Delay systems and application of these systems is of the cementing slurries of the wells petroleum or the like

摘要

The present invention relates to systems for retarding setting in an oilfield well cement slurry constituted by a solution of a phosphonate selected from methylene phosphonic acid derivatives and a phosphate, in particular selected from the following salts or the corresponding acids: mono-phosphates (ortho-phosphates PO42-, meta-phosphates PO3-), acyclic poly-phosphates (pyrophosphates P2O74-, tripolyphosphates P3O105-) or cyclic poly-phosphates. The system preferably may also comprise a retarder booster and is more particularly applicable to cementing at low or medium temperatures.