Radiation Exposure to Natural Radioactivity in Crude Oil and Petroleum Waste from Oil Fields in Ghana; Modelling, Risk Assessment and Regulatory Control A dissertation presented to the: Department of NUCLEAR SAFETY AND SECURITY UNIVERSITY OF GHANA by DAVID OKOH KPEGLO (ID: 10255978) BSc (Kumasi), 2006 MPhil (Legon), 2009 In partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY in RADIATION PROTECTION June, 2015 University of Ghana http://ugspace.ug.edu.gh i DECLARATION This dissertation is the result of research work undertaken by David Okoh KPEGLO in the department of Nuclear Safety and Security, university of Ghana, under the supervision of Prof. Emmanuel O. Darko (SNAS, UG-Legon, Ghana), Prof. G. Emi-reynolds (SNAS, UG- Legon, Ghana), Prof. Rafael García-Tenorio García-Balmaseda (University of Seville, Spain), and Dr. Juan Mantero Cabrera (University of Seville, Spain). Sign: Date: 04- 03 - 2016 Kpeglo Okoh David (Student) Sign: Date: 04- 03 – 2016 Prof. Emmanuel O. Darko (Principal Supervisor) Sign: Date: 04- 03 – 2016 Prof. G. Emi-reynolds (Co-Supervisor) Sign: Date: 04- 03 – 2016 Prof. Rafael García-Tenorio García-Balmaseda (Co-Supervisor) Sign: Date: 04- 03 - 2016 Dr. Juan Mantero Cabrera (Co-Supervisor) University of Ghana http://ugspace.ug.edu.gh ii DEDICATION This research work is dedicated to the OKOH KPEGLO Family University of Ghana http://ugspace.ug.edu.gh iii ACKNOWLEDGEMENTS I will like to first of all thank the Almighty God for his strength and mercies that have enabled me to complete this research work successfully. The insightful contributions of my Supervisors, Prof. E. O. Darko, Prof. G. Emi-reynolds, Prof. Rafael García-Tenorio García- Balmaseda and Dr. Juan Mantero Cabrera who reviewed this work time after time are gratefully appreciated. I would like to acknowledge the financial support provided by the International Atomic Energy Agency in the form of an 18 months Sandwich Fellowship at the university of Seville Spain, and do thank the Radiation Protection Institute of the Ghana Atomic Energy Commission, which provided logistics and resources for carrying out sampling. All major analyses were carried out at the laboratories of the Environmental Radioactivity group, Department of Applied Physics II, University of Seville, and the contributions from various members of staff, especially, Prof. Guillermo Manjon, Dr. Ignacio Vioque, Jose Ruiz Diaz, Jose Antonio Galvan and Inma Diaz, are gratefully acknowledged. I am also grateful to the management of the Ghana National petroleum Corporation (GNPC), Tullow Ghana Limited (TGL), Saltpond offshore Producing Company Limited (SOPCL) and Zeal Environmental Technologies Limited (ZETL) for their cooperation, especially Mr. Emmanuel Arthur and Mr. Larry Ibrahim Abdul-Zahir of TGL, Mr. Ababio of GNPC, Mr. Wilfred Bentum of ZETL and Jibril Idris of SOPCL. The sampling within the communities was facilitated by the community leaders namely; Mr Kwame Abosompini, Mr Kwaku Simpah, Mr John Amoah and Oman Kyeame Suapem, and I am very grateful for their assistance. Finally, I will like to express my gratitude to all Scientists and Technicians of the Radiation Protection Institute, GAEC, especially the Director of the University of Ghana http://ugspace.ug.edu.gh iv Institute, Professor Emi Reynolds, Prof. E.O. Darko and Dr. Augustine Faanu, and to all who helped in diverse ways for this work to come to a successful completion. God bless you all. University of Ghana http://ugspace.ug.edu.gh v ABBREVIATIONS AECS Atomic Energy Commission of Syria AFPC Al-Furat Petroleum Company ALARA As Low As Reasonably Achievable API American Petroleum Institute APPEA Australian Petroleum Production and Exploration Association BSS Basic Safety Standards CHARM Chemical Hazard Assessment and Risk Management CMOS Complementary Metal-Oxide Semiconductor C-NLOPB Canada-Newfound Land Offshore Petroleum Board DJ Diffused Junction ENI Ente Nazionale Idrocarburi (Italy) EPA Environmental Production Agency E&P Exploration and Production ERA Ecological Risk Management ESRF Environmental Studies Research Fund FPSO Floating Production Storage and Offloading GAEC Ghana Atomic Energy Commission GHEITI Ghana Extractive Industries Transparency Initiative GPNC Ghana National Petroleum Corporation GSA Ghana Standard Authority HPGe High Purity Germanium HPWJ High Pressure Water Jetting University of Ghana http://ugspace.ug.edu.gh vi IAEA International Atomic Energy Agency IARC International Agency for Research on Cancer ICRP International Commission on Radiological Protection ICP-QMS Inductively Coupled Plasma Quadrupole-Based Mass Spectrometry MCA Multi-Channel Analyzer NORM Naturally Occurring Radioactive Material NRC Nuclear Regulatory Commission NRPA Norwegian Radiation Protection Authority NYSDEC New York State Department of Environmental Conversation OPAR Oslo/Paris PCB Polychlorinated Biphenyl ROPME Regional Organization for Protection of the Marine Environment RPB Radiation Protection Board SEM Scanning Electron Microscopy SSB Silicon Surface Barrier SSDL Secondary Standard Dosimetry Laboratory SOPCL Salt pond Offshore Producing Company Limited SWACO Solid Waste Authority of Central Ohio TECDOC Technical Documentation TGL Tullow Ghana Limited UKOOA United Kingdom Offshore Operation Association UNSCEAR United Nation Scientific Committee on the Effects of Atomic Radiation USEPA United States Environmental Agency University of Ghana http://ugspace.ug.edu.gh vii WEEE Waste Electronic and Electrical Equipment WERF Water Environment Research Foundation WHO World Health Organization XRD X-Ray Diffraction XRF X-Ray Fluorescence University of Ghana http://ugspace.ug.edu.gh viii Table of Contents DECLARATION……………………………………………………………………………………………………………………………i DEDICATION………………………………………………………………………………………………………………………………ii ACKNOWLEDGEMENTS………………………………………………………………………………………………………….iii ABBREVIATIONS……………………………………………………………………………………………………………………….v LIST OF TABLES…………………………………………………………………………………………………………………..….xv LIST OF FIGURES……………………………………………………………………………………………………………………..xx LIST OF PLATES…………………………………………………………………………………………………………………….xxiv ABSTRACT………………………………………………………………………………………………………………………..…….xxv CHAPTER ONE…………………………………………………………………………………………………………………….….….1 INTRODUCTION…………………………………………………………………………………………………………………………1 1.1 Background………………………………………………………………………………………………………………………………1 1.2 Statement of the Problem………………………………………………………………………………………………………...7 1.3 Research Objectives……………………………………………………………………………………………………………..