LIGHTENING ADDITIVE FOR CEMENT MIXTURES AND PREPARATION METHOD THEREOF Russian patent published in 2011 - IPC C09K8/473 C04B20/00 

FIELD: chemistry.

SUBSTANCE: invention relates to oil-and-gas industry and can be used to prepare light backfill cement grout when casing cementing gas, gas-condensate and oil wells. The method of preparing a lightening additive for backfill cement grout involves separating aluminosilicate microspheres from an aqueous suspension of ash dust from thermal power plants via hydroseparation and removing emerging aluminosilicate microspheres, dehydrating the microspheres, drying and fractionating the microspheres, containing the following in wt %: SiO₂ 52.1-56.1; Al₂O₃ 33.1-37.8; Fe₂O₃ 0.5-1.7; CaO 0.34-0.92; MgO 0.23-0.36; Na₂O 0.34-0.48; K₂O 0.31-0.49; TiO₂ 0.6-1.5; other impurities - the rest, with separation of five fractions with diametre 1-315 mcm and obtaining their mixture in their following ratio in wt %: 1-50 mcm 4.0-8.0; 51-100 mcm 41.5-42.2; 101-160 mcm 40.0-42.0; 161-200 mcm 8.0-10.0; 201-315 mcm - the rest. From the said limits of the ratios, specific values of the ratio are selected for specific maximum hydrostatic pressure P_hydr in the well taking into account the number of broken microspheres for each of the said fraction, where P_hydr is defined using the formulae given above. Said additive is obtained using the method given above.

EFFECT: low density of the cement grout and high strength of the hardened cement paste in deep and super-deep wells.

2 cl, 5 tbl