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

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.