34/7-28

General

Well 34/7-28 is located in the Tampen area in the Northern North Sea. It was drilled on a prospect situated north east of the Statfjord Nord field and east of the Snorre field. The well tested the NW III prospect, which was defined as a stratigraphic trap with pinch out of the Draupne Formation. The sands in the Draupne Formation were expected to be erosional products from the Snorre block positioned in a north east direction of the well.

Operations and results

Wildcat well 34/7-28 was spudded with the semi-submersible installation Transocean Leader on 30 December 1997. The well was initially drilled to a total depth of 1267 m in the 12 l/4" section where the decision was made to plug and abandon the well. The abandonment was due to concerns over the integrity of the 18 3/4" wellhead housing, which had suffered damage during BOP latching procedures. At this time a total of 24.9 days had been spent on the well. With the rig moved ca. 25 m NNE from the original location, well 34/7-28 was re-spudded on 24 January 1998 and drilled to TD at 3005 m in the Middle Jurassic Drake Formation. The final 34/7-28 well was drilled with sea water and bentonite hi-vis sweeps down to 1300 m, with silicate mud from 1300 m to 2165 m, and with KCl/glycol mud ("Aqaucol D" polypropylene glycols) from 2165 m to TD.

Apart from the Utsira Formation only traces of sand was penetrated above top Jurassic. Sandstones were encountered in the prospective level of the Viking Group. The uppermost sand at 2666 m was a 3 m thick Intra Draupne Formation sandstone overlying 10 m of Heather Formation shale. The lower sand at 2679 m was a 16 m thick Intra Heather Formation sandstone, interpreted as a gravitation deposit. Both sandstones were penetrated at shallower depth than the oil-water contact in Statfjord Nord and both were water filled. An undifferentiated sequence of water filled Rannoch/Etive Formations sandstones was penetrated from 2805