Paper: Joe Kirk, BJ Chemical Services

It has been reported in the literature that the presence of soluble iron significantly increases the minimum inhibitor level for effective control of calcium carbonate and calcium sulfate scales. When confronted with developing a scale inhibitor for application in water containing 500 milligrams per liter soluble iron, the prospects of finding a scale inhibitor were daunting. Because the produced water was near saturation, compatibility of the scale inhibitor was of concern. Also, it was required that the scale inhibitor should be compatible with any corrosion inhibitor, biocide, coagulants, polyelectrolytes, scavengers, etc., which could be present in the system. Presented are the details of the laboratory investigation leading to the development of two scale inhibitors for calcium sulfate. Included are both the mechanical and chemical evaluations. Also, a case history successfully utilizing one of the inhibitors is discussed.