1. n. [Drilling Fluids]

A polysaccharide secreted by the bacteria genus Xanthomonas campestris, also known as xanthan gum. XC in water muds provides non-Newtonian mud rheology, highly desirable because of the flat velocity profile it produces in annular flow, which is required for efficient cuttings lifting in lower density muds. XC polymer is anionic, with tolerance for salinity and fair tolerance for hardness ions. XC is a finely powdered material that can vary in the amount of residual bacteria debris and the ease with which it disperses into water. Temperature tolerance varies with water-phase components, but starts to degrade around 200 to 250°F [93 to 121°C]. Extreme pH or hardness are not well-tolerated by XC polymer and it is susceptible to bacterial attack.

Synonyms: xanthan gum

See: annular flow,  bactericide,  biopolymer,  carrying capacity,  hydration,  mud additive,  non-Newtonian fluid,  paraformaldehyde,  potassium mud,  power-law fluid,  prehydration,  pseudoplastic,  saltwater mud