Gas Migration through cement columns has been an industry challenge for many years. To control gas migration, high cement densities are required to successfully cement the high pressure formation. Formation gas/influx can migrate through the cement column resulting in gas being present at the surface.
Current high density cement formulations do not provide good gas migration prevention due to settling and increase in permeability. To solve the settling problem and reduce permeability of cement, intensive lab work was conducted earlier by Al-Yami et al. (2009).
The objective was to develop novel cement formula containing a combination of solids with different particle size distribution to minimize cement porosity and prevent solids settling. Compared to conventional high density cement weighted up with hematite, the developed cement showed no signs of settling, better fluid loss control and improved resistance against gas migration in the lab.
Saudi ARAMCO has successfully trial tested their new developed cement formula (Gas Preventing Cement) in 5 wells in 2015 for 9 5/8" casings across high pressure formation to mitigate 9 5/8" X 13 3/8" Annular leaks. This is an effort to help in minimizing gas shut-in potential and safety risks due to casing-casing leaks. The new formula was applied with good cement returns to surface and good wellbore isolation according to the conducted well flowing test. In addition, loggings were run to ensure good bonding of cement. More high pressure gas wells will be cemented using this formulation.