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Gohta: New oil discovery in the Barents Sea

Lundin Norway has made an exciting oil discovery on the Loppa High in the Barents Sea.
The discovery was made in carbonate rocks from the Late Permian Age (255 million years old), which is part of the Tempelfjord Group. This is the first time a successful production test has been carried out on such rocks on the Norwegian Shelf.

Lundin Norway’s latest oil discovery was made in a prospect called Gohta, in PL492 south on the Loppa High. PL492 was awarded in 2008 (APA 2007). The partners in PL492 are Noreco and Det norske. The Gohta discovery was made in exploration well 7120/1-3, drilled with the Transocean Arctic rig. The well tested flow rates of approximately 4,300 barrels of oil per day. Preliminary evaluation of the gross recoverable oil and gas resources from the discovery are estimated to be between 105 and 235 million barrels oil equivalent.

One well has previously been drilled in the licence, 7120/1-1, drilled by Shell in 1985/1986. This well had hydrocarbon shows in carbonate rocks from the Permian. Ten kilometres northeast of Gohta, in the Lundin Norway operated PL609, well 7120/2-1 from 1985, also proved traces of hydrocarbons in carbonates. The wells were tested, but only small amounts of hydrocarbons were produced. In other words, oil was present in the rocks, but it was apparently not producible.

However, new 3D seismic enabled Lundin Norway’s geophysicists and geologists to define an area where the carbonate rocks (limestone) were probably exposed to weathering processes some 250 million years ago, in much the same way these rock layers are exposed on Bjørnøya and Svalbard today. Rainwater, which was also slightly acidic at that time, dissolved and converted parts of the limestone to form holes and small caves where falling rock and other sediments were deposited on the floor. In time, the roof of the caves collapsed, and the collapsed caves preserved a network of porous systems, through which oil could flow.

Lundin Norway’s geologists and geophysicists, together with the partners in PL492, decided to drill well 7120/1-3 to examine whether such collapsed limestone cave systems containing oil could be found in the licence.

Seismic interpretations and analyses also identified younger, overlying channel-like geometrics, which were thought to represent sandstones deposited in river channels or canals in a Triassic delta (approx. 235 million years old). A decision was made to drill through these as well, to examine if they contained hydrocarbons.

The conclusion from the drilling proved the presence of river-deposited sandstone with traces of oil in the Triassic strata, and that limestones with producible oil were present in the deeper Permian strata.