An assay method to determine mineral scale inhibitor efficiency in produced water

• A method to determine the scale inhibitor inhibition efficiency is developed.
• The method is effective in both laboratory prepared and real field produced water.
• The method features low LOD, applicability on various inhibitors, and low cost.

This paper presents an easily-implemented assay method designed to detect mineral scale inhibitors, especially at low concentrations, in oil and gas produced water. The scale inhibitor concentration is determined using standard addition method, based on a semi-empirical linear relationship between scale inhibitor concentration and the logarithm of scale induction time. If a water sample contains only one scale inhibitor, this method will measure this inhibitor concentration directly. If multiple scale inhibitors are present, this method will detect their total scale inhibition efficiency. The method has successfully detected seven representative scale inhibitors at 0.3, 0.5, 1.0 mg/L in two laboratory prepared produced water samples. It has also been applied to scale inhibitor detection in real produced waters from oil field. This method features extremely low detection limit (0.05 mg/L inhibitor), applicability on a wide variety of scale inhibitors, and being easy to implement. By giving accurate determination of scale inhibitor efficiency, this method could enable better scaling control.