16/10-1

General

Well 16/10-1 was the first well drilled in block 16/10 operated by Norsk Agip. Among the various structures defined within block 16/10, the one called "Alpha", located in the southwestern area, was selected as the first one to be drill. Main reason for this choice was the presence of a deep basin (Witch Ground Graben) to the south west of the block, where the Viking Group shales was believed to have generated hydrocarbons since Cretaceous time. The tectonic evolution of the structure is probably of pre-Cretaceous age, well before hydrocarbon generation started.

The purpose of the well was to explore all main reservoirs down to Triassic. The primary targets were the Jurassic and Triassic sandstone units, expected at 2850 m and 2980 m, respectively. Prognosed TD was at 3175 m.

Operations and results

Wildcat well 16/10-1 was spudded 25 May 1986 by Dyvi Offshore A/S semi-submersible rig Dyvi Stena and drilled to TD at 3151 m in the Late Permian Zechstein Group. The well was drilled with Seawater and hi-vis pills down to 514 m, with KCl/Polymer mud from 524 m to 2565 m, and with lignosulphonate mud from 2565 m t TD. Drilling proceeded without any significant problems. Electrical logs were run already in the 26" section from 195 m. No shallow gas was encountered.

The Quaternary/Tertiary sequence, 2280.5 m thick, is represented by Nordland, Hordaland and Rogaland groups and is predominantly constituted by marine claystones. A 513.5 m Cretaceous section represented by the limestones of the Chalk Group and by the reddish marl and calcareous shales of the Cromer Knoll Group was penetrated. It was nearly a complete sequence except for two possible hiatus: the first in the Late Santonian and the second between the Cenomanian and the Aptian-Albian. The base Cretaceous Unconformity overlies the Late Jurassic shales of the Viking Group (top at 2794 m), which proved to have a thickness of 211 m. The top of the