Effect of Various Cations on the Formation of Calcium Carbonate and Barium Sulfate Scale with and without Scale Inhibitors

High pressure dynamic tube blocking tests have been conducted to determine the effect of iron (divalent and trivalent), calcium, magnesium, and sodium ions on the formation of calcium carbonate and barium sulfate scale with and without added scale inhibitors. Scale inhibitors were chosen to represent the three main functional groups used in commercial oilfield scale inhibitors: the phosphonate group (found in sodium diethylenetriaminepentaphosphonate), the carboxylate group (in sodium polyaspartate), and the sulfonate group (in sodium polyvinysulfonate). A fourth proprietary inhibitor with phosphonate and carboxylate groups was also used in some studies.