| We all know that the content, the shape and the structure of the precipitated wax crystals are the major factors which are very important to crude oil rheology. The macroscopic rheological of crude oil is just affected by heat and shear conditions through affecting the shape and the structure of wax crystals. Therefore, Artificial waxy oil and crude oil's microscopic characteristics are studied comprehensively in this paper combining with theoretical basis and experimental study. The relation between macroscopic rheological of crude oil and microscopic characteristics of wax crystals in the low temperature condition is also further studied in this paper. In this paper, the relation between wax content and temperature during cooling process of different waxy crude oil were mesured by Differential Scanning Calorimeter, the exothermic and crystallization characteristics of waxy crude oil during gelation process was investigated, and get the wax precipitation of waxy crude oil at different temperatures according to experimental data. Combined with the small amplitude oscillatory shear mode of rheometer, studied the storage modulus, loss modulus, loss angle changes during the gelation process of waxy crude oil. Through the rheological measurements, combined with the exothermic and crystallization characteristics of waxy crude oil during the gelation process, explore the relation between viscoelastic parameters and precipitated wax crystals. Established the relationship between micro-structure fractal dimension, the amount of wax precipitation and the the viscoelastic parameters, indirectly get the micro-structure fractal dimension of waxy crude oil, then established the relationship between macro-rheological properties of waxy crude oil and microscopic characteristics of wax crystals. In addition, measured the yield stress of waxy crude oil, indicated the exponential relationship between yield stress and precipitated wax crystals mass fraction. To deeply reveal the gelation mechanism of waxy crude oil, hoping to provide theoretical basis of safety, economic operation and the shutdown and restart for the heating pipeline transportation. |
