34/7-19

General

Well 34/7-19 is an appraisal well on the Vigdis Middle structure, south of the Snorre Field on Tampen Spur in the Northern North Sea. The well was drilled approximately 1.5 km north-west of well 34/7-16, on a north-west dipping, rotated fault block. A wedge of partially eroded Viking Group/Heather Formation was interpreted above the reservoir. The primary objectives of the well were to prove the north-western extension of the 34/7-16 reservoir into Segment M1 of the Vigdis Middle and establish an oil water contact for the upper Brent Group. A secondary objective was to test the possible existence of a Late Jurassic Draupne Formation shale wedge. The well was designed to be used in possible future field development. Shallow gas was expected at a depth of 445 m on the well location. This level represents a sand layer at Top Pliocene where gas had been observed in several previous wells in block 34/7. Shallow gas could also be expected in thin sand layers, below seismic resolution down to Top Utsira Formation. A boulder bed could be expected approximately 60 m below sub seabed. Prognosed TD was estimated to 2803 m, and an OWC was assumed at 2418 m (2400 m MSL).

Operations and results

Well 34/7-19 was spudded with the semi-submersible installation West Alpha on 24 September 1991 and drilled to TD at 2800 m in the Early Jurassic Cook Formation. At core point, 2439 m the weather deteriorated. Due to extreme heave the top drive jumped out of hook. The drill pipe bent and the top drive fell down on the drill floor. The shear ram was activated leaving the drill string with core assembly in the hole. Fishing and WOW caused 4.5 days delay before coring could commence. The well was drilled with spud mud down to 1166 m and with KCl mud from 1166 m to TD. Shallow gas was not encountered in this well, but a zone from 526 to 527.5 m was interpreted as potentially gas bearing. One boulder bed was encountered at 363 m.

Down to the Top Jurassi