Feasibility Study of Asphaltene Damage Control in Low-perm Carbonates by In-Situ Synthesis of Fe2O3 Nanoparticles

Asphaltene precipitation/deposition in reservoir formation has detrimental influences on the oil production. The stability of w/o emulsions, the high viscosity of oil, and unfavorably changing the reservoir rock properties are induced in part by the asphaltene instability. Nanoparticles exhibit acceptable capacities for the adsorption and control of the precipitation of asphaltene. In this study, in-situ synthesis of iron oxide nanoparticles in reservoir oils has been followed to evaluate the effects of the thus-prepared nanoparticles on the control of asphaltene damage in tight carbonate core plugs. Model oil has been prepared by dissolving dead oil in a toluene/gasoil mixture. Following the preparation of stable emulsions of precursor iron salt aqueous solution in the model oil, Fe₂O₃ nanoparticles have been synthesized at a typical reservoir temperature and high-enough pressure in an autoclave. Two series of core-flooding experiments have been performed by the injection of n-C₆ and monitoring the hydrocarbon effective permeability before and after the damage. Two core plugs with the same flow zone index have been selected, one of which has been saturated with the model oil and the other with the emulsion, and the asphaltene damage has been induced by the core flooding test. The results of XRD and FESEM have indicated the crystalline structure and the mean particle size of 65 nm for the in-situ prepared nanoparticles, much smaller than the pore/throat sizes of the plugs. It is found out that the nanoparticles are effective in the control of the asphaltene damage at high injection/production flowrates. However, at low drawdown or injection/production flowrates, the in-situ synthesis procedure leads to a higher drop in the hydrocarbon effective permeability when compared to that observed during the displacement of the virgin model oil. Finally, this may be ascribed to the trapping of aqueous droplets in pore-throats, resulting in a significant reduction in the hydrocarbon permeability by the phase trapping.