6507/12-3

General

Wildcat well 6507/12-3 was drilled east of and near to the Midgard field on Haltenbanken. The main objective was to test the W-1 prospect located on the western margin of the Trøndelag Platform, on the eastern edge of the Ellingråsa Graben. The structure was seen as a domed N-S striking horst restricted by the main platform fault to the west and a related antithetic fault to the east with throws of approximately 350 m and 100 m, respectively. Primary target was the Middle Jurassic sandstones of the Fangst Group. A secondary target was the Lower Jurassic sandstones of the Tilje Formation, and to penetrate the coal horizon in the Åre Formation. Proposed TD was at 2700 m.

Operations and results

Well 6507/12-3 was spudded with Wi1h. Wi1helmsen semi-submersible installation Treasure Saga on 16 August 1985 and drilled to TD at 2600 m in the Early Jurassic Åre Formation. The well was drilled with spud mud down to 380 m, with gel mud from 380 m to 920 m, with Gypsum / Polymer mud from 920 m to 1949 m, and with a gel mud again from 1949 m to TD. A gas flow occurred between the 20" and 30" casing. The casing was perforated at 705 m and cement successfully squeezed. Gas flow continued to be a problem and the 13 3/8" casing was also perforated and cement squeeze was performed in both the lower and upper perforations.

The Quaternary/Tertiary Sequence was 1596 m thick and consisted predominantly of marine claystones. Cretaceous was represented by a 75 m sequence of Springar Formation. Two metre of Spekk Formation was encountered at 1937 m, followed by 33 m of Melke Formation. The Fangst Group was penetrated at 1974 m, 20 m above the prognosed depth. MWD displayed fall in resistivity and the formation was considered dry. All Jurassic sandstone sequences were water bearing. A number of gas peaks were recorded from 474 m to 804 m, but there were no oil shows observed in the well.

Two cores were attempted in the in