Treatment of oily drill cuttings slurries using supercritical carbon dioxide

Abstract

Research was conducted into using supercritical fluid extraction (SFE) for removing hydrocarbons from drill cuttings slurries, which will be used in a pilot-scale continuous SFE system currently under development. A laboratory-scale batch SFE system employing supercritical carbon dioxide (CO2) was used in this research. Based on the measured hydrocarbon solubility and apparent hydrocarbon solubility in supercritical CO2, conditions of 14.5 MPa and 40oC were selected for SFE treatment. The slurries require a minimum water to drill cuttings ratio of 1:1 (mass basis) to be “free-flowing” and therefore suitable for treatment in a continuous system. Water in the slurries leads to lower hydrocarbon extraction efficiencies during SFE treatment compared to the treatment of drill cuttings without slurrying. However, effective mixing and introduction of the supercritical CO2 at the bottom of the extraction vessel resulted in treated slurries containing less than 1% hydrocarbons (dry mass basis).