In oil drilling fluids, HEC (Hydroxyethyl Cellulose) is mainly used as a viscosifier, fluid loss control agent, and suspension stabilizer in water-based drilling muds. It increases the viscosity of the drilling fluid, helping carry drilled cuttings to the surface and preventing solids from settling during circulation. At the same time, HEC provides good shear-thinning rheology, allowing the fluid to maintain high viscosity under low shear conditions while reducing pumping resistance under high shear conditions.
HEC also helps control filtration loss by forming a protective filter cake on the wellbore wall, which improves wellbore stability and reduces formation damage. In addition, it is compatible with salts and has good thermal stability within moderate temperature ranges, making it suitable for certain water-based drilling operations.
