Fractionated drilling wastes originating from shale gas exploration in the Baltic Basin in Pomerania were subjected to the measurements of mean activity concentrations of naturally occurring radioactive materials (NORMs).To better understand rock structure and texture, the X-ray diffraction analysis (XRD) and scanning electron microscopy(SEM) observation were used. To compare activity concentration of radionuclides in bulk wastes and fractionated samples (the latter were obtained through a sieve analysis), they were analyzed by gamma-ray spectrometer, both before and after the Dean-Stark extraction. After fractionation, three different size ranges were distinguished. Radiological indices were estimated by comparison with the levels recommended by International Association of Oil and Gas Producers (OGP) and the equivalent absorbed dose was determined with respect to appropriated disposal of cuttings. The results show that the drilling cuttings from the Ordovician period have a natural radioactivity level comparable to other rocks with the same lithology (potassium K-40 800-992 Bq/kg and thorium Th-232 23.3-30.8 Bq/kg) and they do not exceed acceptable levels of total absorbed dose rate. The average global value is 55 nGy/h and the average absorbed dose rate in outdoor air 1 m above the drilling cuttings was 54.1nGy/h. The relation between particle size and natural radioactivity indicates that concentration of radionuclides increases as the fractions size decreases.
Authors
Additional information
- DOI
- Digital Object Identifier link open in new tab 10.5277/ppmp150213
- Category
- Publikacja w czasopiśmie
- Type
- artykuł w czasopiśmie wyróżnionym w JCR
- Language
- angielski
- Publication year
- 2015
