New Viscosity Correlations for Saturated and Undersaturated Arabian Crude Oil

Abstract

Newly developed correlations for undersaturated and saturated Arabian crude oil viscosities were developed and tested using two datasets of experimental measurements. The datasets cover 71 data points of measured undersaturated viscosity (μundersaturated), pressure (P), temperature (T), bubble point pressure (Pb), gas specific gravity (γg), crude oil API, viscosity at bubble point pressure (μb) and dead oil viscosity (μd) and 79 data points of saturated viscosity (μsaturated), pressure (P), temperature (T), bubble point pressure (Pb), gas specific gravity (γg), crude oil API, viscosity at bubble point pressure (μb) and dead oil viscosity (μd), gas–oil ratio (GOR) and gas solubility (Rs). The viscosity models were developed utilizing 80% of the datasets using forward step-wise regression method. The selection of the independent variables was carried out using graphical alternating conditional expectation program (GRACE), a nonparametric regression method, which produce and generate plots for the optimal transformation of the dependent and independent variables. The program also performs low- and high-degree polynomial curve fit up to six-degree polynomial to create the desired model. The models’ accuracy was validated using the rest of the datasets, and their efficiency was tested against some commonly used correlations utilizing average absolute relative error, average relative error and cross plots. The developed models proved to be very efficient and they accurately predicted the experimental undersaturated and saturated crudes viscosities with average absolute relative errors of 1.79% and 5.89%, respectively.