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The delimitation of the Norwegian continental shelf is not finalized, but the size of the area with a sediment thickness of significance from hydrocarbon potential is of the order of 1.5 × 106 sq km. From an exploration point of view the shelf can be subdivided into 2 areas: (1) the North Sea south of 62°N where exploration drilling has been going on since 1966; by November 1, 1978, 205 exploration wells had been spudded; (2) the area north of 62°N where no exploration drilling has been permitted up to now.
Recoverable reserves of 1.4 × 109 tons of oil or oil equivalents have been discovered. The fields are located along the Central and Viking grabens, north-south Mesozoic basins along the central North Sea. Three zones have proven to be the main reservoir rocks. (1) In Jurassic sandstone, Statfjord is the most prominent field. (2) In Maestrichtian-Danian chalk, Ekofisk is the most prominent field. (3) In Paleocene-Eocene sandstone, Frigg is the most prominent field.
The Norwegian Petroleum Directorate (NPD) has risk evaluated undrilled structures south of 62°N and concluded that another 2 × 109 tons of oil or oil equivalent recoverable reserves are to be found. Evaluation of the area north of 62°N is based mainly on NPD seismic surveys. The three main areas are: (1) More Lofoten between 62 and 69°N, (2) Barents Sea north of 70°N, and (3) Jan Mayen Ridge.
The first two areas are the most extensively explored and are considered to be the most prospective. Several different types of basin development are defined. Favorable conditions for formation and accumulation of substantial amounts of hydrocarbons prevail over extensive parts. The two areas are generally considered highly prospective, but there are variations within them. The Jan Mayen Ridge is considered to be a continental block with sediments of considerable thickness. The possibility of commercial hydrocarbon deposits is highly questionable but should not be ruled out.
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