Paraffin is an inevitable composition in waxy crude oil, which has caused series of problems in the process of transportation, including increase of viscosity, deposition of paraffin etc. We have employed molecular dynamics (MD) simulations to study the effects of paraffin on the transport property and viscosity of waxy crude oil. Two models were constructed. One is the light oil model containing alkanes (72 hexane, 66 heptane, 78 octane, 90 nonane, 48 cyclohexane, 78 cycloheptane) and aromatics (78 toluene, 30 benzene) molecules. The other is waxy crude oil model consisting of light oil and 24.9% by weight of paraffin. The simulated paraffin molecules were chosen as n-hexacosane (C26H54) and n-octatriacontane (C38H78) molecules based on the analysis of experimental data on carbon number distributions. Diffusion coefficients of each type of molecule and systems viscosity in the temperature range from 293K to 318K will be discussed. When paraffin is added into the light oil, diffusion coefficients decrease and viscosity of the system increases. The lower the temperature, the larger the effects of paraffin on viscosity. The self-assembly of paraffin was also investigated for further understanding of changes in transport properties and viscosity. Aggregation of paraffin is observed in waxy crude oil. It is assumed that the paraffin clusters inhibit the movement of small molecules, the decrease of mobility cause increase of viscosity. The size of paraffin cluster increases with the decrease of temperature. The microscopic data obtained from MD simulations are conducive to reveal the influence of self-assembly of paraffin on properties of waxy crude oil, which is supposed to enrich theoretical foundation for the rheological property of non-Newtonian fluid. Finally, we discuss the influence of imposed magnetic field on the self-assembly of paraffin molecules and the overall viscosity of waxy crude oil.

Effects of self-assembly of paraffin on the transport property and viscosity of waxy crude oil

255th National Meeting (2018)

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