS, DEBRA H. MCGIMSEY, HENRY POSAMENTIER, and MARK H. LEANDER
A shallow fluvial reservoir at the Kuparuk River Unit (KRU), North Slope of Alaska, has been successfully delineated using 3D seismic and limited borehole data. This late Cretaceous Colville Group reservoir, informally termed Tabasco Sands', comprises a secondary target to primary production from the Kuparuk River Formation, and constitutes "behind pipe reserves". 3D seismic data and workstation interpretation tools, such as time and horizon slice techniques have been essential in defining the limits and architecture of this hydrocarbon accumulation.
Well data suggest that the Tabasco Sands are incised into underlying shales, have high lateral heterogeneity, and are limited in aerial extent. At Drill Site 2T (KRU), 3D seismic images suggest the presence of a large erosional feature, 'Tabasco Valley', approximately .5 mi wide, 3 mi long, and up to 250 ft deep. This valley, oriented approximately normal to the shelf/slope break, is interpreted to be an incised valley and is filled with fluvial to estuarine sediments. The valley fill consists of channel complexes up to 100 ft thick. Mappable seismic geometries within Tabasco Valley are steeply dipping off-lapping reflections and flatter-lying onlapping reflections. The base of Tabasco valley is erosional, indicated by sharp truncation of underlying clinoforms. Off-lapping features within the valley are associated with medium to coarse-grained lithic sandstone and conglomerate. Flatter on lapping events are associated with thin-bedded, fine-grained sand, silt and mud.