25/10-1

General

Well 25/10-1 is located in the western part of the Balder Field in the North Sea. It was drilled on the crest of an Eocene structure up dip from the 25/11-1 Balder Discovery well, which had thin, oil-bearing Lower Eocene sands underlain by wet Paleocene sands. The purpose was to test this structure, and it was anticipated that 25/10-1 would find the Paleocene sands structurally higher and oil-bearing.

Operations and results

Appraisal well 25/10-1 was spudded with the vessel Glomar Grand Isle on 4 August 1969. The pipe got stuck at 1572 m. Fishing was unsuccessful and a technical sidetrack was made. The well was drilled to 1747 m (TD) into Paleocene shale belonging to the Sele Formation, where it was plugged and suspended due to severe winter autumn storms. A later re-entry would complete the well objectives. Initial drilling from the set floor to 997 m was with sea water and gel. From 997 m to TD, the mud system consisted of seawater/spersene XP-20, Splinex mud.

Down to top Oligocene at 1247 m the sediments were composed of soft clays and unconsolidated sands and silts with no indication of hydrocarbons. The lower part of the well section (Early Eocene, Balder Formation) was predominantly grey shale with very thin sands developed below a volcanic ash zone near the base. These sands had good oil shows and tested 24.8 - 25.1 deg API gravity oil on wire line formation tests in the re-entry well 25/10-1 R, but were too thin to be considered commercial.

The section from 1664.8 to TD in this well was cored all through in eight cores, with near 100% total recovery. A further five cores in partially overlapping lithology, were cut in the re-entry well 25/10-1 R. No wire line tests were performed in this well, but a number of wire line FITs, including fluid sampling, were taken in the re-entry well.

The well was suspended on 16 October 1969. It is classified as a well with shows.

Testing