The focus of this paper is the application of colloidal suspensions of nanoparticles, commonly known as "nanofluids" for enhanced oil recovery in tight oil reservoirs. Nanofluids are specialized colloidal solvents, compatible with various types of fluids used in oil reservoirs and they have the potential to enhance the recovery of oil and gas from a variety of rock pores (EOR). Nanofluids can be used as an important tool to alter the properties of the formations. We examine here the underlying mechanisms, including the wettability alterations and reduction of the interfacial tension driving enhanced oil recovery in tight oil reservoirs using compositional numerical simulation.

We start with a review of the nanofluid properties critical to mobilize oil in the reservoir pore network by wettability alteration. We then demonstrate the effectiveness of surfactant-based nanofluids for wettability alteration using a comprehensive chemical flooding simulation. The modeling of wettability modification depends on a shift in relative permeability and capillary pressure curves during simulation. Altered wettability affects the residual phase saturations which, in turn, influences the relative permeability and causes oil mobilization. Moreover, capillary imbibition promotes oil recovery as the wettability is altered towards water-wet conditions. We investigate the major factors in wettability modification and how they influence the oil recovery through exhaustive sensitivity studies and a Pareto-based multi-objective optimization approach.

This study concentrates on the nanofluids mechanisms in enhanced oil recovery, including the permeability alterations, rock wettability alterations and reduction of the interfacial tension. A comprehensive simulation sensitivity study and a multi-objective optimization approach are utilized to identify the dominant parameters impacting oil recovery in tight oil reservoirs using complex surfactant based nanofluids. Based on the results, a set of guidelines are suggested for selection and application of nanofluids for improving oil recovery in tight oil reservoirs stimulated with multiple hydraulic fractures.

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