Representation of the Viscosity of Alkanes as a Function of Temperature and Pressure Using a Vogel Type Equation

Abstract

High Pressure / Liquids / n-Alkanes / Viscosity Prior evaluation of the viscosity of oil field fluids according to pressure-temperature conditions is a fundamental factor in exploitation. The aim of this article is to propose a representative form of the viscosity as a function only of pressure-temperature variables and a parameter characteristic of the fluid, namely the molecular weight. This analytical expression applies to all the members of the same chemical family. It is based on known parameters and is consequently available without any additional experimental work. -This Vogel type analytical expression: Igq = A + B/(T-T,) has been developed from experimental results conccrning the viscosity of pure linear alkanes (n-Clo to n-Cls) at different temperatures (20-100°C) and pressures (1 -1000 bar) corresponding to the liquid state. The isobaric set [q =f'(T)] of the different alkanes considered has been reduced to a single master curve, by double translation, a technique used for polymer study. This procedure allows the dependence of parameters A , B and T, to be specified with respect to pressure and molar mass. Numerical verification of the proposed representation shows that the experimental values for pure substances have on average an accuracy of 3%. The method yields results which remain acceptable for binary and quaternary mixtures of these alkanes.