The effect of chloride, sulfate, and carbonate Tons on the electrochemical behavior of steel in a simulated concrete environment has been studied using alternating current (AC) and direct current (DC) techniques. Plain carbon steel acquires a passiva layer in uncontaminated saturated calcium hydroxide solutions. The addition of chloride, sulfate, and carbonate ions leads to a modification of the original passive film, and lowers the pH of the solution, leading to the breakdown of the passiva layer and an increase in the rate of corrosion.

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A new and reliable Oilfield Scale Prediction Model (OSPMod) has been developed and is presented. Unlike the available models which predict only scaling potential using thermodynamics and limited solubility data, OSPMod predicts the potential and deposition profile based on extensive thermodynamic and kinetic data. The model uses experimental solubility data in NaCl, MgCl2, CaCl2, and their mixtures, and in natural oilfield brines to determine the saturation index. Critical saturation indices beyond which scaling occurs have been established for the common oilfield scales (BaSO4, SrSO4, CaSO4 nH2O, and CaCO3). The model uses the flow characteristics and experimental kinetic data to predict the scale deposition profile from the bottomhole to the surface, once the critical saturation index is exceeded. The model has been developed as a menu-driven, user-friendly software. It is applicable to all the common oilfield scales and provides several input, computation and output options. Graphic presentation of results is a useful feature of OSPMod. The accuracy, reliability, and key features of the model are illustrated in the text with oilfield and test well cases.

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