Five scale inhibitors were evaluated to reduce the scaling tendency of seawater from the Subiya region in Kuwait co-mingled with three different formation waters. The seawater to formation water ratios for each of the water combinations under study were chosen to reflect the worst case
conditions, as predicted from a computer compatibility study. Static jar tests were performed prior to the dynamic scaling tests in order to select an appropriate dose concentration for the inhibitors. Each inhibitor was tested at three different doses at reservoir temperature of 180°F (82°C). Results of the jar tests and dynamic scaling tests indicated that the most effective scale inhibitor is an aqueous blend containing polyacryate and ethylene glycol at a dose concentration of 5 to 7 ppm. Keywords: scale inhibitor, jar test, dynamic scale test, seawater, formation water.