25/10-1 R

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General

Well 25/10-1 R is a re-entry of well 25/10-1, which found strong shows in thin Early Eocene sands, but was suspended at top Paleocene level due to heavy autumn storms. The purpose of the re-entry was to test the Early Eocene sands and to extend the well into deeper Paleocene sands, which were anticipated to be oil-bearing.

Operations and results

Appraisal well 25/10-1 was re-entered (25/10-1 R) with the vessel Glomar Grand Isle on 9 July 1970. The re-entry well was kicked off at 1664 m in 25/10-1 and drilled to final TD at 2091 m in the Early Jurassic Statfjord Formation. No significant problems were encountered in the operations. The well was drilled with seawater/spersene XP-20, Splinex mud from kick-off to TD.

From kick-off down to 1747 m the well drilled the same lithology as the primary well. The underlying Paleocene section was composed of sands and shales, with the sand bed thicknesses ranging from about 4 to 40 m. These Paleocene sands were highly porous and permeable, but only the top 5 m had good oil shows and this section produced water only on wire line formation test. The Paleocene section rested directly on the Early Jurassic Statfjord Formation. Sands within the Statfjord Formation were of reservoir quality, but were water-wet with only streaks of non-fluorescing dead oil.

The section from 1731 to 1804.1 m was cored all through in five cores, with near 100% total recovery. The upper two of these (core #9 and #10) were partially overlapping with the lower three cores (core #6, #7, and #8) in well 25/10-1. A total of twelve wire line FIT samples were attempted and five of them were reported to contain formation fluid. FIT no 1 and 2 were taken in the Paleocene sands (Heimdal Formation) at 1789.2 m and 1778.2 m. These recovered only water and mud. The remaining successful FIT recovered hydrocarbons: FIT no 4 at 1760.8 m (Heimdal Formation) recovered gas and 4800 cm3 oil, FIT no 6 at 1762.4 m (Heimd