高炉矿渣改性铝酸盐水泥材料腐蚀机理与性能

随着油气资源的勘探与开发力度加大，固井作业面临越来越复杂的工况，如高温、高压、酸性环境等，对固井水泥环提出了更高的要求，固井常用硅酸盐水泥由于自身矿物组分及水化产物原因，易被酸性环境腐蚀，进而引起固井水泥环封隔失效等问题。而高炉矿渣改性铝酸盐水泥基材料具有较好的耐高温性、耐久性和抗酸腐蚀性，还具有成本低、使用范围广的特点。模拟海上高温高压酸性气田开发实际工况，研究了高炉矿渣改性铝酸盐水泥的耐腐蚀性能，通过对腐蚀前后水泥石的物相组成和微观形貌的表征揭示了高炉矿渣改性水泥石的增强及防腐蚀机理。结果表明，掺入40%高炉矿渣可改善铝酸盐水泥后期强度衰退并提高防腐能力；微观分析表明，铝酸盐水泥主要物相CA会直接生成C₃AH₆，避免了C₂AH₈、CAH₁₀和高炉矿渣反应生成结构疏松并且强度较低的C₂ASH₈。由于该水化产物的大量生成，使得水泥石结构更为致密，减少了酸性介质腐蚀通道，使得高炉矿渣改性铝酸盐水泥石的力学性能以及防腐蚀能力大大提升。 

Research on the Effect of Blast Furnace Slag on Low-temperature Hydration Characteristics and High-temperature Mechanical Properties of Aluminate Cement

Well cementing operation is now faced with more complex working conditions such as high temperature, high pressure and acidic environment in oil and gas exploration and development, demanding higher quality cement sheath. Silicate cement, because of its mineral composition and hydrational products, is easy to get corroded in acidic environment, resulting in failure of the cement sheaths to seal the annular spaces behind the casing string. Compared with silicate cement, the aluminate cement modified with blast furnace slag has properties that are more satisfactory, for example, it has better high-temperature resistance, long durability, and higher resistance to acid corrosion, as well as low cost and wider applicability. The corrosion resistance of the blast furnace slag modified aluminate cement was studied in simulated working conditions of high temperature high pressure offshore operation. The strength development and corrosion resistance mechanisms of the blast furnace slag modified aluminate cement were revealed by characterizing the mineral composition and micromorphology of the set cement before and after corrosion. It was found that addition of 40% blast furnace slag helps the aluminate cement retard its late-stage strength deterioration and improve its corrosion resistance. Microscopic analyses showed that the tricalcium aluminate hexahydrate (C₃AH₆) is produced directly from the main mineral component CA (calcium aluminate) of the aluminate cement, thereby avoiding the reaction of C₂AH₈ (dicalcium aluminate octahydrate) and CAH₁₀ (calcium aluminate decahydrate) with the blast furnace slag to produce C₂ASH₈ (calcium aluminosilicate hydrate), a mineral having loose structure and low strength. The production of large amount of C₃AH₆ results in a set cement with much denser structure, reducing the number of channels through which acidic fluid can flow and greatly enhancing the mechanical property and corrosion resistance of the blast furnace slag modified aluminate cement.