Study on the mechanism of shear bonding performance of Al2O3-modified oil well cement slurry

The cementing quality at the wellbore interface is critical to wellbore integrity and long-term safety. In this study, Al2O3 modulates hydration products to enhance interfacial bond strength between cement slurry and casing. The influence of Al2O3 on primary cement interface bonding strength was investigated using characterization techniques including X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, backscattered electron microscopy, and mercury intrusion porosimetry. Interfacial bond strengths were tested at varying curing temperatures and durations. Analysis of hydration products, microstructure, and pore distribution in the interfacial transition zone revealed that Al2O3 promotes the formation of calcium aluminosilicate hydrate. These hydrates interlock with other hydration products to form a dense, interwoven packing structure, significantly optimizing the interfacial microtopography. Simultaneously, it effectively filled the primary pores and microcracks in the interfacial transition zone, reducing porosity and refining the pore size distribution. These combined effects enhanced the bonding performance at the cement ring-first interface. The optimal interfacial bond strength was achieved when the alumina content was 1.8 %.