Recent studies with nanoparticles have concentrated on improved oil reservoir recovery. A newly utilized ZnO/SiO2/xanthan/walnut green nanocomposites (NCs) is presented in this work, along with different surfactants like sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB), for exploring the physicochemical characteristics of sandstone reservoirs at real conditions (68 °C and 3120 psi). After performing characterization studies, based on interfacial tension, stability, and contact angle tests, 20 ppm of NCs was selected for the best outcomes. Then, 20 ppm was used in combination with different CTAB/SDS ratios, and three ratios, including 6:4, 7:3, and 8:3, were selected based on better interfacial tension and contact angle reduction tests. Finally, these scenarios (20 ppm NCs + (6:4, 7:3, and 8:3) CTAB/SDS ratios) were used in real imbibition tests using sandstone at 68 °C and 3120 psi. At 6:4, 7:3, and 8:3 CTAB/SDS ratios, interfacial tension and contact angle were reduced up to (10.12 mN/m, 57.55°), (9.22 mN/m, 56.13°), and (9.15 mN/m, 55.13°), respectively. Under a 28-day test, the recovery factors using base (without NCs and surfactant), 20 ppm NCs + 8:2 CTAB/SDS, 20 ppm NCs + 7:3 CTAB/SDS, and 20 ppm NCs + 6:4 CTAB/SDS were 50.41, 61.44, 63.19, and 70.17%, respectively.
