Particular pollutants, human health risk and ecological risk of oil-based drilling fluid: a case study of Fuling shale gas field.

Samples of new oil-based drilling fluid (NOBDF) and circulating oil-based drilling fluid (COBDF) in Chongqing were tested and analyzed to evaluate the possible impact of oil-based drilling fluid (OBDF) on human health and ecological environment. Organic matter, metals, and naturally occurring radionuclide materials (NORMs) in OBDF samples were analyzed and determined by gas chromatography-mass spectrometry, high-performance liquid chromatography, PANalytical Axios Fast XRF spectrometer, and gamma ray spectrometer. The results revealed that the contents of trace metals and NORMs in OBDF were less, which would not cause local ecological risk or health risk to the drilling crew. However, the concentrations of various aromatics analyzed in OBDF were very high, which was easy to pose serious environmental and health hazards. There were 8 aromatic hydrocarbons (AHs) in NOBDF and 15 AHs in COBDF. And the total carcinogenic risk value of each aromatic hydrocarbon was far greater than 10-4, which belonged to an unacceptable level. In addition, the inhalation pathway seemed to be the most significant source of carcinogenic risk, accounting for 99% of the total carcinogenic risk. Meanwhile, it is recommended to equip drilling workers with gas masks and develop all-oil biodiesel drilling fluid.