Mud Composition
Composition:
Phases
z Phases of a Drilling Fluid
z Water (continuous) phase
z Reactive commercial clay solids
z Reactive formation (drilled) solids
z Inert formation (drilled) solids
z Inert commercial solids
z Soluble chemicals
Composition:
Water phase
z Definition: The continuous (liquid)
phase of the drilling fluid (mud)
z Can be fresh water, brackish water, sea
water, saturated salt water, or another
type of brine fluid
z Can be hard water containing a high
concentration of calcium or magnesium
Composition:
Fresh water
z Usually available only on land locations
z Advantages:
z Commercial clays hydrate more
z Most chemicals are more soluble
z Disadvantages:
z Formation clays hydrate more, which
can result in hole problems and
damage to the producing zone
Composition:
Brackish water
z Usually in a marine environment
z Slightly salty
z Higher calcium and magnesium than
fresh water
Composition:
Sea water
z Chlorides and hardness varies
z Chlorides in Gulf of Mexico 15,000 -
30,000 mg/l
z Calcium in Gulf of Mexico 400 ± mg/l
z Magnesium in Gulf of Mexico 1200±
mg/l
z Hardness in North Sea much higher
Composition:
Saturated salt water
z Used primarily to drill through large salt
formations
z Salt must be added to achieve saturation
z Prevents hole enlargement due to
leaching or dissolving salt from the
formation
z Leaching could result in hole problems
and expensive mud and cement costs
Composition:
Brine water
z Usually used for clay (shale) inhibition
z Potassium chloride (KCl)
z Calcium Chloride CaCl
2
z Formates (Na , K )
+ +
z Bromides
Composition:
Reactive solids
z S.G. = 2.6, Density = 21.67 ppg
z Commercial clays
z Sodium Montmorillonite or bentonite
z M-I GEL
z Attapulgite
z SALT GEL
Composition:
Reactive solids
z Formation clays (drilled solids)
z S.G. = 2.6, Density = 21.67 ppg
z Montmorillonite (swelling clay)
z Illite (non-swelling clay)
z Kaolinite (non-swelling clay)
z Chlorite (non-swelling clay)
z Gumbo Shale (combination of above
clays)
Composition:
Inert solids
z Commercial
z Barite (barium sulfate)
z S.G. = 4.2, Density = 35 ppg
z (M-I BAR)
z Used to increase mud density up to
maximum of 22 ppg±
Composition:
Inert solids
z Hematite (iron oxide)
z S.G. = 5.0, Density = 41.67 ppg
z Fer-Ox
z Used to increase mud density up to
maximum of 25 ppg ±
Composition:
Inert solids
z Calcium Carbonate
z S.G. = 2.8, Density = 23.34 ppg
z Acid soluble
z Lo-Wate
z Used to increase fluid density up to
maximum of 14.0 ppg ±
z Used as bridging agent in drill-in,
oil and synthetic fluids
Composition:
Inert solids
z Lost Circulation Material
z Material used to bridge off (seal)
formations where whole mud is being
lost to the formation
z Nut shells (mostly pecan & walnut)
z Mica
z Fiber (wood, paper, plastic, etc.)
Composition:
Inert solids
z Formation solids
z S.G. = 2.6 ±, Density = 21.67 ppg ±
z Sand
z Limestone
z Dolomite
Composition:
Soluble chemicals
z Caustic Soda (NaOH) pH 13.3
z Caustic Potash (KOH) pH 13.3
z Lime [Ca(OH)2] pH 12.4
z Soda Ash (Na2CO3) pH 11 - 11.5
z Sodium Bicarb (NaHCO3) pH 8.4
z Zinc Oxide (ZnO)
Composition:
Soluble chemicals
z Lignosulfonate (organic acid)
z Spersene (chrome lignosulfonate)
z Spersene CF (chrome-free
lignosulfonate)
z Chemical de-flocculant (mud thinner)
adds anionic (negative) charges to the
mud.
Composition:
Soluble chemicals
z Lignite (organic acid)
z Tannathin (lignite)
z XP-20 (chrome lignite)
z Chemical de-flocculant (mud thinner)
adds anionic (negative) charges to the
mud.
z Neutralizes positive sites on the clays
causing them to repel each other.
