Rheology modifiers for drilling are chemicals that are added to drilling fluids to control their flow properties and improve their performance. Drilling fluids are used to lubricate and cool the drill bit, carry cuttings to the surface, and provide stability to the borehole. Rheology modifiers in general are used to adjust the viscosity, gel strength, and yield point of a fluid. They can be used to thicken the drilling fluid and prevent sagging or settling of the cuttings, or to thin the fluid and reduce the pressure drop across the drill bit.