A modification of Pedersen's model for saturated crude oil viscosities using standard black oil PVT data

This paper presents a modification of Pedersen's corresponding states compo sitional viscosity model that enables viscosity prediction for black oil sy stems when there are no compositional data available. This model can be eas ily implemented in any reservoir simulation software, it can be easily tune d, and it provides better estimates of oil viscosity than the existing corr elations. Viscosity from 324 sets of differential liberation data consisting of 2343 observations covering a wide range of pressure, temperature, and oil densit y were used to develop the correlation which retains most of the functional form of Pedersen's model. These modifications include (1) use of n-decane as the reference fluid; (2) consider the oil mixture as a single pseudocomp onent with molecular weight and critical properties correlated to its densi ty; and (3) add a functional dependence to solution gas/oil ratio and gas-s pecific gravity. The average error over 2343 viscosity observations was 0.9 %. The model was tested against a second data set consisting of 150 observa tions and the average error was 0.7%. The predictions were compared with those predicted from the correlations of Khan et al. [SPE 15720 (1987)] and of Petrosky [SPE 29468 (1995)] that are applicable to the experimental conditions of our data sets. These average errors for these correlations were -28 and 4.9%, respectively, for the firs t data set; and -60.8 and -1.4% for the second data set. (C) 2001 Elsevier Science B.V. All rights reserved.