Utilization of nanoparticles for enhanced oil recovery (EOR) has attracted great attention in recent decades. However, various constraints influence fluid-fluid and fluid-rock interactions of nanofluids and subsequently oil recovery. A comprehensive review of existing literatures on how to mitigate against these limits are presented in this study. Furthermore, nanofluid EOR mechanisms and various application parameters which may influence nanofluid flooding efficiency were discussed. Also, the basic steps for preliminary investigation of nanomaterials for EOR, the challenges, gaps, and future trends associated with nanofluids reservoir field applications were suggested. Field trials results have proven that nanofluids can influence various EOR mechanisms.

Abstract: To monitor and manage hydrological systems such as brooks, streams, rivers, the use of tracers is a well-established process. Limited number of potential tracers such as salts, isotopes and dyes, make study of hydrological processes a challenge. Traditional tracers find limited use due to lack of multiplexed, multipoint tracing and background noise, among others. In this regard, DNA based tracers possess remarkable advantages including, environmentally friendly, stability, and high sensitivity in addition to showing great potential in the synthesis of ideally unlimited number of unique tracers capable of multipoint tracing. To prevent unintentional losses in the environment during application and easy recovery for analysis, we hereby report DNA encapsulation in silica containing magnetic cores (iron oxide) of two different shapes—spheres and cubes. The iron oxide nanoparticles having size range 10–20 nm, have been synthesized using co-precipitation of iron salts or thermal decomposition of iron oleate precursor in the presence of oleic acid or sodium oleate. Physico-chemical properties such as size, zeta potential, magnetism etc. of the iron oxide nanoparticles have been optimized using different ligands for effective binding of dsDNA, followed by silanization. We report for the first time the effect of surface coating on the magnetic properties of the iron oxide nanoparticles at each stage of functionalization, culminating in silica shells. Efficiency of encapsulation of three different dsDNA molecules has been studied using quantitative polymerase chain reaction (qPCR). Our results show that our DNA based magnetic tracers are excellent candidates for hydrological monitoring with easy recoverability and high signal amplification. Graphic Abstract: [Figure not available: see fulltext.].