After the cement is placed in the wellbore and has been left static, it begins to develop gel strength (gelation). In this state, the unset slurry cannot fully transmit hydrostatic pressure to the formation (loss of overbalance). The time period of gelation before cement sets can last for several hours (transition time). The loss of hydrostatic pressure allows gas to percolate through the unset cement. After the cement has fully hardened, these channels still exist and they constitute a permanent path for uncontrolled gas migration to the surface or other formation zones.
Basoblock styrene-butadiene lattices and Paragas® which is a modified polyethylenimine, provide excellent gas migration control. Furthermore, Basoblock additives increase the elasticity to the cement and support fluid loss control.
Paragas® efficiently prevents gas channelling
Basoblock ND 614 is a lattice for oilwell cementing