Laboratory evaluation of a new, selective water control treatment and its implementation in a North Sea well

A new weak gel consisting of a non-ionic, high molecular weight polysaccharide and an organometallic activator was developed for harsh reservoir conditions. A first field application was performed on a candidate well in an oil field in the German North Sea tidelands in June 1992. The treatment had to be designed for the entire range of the perforated interval. The polymer solution was readily injectable and the activator was added to the last quarter of the injected volume. The treatment was considered successful as the initial increased water-cut could be maintained at a level of 65%, the overall production rate being comparable to that before treatment. However, the desired reduction in water production was not achieved, presumably because formation permeability was higher than estimated. A laboratory post-implementation evaluation was conducted to find out whether a possible further treatment with a stronger gel might be feasible. The results indicate that formulations yielding stronger gels would still be selective and easily injectable and would show a far greater water control potential.