New Viscosity Correlations for Saturated and Undersaturated Arabian Crude Oil
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RESEARCH ARTICLE-PETROLEUM ENGINEERING
New Viscosity Correlations for Saturated and Undersaturated Arabian Crude Oil Othman R. Bin Abdulwahab1 · Abdulrahman A. AlQuraishi1 · Naif B. Alqahtani1 Received: 18 January 2020 / Accepted: 24 April 2020 © King Fahd University of Petroleum & Minerals 2020
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 (γ g ), 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 (γ g ), 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 lowand 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. Keywords Oil viscosity · Saturated · Undersaturated · Correlation · Regression analysis
1 Introduction Crude oil viscosity is an important physical property. Based on oil type, it is classified into dead, saturated and undersaturated viscosities. Many correlations were developed to predict crude viscosity, and these correlations are generally categorized into those that utilize oil field data such as API gravity, reservoir temperature, saturation pressure and solution gas–oil ratio or those referred to as empirical and semi-empirical models that use some other parameters that are not included in the first category. The parameters include reservoir fluid composition, pour point temperature, molar mass, boiling point and acentric factor as well as critical temperature [1].
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Naif B. Alqahtani [email protected] National Center for Oil and Gas Technology, King Abdulaziz City for Science and Technology, P.O. Box 6086, Riyadh 11442, Saudi Arabia
Empirical correlations are an effective and quick mean for viscosity prediction, and many models have been proposed. Beal [2] in his study develo
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