3/7-4

General

Well 3/7-4 was designed to drill a prospect on the Lulita culmination. The Lulita prospect extends in to Danish waters, and forms part of an elongated, N-S trending, salt induced feature on the western margin of the Søgne Basin. The present structural features were developed during mid Cretaceous time, and closure at Late Cretaceous and Tertiary levels essentially reflects compaction and drape over the Jurassic high. The Jurassic Lulita closure is separated from the area tested by the 3/7-3 well by a faulted saddle, which also is well expressed at Tertiary and Cretaceous levels, providing a vertical closure of some 75 metres. The well had as primary objective to test the hydrocarbon potential of Middle Jurassic sandstones within a structural/stratigraphic trap, and as secondary objective to testing the potential in possible Late Jurassic and Early Cretaceous sandstones, within a structural trap. Additional objectives included testing of Late Cretaceous Chalk, found hydrocarbon bearing in the nearby Harald field, Paleocene/Eocene turbiditic sandstones, and the reservoir quality of the Triassic sequence. The well should drill some 150 m into rocks of Triassic age. Shallow gas could be encountered at 317 to 388 m, at 485, and at 515 m according to seismic anomalies.

Operations and results

Wildcat well 3/7-4 was spudded with the semi-submersible installation Hunter on 20 September 1989 and drilled to TD at 3723 m in the Permian Zechstein Group. At 3472.9 m the string was backed off, and a cement kick off plug was set. The hole was sidetracked from 3405 m. The well was drilled with seawater and hi-vis spud mud down to 622 m, with KCl polymer from 622 m to 3473 m, and with seawater/polymer from 3473 m to TD. No shallow gas was encountered.

A 160 m hydrocarbon column from top Ula Formation and down to 3572 m in the Bryne Formation was found from well-logs, core shows, and RFT pressure gradients. Strong shows were recorded throughou