固井水泥石温度与裂缝抑制用微胶囊实验研究

Development and study of microcapsules for suppression of temperature rise and crack generation in well cementing

摘要:

深海油气井经常穿越天然气水合物地层，天然气水合物在低温高压条件下稳定存在，固井水泥浆的水化热易引起井周水合物分解而导致严重井内事故。同时，水化热还会使固井水泥环产生热应力裂缝，降低水泥环的封隔能力，进而导致固井质量下降。本文以低碳链混合烷烃作为相变材料、环氧树脂作为裂缝抑制性材料基材，通过自组装法和冷凝析出法将碳酸钙和硬脂酸在其表面进行两次包覆，制备了一种适用于水合物地层固井水泥浆的控温自修复微胶囊。利用DSC、TG、体视显微镜、热循环试验和断裂面胶结试验对微胶囊基本性质进行了表征。通过水泥浆流变性能测试、水化温升试验、水泥石力学强度变化及裂缝发育情况的测试，研究了微胶囊在固井水泥浆体系中的控温和抑制裂缝的性能。

Abstract:

Deep-sea oil and gas wells often traverse natural gas hydrate formations. Due to the stable existence of natural gas hydrates under low temperature and high pressure conditions， the hydration heat of cement slurries can lead to the decomposition of hydrates around the wellbore， resulting in serious wellbore accidents. Moreover， hydration heat can induce thermal stress in the cement sheath， causing cracks and reducing the sealing capability of the cement sheath， ultimately leading to decreased cementing quality. In this study， low-carbon chain mixed alkanes were used as phase change materials and epoxy resin as the base material for crack suppression. A temperature-controlled self-healing microcapsule suitable for cement slurries in hydrate formations was prepared by the surface coating of calcium carbonate and stearic acid using a self-assembly method and a condensation method. The basic properties of the microcapsules were characterized using DSC， TG， optical microscopy， heat cycle tests， and fracture surface adhesion tests. The performance of the microcapsules in controlling temperature and suppressing cracks in cement slurry systems was investigated through rheological property tests， hydration heat rise tests， changes in the mechanical strength of cement stone， and crack development assessments.