The accumulation and increase in radionuclide activities of NORMs beyond permissible levels, will lead to health hazards and environmental damages if proper measures are not taken to control their occurrence as well as protect the lives of drillers and the environment. Therefore, evaluations and risk assessments of subsurface lithofacies is inevitable in order to protect people and the environment. Lack of existing Federal environmental regulations to address the presence of NORMs in oil and gas exploration activities in Nigeria, gives credence to this study. However, before these regulations can be developed, adequate research knowledge is needed to better understand the occurrence and distribution of Norms in subsurface lithofacies, as well as quantify the hazards posed by these NORMs to the people in the environment. This study then investigates the occurrence of natural radiation in lithofacies of an oil field region in Niger-Delta area using Hyper Germanium (HPGe) detector. Six (6) samples of different subsurface layers of lithofacies were collected during drilling, and analyzed. The results showed that the measured activity concentration of 238U decreased as the depth increased; the activity concentration of 232Th ranged between 11.8 ± 9.29 Bq/kg and 23.1 ± 8.43 Bq/kg, while the activity concentration of 4 K ranged from 161.8 Bq/kg to 245.4 Bq/kg. The estimated radiological risks such as absorbed dose rates, annual effective dose rates, radium equivalent index, external hazard index and internal hazard index were determined. The mean values for the estimated radiological parameters were 12.32 nGyh-1, 15.1049 Svy-1, 44.7720 Bqkg-1, 0.1209 and 0.1318 respectively. The gamma index estimated for the samples used were within the standard values recommended by Unscear, 2000. Significantly, this study reveals a distinctive decrease in 232Th activity with depth within the area under consideration. Based on the compared results, the measured radioactive concentrations and estimated radiological risks were below international reference values.

中文翻译：

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尼日尔三角洲地区油田岩相中自然辐射的评估及其对健康的影响。

如果不采取适当措施来控制NORMs放射性核素的积累并增加其安全性，并保护钻工的生命和环境，则其累积和增加的放射性核素活性将超过其允许水平，从而对健康和环境造成损害。因此，为了保护人类和环境，地下岩相的评估和风险评估是不可避免的。缺乏解决尼日利亚石油和天然气勘探活动中存在NORM的现行联邦环境法规，为这项研究提供了保证。但是，在制定这些法规之前，需要有足够的研究知识，以便更好地了解地下岩相中规范的发生和分布，以及量化这些NORM对环境人员造成的危害。然后，本研究使用高锗（HPGe）探测器调查了尼日尔三角洲地区油田地区岩相中自然辐射的发生。在钻探过程中收集了六（6）个岩相不同地下层的样品，并进行了分析。结果表明，随着深度的增加，测得的238U活度浓度降低。232Th的活性浓度在11.8±9.29Bq / kg至23.1±8.43Bq / kg之间，而4K的活性浓度在161.8Bq / kg至245.4Bq / kg之间。确定了估计的放射风险，例如吸收剂量率，年有效剂量率，镭当量指数，外部危害指数和内部危害指数。估计放射学参数的平均值为12.32 nGyh-1、15.1049 Svy-1、44.7720 Bqkg-1、0.1209和0。分别为1318。估计所用样品的伽玛指数在Unscear，2000建议的标准值之内。有意义的是，这项研究表明232Th活性随所考虑区域的深度而显着降低。根据比较结果，测得的放射性浓度和估计的放射风险低于国际参考值。