25/11-3

General

Well 25/11-3 was drilled ca 1.5 km south of the 25/11-1 Balder discovery well on the Utsira High in the North Sea. The objective was to test the reservoir continuity, sand correlation and possible thickening of the 25/11-1 Early Eocene oil sands in a South-easterly direction.

Operations and results

Appraisal well 25/11-3 was spudded with the vessel Glomar Grand Isle on 25 September 1970 and drilled to TD at 1858 m in the Early Paleocene Ekofisk Formation. North Sea fall storms were the cause of drilling problems experienced on this well. Cumulative lost time due to waiting-on-weather alone amounted to 23.3% of the total rig days. While at the depth of 1228 m, one of the severe storms necessitated pulling the bit into the 9-5/8 inch casing and hanging off the drill pipe. After the storm abated and the hang off tool recovered, it was found that the 5 inch drill pipe extension below the tool had parted, allowing the drill string to fall to bottom. Fortunately the fish was recovered in one run with an overshot. The hole was then drilled to TD with no further problems. Initial drilling from the seafloor to 396 m was with sea water and gel. Below 396 to a depth of 960 m, the mud system consisted of seawater, Spersene XP-20 Salinex. From 960 m to TD fresh water Spersene XP-20 mud was used.

The well penetrated the Utsira Formation and several Skade Formation sand units and then entered a ca 600 m thick section of shales belonging to the lower Hordaland Group before top Balder formation was encountered at 1711 m. Only thin Paleocene sands were encountered, and all were water wet without shows.

No conventional cores were cut in the well. Four FIT fluid samplings were attempted in the