An Engineered Fit-For-Purpose Polymer Nanocomposite Seal Repair Material for Wellbores

Seal integrity of wellbores has become of significant interest due to repeated leakage and spill incidents occurring worldwide that jeopardize both human health and the environment in addition to causing significant economic burden. This is attributed to the fact that wellbores intersecting geographical formations contain potential leakage pathways. The cement-steel and cement-rock formation interfaces are recognized as two critical leakage pathways. A seal repair material that has good bond strength with both steel and rock formations in addition to the ability to completely fill thin microcracks is needed to restore the seal integrity of wellbores. In this research, engineered polymer nanocomposites are proposed for use as seal repair materials for wellbores. Novolac epoxy polymer nanocomposites (PNCs) show more than 200% and 250% higher bond strength with steel and shale, respectively, when compared with microfine cement. In addition, it was found that Novolac epoxy PNCs have up to 545% and 761% higher displacement at peak load and toughness than microfine cement respectively. Moreover, Novolac epoxy PNCs was able to completely fill 800 mm microcracks that microfine cement were not able to completely fill. Microstructural investigations using Fourier-Transform Infrared spectroscopy (FTIR) and Dynamic Mechanical Analysis (DMA) showed that incorporating aluminum nanoparticles (ANPs) in Novolac epoxy PNCs interrupted the polymerization process, which allowed free epoxy groups to improve the bond strength of PNCs with both shale and steel surfaces. On the other hand, penetrability calculations based on contact angle and surface tension of seal repair materials showed that nanomodified methyl methacrylate (NM-MMA) incorporating 0.5 wt.% ANPs has higher potential to penetrate thin microannuli than microfine cement and Novolac epoxy PNCs. NM-MMA was able to seal thin microcracks as small as 30 mm while microfine cement has very limited penetration in su