The paraffin crystals can aggregate and precipitate when the oil temperature declines below the wax appearance temperature (WAT) of the waxy crude oil. However, the aggregation behaviour of paraffin crystals during the process of crude oil production and transportation is not well revealed. This study concentrates on using fractal dimensional analysis to elucidate the aggregation behaviour of paraffin crystals in shearing fields. A set of microscopic experiments was recently performed to capture the basic information of the paraffin crystal images in different conditions. A methodology for characterizing paraffin crystal aggregation was then developed, and the blanket algorithm was introduced to compute the fractal dimension of aggregated paraffin crystals. The results indicate that the aggregation behaviour of paraffin crystals is closely related to temperature and shearing experienced by the waxy crude oil. The aggregation behaviour would be intensified with the reduction of temperature and the decrease of shearing effect, and it appears to be a wider fractal dimension distribution at lower temperature when the same shear rate range is employed. The lower fractal dimensions are at high temperature and strong shear action, the weaker nonlinear characteristics of paraffin crystals aggregation structure are, and thus the potential paraffin deposition would be inhibited during waxy crude oil production and transportation. The methodology developed in this study is beneficial to optimize the flow assurance operations in single-phase and multiphase pipeline transportation for waxy crude oils, and the results are expected to lead to a better understanding of paraffin crystallization and deposition mechanism.

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