EVALUATION OF SELF-ATTENUATION COEFFICIENTS OF OIL-PRODUCED SCALES FOR GAMMA-RAY SPECTROSCOPIC ANALYSIS

This study focuses on the evaluation of self-attenuation correction factors (C-f) and linear-attenuation coefficients (mu) of scale samples, produced from the oil fields. This was performed using Eu-152 point source at the optimal geometry found (i.e., 3 mm). The scale samples were of apparent density ranging 1.04 - 3.08 g cm(-3). The results illustrated that self-attenuation correction values were as high as 5.08 for the most dense samples at gamma-energy line of 45.5 keV. High correlation was observed by Pearson matrix between self-attenuation correction factor and sample density (correlation coefficient of 0.967 at gamma-energy of 45.5 keV). A simplified model of the relationship between these variables was proposed. The remarkable finding was that when scale sample density increased self-absorption extended to occur to a higher energy line. Hence, self-attenuation correction was negligible at c-energies of 122, 222, and 344 keV for samples with density ranging 1.04-1.41, 1.45-2.04, and 2.12-3.08 g cm(-3), respectively. Since linear attenuation coefficient is material sensitive, it was calculated for each sample. Analysis of variance (ANOVA) reflected the linear relationship between linear-attenuation coefficient and sample density up to 344 keV which disappeared thereafter. The data obtained allowed an accurate determination of the concentrations of c-emitters in scale samples within the energy range of 45.5-1408 keV.