34/7-15 S

General

Well 34/7-15 S was the first well drilled on the east flank of the 34/7 block. This part of the block has mainly been subsiding during Late Jurassic, Early and Late Cretaceous on the Tampen high and hence not been exposed so heavily to the erosive events, whereas the structures elsewhere in the block have suffered periods of erosion and non-deposition. The westward tilting of the Tampen area developed in these periods, and a large part of the erosion products were deposited to the west. The eastern flank received coarse clastic sediments, developed as fans next to the Inner Snorre Fault. The Middle Jurassic Brent Group probably shows the same development as elsewhere in the Tampen area. Seismic anomalies indicate possibilities for shallow gas. The primary objectives of well 34/7-15 S were to test the prospectivity of the Brent Group, and thereby test the sealing capacity of the Inner Snorre Fault; to test the stratigraphy and prospectivity of the Early Cretaceous and Late Jurassic sediments; and to obtain better seismic and velocity control of the Cretaceous and Jurassic sediments. The well fulfilled the work commitment of PL 089.

Operations and results

Wildcat well 34/7-15 S was spudded with the semi-submersible rig Treasure Saga 23 May 1990 and drilled to TD at 4646 m in the Early Jurassic Drake Formation. The well was drilled as a deviated well to the east with kick-off point at 2900 m. It was drilled with seawater and gel down to 1038 m and with KCl mud from 1038 m to TD. No shallow gas was encountered.

The sandstones of the Brent Group (Tarbert Formation) came in at 4376 m. Oil shows were recorded in thin Intra Draupne and Intra Heather Sandstones. The Brent Group proved to be water bearing with some insignificant oil shows. A total of 250 sidewall cores were attempted and 151 cores were recovered. One core was cut in the Tarbert Formation from 4379 m to 4394 m. One FMT segregated sample was taken at 3599.5 m in o