….8 1.4 Significance of the study………………………………………………………………………………………………………....9 1.5 Scope and Limitation………………………………………………………………………………………………………………10 1.6 Structure of the Thesis…………………………………………………………………………………………………………….11 CHAPTER TWO………………………………………………………………………………………………………………………….12 LITERATURE REVIEW……………………………………………………………………………………………………………..12 Overview………………………………………………………………………………………………………………………………………12 2.1 NORM in the Oil and Gas Industry…………………………………………………………………………………………12 2.2 Origin of Petroleum………………………………………………………………………………………………………………..15 2.3 NORMs in the Petroleum Industry………………………………………………………………………………………….16 University of Ghana http://ugspace.ug.edu.gh ix 2.4. Radiological Characteristics of NORM……………………………………………………………………………………20 2.5 Occurrence of NORMS in Scale, Sludge and Sand…………………………………………………………………..25 2.5.1 Occurrence of NORM scale ................................................................................................... 25 2.5.2 Occurrence of NORM sand ................................................................................................... 27 2.5.3 Occurrence of NORM sludge ................................................................................................ 28 2.5.4 A summary of radionuclide concentrations of NORM .......................................................... 28 2.6 Radiation Protection Aspects of NORM…………………………………………………………………………………..29 2.6.1 Radiation exposure pathway .................................................................................................. 30 2.6.2. External exposure ................................................................................................................. 31 2.6.3. Internal exposure ................................................................................................................... 33 2.6.4. Decontamination of plant and equipment ............................................................................. 35 2.6.5. Practical radiation protection measures ................................................................................ 36 2.6.5.1. Measures against external exposure ................................................................................... 38 2.6.5.2. Measures against internal exposure ................................................................................... 39 2.7 Oil and Gas Companies in Ghana and Waste Transfer………………………………………………………………39 2.7.1 The waste transfer .................................................................................................................. 40 2.7.1.1 Associated waste ................................................................................................................. 40 2.7.1.2 Drilling waste ...................................................................................................................... 41 2.7.1.3 Produced water ................................................................................................................... 41 2.7.2 Oil and Gas Waste Management Systems in Ghana .............................................................. 42 2.7.2.1 Associated waste management ........................................................................................... 42 2.7.2.2 Drilling waste management ................................................................................................ 44 2.7.2.3 Produced water management .............................................................................................. 44 2.8 Waste Management Considerations with respect to NORMs…………………………………………………….47 2.8.1 Wastes from the decontamination of plant and equipment .................................................... 48 2.8.2 Waste management strategy and programmes ....................................................................... 49 2.8.3 Risk assessment ..................................................................................................................... 50 2.8.4 Regulatory approach .............................................................................................................. 51 2.8.5 Characteristics of NORM wastes in the oil and gas industry ................................................ 52 2.8.5. 1 Produced water .................................................................................................................. 52 2.8.5.2 Solid wastes ........................................................................................................................ 53 2.8.6 NORM Disposal Methods...................................................................................................... 54 2.8.6.1 Regulatory review and approval ..................................................................................... 56 University of Ghana http://ugspace.ug.edu.gh x 2.8.6.2 Safety implications of waste disposal methods ................................................................... 56 2.8.6.3 Significant non-radiological aspects ................................................................................... 57 2.8.6.4 Storage of solid radioactive wastes ..................................................................................... 57 2.8.6.5 Examples of disposal methods for produced water ............................................................ 58 2.8.6.5.1 Reinjection into the reservoir ...................................................................................... 58 2.8.6.5.2 Discharge into marine waters ...................................................................................... 59 2.8.6.5.3 Discharge into seepage ponds ..................................................................................... 60 2.8.6.6 Examples of disposal methods for scales and sludges ........................................................ 62 2.8.6.6.1 Discharge into marine waters ...................................................................................... 62 2.8.6.6.2 Injection by hydraulic fracturing .................................................................................. 63 2.8.6.6.3 Disposal in abandoned wells ........................................................................................ 63 2.8.6.6.4 Surface disposal ........................................................................................................... 64 2.8.6.6.5 Land dispersal .............................................................................................................. 66 2.8.6.6.6 Deep underground disposal ......................................................................................... 67 2.8.6.6.7 Recycling by melting .................................................................................................... 