Drilling Fluids
Citric Acid
Organic Acid
Citric acid is a weak organic acid that naturally occurs
in citrus fruits. Its chemical formula is C6H8O7, and its
molar mass is 192.124 g/mol. It is a trihydric acid in that
three hydrogen ions can dissociate from the molecule.
Consequently, its formula is often expressed as H3C6H5O7.
Applications
• Used to combat cement contamination because it reacts
with soluble calcium to form sparingly soluble calcium
citrate (0.095 g/100 mL at 77°F, 25°C) as a precipitate in
the following equation:
Advantages
• Natural substance
• Common oilfield chemical
• Multiple functions
Typical Physical Properties
Appearance
White crystals
Density
1.665 SG (anhydrous)
2(H3C6H5O7. H2O) + 3Ca(OH)2 → Ca3(C6H5O7)2↓ + 8H2O
Solubility
162 g/100 mL (68°F, 20°C)
• Used to reduce pH and to sequester iron
Packaging (sacks) (lb/kg)
55
25
Usage
Citric acid is applied at levels necessary to remove the
contamination—typically between 0.5 to 3.0 lb/bbl
(1.43 to 8.56 kg/m3).
Consult the MSDS, safety posters, and/or product label before
use, and use personal protective equipment as advised.
Issued February 2010
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