锂盐早强剂改善油井水泥的低温性能及其作用机理

Performance and mechanism of the lithium-salt accelerator in improving properties of the oil-well cement under low temperature

为缩短深水低温固井候凝时间,开展了锂盐早强剂对油井水泥低温水化能力和性能影响的研究。结果表明,锂盐早强剂通过加快水化保护膜破裂使水化诱导期缩短的方式提高油井水泥中C3S、C2S低温水化能力,从而明显缩短油井水泥的低温稠化时间,提高低温抗压强度,并且对水泥浆初始稠度无影响,表现出优异的低温早强功效。锂盐早强剂对油井水泥的水化产物类型无影响,水化产物主要为硅酸钙凝胶、Ca(OH)2晶体和少量钙钒石AFt晶体,与单纯油井水泥水化产物一致,但水化产物的微观结构较常规水泥石致密。

To shorten the waiting-on-cement time under deepwater and low temperature cementing conditions,the present paper dealt with the influence of a new lithium-salt accelerator on the low-temperature hydration capacity and property of oil-well cement and showed that the lithium-salt accelerator could enhance the low-temperature hydratability of C3S and C2S mineral clinkers by means of speeding up the breakdown of protective membranes and shortening the induction period of hydration.Affecting the initial consistency of cement slurry little,the accelerator could shorten the thickening time of the class-G cement slurry,significantly improve the early strength of set cement at low temperature,and show remarkable virtue of acceleration.The lithium-salt accelerator also hardly affected types of hydration products of oil-well cement and these hydration products were mainly composed of calcium silicate gel,calcium-hydroxide crystals and minor ettringite（AFt） crystals,consistent with the hydration product of pure oil-well cement except for denser microstructures than the conventional cement stone.