**2.4. NORM in produced water**

**2.2. NORM in sludge**

**Country/region**

92 Advances in Petrochemicals

Egypt/oil field

Other countries

contain large amounts of barium.

**2.3. NORM in natural gas**

Radioactive molecules containing radium which were not incorporated into scale can be found in sludge, produced sands, and produced waters. Before the treatment investigations, the activity concentrations of the main three radium isotopes were measured in sludge [41]. It is found that the average activity level of Ra226, Ra228, and Ra224 for samples taken from Abu Rudeis region, Government of Sinai–Egypt, were 11950, 1750, and 1900 Bq/kg, respectively. Due to the accumulated TE-NORM wastes in huge amounts and release of high activity concentrations to the environment and the workers, treatment approaches are suggested to reduce the human and environmental hazard potential. Sludge is composed of dissolved solids which precipitate from produced water as its temperature and pressure change. Sludge generally consists of oily, loose material often containing silica compounds, but may also

Abu Rudeis 68.9 24 [33] Gabal El Zeit 14.8 4.3 [34] Badr El Din 31.4 43.3 [34] Red Sea 195 897.8 [35] Western desert 59.2 244.5 [35]

Australia 20–70 [36] USA 70.8 [37] Algeria 1–950 [38] Tunisia 4.3–658 [39] UK 1–1000 [40]

**Table 4.** Activity of 226Ra (U-series), 228Ra (U-series), and 40K in the TE-NORM in Egypt and some countries

**Activity (Bq/g)**

**226Ra 228Ra**

**Ref.**

Radon is a radioactive noble gas, present in varying level in natural gas in oil and gas forma‐ tions. In the absence of natural gas, radon easily dissolves in the light hydrocarbon. Radon usually follows the gas stream when produced with the oil and gas. If the natural gas is fractionated, higher percentage of radon can concentrate in the propane streams and lower degree in the ethane streams. Most of the radon decay products are found in ambient aerosols, airborne particulates, or surfaces. Most radon progeny are short-lived, with the exception of Po210 and Pb210, which have relatively long half-lives of 138 days and 22.6 years, respectively. Formation of thin radioactive films on the inner surfaces of gas-processing equipments, such Formation water at oil and gas reservoirs called produced water float to the surface during oil and gas production. However, gas reservoirs typically produce smaller quantities whereas the oil reservoirs can contain large volumes of formation water. Water is injected into the reservoir to maintain pressure and or maximize production in most fields. The produced water stream can be one of the largest waste products, by volume produced from oil and gas industry. It was found that the produced water contains a complex mixture of inorganic compounds, such as dissolved salts, trace metals, suspended particles and organic compounds such as dispersed and dissolved hydrocarbons, organic acids, and residual chemical additives such as scale and corrosion inhibitors that are added into the hydrocarbon production process. Technologies of treatment depending on the application and particular field conditions. Also, it is to consider include combinations of gravity and / or mechanical separation and chemical treatment, and may include a multistage system, typically including a parallel plate separator, followed by a gas flotation cell or hydrocyclone. For disposal of produced water to sea, some criteria should be considered to reduce the volume of produced water, such as:

Select adequate well management during well completion to minimize water production;

Minimize water production by recompletion of high water-producing wells;

To be economically feasible, use down hole fluid separation techniques, where possible.

For reducing environmental hazards related to residual chemical additives in the produced water stream, where surface disposal methods are used, production chemicals should be selected carefully by taking into account their volume, toxicity, and bioaccumulation potential [42]. The average worldwide activity levels of uranium (U), thorium (Th), and potassium (K) [43] and the exemption activity levels of NORM as recommended in the IAEA basic safety standards [44] were given in Tables 5 and 6. The average worldwide levels of the most common radiological indices [43] were given in Table 7. These indices include radium equivalent (Raeq), total absorbed dose (Dγr), and effective annual dose rate (EDAR).


**Table 5.** The average worldwide activity levels of uranium (U), thorium (Th), and potassium (K)


**Table 6.** The exemption activity levels of NORM as recommended in the IAEA basic safety standards


**Table 7.** The average worldwide levels of the most common radiological indices
