In production and transportation of waxy crude oil as well as in practical Rheological studies of non-Newtonian liquids, it is very important to find and characterize its thixotropic properties. There are some ways to study this phenomenon, but nowadays the existing equations still can not quantifiably describe the time-dependent behavior of thixotropic liquids with acceptable accuracy using in this case an exponential or hyperbolic functions.

The authors have conducted the screening studies on rotational viscometer Rotovisco RV-20 with different kinds of waxy crude oils from JV "Vietsovpetro" fields offshore Vietnam. Based on the received experimental data and its analysis the authors have proposed a new equation showing a very good agreement between experimental and calculated data (the average deviation is less than 2%). The general time-dependence of shear stress at constant shear rate can be much more precisely expressed.

A new idea "the measure of thixotropicity" of liquids at given shear rate and temperature is also proposed to characterize the properties of thixotropic liquids.

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