68 2.9 Health Effects of NORMs…………………………………………………………………………………………………………70 2.9.1 Potential effects of NORMs on the receiving environment ................................................... 71 2.9.2 Personal exposures due to NORM radiation in petroleum production .................................. 73 2.9.3 Human health risk assessment for NORMs in produced water ............................................. 73 2.9.3.1 Physical Transport of Produced Water ............................................................................... 76 2.9.3.2 Fate of Chemicals in Produced Water................................................................................. 77 2.9.3.3 Ecological Risk Assessment ............................................................................................... 77 2.9.3.4 Human Health Risk Assessment .......................................................................................... 80 2.9.3.5 Dilution model for contaminants in fish ............................................................................. 82 2.9.7 Regulatory Limitations of Produced Water Discharge .......................................................... 86 CHAPTER THREE……………………………………………………………………………………………………………………….88 RADIATION DETECTION METHODS……………………………………………………………………………………….88 Overview……………………………………………………………………………………………………………………………………….88 3.1 Background………………………………………………………………………………………………………………………………88 3.2 Detection of Gamma Radiation…………………………………………………………………………………………………89 3.2.1 Interaction of Gamma Radiation with Matter ........................................................................ 89 University of Ghana http://ugspace.ug.edu.gh xi 3.2.1.1 Photoelectric Absorption .................................................................................................... 90 3.2.1.2 Compton Scattering ............................................................................................................ 90 3.2.1.3 Pair Production ................................................................................................................... 91 3.2.2 Gamma Spectroscopy and HPGe Detectors ........................................................................... 92 3.2.2.1 Gamma Spectroscopy ......................................................................................................... 92 3.2.2.2 HPGe Detectors .................................................................................................................. 93 3.2.3 Software for gamma spectra analysis: Genie 2000 ................................................................ 95 3.2.4 Calibration of the gamma spectrometry system ..................................................................... 96 3.2.4.1 Energy calibration ............................................................................................................... 96 3.2.4.2 Photopeak efficiency calibration ......................................................................................... 98 3.2.4.2.1 Efficiency calibration for Marinelli beaker geometry .................................................. 99 3.2.4.2.2 Efficiency calibration for Petri dish geometry ............................................................ 101 3.2.5 Background measurements in the XtRa gamma detector .................................................... 102 3.2.6 Determination of Minimum Detectable Activity in gamma spectrometry .......................... 104 3.3 Detection of Alpha Radiation…………………………………………………………………………………………………105 3.3.1 Interaction of alpha particles with Matter ............................................................................ 105 3.3.2 Alpha spectroscopy and silicon detectors ............................................................................ 107 3.3.2.2 Alpha Series of Passivated Implanted Planar Silicon (PIPS) Detector ............................. 109 3.3.3 Alpha Analyst system and its calibration ............................................................................. 111 3.3.3.1 Energy calibration ............................................................................................................. 112 3.3.3.2 Efficiency calibration ........................................................................................................ 114 3.3.4 Calculation of Minimum Detectable Activity in alpha spectrometry .................................. 117 CHAPTER FOUR………………………………………………………………………………………………………………………..119 MATERIALS AND METHODS………………………………………………………………………………………………….119 Overview……………………………………………………………………………………………………………………………………..119 4.1 Description of Study Area………………………………………………………………………………………………………119 4.1.1 Saltpond Oilfield and surrounding coastal towns ................................................................ 119 4.1.1.1 Geology of Saltpond oilfield ............................................................................................. 122 4.1.1.2 Relief, Geology, Meteorology and Vegetation of Saltpond .............................................. 122 3.1.2. Jubilee Field ........................................................................................................................ 123 4.1.2.1 Geology of Jubilee Oilfield ............................................................................................... 123 4.2. Sample collection………………………………………………………………………………………………………………….127 University of Ghana http://ugspace.ug.edu.gh xii 4.2.1 Sampling of environmental samples .................................................................................... 129 4.2.2 NORM Sampling ................................................................................................................. 129 4.3 Sample preparation and measurement by alpha-particle spectrometry…………………………………….132 4.4 Sample preparation and measurement by Gamma Spectroscopy…………………………………………….136 4.4.1 Sample preparation .............................................................................................................. 136 4.4.2 Analysis of samples ............................................................................................................. 137 4.5 Calculation of Activity Concentration…………………………………………………………………………………….138 4.6 Determination of Hazard indices and risks……………………………………………………………………………..140 4.7 Radon Measurements……………………………………………………………………………………………………………..142 4.7.1 Determination of radon emanation fraction and radon mass exhalation rate ............... 