Patent ID: 7674331
Filing Date: 2010-03-09
Classification: C04B,C09K

Abstract:
1. A retarder for use in well cementing slurries, comprising a mixture of a set retarder and one or more silicates or silica comprising an alkali metal silicate of the general formula (SiO 2 )x(M 2 O) having a molar ratio falling in the range 1.68-3.37, wherein M is an alkali metal, the relative amounts of set retarder and silicates or silica are such that the retarding effect of the set retarder under downhole conditions is enhanced when compared to the retarding effect of the retarder alone, and the set of the cement at temperatures below 80° C. is accelerated when compared to the set of the cement containing the retarder wherein the amount of the silica or silicates allows the use of a lesser quantity of retarder than would be used alone for a given retarding effect at the bottom hole temperature above 90° C.