1/5-2

General

The Flyndre well (1/5-2) was drilled on a structural high situated in the Feda Graben of the North Sea close to the UK border. The principle objective horizons were the Paleocene and Jurassic sand sections which had produced oil in the UK 30/13-2 well and the NO 2/7-3 wells. It was estimated that at Paleocene depth the structure was an irregular dome about 4 miles in diameter, with 12 square miles of closure and 290 ft (88.4 m) of vertical relief while at Jurassic depth the structure was a NW-SE trending anticline 4.5 miles by 3.5 miles with 12 square miles of closure at 190 ft (57.9 m) of vertical relief. Planned TD was 15000 ft (4572 m), Triassic sands, or the Zechstein Group, whichever came first.

Operations and results

Well 1/5-2 was spudded on 19 October 1973, 15 m away from the original Flyndre well 1/5-1, which was junked at 491 m for technical reasons. Well 1/5-2 was drilled with the semi-submersible installation Ocean Viking. Total depth was set at 4287 m in Late Permian Zechstein salt. The well was drilled with seawater and hi-vis pills down to 494 m. The rest of the well was drilled with lignosulphonate mud.

The well had shows throughout the Paleocene and Late Cretaceous sections and four drill-stem tests were carried out.

The top sand in Paleocene at 2832 m (Forties Formation sand) produced oil upon testing. Mud log shows were present in the Danian, but testing proved the section to be tight and unproductive. A thick Late Cretaceous section was encountered with oil shows at the top of the Maastrichtian (Tor Formation) and in the Campanian (Lower Tor and Hod Formation) sections. Drill-stem t