Radiological Survey of Oil and Gas Wastes and its Health Risks in Niger Delta Region of Nigeria

Abstract

Aim: The aim of this study is radiometric survey of oil and gas wastes and its health risks in Niger Delta region of Nigeria.  Study Design: This study was purely an experimental work which involves collection of samples and laboratory analysis. Place and Duration of the Study: This study was carried out at oil and gas company waste stream facilities and waste pipe market within Niger Delta region between June 2018 and May, 2019. Methodology: Sixteen samples (4 drill cuttings, 4 pipe scales, 2 sludges and 6 produced water) were randomly collected from four waste streams in six locations within the oil and gas production facilities and used pipe market. These samples were taken to the laboratory, prepared following the ISO procedure and packaged in a porcelain bottle, sealed and kept for twenty eight days in order to ensure secular equilibrium between 238U, 232Th and their progenies and counted with high purity Germanium detector (HPGe). The activity concentration of all the radionuclides were used to determine the radiological health risks using mathematical models. Results: The lowest and highest specific activity concentrations  of 226Ra, 238U , 232Th  and 40K, in solid wastes are 5.28±1.08 and 25727.75 Bqkg-1, 3.61±0.76 and 23021.73±1041.58 Bqkg-1, 2.40±0.56 and 21468.25±1125.57 Bqkg-1 and 35.31±2.38 and 1527.73 ±86.60 Bqkg-1 respectively. In the liquid waste, the lowest and highest activity concentration of 238U, 232Th and 40K are 0.34±0.15 and 1.11±0.28 Bql-1, 0.63±0.17 and 1.06±0.18 Bql-1 and 9.60±0.66 and 14.20 ±1.04 Bql-1 respectively. 226Ra was below detectable limit in the liquid waste except in one sample (CZI). Downhole pipe scales recorded the highest activity concentration of all the radionuclides. Surface pipe scale also recorded very high activity concentration of all the radionuclides. The radiological health risk parameters assessed from the activity concentration of these radionuclide were all above the safe reference levels in downhole pipe scales and surface pipe scales while they are within the safe values in other samples. The estimated Exposure rate for both solid and liquid wastes were higher than the recommended reference level of 600 µRh-1 and the associated dose rate was also higher than reference level. Conclusion: The result of this work revealed that downhole and surface pipes from oilfield commonly used in the construction of buildings and domestic overhead tank-stands are associated with high levels of ionizing radiation which may be detrimental to human health and the environment.