6507/2-2

General

The Dønna Terrace forms a large down faulted block on the western margin of the Trøndelag Platform, situated between the Nordland Ridge and the Vøring Basin. The structure to be tested by 6507/2-2 is situated on the western edge of the Dønna Terrace. This structure was earlier tested by well 6507/2-1, which however left a considerable untested column up-dip from the well position. The main target of the well was the Jurassic reservoirs of Garn, Ile, and Tilje Formation. The secondary objectives were to test the prospectivity of the Cretaceous sands in the Lysing and Lange Formations or at least to obtain stratigraphic information from these formations.

Operations and results

Wildcat well 6507/2-2 was spudded with the semi-submersible installation Polar Pioneer on 21 October 1991 and drilled to TD at 3958 m in Early Jurassic sediments of the Åre Formation. The well had 37% downtime due mainly to repeated occurrences of stuck drill pipe. Drilling went relatively smooth down to setting of the 9 5/8" casing shoe at 2760 m. After having cut two cores in the 8 1/2" section the well was shut in due to an influx at 3336 m. The well was killed with increased mud weight, but the pipe was found to be stuck. The pipe could not be freed and was cut at 3175 m. The well was then plugged back and sidetracked from 2989 m and drilled to 3326 m with minor problems. A 7" liner was run and set with shoe at 3324 m and the 6" section was then drilled to 3737 where parts of the bit sub was lost in the hole. This led to 20 days lost while attempting to recover the fish and sidetrack past the fish. Eventually the fish was partly recovered and drilling commenced to TD. The well was drilled with seawater and hi-vis pills down to 685 m and with a KCl/polymer mud from 685 m to TD.

Oil shows were recorded on sandstone laminae in the interval 2208 ? 2750 m in the Shetland Group. The Cretaceous Lysing Formation was encountered at 2817.5 m