Toxicity assessment of approved drilling mud additives in the oil and gas sector

Approval by Alberta Energy and Utilities Board of the surface disposal of drilling fluids has been announced under the jurisdiction of the Drilling Waste Management guideline. Disposal is allowed without toxicity testing if the fluid is consistent with water based materials as opposed to oil based, and all additives have been pre-approved. The list of additives is compiled by the Petroleum Services Association of Alberta and additives must pass the bacterial luminescence test to be included. This paper examines the question of whether the bacterial luminescence test provides an adequate degree of ecological protection for surface disposal. The study consisted of subjecting over 90 per cent of the additives to a multitrophic level examination (microbes, plants, invertebrates, fish), followed by ranking and consolidation into a toxicity index for comparison to the bacterial luminescence test results. Overall, there was good agreement and the results support the multitrophic level approach because a number of the additives cannot be adequately evaluated by the bacterial luminescence alone