A Unified Model for Predicting Barite Scale Inhibition at the Conditions of Geothermal Productions

Abstract

Calcite scaling is one of the most prevalent scaling problems in the geothermal systems due to the high concentrations of Ca2+ and HCO3- in the geothermal fluids. The scaling problem could significantly affect the operation efficiency by damaging the wells and utilization systems. Compared to physical removal and chemical dissolution treatment, the addition of scale inhibitors is one of the most convenient, efficient and cost-effective method to control the calcite scale. In this study, a novel laser apparatus (for experiments under 100 °C with 1 atm pressure) and high-pressure reactors (for experiments higher than 100 °C with the pressure higher than 1 atm) are used to test the calcite formation and inhibition kinetics at various conditions corresponding to the geothermal sites in Boye and Lankao, China. Based on the testing results, a kinetic model is developed to predict the formation and inhibition kinetics of calcite with inhibitors polycarboxylic acid and phosphates at these geothermal related conditions, as well as the minimum scale inhibitor concentrations needed. The model developed will provide critical instructions (e.g. the severity of the scaling problems, the inhibitor dosage amount, etc) to the calcite control in the geothermal sites.