Equinor Energy AS further delineated the 2023 Heisenberg oil and gas discovery in the Norwegian North Sea, which is now estimated to hold recoverable volumes to 24-56 MMboe after completion of an appraisal well and sidetrack.
Oil-bearing sands were encountered in a deeper secondary target, Hummer, and forward plans include drilling of a well in this year's second quarter to explore an additional deep prospect, Angel, while delineating Heisenberg westward.
Surrounded by Equinor-operated North Sea hubs Troll B and Kvitebjørn, as well as and Vår Energi Norge AS-operated Gjøa, Heisenberg lies within tieback range of existing hosts, partner DNO ASA said in a release. Studies are underway for fast-track development of Heisenberg, the company said.
Exploration targets
Wells 35/10-11 S and A were drilled about 140 km northwest of Bergen. These are the first and second wells drilled in in production license (PL) 827 SB and represent additional acreage for PL 827 S where the original discovery was made, according to the Norwegian Offshore Directorate. Drilling was carried out using the Deepsea Stavanger rig in 364 m of water.
The primary exploration target for well 35/10-11 S was to delineate the Heisenberg discovery made in 35/10-9 in the lower Hordaland Group in the Eocene (OGJ Online, Mar. 14, 2023). The secondary exploration target was the Hummer prospect in the Balder formation in the upper Palaeocene to lower Eocene.
The well was drilled to a measured depth of 1,853 m subsea. It was terminated in the Rogaland Group in the Palaeocene. It encountered a sandstone reservoir totaling about 10 m with good reservoir quality in the Hordaland Group. The reservoir was aquiferous with traces of hydrocarbons. In the secondary exploration target in the Balder formation, the well encountered a 3-m oil column in sandstone totaling 23 m with poor-to-moderate reservoir quality.
Because 35/10-11 S encountered the primary target in the water zone, 35/10-11 A sidetrack was drilled with the primary target of encountering Heisenberg upflank in the oil zone. The well was drilled to a measured depth of 1,690 m subsea. It was terminated in the Hordaland Group in the Eocene.
The well encountered a sandstone reservoir totaling about 12 m with moderate-to-good reservoir quality. This reservoir has a 12-m oil and gas column in the Hordaland Group. Gas-oil contact was encountered 1,571 m subsea, and the oil-water contact was proven 1,576 m below sea level. The well was not formation-tested, but extensive data acquisition and sampling were carried out.
The wells have been permanently plugged.
Resource estimates for Heisenberg prior to drilling were 4.1-9.0 million std cu m oil equivalent. Preliminary calculations indicate that the size of the discovery is 3.8-8.9 million std cu m oil equivalent.
Oil reserves in the secondary Hummer prospect are preliminarily calculated at 0.1-0.6 million std cu m oil equivalent.
Equinor is operator of the license with 51% interest. DNO Energy AS holds the remaining 49%.