Cement slurries for cementing well casings - contain polyvalent metal ions, silica and sodium silicate

摘要

Pumpable cement slurries for cementing well casings comprise (a) 5-15 pts. wt. of a source of polyvalent metal ions; (b) 15-20 pts. wt. of water per 100 pts. of total solids; (c) 60100 pts. wt. of a SiO2 source which hydrates and releases SiO2 for reaction with the polyvalent metal ions when exposed to heat; and (d) 5-15 pts. wt. of spray-dried Na silicate hydrate powder. The cement does not set until exposed to the high temps. prevailing in the well bore (e.g. >=150 degrees F), thus avoiding premature settling in the event of pump failure, etc. It is superior to Portland cement in its bonding strength to steel casing pipes and its resistance to high temps.