Diesel based drilling fluids had been widely used in the past due to its low price in the market. However, it has been well documented the adverse health and environmental effects of Diesel mostly due to the high aromatic hydrocarbon content which makes it toxic. As an alternative to the use of Diesel, PDVSA-Intevep has addressed efforts toward the development of environmentally safe drilling fluids. In that sense, new oil based mud formulated with mineral oil (< 0.1% aromatics) and palm tree oil (without aromatic), both produced in Venezuela, have been used for drilling operation proposes to overcome the environmental and health risks. The present work evaluated the toxicity and biodegradability of mineral and palm tree oil-base drilling fluids compared to those formulated with Diesel. Standard procedures were performed for both tests. US-EPA protocols were followed for toxicity evaluation and A.S.T.M for biodegradability tests. Biodegradation rate of drilling cuttings impregnated with the three fluids were estimated in soil pans at laboratory scale to determine bioremediation process of the waste. The results indicate that mineral and palm tree oil based fluids are no toxic (LC50 > 30,000 ppm) while Diesel showed high toxicity levels (LC50 19,000 ppm). Under anaerobic conditions, the palm tree oil based fluid was the only biodegraded (>70%). From the soil pan studies, the three types of oil impregnated cuttings showed to be bioremediated; nevertheless, the palm tree cuttings biodegrade in soil compost even without aeration.

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