2/11-8

General

Well 2/11-8 was designed to drill on the western part of block 2/11, approximately 2.3 km north of the Norwegian-Danish sector line. The well was located in the western part of the Ål Basin, separated from the Grensen Nose to the west by a series of faults. The primary target was sandstone of Late Jurassic age. Pre-Late Jurassic sandstones, probably Permian, were considered the secondary target. The main objectives for well 2/11-8 were to prove hydrocarbons in the target Formations; to define the reservoir level and reservoir quality adjacent to the Grensen Nose; and to collect geological information important for further reservoir evaluation and geological modelling in the area. Seismic amplitude anomalies were present at 347 m, 435 m, and 597 m. Shallow gas could not be excluded at these levels so an 8 1/2" pilot hole was planned to be drilled. The total depth of the well was planned to be at 4616 m, in igneous rocks of Permian age.

Operations and results

Wildcat well 2/11-8 was spudded with the semi-submersible installation Polar Pioneer on April 3 1991 and drilled to a total depth of 4584 m in clastic rocks of Carboniferous to possible Devonian age. The well was drilled with spud mud down to 1018 m, with ANCOQUAT cation polymer mud from 1018 m to 2515 m, with KCl mud from 2515 m to 3717 m, and with HPHT mud from 3717 m to TD.

The only Late Jurassic (Ryazanian to Volgian) sediments encountered in the well were 3 m of carbonaceous claystone, representing the Mandal Formation of the Tyne Group. The thin Jurassic section rested unconformably on Carboniferous sediments. Poor shows were observed in the Jurassic claystones as well as in carbonaceous claystones between 4265 m to 4335 m in the Carboniferous. A single 10 m core was cut at TD for stratigraphic purposes. The core recovered claystones with minor sandstone interbeds and stringers of limestone and was dated to possible Devonian. No fluid samples were taken. Th