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Arild Saasen, Jan David Ytrehus
Rheological Properties of Drilling Fluids - Use of Dimensionless Shear Rates in Herschel-Bulkley Models and Power-Law Models

Appl. Rheol. 28:5 (2018) 54515 (10 pages)

An approach of Nelson and Ewoldt [Soft Matter 13 (2017) 7578] to create a viscosity model of the Herschel-Bulkley type in order to use only parameters with the potential of containing fluid information has been extended to be applied to drilling fluids using current industry standard procedures. The commonly used Herschel-Bulkley consistency parameter k is found inadequate in describing fluid properties properly as it has a unit dependent on n. Hence, the model is not optimum for digitalisation. The Herschel- Bulkley model is re-written and base its parameters directly on the yield stress and the additional or surplus shear stress at a pre-determined shear rate relevant for the flow situation to be considered. This approach is also applicable for Power-Law models.

Cite this publication as follows:
Saasen A, Ytrehus JD: Rheological Properties of Drilling Fluids - Use of Dimensionless Shear Rates in Herschel-Bulkley Models and Power-Law Models, Appl. Rheol. 28 (2018) 54515.

Arild Saasen, Helge Hodne
The influence of vibrations on drilling fluid rheological properties and the consequence for solids control

Appl. Rheol. 26:2 (2016) 25349 (6 pages)

Removing drilled cuttings from the drilling fluid flowing out of an oilwell is essential for obtaining good drilling conditions. Currently this solids control process is performed by use of shale shakers and vacuum devices. Throughout the last decades, the design and performance of the primary solid control devices have changed significantly. Flow through screens is strongly dependent on the rheological properties of the drilling fluid. Drilling fluids with high extensional viscosity seldom have a very strong gel structure, and are generally not affected equally much by vibrations. This explains why solids control is more difficult using a KCl/polymer water based drilling fluid than using an oil based drilling fluid. This article focuses on describing how the drilling fluid viscous properties alter when being exposed to vibrations like those on primary solids control devices. It is based on theoretical analysis, and rheological studies in the laboratory. The solids control efficiency resulting from using different screen configurations is outside the scope of this article, as this topic requires a higher focus on separation technology.

Cite this publication as follows:
Saasen A, Hodne H: The influence of vibrations on drilling fluid rheological properties and the consequence for solids control, Appl. Rheol. 26 (2016) 25349.


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