Unified scaling model for viscosity of crude oil over extended temperature range

Abstract

The viscosity of crude oil is an important physical property that largely determines the fluidity of oil and its ability to seep through porous media such as geological rock. Predicting crude oil viscosity requires the development of reliable models that can reproduce viscosity over a wide range of temperatures and pressures. Such viscosity models must operate with a set of physical characteristics that are sufficient to describe the viscosity of an extremely complex multi-phase and multi-component system such as crude oil. The present work considers empirical data on the temperature dependence of the viscosity of crude oil samples from various fields in Russia, China, Saudi Arabia, Nigeria, Kuwait and the North Sea. For the first time, within the reduced temperature concept and using the universal scaling viscosity model, the viscosity of crude oil can be accurately determined over a wide temperature range: from low temperatures corresponding to the amorphous state to relatively high temperatures, at which all oil fractions appear as melts. A novel methodology for determining the glass transition temperature and the activation energy of viscous flow of crude oil is proposed. A relationship between the parameters of the universal scaling model for viscosity, the API gravity, the fragility index, the glass transition temperature and the activation energy of viscous has been established for the first time. It is shown that the accuracy of the results of the universal scaling model significantly exceeds the accuracy of known empirical equations, including those developed directly to describe the viscosity of petroleum products.