8/3-1

General

Wildcat well 8/3-1 was the first exploration well to be drilled in Norwegian waters. The chosen location was northwestern part of the Danish Norwegian. The well was proposed to investigate the largely unknown stratigraphic sequence and lithologies in a virgin area on an attractive, representative seismic structure. Although the seismic feature was based on low-density reconnaissance control, the structure qualified for testing in terms of vertical and areal closure and inferred thickness of sediments. The well site location was thought to lie on the east flank of the Tertiary "Viking" basin, but on the west flank of a Mesozoic sub basin. The position and delineation of older basins was uncertain, although Permian? salts of sufficient thickness to flow were recognized as probably present at depth. Interpretation of data from a seismic grid with about 7 Km line spacing indicated a regionally high, west-dipping, normally faulted block to be present. The well location was sited near the crest of the highest step faulted block. A diapiric Zechstein? salt plug was interpreted to be present, to the east on the down side of the principal fault block. The salt could have partially intruded along the fault plane, up through the Kimmerian horizon."

Operations and results

Well 8/3-1 was spudded with the semi-submersible installation Ocean Traveller on 19 July 1966 and drilled to TD at 3015 m in Caledonian schists. While pulling out of the hole to pick up a core barrel at a depth of 296I m the pipe stuck at 1660 m, and was pumped free with seawater. The hole began caving immediately. Extensive caving over the interval 1320 m to 2030 m lead to bridging, stuck pipe, and logging problems. Eighteen rig-days were spent to cure the problems by reaming and raising the mud weight and to log the section in various logging attempts. The hole was eventually cased to 2963 m. No further problems developed. From sea bed to 277 m the initial dri