Microsoft Word - 30-3086_s_ETASR_V9_N5_pp4741-4744 Engineering, Technology & Applied Science Research Vol. 9, No. 5, 2019, 4741-4744 4741 www.etasr.com Kareem et al.: Surface and Deep Soil 222 Rn Gas Exhalation Comparison Surface and Deep Soil 222 Rn Gas Exhalation Comparison A Case Study in Tawke, Duhok, Northern Iraq Idrees M. Kareem Radiation Department, Duhok Environment Office, Duhok, Northern Iraq idris.majeed@yahoo.com Lokman A. Abdulkareem Department of Petroleum Engineering, University of Zakho, Zakho, Northern Iraq lokman.abdulkareem@uoz.edu.krd Hanaa I. Al-Barudi Department of Physics, University of Mosul, Mosul, Northern Iraq hana_hh200012@yahoo.com Abstract— In this study, 13 different surface locations and 20 mud samples were collected during drilling, from one of the oil wells in the Kurdistan region of Iraq. The samples were taken at different well depths. RAD7 technique was used for finding the radon concentration. The smallest values in soil and surface were 14.12±8.59 and 16±4.24Bq/m3 and the highest were 93.25+21.72 and 137±8.76Bq/m3 respectively. The difference in the depth and surface formation shows the surface formation over depth ratio. The exhalation rate recorded value of the surface was generally higher than that of the depth formations. The exhalation results were finally compared with the recommended values of the International Atomic Energy Agency (IAEA) levels. The data show that it was less than the standards of IAEA. Keywords-NORM; surface geological formation; oil well; 222 Radon gas; exhalation rate; RAD7 I. INTRODUCTION Natural radioactivity is more than the background radiation in oil drilling. Since the ‘80s some regulatory agencies paid attention to the Naturally Occurring Radioactive Material (NORM) issues related to hydrocarbon production [1]. Gamma radiation that comes from waste has an extremely wide range [2, 3]. Activities relative to uncontrolled releasing and enhanced NORM levels cause environment contamination. These kinds of risks can be reduced by the adoption of checks to recognize the NORM source, controlling NORM waste and polluted equipment, and protecting workers. The 238 U and 232 Th are radioactive materials situated into rock formations and soil. Unstable radioactive chemical elements of this kind create other radionuclides, which bring on certain conditions (temperature, pressure, acidity, etc.) into the surface layer and subsurface environment. They are mobile with a probability of transmitting from the reservoir to the surface during the extraction of crude oil products. This research aims to study radon gas and its exhalation in terms of area and mass ratio, considering depth. More than one samples come from the same formation, although their distance is of the order of hundreds of meters. Samples were collected from different locations that have a spatial geological formation. In Saudi Arabia, radon concentration in the soil ranges from 75 to 220Bq/m 3 [3], with a reported mean value of 4561Bq/m 3 [4]. In India, the radon gas in soil is 7.46±0.69kBq/m 3 [5]. The radon exhalation rate in Syria was measured as 9Bq.m -2 .s -1 [6]. The aim of the current study is to find the radon concentration by using the RAD7 technique. A total of 13 formation samples and 20 mud samples were collected in the North of Duhok Governorate during drilling. Sampling was conducted at different depths, the purpose was to calculate the surface and mass exhalation rate of radon and to compare them with the findings of other studies. II. STUDY AREA The study area is located in Iraq, Northwest and in the North of Duhok Governorate, about 60km from the center of the city, in 37.161985 latitude, 43.016341 longitude. It is one of the 51 well locations that extract crude oil. The depth to reach the layer of crude oil is 2200m, so during the excavation, we can find different geological formations. III. EXPERIMENTAL PREPARATION Twenty samples of drilling mud from assorted depths (assorted formations) were gathered from the T-49 well, located in the Tawke oil field. The radon concentrations and relative depths from the collected samples are listed in Table I and the surface formation measurements are shown in Table II. The collected samples were dried in an oven at 110 o C for one day for eliminating moisture, then milled to fine powder, and finally garbled