Conventional silicate cements at elevated temperatures have a series of problems, such as poor stability, declining of compressive strengthof set cement and cracking of set cement etc. To address these problems, studies have been conducted on the selection of materials for modification of cement, optimization of the mechanical properties of set cement and the overall properties od modified silicate cement slurry. It was concluded that, at elevated temperatures, addition of highly active minerals (such as volcanic ash) into cement can ensure the sound development of the compressive strength of set cement. Crystal whiskers/fibers selected play an important role in the "brittleness reduction and toughness enhancement" of set cement, ensuring that set cement does not crack when curing at elevated temperatures and its elastic modulus is controlled to less than 9.0 GPa. Using high performance filter loss reducers, retarders and high temperature stabilizers suitable for the cement, the cement slurry will have good overall properties, i.e., low filter loss, good high temperature stability, thickening time that is controllable and short transit time etc. This study is of importance to safe cementing of deep and ultra-deep wells with high job quality.%针对高温条件下,常规硅酸盐加砂水泥浆体系存在的稳定性差、水泥石抗压强度衰退和开裂等问题,有针对性地开展了水泥高温增强材料优选、水泥石力学性能优化和抗高温硅酸盐水泥浆体系综合性能优化等研究,结果表明,高温条件下,掺加火山灰类高活性矿物材料能保证水泥石抗压强度良好发展,无衰退现象;优选的晶须/纤维材料对水泥石"降脆、增韧"作用显著,水泥石高温养护无开裂现象,且弹性模量能控制在9.0 GPa以内;通过配套使用高性能抗高温降失水剂、缓凝剂和高温稳定剂等外加剂,水泥浆体系综合性能良好,具有低失水、高温稳定性好、稠化时间可调、过渡时间短等特点.该研究成果对保证深井、超深井固井安全,提高固井质量具有重要意义.
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