34/8-5

General

Well 34/8-5 is located on the A-structure on the Visund Field. This is a NNE-SSW oriented elongated fault block with the Pre-Cretaceous strata dipping towards WNW. The A-Central fault divides the A-structure into the A-North and A-South compartments. Well 34/8-5 was drilled on the southern part of the A-South compartment, ca 6 kilometres SSW of Visund Discovery well 34/8-1. The primary objective was to appraise the Jurassic Brent Group. A secondary objective was to test reservoir quality of an Oligocene submarine fan system. Possible shallow gas was predicted at 604 and 793 m.

Operations and results

Appraisal well 34/8-5 was spudded with the semi-submersible installation Transocean 8 on 18 February 1991 and drilled to TD at 3540 m (3528 m TVD) in the Late Triassic Lunde Formation. The 36" hole was drilled to TD at 406 m, but when attempting to stab in the 30" casing the hole could not be located. The well was re-spudded and this time with success. An 8 1/2" pilot hole was drilled from 406 m to 850 m to check for shallow gas. No gas was observed. The well was planned vertical, but built some angle below 2660 m, and at ca 2720 m the deviation was ca 10 deg. This angle kept down to TD resulting in a 12 m discrepancy between measured and vertical depth at TD. There were also some hole curable problems during logging, but otherwise operations proceeded without significant problems. The well was drilled with seawater and hi-vis pills down to 1197 m and with KCl/polymer mud from 1197 m to TD.

Thinly developed water bearing Oligocene and Eocene sands were encountered. The Brent Group was encountered at 2855 m and was found water bearing with oil shows on the cores. The shows continued down to 2977 m. Otherwise there w