微米与纳米级CaCO3对油井水泥石酸溶特性的影响

Effect of Micron-CaCO_3 and Nano-CaCO_3 on the Acid-soluble Performance of Oil-well Cement Stone

为解决油井水泥浆对油气储层的污染问题,优化水泥浆的储层保护性能,开展了微米与纳米级CaCO_3对水泥石酸溶特性的影响研究。试验结果表明,微米与纳米CaCO_3的复合最优掺量为18.5%与1.5%,此时水泥石的抗压强度较基准组无较大降幅,其在盐酸中的2 h酸溶率提升至67.5%。结合XRD、热分析及扫描电镜结果,可知复掺纳米CaCO_3,晶核效应与高温水湿环境的共同作用下,激活了火山灰反应的活性,Ca(OH)_2与SiO_2明显被消耗,水泥石结构密实,强度提升;经盐酸2 h腐蚀后,掺入CaCO_3的水泥石表层较基准组的侵蚀程度更为严重,水化产层出现了明显脱落痕迹,残留物仅为未反应完全的硅灰,同时水泥石内部发现了C-S-H与Ca(OH)_2的被腐蚀痕迹,H+的渗透效果显著增强,油井水泥石的酸溶特性得到大幅提升的同时,有效保障了其在井下的有效封固能力。

In order to solve the pollution of oil-well cement paste on oil and gas reservoir,improving the reservoir protection performance of cement paste,the effect of micron-CaCO3 and nano-CaCO3 on acidsoluble performance of oil-well cement stone were carried out to study in this paper.The experimental results indicated that optimal dosage of micron-CaCO3 and nano-CaCO 3 was 18.5%and 1.5%respectively,the compressive strength in this dosage had no evident decreasing amplitude and the acidsoluble rate increased to 67.5%in 2 h corrosion compared with the plain specimen.Combined with Xray diffraction,thermoanalysis and scanning electron microscope experiment,it could be concluded that Ca(OH)2 and SiO2 were obviously consumed after the addition of nano-CaCO3,on account of the activity of pozzolanic reaction was activated synergistically in the high temperature and water wet environment,the structure of cement stone became denser and compressive strength improved.After 2 h corrosion of 15%hydrochloric acid,the surface layer mixed with CaCO 3 was more corrosive than the plain specimen,obvious shedding marks were appeared on the hydration production layer,the main residue was silicon fume that had not been fully reacted,the corrosion marks of C-S-H gel and Ca(OH)2 crystal were found in the core of cement stone,the permeation ability of H+increased.The acid solubility of the oil well cement had been greatly improved,and its effective sealing ability was vigorously guaranteed.