31/6-2 R

General

Well 31/6-2 R is a re-entry of well 31/6-2 gas appraisal well on the south-east periphery of the Troll East gas province. Well 31/6-2 was suspended at 2020 m after drilling through the main target reservoir (Sognefjord Formation) and into the Early Jurassic Drake Formation. The objectives for 31/6-2 R re-entry were to test the gas column in the Sognefjord Formation, and to drill on to the planned Triassic level.

Operations and results

Well 31/6-2 was re-entered (31/6-2 R) with the semi-submersible installation Deepsea Bergen on 31 July 1984 and drilled from 2020 m in the Early Jurassic Drake Formation to final TD at 2235 m in the Late Triassic Hegre Group. The well was drilled with lignosulphonate mud. Drilling went without significant problems. No cores were cut and no fluid samples taken in this well bore.

The well was permanently abandoned on 8 September 1984 as a gas appraisal.

Testing

Prior to testing a large amount of steel particles and rust, possibly caused by oxidation of casing, was circulated out of the hole. This caused several days lost time. The rust also created problems with valves in the Otis sub-sea test tree and the Pre-Gravel-Pack test string had to be pulled because of leakage caused by steel particles in the ball valve.

The well was tested from the interval 1506 m to 1510 m in the middle of the gas column in the Sognefjord Formation, first without gravel-pack and then with gravel-pack. The well flowed 276000 Sm3 gas/day to surface in the pre-gravel-pack test. In the gravel-pack test several acid-jobs were performed and the flow rate increased after each job. After the fifth and final acid-job the well produced gas at a rate of 851000 Sm3/day on a 1.5" choke.