Chemical Treatment of Rotary Drilling Fluids

Abstract

The desirable properties of rotary drilling fluid in the technique of boring oil wells are considered. An analysis of the problem of elimination of cuttings by differential settling with reclamation of the colloidal content of clay dispersions shows that viscosity should be lowered as much as possible when the density is held constant. It is demonstrated that lowering of viscosity results in a small lowering of pump pressure, even though the velocity of the mud-fluid is increased to maintain constant carrying capacity for cuttings. Several chemicals have been found that cause remarkable lowering of the viscosity of clay drilling fluids. Suitable adjustment of the concentration of caustic soda in these chemical reagents imparts desirable thixotropic properties to the clay dispersion. The theoretical results of this study are applied to some of the practical problems of oil-well drilling.