Drilling Fluid Contamination: Calcium Sulphate (Anhydrite)
Contamination with Calcium Sulphate (Anhydrite) will result in flocculation of bentonite muds resulting in an increase in yield point, gel strengths and fluid loss.
Polymer muds are relatively insensitive to this type of contamination, unless significant quantities of drilled clay solids are present.
Sources of Contamination
This type of contamination can occur whilst drilling Anhydrite.
Diagnosis
Calcium Sulphate (Anhydrite) contamination will result in:
- an increase in filtrate calcium.
- a decrease in pH
- a decrease in Pt.
Treatment