Prediction of wax deposition and optimization of pigging intervals in shale oil multiphase pipelines

Abstract

To address the flow safety challenges caused by wax deposition in shale oil multiphase pipelines under low-temperature conditions and the difficulty of current wax deposition prediction models to adapt themselves to the complexity of multiphase flows, this study presents a multi-physics coupled wax deposition model and a pigging interval optimization method. By coupling a steady-state two-fluid model and thermodynamic equations, along with a wax deposition kinetics mechanism that accounts for molecular diffusion, deposit layer porosity, and shear stripping effects, a multiphase wax deposition model is developed. This model is capable of comprehensively predicting of flow regime, temperature loss, pressure drop, and wax deposition thickness in multiphase pipeline. The accuracy of the model is validated through comparisons with experimental data and OLGA simulations, and the model results are within 20 % of the experimental error. Additionally, an optimization method for pigging intervals is proposed, considering both environmental parameters and economic factors. The impacts of temperature and flow rate on pigging intervals are analyzed. The proposed model and optimization method provide a robust theoretical foundation for the safe operation and optimization of pigging in shale oil multiphase pipelines.