Evaluation of Oil Desorption from Shale and Sandstone by Surfactant Solutions with Implication to Oily Drillcuttings Decontamination

In this paper, batch experiments of shale/sandstone aqueous systems were conducted to evaluate desorption of spiked oil from shale and sandstone using surfactant solutions. The desorption experimental study was designed to determine if selected surfactants in aqueous solutions with varying pH, initial oil on shale/sandstone, surfactant concentrations, surfactant type, solid/liquid ratio, with and without sonication and at different contact time could enhance the desorption of spiked oil (Sarapar147) from pre-spiked shale and sandstone. The experiments tested the influence of the selected variables in batch experiments. The early screening results obtained for sandstone and shale show that sandstone are very much easier to clean than shales. Furthermore, the desorption efficiencies was lower for water compared to surfactant solutions particularly for sandstones. Nevertheless, ultrasound was able to improve the desorption efficiencies for sandstone washings but not for shale washings. In the other hand, the results of the full factorial experiments showed that the variations of solution pH, mechanical interruption by ultrasound, and prolonged desorption times did not significantly improve the desorption process. These results give strong evidence to the existence of a considerable and irreversibly bound fraction of oil to shale.