Synthesis and application of eucalyptus plant- and walnut shell- CuO/Fe3O4/Xanthan polymeric nanocomposites for enhanced oil recovery in carbonate reservoirs

Utilizing nanomaterials in enhanced oil recovery (EOR) operations is suggested as an efficient way to modify fluid-rock (i.e., contact angle) and fluid-fluid (i.e., interfacial tension) interactions in porous media. In the current experimental study, a well-known CuO/Fe3O4/Xanthan nanocomposite (NCs) was combined with two naturally-origin nanoparticles, i.e., eucalyptus plant (EP-NCs) and walnut shell (WS-NCs). The main novelty of the current study is synthesizing new nanocomposites and obtaining their optimum concentrations in the base fluid based on the contact angle and zeta potential tests. Scanning electron microscopy, Fourier-transform infrared spectroscopy, energy diffraction X-rays, and Brunauer-Emmett-Teller tests have been performed on the fabricated nanocomposites to investigate their surface morphology and chemical compositions. The results show that the synthesized nanocomposites have average diameters of NCs, EP-NCs, and WS-NCs of 31–59 nm, 15–101 nm, and 21–52 nm, respectively. Various tests, including wettability alteration, interfacial tension, zeta potential, and oil recovery, were conducted at 2000 psi and 70 °C to determine the best green nanocomposite and its optimum concentration for application in the carbonate porous media. The most stable nanofluids (i.e., the zeta potential of -23.88 to -33.65 mV) and the maximum decrease in contact angle (i.e., 76.10 ° to 43.98 °) have been achieved by the optimum concentration of the EP-NCs and WS-NCs in the base fluid (i.e., 30 ppm). Comparing the performance of the three investigated nanocomposites in reducing wettability and interfacial tension and increasing stability proves that the EP-NC performed better than the NCs and WS-NCs. In addition, the obtained displacement efficiency by 30 ppm of the NCs, WS-NCs, and EP-NCs in the base fluid at 70 °C and 2000 psi is 36.00%, 51.78%, and 60.61%., respectively.