16/7-5

Well 16/7-5 is located ca 10 km east of the Sleipner Øst field in the North Sea. The primary objective was to test potential gas bearing Jurassic/Triassic sandstones.

Operations and results

Wildcat well 16/7-5 was spudded with the semi-submersible installation Zapata Ugland on 2 July 1984 and drilled to TD at 2900 m in the Triassic Smith Bank Formation. Due to turning of the permanent guide base the 30" casing had to be re-landed. No other major problems occurred during drilling. The well was drilled with gel/sea water down to 170 m, and with seawater/lignosulphonate gel from 470 m to TD.

The ?Jurassic/Triassic (Skagerrak Formation) was encountered at 2594, underlying an interpreted one-meter layer of Draupne shale. A 306 m gross / 120.5 m net (22% average porosity) sequence of sands was penetrated. No significant hydrocarbon shows were encountered while drilling the well. Electric log analysis also confirmed that the Jurassic/Triassic Sandstone (primary objective) was water bearing. RFT pressure measurements and samples suggested the possible presence of minor amount of gas in the upper part (2594 m to 2642.6 m) where the pressure gradient was lower than the water gradient (below 2662.5 m). However, the pressure readings were scattered in this interval and very much subject to interpretation.

One core was cut from 2590 to 2603 m (2596 - 2612.5 m logger's depth) in the top of the target sands in the Skagerrak Formation. Three successful RFT fluid samples were taken. The first sample, at 2691 m, recovered "2800 cc. of light brown fluid, mainly mud filtrate and mud, no gas, no fluorescence". The second, at 2806.5 m, recovered "8600 cc. of clear medium brown fluid, mainly mud filtrate with a few cc's of gas. The fluid had no odour or taste but it had a very pale bluish white fluorescence". The third, at 2603 m, recovered "8700 cc. of none clear (turbid) fluid + few cc's of gas. The fluid had no odour or tast