1. n. [Drilling Fluids]
One of several flow characteristics of a material, such as a drilling fluid, completion fluid, workover fluid or cement. Shear-stress measurements made at a minimum of two shear rates are needed to define the properties of these oilfield fluids. Three parameters are sometimes used to better define fluid behavior. "Rheological properties" most often refers to the Bingham plastic fluid parameters, PV (plastic viscosity) and YP (yield point), as measured by the direct-indicating rheometer. The power-law fluid model parameters, exponent (n) and consistency (k), apply to polymer muds, although the three-parameter Herschel-Bulkley model is a better fit to polymer muds. Brookfield viscometers measure flow properties at low shear rates to determine suspension and transport of cuttings in high-angle holes.