Applied Problems in the Rheology of Structured Non-Newtonian Oils

*Gudret Isfandiyar Kelbaliyev, Sakit Rauf Rasulov and Dilgam Babir Tagiyev*

#### **Abstract**

The rheology problems of non-Newtonian oil, accompanied by the physical phenomena of formation and destruction of coagulation structures and aggregates, significantly affecting the flow are considered and analyzed. Also are considered issues of hydrodynamic interaction of particles leading to the formation of disordered structures, which significantly change the rheological properties of non-Newtonian oil. It has been noted that the formation of coagulation structures depends on energy dissipation, viscosity, stress or shear rate, and the size of the particles forming the structure. With increasing asphalt-resin content in the oil, the probability of particle collision increases, increasing the rate of formation of various disordered structures up to a framework that nullifies the rate of oil flow. Applied problems of rheology, including dissolution kinetics of asphalt-resinous substances in aromatic hydrocarbons and improving rheological properties of the oil, rheology of structured non-Newtonian oils in gas lift method of production, as well as possible ways to create new technologies for processing non-Newtonian oils were considered.

**Keywords:** rheology, non-Newtonian oil, coagulation structures, models, asphalt-resinous substances, kinetics, technology

#### **1. Introduction**

The world has huge reserves of heavy oils that show non-Newtonian properties, and their use is limited by a lack of efficient extraction, transport, and refining technologies.

Non-Newtonian oils are characterized by a fairly high content of asphalt-resinous substances and paraffinic compounds that are prone to coagulation structures and aggregates. This factor significantly affects the rheological properties of the oil, primarily its effective viscosity and diffusion, making its transport and storage difficult. At the same time, there are many methods of improving the rheological properties of oils required in the production, transportation, and refining of the latter. They are associated with improving temperature conditions, as well as creating efficient technologies using various chemical reagents that reduce the surface tension and viscosity of rheological fluids and many other factors that enable intensification of the extraction, transport, and refining processes. The flow of highly viscous fluids and dispersed systems with a high content of dispersed particles is characterized by certain

#### *Advances in Rheology of Materials*

complexities, mainly related to the non-linearity of the disordered structure and the properties of the carrier phase. Accordingly, the rheology of such systems, at present, can be classified as:


Analysis of the literature studies [1, 6, 11, 13–15] showed that the most widespread in engineering practice are rheological empirical or semi-empirical equations. For heavy viscoplastic oil, s the following rheological equations are the most acceptable: Bingham mod: *<sup>τ</sup>* <sup>¼</sup> *<sup>τ</sup>*<sup>0</sup> <sup>þ</sup> *<sup>η</sup>*•*γ*; Ostwald-de-Ville model: *<sup>τ</sup>* <sup>¼</sup> *<sup>k</sup>*0•*γ<sup>n</sup>* <sup>¼</sup> *<sup>k</sup>*0•*γ<sup>n</sup>*�<sup>1</sup>•*γ*; Hershel-Bulkley model (Hershel-Bulkley): *<sup>τ</sup>* <sup>¼</sup> *<sup>τ</sup>*<sup>0</sup> <sup>þ</sup> *<sup>k</sup>*0•*γ<sup>n</sup>*. In practical calculations, various modifications of these equations using are possible.
