Nanofluids application in enhanced oil recovery process-opportunities and challenges

Enhanced oil recovery (EOR) remains paramount for tapping into residual oil post primary and secondary recovery stages. While conventional methods hold their ground, the rise of chemical EOR, especially utilizing nanofluids, stands out due to its economic viability, enhanced recovery efficiency, and adaptability. The allure of nanofluid-enhanced oil recovery (N-EOR) has grown amongst researchers, albeit with underlying mechanisms that still harbor inconsistencies and ambiguities. This review meticulously examines the micro-mechanics of nanofluid interactions with heavy oil molecules, particles, and surfaces, the methodologies underpinning nanofluid-assisted EOR, multiphase displacement within pores and cores, and the fluid–solid coupling during such flows. Key findings show that nanofluids alter mineral wettability, adjust oil/water interfacial tension, shift structural disjoining pressure, and curtail viscosity. The prowess of N-EOR largely hinges on nanoparticle adsorption. Their affinity for mineral surfaces induces a shift towards water-wet states, while their interplay at oil/water boundaries can tweak interfacial tensions, fostering emulsification. One standout revelation is the adsorption of asphaltenes on nanoparticles, which mitigates asphaltene concentrations in heavy oil, thereby diminishing viscosity and amplifying oil extraction. Contrary to previous studies that merely spotlighted outcomes, our review delves deep into the complexities of nanoparticle adsorption, spotlighting the harmonious interplay between nanoparticle adsorption features and N-EOR operations. We unravel the intricacies of nanofluid behaviors during multiphase core displacement and provide a detailed overview of pertinent simulations. To encapsulate, this study demystifies potential N-EOR techniques and charts fresh research trajectories. Our revelations aim to enrich the comprehension of N-EOR phenomena, accentuating the pivotal role of nanofluids in multiphase core transitions and computational simulations. Furthermore, we highlight lingering challenges, directing the scientific community towards continued nanoparticle innovations and exploration. The novelty of this study is as follows: Nanofluids are mainly used in the third oil recovery process, and are not used in the first and second oil recovery processes. In addition, during the third oil recovery, some nanofluids may remain in the mine due to the sedimentation characteristics of nanomaterials. Currently, we are also committed to developing new processes to reduce the deposition of nanomaterials in the mine. At present, it is not clear how nanofluids enhance the oil recovery mechanism, and the oil recovery mechanism is relatively chaotic. In this article, we analyzed these mechanisms.