Sognefjord Formation (new)
(From NPD Bulletin no. 3)
After a fjord on the west coast of Norway, adjacent to the type area in Quadrant 31.
Well type section
Norwegian well 31/2-1
(Shell), from 1440 m to 1531.5 m, coord N 60°46' 19.16", EO3°33' 15.87",
Well reference section
None at present.
The formation consists of sandstones and sands, grey-brown in colour, medium to coarse grained, well sorted and friable to unconsolida-ted. Locally the formation is weakly micaceous with minor argillaceousand carbonaceous beds Bioclastic material and occasional calcite cemented bands occur locally.
The Sognefjord Formation has a gradational lower boundary, due to the
interdigitation of sandstones with the siltstones which form the upper part
of the Heather Formation. The base is chosen
immediately below the first continuous sandstone, often shown by reduction in
gamma ray intensity. The formation has a homogenous "blocky" log motif in the
lower half. The upper half comprises several cycles displaying
"funnel-shaped" gamma ray log motifs coincident with coarsening upward
sequences. The top of the formation is marked by the distinct lithological
break into claystones or shales, which in the type well are the overlying
The formation has only been clearly recognized in the Troll Field area, where it is the major reservoir interval.
Oxfordian to Kimmeridgian/Volgian.
The formation was deposited in a coastal-shallow marine environment.