Prediction of Sulfate Scaling Tendency in Oilfield Operations

Summary This paper presents a model for predicting the scaling tendencies of barium, strontium, and calcium sulfates resulting from the mixing of injected and formation waters and from temperature and pressure effects. The model also predicts competitive simultaneous coprecipitation of BaSO4, CaSO4, and SrSO4, where sulfate is the common ion, reflecting the precipitation of more than one sulfate mineral. The supersaturations and amounts of precipitation of the sulfates are calculated from their solubilities, which in turn are calculated by the Pitzer equation for electrolyte ion activity coefficients.