Abstract
Maintaining the stability of microbubbles is essential for enhancing the longevity of aphronic water-based drilling fluid usage in drilling depleted reservoirs and other under-pressured zones. Here, we introduce the integration of partially reduced graphene oxide (PrGO) nanosheets into the shell of aphron microbubbles (AMBS) to enhance the stability and size distribution, particularly for drilling fluid applications and carbon geological storage. The amphiphilic characteristic of PrGO nanosheets, due to meticulous control of the reduction process of graphene oxide, facilitates their spontaneous adsorption at interfaces, thereby reducing the interfacial energy as a two-dimensional surfactant. The loading of PrGO nanosheets in the polymeric shell of AMBs enhances mechanical strength, stability, and resistance to gas diffusion, prolonging the half-life of the microbubbles to over 120%. According to the results, a more uniform size distribution and reduction of microbubble size up to 60% have been achieved at a concentration of 0.30 wt % PrGO. Rheological studies using various models indicate the optimal PrGO concentration for improved stability in aphronic fluids. Filtration tests indicate the loaded PrGO can reduce filtration loss by up to 45% at 0.50 wt % by forming a cohesive and compressible cake, improving filtration control. Changes in the Fourier-transform infrared spectra and contact angle measurements suggest increased surface hydrophobicity with higher graphene concentrations in aphronic fluid cakes. Moreover, the study elucidates that the stability of microbubbles is influenced by the type of core gas, with N(2) gas yielding the highest stability and CO(2) the lowest. Ultimately, these results highlight the beneficial effect of incorporation of PrGO nanosheets in aphron microbubbles to boost the drilling fluid performance and efficiency, which will pave the way toward ultralightweight fluids that can even be used as carrier and injection fluids in carbon capture and leak-free geological storage technologies.