Disequilibrium of Naturally Occurring Radioactive Materials (NORM) in Drill Cuttings from a Horizontal Drilling Operation

Abstract

Naturally occurring radioactive materials (NORM) in solid waste or “drill cuttings” produced from unconventional drilling for natural gas extraction wells potentially pose environmental contamination risks; however, the composition and mobility of NORM in these solid wastes are poorly understood. In this study, the composition of NORM, including uranium, thorium, radium, lead, and polonium isotopes, was evaluated in three samples of drill cuttings extracted from a well drilled into the Marcellus Shale formation. Leachability of NORM in drill cuttings was characterized by leaching the solid waste with dilute acetic acid at four different pH values. The uranium-series radionuclides in cuttings and leachate samples displayed isotopic disequilibrium, suggesting some environmental mobility of radionuclides in these shale formations. Our results indicate that isotopic analysis of uranium-series radionuclides is needed for a more complete understanding of the potential environmental contamination risks associated with these solid wastes.

Radioactivity of Soil, Rock and Water in a Shale Gas Exploitation Area, SW China

“…The activity concentrations of 226 Ra in limestone and shale in the study area are slightly lower than those in Kenya [34]. However, the activity concentrations of 226 Ra in the shale in this study are within the results of northern PA in the USA [35]. The difference in radioactivity levels in different areas can be attributed to differences in the local geological and geochemical conditions, especially for soil, and the specific levels are closely related to the type of parent rock [36,37].…”

Geochemical conditions conducive for retention of trace elements and radionuclides during shale–fluid interactions

“…The 226 Ra activity measured here is consistent with the previously reported 226 Ra activity in Marcellus shale (50-500 Bq kg À1 ). 44 The radioactivity of produced water is oen elevated, primarily due to high concentrations of Ra isotopes. Generally, produced water contains total dissolved Ra ( 226 Ra and 228 Ra) ranging between 37 and 555 Bq L À1 , whereas dissolved U concentration is typically low, ranging between 0.084 mg L À1 and 3.26 mg L À1 .…”

“…In addition to geochemical controls on Ra mobility in pore water, the physical process of alpha-recoil is an equally important mechanism for supplying Ra to pore water, especially in the context of hydraulic fracturing. 44,47 Alpha recoil is a physical process of displacement of a radioactive decay product from its initial position in a crystal lattice of a mineral Fig. 7 Autoradiographs of shale, illustrating spatial bulk radionuclide distribution within the shale studied here.…”

Investigation of produced waters radioactivity of oil and gas deposits in the Dnieper-Donets province

“…The principle of radiochemical concentration and uranium extraction is based on its sorption on the Dowex-1 anion in a hydrochloric acid medium, and thorium in a nitrate medium [16]. Samples to measure the activity of uranium and thorium were prepared by an electrochemical method.…”