Flekkefjord Formation
(From NPD Bulletin no. 3)
Boknfjord Group
Name
From a town on the south-west coast of Norway. This formation was formerly
included in the Valhall Formation of the Cromer Knoll Group (Deegan and
Scull, 1977). The same unit was defined as the Flekkefjord Member by Rawson
and Riley (1982), and is here elevated to formation status.
Well type section
Norwegian well 9/4-2
(Texaco) from 2155 m to 2208 m, coord N 57°41'11.05" E 04°02'34.85",(Fig. 38).
Well reference section
Norwegian well 8/1-1
(Phillips) from 2379 m to 2425 m, coord N 57°51'43.53", E 03°12'27.64",(Fig. 37).
Thickness
In the type well it is 53 m, and in the reference well it is 46 m. This is
also the approximate
thickness in most wells within the Egersund Sub-Basin.
Lithology
The formation consists of dark grey shales which are variably carbonaceous,
pyritic and may contain thin limestone stringers.
Boundaries
The lower boundary of the formation is clearly defined both on gamma and
sonic logs by the contact with the more silty Sauda
Formation. The upper boundary usually appears as a distinct log break,
with higher radioactivity and higher interval transit times in the
Flekkefjord Formation. In the Egersund Sub-Basin, which is situated closer
to the source area, the boundary may be difficult to identify on logs.
Distribution
The formation is present in the Norwegian-Danish Basin. It is time-equivalent
to the upper part of the Mandal Formation in the
graben areas to the west and to the Fredrikshavn Unit C in the Danish sector
to the east (Michelsen, 1978).
Age
Ryazanian.
Depositional environment
The Flekkefjord Formation was deposited in a marine, low-energy, basinal
environment.
