Summary Wellbore cement primarily serves to maintain structural integrity, separate zones, and ensure the long-term stability of hydrocarbon wells, particularly under high-pressure, high-temperature (HPHT) conditions. Conventional cementing practices face several challenges, including the integrity of porous or uncompacted cement, and fluid loss due to pressure differences. Recently, the development of nanomaterials for cementing has shown significant promise as nanoadditives for optimizing cement performance. In this study, we present the systematic investigation of morphology-controlled zinc oxide (ZnO) nanoparticles (NPs) for wellbore cement applications. The aim of our investigation is to evaluate the effect of ZnO-NPs synthesized by two different procedures: hydrothermal (H) reducing ZnO using sodium borohydride (NaBH4) and wet chemical (W) reducing ZnO using sodium hydroxide (NaOH), on the performance of American Petroleum Institute (API) Class G cements under elevated laboratory conditions. Novel flower-like ZnO nanostructures were successfully synthesized via hydrothermal methods, demonstrating superior performance over round-agglomerated particles. The synthesized ZnO-NPs exhibited varied morphologies and particle sizes and were introduced into cement slurries at different concentrations (0.01–0.05 wt%). The examined properties of the wellbore cement include compressive strength, fluid loss, elastic properties Poisson’s ratio (PR) and Young’s modulus (YM), porosity, and permeability. This study demonstrates that morphological control significantly influences cement performance: 0.05 wt% H-ZnO-NPs increased compressive strength by 44.43%, while 0.05 wt% W-ZnO-NPs increased it by 32.79% over the base cement. Porosity and permeability were reduced by 59.7% and 77.8%, respectively, for H-ZnO-NPs and by 47.2% and 61.7% for W-ZnO-NPs, indicating superior microstructural densification in hydrothermally derived systems. Fluid loss decreased progressively by 17%, 29%, and 45% with increasing H-ZnO-NPs concentration, demonstrating efficient filtration control. Elastic characterization revealed a 30.1% reduction in YM and a 30.8% increase in PR with 0.05 wt% H-ZnO-NPs, indicating enhanced flexibility and stress tolerance. H-ZnO-NPs also more effectively reduce porosity and permeability in core samples compared with W-ZnO-NPs due to their flower-like nanostructure. Scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) analyses of the NPs reveal their structural and chemical compositions. Results indicate that ZnO-NPs improve cement performance in the elevated pressure and temperature environment, and modifying the morphologies of ZnO-NPs can further optimize cement performance. The novel finding reveals that flower-like structures exhibit superior efficiency in filling void spaces and reducing permeability, and they are developed within a compact cement matrix, which is critical for maintaining wellbore stability. This pioneering research establishes morphological control as a new design paradigm for developing next-generation cementing additives specifically tailored for wellbore environments.
Shahzar et al. (Mon,) studied this question.