This paper presents a concise investigation of viscoplastic
behavior of a novel lightweight biopolymer drilling fluid. Eight different
rheological models namely the Bingham plastic model, Ostwald–De–Weale
model, Herschel–Bulkley model, Casson model, Sisko model, Robertson–Stiff
model, Heinz–Casson model, and Mizhari–Berk model were
used to fit the experimental data. The effect of concentration of
clay, glass bubbles, starch, and xanthan gum on the fluid rheological
properties was investigated. Results show that the fitting process
is able to successfully predict the rheological behavior of the fluid
very well. The predicted values calculated from the best selected
model are in a good agreement with the experimental data both in low
and high (1500 s–1) rate of shear. The result also
indicated that the presence of clay, glass bubbles, and xanthan gum
have significantly changed the fluid behavior, while the presence
of starch has not. Results also showed that all of the tested fluid
seems to follow pseudoplastic behavior except for the following three
tested fluids: one is fluid with the absence of clay, second and third
is fluids with no glass bubble or xanthan gum, respectively. The first
fluid tends to follows a Newtonian behavior, while the other two fluids
tend to follow dilatants behavior.