ID: 394
OBJECTID: 394
wlbNpdidWellbore: 399
wlbName: 31/2-6
wlbHistory:

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
wlbHistoryDateUpdated: 2016-07-06T00:00:00