ID: 839
OBJECTID: 839
wlbNpdidWellbore: 2068
wlbName: 34/7-21 A
wlbHistory:

General

Exploration well 34/7-21 A is a sidetrack to well 34/7-21 which found oil in three different sands in the Late Jurassic - Early Cretaceous succession. No OWC was found. The primary purpose of the sidetrack was to test the extension of these discoveries and to prove possible OWC(s). A secondary objective was to test the presence of sandstones, and possible hydrocarbons, within the Late Cretaceous in which a thin sandstone interval was proved oil-bearing in well 34/7-21.

Operations and results

Well 34/7-21A was kicked off from 1798 m in the vertical well on 16 December 1992. The well was deviated and penetrated the top reservoir 585 m west of the vertical well. It was drilled with the semi-submersible installation Treasure Saga to TD at 3360 m (2874 m TVD), 37 metres TVD into the Brent Group. Initial problems with steering the drill string resulted in a kick-off in the wrong direction. The well was turned around and lined up to the correct azimuth. The drill string got mechanically stuck three times in the interval 2465 m to 2571 m, but came free within short time. The string also got stuck at 2998 m when running in the hole after waiting on weather. The hole apparently deteriorated with time. The TD caliper log showed severe washouts of the hole, up to a maximum of 22". Waiting on weather for about 17 days was seen to be a major cause of the severe washouts. The washouts and hence increased amounts of cuttings, possibly explain the problems with the hole packing off and the string becoming stuck. Due to the hole angle and the bad hole condition logging operations were troublesome and time consuming, with many of the logs being run on drill pipe. The sidetrack was drilled with a KCl mud all through. The KCl levels were high and in addition glycol was introduced to inhibit the formation, but without the wanted effect as proved by the severe washout.

The Base Cretaceous Unconformity was penetrated at 2870 m. A 3 m thick san
wlbHistoryDateUpdated: 2016-07-06T00:00:00