This study investigated the effect of average carbon number and molecular/bonding characteristics of wax on wax appearance temperature (WAT) and wax crystal shape under microscope. Three samples of SAR, AS, and FAH from oil fields in southwestern Iran were analyzed. Their WAT values were measured using cross-polarized microscopy (CPM). The results showed that the average carbon number of the wax samples was in direct relation to WAT, with WAT increasing proportionately with increases in the average carbon number. The SAR sample with the highest average carbon number among the three samples showed a higher WAT than the other two. According to FTIR results, SAR and AS samples in their molecular structure, in addition to paraffinic compounds, slightly contain polar/naphthenic compounds. The presence of these structures in the wax molecule affected the interactions between the molecules of the wax and the interactions between the wax-asphaltene molecules, and increased the WAT. At 30oC below the WAT point, images taken from surface the oil samples were subjected to image processing. The SAR sample, which had the highest average carbon number, formed small, rod-shaped crystals, while the FAH sample with smallest average carbon number formed large, round crystals.


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