6506/12-10

General

The main objective for well 6506/12-10 was to appraise the down flanks hydrocarbons in the Garn, Ile, Tilje, and the Åre Formations, on the Smørbukk Field.

Operations and results

The vertical appraisal well 6506/12-10 was spudded with the semi-submersible installation "Ross Rig" on 21 April and drilled to 5097 m in the Early Jurassic Åre Formation within the planned budget. Boulders were encountered drilling the 36" section, and was the main reason why the 22" underreamer became stuck in 20" casing. As 12 1/4" pilot hole was drilled to 890 m, gas flow occurred when flow checking with seawater at 628 m. The 20" casing had to be set above this zone, which was considerable higher than planned. A 16" liner was then set to obtain enough integrity below 16" liner shoe to drill 17 1/2" section to 2795 m for optimum setting depth of 13 3/8" casing (lower part of Shetland). All other casing strings were set at planned depths according to "Base case" in the drilling programme. The well was drilled with seawater/bentonite down to 562 m, seawater/bentonite/CMC from 562 m to 1602 m, and Anco 2000 mud with Anco 208 glycol additive from 1602 m to 2790 m. Oil based mud (ANCO VERT) was used from 2790 The 6506/12-10 well proved no producible oil or gas in neither the Fangst nor the Båt Groups, thereby delineating hydrocarbons to the central areas of the field. The results of the 6506/12-10 well lead to the conclusion that there had to be drilled a sidetrack well in order to fulfill the obligations of the well and perform an extended production test of the Tilje Formation. Fourteen cores were cut in the Fangst and Båt Groups. FMT fluid samples were taken at four levels within the Åre and Tilje Formations. They contained mainly base oil (from the drilling fluid) and water. No indigenous hydrocarbons were found. It was decided to sidetrack the well and to penetrate higher up on the structure (6506/12-10 A). The vertical well was plugged with top plug (kick-off plug) in 13 3/8" casing