The Machar field is located in the Eastern Trough area of the UK North Sea. Well 123, a subsea well, was drilled and completed as an oil producer in March 1998 and brought onto production from the Lower Chalk formation in August 1998 upon commission of the production facilities. Water breakthrough was first detected in May of 2001 and despite subsequent intervention to shut it off, the water cut continued to increase until production had dropped off to 3000 BOPD by late 2005. The accompanying 65% water cut presented handling problems at the production facilities that necessitated the well being shut in until additional water handling capacity could be made available.

Additional reserves were present above the Lower Chalk formation in the Upper Palaeocene Sands, but to date they had not been fully evaluated and their potential could well have a significant affect on the future of the field. Therefore, in order to make up for the loss in production, it was decided to re-enter the well and re-complete it so that the Upper Palaeocene sands could be produced. At a subsequent time, when additional production facilities were available, the Lower Chalk could be brought back on stream automatically without further intervention.

In this paper, the authors will review the decision-making process that led to the re-completion, discuss installation planning and execution, and present the results achieved with this unique completion that was installed using an intervention vessel.

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