143 4.8 Gross alpha and beta measurements in water samples…………………………………………………………….144 4.9 Scanning Electron Microscopy (SEM)……………………………………………………………………………………145 4.10 Estimation of massic elemental concentrations of primordial radionuclides………………………….145 4.11 Estimation of the age of scale samples………………………………………………………………………………….146 4.12 Calculation of external absorbed dose rate and annual effective dose due to radioactivity in solid matrix samples……………………………………………………………………………………………………………………………..147 4.13 Calculation of effective doses and total annual effective dose……………………………………………….148 4.14 Determination of annual effective dose from external gamma dose rate measurements…………150 4.15 Human Health Risk Assessment Model………………………………………………………………………………..151 4.15.1 Prediction of exposure concentration for the fish .............................................................. 152 4.15.2 Prediction of Radium in the Edible Part of Fish ................................................................ 154 4.15.3 Characterization of Cancer Risk ........................................................................................ 156 4.15.3.1 Fish ingestion rate (FIR) ................................................................................................. 156 4.15.3.2 Fraction of contaminated fish ingested (FR) ................................................................... 156 4.15.3.3 Exposure frequency (EF) ................................................................................................ 157 4.15.3.4 Exposure duration (ED) .................................................................................................. 157 4.15.3.5 Gastrointestinal absorption factor (GI) ........................................................................... 157 CHAPTER FIVE………………………………………………………………………………………………………………………….159 University of Ghana http://ugspace.ug.edu.gh xiii RESULTS AND DISCUSSION…………………………………………………………………………………………………..159 Overview……………………………………………………………………………………………………………………………………..159 5.1 Quality control and validation of Gamma and Alpha Spectrometric techniques………………………159 5.2 Environmental samples…………………………………………………………………………………………………………..164 5.2.1 Soil ....................................................................................................................................... 164 5.2.2 Beach sediments .................................................................................................................. 172 5.2.3 Water .................................................................................................................................... 177 5.3 NORM waste samples…………………………………………………………………………………………………………….181 5.3.1 Produce water, oily waste water, and crude oil .................................................................... 181 5.3.1.1 Radioactivity measurements in produced water ............................................................... 181 5.3.1.2 Correlation of Ra with chemical and physical properties of produced water ................... 187 5.3.1.3 Crude oil ........................................................................................................................... 195 5.3.1.4 Oily waste water and wash water ...................................................................................... 197 5.3.2 Scale, Sludge, Ash, Mud and Mud block ............................................................................. 199 5.3.2.1 Morphological and elemental composition of NORM waste Samples ............................. 218 5.4 Total annual effective dose and estimated fatality cancer risk and hereditary effects………………222 CHAPTER SIX……………………………………………………………………………………………………………………………227 SUMMARY, CONCLUSIONS AND RECOMMENDATIONS………………………………………………….227 Overview……………………………………………………………………………………………………………………………………..227 6.1 Summary and Conclusions……………………………………………………………………………………………………..227 6.2 RECOMMENDATIONS……………………………………………………………………………………………………….236 6.2.1 Regulatory Body .................................................................................................................. 236 6.2.2 Oil and gas companies ......................................................................................................... 236 6.2.3 Future Research ................................................................................................................... 237 Publication Lists…………………………………………………………………………………………………………………………..238 REFERENCES…………………………………………………………………………………………………………………………….239 APPENDIX A: Input parameters and their characterization………………………………………………………….257 APPENDIX B: Moisture and lipid content in selected species (USEPA 1996)……………………………..258 University of Ghana http://ugspace.ug.edu.gh xiv APPENDIX C: Concentration factors for edible and non-edible parts in a fish (adapted from Swanson 1983; Iyengar et al., 1980; Hamilton et al. 1992; Meinhold and Hamilton 1992)………...259 APPENDIX D: Sampling Co-ordinates for environmental samples from study area…………….260 University of Ghana http://ugspace.ug.edu.gh xv LIST OF TABLES Chapter two Table 2.1: Properties of radium-226 decay series……………………………..……………18 Table 2.2: Properties of radium-228 decay series…………………………………..………19 Table 2.3: NORM in Oil and Gas production………………………………………………19 Table 2.4: Radioactive decay characteristics of NORMs associated with oil and gas production (IAEA, 2003)……………………………………………………..23 Table 2.5: NORMs in two Australian offshore petroleum production facilities (Kvasnicka, 1998)……………………………………………………………………………27 Table 2.6: Concentration of NORM in Oil, Gas and By- Products (Jonkers et al., 1997)….29 Table 2.7: External Gamma Radiation Dose Rates observed in some Oil Production and Processing Facilities (IAEA, 2003)……………………………………………31 Table 2.8: Dose per unit intake for inhalation of radionuclides in particles of NORM Scale (IAEA, 2003)…………………………………………………………………...34 Table 2.9: Type of waste, technology, the companies involve and the treatment option available…………………………………………………………………...……45 Table 2.10: Summary of Produced Water Discharge Regulations (OSPAR, 2007; US EPA, 2003; C-NLOPB, 2008)………………………………………………………..87 Chapter three Table 3.1: Characteristics of the XtRa system used in this study…………………………..95 Table 3.2: Results in the energy-resolution calibration process of XtRa gamma detector…………………………………………………………..