Wellesley wraps up appraisal of Grosbeak discovery in North Sea

Wellesley Petroleum has successfully appraised the Grosbeak discovery in the Northern North Sea by wells 35/11-21S and 35/11-21A.

Transocean Arctic rig; Author: Marcusroos; Source: Wikimedia - under the public domain

The wells were drilled in production license Pl248I where Wellesley is the operator and holds a 60% operated interest.

Well 35/11-21S encountered a gross oil column of 90 meters at the target Middle Jurassic Brent Group level.

Wellesley said that, within this oil column, 45 meters comprised net reservoir with good to excellent reservoir properties. Extensive data was acquired from the reservoir interval including a successful well test which confirmed the high quality and good connectivity of the reservoir.

Sidetrack well 35/11-21A encountered 20 meters of excellent quality gas-bearing reservoir and an 8 meter oil column in the shallower Upper Jurassic Sognefjord and Fensfjord formations. The underlying Brent Group reservoir comprised a 50 meter oil column in the Ness Formation with 9 meters of sandstones lying within the oil zone. Pressure data from these sandstones indicates good connectivity to the zone tested in the 35/11-21S well.

The updated range of recoverable resources in the Grosbeak Discovery is 53 – 115 million barrels of oil plus 269 – 432 billion cubic feet of gas. The 35/11-21S and A wells have been plugged and abandoned and development studies will start.

Chris Elliott, CEO of the Wellesley Group of companies, commented: “This is a very positive end to our operated drilling campaign in the Grosbeak area. Our pre-drill subsurface studies of Grosbeak indicated that the Brent Group sandstones were both predictable and well connected and this has been demonstrated by the appraisal wells, significantly reducing the development risk of this reservoir. The discovery of a separate, excellent quality gas reservoir in the Upper Jurassic also adds significant resources to what we expect to be a material and commercially robust future development.”

The wells 35/11-21S and 35/11-21A were the first and second exploration wells in production license 248 I. Production license 248 was awarded in 1999 and production license 248 I was carved out in 2017.

Wells 35/11-21 S and 35/11-21 A were drilled to respective vertical depths of 2564 and 2614 meters, and respective measured depths of 2776 and 2907 meters below the sea surface. Both wells were terminated in the Cook formation in the Lower Jurassic. Water depth at the site is 360 meters. The wells have been permanently plugged and abandoned.

The wells were drilled by the Transocean Arctic, which will now drill wildcat well 30/6-30 in the northern North Sea in production license 825, where Faroe Petroleum is the operator.