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added Category:Methods in Exploration 10 using HotCat
==Purpose of fluids==
==Purpose of fluids==
An essential element of drilling a well is the drilling fluid or mud. Drilling fluids serve a number of functions:
An essential element of [[drilling a well]] is the drilling fluid or mud. Drilling fluids serve a number of functions:
* Removal of cuttings from the bottom of the hole
* Removal of cuttings from the bottom of the hole
Dispersed muds can be broken into two smaller categories: ''calcium-based'' and ''seawater muds'',
Dispersed muds can be broken into two smaller categories: ''calcium-based'' and ''seawater muds'',
* ''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.
* ''Seawater Mud''—In seawater muds, the upper limit for conventional dispersed fluids to function efficiently is 20,000 mg/L chlorides (which is the salinity of seawater). The cost for this type of system is slightly higher than that of a freshwater system. However, in offshore environments, this cost is offset by allowing muds to be run using native seawater rather than transporting in freshwater.
* ''Seawater Mud''—In seawater muds, the upper limit for conventional dispersed fluids to function efficiently is 20,000 mg/L chlorides (which is the salinity of seawater). The cost for this type of system is slightly higher than that of a freshwater system. However, in [[offshore rig|offshore environments]], this cost is offset by allowing muds to be run using native seawater rather than transporting in freshwater.
====Nondispersed muds====
====Nondispersed muds====
[[Category:Wellsite methods]]
[[Category:Wellsite methods]]
[[Category:Methods in Exploration 10]]