with 0.2mm mesh. This study used active mod as a solid-state determination to find the activity concentration of radon gas. The setup of the experiment is shown in Figure 1 as an active method to find radon concentration. It consisted of a plastic tube of about 1L volume made from polyvinyl chloride (PVC) as a chamber to accumulate radon. The PVC-tube was joined with a vinyl tube that contained desiccant (CaSO4) for drying the gas from humidity, and a radon monitor device. Soil samples were put in the bottom of the tube as radon exposure source, with closing sides by the PVC cover. Then the plastic-tube container was isolated via two valves adjusted at the sides of the container. The concentration was measured after putting Corresponding author: Idrees M. Kareem Engineering, Technology & Applied Science Research Vol. 9, No. 5, 2019, 4741-4744 4742 www.etasr.com Kareem et al.: Surface and Deep Soil 222 Rn Gas Exhalation Comparison the samples and leaving them in room temperature for about one month. This time was sufficient for the samples to reach radium-radon, and radon decay equilibrium. When connected to the closed loop both valves were open. The device pooled air from the container, passing it through the desiccant to the inlet filter and then to the RAD7 device into the measuring tube chamber. The air was discarded from the outlet of the RAD7 device. The radioactive element decays in the interior of the chamber, creating detected alpha (α) particles that emit progeny, especially polonium isotopes. There is a high voltage of about 2218V on the chamber walls. The RAD7 detector converts alpha radiation to electrical signal by utilizing the alpha technique and is able to separate the different electrical pulses produced from 214 Po and 218 Po with energies of 7MeV and 6MeV correspondingly. The humidity is between 4%-8%, in room temperature ranging from 20 o C to 31 o C. Fig. 1. Method of radon concentration measurement. At equilibrium state, the flux (exhalation) of radon from the sample inside the can in terms of area and mass can be measured by [7]: EA= ����.�.��/ ��� ������/� (1) EM= ����.�.��/� ��� ������/� (2) where EA is the exhalation rate in terms of area (Bq.m -2 .d -1 ) and EM is the exhalation rate in terms of mass (Bq.kg-1.h-1), CRn is the radon concentration calculated by the RAD7 detector in a Bq/m 3 , �=7.56×10 -3 h -1 is the constant of radon decay, T is the exposure time in hours, V is the volume of the can, equal to 0.001192m 3 and S is the surface area of the sample in the can, equal to 0.003847m 2 . The RAD7 works on a four-cycle mode, the data are stored in an internal memory via using the starting protocol of 2-days test. The saved value depends on the average gas concentration of radon during each break time. IV. RESULTS AND DISCUSSION The statistics of the concentration of radon into different depths and formations of Tawke area and the soil from different locations show that different depths have different concentrations of radioactive radon gas and the results are compared with the ones from the surface samples. The surface formation in general was recorded to have higher concentrations than the depth locations. The highest rate was recorded in the depth of 1100m (Euphrates formation and Khormala Formation), and the lowest ratio was recorded in the depth of 1900m (Kolosh formation and Jurbi formation), with values of 93.25±19.72, 137±8.76 and 14.12±8.59, 16±4.24Bq.m -3 respectively. The results of radon concentration vs formation and depth measurement are displayed in Figure 2. There are many factors affecting radon release from soil and rocks, such as permeability, moisture, porosity, CO2 soil concentration, temperature, and pressure. Maybe each location includes specific distinctive soil and rock properties, so the evaluation must be held accordingly [3]. TABLE I. RADON CONCENTRATIONS AND EXHALATION IN DIFFERENT DEPTHS Depth (m) Layer name Weight (g) Rn Std division (Bq/m 3 ) Radon area (mBq.m -2 .h -1 ) Radon mass (mBq.kg -1 .h -1 ) Surface Surface area 126.34 62±15.25 177.8±43.73 5.41±1.33 400 Upper Faris 129.96 85.25±7.2 244.48±20.59 7.24±0.61 500 Sandston-clayston-Upper Faris 136.02 66.25±3.8 189.99±10.81 5.37±0.31 600 Sandston-clyston- Upper Faris 132.5 40.75±21.7 116.86±62.29 3.39±1.81 700 Sandston-clyston- Upper Faris 145.12 52.25±10.17 