Calcium carbonate (CaCO3) crystallization is a complex operation due to the diverse thermodynamic and kinetic factors involved during the particle formation of vaterite, aragonite, and calcite. This article involves the experimental and computational study of CaCO3 crystallization in the presence of Mg2+, Ba2+, and Sr2+. Crystallization experiments were performed varying the Mg2+, Ba2+, and Sr2+ concentration, monitored by dynamic light scattering, scanning electron microscopy, and X-ray diffractometry techniques. The crystallization model includes the thermodynamic equilibrium, pathway, and kinetic rates associated with a populational balance. It was obtained that the Mg2+ inhibited vaterite nucleation and accelerated its transformation to calcite. The Ba2+ and Sr2+ ions accelerate both calcite growth and vaterite-calcite transformation rates. All external ions produced an increase in crystal size and a decrease in the total crystalline mass, albeit in different proportions. Simulation results with the developed model presented a good agreement with experimental data with an error of 12% per variable. Thus, the proposed model framework may be helpful for the evaluation of the calcium carbonate crystallization process as a practical tool to provide insight into the extensively experimentally studied effects of external ions on CaCO3 crystal populations.

This article summarizes initial efforts on the evaluation of the joint action of chemical inhibition and magnetic field to maximize the potential of scale mitigation in downhole conditions. This strategy is seen as a promising way to enhance flow assurance reliability in high cost deepwater wells where workover jobs are very expensive. This strategy is being considered as a good option for downhole applications where portions of the wellbore are not assisted by chemical injection or even as a redundancy which can attenuate effects of chemical injection failure. The calcium carbonate scale in the oilfield is typically controlled by chemical inhibitors, in several types and concentrations, depending on the saturation index related to the application. A magnetic field has the potential of retarding scaling of inorganic salts in oil production/water treatment systems. A preliminary assessment of the association of magnetic field and inhibitors to postpone carbonate scaling has been evaluated, based on tube blocking test method and two saturation indexes levels (2.8 and 3.03 – SSP Norm Scale). The reactor, with nominal diameter of 1/8", was operated under the total flow rate of 52 mL/min. (Re ≈ 800), the pressure of 50 kgf/cm2, temperatures of 40, 60, and 80 °C, using hydroxymethyl amino-di(methylene phosphonic acid) inhibitor type at different concentrations. The magnetic field employed was 1,6 Tesla. Results indicate that at given conditions, expressive delay can be achieved with the combination of the two techniques, while in other situations the system may need redesign. This study reveals an interesting potential of coupling two different mitigation strategies aiming different applications, such as spacing the necessity of squeeze treatments and optimizing surface treatment.