The role of direct asphaltene inhibitors on asphaltene stabilization during gas injection

There are a large number of investigations, which evaluate the impact of the liquid-based inhibitors on the asphaltene stabilization. In those studies, a specific volume of inhibitor was added to the oil sample and the asphaltene precipitation is then studied. However, this method is indirectly applicable to processes like gas injection. For that reason, in this work, the metal oxide nanoparticles (GO, TiO2, SiO2, and MgO) have been considered in the liquid-free mode as direct asphaltene inhibitors (DAIs) on asphaltene stabilization for the duration of miscible CO2 injection. The dissolution of DAIs in CO2 was investigated by measurement of cloud point pressure to evaluate the pressure/temperature conditions, need for certifying that the CO2/DAIs mixtures have the single-phase condition. Afterwards, the impact of DAI was studied on asphaltene precipitation and deposition by static and dynamic approaches. Results show that the total size of asphaltene particles which precipitated during injection of miscible CO2/DAIs mixture is significantly lower than that for immiscible pure CO2 injection. The amount of asphaltene deposition significantly decreased during injection of miscible CO2/DAIs mixtures compared to immiscible pure CO2 injection. Additionally, the metal oxide nanoparticles hinder the phase separation of asphaltenes kinetically and prevent growth. It is conducted by stabilizing the colloidal suspension of the asphaltene particles, which are in sub-micrometre size to significantly slow the asphaltene flocculation onset.