BAKER HUGHES - Drilling Fluids Reference Manual

Water Based Drilling Fluids
Glycol and water together
At room temperature, the
glycol demonstrates
complete water solubility.
Glycol/Water solution at cloud point
When the solution's temperature is
raised to the cloud point, the glycol
becomes insoluble and begins to
form individual droplets (micelles).
The solution's appearance
becomes "cloudy".
Solution above cloud point temp.
If the temperature remains above
the cloud point, the seperation of
glycol and water becomes
distinct and both phases are
clearly visible.
Figure 3-18
Cloud Point: Temperature at Which Water and Glycol Begin to Separate
Engineering Cloud Point
For glycols at room temperature, water solubility decreases with increasing molecular weight.
Low molecular weight glycols are typically more soluble in freshwater systems than in high
molecular weight glycols. Two factors control the cloud point of freshwater glycols:
• salinity
• glycol concentration
An increase in either of these factors results in a lower cloud point temperature.
When a glycol is mixed in water below the resultant solution’s cloud point, it is evenly distributed
as minute droplets known as micelles. The micelles are stabilized by hydrogen bonding between
the water molecules and oxygen atoms present in the glycol molecule. The stabilization process is
known as hydration. When the temperature increases, hydration decreases until the micelles are
no longer stable in an aqueous environment. Consequently, they coalesce in large numbers and
form a separate phase that is distinct from the water.
The “clouding” process is reversible. If the solution is subsequently cooled, the two phases
recombine to form a clear, single-phase solution. Baker Hughes Drilling Fluids has engineered
combinations of glycol concentration and salinity to design a drilling fluid where glycols are in
solution on the surface and out of solution downhole. As bottom-hole temperatures change with
depth, the system’s cloud point can be adjusted to maintain optimized drilling performance and
shale stability.
Reference Manual
Baker Hughes Drilling Fluids
3-74 Revised 2006