Produced water quality is a function of the reservoir conditions, the fluid chemistry and the upstream process. The oil droplet size distribution in produced water is influenced mainly by choke valve pressure drop causing shear effects thereby droplet break down, and further the oil droplets ability to coalesce to larger droplets. Factors preventing coalescence include the droplets negative electrostatic charge, stabilization by surface active components and steric stability caused by fines. The larger the oil droplets in the produced water the easier they are to separate (Stokes' Law). Hydroflokk is a newly developed process for pre-treatment of produced water in order to optimize its separability. In this process oil droplets are subjected to combined chemical and mechanical action to accelerate coalescence and the formation of larger, more separable flocs.
The Hydroflokk system was developed by Norsk Hydro on behalf of the Troll Oil Unit Committee, to be qualified for installation on the Troll B platform in the North Sea. There the Hydroflokk system has been operated successfully since the installation in March 1996. The system has successfully been tested at several offshore platforms with a containerized test unit and has been incorporated in the produced water system for the Troll C platform to go on stream in 1999/2000.