Preventing the formation of CaCO3 scales: molecular dynamic simulation study on the role of sodium triphosphate as scale inhibition

Abstract

To prevent CaCO₃ scaling in oil and gas wells, scale inhibition are commonly used. This study utilized the molecular dynamics method to simulate the crystallization of a high concentration CaCO₃ solution, with particular attention given to the influence of the scale inhibitor sodium tripolyphosphate (Na₅P₃O₁₀). Examination of the distribution of CO₃²⁻ surrounding Ca²⁺ indicated that P₃O₁₀⁵⁻ effectively hinders the interaction between CO₃²⁻ and Ca²⁺, leading to a decrease in the root mean square displacement and diffusion coefficient of ions. Based on the analysis of intermolecular interaction energies, it is evident that the binding energy between Ca²⁺ and CO₃²⁻ is estimated at around 550 kcal/mol, whereas the binding energy between Ca²⁺ and P₃O₁₀⁵⁻ is approximately 1000 kcal/mol. These data support the conclusion that P₃O₁₀⁵⁻ exhibits a higher affinity for Ca²⁺ binding, thereby impeding the formation of CaCO₃.