Contamination is a steady process while drilling, as drilled solids are continually entering the mud. While much of the drilled solids are inert, there are certain materials which can cause severe chemical and physical problems.
Contaminants tend to become apparent more quickly with lightly treated muds rather than with more highly inhibited varieties.
Any contamination must be treated immediately so it is essential that careful and frequent checks are maintained on the mud properties at all times.
Advance treatment to prevent contaminants affecting the mud can be made if, for example, a complete geological prognosis is available or when drilling out cement. Whenever the mud has been contaminated and a cure is required careful pilot testing should be carried out before treating the complete mud system.
When drilling cement
- pre-treat with Sodium Bicarbonate
- dump any contaminated mud
- clean shakers continuously
- use medium size screens
- drill cement with sea water if possible