BAKER HUGHES - Drilling Fluids Reference Manual

Water Based Drilling Fluids
Polyethylene Glycols
Polyethylene glycols are polyglycols made from the addition of ethylene oxide to water (or low
molecular weight alcohols). The lower molecular weight commercial polyglycols are viscous
liquids while the higher molecular weight materials are tough solids. All are soluble in fresh
water at room temperature and up to near the boiling point of water. Toxicity of these products is
low. Biodegradability of polyethylene glycols is typically good due to the linearity of the
molecules.
Polypropylene Glycols
Polypropylene glycols are polyglycols made from the addition of propylene oxide to water or low
molecular weight alcohols (although other polyhydric alcohols can also be used). All are viscous
liquids and the higher molecular weight products (molecular weight > ~1,000) are essentially
insoluble in water. The lower molecular weight products (molecular weight < ~1,000), however,
tend to be soluble in fresh water (at least at room temperature) although some show inverse water
solubility with temperature changes. Toxicity of polypropylene glycols is typically low and
usually decreases with molecular weight. The lower molecular weight polypropylene glycols
normally show good biodegradability, while the higher molecular weight polypropylene glycols
are usually more resistant.
EO/PO Copolymers
EO/PO copolymers are polyglycols made from the random addition of both ethylene oxide (EO)
and propylene oxide (PO) to low molecular weight alcohols (commonly methyl or butyl). The
ratios of ethylene oxide and propylene oxide used is either close to unity, or ethylene oxide is
used in abundance. All are viscous liquids, soluble in fresh water at room temperature, and all
show inverse water solubility with temperature. Toxicity of EO/PO copolymers has been good
and would be expected to decline with molecular weight. The lower molecular weight EO/PO
copolymers tend to show acceptable biodegradability and the higher molecular weight materials
would be expected to be more resistant.
Polyglycerols
Polyglycerol is, or can be thought of as, a condensation product made from the
dehydration/condensation of glycerol. The commercial product is a blend of polyglycerol with
polyglycol for defoaming and ease of handling. The product appears to be soluble in fresh water
at all temperatures. The toxicity of polyglycerols is low, and biodegradability would be expected
to be good.
The selection of a particular polyol for use in a drilling fluid depends on the application required
and the environment to which it will be exposed. Low molecular weight water soluble glycols
find applications for cuttings and borehole stabilization. The scope of this document is restricted
to detailing the theory and application of low molecular weight polyols only.
The basic properties of glycols used in the AQUA-DRILL system are shown below.
Reference Manual
Baker Hughes Drilling Fluids
3-68 Revised 2006