The water chemistry prevailing in the BP Amoco operated Miller field presents one of the harshest scaling environments in the North Sea. The high barium, moderate salinity brine, coupled to a relatively high bottom hole temperature produces a scaling environment that dictates the need for high concentrations of exotic scale inhibitor chemistry for downhole scale control. These high levels of inhibitor, typically 10-200 ppm, are particularly difficult to sustain over long production periods. This leads to a relatively short squeeze life and thus high well intervention frequency and deferred oil costs.

Vinyl sulphonate chemistry has been shown to be particularly effective at controlling scale deposition under Miller conditions. However, its retention characteristics are less than ideal, leading to short treatment life. A new chemistry has now been developed which realises the benefits of the vinyl sulphonate functionality whilst achieving significantly higher retention and thus the potential for longer treatment life. This has been achieved by incorporating a novel phosphorus containing species into the polymer matrix.

Laboratory studies suggest that the new inhibitor combines significantly improved performance with superior environmental properties. One field trial has already been completed and another is currently ongoing. The trials have already achieved a significant increase in squeeze life.

Results to-date indicate that operating costs can be significantly reduced through development of a novel chemistry designed to meet the specific needs of a particularly harsh scaling environment.

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