PHYSICAL AND CHEMICAL ASSOCIATIONS OF URANIUM AND HYDROCARBONS IN THE MARCELLUS SHALE

The Marcellus Shale natural gas reservoir is enriched in uranium and other redox sensitive metals. Hydraulic fracturing (fracing) to extract natural gas from these shales may alter pH and eH conditions causing many of these metals to become locally mobile within the subsurface. In this study, Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS) was used to map the elemental compositions of core and outcrop samples of the Marcellus Shale collected from western NY and PA. Six shale samples were analyzed and total organic content (TOC) varied between 3.13 wt% and 8.55 wt%. Hydrocarbons were unevenly distributed, as shown by varied intensity of hydrocarbons throughout the elemental maps. Uneven distributions of uranium were also present in samples with concentrations ranging from 10.2 ppm to 53.4 ppm. Preliminary results indicate that uranium is physically and chemically associated with hydrocarbons. High concentrations of barium, ranging from 902 ppm to 2000 ppm, also exist within the samples. Barium is more evenly distributed within the samples. However, barium has not been determined to be directly associated with hydrocarbons.