Characterization of Naturally Occurring Radioactive Material (NORM) Generated from the Lower Cretaceous Carbonate Formations in the Arabian Peninsula and Gulf

Abstract

For most of the petroleum reservoirs in the world, the impact of the mother nuclides such as uranium-238 on the deposition of radioactive materials a.k.a. NORM from the formation and particularly as mineral scales adherent to tubulars and other equipment is considered insignificant. Uranium is regarded as insoluble in the reservoir formation and the prevailing understanding is that dissolved radium is not generated necessarily by U and Th in solution. Consequently, “uranium scale”, as a technical term, seems to be non-existent in the oil and gas industry. However, gamma spectroscopy and chemical analysis of NORM scale samples of carbonate origin, performed in the course of this research, has proven that they actually can contain uranium. A fundamental relationship between uranium and vanadium in scales is presumed. The highest specific activity of 238U in scale analyzed with gamma spectroscopy was at 11.4 [Bq/g] and supplementary chemical analysis has shown concentrations of up to 740 ppm total uranium and up to 260 ppm vanadium.

Characterization of NORM‐type scales from the oil industry through spectrometry techniques and multivariate analysis

“…29 The presence of NORM in scales from the oil industry has been studied over the years by several researchers from different regions. 9,13,14,[30][31][32][33][34][35][36][37] The 226 Ra activities determined in this work are proportional to those reported in the literature and within the limits by the International Atomic Energy Agency (IAEA). 30 The minimum activities determined for 228 Ra, in samples 3 and 6, were below the minimum activities established.…”

“…These precipitate along the scales during the production process. [8][9][10] The highest concentrations of NORM are usually found in scale that forms when radionuclides precipitate together with barite (BaSO 4 ), celestite (SrSO 4 ), and calcite (CaCO 3 ) compounds, since just like calcium, strontium, and barium, radium belongs to the family of alkaline earth metals and, therefore, has geochemical affinities with these elements.…”

“…These studies report the characterization of NORM products from oil and gas exploration over the years. 1,9,[11][12][13][14] Since the characterization of these scales contributes to a better understanding of their chemical compositions and their formation and deposition mechanisms, assisting to create chemical products aimed at their prevention and removal. In addition to contributing to improvements in the control and monitoring of areas subject to higher levels of exposure, changes of the use or addition of personal protective equipment, as well as improvements in procedures for routine activities, aiming to reduce the exposure time of workers in critical areas, through the determination of activities concentrations and associated radiological indices, the goal of this work was to characterize scale samples from different parts of a floating production storage and offloading (FPSO) facility, determining their chemical and mineralogical compositions through the x-ray fluorescence (XRF) 15,16 and x-ray diffraction (XRD), 17,18 respectively, and their specific activities of 226 Ra and 228 Ra, [18][19][20][21] along with associated exposure indices, by high resolution gamma spectrometry technique.…”

“…These radionuclides are practically insoluble and little mobilized by oil and water in the formation, which are pumped to the surface, however, its decay products 228 Ra and 226 Ra are soluble and are easily mobilized. These precipitate along the scales during the production process 8–10 . The highest concentrations of NORM are usually found in scale that forms when radionuclides precipitate together with barite (BaSO 4 ), celestite (SrSO 4 ), and calcite (CaCO 3 ) compounds, since just like calcium, strontium, and barium, radium belongs to the family of alkaline earth metals and, therefore, has geochemical affinities with these elements.…”

“…The evidence of the existence of norm in the oil industries aroused the interest of researchers from all over the world, who started to evaluate the existing levels of radiation and the risks caused by these residues. These studies report the characterization of NORM products from oil and gas exploration over the years 1,9,11–14 …”