Rheological study on natural heteropolysaccharide based drilling fluid

Abstract

A tree gum which is mainly composed of natural heteropolysaccharides, namely PG gum, was presented. The rheological characteristics of PG gum based drilling fluids at different concentrations and aging temperatures were studied by means of a rotating rheometer. The effects produced by the addition of inorganic salts (NaCl and CaCl2) on the rheological properties of PG gum based drilling fluids were also studied. The results show that PG gum based drilling fluids investigated behaves as non-Newtonian shear-thinning fluids. With the increase of PG gum concentrations from 0.5% to 2.5%, the consistency coefficient increases while the viscosity behavior index decreases. The aging experimental data indicate that temperature has a slight effect on the rheological properties of PG gum based clay suspensions when the aging temperature is below 120 °C. Whereas, when temperature is above 120 °C, the rheological parameters of the suspensions, containing apparent viscosity, plastic viscosity and yield point, decrease significantly. The PG gum shows a better resistance to an increase in salinity or divalent cations concentration.