Several models are frequently used in describing the shear rate dependent viscosity of drilling fluids.&nbsp; Most of these models, like for example the Herschel-Bulkley model, have a purely empirical fundament.&nbsp; Another model, still empirical although it is based on physical principles, is the Quemada model.&nbsp; The model is constructed along the philosophy that structural units develop at lower shear rates.&nbsp; These structural units will be partially broken down when the applied shear increases.&nbsp;&nbsp;In the current work, drilling fluid rheological data are fitted both to the Herschel-Bulkley model and to the Quemada model.&nbsp; The development of the Quemada model and the calculation of each model parameter are presented.&nbsp; It is shown that the Quemada model fits measurements over a wider range of shear rates than does the Herschel-Bulkley model.&nbsp; It is described how to select the parameters of the Quemada model.&nbsp; Based on the knowledge of the difficulty of understanding the correct shear rate in presence of possible yield stresses, it is discussed how this can affect the Quemada model.&nbsp; Furthermore, the Quemada model does not open for a non-zero yield stress.&nbsp; Therefore, it is discussed how the yield stress is handled using a (very high) zero shear rate viscosity.&nbsp;Th Quemada model contains several parameters and is very complex compared to for example a Herschel-Bulkley fluid model.&nbsp; It is discussed how such a complex model can be applied for practical drilling fluid operations.&nbsp; Items in the discussion include evaluation of these parameter’s suitability for being correlated with thermodynamic quantities like pressure and temperature or with chemical content parameters like for example polymer concentration for water based drilling fluids or oil/water ratio for oil based drilling fluids.&nbsp;

Application of the Quemada Viscosity Model for Drilling Fluids

Paper Proceedings: https://asmedigitalcollection.asme.org/OMAE/OMAE2021/volume/85116

OMAE 2021

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