ABSTRACT

This study investigates heavy metals and naturally occurring radionuclide materials (NORM) possible presence and pollution rates in oil-based drilling fluids system used to drill an oil and gas well. It also estimates the health risks of the drilling crew due to their exposure to these substances. Measurements from Atomic Absorption Spectrometry (AAS) revealed that, the concentrations of the metals present in the drilling mud samples varied significantly and decreased in the order of Zn > Al > Ni > Pb > Cr > Cu > As > Hg > Cd. Generally, amongst all the heavy metals considered, mud sample C had the highest heavy metal concentration when compared to samples A and B, respectively. When compared with the recommended maximum allowable limits, Cd and Ni were found to be higher than the International Reference Standard by factors of Cd (3 mg/kg) and Ni (50 mg/kg). The cancer risk obtained from this present study are 1.1 × 10⁻³ and 7.7 × 10⁻³ for the drilling crew, which is slightly above the acceptable risk range considered by the environmental and regulatory agencies. The concentrations of radioactive substances as obtained from analysis, show that K-40 is the dominant radionuclide in the samples with the highest value slightly twice the standard reference value. The concentrations of Ra-226 and Th-232 activity in the mud samples were found to be lower when compared with the International Reference Level. Also, the X-ray diffraction analysis helped to identify 16 very important/useful minerals in the three mud samples under consideration. The higher elemental concentrations of potassium and aluminum silicate found in sample C can be credited to the elevated heavy metal-content found in the mud samples. Significantly, these exposure risks found in this present study indicate that the potential health risks due to radiological activities may not pose short – but long-term risks to the drillers.

摘要

本研究调查了用于钻探油气井的油基钻井液系统中可能存在的重金属和天然存在的放射性核素材料 (NORM) 和污染率。它还估计了钻井人员因接触这些物质而造成的健康风险。原子吸收光谱法 (AAS) 的测量结果表明，钻井泥浆样品中存在的金属浓度变化很大，并按 Zn > Al > Ni > Pb > Cr > Cu > As > Hg > Cd 的顺序降低。一般来说，在所有考虑的重金属中，泥浆样品 C 的重金属浓度分别高于样品 A 和 B。与推荐的最大允许限值相比，发现 Cd 和 Ni 比国际参考标准高出 Cd (3 mg/kg) 和 Ni (50 mg/kg) 的因素。从本研究中获得的癌症风险为 1.1 × 10^-3和 7.7 × 10 ^-3对于钻井人员来说，这略高于环境和监管机构认为的可接受风险范围。分析得到的放射性物质浓度表明，K-40 是样品中的主要放射性核素，其最高值略高于标准参考值的两倍。与国际参考水平相比，发现泥浆样品中的 Ra-226 和 Th-232 活性浓度较低。此外，X 射线衍射分析有助于在所考虑的三个泥浆样品中识别出 16 种非常重要/有用的矿物。样品 C 中发现的较高元素浓度的硅酸钾和硅酸铝可归因于泥浆样品中发现的较高的重金属含量。显著地，