* ''Calcium-Based Mud''—Calcium-based mud systems maintain a desired amount of calcium in the water phase. The calcium concentration can be maintained by using [[gypsum]] (CaSO<sub>4</sub>) or lime [Ca(OH)<sub>2</sub>]. These muds are more inhibitive and can tolerate cement and [[anhydrite]] contamination better than a freshwater-dispersed fluid. However, their thermal limitation is somewhat reduced. | * ''Calcium-Based Mud''—Calcium-based mud systems maintain a desired amount of calcium in the water phase. The calcium concentration can be maintained by using [[gypsum]] (CaSO<sub>4</sub>) or lime [Ca(OH)<sub>2</sub>]. These muds are more inhibitive and can tolerate cement and [[anhydrite]] contamination better than a freshwater-dispersed fluid. However, their thermal limitation is somewhat reduced. |