Characteristics of oil mist and vapours from drilling fluids emitted from a shale shaker in an offshore test facility

Workers in the petroleum industry are exposed to oil mist and vapours generated by drilling fluids. This project aimed to characterise the aerosols and vapours emitted from two drilling fluids with different viscosities in a shale shaker room at different drilling fluid temperatures. Oil mist and vapour concentrations measured with different samplers (37-mm closed cassette with back-up charcoal tubes, IOM head with back-up charcoal tube, Gesamtstaub-Gas-Probenahme (GGP) sampler) and direct reading instruments (Phocheck and ToxiRae for vapour and GRIMM, Aerosol Particle Sizer Spectrometer (APS), MIE DataRam, SidePak� for oil mist) were compared in an onshore test facility. Results showed statistically significant differences in the oil mist and vapour concentrations sampled with the different samplers. The closed cassette yielded higher oil mist concentrations than the IOM head and GGP sampler, while the GGP yielded the highest vapour concentrations. The oil mist results are likely to underestimate actual oil mist levels due to sampling losses arising from the evaporation of hydrocarbons from the oil mist, whilst vapour concentrations may be overestimated. Results from direct reading instruments were difficult to interpret as there are no suitable calibration factors. The base oil system with a lower viscosity yielded low oil mist levels, but high oil vapour concentrations, while the opposite was found for the base oil system with a higher viscosity. An increase in temperature of the drilling fluid resulted in an increase in the vapour and oil mist concentrations. Oil vapour concentrations at temperatures ≥50�C exceeded the Norwegian Occupational Exposure limit (OEL) of 30 mg/m3 (for a 12-hours shift). Reported oil mist concentrations at temperatures ≥60�C exceeded the OEL of 0.6 mg/m3 (based on a 12-hours shift). The particle size distribution was consistent with evaporation and subsequent condensation of oil vapour being the main mechanism of aerosol generation, especially at higher temperatures. The best way to reduce oil mist and vapour exposure would be to cool the drilling fluid before it reaches the shale shaker. “”