30/5-2

Well 30/5-2 is located a few km west of the Oseberg Field in the Northern North Sea. It was drilled on the northern and down dip extension of the hydrocarbon accumulation discovered by well 30/8-1 S. The main target was the Brent deltaic sands of the Tarbert Formations. The primary objectives were to prove filling level and hydrocarbon types in a down dip (northern) direction, and to prove pressure communication and continuity with the reservoirs in 30/8-1 S. Planned TD was 50 m into the Dunlin Group.

Operations and results

Appraisal well 30/5-2 was spudded with the semi-submersible installation Treasure Saga on 4 October 1996 and drilled to TD at 4076 m in the Early Jurassic Drake Formation. The total duration of the well was some 20 days behind schedule. The main contribution to this was time spent to cure a shallow gas source, corrective measures in conjunction with a 13 3/8" casing hanger sitting high and a stuck MDT tool. The well was drilled with spud mud and bentonite down to 1558 m, with KCl/polymer mud from 1558 m to TD.

The main reservoir interval consisted of the Tarbert Formation, but the Ness and ORE Formations were also encountered. Gas and oil pay was interpreted below 3528.5 m in the "Tarbert 2" reservoir, approximately 58 m and 10 m respectively. The well interpretation concludes with a GDT (gas down to) situation at 3591.5 m in the Tarbert 2 reservoir and with an OUT (oil up to) at 3602 m. An OWC is indicated at 3614 m with a FWL (free water level) at about 3616.5 m. In the Ness Formation a total of 16 m pay was interpreted in channel sands. The assumed fluid in these sands is gas, but this was not conclusively proven. The ORE (Oseberg - Rannoch - Etive) Formation had 1.4 m pay interpreted, but this may be an optimistic result as it was equally likely that this could represent so-called residual hydrocarbons. The reservoir properties are considered fairly modest with porosities generally bel