Norway sheds light on recent gas discovery in North Sea

More information about a recent gas and condensate discovery in the Norwegian sector of the North Sea has come to light. This discovery was made by Wellesley Petroleum using one of the Odfjell Drilling-managed rigs.

The discovery was revealed by Wellesley’s partner, DNO, a few days ago, as Norway’s “largest hydrocarbon discovery” in ten years, with a preliminary evaluation of comprehensive data indicating gross recoverable resources in the range of 120-230 million barrels of oil equivalent (MMboe) on a P90-P10 basis. 

This came after the Norwegian Petroleum Directorate (NPD) granted Wellesley Petroleum a drilling permit for the well 35/10-10 S in February 2023. The firm obtained consent for exploration drilling in block 35/10 in the North Sea prior to this from the Petroleum Safety Authority Norway (PSA).

According to the NPD, Wellesley Petroleum concluded the drilling of wildcat wells 35/10-10 S and 35/10-10 A, which were drilled about 25 km northwest of the Troll field and 150 km northwest of Bergen. The drilling work was done with the Deepsea Yantai rig, – formerly known as the Beacon Atlantic – which is owned by China’s CIMC and managed by Odfjell Drilling.

These are the first and second exploration wells in production licence 1148, awarded in APA2021. The prospect, Carmen was expected to be spudded in March 2023 and the water depth at the location is around 360 metres. Wellesley Petroleum holds an ownership interest of 50 per cent and acts as the operator of the licence, while its partners are DNO Norge (30 per cent), Aker BP (10 per cent) and Equinor (10 per cent).

While the primary exploration target for well 35/10-10 S was to prove petroleum in Middle Jurassic reservoir rocks in the Etive and Oseberg formations in the Brent Group, the secondary one was to prove petroleum in the Early Jurassic Cook Formation. On the other hand, the objective of appraisal well 35/10-10 A was to encounter the petroleum-water contact in a lower position on the structure and to collect liquid samples from the aquifer.

Furthermore, the well 35/10-10 S encountered a 210-metre gas-condensate column in the Ness, Etive and Oseberg formations, of which a total of 90 metres was sandstone reservoir with poor to moderate quality. In the Cook Formation, the well encountered a 70-metre gas-condensate column, of which a total of 23 metres was sandstone reservoir with poor quality.

In addition, a 13-metre oil column was also encountered in the Early Jurassic Amundsen Formation in the Dunlin Group, where a total of 13 metres was sandstone reservoir with poor quality. The NPD explains that the well 35/10-10 A was drilled lower on the structure, 900 metres west of the main well and encountered a 240-metre gas-condensate column in the Ness, Etive, Oseberg and Cook formations, with 50 metres being sandstone reservoir with poor to moderate quality.

The water was encountered in the Cook Formation from a vertical depth of 4,158 metres below sea level. Based on the NPD’s statement, preliminary estimates indicate the size of the discovery is between 9 and 46 million standard cubic metres (Sm³) of recoverable oil equivalent. The licensees will initiate early-phase development studies, and are considering additional appraisal wells within the discovery.

Moreover, the well 35/10-10 S was drilled to a vertical depth of 4,030 metres below sea level and was terminated in the Amundsen Formation in the Early Jurassic while extensive data acquisition and sampling have been carried out. In contrast, the well 35/10-10 A was drilled to a vertical depth of 4,212 metres below sea level and was terminated in the Cook Formation in the Early Jurassic.

The wells have been permanently plugged and abandoned and the Deepsea Yantai rig will now drill the wildcat well 25/7-11 S in production licence 984 in the North Sea, where DNO Norge is the operator.