In 1965 ExxonMobil was awarded the very first exploration licenses on the Norwegian Continental Shelf. ExxonMobil started exploring an area named the Utsira High which is 12 times bigger than Oslo. The Utsira High area is a geologic “high” in the North Sea subsurface where it was natural to start searching for oil and gas since hydrocarbons tend to migrate from deeper sediment layers up towards such “highs”- eventually to be trapped in structural and/or stratigraphic traps.

Inspired by discoveries further south in the North Sea, sediments of Permian age (225 – 280 million years ago), which were the main targets of ExxonMobil’s first exploration wells on the NCS. Sediments of Jurassic age ( 136 – 190 million years old) and Tertiary age ( 1,8 – 65 million years old), were only considered as secondary hydrocarbon sediments. It soon appeared, however, that deepmarine layers of early Tertiary and classic Jurassic age contained hydrocarbons on the Utsira High. Oil and gas in Tertiary traps are originally formed in layers of Jurassic age.

The first oil from the NCS was taken up in 1967 from well 25/11-1 in layers of early Tertiary age (54 million years old) in an area close to the later to be discovered Balder field. Later on a number of discoveries were made on or near the Utsira High, and ExxonMobil has in fact made or participated in most of these discoveries. The gas in the Sleipner East field (Paleocene/early Tertiary age) was discovered in 1981, and in the following year the gas/condensates field Sigyn was discovered in rocks of Triassic age. ExxonMobil has over 30 years accumulated a lot of knowledge about the Utsira High which was used in an extensive exploration programme in the 1990’s. The programme, which turned out to be very successful, yielded a number of discoveries including Grane, Jotun, Ringhorne and Hanz.