Investigating Drilling Muds in Deep Sea Sediments: Northeast Gulf of Mexico

Sediment cores were collected in the Gulf of Mexico (GoM) to investigate the sediment record of synthetic based drilling mud (SBM) and evaluate the scope of the Deepwater Horizon (DwH) oil spill. Synthetic drilling mud containing barium sulfate is used at oil drilling sites to control the temperature and pressure inside the well during drilling activities. On April 20, 2010, the DwH oil spill triggered the release of over 4 million barrels of oil in the ocean. Attempts were made to stop the flow of oil from the well, including pumping synthetic barium sulfate (barite) drilling mud into the well. This failed to stop or reduce the oil flow and nearly 30,000 barrels of drilling mud were dispersed onto the seafloor. Due to the unique characteristics and uses of SBMs, they may be used as tracers in deep-sea sediments to investigate the environmental implications of barium from oil drilling and assist with the evaluation of the implications of barium increases in benthic environments. The objectives of this research are as follows: (I) Determine if there is variability of barium in sediments in northeast the GoM, (II) If yes, determine if this can be attributed to oil drilling activities and/or other anthropogenic activities. Sediment cores were analyzed by X-ray Fluorescence (XRF) spectroscopy to determine the elemental composition of sediment samples and evaluate variability in Ba concentrations. Short lived radioisotope analyses (210Pb) were conducted to provide age control over the past ~100 years to determine timing of Ba input. Preliminary findings indicate that sediment surrounding the DwH site exhibit increased concentrations of Ba at the surface, likely due to the DwH event. Samples collected from areas of active drilling exhibit spikes in Ba concentrations at various intensities possibly indicating drilling activities from surrounding wells. This research can be used to evaluate the effectiveness of regulations on synthetic drilling mud put in place to prevent contamination and toxicity to benthic communities, as well as provide a potentially more persistent tracer of oil spill events. This will help further determine the spatial extent of the DwH event on the seafloor as well as its preservation in the sedimentary record.

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