……………97 Table 3.3: Radionuclides used in liquid samples efficiency calibration…………………..99 Table 3.4: Fitting parameters and statistics from ln()-Ln(E) fitting process…………….101 Table 3.5: Experimental efficiency values ( (E), with uncertainty () in% for Petri dish geometry in IAEA_U ore (left) and IAEA Th ore (right)…………………….102 University of Ghana http://ugspace.ug.edu.gh xvi Table 3.6: The background count rate, counting efficiency, and MDA values for different α- particle measurement techniques……………………………………………..108 Table 3.7: Sources used for the energy calibration of the alpha spectrometers and channels found for the alpha peaks in one of the eight chambers of the Alpha Analyst system. The energies and their associated uncertainties have been extracted from (Chu et al., 1999)……………………………………………………………..112 Table 3.8: Experimental results determined for the counting efficiencies in the eight chambers at a source-detector distance of 5.5 mm…………………………..116 Table 3.9: MDA values in some alpha chambers………………………………………...118 Chapter four Table 4.1: Description of samples collected during each sampling campaign…………....128 Table 4.2: Activity to dose rate conversion factors (UNSCEAR, 2000 and 2008)……….147 Chapter five Table 5.1: Results of experimental efficiencies for the alpha chambers at a source to detector distance of 0.5cm…………………………………………………...160 Table 5.2: Geometries used for gamma measurements in different sample matrices……..160 Table 5.3: Analysis of reference material via gamma spectrometry………………………162 Table 5.4: Analysis of reference material via alpha spectrometry………………………...162 Table 5.5: Activity Concentrations of 238 U, 234 U, 230 Th and 232 Th, and 234 U/ 238 U activity ratio of the soil samples determined by alpha-particle spectrometry………………………………………………………………...….165 Table 5.6: Activity Concentrations of 226 Ra, 228 Ra, 228 Th, 40 K, 210 Pb, 234 Th and 137 Cs in the soils, determined by gamma-ray spectrometry…………………………………167 Figure 5.5: Graph showing the ratios of 226 Ra (by-)/ 238 U (by-) and 238 U (by-)/ 238 U (by-) for the soil samples……………………………………………………………166 Table 5.7: Average absorbed dose rate in air at 1 m above sampling points in the study areas and associated annual effective dose…………………………………………167 University of Ghana http://ugspace.ug.edu.gh xvii Table 5.8: External gamma absorbed dose rate and external annual effective dose calculated for all the soil sampling points analyzed in this work………………………….170 Table 5.9: Radium equivalent activity in Bq.kg -1 (Raeq), external (Hex) hazard index and internal (Hin) hazard index calculated at each soil sampling point…………...172 Table 5.10: Activity Concentration of 40 K, 238 U, 232 Th series radionuclides in beach Sediments samples by Gamma Spectrometry………………………………...173 Table 5.11: Radium equivalent activity in (Raeq), external (Hex) hazard index, internal (Hin) hazard index, External gamma absorbed dose rate and external annual effective dose calculated for beach Sediments samples………………………………..173 Table 5.12: Activity Concentrations of 238 U and 234 U and chemical yields in beach sediments samples analysed by alpha-particle spectrometry using the UTEVA and TBP radiochemical separation procedures……………………………….174 Table 13: Activity Concentrations of 232 Th and 230 Th and chemical yields in beach sediments samples analysed by alpha-particle spectrometry using the UTEVA and TBP radiochemical separation procedures……………………………………..174 Table 5.14: Activity Concentrations of 238 U, 234 U, 230 Th and 232 Th in beach Sediments samples determined by alpha-particle spectrometry using the TBP radiochemical separation procedure………………………………………………………….175 Table 5.15: Time, reagents and waste generated for TBP and UTEVA separation techniques…………………………………………………………………...176 Table 5.16: Gross -α and gross-β activities in the different waters samples analyzed in this work (W1-W4=underground, W5-W7= lagoon, W12 = river)……………….177 Table 5.17: 234 U, 238 U, 230 Th, 232 Th and 226 Ra activity concentrations as well as 234 U/ 238 U activity ratios determined in the water samples analysed…………………….178 Table 5.18: Activity Concentration of 40 K, 238 U, 232 Th series radionuclides and 228 Ra/ 226 Ra ratio in Produced water samples by Gamma Spectrometry………………….182 Table 5.19: Comparison of 226 Ra and 228 Ra in Produced Water from Ghanaian oilfields with others published in literature………………………………………………...184 Table 5.20: Activity Concentrations of 238 U, 234 U, 210 Po, 230 Th and 232 Th in the Produced water samples determined by alpha-particle spectrometry………………….185 Table 5.21: Average Gross -α and gross-β activities in Produced waters samples………..186 University of Ghana http://ugspace.ug.edu.gh xviii Table 5.22: Physical Parameters measured for Produced waters samples………………...187 Table 5.23: Anions and cations for Produced waters samples…………………………….188 Table 5.24: Trace metals in Produced waters samples determined via (ICP-QMS)………188 Table 5.25: Minimum detectable activity Concentration of 40 K, 238 U and 232 Th series radionuclides in crude oil by Gamma Spectrometry………………………..196 Table 5.26: 234 U, 238 U, 230 Th, 232 Th and 210 Po activity concentrations determined in the crude oil samples analysed………………………………………………………...196 Table 5.27: Activity Concentration of 40 K, 238 U, 232 Th series radionuclides in oily waste water and wash water samples by Gamma Spectrometry…………………...198 Table 5.28: Activity Concentrations of 238 U, 234 U, 210 Po, 230 Th and 232 Th in oily waste water and wash water samples determined by alpha-particle spectrometry……….199 Tables 5.29: Activity Concentration of 40 K, 238 U, 232 Th series radionuclides in Scales and sludge samples by Gamma Spectrometry…………………………………...200 Table 5.30: Activity Concentration of 40 K, 238 U, 232 Th series radionuclides in Ash, Mud and Mud block samples by Gamma Spectrometry………………………………201 Table 5.31: Comparison of 226 Ra and 228 Ra in Scale and Sludge from Ghanaian oilfields with others published in literature…………………………………………..205 Table 5.32: Activity Concentrations of 238 U, 235 U, 234 U, 210 Po, 230 Th and 232 Th in Scale, sludge, ash, mud and mud blocks samples determined by alpha-particle spectrometry…………………………………………………………………207 Table 5.33: Radium equivalent activity in (Raeq), external (Hex) hazard index, internal (Hin) hazard index, External gamma absorbed dose rate and external annual effective dose calculated for waste samples………………………………………….210 Table 5.34: Radon emanation fraction and Radon mass exhalation rate for waste samples………………………………………………………………………211 Table 5.35: Annual effective dose from inhalation of outdoor 222 Rn concentration for scale samples embedded in pipes and mud processing and block moulding facility…………………………………………………………………………214 Table 5.36: Annual effective dose from inhalation of indoor 222 Rn concentration for scale samples embedded in pipes…………………………………………………..214 University of Ghana http://ugspace.ug.edu.gh xix Table 5.37: Ambient effective dose rate measured externally and internally for scale samples embedded in pipes…………………………………………………..216 Table 5.38: Summary of annual equivalent doses, the estimated total effective dose and estimated risk components for the public exposure path ways considered………………………………………………………………………223 Table 5.39: Summary of annual equivalent doses, the estimated total effective dose and estimated risk components for the occupational exposure path ways considered………………………………………………………………………223 Table 5.40: Predicted 226 Ra and 228 Ra concentrations in fish and estimated associated cancer risk using human health risk assessment model…………………………….226 University of Ghana http://ugspace.ug.edu.gh xx LIST OF FIGURES Chapter two Figure 2.1: Uranium-238 decay series (IAEA, 2003)……………………….