The article presents the results of laboratory study of the stability of the rheological parameters of oil mixture passing through a pump, and transported through the Atyrau – Uzen - Samara main pipeline. As an object for research we used two batch oil mixtures that differing in properties: Buzachi and Mangyshlak oil mixtures selected inlet T. Kasymova pumping station. The Mangyshlak oil mixture is characterized by a high content of waxes, which causes a high pour point temperature. The Buzachi oil mixture is characterized by a high content of resins and, accordingly, a high density. Results of mixtures modeling and studying showed, the highly paraffinic Mangyshlak oil is main component that affects the processes of structuring and, consequently, thixotropic properties of Buzachi-Mangyshlak oil mixtures. There were observed the most typical curves for thixotropic fluids at temperatures corresponding to or bordering on the fluidity loss temperature of the oil mixture - a gradual increase in the shear rate leads to shear deformation and destruction of the structured oil dispersed system, but with a decrease in the shear rate, a gradual restoration of the structure occurs. Highly solidifying Buzachi-Mangyshlak oil mixtures have thixotropic properties, due to which the structure and rheological properties of oil can be restored after prolonged and significant deformation effects, such as the passage of oil through a pump. In this case, the introduction of a depressant additive not only leads to a decrease in the rheological parameters of the oil mixture, but also contributes to a reduction in the time of the thixotropic response of the oil-dispersed system to shear effects. The study of the influence of the composition, depressant additives, temperature, and deformation conditions on the rheological and thixotropic properties is of great importance in the study of the possibilities of regulating the rheological parameters of anomalous oils. In addition, the obtained data are necessary for carrying out thermal-hydraulic calculations and determining the conditions for safe oil pumping.
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