水合物地层低热固井水泥浆用相变微胶囊的制备及应用

Preparation and application of phase change microcapsules for low heat cement slurry for well cementing in hydrate formation

当深海固井遇到天然气水合物地层时,由于水泥浆水化放热,导致水合物的相变平衡条件发生改变,诱发水合物分解,引起二界面胶结质量下降等问题。为提高水合物地层固井质量,可向水泥浆中添加具有吸热控温作用的相变微胶囊,可有效降低固井水泥浆的水化升温。基于此,以配比石蜡为控温芯材、碳酸钙为壁材,利用自组装法制备了一种使用于深水水合物地层固井水泥浆控温微胶囊。由于固井水泥浆在达到水合物地层的过程中,外界温度环境复杂,单一相变温度的控温芯材极易失效。为扩展控温区间,选用切片石蜡与白油作为混合芯材,控温区间达到14.8~39.8℃。研究表明,该微胶囊表观形态良好、彼此无团聚,在热循环过程中,不易发生泄漏。与水泥浆复配后,对水泥浆流变性能无明显影响。在低掺加量时,微胶囊主要起降低水泥浆峰值温度的效果,并提升水泥石整体力学强度;高掺加量时,微胶囊既可以有效降低水泥浆峰值温度,也可以明显地延缓水泥浆放热速率。

When deep⁃sea cementing is performed in the natural gas hydrate formation,hydration heat release of cement slurry will change the phase transition equilibrium conditions of hydrate,and induce hydrate decomposition,causing the quality of cementation at the two interfaces to decrease.In order to improve the cementing quality in hydrate formation,phase change microcapsules with endothermic temperature control can be added to cement slurry to effectively reduce the hydration temperature of cementing slurry.Based on this,a temperature⁃controlled microcapsule for cementing slurry in deep water hydrate formation was prepared with the self⁃assembly method.The temperature⁃controlled core material with single phase transition temperature is easy to fail due to the complex external temperature environment of cementing cement slurry in the process of reaching hydrate formation.For expanding the temperature control range,paraffin and white oil were selected as the mixed core material with the temperature control range from 14.8℃to 39.8℃achieved.Study shows that the microcapsule has good apparent morphology and no agglomeration with each other,so it is not prone to leakage during thermal cycling.After mixed with cement slurry,it doesn’t affect obviously the rheological properties of cement slurry.At low dosage,microcapsules mainly reduces the peak temperature of cement slurry and improves the overall mechanical strength of cement stone.At high dosage,microcapsules can not only effectively reduce the peak temperature of cement slurry,but also delay the heat release rate of cement slurry.