Viscosity and density play very important roles in oil production, transportation through pipelines, and oil recovery processes. The most common definition of heavy crude oil is crude oil with API gravity less than 20, according to the International Energy Agency (IEA) and US geological survey (USGS). Crude oil is classified as light or heavy oil based on different physical properties, such as molecular weight, viscosity, density, and API gravity. Recent developments in improved oil technologies have increased the demand for heavy oil in the international market. However, the proposed model significantly minimizes the relative error and increases the correlation between the predicted and experimental data compared with other published methods. It was found that it is not possible to generalize a correlation for the heavy oil viscosity using only API and temperature. The proposed model and the literature models were tested on heavy oil samples. The comparison between the experimental data and the predicted values indicated that the proposed model successfully predicted the experimental data with an average absolute relative error of less than 8 % and correlation coefficients ( R 2) of 0.97 and 0.92 at normal and high temperatures, respectively. Published correlations were also used to evaluate the experimental viscosity data. The accuracy of the experimental density data was determined using Standing and Katz method. Viscosity and density were measured in the temperature range from 20 to 160 ☌. A total of 30 heavy oil samples of different API gravities ranging from 11.7 to 18.8 were tested. In this study, heavy oil density was predicted from API and temperature, and then the predicted values of the densities were used in the second step to develop the viscosity correlation. The principal objective of this paper is to obtain exact models that can successfully predict these two important fluid properties covering a wide range of temperatures. However, no practical theory exists for the calculation of these properties for heavy oil at elevated temperatures. Viscosity and density are important physical properties of crude oil.
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