Assessment of Common Oil Viscosity Correlations for Libyan Crude Oils

Abstract

Reservoir oil viscosity plays a key role in the design and optimization of injection/production strategies and surface facilities for efficient reservoir management. The direct measurement method to determine the viscosity of the reservoir fluid involves reservoir fluid sampling, which is costly and frequently unavailable. In the absence of experimentally measured properties of crude oils, the petroleum engineer must determine the properties from empirically derived correlations. The main aim of this paper is to test several well-known viscosity correlations against a new dataset collected from different Libyan crudes. Statistical analyses and graphical methods have been used simultaneously to evaluate the performance and accuracy of each correlation. For dead oil viscosities, none of the available correlations yielded satisfactory results and exhibited high errors; however, the Ng and Egbogah (1983) and Beggs-Robinson (1975) correlations have the lower errors with AAPE% of 31.18 and 33.66, respectively. For live oil viscosities, the Beggs-Robinson correlation (1975) proved to be more accurate than the others, with AAPE% of 20.17 and 24.96, respectively. Labedi (1982) and Khan et al. (1987) for undersaturated oil viscosity are the most reliable correlation equations among published correlations, with AAPE% of 3.01 and 3.60, respectively.