Waste water-based drilling fluids have some characteristics, such as complex chemical composition, colloidal stability, high COD (Chemical Oxygen Demand), low BOD (Biochemical Oxygen Demand)/COD ratio and poor chemical and biological degradation. As a result, such treatments as biochemical, chemical oxidation or membrane separation process has the deficiency of poor adaptability, poor treatment efficiency and high running costs. This paper has studied the treatment technology of low pressure distillation process for waste water-based drilling fluids.

This technology has been applied in four wells of CPOE5 platforms in Dagang oilfield. The field application results have shown that this technology used to treat waste water-based drilling fluid can efficiently reduce COD, especially has good adaptability to different kinds of drilling fluids.

The treatment technology studied in this paper can treat wastewater's COD to lower than 150mg/L. The disposed waste-water can reach the class II water quality requirements of China national standards (integrated wastewater discharge standard, GB8978-1996) and can be directly discharged into sea.

This technology can control the influence and harm of waste drilling fluid on marine environment and meet the requirements of offshore environmental protection.

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