6507/7-1

General

License 095 was awarded to the Conoco/Statoil/Arco/Tenneco group in 1984 with Conoco as operator. The area, known as Haltenbanken, is a promising oil and gas province. It straddles two major Mesozoic structural features, the Trøndelag Platform and the Vøring Basin and lies along the western flank of the series of NNE-SSW faults, which separate them. The well was drilled on the A-prospect and was designed to test a major fault block. It was hoped to test oil bearing Middle Jurassic Sandstone at approximately 3898 m with a secondary objective at the Early Jurassic level.

The well is Type Well for the Lysing Formation.

Operations and results

Wildcat well 6507/7-1 was spudded with the semi-submersible drilling rig Nortrym on 10 August 1984 and drilled to TD at a depth of 4825 in the Early Jurassic Tilje Formation. The well was drilled with seawater and hi-vis pills down to 906 m, with gypsum/polymer mud from 906 m to 3803 m, and with gypsum/lignite mud from 3803 m to TD. Few problems were experienced whilst drilling the well. Some time was lost due to gumbo-associated problems. Mud was lost to formation while cementing the 13 3/8" casing, resulting in the top of cement being lower than planned. However this did not affect the strength at the shoe, as it was possible to make a good leak off test after drilling out. Tight hole problems were experienced on a bit trip from 3716 meters, with over pull recorded on the majority of subsequent trips. In addition a gain of 45 bbls of mud at 4360 meters indicated apparent under balanced conditions. Mud weight was progressively raised from 11.2 ppg at 4081 meters to 12.6 ppg by 4360 meters in response to this problem. A further increase to 13.1 ppg was made at TD due to logging difficulties associated with tight hole. The overall operation took 115 days from spud. Total depth was reached in 87 days, while an additional 28 days were used to log, test and abandon the well.