**1. Introduction**

Most of the natural radionuclides in wastes from crude oil exploitation were firstly discovered in the beginning of the last century. More types of industries have been identified dealing with

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materials containing enhanced levels of natural radionuclides, which are summarized as TE-NORM (technologically enhanced naturally occurring radioactive materials). Naturally occurring radionuclides are present at varying concentrations in the Earth's crust and can be concentrated and enhanced by processes associated with the recovery of oil and gas. This "enhanced'' NORM, often known as TE-NORM, can be created as a result of industrial processes and human activity, and in addition, can be the by-product of oil, gas production. One of the important examples that can contain elevated levels of NORM, and the radioactive materials may migrate from site to site as the materials and equipment are reused are sludge, pipe scales, produced water, and drilling mud.

Transportation or decay of radioactive elements produces other radionuclides (daughters) from the reservoir to the surface with the produced oil and gas carried out under certain conditions dependent upon pressure, temperature, acidity. NORM with the oil, gas, and water mixture migrate and accumulate in scale, sludge, and scrapings during the production process. Moreover, they form a thin film on the interior surfaces of gas-processing vessels and equip‐ ment. The geological formation is considered as important parameters at determining the level of NORM and it was found that the accumulation can vary from one site to another depending on it.

There are three types of radiation emitted by NORM, namely:

⋅ Alpha (α) ⋅ Beta (β) ⋅ Gamma (γ)

Alpha particles are considered as internally hazardous if a radioactive source of alpha-emitting particles is inhaled or ingested. While beta particles have one (negative) charge and interact more slowly with the material, they are effectively stopped by thin layers of metal, wood, or plastic and considered hazardous only if a beta-emitter source is ingested or inhaled. Gamma emitters are associated with alpha, beta decay with high-energy electromagnetic radiation that interacts lightly with matter. Gamma rays are best shielded by thick layers of lead or other dense materials and are considered as an external hazard to human bodies. Figure 1 details the origins of NORM in the recovery process [1].
