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| ==Purpose of fluids== | | ==Purpose of fluids== |
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− | 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: |
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| * Removal of cuttings from the bottom of the hole | | * Removal of cuttings from the bottom of the hole |
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| * ppg = pounds per gallon (United States) | | * ppg = pounds per gallon (United States) |
− | * S.G. = specific gravity (dimensionless) (international) | + | * S.G. = specific [[gravity]] (dimensionless) (international) |
| * psi/ft = pounds per square inch per foot (uncommon) | | * psi/ft = pounds per square inch per foot (uncommon) |
| * pcf = pounds per cubic foot (California) | | * pcf = pounds per cubic foot (California) |
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| 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'', |
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− | * ''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. |
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| ====Nondispersed muds==== | | ====Nondispersed muds==== |
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| [[Category:Wellsite methods]] | | [[Category:Wellsite methods]] |
| + | [[Category:Methods in Exploration 10]] |