Experimental Study of the Interface Bond Properties and Microstructures of Nanosilica-Modified Epoxy Resin Cement Materials

Summary The bond properties of the cement sheath in the annulus are critical to maintaining the sealing integrity of oil and gas wells. However, there is no agreement on how to test and evaluate the bond properties, and there is still no effective method for improving the interfacial bond strength. For this study, we established a tensile bond strength (TBS) setup and a novel nanosilica-modified epoxy resin (MER) cement slurry for enhancing the interfacial bond properties. The test samples were cured at 50°C, 70°C, and 90°C under a pressure of 21 MPa for 7 days. Experimental results demonstrated that the incorporation of MER significantly enhanced TBS values. Specifically, when 3% modified silica nanoparticles were added to the epoxy resin, a substantial increase in TBS was observed at both the first (between the casing and cement sheath) and second (between the cement sheath and formation) interfaces. The influence of core permeability on TBS was found to be negligible. The silica nanoparticles provided nucleation sites that facilitated the formation of hydration products. Based on the test results, the improved bonding performance of the resin-modified cement can be attributed to mechanisms of mechanical interlocking and interfacial chemical reactions. These findings suggest that MER is a promising additive for cement slurries aimed at enhancing interfacial bond strength and promoting cement hydration, thereby significantly improving the sealing integrity of oil and gas wells.