7117/9-2

General

Exploration well 7117/9-2 is located on the Senja Ridge west of the Tromsø Basin. The primary objective of wildcat 7117/9-2 was to test sandstone or limestone reservoirs of Early Cretaceous age in a well-defined offset bounded structure within the Senja Ridge (the Lom structure). An alternative model suggested that the primary objective was sandstones of Middle Jurassic age and the secondary objectives were sandstone reservoirs of Triassic age or older. The well was planned to be drilled to a total depth of 5000 m and serve as the deep commitment well on the block.

Operations and results

7117/9-2 was spudded with the semi-submersible installation Treasure Scout on 7 May 1983 and drilled to a total depth of 5000 m in Early Cretaceous (?Aptian) clay stone. Nineteen rig days were lost due to strike, otherwise no major problems occurred during drilling of this well. The well was drilled with seawater and hi-vis pills down to 358 m. with seawater and bentonite from 358 m to 915 m, and with gypsum / polymer from 915 m to 2500 m. From 2500 m the mud was dispersed to a lignosulphonate mud, which was used for the remaining well down to TD.

Pleistocene deposits were encountered down to 400 m and underlain by a thick sequence of Pliocene clays down to 1092 m. Paleocene rocks continued down to 1345 m followed by a thin sequence of Campanian (1380 m to1396 m) and Late Albian to Early Cenomanian (1400? - 1410) deposits. The lowermost strata penetrated by the well consisted of a thick, poorly defined sequence of claystones. The upper sequence from 1625 m to 3440 m is of Albian to Aptian age. In the lower section, few identifiable fossils were recorded and preservation was poor. The Lom structure was penetrated in a down flank position at approximately 3375 m. The structure proved to consist of Early Cretaceous silty claystones of probable Aptian age and bounded by fractured dolomites. No rocks with reservoir properties were encountered in