Researchers said recent study results suggest the possibility of oil and natural gas discoveries in a 7,000-sq km area of the UK North Sea because of “phantom” volcanoes.
Geologists said a large swathe of the UK Continental Shelf was unexplored for more than 50 years because of beliefs about the existence of volcanoes based upon what researchers now call “incorrect geological models.”
Scientists from the University of Aberdeen led a study resulting in an article entitled “Phantom volcanoes discovery signals new hope for North Sea oil and gas exploration” that was published in November 2018 in the Journal of the Geological Society.
Previously, scientists believed the Middle Jurassic Rattray volcanic province off northwest Scotland contained three volcanoes that erupted 165 million years ago. The notion that the area contained empty magma chambers ruled out possible oil and gas discoveries.
The volcanoes were believed to have been formed millions of years ago during seismic activity under the North Sea that almost created an ocean between Britain and Europe—a rifting episode geologists have described as a failed ‘Jurassic Brexit’ attempt.
Assumption overturned
Nick Schofield and Ailsa Quirie from the University of Aberdeen along with colleagues from Heriot-Watt and the University of Adelaide have questioned this assumption.
Schofield said reinterpretation using 3D seismic data and well data shows no volcanic centers are present, and the Rattray volcanics were instead sourced in fissure eruptions from linear vents.
Norway’s Petroleum Geo-Services provided the 3D seismic.
The fissures run parallel to the Highland Boundary Fault, which intersects the Rattray volcanics at the Buchan-Glenn Fissure System.
“What we found has completely overturned decades of accepted knowledge,” Scholfield said. “Our study has shown these volcanoes never existed at all. Essentially this gives us back a huge amount of gross rock volume that we never knew existed.”
Schofield added: “There is a huge area under there that hasn’t been looked at in detail for a long time” because of an incorrect geological model. Meanwhile, discoveries still are being made in the North Sea, such as the Central Graben and Viking Graben areas.
UKCS discoveries
Wood Mackenzie Ltd. said the UK Central Graben basin is in less than 100 m of water. The Mesozoic high-pressure, high-temperature play remains of interest following the large Culzean discovery in 2008, which is expected on stream late this year.
In January, CNOOC Petroleum Europe Ltd. discovered natural gas and condensate pay in the Glengorm prospect in the Central Graben area. The CNOOC subsidiary drilled an exploration well to 5,056 m TD in 86 m of water, encountering net gas and condensate pay with a total net thickness of 37 m in a Upper Jurassic reservoir.
Recoverable resources are estimated at about 250 million boe, said partner Total E&P UK North Sea Ltd.
Further drilling and testing will be carried out to appraise resources and the productivity of the reservoir, Total said.
The discovery was in the P2215 license, previously part of the Maersk Oil portfolio, and close to existing Total-operated infrastructures offering tie-back possibilities, such as the Elgin-Franklin platform and the Culzean project.
CNOOC is operator with 50% working interest. Partners include Total and Euroil, a wholly owned subsidiary of Edison E&P SPA, each with 25% working interest.
