1/6-3

General

Well 1/6-3 is located on the Albuskjell Field in the southern Norwegian North Sea. The primary objective was appraisal of reservoir development in the western part of the Albuskjell field. A Danian - Maastrichtian gas condensate field had previously been confirmed by two wells (A/S Norske Shell l/6-l and Phillips 2/4-9) drilled farther east along the WNW - ESE trending structure. Secondary objectives were to investigate Danian Chalk prospect and possible deeper prospects.

Operations and results

Appraisal well 1/6-3 was spudded with the jack-up installation Zapata Nordic on 12 April 1974. Three sidetracks had finally to be drilled, of which the second and deepest reached 3343 m in the Late Cretaceous Tor Formation. The first sidetrack was kicked off at 314 m after unsuccessful fishing (lost hole opener). The second sidetrack was kicked off at 3022 m when it was realised that a core point had been missed so that a Danian porous zone and 37 m of Maastrichtian had not been cored. Lost circulation and stuck pipe led to the third side track, which was kicked off at 2995 m. Further lost circulation problems and the discovery that there was a break in the casing at 3140 m finally led to abandonment of the well without investigating the deeper prospects. The well was drilled with seawater down to 417 m, with shale-trol/lignosulphonate from 417 m to 1221 m, with shale-trol/lignosulphonate and lime from 1221 m to 2500 m, and with lignosulphonate and lime from 2500 m to TD. A diesel/pipe lax pill was spotted at 314 m.

As prognosed, gas was encountered both in the Danian and Late Maastrichtian Chalk. Hydrocarbons were present from Top Ekofisk at 3110 m down to an OWC at 3289.7 m in the Tor Formation. The net thicknesses were respectively 91 and 45 m. The great thickness of the Danian reservoir was in contrast to the findings from wells l/6-l and 2/4-9, where only a thin hydrocarbon-bearing zone was present in an otherwise tight Danian.