Over a dozen successive selective water shut off treatments (SWSO) have been performed on an individual North Sea field. The target wells were vertical, cased, perforated producers in a mature, high scale potential asset in the UKCS. Reservoir temperatures were in excess of 121°C and permeability ranged from 100 – 1000 mD. Mention is also given to several other treatments performed in this mature field on wells with water rates up to 16,500 bwpd.

Treatments were generally bullheaded as part of a scale inhibitor squeeze intervention, being contained in the final portion of the over flush. Results were all positive and in one case reduced water production by up to 60%. Furthermore, oil production was stimulated by up to 250%. The non-hazardous, low concentration chemical treatments were developed for pumping from the surface to reduce water production without affecting hydrocarbon production. It is more generally applicable than previous SWSO systems as it can be applied from ambient temperatures up to 130°C and 20mD – 16 D.

This paper details the treatment design and pre-qualification experiments to a variety of field applications of a novel relative permeability modifier gel. Details are given regarding the pumping schedule, treatment well test data, and lessons learnt from the operations.

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