35/11-21 S

General

Well 35/11-21 S was drilled to appraise the 35/12-2 Grosbeak discovery on the Ryggsteinen Ridge in the North Sea. The primary objective was to explore the reservoir potential of the Ness Formation and to prove oil in the Etive Formation.

Operations and results

Appraisal well 35/11-21 S was spudded with the semi-submersible installation Transocean Arctic on 26.July 2018 and drilled to TD at 2800 m (2588 m TVD) m in the Early Jurassic Cook Formation. Operations proceeded without significant problems. The well was drilled with seawater and bentonite sweeps down to 449 m, with KCl/polymer/GEM mud from 449 to 996 m, and with Innovert NS oil-based mud from 996 m to TD.

Top of Brent Group, Ness Formation was penetrated at 2595.2 m (2383 m TVD). The Ness and Etive formations were oil-bearing down to top Rannoch Formation at 2686 m (2474 m TVD). Of this ca 90 m oil column 45 m was effective reservoir sandstone with good to very good reservoir properties. In addition to shows in Ness-Etive, there were oil shows in Rannoch Formation sandstone, described as very weak patchy pale yellow direct fluorescence, very slow, very weak, blue white to pale yellow cut fluorescence, weak, pale yellow fluorescent residue. Otherwise there were no shows in the well.

Three 54 m cores were cut from 2566 to 2620.9 m, from 2620.90 to 2675.4 m, and from 2675.4 to 2729.8 m. Each core was cut with 100% recovery. MDT fluid samples were taken at 2615.5 m (oil), 2634.49 m (oil), 2657.54 m (oil), 2681 m (oil), and 2698.5 m (water).

The well was permanently abandoned on 5 September 2018 as an oil appraisal well.

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