Scale-Up Fabrication and Microfluidic Evaluation of Janus Graphene Nanofluids as Novel EOR Agent

Abstract

Nanofluid flooding is an emerging enhanced oil recovery (EOR) technique whereby injection fluids containing nanoparticles or nanocomposites are utilized for the oil displacement or injectivity improvement in oil reservoirs. However, current nanofluids with conventional nanoparticles have relatively low efficiency for EOR at simulated reservoir conditions, especially at low concentrations of nanoparticles. This research reported a new cost-effective method for scale-up synthesis of Janus graphene nanosheets and demonstrated a new type of nanomaterials, Janus nanofluids, as highly effective alternative nano-agents for EOR applications. A lyotropic liquid crystal phase as a novel "interfacial nano-reactor" system has been developed for fabricating Janus nanomaterials at nano-scaled liquid-liquid interfaces. Compared to interfacial reaction in a conventional bi-phase system, the new "interfacial nano-reactors" could tremendously enlarge the interfacial area by more than million times for chemical reactions at the interface, and thus allow production of Janus nanomaterials in mass quantity economically for industrial applications. Janus graphene nanosheets synthesized via this method have been characterized and confirmed by multiple techniques including scanning electron microscopy (SEM), Langmuir-Blodgett (LB) isotherm, contact angle, and interfacial tension (IFT) measurements. Interfacial tension measurements have shown that the Janus graphene nanosheets could significantly lower the IFTs between brine and crude oil at simulated reservoir conditions. With low concentration of Janus graphene nanosheets in nanofluid formula, microfluidic flooding experiments have been performed to evaluate the efficiency of the nanofluids for oil displacement in carbonate reservoirs. The results have demonstrated improved efficiency of oil recovery by the novel Janus graphene nanofluids at ultra-low concentration (0.01 wt%).