A century of oil and gas exploration in Albania: assessment of Naturally Occurring Radioactive Materials (NORMs)

TL;DR

This study assesses Naturally Occurring Radioactive Materials (NORMs) in Albania's oil and gas regions, revealing low activity levels and providing a basis for future radiological safety planning in the area.

Contribution

It provides the first extensive survey of NORMs in Albania's oilfields, combining gamma-ray spectrometry with mineralogical analysis to inform radiological risk assessment.

Findings

Low activity concentrations of radionuclides in samples

No significant disequilibrium in decay segments observed

Outdoor gamma dose rates below global average

Abstract

Because potential Naturally Occurring Radioactive Materials (NORMs) generated from oil and gas extractions in Albania have been disposed without regulatory criteria in many decades, an extensive survey in one of the most productive regions (Vlora-Elbasan) has been performed. Among 52 gamma-ray spectrometry measurements of soil, oil-sand, sludge, produced water and crude oil samples, we discover that relatively low activity concentrations of 226Ra, 228Ra, 228Th and 40K, which are 23 +/- 2 Bq/kg, 23 +/- 2 Bq/kg, 24 +/- 3 Bq/kg and 549 +/- 12 Bq/kg, respectively, come from oil-sand produced by hydrocarbon extraction from molasses formations. The mineralogical characterization together with the 228Ra/40K and 226Ra/40K ratios of these Neogene deposits confirm the geological and geodynamic model that predicts a dismantling of Mesozoic source rocks. The average activity concentrations (+/- standard deviations) of the radium isotopes (226Ra, 228Ra) and of the 228Th and 40K radionuclides in soil samples are determined to be 20 +/- 5 Bq/kg, 25 +/- 10 Bq/kg, 25 +/- 9 Bq/kg and 326 +/- 83 Bq/kg, respectively. Based on these arguments, the future radiological assessment of other fields in the region can be strategically planned focusing on the oil-sands from molasses sediments. No disequilibrium in the 228Ra decay segment has been observed in soil, sludge and oil-sand samples within the standard uncertainties. After a detailed radiological characterization of the four main oilfields, we can conclude that the outdoor absorbed dose rate never exceeds the worldwide population weighted average absorbed dose rate in outdoor air from terrestrial gamma radiation.