C.R. Jones and S.E. Guigard (Canada)
Waste management, drilling waste, supercritical fluid extraction, carbon dioxide, slurry
A continuous supercritical fluid extraction system for the removal of oil from drilling waste is being proposed as a new and innovative technology to treat drilling waste and meet increasingly stringent environmental regulations on drilling waste disposal. It has been proposed that water be added to drilling waste prior to SFE treatment, to produce slurries that can be continuously pumped through an extractor. The purpose of this investigation was to determine the effect of adding water to oily drill cuttings on the oil removal efficiency of the process. Slurries were made using water to drilling waste ratios between 0:1 and 5:1 (on a mass basis), and contacted with supercritical carbon dioxide in a laboratory-scale semi-batch extraction system operating at 40°C and 14.5MPa. It was found that oil removal efficiencies dropped from 91.4% to 35.0% when the water content was increased from 0:1 to 2:1, but rose to 54.5% in slurries containing 5:1 water to drilling waste. It was also observed that free-flowing slurries, suitable for pumping before and after treatment, were formed when at least 1 part water was added. It is recommended that the extraction process, in particular the water content, temperature and pressure, be optimized for water to drilling waste ratios near 1:1.
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