Mud Composition

Mud Composition

Composition:
Phases

Phases of a Drilling Fluid

    Water (continuous) phase
    Reactive commercial clay solids
    Reactive formation (drilled) solids
    Inert formation (drilled) solids
    Inert commercial solids
    Soluble chemicals

Water phase

    Definition: The continuous (liquid) phase of the drilling fluid (mud)
    Can be fresh water, brackish water, sea water, saturated salt water, or another type of brine fluid
    Can be hard water containing a high concentration of calcium or magnesium

Fresh water
Usually available only on land locations
Advantages:
Commercial clays hydrate more
Most chemicals are more soluble
Disadvantages:
Formation clays hydrate  more, which can result in hole problems and damage to the producing zone
  Brackish water
Usually in a marine environment
Slightly salty
Higher calcium and magnesium than fresh water
Sea water
Chlorides and hardness varies
Chlorides in Gulf of Mexico 15,000 - 30,000 mg/l
Calcium in Gulf of Mexico 400 ± mg/l
Magnesium in Gulf of Mexico 1200± mg/l
Hardness in North Sea much higher
Saturated salt water
Used primarily to drill through large salt formations
Salt must be added to achieve saturation
Prevents hole enlargement due to leaching or dissolving salt from the formation
Leaching could result in hole problems and expensive mud and cement costs
Brine water
Usually used for clay (shale) inhibition
Potassium chloride (KCl)
Calcium Chloride CaCl2
Formates (Na+, K+)
Bromides
 Reactive solids
S.G. = 2.6, Density = 21.67 ppg
Commercial  clays
Sodium Montmorillonite or bentonite
M-I GEL
Attapulgite
SALT GEL
Formation clays (drilled solids)
S.G. = 2.6, Density = 21.67 ppg
Montmorillonite (swelling clay)
Illite (non-swelling clay)
Kaolinite (non-swelling clay)
Chlorite (non-swelling clay)
Gumbo Shale (combination of above clays)
Inert solids
Commercial
Barite (barium sulfate)
S.G. = 4.2, Density = 35 ppg
(M-I BAR)
Used to increase mud density up to maximum of 22 ppg±
Hematite (iron oxide)
S.G. = 5.0, Density = 41.67 ppg
Fer-Ox
Used to increase mud density up to maximum of 25 ppg ±
Calcium Carbonate
S.G. = 2.8, Density = 23.34 ppg
Acid soluble
Lo-Wate
Used to increase fluid density up to maximum of 14.0 ppg ±
Used as bridging agent in drill-in, oil and synthetic fluids
Lost Circulation Material
Material used to bridge off (seal) formations where whole mud is being lost to the formation
Nut shells (mostly pecan & walnut)
Mica
Fiber (wood, paper, plastic, etc.)
Formation solids
S.G. = 2.6 ±, Density = 21.67 ppg ±
Sand
Limestone
Dolomite
Soluble chemicals
Caustic Soda (NaOH)  pH 13.3
Caustic Potash (KOH)  pH 13.3
Lime [Ca(OH)2]  pH 12.4
Soda Ash (Na2CO3)  pH 11 - 11.5
Sodium Bicarb (NaHCO3)  pH 8.4
Zinc Oxide (ZnO)

Lignosulfonate (organic acid)
Spersene (chrome lignosulfonate)
Spersene CF (chrome-free lignosulfonate)
Chemical de-flocculant (mud thinner) adds anionic (negative) charges to the mud.
Lignite (organic acid)
Tannathin (lignite)
XP-20 (chrome lignite)
Chemical de-flocculant (mud thinner) adds anionic (negative) charges to the mud.
Neutralizes positive sites on the clays causing them to repel each other. 

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