NORWAY · WELLBORES · NPDID 399
31/2-6
Exploration · Appraisal · P&A · Oil/gas · A/S Norske Shell · Troll · PL 054
31/2-6 is an appraisal exploration wellbore in the North Sea, drilled by A/S Norske Shell, entered Jul 21, 1981, to 1,760 m in the Fensfjord Fm.
Discovery 31/2-1 (Troll Vest) · On the map →
- 1,760
- m total depth · 1,754 m vertical
- 343
- m water depth
- Jul 21, 1981
- entered · completed Oct 17, 1981
- Fensfjord Fm
- at total depth · Middle Jurassic
- 123.7
- m of core in 9 cores
- 73
- °C bottom-hole temperature
SODIR FACTPAGES · RECORD UPDATED NOV 4, 2026 · RELEASED OCT 17, 1983
On file for this wellbore
What the Directorate holds from this wellbore. Each opens the section that lists it.
Drilling
- Drilling facility
- BORGNY DOLPHIN · Semisub steel
- Drilling days
- 89
- Kelly bushing elevation
- 25 m
- Maximum inclination
- 1.25°
- Drilling permit
- 296-L
- Licensing round
- 4
- Plugged and abandoned
- —
- Core samples available
- Yes
- Cuttings samples available
- Yes
- Position · ED50
- 60.90377° N, 3.64709° E
- Hydrocarbons in
- Sognefjord Fm · Late Jurassic
Well history
WRITTEN BY THE NORWEGIAN OFFSHORE DIRECTORATE
General
Well 31/2-6 is located in a fault block north-east on the main Troll structure, approximately 8 km NNE of 31/2-3. The main objective of the well was to test the north-eastern margin of the Troll structure and to prove hydrocarbon communication between block 31/2 and 31/3. The well location was picked to test the oil zone in a good sand reservoir. A second objective was to get reliable geologic tie to the seismic reflectors to allow for accurate lateral extrapolation of well data. Planned TD was 2500 m in Triassic sediments.
The well is Reference Well for the Sele Formation.
Operations and results
Appraisal well 31/2-6 was spudded with the semi-submersible installation Borgny Dolphin on and drilled to TD at 1760 m in the Late Jurassic Formation. The 9 5/8" casing collapsed at 771 m and was cut and retrieved from 760 m. As a result of this, well 31/2-6 was not deepened to the Triassic. The well was drilled with seawater gel down to 614 m and with KCl polymer mud from 614 m to TD.
Well 31/2-6 proved a similar hydrocarbon accumulation in this northern fault block area to that of the main field accumulation tested by wells 31/2-1,2,3 and 4. The well encountered the Sognefjord Formation at 1492 m. The Formation held a 79.4 m gross gas column underlain by a 10.3 m oil column. The GOC at 1571.4 m and the OWC was at 1582.2 m. Well 31/2-6 confirmed the overall interpretation of the flatspot as a direct hydrocarbon indicator. Oils shows were recorded on cores from 1504 m to 1601 m. In addition, cuttings gave patchy shows in the interval from 1710 m to 1758 m. Sidewall cores from this interval did not confirm shows in the latter interval.
Coring commenced at 1504.4 m and terminated at 1632.05 m, within the Sognefjord Formation. Thus 127.65 m of core was cut from which 123.65 m (97%) was recovered. An RFT gas sample was taken at 1518 m as a backup until samples could be obtained from the subs
Around this wellbore
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About this data
Norwegian Offshore Directorate (Sodir) FactPages, mirrored nightly and used under the Norwegian Licence for Open Government Data (NLOD). Depths are metres along the wellbore from the kelly bushing unless a row gives its own unit; older cores are filed in feet. A zero the Directorate files for an unmeasured pressure, density, or temperature is shown as a dash.
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