EXPERIMENTAL INVESTIGATION OF THE RHEOLOGY OF WHITE OIL FOR OIL-BASED DRILLING FLUIDS.

The rheological properties of white oil used as the base for drilling fluids were investigated at 4, 10, 20, 30, 50 and 100°C, shear rates ranging from 0 s-1 to 1000 s-1 and at atmospheric pressure and 3.5 MPa. The results revealed the rheological behaviour of white oil followed that of typical Bingham plastic fluids. When the shear rate increased, the apparent viscosity decreased markedly in the lower shear rate range (< 200 s-1), and as the shear rate increased it tended to exhibit Newtonian behaviour. Shear stress was linearly related to shear rate which fit into a Bingham plastic model. The effect of temperature on viscosity was quantified through modelling (Arrhenius equation), while the influence of pressure was examined by comparing the rheological behaviour of white oil at pressures of 0.1 MPa and 3.5 MPa. This study indicated that plastic viscosities at the higher pressure were generally higher than at the lower pressure, and the effect was more noticeable at lower temperatures. [ABSTRACT FROM AUTHOR]