Correlating NORM with the mineralogical composition of shale at the microstructural and bulk scale

Hydrocarbons produced via hydraulic fracturing of shale formations frequently contain elevated quantities of Technologically Enhanced Naturally Occurring Radioactive Materials (TENORM) that are difficult to dispose of and can be harmful to the environment. This research investigates the elemental composition of seven major shale formations at the bulk and microstructural scale to better understand the relationship between major naturally occurring radioactive elements (NORM) and organic phases within shales. Bulk mineralogy analysis was performed via powder X-ray diffraction to identify which shales were ideal for hydraulic stimulation based on the content of ductile and brittle minerals. To complement the XRD, Quantitative Evaluation of Minerals by Scanning Electron Microscopy (QEMSCAN®) was performed to identify non-crystalline phases and provide spatial mapping of the minerals through the shale samples. In addition, XRD and QEMSCAN were used to determine the total sulfur and carbonate content as this greatly contributes to the acidity of the shale and subsequently, U and Th migration. Select samples were characterized by scanning electron microscopy - energy dispersive x-ray spectroscopy (SEM/EDX) to reveal the presence of heavy metals (i.e. U, Pb) near hydrocarbon-rich regions of the shale. The NORM content and organic content were also correlated using gamma well logging.