硫酸腐蚀后油井水泥石的性能及微观结构

Properties and Microstructure of Oil-Well Cement Stone Attacked by Vitriol

研究了硫酸对油井水泥石强度及微观结构的影响。结果表明:水泥石被硫酸腐蚀后,强度明显下降,硬化浆体中100 nm以上有害孔的数量显著增多,水化产物变得疏松多孔,硬化水泥浆体的物相组成发生变化,有新的腐蚀产物CaSO4 2H2O生成;水泥石抵抗酸性介质腐蚀的能力不仅与其致密程度有关,还与其硬化浆体的矿物组成密切相关;不同水化产物抵抗腐蚀的能力不同,Ca(OH)2比C-S-H凝胶更容易受到酸性介质的腐蚀;C-S-H凝胶被腐蚀后产生的孔隙主要是细小孔隙,而Ca(OH)2被腐蚀后产生的孔隙主要是100 nm以上有害孔,降低硬化浆体中Ca(OH)2的含量是提高水泥石抗腐蚀性能的关键。

The effect of vitriol on the strength and microstructure of hardened oil-well cement paste was investigated.The results show that the strength decreases,and harmful pores with the size of 100 nm increases and the hydration products become more po-rous when the hardened cement paste is attacked by vitriol.Also,the composition of the cement paste changed due to the generation of a new corrosion product CaSO4？2H2O.The vitriol corrosion resistance performance of hardened cement paste was correlated to the microstructure as well as the mineral composition.The vitriol corrosion resistance performances of different hydration products were different.Ca（OH）2 was more vulnerable rather than the C-S-H gel.Most of the pores generated in the C-S-H gel corrosion process were smaller,but most of the pores generated in the process of Ca（OH）2 corrosion were larger than 100 nm.The corrosion of Ca（OH）2 was thus more harmful to the macroscopic properties of hardened cement paste rather than the corrosion of C-S-H.The reduction of the Ca（OH）2 content in the hardened paste could be an effective way to improve its vitriol corrosion resistance performance.