8/10-2

General

Well 8/10-2 was drilled on the Sørvestlandet High about 20 km east of the Ula Field. The primary objective of the well was Jurassic sandstones expected to be 122 m thick. Secondary objective was Paleocene sandstones.

Operations and results

Wildcat well 8/10-2 was spudded with the semi-submersible installation Nortrym on 5 February 1980 and drilled to TD at 2997 m in the Late Permian Zechstein Group.

The first samples to the surface were from Miocene - Oligocene. They were badly contaminated with cement from the casing shoe at 461 m. First clean formation samples were collected at 503 m and they consisted of a soft grey brown clay with minor amounts of fine to medium grained sand and occasional fossil frogs. This gave way at 570 m to a totally argillaceous section, and soft grey-brown, slightly calcareous, claystone was found. This became the dominant lithology down to the 13 3/8" casing point at 1198 m. After casing point, cement contamination of samples occurred for about 10 m. The claystone gave way to a grey-green-brown, soft, sticky clay, which had occasional traces of carbonaceous material. Top Hordaland Group is set at 1265 m. At 1471 m a thin hard white limestone occurred with an associated drop in drilling rate from 61 m to 46 m per hour. Background gas also decreased during this interval. After 1494 m the dominant lithology became soft grey-brown clay, some sections of which were slightly calcareous. Occasional fossil fragments and pyrite nodules were also found in this section. There was a slow increase in the claystone content and by 1801 m a light grey claystone had become the dominant lithology. This claystone was moderately hard, slightly calcareous and micro micaceous; traces of dolomite and shelly fragments were also found. By 1951 m the soft clays had disappeared completely and were replaced by light grey and dark brown claystones, both soft to firm, the light grey claystone being non-calcareous and the