1.
n. [Drilling Fluids]
Linear,
anionic polymer made from the
monomer acrylic
acid, CH2=CHCOO- H+. The acrylic acid groups are evenly spaced along the chain. Acrylic acid polymer neutralized with NaOH is sodium polyacrylate (SPA). Polyacrylates are best utilized in soft water with low salinity to achieve the best
dispersion and full chain elongation. Even low concentrations of hardness ions, for example, Ca+2,
precipitate polyacrylates. Low molecular-weight polyacrylates are used as
clay deflocculants. High molecular weight polymers are used for
fluid-loss control and as a
clay extender. As an extender, SPA is added to
bentonite at the grinding plant. It is also used at the
rig in
low-solids mud. Divalent cations can negate its benefits as a clay extender. SPA is highly efficient when used to
flocculate colloids in native-solids muds, clear-water muds and
wastewater cleanup. The polymer chain links together
colloidal solids that can be removed by gravity settling in shallow pits or by applying
hydrocyclone,
centrifuge or
filtration techniques.