Sound Velocity Studies of Pipeline Oils As a Function of Viscosity, Density And Water Content
Authors: Verrall R.E. , Heal G.A. , Dyer K.L. 
Published: March 2010

Measurements of velocity of sound in crude oil samples taken from a pipeline have been made as a function of oil temperature and added amounts of water and diluent (toluene). In the case of low concentrations of water-in-oil, the experimental sound velocities show a linear dependence on wt % of added water. For the diluent-in-oil systems the experimental sound velocity can be predicted over a wide concentration range of diluents by assuming an ideal mixing law for the sound velocities of the individual components. It is observed that the sound velocities for a number of the water-free oils show a strong dependence on the source of the oil. Of further interest is the observation of a good correlation between the measured viscosity and density properties with the measured sound velocities for the oil samples as obtained from the pipeline. These preliminary results suggest some potentially important deliverables. In particular, that rapid and frequent on-line monitoring of the sound velocity property of an oil or oil mixture may provide accurate estimates of:viscosity;density;wt % diluent-in-oil for conditions &lt; 50 wt % added diluent; andwt % water-in-oil for conditions &lt;10 wt % added water.

Introduction

In this paper we report the results of measurements of sound velocity, viscosity and density properties of several crude oils as a function of temperature in the range 15–35 °C. As well the sound velocities in mixtures of water-in-oil and diluent (toluene)-in-oil have been measured as a function of the concentration of water or diluent added to the oil.

Analyses of these data have led to empirical correlations of sound velocity in the oil with either the density or the viscosity of the crude oil. Empirical correlations are also presented for sound velocity in water-in-oil and diluent-in-oil mixtures with the composition (wt %) of water or diluent added to the oil. Several of these correlations have a basis in the theory of acoustic wave propagation. The results show that the measurement of sound velocity may be used to estimate several important physical properties of crude oils.

On a practical level, this study demonstrates the potential for the use of sound velocity measuring devices that would be capable of providing continuous monitoring of the density and viscosity of oils flowing through pipelines. Also, under controlled conditions sound velocity measurements could serve as an effective means of continuously monitoring water and diluent content of pipeline crude oils. Since sound velocity monitors are already in use for the monitoring of flow rates, it is nm unforeseeable that in the future their use could be extended to carry out analyses of pipeline oil mixtures.

Experimental

The oil samples in this study were obtained from the Interprovincial Pipeline Company, Regina Station, on two separate occasions over a period of one year. In total, 55 different oil samples were collected from 18 different batches representing 10 different sources of oil from Western Canada. Preliminary analysis for the determination of water and solid contents of the oils was performed on all samples by the Saskatchewan Research Council (Petroleum Research Unit, Regina).