Abstract: In view of the uncertainty of qualitatively describing wax crystal particles, their quantitative characterization method is discussed, and a distribution fractal model for wax crystals based on their volume characteristics is presented. Taking Nan Sanlian and Linyuan crude oil before and after adding flow improver in Daqing Oilfield as the case, their wax precipitation process and viscosity-temperature characteristics are tested by using rheological testing methods and image analysis techniques, and the microstructures of the wax crystals during their wax crystallizing are analyzed to determine the fractal dimension based on the wax crystal size distribution by using the NcMiVnt software, and then the influence of temperature and the flow improver on wax crystal fractal characteristics is discussed. The results indicate that the distribution fractal model can quantitatively characterize the wax crystal morphologies of the crude before and after adding the flow improver, the fractal dimension, volume and number of wax crystal particles deposited from the oil increase with temperature drops, so the low-temperature flowability of the oil becomes worse. While the crude treated by the flow improver, their wax crystal fractal dimensions increase significantly, but the wax crystal particle numbers reduce substantially. As a result, the low-temperature flow ability of the oil improves obviously.

Key words: wax crystal particle, fractal dimension, temperature, flow improver, waxy crude oil