……………...21 Figure 2.2: Thorium-232 decay series (IAEA, 2003)………………………….…………...22 Figure 2.3: Precipitation of scales in production plant and equipment (IAEA, 2003)……...24 Figure 2.4: A Summary flow chart showing wastes and management processes currently being used by oil waste management companies in Ghana…………………..46 Figure 2.5: Ecological Risk Assessment Frameworks (US EPA, 1998; NRC-NAS, 1992; WERF, 1996; CCME, 1996)…………………………………………………...79 Figure 2.6: Human Health Risk Assessment Frameworks (US EPA, 1999a)……………...81 Figure 2.7: Horizontal flow profile for the Equation (2.0) dilution model…………………84 Chapter three Figure 3.1: Interaction mechanisms of X and gamma-rays with matter as a function of photon energy and atomic number (Knoll, 2000)…………………………….89 Figure 3.2: Compton scattered gamma photon……………………………………………..91 Figure 3.3: Pair production process………………………………………………………...91 Figure 3.4: Different constructions of Ge detectors; (A) plane, (B) coaxial, (C) ReGe, (D) XtRa and (E) well detector……………………………………………………94 Figure 3.5: Efficiency calibration curve for liquid samples in 1 L Marinelli geometry……94 Figure 3.5: Electronic system, detector and shielding from the gamma detector used in this work…………………………………………………………………………..94 Figure 3.6: Genie 2000 screenshot with singlets (red) and multiplets (blue) photopeaks groups …………………………………………………………………………95 Figure 3.7: Efficiency calibration curve for liquid samples in 1 L Marinelli geometry…..100 University of Ghana http://ugspace.ug.edu.gh xxi Figure 3.8: Comparison of background spectra measured in Rege detector (green dots) and Xtra detector (yellow area) after measuring the same time (254000 s) in both systems………………………………………………………………………103 Figure 3.9: List of the peaks found in the background of the Rege detector (left) and Xtra (right) detector……………………………………………………………...103 Figure 3.10: MDA in natural gamma emissions within two gamma systems available in the laboratory of University of Seville…………………………………………105 Figure 3.11: Simulation of the range reached by alpha particles of different energies in air (T=20ºC, P=760 Torr, relative humidity 50%) performed with the code SRIM 2013…………………………………………………………………………107 Figure 3.12: CANBERRA’s A- series PIPS detectors…………………………………...111 Figure 3.13: Eight (8) - chamber Alpha analyst system (Canberra)………………………111 Figure 3.14: Spectrum obtained in the energy-channel calibration with peaks used marked in red and green showing the alpha-peaks corresponding to the different U isotopes..…………………………………………………………………...113 Figure 3.15: Experimental variation of the counting efficiency with the distance source- detector (Vioque, 2000)……………………………………………………..115 Chapter four Figure 4.1: Saltpond offshore production field……………………………………………120 Figure 4.2: Map showing the study area and the location of the sampling points (S =soil, W=water, SD =sediment)…………………………………………………….121 Figure 4.3: Ghana offshore activity map………………………………………………….125 Figure 4.4: Jubilee oilfield straddling the two oil concession blocks……………………..126 Figure 4.5: Summary of various analytical steps involved in Alpha Spectrometry used in this work……………………………………………………………………...….132 Figure 4.6: Radiochemical separation steps for UTEVA and TBP……………………….135 Figure 4.7: Human health risk assessment framework……………………………………152 Figure 4.8: Exposure Pathways for Human Uptake………………………………………153 University of Ghana http://ugspace.ug.edu.gh xxii Chapter five Figure 5.1: Energy calibration curve for alpha spectrometry system……………………..159 Figure 5.2: Efficiency calibration curve for 1L marinelli beaker geometry of HPGe detector using 4 th order polynomial curve fitting……………………………………...161 Figure 5.3: Energy calibration curve for gamma spectrometry system…………………...161 Figure 5.4: Average Radiochemical yield for samples determined via Alpha spectrometry.........................................................................................................................163 Figure 5.5: 235 U/ 238 U activity ratios determined in the soil samples……………………..166 Figure 5.6: Graph showing the ratios of 226 Ra (by-)/ 238 U (by-) and 238 U (by-)/ 238 U (by-) for the soil samples……………………………………………………………168 Figure 5.7: Ambient 222 Rn concentration measured at coastal communities along the coast of Saltpond oilfield using alpha guard…………………………………………..171 Figure 5.8: Comparison between the Gross- activities and the 234 U activity concentrations determined in all the water samples analyzed in this work…………………...180 Figure 5.9: Comparison of mean specific activity of radionuclides in propduced water for the two Ghanian oilfields with the Canadian Derived Release Limits- Diffuse NORM Sources……………………………………………………………….183 Figure 5.10: Correlation between 226 Ra with HCO3 - , SO4 2- , Cl - in produced water……189 Figure 5.11: Correlation between total Radium with HCO3 - , SO4 2- , Cl - in produced water…………………………………………………………………………190 Figure 5.12: Correlation between 226 Ra with TDS, conductivity, Na and Ca in produced water…………………………………………………………………………191 Figure 5.13: Correlation between total Radium with TDS, conductivity, Na and Ca in produced water………………………………………………………………191 Figure 5.14: Correlation between total Radium with NO3 - , PO4 3- , F - in produced water.............................................................................................................192 Figure 5.15: Correlation between F - with other physico- chemical parameters in produced water…………………………………………………………………………193 Figure 5.16: BEI image of particulate matter in produced water via SEM………………..194 University of Ghana http://ugspace.ug.edu.gh xxiii Figure 5.17: Elemental composition of particulate matter in produced water via SEM…..........................................................................................................195 Figure 5.18: Comparison of mean specific