Investigation on the mechanism of wax deposition inhibition induced by asphaltenes and wax inhibitors

Abstract

This study is specifically concerned with the effect and mechanism of asphaltenes and wax inhibitors on the wax deposition characteristics of model waxy oil. According to the rheological and wax deposition test, the pure model waxy oil has a pour point higher than the pipe wall temperature, and the formed wax deposit exhibits the slowest aging rate and homogeneous wax deposit structure. Based on the DSC and rheological experiments, the solubility of wax crystals is hardly influenced by asphaltenes or wax inhibitors, but the decrease of oil viscosity and the weakened low-temperature gel structure induced by asphaltenes and wax inhibitors would increase the wax molecular diffusion coefficient and wax content in the wax deposit, which ultimately leads to a thinner and harder wax deposit. Moreover, based on the molecular dynamic simulation, the EVA molecules can be adsorbed on the asphaltene surface thus forming EVA-asphaltene composite particles, which can change the crystallization habit of wax molecules and the wax crystal micromorphology, thereby dramatically improving the crude oil rheology at low temperatures and inhibiting wax deposition. This work provides a comprehensive understanding of the wax deposition mechanism induced by asphaltenes and wax inhibitors, which helps to the well or pipeline operation safety and efficiency. • The solubility of wax crystals is hardly influenced by the asphaltenes. • Asphaltenes decrease the oil apparent viscosity thus increasing the molecular diffusion coefficient of wax molecules. • Asphaltenes decrease the gel structure strength thus increasing the wax content of the formed wax deposit. • EVA molecules can adsorb on the asphaltene surface to form EVA-asphaltene composite particles.