The Ar-Sai waxy crude oils were taken as the research objects, and the viscosity reduction rates and the condensation point reduction rates were regarded as the evaluation indexes, the impacts of components content of the crude oils and carbon number distribution of waxes on the modification effect of EVA-type pour point depressant (PPD) were analyzed by using gray correlation analysis method. The oil wax was acquired by applying the extraction and separation techniques initially, then the structures and the lattice parameters of wax crystals before and after adding the PPD were studied by polarized light microscopy observation and x-ray diffraction techniques, the mechanism of pour point depression was discussed at last. The results indicate that wax content and the low carbon number wax have significant influences on the modification effect of PPD, while the impact of high carbon number wax is relatively small. Co-crystallization is the main mechanism of pour point depression, nevertheless, the impacts of the asphaltenes, resins, solid particles, and light components of the crude oils on the modification effect of the PPD cannot be ignored.

Conventional methods for pipeline transportation of heavy or extraheavy crude oils adopt heating, water blending, and dilution, and several methods are generally required to be used simultaneously to ensure normal transportation. However, how to determine the optimal transport boundary conditions for heavy oils is still one of the technical challenges. In this paper, the circulating piping experiment at different water contents (0–90 wt % with an interval of 10 wt %) and temperatures (65–90 °C with an interval of 5 °C) of three heavy oils from the Xinjiang oilfield is carried out. The apparent viscosity calculated from the experimental data of the circulating pipeline shows that when the water content is below the phase inversion point, the apparent viscosity increases and when the water content is close to the phase inversion point, the apparent viscosity increases nearly three times. Only when the water content is greater than the phase inversion point, the apparent viscosity shows a downward trend. Also, then, various viscosity prediction models with different independent variables, which mainly included temperature, water content, and dilution ratio, are selected and verified. Based on experimental data of six crude oils, a prediction model of the phase inversion point is established. Simultaneously, a method for determining the boundary conditions of heavy oils using the combined methods of heating, water blending, and dilution is proposed, while a set of simple decision diagrams of boundary conditions for heavy oil is also described. Finally, verified by the heavy oil pipeline of the Bohai LvDa oilfield, the gathering and transportation limits determined by this method are consistent with the operating parameters of the oilfield.

New stable aqueous foam was prepared, and the effects of different factors on its rheological property were systematically investigated.