纤维/晶须材料对固井水泥石的增韧机理研究

扫描电子显微镜（SEM）用于水泥基材料研究，可以准确、快速、直观地提供水泥石断面的微观形貌等信息。固井水泥环这一水泥基材料在井下工况受复杂应力影响易产生微裂缝与微环隙，造成水泥环封固能力下降。高弹模纤维、低弹模纤维、晶须等材料有助于降脆增韧水泥环。为了弄清高弹模纤维、低弹模纤维、晶须等材料对水泥环的降脆增韧机制，用扫描电镜对水泥石微观形貌进行了观察分析，探讨了增韧机制。实验结果表明，高弹模纤维、低弹模纤维、晶须等材料降脆增韧水泥环的机制包括拔出、桥连和裂纹偏转。相对于单掺纤维或单掺晶须，将二者混杂使用的增韧效果更好，其原理在于晶须属于微米级材料，可以阻止微米级微裂纹的产生和扩展；纤维属于毫米级材料，可以阻止毫米级微裂缝的产生与扩展；二者混杂使用可以起到多层次阻裂和增韧的目的。

Research on The Toughening Mechanism of Fiber/Whisker on Oil Well Cement Stone

Information such as the microstructure of cement stone cross section can be accurately, speedily and intuitively, provided by SEM when used in the research of cement-based materials. Oil well cement stone easily caused the micro-fracture and micro-annulus under the complex downhole stressed to decrease the sealing integrity between the cement sheath and the casing or formation. Whisker,fiber,and hybrid fiber are incorporated to strengthen and toughen the cement stone. Microstructures and micromechanical behaviors are investigated using scanning electron microscopy. The experimental results show that the toughness of the hybrid fiber cement stone was better than that of the single fiber cement stone. The toughening mechanisms of cement stone contains bridging, crack deflection and fiber pull out and the improvement could be correlated to energy-dissipating processes at the crack tips for different size and structure between the whisker and fibers and different load phases.