Increasingly challenging environmental legislation around the world has led to the development of technologies for the treatment of oil based mud (OBM) contaminated drill cuttings. Operators in many countries are currently using low and high temperature indirect thermal desorption to remove the oil and water from drill cuttings, providing an opportunity to recycle the recovered oils.

Thermal desorption plants are capable of recovering a variety of base fluids, including diesel, low toxicity, synthetic and crude oil. Safety and environmental concerns have been raised in the UK and Norway regarding the suitability of re-using the recovered fluids in the mud system. Occupational health concerns, mainly due to the potential presence of toxic species, have been voiced. Other countries around the world, including Holland, Kazakhstan, Denmark, Nigeria, Colombia, Bolivia and Ecuador, amongst others, already routinely reuse oil recovered from thermal processes in new drilling fluids.

This paper presents detailed chemical and physical analysis on the quality of fluids recovered from a low temperature indirect thermal desorption process in the United Kingdom. Detailed examples of a Synthetic and a Low Toxicity fluid are presented, including the compound(s) responsible for the characteristic odour associated with recovered oils, and a method for their removal. The results demonstrate that low temperature thermal desorption does not crack the base oil or produce toxic by-products, and that the recovered fluid has suitable rheological and toxilogical properties for reuse in drilling fluids.

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