Synthesis of novel green nanocomposites by considering enhanced oil recovery and asphaltene adsorption effectiveness in calcite and dolomite formations

•Introducing new eucalyptus/CuO/Fe3O4/xanthan green nanocomposites (EC-NCs) for asphaltene adsorption.•Asphaltene adsorption in the presence of EC-NCs in calcite and dolomite formations.•Effects of time steps and pressures on asphaltene adsorption using EC-NCs.•Using SEM, isotherm models, and CO2/oil interfacial tension tests for the investigation of asphaltene adsorption.•Performing natural depletion and core flooding tests in shale formation using EC-NCs. Asphaltene deposition is known as the main issues in reservoirs, which causes formation damage in reservoir. This research investigated the effects of a newly introduced green nanocomposites, namely eucalyptus/CuO/Fe3O4/xanthan nanocomposites (EC-NCs), on the inhibition of asphaltene precipitation in calcite and dolomite formations. First, at two time steps of 48 and 96 h, asphaltene adsorption on EC-NCs surfaces was examined through scanning electron microscope (SEM) tests in both calcite and formation tests. Moreover, asphaltene adsorption on the surface of EC-NCs was confirmed through isotherm models including Langmuir and Freundlich and the interfacial tension between CO2 and oil. Finally, a series of static and dynamic tests were performed at the highest adsorption pressure points, including 4200, 3950, and 3700 psi, and at the highest adsorption time step, i.e., 96 h, and the effects of asphaltene adsorption were seen on permeability reduction and asphaltene precipitation. EC-NCs exhibited superior efficacy in both asphaltene adsorption and precipitation inhibition. Two separate pressure changes were observed, and the ratios of the interfacial tension slope in the 2nd to the 1st regions [1st: 200–2700 psi, 2nd:2700–4200 psi] were changed from 19.44 % to 25.00 % and 29.74 % in 48 and 96 h, respectively, and this confirms that asphaltene had indeed adhered to the surface of the EC-NCs. Moreover, at 48, and 96 h, the size reductions of particles in SEM for calcite and dolomite were (29.27 %, 56.81 %), and (59.09 %, 62.25 %), respectively, which shows asphaltene adsorption was more efficient in dolomite formation, and in 96 h.