It is a high-cloud-point water soluble glycol ether designed for high salinity water-based drilling fluids. It can provide improved wellbore stability, lubricity, high temperature filtration control and reduced bit balling. "Cloud point" is the temperature where polyglycol additives change from being soluble (at low temperatures) to being insoluble (at higher temperatures). The cloud point can be reduced by increasing salinity or increasing the concentration of polyglycol. acts to reduce swelling of reactive clays by chemical interaction at the clay surface (below the cloud point) and by inhibiting filtrate invasion into the clay particles (above the cloud point). The cloud point of the mud system containing Glycol can be varied by alternating the salinity as required. Glycol is normally used in high salinity systems up to 150,000 ppm chloride because of its relatively high cloud point.