Role of a Nanocomposite Pour Point Depressant on Wax Deposition in Different Flow Patterns from the Perspective of Crystallization Kinetics.

Wax deposition is one of the core issues affecting flow assurance studies of crude oil pipelines, particularly with deep and ultradeep water conditions. Nanocomposite pour point depressants (NPPDs) provide a novel and effective strategy for inhibiting wax deposition and have recently attracted increasing research attention. Although recent advances have been made in understanding the performance and mechanism of NPPDs, the effect of flow pattern remains an open question. In this paper, deposition thicknesses of waxy oils with different flow patterns and NPPD dosages were obtained using a flow loop experimental device. It was found that the NPPD used in the current work can effectively inhibit the formation of wax deposition layers in different flow patterns. The Avrami model-focused beam reflectance measurement and polarizing microscope experiment method were used to characterize crystallization kinetics parameters and mesoscopic structure parameters of wax crystals. The consistency of results from Avrami equation fitting parameters, wax crystal morphology, and particle number supported the validity of crystallization kinetics analysis. The mechanisms of NPPD in different flow regimes were discussed. The inhibition of laminar and turbulent deposition layers by NPPD was attributed to the improvement of wax crystal morphology and the reduction of wax crystal number, respectively. This has important consequences for our understanding of the utilization and mechanism of nanocomposite pour point depressants.