29/6-1

General

Well 29/6-1 was drilled ca 2 km west of the UK border on the eastern margin of the East Shetland Basin. The primary objective was the Brent Group in a fault block separate from the Hild structure some few km to the southwest. The secondary objective was the Statfjord formation.

Operations and results

Wildcat well 29/6-1 was spudded with the semi-submersible installation SEDCO 707 on and drilled to TD at 4832 m.

The well was spudded by "Sedco 707" on 12.10.81. When drilling the 17 1/2" pilot hole (with 1.1 sg mud) in the 24" section, mud losses occurred at 870 m. The hole was displaced to seawater and operations continued down to 1205 m where the 24" casing was set. Further drilling went with increasing mud weights due to tight hole problems, to a point where the overbalance considerably reduced penetration rate. Due to high deviation the pipe became differentially stuck at 4664 m. The well was planned to be vertical, but ended up severely deviated. From 3973 m to 4097 m hole inclination increased from 5 degrees to 10.5 degrees, increasing to 15.5 degrees by 4155 m, as a result of the increased dip of the bedding planes. At 4155 m a pendulum drill assembly was used but the hole inclination continued to increase to 19.5 degrees. By 4211 m the angle had reduced to 17 degrees but again increased to a maximum of 21 degrees by 4457 m, and then decreased to 20.25 degrees by 4570 m. Below this depth, surveys were not possible due to the hole conditions with overpull and stuck pipe on the connections and tight hole on trips. Keyseating, washout in the sandstones and the swelling nature of the clays in the Dunlin formation added to the problem caused by hole angle. At TD Schlumberger HDT log was run and the