Sustainable treatment and recycling of oily sludge: Incorporation into gel -system to improve oil recovery.

Oily sludge is very difficult to treat in solid waste, how to achieve on-site treatment and recycling of the sludge is rarely reported. This research proposes a new treatment method for oily sludge by adding the oily sludge into the gel water plugging system designed for low-performing oilfields-sludge re-injection technology. The gel system of oily sludge can resist dehydration for 150 days at a high temperature up to 140 °C and a salinity of 2.11 × 105 mg/L, and its strength reaches grade I. The microstructure of the gel was revealed using scanning electron microscopy (SEM). The addition of oily sludge made the gel system microstructure develop a dense three-dimensional network structure, which can effectively improve the strength and temperature resistance of the gel system. Differential scanning calorimetry (DSC) experiments show that the gel with oily sludge can maintain temperature resistance even at 188 °C. Laboratory displacement experiments show that the breakthrough pressure of the gel system can reach 3418 kPa/m, and the plugging rate is above 98%. The performance of the system was improved by adding oily sludge into the gel as an enhancer, which provided a research idea for harmless treatment, resource utilization and clean production of oily sludge.