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Alexander Busch, Velaug Myrseth, Paal Skjetne, Milad Khatibi, Stein Tore Johansen
Rheological characterization of polyanionic cellulose solutions with application to drilling fluids and cuttings transport modeling
Appl. Rheol. 28:2 (2018) 25154 (17 pages)
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In petroleum drilling, aqueous Polyanionic Cellulose solutions (PAC) are often used as a drilling fluid model system in experimental
laboratory studies to investigate cuttings transport. Cuttings transport refers to the transportation of drilled-off solids
out of the wellbore. In these studies, PAC solutions are typically assumed to behave purely viscous, i.e. they do not show timedependent/
thixotropic and/or viscoelastic properties. In this study, a rheological characterization of PAC has been performed
in combination with an evaluation of time scales characterizing the fluid to verify the conventional assumption of a purelyviscous
fluid. It is found that PAC solutions are generally not purely viscous: They feature viscoelastic behavior on time scales
of the order of 0.01 to 1 s, such as normal stress differences, as well as thixotropic behavior on larger time scales of the order
of 10 to 1000 s because of their polymeric microstructure. If simplified to a purely viscous fluid, the degree of uncertainty in
representing the measured apparent shear viscosity may increase by an order of . 75 to 90 % depending on the relevant time
scale. When obtaining flow curves, a sufficiently long measurement point duration (sampling time for a particular torque
reading) is required to ensure that the liquid microstructure has reached its dynamic equilibrium at the desired shear rate.
Due to their polymeric nature, PAC solutions feature Newtonian viscosity plateaus at both low and high shear rates. For modeling
purposes, the application of a Cross/Carreau material function is recommended because it both best describes the flow
curve data and minimizes extrapolation errors compared to the conventionally used Power Law material function.
► Cite this publication as follows:
Busch A, Myrseth V, Skjetne P, Khatibi M, Johansen ST: Rheological characterization of polyanionic cellulose solutions with application to drilling fluids and cuttings transport modeling, Appl. Rheol. 28 (2018) 25154.
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