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Norwegian Sea: Deep Penetration

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.
This article appeared in Vol. 4, No. 2 - 2007

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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 Terraces

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.

The Deep Water

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

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. 

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