Drilling fluids are critical to maintaining well control and wellbore stability throughout the drilling operation. In addition, they suspend cuttings while not circulating and transport them to surface while circulating to optimize drilling operations. They also clean, cool and lubricate the bit. Drilling fluids also isolate the surrounding formations by developing a tight filtercake across permeable sections. Drilling fluids may be water base or non-aqueous based. These fluids are selected and designed based on geologic conditions and directional and geometric requirements.