Nanohybrid preparation methods and compositions, and their usage as oil/water emulsion stabilizers for Chemical Enhanced Oil Recovery (C-EOR). These methods have two main steps: (a) MWCNTs modification; and (b) encapsulation and insertion techniques to insert inorganic nanoparticles into the modified MWCNTs structure. The so-prepared nanohybrids used for the preparation of nanofluids were found to decrease the oil surface tension and reservoir wettability modification from oil-wet to water-wet, which is useful for Chemical Enhanced Oil Recovery (C-EOR).