6507/12-2

General

The purpose of drilling the second exploration well offshore Mid-Norway was to test the whole stratigraphic sequence between the seabed and 5000 m or basement whichever came first, as specified in the licence agreement,

Vertical closures near base Jurassic, top Lower Triassic, and a possible Permian marker represented the primary targets. Any horizon below the mapped Near Base Jurassic reflector would, according to Saga's interpretation, also be closed and thus represent a possible trap.

Operations and results

Well 6507/12-2 was spudded with the semi-submersible installation Byford Dolphin on 9 June 1981 and drilled to TD at 5008 m in the Triassic Red Beds. When pulling out of hole after drilling the 17 1/2" to 1005 m a shallow gas kick was taken. The drill string got stuck m in the 8 1/2 " section at 3620 and could not be freed. The well had to be plugged back and sidetracked from 3347 m. The well was drilled with sea water and gel down to 354 m, with gel/gypsum mud from 354 m to 1005 m, with PAC/polymer/gypsum mud from 1005 m to 2522 m, and with salt saturated lignite mud from 2522 m to TD.

The well turned out to be dry except for traces of hydrocarbons in a few minor sand-streaks in the Upper Triassic Red Bed sequence. Correlation to the well 6507/12-1 demonstrated generally that all the layers were thinning towards the hinge of the platform. In the Triassic, two significant salt units were encountered, with a total thickness of 800 m, separated by more than 500 m claystones/shales. Two cores were cut. The first was cut from 1929.3 m to 1947.3 m, but nothing was recovered on the rig. The second was cut from 4975 m to 4985 m with 92% recovered. The FIT-samples were attempted through the liner and the 9 5/8" casing at two levels (3010 m and 3002 m), but build up pressure was not achieved. The fluid sample recoveries were respectively 560cc and 550cc, both composed predominantly of mud filtrate.</