34/8-4 S

General

Well 34/8-4 S is located on the Visund Field, A structure where previous wells 3/8-1, 3/8-3, and 3/8-3 A had proved hydrocarbons in the Brent Group. The main target in 34/8-4 S was the hydrocarbon potential in the Lomvi Formation on the A-structure. Secondary targets were the hydrocarbon potentials of the Statfjord and Lunde B/C formations on the A south compartment. Pressure measurement should be acquired from the Lunde- and Lomvi Formations in order to evaluate the sealing potential of the Middle to Late Triassic sequence. The well was designed for temporary abandonment and re-entry as a subsea producer. The well was planned as a deviated hole to penetrate top Statfjord, Lunde B/C and the Lomvi Formations within structural closure, leaving more than 10 mill Sm3 oil untested up-dip. Boulders could be encountered between 350 m and 395 m. Two intervals with possibility for shallow gas were identified at 446 m and 477 m.

Operations and results

Wildcat well 34/8-4 S was spudded with the semi-submersible installation Maersk Jutlander on 6 Desember 1991 and drilled to TD at 4150 m in rocks of Triassic age. Drilling started with an 8 1/2" pilot hole checking for shallow gas. No boulders or shallow gas was encountered. Significant technical problems were encountered during drilling of this well and one third of the total rig time was counted as down time. The longest period of down time occurred after TD in the 17 1/2" hole where 31.6 days were spent repairing the BOP and wellhead. The planned TD at 4478 m was not reached due to operational problems. The pipe was backed off at 3936 m and the borehole was logged from this depth and up to the 9 5/8" casing shoe. The well was drilled vertical down to ca 2310 m where it started to build angle up to 30 ° at ca 2680 m. From here to TD the deviation varied between 30 ° and 50 °. The well was drilled with spud mud and seawater down to 1165 m, with KCl / polymer mud from 1165 m to