--> Abstract: Reservoirs in a Structurally Controlled Estuary: The Jurassic Snohvit Gas-Condensate Field, Barents Sea, Norway, by Atle Folkestad, Signe Ottesen, and Arnfinn Romuld; #90039 (2005)

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Reservoirs in a Structurally Controlled Estuary: The Jurassic Snøhvit Gas-Condensate Field, Barents Sea, Norway

Atle Folkestad, Signe Ottesen, and Arnfinn Rømuld
STATOIL, Stavanger, Norway

Development planning for gas-condensate production from the Snøhvit Field in the continental, rifted Hammerfest Basin, has provided an opportunity for revisiting the key sedimentary and tectonic controls on this important region of the Barents Shelf. Analysis of 2D and 3D seismic data together with some 17 exploration and appraisal wells and 1600 meters of cores now shows the importance of tectonically-enhanced accommodation creation during deposition of the Upper Triassic-Middle Jurassic succession.

The study interval of strata consists of a fluvial/coastal plain clastic wedge (Tubåen and Nordmela formations) overlain by a thick estuarine succession (Stø Formation). The latter consists of (in stratigraphic younging order) (a) inner-estuary tidal/fluvial sandstones, (b) lagoonal/central basin mudstones and sandstones, (c) beach-barrier sandstones and (d) offshore mudstones (Fuglen Formation). This succession is overall transgressive, and is unusually thick to be estuary-infill. It is interpreted as estuarine because of the two clear fluvial and marine sediment-input points, its tidal facies, and because of the landward-stepping stacking pattern of the strata. Syn-sedimentary tectonic movement on a fault zone centrally in the basin and on the northern margin fault complex apparently provided a rapidly subsiding trough in this northwestern part of the Hammerfest Basin. This, in turn, created ideal conditions for large-scale transgression and for the thick accumulation of the linked fluvial-brackish water- shallow marine deposits. This type of tectonically controlled estuarine valley fill differs significantly from the conventional incised-valley estuaries.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005