Wellesley Petroleum AS has successfully appraised the Grosbeak discovery in the Northern North Sea by wells 35/11-21S and 35/11-21A. The most optimistic estimate, as given by NPD, is that the discovery may contain resources close to 200MMboe.
The larger part of this is in the Brent Group, while the remaining is in the Sognefjord and Fensfjord formations.
Prior to the drilling of the two wells, the operator’s resource estimate for the discovery was a downside of 12MMboe and an upside of 115MMboe.
Well 35/11-21Sencountered a gross oil columnof 90 metres at the target Middle Jurassic Brent Grouplevel. Within this oil column, 45 metres 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 35/11-21Aencountered 20 metres of excellent quality gas-bearing reservoir and an 8 metre oilcolumn in the shallower Upper Jurassic Sognefjord and Fensfjord formations.
The underlying Brent Group reservoir comprised a 50 metre oil column in the Ness Formationwith 9 metres of sandstones lying within the oil zone.
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.
“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,” Chris Elliott, CEO of the Wellesley Group of companies, said.
“The discovery of a separate, excellent quality gas reservoir in the Upper Jurassicalso adds significant resources to what we expect to be a material and commercially robust future development,” Elliott added.
It is particularly pleasing to have reached this point only 10 months after assuming operatorship of the PL248I licence. These wells conclude an operated summer drilling campaign of 159 days duration with almost 13,000 metres drilled in 5 boreholes and very extensive data collected from each of the 5 hydrocarbon-bearing zones encountered. Drilling efficiency has been outstanding and was undertaken with excellent focus on risk management and major accident prevention. We extend our gratitude to our licence partners, our network of suppliers and the relevant authorities for their support in the planning and delivery of this well programme”