Viscosity measurements of liquids under pressure by using the quartz crystal resonators
Résumé
A quartz crystal viscometer has been developed for measuring viscosity in liquids under pressure. It employs an AT-cut quartz crystal resonator of fundamental frequency 3 MHz inserted in a variable-volume vessel designed for working up to 80 MPa. Viscosity is determined by two methods from resonance frequency and bandwidth measurements along up to eight different overtones. The resonance frequency allows an absolute measurement of the viscosity but leads to an accuracy limited to 5% whereas the bandwidth technique which works in a relative way provides an accuracy of 2%. The techniques were tested by carrying out measurements in two pure compounds: heptane and toluene. Measurement results demonstrate the feasibility of the technique in this viscosity range. The apparatus was also used to determine the viscosity of n-decane with dissolved methane. The results obtained with these mixtures reveal the applicability of the apparatus for reservoir fluids study.
Mots clés
Absolute measurements
AT-cut quartz crystals
Bandwidth measurements
Dissolved methane
Fundamental frequencies
Measurement results
N-decane
Pure compounds
Quartz crystal
Quartz crystal resonator
Reservoir fluid
Resonance frequencies Engineering controlled terms: Bandwidth
Methane
Modulators
Natural frequencies
Paraffins
Quartz
Toluene
Viscometers
Viscosity
Viscosity measurement Engineering main heading: Crystal resonators