Predicting Calcium Carbonate Scaling in Tubular Reactors: A Thermodynamic and Kinetic Model with Experimental Data Validation

This paper presents a thermodynamic and kinetic model for simulating calcium carbonate scaling in a tubular reactor under varying saline composition, temperature, and flow rate. Simulation results are compared with experimental data obtained from a tubular reactor developed by the IPT and Petrobras. A mathematical model based on thermodynamics and crystallization kinetics is developed using experimental data from a custom-designed tubular reactor. This reactor enables the direct measurement of deposited mass along its length, as well as particle size distribution and polymorphic composition, with or without CO₂ addition. The model calculates the solubility of three carbonate polymorphs to determine their sequential appearance following Ostwald's step rule, and its crystallization kinetics are modeled using a population balance approach that accounts for nucleation, growth, agglomeration, and polymorphic transformation. A series of experiments were performed under diverse conditions—including two distinct water compositions, varying test durations, and different flow rates—to validate the model. Overall, the simulation yielded average relative errors of approximately 8% for total deposited mass, 12% for deposition percentage, and 5% for deposit particle size predictions. These results indicate that the model effectively captures the influence of key operational parameters—such as temperature, residence time, CO₂ addition, and flow rate—on calcium carbonate scaling behavior. Consequently, the proposed model demonstrates robustness and reliability as a predictive tool for designing effective scaling mitigation strategies in downhole applications. These findings underscore the importance of incorporating operational variables into the design of oil and gas equipment. The novelty of this work is twofold: it introduces an experimental system that enables direct measurement of scaling variables along a tubular reactor, and it presents a thermodynamic and kinetic model capable of accurately simulating calcium carbonate precipitation and scaling under conditions relevant to the oil and gas industry.