Pumpable, aq. cement slurry for use in deep oil or gas wells - is mixt. of blast furnace cement and fly ash, which is not impaired by solns. of magnesium salts

摘要

The slurry is made from a mixt. contg. portland cement, esp. blast furnace cement, as a hydraulic binder. To improve the setting of the slurry in the presence of Mg salts and their solns., and to increase the resistance of the solidified cement to such materials, an addn. of 10-70 wt.% (based on dry wt.) of EFA filler is made to the cement mixt. The pref. mixt. contains 65% blast furnace cement and 35% EFA filler. The EFA filler is a vitreous fly ash obtd. in electrofilters through which waste gases flow after burning coal at 1600- 1700 deg. C in power stations. The fly ash contains SiO2, Al2O3 and Fe2O3. The cement mixt. may also contain cpds. altering its density, flow and setting speed. Used in the cementing of pipes in very deep boreholes used for winning petroleum or natural gas. The mixts. is not impaired by Mg salt solns.