Quantitative Environmental Radiologic Assessment of Oil and Gas Exploration Activities Using Ra Concentration to Estimate Po and Pb Dose

Exploration activities of hydrocarbon reservoirs have resulted in the release of naturally occurring radioactive material (NORM) into the environment, exposing them to workers and members of the public. Radium-226 and its progeny (Rn, Pb and Po) in the U-series and Ra in the Th-series are key isotopes that are released into the environment. Excessive radiation derived from oil and natural gas activities can potentially result in adverse health effects and increased cancer risk; thus, this study is focused on the evaluation of radiation exposure in Southern Pennsylvania, where large-scale conventional drilling and newer technologies have been carried out for over a century. We collected and analyzed a suite of soil/sediment cores and grab samples; analyzed for Po, Pb, Ra and Ra; and evaluated the fraction of Ra derived from hydrocarbon exploration activities. The vertical variations of the activity ratios of Pb/Ra and Po/Pb for soil and sediment cores are plotted. The vertical variations enrichment factor for Ra are plotted showing the vertical variations on the extent of Ra enrichment. Using a modeling approach, an estimate of the production of Po and Pb from production well to houses are estimated. The measured activities of U- and Th series radionuclides (Ra, Rn, Pb and Po, and Ra), indicate that the estimated radiation dose does not pose any radiation health hazard to the public in Southern Pennsylvania. However, the oil and gas workers may be at risk and should be considered for radiation monitoring when working with certain infrastructure.