Research Product

The Environmental Research Laboratory, Gulf Breeze, Florida, carried out a research program from 1976-1984 to evaluate the potential impact of drilling fluids on the marine environment. Research efforts were accomplished mainly through cooperative agreements with academic institutions and contracts with private laboratories; program direction and toxicity testing with used and generic drilling fluids were provided by the Gulf Breeze Laboratory. Results of research activities reported from this research program showed that drilling fluids are toxic to marine animals at certain concentrations and exposure regimes. Further, drilling fluids can adversely affect animals, especially benthos, through physical contact by burying or altering substrate composition. The fluids, or components of the fluids, also can exert effects by disrupting essential physiological functions of organisms. While some components (pentachlorophenol, for example) that are toxic are no longer permitted for fluids released on the OCS, research indicated that a 'diesel' contaminant is a toxic component of used fluids recently collected from the Gulf of Mexico. Tests also showed that the addition of #2 fuel oil (diesel) or mineral oil increased the toxicity of laboratory-prepared drilling fluids. Models developed to predict the impact of drilling fluids on open, well-mixed, and relatively deep (>20 meters) marine environments suggested that under normal operating conditions most detectable adverse effects should be limited to within several hundred meters of the point of discharge. Possible exceptions to this generalization could occur when drilling conditions differ from normal or when drilling rigs are located near sensitive biological areas, such as coral reefs, or in poorly flushed areas. Incomplete research data were acquired in some areas, and further research would be desirable in other areas. For example, models developed to predict the fate and effects of drilling fluids should be field tested to validate the assumptions and inputs into the models. Special emphasis should be placed on discharges from multiple development rigs. Also, data and methodology are needed on the effects of additives, particularly biocides and chemicals to improve lubricity, on the toxicity of drilling fluids. Additional information on sublethal and chronic effects of the drilling fluids on sensitive life stages of organisms, particularly benthic organisms, would be useful in preparing hazard assessments. Another area for future research is the impact of drilling fluids that contain diesel oil, or chemicals used in place of diesel oil, on structure and function of benthic communities.