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The Norwegian Sea covers more than
200 000 km2 of highly prospective acreage
with many proven discoveries of Mezosoicand
Cenozoic age. The large shelf area
can be divided into three sub-regions.
The partly mature eastern province (Trøndelag Platform, Halten and Dønna terraces and Nordland Ridge); the relatively unexplored deep Cretaceous basin province (Vøring and Møre basins) and the virgin westernmost province with volcanic influences. Oil and gas discoveries have established proven petroleum systems in both the eastern province and Cretaceous basins. The volcanic province remains un-drilled but with new regional seismic lines it is possible to identify several structures with promising hydrocarbon potential.
See seismic offshore Mid-Norway (PDF - 700kb)
The terrace areas within the eastern province (Halten and Dønna terraces) have been extensively explored for the last three decades and numerous commercial oil, condensate and gas discoveries have been made within rotated Jurassic fault blocks. On the Trøndelag Platform east of the terrace areas the Late Jurassic source rock is considered to be immature and although no commercial discoveries have been made the less explored Triassic/Permian play is believed to be more promising. The key to understanding this area is better imaging of the Paleozoic sequence and new, long offset data has significantly progressed the imaging of Paleozoic highs and basins within the platform area.
Within the deepwater Vøring and Møre
basins to the west there are many large
structures, often covering up to several
thousand square km each, which have
only been explored by one or two wells,
e.g. Gjallar Ridge, Vema Dome, Nyk High,
Utgard High and Helland-Hansen Dome.
A few oil and gas discoveries have been
made but uncertainty remains regarding
the reservoir and source potential within
the different parts of the basins. Much of
the uncertainty can be related to the difficulty
in mapping the base Cretaceous
unconformity which is often found at
depths in excess of 6s twt, depths at which
“conventional” seismic data often fail to
provide a confident image. New long offset (10 km) and long record
length (10 s twt) data acquired offshore
mid Norway has generated new and valuable
information for the deepwater basins.
A comparison of a 10 s twt map and a 6 s
twt map illustrates the advantages of the
long record length data. In addition to the
structural improvements provided by the
new data, gathers with far and ultra far offsets
may also provide new information not
previously available for analysis. Numerous
undrilled and well defined DHI’s (both
flatspots and AVO effects) can be found
throughout the basin area, (see seismic
section for example). Due to the size of the
structures and relatively few wells in the
deepwater basins, this area can be characterized
as underexplored.
The volcanic province, including the
Vøring and Møre marginal highs, stretches
along the entire mid Norway shelf and
consists of both massive lava flows and
large sill complexes. Much of the area is
underlain by what is assumed to be a large
northeast-southwest trending Mesozoic
sedimentary high which is currently the
focus of much of the industry interest offshore
mid Norway. Although this area has
not yet been explored by sub-basalt wells,
drilling projects are currently being evaluated
by the oil industry and academia.
The volcanics vary in thickness from a
few hundred meters up to several km and
the seismic image underneath varies from
good to poor (although not necessarily in
proportion to the basalt thickness).
Promising sub-basalt observations such
as well-defined fault blocks have been
seen on several lines and oil companies
and processing contractors are now focusing
much of their efforts on improving the
sub-basalt image, e.g. PSDM.
The sub-basalt region offshore mid Norway
can be classed as a typical frontier
area where the entrance fee may be high
but where the potential rewards are well
worth the effort.
Updated: 17.11.2008 10:07 by Alf Kvassheim
GeoPublishing, c/o NGU 7491-TRONDHEIM, NORWAY +47 73904090 / +47 90563595
