Effect of octadecyl methacrylate-maleic anhydride-vinyl acetate-styrene pour point depressant on wax crystal morphology of crude oil

Effect of octadecyl methacrylate-maleic anhydride-vinyl acetate-styrene (OMVS) pour point depressant on wax crystal morphologies in crude African and domestic oils was observed through micropolariscope. The commonly used OMVS pour point depressant could significantly affect the wax deposition rate and the crystal morphology. The wax crystals in the crude oils transformed from irregular rod-like or flake-like into well-dispersed micro-spheres with smaller size due to increase of the OMVS. The crystal numbers in the African and domestic crude oils increased from both less than 100 to more than 1300 and 1700 by means of PLM, respectively. The wax crystals with surface area 5-50 (jim2in the crude oils increased from less than 10% to more than 90%, and those with surface area 150-250 μm² in the African crude oil and 100-200μm² in the domestic crude oil decreased from more than 60% to less than 1%. The relation of OMVS pour point depressant dosage, average surface area of wax crystals and magnitude of OMVS depression could be determined by nonlinear regression, and results were in accordance with the experiments.