Synergetic effect between in-situ mobility control and micro-displacement for chemical enhanced oil recovery (CEOR) of a surface-active nanofluid

Abstract

Environmentally friendly and high cost-effective chemical enhanced oil recovery (CEOR) techniques have been the center of attention in oil industry. In this context, we tested a synergy between in-situ mobility control and micro-displacement of a surface-active nanofluid that was simply created using silica nanoparticles and nonionic surfactant via a combination of batch measurements at oil-water-rock interfaces, microfluidic and heterogeneous core flooding tests. Results show that the surface-active nanofluid imposes a positive curvature upon the oil−water interface, inducing Pickering emulsions with in-situ mobility control at a wide range of water saturation. These Pickering emulsions are thermodynamically unstable but kinetically stable, suggesting a static demulsification of oil well produced liquids. Meanwhile, the surface-active nanofluid yields 10 −2 mN/m order magnitude of interfacial tension between oil and brine, and alters the oil-wet rock towards weak water-wet rock. Therefore, the capillary number of the surface-active nanofluid is 10 3 order magnitude to brine and has a higher value at higher water saturation condition, implying a self-regulating mobility control of the surface-active nanofluid. 0.6 pore volume of the surface-active nanofluid yields 29.2% of additional oil recovery with cumulative oil recovery of 70.9% under heterogeneous condition due to the mobility control of the in-situ Pickering emulsion and the micro-displacement behavior. CEOR potential of this nanofluid is comparable with alkali-surfactant-polymer flooding that has been a common knowledge of high CEOR method for decades. Moreover, the surface-active nanofluid can be easily prepared and injected using existing oilfield injection system with low-energy cost. Caption: In-situ O/W Pickering emulsion with self-regulating mobility at the displacement frontier, together with decreasing interfacial tension and rock wettability alteration of the nanofluid indicated a great chemical oil recovery potential. • A surface-active nanofluid was simply formulated using nanoparticles and surfactant with complement hydrogen bonds. • The nanofluid induced O/W Pickering emulsions with self-regulating mobility. • The relative capillary number of the nanofluid to brine was 10 3 order magnitude of brine. • The micro- and macro-displacement EOR efficiencies of the nanofluid were studied.

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