Toward mechanistic understanding of asphaltene adsorption onto quartz surface: The roles of size, concentration, and hydrophobicity of quartz, asphaltene composition, flow condition, and aqueous phase
Abstract: The nature of asphaltene and mineralogy of reservoir rock affect the asphaltene
adsorption onto the rock surface. The main aim of the present work is to assess the adsorption of
different asphaltenes on quartz as the main mineral of sandstone formations. For this purpose,
asphaltenes were extracted from four crude oil samples from different Iranian oil reservoirs and
their specifications were analyzed applying various methods including Fourier-transform infrared
spectroscopy (FTIR), elemental analysis, dynamic light scattering (DLS), and field emission
scanning electron microscopy (FESEM). Also, Brunauer–Emmett–Teller (BET) and X-ray
fluorescence (XRF) methods were carried out to analyze the quartz mineral. Adsorption
experiments were performed both statically and dynamically and the effects of water phase
addition on the adsorption of asphaltene on the mineral were investigated. The results of this work
indicated that the adsorption amount of asphaltene on the quartz surface is directly related to the
nitrogen content and polarity of asphaltene, but it is not related to the average particle diameter of
asphaltenes and their aromatic nature. When changing the flow rate, from 5 to 10 ml/min in the
dynamic adsorption process, the asphaltene uptake by quartz is reduced by about 35%, This could
be a clear indication of the physical adsorption of the asphaltene molecule on the surface of the
quartz rock. Finally, to compare the amount of adsorption in two-phase and three-phase systems
(with water), the test results showed a reduction of more than 30% of the amount of adsorption in
the three-phase mode, which indicates the effect of the competitive presence of water with
asphaltene for the surface-active sites. Also, the uptake of asphaltene onto the quartz samples
increased with increasing the initial asphaltene concentration and decreasing quartz particle sizes.
The effect of wettability on asphaltene adsorption in two- and three-phase systems was
investigated using hydrophilic and hydrophobic quartz nanoparticles. In both systems, the
adsorption of asphaltene on hydrophobic nanoparticles was higher and the adsorption reduction in
the three-phase system was calculated to be between 5-10%, which was very small compared to
hydrophilic nanoparticles. Wettability of nanoparticles compared to their specific surface area
showed more importance in asphaltene adsorption.