Water-based Nanofluid EOR in Carbonate Reservoirs Using Green Synthesized Nanocomposites

Abstract

Polymer and smart water flooding have been shown, repeatedly, to be effective methods for chemical Enhanced Oil Recovery (cEOR). The benefits are obtained by increasing the viscosity of the injected fluid, minimizing the interfacial tension (IFT) of the crude oil/aqueous phase, and by wettability alteration. Similarly, nanofluids (fluids injected with nanoparticles) have also been demonstrated to induce the same processes. We have analyzed the EOR response of green nanofluids when formulated with a typical natural polymer mixed with the LoSal and smart waters. For this purpose, two nanocomposites (NCs) called ZnO/SiO2/Xanthan and TiO2@SiO2@poly(acrylamide) were synthesized and prepared from the pomegranate seed extract using a simple, economical and, importantly, green method. The characterization of the synthesized NCs was investigated using the ultraviolet–visible spectroscopy (UV–Vis), scanning electron microscopy (SEM), electron dispersive spectroscopy (EDS), X-ray diffraction (XRD), termogravimeric analysis (TGA) and Fourier-transform infrared spectroscopy (FTIR). In this study, the distilled water, seawater, its dilutions (1:10 and 1:20 time dilutions) and smart water were used as dispersion medias for the developed nanocomposites at different concentrations of 500, 1000, 1500 and 2000 ppm. From the smart waters formulated the single and binary systems of different monovalent and divalent ions at different concentrations (2500, 5000 and 10000 ppm), such as NaCl, KCl, MgCl2, CaCl2, Na2SO4, MgSO4, K2SO4 and CaSO4, KCl-5000, K2SO4-5000, CaSO4+CaCl2 (5000+5000) and K2SO4+ CaCL2 (2500+2500) were selected as the optimal smart solutions dependent of their IFT and CA results. The prepared nanofluids were then tested in various experimental studies related to the stability of injections fluids, IFT behavior, wettability alteration, oil/nanofluid emulsification, and EOR flooding. The pendant drop technique was used to measure the interfacial tension (IFT) of crude-oil/SW, crude-oil/LoSal-water, crude-oil/smart- iii water and crude-oil/nanofluid systems, the wettability behavior of carbonate rock samples was studied using the contact angle (CA) measurement, and nine carbonate core samples were used to observe the role of the synthesized NCs on the performance of the LoSal and smart waters in improving oil recovery using coreflooding tests. The LoSal nanofluid, with 2000 ppm ZnO/SiO2/Xanthan NCs, enabled higher oil recovery by 19.28% OOIP due to a significant reduction in IFT, higher viscosity, better emulsion stability, and wettability alteration towards a stronger water-wet system from 137° to 34° contact angle. Additionally, the performance of the selected smart waters was improved by 65% in IFT reduction, 32% in wettability alteration and 10.5 % in oil recovery due to the influence of the TiO2@SiO2@poly(acrylamide) NCs. Nano-OSS3-5000 smart-nanofluid developed from mixing 1500 ppm of TiO2@SiO2@poly(acrylamide) with 5000 ppm of CaSO4 and CaCl2 ions demonstrated the highest performance in increasing oil recovery from 36.0 to 46.53% OOIP. Overall, ZnO/SiO2/Xanthan NCs dispersed within the LoSal water demonstrated the better performance compared with the TiO2@SiO2@poly(acrylamide) dispersed within the optimal smart waters in improving oil recovery due to the IFT reduction and wettability alteration.