7229/11-1

General

Well 7229/11-1 was the first well drilled in Production Licence 183 following the interpretation of a 3D seismic survey acquired in 1991. The well is situated on the northeastern part of the Finnmark Platform. The target of the well was the "Castor" prospect, consisting of two Permian-Carboniferous (Sakmarian to Asselian age) carbonate build-ups confined in combined dip-closed and stratigraphic traps. The objectives were to test the hydrocarbon potential of the carbonate build-ups, referred to as Carbonate 1 and Carbonate 2 respectively, to acquire additional information on the Permian-Carboniferous of the Finnmark Platform, and to calibrate the seismic expression of the build-ups.

Operations and results

Exploration well was spudded with the semi-submersible installation "Ross Rig" on 9 August 1993 and drilled to a total depth of 4630 m in limestone of Middle - Lower? Carboniferous age. The well was drilled with sea water and hi-vis pre-hydrated bentonite pills down to 1098 m, with KCl / polymer mud from 1098 m to 3012 m, and with a high-temperature KCl / Polymer mud from 3012 m to TD. The soft seabed did not present anchoring problems. No shallow gas was encountered. Drilling problems were experienced in the interval 339 m & 379 m. A seismic marker (black loop) corresponds to the top of this interval, which is interpreted as a boulder rich sequence. Drilling problems could have been due to boulders to fall into the hole and become wedged, thus causing sticking. The predicted carbonate build-up targets were encountered but were not reservoir facies. Carbonate 1 was confirmed to be build-up / build-up flank facies; Carbonate 2 was found to be carbonate platform facies. No hydrocarbon shows were encountered in the well. Nine cores totalling 180.9 metres length were successfully cut and retrieved from the Permian-Carboniferous. No hydrocarbon shows were encountered in the well. The well was plugged and abandoned as a dry hole on 15 Dec