6305/1-1

General

Well 6305/1-1 is located in the northern part of the Ormen Lange Dome and was the third well drilled on the Ormen Lange Structure, following the two successful wells 6305/5-1 drilled by Hydro in 1997 and 6305/7-1 drilled by BP in 1998. The Egga sand in the Tang Formation was the main target for the well. The sand was predicted to contain gas. The Tare and Lysing Formations were considered as secondary and third target levels, respectively.

Operations and results

Wildcat well 6305/1-1 was spudded in a water depth of 863 m on 18 August 1998 with the semi-submersible installation "Transocean Leader" and drilled to a total depth of 4565 m (4551 m TVD) in Late Cretaceous sediments of the Lysing Formation. Well 6305/1-1 was drilled to 2560 m where hole problems made it necessary to plug the well back and perform a technical, sidetrack from 2467 m. The well was drilled with spud mud down to 1610 m and with "Aquacol" KCl/Polymer mud from 1610 to TD. The Egga Member of the Tang Formation and thin sandstones in the Springar Formation were proven in cores from 2558-2623,5 m. Egga sand was encountered even though the reservoir quality was poorer than prognosed. No moveable hydrocarbons were encountered in well 6305/1-1, but weak residual shows were reported in almost the entire Cretaceous section. The Egga sand in well 6305/1-1 proved to be over pressured compared to wells 6305/5-1 and 6305/7-1. Even though some sand was reported from the mud geologist at the predicted intra Tare level this was not considered as a reservoir sand. At Lysing level some thin sandstone layers were encountered, but not considered as a reservoir. Five cores were cut in the well. Four were cut in the Tang and Springar Formations in the interval 2556 m to 2628 m. Recovery for these varied from 10 % to 95 %. The fifth core was cut in the upper part of the Lysing Formation in the interval 3646 m to 3670.5 m. Recovery for this core was 97 %. An MDT fluid sample was taken a