6306/10-1

General

Well 6306/10-1 was designed to drill the Skalmen prospect, a structural closure located at the northern apex of the Gossa High in block 6306/10. Amplitude anomalies was seen at 280-, 300-, 400-, 1200 to 1300-, and 2200- 2400 ms. The primary objective of the well was to test the hydrocarbon potential of Early Jurassic and Pre-Jurassic sequences, believed to be developed in a sandy facies of deltaic/fluvial origin. Secondary objective was to test potential reservoir developments in the Cretaceous and the Late Jurassic within dip-closure. A third objective was to test the hydrocarbon potential of Paleocene sands. The well should be drilled some 250-300 m into rocks of Pre-Jurassic age and would penetrate the primary objective some 300 m down-dip from the structural culmination.

Operations and results

Wildcat well 6306/10-1 was spudded with the semi-submersible installation Dyvi Stena on 7 September 1990 and drilled to TD at 3187 m in basement rocks. Shallow gas was not observed. Overcompacted sediments and boulders caused some problems, and the well had to be re-spudded several times. Bad weather caused some delay in the drilling procedure, as the string was temporary hung off several times. The well was drilled with Bentonite and seawater down to 610 m and with PAC/gypsum mud from 610m to TD.

The well encountered close to 150 m of Paleocene Egga sand at 1138 m. Some sand developments were seen also in an Intra-Kvitnos Unit at 1825 m and in a 7 m thick Lysing Formation at 1992 m. The well penetrated a hiatus from Aptian to Early Callovian at 2692 m. The Middle Jurassic section from 2692 m to 2980 m contained about 60 m net sand with relatively low porosities and poor permeabilities, based on petrophysical log evaluation. The logs also showed that this section was gas bearing. Shows were recorded in the Egga Informal unit from 1142 m to 1180 m, in sandstone stringers in the interval 1992 m to 2470 m in the Lysing and Lange F