33/9-11

General

Wildcat well 33/9-11 was drilled to test the 33/9-Epsilon prospect 6 kilometres north of the 33/9-Beta oil discovery and 10 kilometres northeast of the Murchison Field (UK). The Epsilon structure is a northwest tilted fault block and is expressed as a topographic high at the Kimmerian Unconformity surface. The primary objective was to test the hydrocarbon potential in the Middle Jurassic Brent Sand. The Early Jurassic Statfjord Sand was secondary objective.

Operations and results

Exploration well 33/9-11 was spudded with the semi-submersible installation Fernstar on 17 June 1978. The spud location turned out to be in a 25 m diameter crater in the sea floor. Due to problems with tilting of the temporary guide base two unsuccessful spuds were made before the third and successful spud was made with a modified guide base on 24 June 1978. Final position refers to this hole. The well was drilled with seawater and gel down to 820 m, with KCl polymer mud from 820 m to 1870 m, and with a fresh water/lignosulfonate mud from 1870 m to TD. Diesel and Protectomagic was spotted below 820 m, and from this depth the mud is reported to contain between 4 and 12 % oil. The well was drilled to TD at 3528 m, 91 m into the Early Jurassic Statfjord Formation.

Grey clays and claystone dominated the Tertiary except for the sands in the intervals, 989 to 1034m and 1205 to 1225m. In the Paleocene Balder Formation typical tuffaceous grey and red claystone were present and were also observed above and below the Balder. The Late Cretaceous Shetland Group was comprised of grey and brown claystone and siltstones with only minor sands and carbonates. The electric log pick of the top of the Early Cretaceous Cromer Knoll Group was taken at 3037.8 m. The Early Cr