7120/9-1

General

Well 7120/9-1 was drilled in the Hammerfest Basin. The primary objective of the well was to test sandstone reservoirs of Early to Middle Jurassic age at a location very close to the highest position of the prospective structure.

The well was to be drilled into sediments of Triassic age to a prognosed depth of 2180 m +100/-130.

Operations and results

Exploration well 7120/9-1 was spudded with the semi-submersible installation Treasure Scout on 25July 1982 and drilled to TD at 2300 m in the Triassic Snadd Formation. The 36" section was drilled with a 17 1/2" bit followed by a 36" hole opener. Low penetration rates were encountered due to the over-compacted nature of the clay formation together with the presence of numerous erratic glacial boulders. The hole had to be reamed 3 times before the 30" casing was set. After that drilling proceeded without major problems. The 36" section was drilled with mud left from the previous well (7117/9-1). The 26" section down to 760 m was drilled with seawater and prehydrated bentonite. From 760 m to 1651 m the well was drilled with gypsum/"Milpolymer 302" mud, and from 1651 m to TD the well was drilled with "Milpolymer 302".

The main reservoir was found hydrocarbon bearing from 1840.5 m (Top Stø Formation) down to the gas/water contact at 1904 m, eight meter into the Nordmela Formation. This interval consists of fine to medium, occasionally coarse sandstones with a few thin claystone stringers. RFT pressure recordings and sampling were performed over the interval. This gave a clear gas gradient of 0.084 psi/ft down to 1904 m with an underlying water gradient of 0.48 psi/ft. Weak to good shows were reported in sandstones in the interval from 1904 m in the lower part of the Early Jurassic and into the Triassic at TD. The water saturation in this interval ranged from 50-100% and based on log interpretation the hydrocarbons were assume