activity of radionuclides in waste samples with the Exemption levels………………………………………………………...203 Figure 5.19: Comparison of mean specific activities of radionuclides in waste samples ......................................................................................................................209 Figure 5.20: Comparison of the Normalized average values of 226 Ra concentration, Radon emanation fraction and Radon mass exhalation rate for waste samples…….212 Figure 5.21: Correlation between 226 Ra with Radon emanation fraction and Radon mass exhalation rate for waste samples………………………………………….213 Figure 5.22: Ambient 222 Rn concentration measured at storage and maintenance facility for pipes embedded with scales using alpha guard…………………………….214 Figure 5.23: Ambient 222 Rn concentration measured at oily based mud treatment and block moulding facility using Alpha Guard………………………………………215 Figure 5.24: Results of SEM analysis for particles of scale (spot 1) with (a) showing grain size and (b) elemental composition …………………………..……………..218 Figure 5.25: Results of SEM analysis for particles of scale (spot 2) with (a) showing grain size and (b) elemental composition …………………………………………219 Figure 5.26: Results of SEM analysis for particles of scale (spot 3) with (a) showing grain size and (b) elemental composition ………………………..………………..220 Figure 5.27: Results of SEM analysis for particles of scale (spot 4) with (a) showing grain size and (b) elemental composition ……………………….………………..220 Figure 5.28: Results of SEM analysis for particles of sludge with (a) showing grain size and (b) elemental composition ……………………………….…………………220 Figure 5.29: Results of SEM analysis for particles of mud block with (a) showing grain size and (b) elemental composition ………………………………………..……220 Figure 5.30: Results of SEM analysis for particles of oil based mud with (a) showing grain size and (b) elemental composition ………………………………………...221 Figure 5.31: Results of SEM analysis for particles of Ash (Spot1) with (a) showing grain size and (b) elemental composition …………………………………………221 University of Ghana http://ugspace.ug.edu.gh xxiv Figure 5.32: Results of SEM analysis for particles of Ash (Spot2) with (a) showing grain size and (b) elemental composition ……………………...………………….221 LIST OF PLATES Chapter two Plate 2.1: Monitoring the outside of plant and equipment using a dose rate meter (courtesy: National Radiological Protection Board, UK) ………………………………….32 Plate 2.2: Workers wearing personal protective equipment decontaminating a valve inside an on-site facility (courtesy: National Radiological Protection Board, UK)…….37 Plate 2.3: Barrier designating a controlled area to restrict access to NORM-contaminated equipment stored outside a decontamination facility (courtesy: National Radiological Protection Board, UK)…………………………………………....37 Plate 2.4: Tanker siphoning bilge water/sludge from a vessel……………………………...41 Plate 2.5: Oily waste water separator on a vessel…………………………………………..43 Plate 2.6: Lagoons of produced water and remediation of contaminated land after drying the lagoon (courtesy: Atomic Energy Commission of Syria). ……………………...60 Chapter four Plate 4.1: Oil based mud processing and blocks moulding facility (Zeal environmental Technologies Ltd) …………………..…………………..……………………..130 Plate 4.2: Oily waste water treatment plant (Zeal environmental Technologies Ltd)…….130 Plate 4.3: Dose rate measurement around well heads on the Saltpond oilfield platform….131 Plate 4.4: Dose rate measurement on the inner surface of scale contaminated pipe from Jubilee field…………………..…………………..…………………..…………131 Plate 4.5: Gamma spectrometry system with a p-type Extended Range Germanium coaxial detector…………………………………………………………………………137 University of Ghana http://ugspace.ug.edu.gh xxv ABSTRACT In this research work radiological hazards and risks to members of the public and workers from exposure to natural radioactivity as a result of crude oil production activities and waste generation from the Saltpond and Jubilee oilfields of Ghana, have been investigated via several exposure pathways using alpha spectrometry after radiochemical separation, non- destructive gamma spectrometry, Scanning Electron Microscope (SEM) and Inductively Coupled Plasma Quadrupole-Based Mass Spectrometry (ICP-QMS) and other complimentary analytical tools. Additionally, in this study a Human health risk assessment model for cancer risk associated with NORM (Naturally Occurring Radioactive Material) components in produced water was developed. Characterization and determination of specific activities of 234 U, 238 U, 210 Po, 230 Th, 232 Th, 226 Ra, 210 Pb, 234 Th, 228 Ra, 228 Th, 224 Ra, and 40 K for several environmental and NORM waste samples in different matrices have been established. The elements Al, Ba, Ca, Cl, Cu, Fe, K, Mg, Na, P, Pb S, Si, Sr, and Zn were identified and semi qualitatively quantified by Scanning Electron Microscope for NORM waste samples. The total annual effective dose of 0.35 mSv.y -1 obtained for all exposure pathways for the public in this study was below the International Commission on Radiological Protection (ICRP) recommended dose limit of 1 mSv.y -1 for members of the public, whilst the total annual effective dose of 80.86 mSv.y -1 obtained in this study for workers clearly exceeded the ICRP recommended dose limit for an occupationally exposed worker of 20 mSv.y -1 , averaged over 5years, but not exceeding 50 mSv.y -1 in any single year. The estimated total lifetime fatality cancer risk and the lifetime hereditary effect values were 1.3 x 10 -3 and 4.9 x 10 -5 for the public, and 23.2 x 10 -2 and 5.7 x 10 -3 for adult workers respectively. In University of Ghana http://ugspace.ug.edu.gh xxvi conclusion, radium concentrations obtained in this study for scale, sludge and produced water from the oilfields of Ghana are of radiological importance and hence, there may be the need to put in place some measures for future contamination concerns due to their bioavailability in the media and bioaccumulation characteristics. The results from this study will assist in decision-making for future set-up of appropriate national guidelines for the management of NORM waste from the emerging oil and gas industry in Ghana. University of Ghana http://ugspace.ug.edu.gh 1 CHAPTER ONE INTRODUCTION 1.1 Background It is well known that the presence of NORM (naturally occurring radioactive material) is acknowledged as a problem in several extractive industries worldwide, a paradigmatic example being the oil and gas industry (Hamlat et al., 2001), where NORMs represent a considerable waste issue. The international