Drilling fluids are mixtures of natural and synthetic chemical compounds used to cool and lubricate the drill bit, clean the hole bottom, carry cuttings to the surface, control formation pressures, and improve the function of the drill string and tools in the hole. They are divided into two general types: water-based fluids and oil-based fluids. The type of fluid base used depends on drilling and formation needs, as well as the requirements for disposition of the fluid after it is no longer needed. Drilling muds are a special class of drilling fluids used to drill most deep wells. Mud refers to the thick consistency of the formulation.
Following are the functions of drilling mud:
⦁ To remove rock bit cuttings from the bottom of the hole and carry them to the surface
⦁ To overcome the fluid pressure of the formation
⦁ To avoid damage of the producing formation
⦁ To cool and lubricate the drill string and the bit
⦁ To prevent drill pipe corrosion fatigue
⦁ To allow the acquisition of information about the formation being drilled (e.g., electric logs, cutting analysis)
