30/9-13 S

General

The primary objective of the 30/9-13 S well was to prove hydrocarbon potential in the Tarbert Formation in the G-East prospect, south west of the Oseberg Field. The well should define fluid contacts in the prospect and test the sealing capacity of the eastern fault. The location was chosen to drill through untruncated Tarbert Formation, and it should leave a minimum of untested reserves up dip in order to establish the fluid contacts in the lower part of the Tarbert Formation.

As secondary objectives the well should test the resource potential within the Ness, Oseberg, Rannoch, Etive, Cook and Statfjord Formations. The well was planned deviated due to a very high amplitude reflection, resulting in a shallow gas

warning for a sand layer at 496 ± 10 m.

Operations and results

Wildcat well 30/9-13 S was spudded with the semi-submersible installation Vildkat Explorer on 5 May 1991 and drilled to a total depth of 4027 m in Early Jurassic Statfjord Formation sandstone. The well was drilled with seawater and hi-vis pills down to 1030 m, with KCl/polymer mud from 1030 m to 3031 m, and with Thermadrill/KCl/polymer mud from 3031 m to TD. The well was drilled vertical to the 13 3/8" casing shoe and was kicked off from there using a steerable motor. A maximum inclination of 31 ° was obtained at 1434 m. At 1483 m the steerable system was pulled and a drop assembly was run in hole to continue drilling. Intra Heather Formation Sandstone was encountered at 2959 m in the 12 l/4" hole before the planned 9 5/8" casing point had been reached. The well was plugged back and casing was set above the hydrocarbon-bearing interval. On drilling out of the casing the well was sidetracked down to the top of the Heather Formation at 2963 m. The greater part of the Heather Formation proved to be sand with a total net gas column of 28.5 m. A total oil reservoir zone of 77 m with a 60 m net pay zone was identified. A Free Oil Level