A Molecular Dynamics Workflow to Study the Dissolution of Paraffin Deposits Exposed to Organic Solvents

Abstract

Wax deposition remains one of the most persistent challenges in crude oil production and transport, often leading to flow restrictions, increased operational costs, and potential pipeline failure. While solvent-based methods are widely employed to dissolve paraffin deposits, the molecular-scale mechanisms governing dissolution kinetics remain poorly understood. To fill this knowledge gap, a framework based on molecular dynamics simulations is proposed and used in this work to quantify the interaction of various nonpolar solvents (commercial xylene, toluene, n-heptane, diphenylethane, and methylcyclohexane) with paraffin solids of varying compositions. Two representative wax models were considered: one composed exclusively of long-chain n-alkanes (nC27–nC42) and the other containing both short- and long-chain n-alkanes (nC7–nC42). The simulated solids exhibited structural features consistent with crystallographic experiments. Subsequent dissolution simulations revealed that aromatic solvents promote more efficient paraffin dissociation compared to aliphatic solvents, as observed by dissolution kinetics, consistent with field observations of faster wax removal using commercial xylene and toluene products. The simulation results are dependent on wax chain length, with short alkanes dissolving readily from the aggregates, and longer chains showing slower dissociation kinetics. Overall, this study provides an initial molecular-scale framework to rationalize wax dissolution processes. Through the analysis of simulation results, it is possible to extract new insights into mechanisms explaining differences in solvent performance for paraffin remediation.