Surfactant adsorption behaviors onto shale from Malaysian formations: Influence of silicon dioxide nanoparticles, surfactant type, temperature, salinity and shale lithology

The application of surfactants has proven important in the field of hydrocarbon recovery from the conventional and unconventional reservoirs. An experimental investigation of influence of silicon dioxide nanoparticles, temperature, salinity, as well as surfactant type and shale lithology, on the adsorption behaviours of three types of commonly used surfactants onto two types of shale found in specific Malaysian formations was investigated in this study. Shale samples were characterized using electron microscopy and FITR spectroscopy. Critical micelle concentration and zeta potential studies were performed on surfactants. Nanoparticles were analyzed in terms of elemental composition and wettability. A series of adsorption experiments was conducted. The amount of surfactant adsorbed on shale was determined through the batch experiments using UV-Visible spectroscopy. Adsorption isotherms data were analyzed by fitting with Linear, Langmuir, Freundlich and Temkin isotherm models. Surfactant adsorption onto shale increases with increasing salinity and decreases with increasing temperature and presence of nanoparticles in the surfactant solutions. The adsorption behaviours of surfactants and nanoparticles-surfactant mixtures onto shale were suited by different equilibrium adsorption isotherm models depending on the surfactant type, adsorbent lithology, as well as, critical parameters such as salinity and temperature conditions. Presence of clay minerals contributed significantly to the adsorption capacity of shale. There is a threshold surfactant concentration, below which there is almost complete adsorption of surfactant monomers on the adsorbent surfaces. The maximum amount of surfactant adsorbed onto shale rock with 55 wt% quartz content was in the increasing order of CTAB > SDBS > Triton X-100 while it was in the order of CTAB > Triton X-100 > SDBS for shale sample with 74 wt% quartz content. Electrostatic interaction between the charged surfaces of the SiO2 nanoparticles and the surfactant head-groups resulted in almost 50% decrease in amount of surfactant adsorbed onto shale at high salinity (3 wt% NaCl) and by 81% at high temperature (353K) conditions. The findings of the study have wide applications in surfactant flooding designs, surfactant adsorption minimization and optimization in the field.