Use of Gas Condensate for the Recovery of Hydrocarbons from Oily Sludge

Abstract

Petroleum operations generate large volumes of oily sludge, a complex residue composed of emulsified oil, water, mineral solids, and chemical additives. This waste reduces storage capacity, accelerates corrosion, and poses significant environmental challenges. Although gas condensate (C5+) has been mentioned in isolated studies, its systematic application as the primary extraction solvent in a mixer–settler system combined with surfactant-assisted demulsification and statistically optimized operating conditions remains unexplored. This study evaluates the feasibility of using C5+ to recover hydrocarbons from oily sludge generated during primary processing. A mixer–settler system was employed with C5+ as the extraction solvent and the commercial surfactant Dissolvan 974 (Clariant), a polycondensed resin dissolved in an organic solvent mixture of xylene and ethanol (20–30% each), to destabilize emulsions. The raw sludge contained 60.5% water, 23.5% oil, and 16.0% solids. A 33–1 fractional factorial design was used to optimize operational parameters. The results demonstrate that C5+ enables efficient oil–water–solid separation and high hydrocarbon recovery, providing a technically viable and environmentally aligned pathway for oily sludge valorization. This integrated strategy offers a cost-effective alternative by utilizing an internal industrial byproduct to replace conventional solvents, while promoting environmental sustainability through circular-economy principles and alignment with the United Nations Sustainable Development Goals (SDGs 6, 9, and 12).