Abstract
With the increasing global population, fossil fuel resources still represent a main contributor to the energy supply, despite the progress made in the field of renewable energies. Large quantities of residual oil from mature reservoirs cannot be produced through primary and secondary recovery methods. Among alternative recovery techniques, chemically enhanced oil recovery methods are attracting considerable interest to increase the hydrocarbon recovery from oil-bearing geological formations. The wettability of any particular formation can be used to predict the oil recovery factor of a reservoir based on its wetting state. However, due to the complex nature of geological porous media, special treatments are required to control the wetting characteristics for improving the oil recovery. In this work, methyl orange (MO), a hazardous pollutant widely discharged in industrial wastewater, was used as a chemical agent for the purpose of altering the wettability. Initially, quartz substrates were aged with 10−2 mol/L n-decane/stearic acid solution to mimic natural geological conditions; then, stearic acid-aged quartz substrates were treated in various concentrations of MO (10, 25, 50, 75, and 100 mg/L) for 7 days at 50 °C, followed by advancing and receding contact angle measurements at various physico-thermal geological conditions (temperature 25, 50 °C, pressure 10, 15, 20 MPa, and brine salinity 0–0.3 M). Our results demonstrate that increasing the temperature, pressure, and salinity of quartz aged with stearic acid has a negative effect on the wettability (resulting in a higher hydrophobicity). However, at any constant physio-thermal condition, MO significantly alters the wettability of the organic-aged quartz substrates from oil-wet to water-wet conditions, thus improving oil recovery. The concentration of MO plays a critical role, with increasing concentrations favouring the water-wet conditions. Quartz aged with MO at a concentration of 100 mg/L shows water-wet behaviour, with the lowest advancing and receding contact angles of 31° and 29°, respectively, at 25 °C, 20 MPa, and 0.3 M salinity. The findings of this study provide new insights that can be useful for disposing MO in deep underground reservoirs rather than discharging into the hydrosphere, thus mitigating climate change. In addition, the present data can be helpful for improving the oil productivity from sandstone reservoirs.