35/11-21 A

General

Well 35/11-21 A was drilled to appraise the 35/12-2 Grosbeak discovery on the Ryggsteinen Ridge in the North Sea. The objective was to prove extension of the Fensfjord Formation discovery, a northern extension of Ness Formation sand, and to establish fluid contacts in Brent Group.

Operations and results

Appraisal well 35/11-21 A was kicked off at 1010 m in primary well 35/11-21 S on 6 September 2018. It was drilled with the semi-submersible installation Transocean Arctic to TD at 2931 m in the Early Jurassic Cook Formation. Operations proceeded without significant problems. The well was drilled with Innovert NS oil-based mud from kick-off to TD.

The Sognefjord Formation was encountered at 2281.0 m (1964.0 m TVD). It contained a 45 m gas column of which 20 m was effective reservoir sandstone with very good reservoir properties. The Fensfjord Formation was encountered at 2389.0 m (2071.8 m TVD). Fensfjord contained an oil column of about 8 m, of which 2 m was effective reservoir in sandstone with moderate to good reservoir properties. Top Brent Group, Ness Formation was encountered at 2724.9 m (2407.6 m TVD). Ness contained a total oil column of 50 m, of which 15 m was effective reservoir sandstone with good reservoir properties. The Brent Group oil-water contact was not found. Weak shows were described in silty sandstones in the Heather Formation above the Sognefjord Formation and above the Fensfjord Formation, otherwise there were no oil shows observed outside of the hydrocarbon-bearing reservoir sections.

Five cores were cut with 100% recovery. Three were cut from 2275 to 2437.32 m in the Viking Group, and two were cut from 2730.5 to 2839.26 m. MDT fluid samples were taken at