ANALYSIS OF THE NATURALLY OCCURRING RADIONUCLIDES OF PRODUCED WATERS FROM THE MARCELLUS FORMATION

The black shales of the Appalachian basin have gained widespread attention over the last several years. It has been suggested that the low porosity shales of the Middle Devonian Marcellus Formation contain up to 500 TCF of gas (Engelder and Lash 2008). While drilling within these formations was not considered attractive to companies in the past, technological advances in horizontal drilling and hydraulic fracturing have made extraction from these unconventional source rocks cost effective. Concerns persist over how the wastewater is being handled, the fate of the remaining fluid that has not returned to the surface, and the potential impacts to the environment.

Attention has been directed at whether hydraulic fracturing mobilizes the naturally occurring radionuclides within the Marcellus Formation into the ground or surface waters, and potentially to the public water supply. Available data show that water samples collected from drill sites around Pennsylvania typically contain relatively high concentrations of radium, and, in some cases, dissolved uranium. However, no harmful or elevated levels of radiological contaminants along Pennsylvania creeks and rivers have been detected.

Our research is focused on understanding what factors influence the mobilization of radionuclides as a result of hydraulic fracturing. Research efforts have been directed at determining the best analytical methods to obtain quantitative results from water samples with high TDS to better assess whether these concerns pertaining to the environment or to public heath are validated.

Preliminary results suggest that neither uranium nor thorium is being transported in the fluids. Radium was detected in the samples, ranging from 5100 to 12000 pCi/L; significantly above the drinking water limit of 5 pCi/L set by the Environmental Protection Agency.

It is difficult to categorically state that hydraulic fracturing the sole reason for the presence of radionuclides in the water samples. It has been noted that radium concentrations increase with time from fracturing, and the Marcellus Formation has low water saturation levels, suggesting that the formation may imbibe water. Further analysis of water samples will allow for a better understanding of the impacts of hydraulic fracturing.