Effect of low OBM contamination on long-term integrity of API class H cement slurries – Experimental study

Drilling mud acts as an important primary barrier during the well construction phase, while the integrity of cement sheath is critical throughout the life cycle of the well. The mud-spacer-cement interactions highly affect the long-term integrity of the cement sheath and in other words the well integrity. Even today, the spacers are not capable of displacing all the drilling mud present in the wellbore before performing cementing operations and the cement slurry is contaminated with a small amount of drilling fluid and/or spacers. Oil based mud (OBM) is highly preferred over water-based mud (WBM) as a drilling fluid when drilling in challenging environments, but with current push for more environmentally drilling fluids the Water Base Muds (WBM) are preferred.