15/9-16

General

Well 15/9-16 was drilled on the Sleipner Øst discovery in the southern Viking Graben of the North Sea. The primary objective was to delineate the hydrocarbon accumulations in the Heimdal Formation on the gamma structure. Sandstones of Jurassic/Triassic age were secondary objectives. It was the fourth well drilled on this structure.

Operations and results

Appraisal well 15/9-16 was spudded with the semi-submersible installation Deepsea Saga on 28 June 1982 and drilled to TD at 3120 m, 52 m into the Permian Rotliegendes Group. The 9 5/8" casing had a leak at 522 m. It was squeezed twice with cement before it held a reduced pressure. Otherwise, no significant problem was encountered in the operations. The well was drilled with gel/seawater spud mud down to 515 m, with gypsum/lignosulphonate mud from 515 m to 2652 m, and with a seawater/lignite/lignosulphonate mud from 2652 m to TD.

Top Heimdal was encountered at 2378 m. It contained gas and condensate, but was thinner than expected. Pressure data indicated a gas/water contact at 2434 m. The logs showed a sharp increase in water saturation at 2428 m. Weak oil shows were recorded on cores between 2418 m and 2427.5 m. The prognosed sandstones of Jurassic/Triassic age were not present at this location. Fair shows were recorded on cuttings in evaporites at 3014 m, at top Zechstein Group level. No shows were recorded on sidewall cores from the same level.

A total of 113.5 m of core (98% recovery) was cut in seven cores in the interval 2382 to 2498 m. cores were cut and no wire line logs were run in the well. An RFT fluid sample was taken at 2380 m (good recovery), while attempts to sample at 2411m, 2413 m, and 2426 m gave poor