Recent Trends in EOR: Nanofluid Flooding

In this chapter, the role of a modern technique, nanofluid flooding has been elucidated for chemical enhanced oil recovery (EOR). Nanofluids are the suspensions of nanoparticles in a base fluid, predominantly water, are used to mobilize oil by altering the wettability of the formation, lowering the interfacial tension and application of disjoining pressure on the isolated/stranded globules of oil. This chapter discusses the preparation, characterization, stability, and factors affecting the stability of nanofluids used in oilfield applications, particularly for EOR. Nanofluid preparation involves two methods: step-by-step and two-steps. The latter disperses pre-prepared powdered nanoparticles (NPs) in a suitable base fluid, often polyacrylamide (PAM). Maintaining nanofluid stability is challenging due to NP agglomeration, leading to sedimentation, rheological, and thermal instability, potentially lowering oil recovery. This chapter also discusses the methods to assess nanofluid stability, including visual appearance, dynamic light scattering (DLS), and ultraviolet–visible (UV–vis) spectroscopy. Visual appearance observes changes in color, while DLS provides quantitative data on NPs' size distribution and zeta potential. UV–vis spectroscopy measures absorbance, indicating the weight percentage of NPs. Stability is crucial for successful EOR applications. Subsequently, in this chapter factors influencing nanofluid stability are discussed. Agglomeration and degradation are influenced by reservoir conditions such as temperature, salinity, and pH. Studies using different metal NPs (Al₂O₃, TiO₂, SiO₂) highlight their impact on oil recovery rates. However, the efficiency depends on reservoir conditions, influencing factors like wettability alteration, disjoining pressure, and adsorption on rock surfaces. Moreover, this chapter also discusses wettability alteration, IFT reduction, and disjoining pressure effects due to silica nanoparticles. Oil recovery experiments using nanofluids in sand pack cores demonstrate the impact of temperature and saline conditions on efficiency. Challenges in nanofluid application include agglomeration, economic viability, and the need for further research on mixed NPs. The chapter emphasizes the importance of stable and well-dispersed nanofluids, economic considerations, and fundamental understanding of processes. Finally, this chapter concludes the use of nanotechnology in EOR shows great potential, improving dispersion stability, rheological properties, wettability alteration, and IFT reduction. Ongoing challenges include developing stable nanofluids economically and addressing fundamental process understanding. Future research prospects were also discussed that includes modeling flow behavior through porous media and further fieldwork on nanoparticle assisted EOR methods.