Preparation of Microemulsion and Its In-Situ Oil Removal Performance on Oily Sludge from Shale Gas Drilling Platforms
Shale gas extraction generates hazardous oily sludge, necessitating effective in-situ treatment. Microemulsion technology offers low energy consumption, cost efficiency, and high oil removal without heating. This study investigates single-surfactant microemulsions using sodium dodecyl sulfate (SDS) and alpha-olefin sulfonate (AOS), and composite microemulsions with sodium silicate (Na2SiO3). Phase behavior and effects of surfactant, alcohol, and salt concentrations on oil removal were examined. Optimal single formulations achieved removal rates of 86.33% for SDS (SDS:alcohol:NaCl = 2.72%:13.21%:2.17% mass ratio) and 87.45% for AOS (SDS:alcohol:NaCl = 2.72%:15.41%:2.17%). SDS microemulsions showed superior phase stability despite slightly lower removal efficiency. Composite SDS-Na2SiO3 microemulsion achieved 92.47% oil removal, outperforming single systems, and could be recycled five times while meeting national secondary reuse standards. AOS-Na2SiO3 exhibited better salt resistance, whereas SDS-Na2SiO3 showed better alcohol resistance. This work provides a novel approach for in-situ oily sludge treatment.