30/7-7

General

The main objective of the well was to test the SE prospect on the 30/7 block. The objective of the well was to test possible sandstone reservoirs of Jurassic age, which were predicted to occur-in a large structure (150 km2) at the Kimmerian unconformity) located on the eastern flank of the Viking basin. The specific targets were possible turbiditic sandstone deposits within a thick Late Jurassic sequence, Middle Jurassic Brent Formation sandstones, and Early Jurassic Statfjord Formation sandstones. The well was planned to penetrate 50 m into the Statfjord Formation to approximately 5250 m.

The well is Reference Well for the Cook Formation.

Operations and results

The well 30/7-7 was drilled between December 16th 1978 and May 30th 1979 with the rig Treasure Seeker. It reached TD at 5127 m in the Early Jurassic/Late Triassic Statfjord Formation. 34.5% of the total rig time was lost time due to fishing, waiting on weather, waiting for replacement of equipment, and hole problems. The problem that had most serious consequences for the geological program occurred while reaming from 5114 m to 5125 m where the string got stuck. After 9.5 days of fishing for the drill string it was finally backed of at 4804 m. At this point it was decided to abandon the well leaving the fish in the hole. Before this happened the well had been logged down to 5122 m, but the fish made it impossible to test the Statfjord Formation sandstone. The well was drilled with Seawater/gel/hi-vis pills spotting LCM pills as needed down to 763 m and with a Spersene/XP20/Drispac mud with 0 % to 4% oil and LCM pills as needed from 763 m to TD.

Sandstone levels interbedded with shales were encountered below 2187 m in the Tertiary. They were mainly developed between 2216 and 2320 m. Some calcareous levels in the Maastrichtian limestones between 2531 and 2575 m could be considered as reservoirs. Limestone stringers in the Turonian calcareous section from