6610/7-2

General

Wildcat well 6610/7-2 is located on the Trøndelag Platform outside Mid Norway. The primary objective of the well was to test the hydrocarbon potential of Early Jurassic and Late Triassic sandstones. Secondary objectives were to gather information about the stratigraphy and hydrocarbon potential down to approximately 4200 m.

Operations and results

Wildcat well 6610/7-2 was spudded with the semi-submersible installation West Vanguard on 28 August 1983 and drilled to TD at 4215 m in the Triassic Grey Beds. Drilling operations were problematic and took 119 days more than programmed. Excessive reaming of tight spots had to be done during drilling of the 22" hole section. In all the four first hole sections a pilot hole was drilled before underreaming. Nineteen kg junk was recovered from the hole after drilling out of the 13 3/8" casing shoe. Several problems with stuck pipe occurred below 3000 m. At 3526 m the pipe was stuck and was backed off at 3315 m. A cement plug was set from 3292 to 3148 m and the hole was sidetracked from 3212 m. Severe problems with tight hole, was experienced down to 3361 m. The well was drilled with seawater and spud mud down to 701 m, with gypsum/lignosulphonate mud from 701 m to 2160 m. Due to expected salt beds below 2500 m the well was drilled with oil based mud from 2160 m to TD. The oil base used was a Norol product, "hvitolje", a low-aromatic mineral oil C13 - C20 distillate.

The well encountered several sandstone bodies, the first interpreted as the Egga Informal Unit in Paleocene. Earliest Cretaceous - Late Jurassic were not present in the well. At 1487 m the Early Jurassic Båt Group was encountered with massive and porous sandstone sequence. The Triassic interval 3473 - 4218 m also had some clean sandstone, especially in the upper part. Electrical logs and RFT pressure tests, however, proved all potential reservoirs to be water bearing. Organic geochemical analyses showed