35/8-1

General

Well 35/8-1 is located on the Marflo Spur, ca 30 km west of the Gjøa Field in the northern North Sea. The principal objective of this well was to test the hydrocarbon potential of sandstones within the Jurassic section beneath the Late Cimmerian Unconformity.

Operations and results

Wildcat well 35/8-1 was spudded with the semi-submersible installation Sedco-704 on 27 July 1980 and drilled to TD at 4345 m in Late Triassic sediments of the Statfjord Formation. The well was drilled without significant technical problems, but two well kicks occurred .After penetrating the Jurassic sand reservoir at 3516m a sudden rapid gas increase was noted, but due to mechanical problems could not be measured. This increase was associated with a quantity of reservoir fluids entering the borehole. During controlling of the kick, a large proportion of gas was vented and light low gravity yellowish oil recovered from the mud. A second kick with formation fluids entering the well bore was taken after coring core no 3 at 3549.6 to 3567.1 m. The well was drilled with seawater and viscous slugs down to 890 m, with gypsum/Lignosulphonate mud from 890 m to 2196 m, and with KCl/polymer mud from 2196 m to TD.

The top sections down to Top Rogaland Group, Balder Formation at 1683 m contained a number of sands and sandy intervals. From top Rogaland and throughout the Cretaceous section down to top Draupne Formation at 3186 m the lithology was mainly claystone and limestone. The heather Formation came in at 3200 m with two thin Intra-Heather Formation sandstones at 3219 and 3250 m. Heather Formation shale continued down to the Brent Group at 3516 m. Frequent sandstones were penetrated in the Brent and Dunlin Groups, and in the Statfjord Formation. </p