Green synthesis of nanocolloids and emulsions based on iron oxide nanoparticles with application to the enhanced oil recovery

In the present work, aqueous solutions of polyphenols extracted from parsley leaves were prepared and reacted with ferric (III) chloride hexahydrate, and ferrous (II) sulfate heptahydrate to synthesize and stabilize aqueous suspensions of iron oxide nanoparticles (IONP). The interfacial and wetting properties of IONP suspensions were measured to assess their capacity to generate stable Pickering emulsions and mobilize trapped oil ganglia in a glass-etched pore network. The rheological properties of emulsions were measured, and their stability was quantified by recording the phase separation (macro-scale) and measuring the oil drop size distribution (micro-scale). The enhanced oil recovery (EOR) efficiency of IONP suspensions and emulsions was evaluated with tests of drainage / primary imbibition / secondary imbibition performed on a glass-etched pore network for synthetic oil / aqueous solution (3-distilled water or brine containing sodium chloride / calcium chloride salts) systems. The stability of IONP suspensions weakens with the presence of salts, and increases with the pH increasing. The surface and oil/water interfacial tension have the tendency to decrease with the IONP concentration increasing but they are not affected by the presence of salts. The oil-in-water Pickering emulsions are shear-thinning fluids with their shear viscosity increasing with the time. When using IONP suspensions in distilled water, the EOR efficiency increases by 10–22 %, for IONPs synthesized from ferrous sulfate, and by 11–15 % for IONPs synthesized from ferric chloride which are comparable to those achieved in earlier studies. The EOR efficiency increases profoundly when using IONP-based Pickering emulsions in distilled water (∼50–80 %) or brine (∼100 %), due to the frontal drive pattern associated with the high values of viscosity ratio and capillary numbers. The oil volume recovered by EOR per unit of energy consumed is maximized when using IONP suspensions or Pickering emulsions of specific composition. • IONPs concentration close to 1 g/L is produced from iron concentration 1.9–2.8 g/L. • IONPs from parsley extracts are more stable than those from green tea extracts. • EOR efficiency is favored when low salinity IONP suspension is used. • EOR efficiency is maximized when injecting IONP-stabilized emulsions. • EOR efficiency per unit energy is maximized for low salinity nanofluids & emulsions.