3/7-5

General

Well 3/7-5 was drilled on the Lemen structure, a fault bounded, salt induced trap located in the centre of the Søgne Basin in the North Sea. The Primary objective of the well was to test sandstones of the Sandnes and Bryne Formations. Secondary objectives were to evaluate the prospectivity of other possible reservoir levels (Late Cretaceous Chalk and Paleocene sandstones) within structural closure and thereby evaluate the charge potential of the local Søgne Basin hydrocarbon kitchen.

Operations and results

Wildcat well 3/7-5 was spudded with the semi-submersible installation Dyvi Stena on 6 December 1991 and drilled to TD at 3666 m (3637.8 m TVD) in the Late Permian Zechstein Group. The well was drilled efficiently, but some problems with deviation and logging was encountered. The hole was practically vertical down to TD in the 12 1/4" section at 3085. The 8 1/2" section was however drilled with close to 20 deg deviation all through to TD, leading to ca 27 m difference between measured and true vertical depth at final TD. Due to hole problems no wire line logs were run between 2198 m and 3085 m in the 12 1/4" section. The 8 1/2" section was eventually logged to 3575 m, 90 m above final TD, but only after several logging attempts and a check trip. The well was drilled with spud mud and viscous pills down to 610 m, and with seawater/gypsum/polymer mud from 610 m to TD.

Above the objective Sandnes / Bryne formations there were no evidence of producible hydrocarbons, although it should be stated that this could not be completely confirmed by logs because a significant section could not be logged with wire line logs. Top Sandnes Formation was encountered at 3379 m and top Bryne Formation at 3436 m. FMT pressure plot indicated a water gradient throughout the Sandnes / Bryne reservoir. Petrophysical evaluation gave no indications of hydrocarbons in the cleaner parts of the reservoir but, there was some indi