BAKER HUGHES - Drilling Fluids Reference Manual

Baker Hughes Drilling Fluids
Table 3-5
Common polar groups in organic compounds
GROUP
FORMULA
CARBOXYL
– C
O
OH
AMINE
– C – NH 2
AMIDE
– C
O
NH 2
HYDROXYL
– C – OH
SULFONATE
– C – SO 2 H
All of these groups are commonly found in the organic polymers used in drilling fluids.
Inorganic compounds are the ionic ones (other than the salts of organic acids) and those covalent
compounds which do not contain carbon.
Solubility and Solutions
Solutions are homogenous mixtures of various compounds. For the purposes of drilling fluids,
only solutions in water and diesel oil will be considered. These two substances form the
continuous liquid part of the solution, which is known as the solvent. The substance dissolved in
the solvent is called the solute and may be solid, liquid or gas. If two liquids are soluble in each
other, they are said to be miscible.
Water is often described as the universal solvent, due to its ability to dissolve a large number of
different substances.
Many ionic compounds are soluble in water. The attractive forces between oppositely charged
ions are reduced by the water, so that it may become possible for each individual ion to separate
from the lattice, which thus breaks up. Each ion is normally hydrated, which means that it is
surrounded by a shell of water molecules which, due to their polar nature, are attracted to the
charge on the ion and are thus loosely bonded to it. This attraction of the solvent molecules to the
ions is called solvation, in solvents other than water.
The solution of sodium chloride in water can be written as NaCl + Water → Na + (aq) + Cl⎯ (aq)
where (aq) denotes the hydration as depicted below.
Baker Hughes Drilling Fluids
Reference Manual
Revised 2006 3-13