34/7-8

General

Wildcat well 34/7-8 was drilled on the "C" structure south of the Snorre field area on Tampen Spur in the Northern North Sea. The Late Triassic - Early Jurassic reservoirs of the structure are tilted fault blocks dipping in a generally north westerly direction. The "C" structure is defined by a major west bounding fault with throws up to 350 m in the northwest, diminishing to 20 m at the southern end. The main objectives of the well were to test the quality and thickness of the Statfjord Formation and the Upper Lunde Formation. Further objectives were to test the fluid content of the structure and sealing effect of the "C" horst fault.

Operations and results

Well 34/7-8 was spudded with the semi-submersible installation Treasure Saga on 5 February 1986 and drilled to TD at 2766 m in the Late Triassic Lunde Formation. Problems with tight hole were experienced through several zones in the 17 1/2" section. At 1642 m the pipe stuck and had to be worked free. During plug and abandon operation of the combined cut and pull tool caused problems. After several attempts of cutting, the string parted in the section of drill collars. Fifty-seven m of drill collar, cut and pull tool, wellhead with casing strings, TGB and PGB were left on the seabed. Seabed clean-up operations were carried out in June 1986, after abandonment. The well was drilled with spud mud down to 439 m, with gel mud from 439 m to 870 m, with gypsum/polymer mud from 870 m to 2280 m, and with gel mud from 2280 m to TD.

Apart from the sandy Utsira Formation of Late Oligocene - Pliocene age, an Early Oligocene (1265 - 1350 m) and a Middle - Late Eocene (1445 - 1465 m) sandstone unit within the Hordaland Group, the Tertiary and Cretaceous proved mainly claystones. The Jurassic consists of reworked sandstone, a claystone rich Dunlin Group and alternating sandstones and claystones in the Statfjord Formation. The Triassic proved sandstones