149.84±29.17 3.97±0.77 800 Lower Faris clayston 136.34 57.5±10.87 164.9±31.17 4.65±0.88 900 Euphrates 145.1 40±16.79 114.71±48.15 3.04±1.28 1000 Euphrates 129 47±11.46 134.79±32.86 4.02±0.98 1100 Euphrates 137.8 93.25±19.72 267.42±56.55 7.46±1.58 1200 Pelaspi 126.8 69±8.98 197.88±25.75 6±0.78 1300 Pelaspi 142.2 63.5±12.15 182.1±34.84 4.93±0.94 1400 Jurkes 138 24±3.36 68.83±9.64 1.92±0.27 1500 Jurkes 126.04 29±8.44 83.17±24.2 2.54±0.74 1600 Jurkes 149.69 24.25±7.93 69.54±22.74 1.79±0.58 1700 Jurkes 150.6 23.75±5.85 68.11±16.78 1.74±0.43 1800 Kolosh 153.34 27.05±4.71 77.6±13.51 1.95±0.34 1900 Kolosh 129 14.12±8.59 40.52±24.63 1.21±0.73 2000 Kolosh 137.58 18.23±7.21 52.3±20.68 1.46±0.58 2100 Kolosh 137.15 23.01±1.32 65.98±3.79 1.85±0.11 2200 Kolosh 140.34 30.50±5 87.47±14.34 2.4±0.39 Max 93.25±21.72 267.42±62.29 7.46±1.81 Min 14.12±8.59 40.52±3.79 1.21±0.11 Average 44.53±9.52 125.0±26.45 3.52±0.74 Engineering, Technology & Applied Science Research Vol. 9, No. 5, 2019, 4741-4744 4743 www.etasr.com Kareem et al.: Surface and Deep Soil 222 Rn Gas Exhalation Comparison In the underground, there is radon movement depending on compaction, brittle, lithology, porosity, etc. [8, 9]. The raises of Radon gas emission were caused by soil moisture, but if there is a saturation of soil pores, the emission will be inhibited. The CO2 behaves as a radon carrier gas into the soil, enhancing the 222 Rn concentration into the soil atmosphere [10]. Note that the studied samples’ maximum radon concentration level is acceptable [11]. Table III shows the comparison of this study results with the results of other works regarding radon concentration and exhalation. The present study shows that the radon rate was higher than the study done in Iraq-Kurdistan, Egypt, Pakistan and India, while it was lower than in Iraq-Baghdad and Iraq-Erbil. Anyhow, this value is lower than the acceptable level which should be less than 300Bq.m -3 [12]. Comparing with the mass exhalation rate in India, Osaka-Japan and Catania- Italy, the value of the average exhalation rate of this study was lower. In general the results were less than the mean world value which is 57600mBq.m -2 .h -1 [13]. In term of mass, this study results were near to India and Erbil-Iraq. Fig. 2. Radon concentration in different depths and soil formations TABLE II. 222RADON CONCENTRATION AND EXHALATION IN DIFFERENT SURFACE FORMATIONS Formation Name Weight (g) Rn Std division (Bq/m 3 ) Radon area (mBq.m -2 .h -1 ) Radon mass (mBq.kg -1 .h -1 ) Jurbi formation 156.15 16±4.24 45.88±12.16 1.13±0.3 Sludge after treatment 165.85 16±5.66 45.88±16.23 1.06±0.37 Soil before treatment 165.35 66.5±11.27 190.71±32.32 4.43±0.75 Lower Faris formation 100.89 33.25±2.06 95.35±5.91 3.63±0.22 Khormala formation 170.56 137±8.76 392.88±25.12 8.86±0.57 Avana formation 128.07 39.5±13.87 113.28±39.77 3.4±1.19 Waste Mud 130.25 80±13.44 229.42±38.54 6.77±1.14 Pelaspi formation 160.1 47±4.24 134.78±12.16 3.24±0.29 Bakhtyari formation 142 31±8.49 88.9±24.35 2.41±0.66 Jurkes formation 134.27 55.5±6.81 159.16±19.53 4.56±0.56 Upper Faris formation 154 57.5±7.14 164.89±20.47 4.12±0.51 Qamchqa formation 161.25 123.25±17.34 353.45±49.73 8.43±1.18 Sheranish formation 133.21 59.35±18.11 170.2±51.93 4.91±1.5 Max 137±8.76 392.88±25.12 8.86±0.57 Min 16±4.24 45.88±12.16 1.13±0.3 Average 58.60±9.34 168.06±26.78 4.38±0.71 TABLE III. RADON EXHALATION RATE IN TERMS OF AREA AND MASS Location 222- Rn concentration (Bq/m 3 ) 222- Rn (mBq.m -2 .h -1 ) 222- Rn (mBq.kg -1 .h -1 ) Reference Tawky-T49. Various well depths and formations 44.53+9.52 58.60±9.34 125.08±26.45 168.06±26.78 3.52±0.74 4.38±0.7 Present study India 7.46±0.69 246.63–1100 7.17–31.98 [5, 14] Turkey 1476 - [15] Erbil-Iraq 361.77±3.79 67.962-515.167 1.882- 12.630 [16] Iraq-Kurdistan 15.638±7.38 5670-14020 536.09-1324.12 [17] Osaka-Japan - 10.8 - [18] Hawaii - 9.0±226 - [19] Japan 1260 - [20] Germany - 7200-63000 - [21] Catania-Italy 43.1±6.7 - [22] Baghdad-Iraq 1337.55 1059.5 61.25 [23] Alexandria-Egypt 7 464.4 - [24] Saudi-Arabia 75–220 [3] Pakistan 666±55 5860±1200 - [25] Bengaluru-India 497±173 78588±27576 [26] Mean world value <300 57600 - [12, 13] V. CONCLUSION There are differences on the amount of radon gas and its exhalation rate, depending on the depth and the surface formation soil. 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