community has been considering disposal options for these NORM wastes in order to make negligible the public radiological impact(Matta et al., 2002). Radiation exposure from NORM generated by the oil and gas industry can occur from seven environmental pathways: radon inhalation, external gamma exposure, ground water ingestion, surface water ingestion, dust inhalation, food ingestion and skin beta exposure (Smith, 1992). Individuals at risk from exposure to NORM radiation from the oil industry include workers at equipment cleaning facilities, oilfield workers, workers at NORM disposal facilities, and the general public, particularly, in the coastal cummunities close to shallow water offshore oilfields and land disposal facilities. The general population may be at risk to NORM via radon inhalation; and ingestion of groundwater, surface water and food. Improper disposal of NORM contaminated waste (scales, sludges and drilling mud) generated by the oil and gas industry may lead to soil and water contamination and to higher indoor radon levels in nearby buildings (Smith, 1992; USEPA, 1993). Ingestion of food grown in contaminated soils or seafood harvested in areas University of Ghana http://ugspace.ug.edu.gh 2 contaminated by produced water outfalls may also result in radiation exposure increments. A recent risk assessment for radium discharged in produced waters indicated a potential risk of exposure for an individual who ingests large amounts of seafood harvested near a produced water discharge point over a lifetime (Smith, 1992). It is therefore, of prime importance to gather baseline radioactivity data for water sources and soil in communities along the coast of such oilfields to serve as reference data for the future . These data will be useful not only to evaluate the present radiological state of the coastal environment, but also for subsequent evaluations of the possible future environmental contamination due to activities of the extractive industry. The presence of naturally occurring radioactive materials (NORMs) in the earth’s crust is well known. The 238 U, 235 U and 232 Th series, as well as 40 K are particularly important as they contain a number of radionuclides that are encountered in oil and gas products, produced water and in all sludge and scale deposits in subsurface and/or surface production facilities. (IAEA, 2003). Generally, the variation in the 226 Ra activity concentrations in NORM wastes of different origins, can be attributed to the differences in the Ra/Ba ratio in formation waters, scale and/or sludge formation processes on the exterior surfaces of the casing material and the amount of 226 Ra in the subsurface (White and Rood, 2001). The Ra content depends on the amount of Ra present in subsurface formation, formation water chemistry, extraction and treatment processes and the age of the waste after production. In general, the solubility of radium in water increases with the increase of saline content and at both high and low pH values. Naturally occurring radioactive material scale is produced when Ra dissolved in the University of Ghana http://ugspace.ug.edu.gh 3 formation water is co-precipitated with Ba, Sr, or Ca as sulphates (White and Rood, 1999). These materials form insoluble hard deposits inside the production equipment (Smith et al., 1999), while NORM sludge results from precipitation of Ra, Ba, Sr and Ca sulphates or silicates and carbonates. In many oilfields, produced water is re-injected into the reservoirs to maintain pressure. Normally, the water injected in the wells has a different composition from the water already present in the reservoir (formation water). When the water/oil emulsion is carried to the surface during the pumping operation, precipitation of residues on the inner surfaces of piping can take place. This precipitation and the consequent scale formation is due to variations of sulphate and carbonate solubilities and is associated with pH and temperature variations, pressure changes and injection of incompatible waters (Smith et al., 1996). Produced water, which is extracted during oil and gas production, includes formation water, injected water, small volumes of condensed water, and any chemical added down the hole or during the oil/water separation process (USEPA, 1993). Produced water is the highest volume of waste generated in association with oil and gas production operations. Despite treatment before discharge to satisfy regulatory limitations on oil content, produced water contains a certain amount of naturally occurring radioactive materials (NORM) such as 226 Ra and 228 Ra. NORM are difficult to remove from produced water, which make the assessment of their effects on human health important to the oil and gas producing industries. University of Ghana http://ugspace.ug.edu.gh 4 Radium-226 ( 226 Ra) is the NORM material of major interest because it is an intermediate member of the Uranium- 238 series and mostly in higher concentrations. It is water soluble, and it is classified as water- borne pollutant. Radium is brought to the surface dissolved in the water that accompanies the hydrocarbons (produced water). Uranium and thorium, on the other hand, remain in the reservoir, as they will not be leached into passing fluids. Potassium, which is released slowly upon dissolution from the rock matrix, is also present in the water. The degree of accumulation of radioactive materials is always significant for ducts and equipment that carry produced water. For this reason, NORM concentrations are, in general, higher in scales and sludge formed in water- handling equipment (Smith et al., 1996). Radiation levels measured after the water separation stage are, consequently, negligible or much lower than those observed in other cases, where the water is still present in the mixture. Consequently, a high water production rate, such as is characteristic of older oil fields, results in increased NORM accumulation on tubing and equipment (Gazineu and Hazin, 2008). NORM in the oil and gas industry represents a considerable waste issue and the international community has been considering disposal options (Matta et al., 2002; Hamlat et al., 2001). Estimates suggest that up to 30 % of domestic oil and gas wells in the USA may produce some elevated NORM contaminates (Derald and Talmage, 2002). In 1998, serious attention was given to health impacts from the uncontrolled release of waste containing NORM, concentrated and accumulated in tubing and surface equipment in the form of scale and sludge (Hamlat et al., 2001; Al-Masri and Aba, 2005). University of Ghana http://ugspace.ug.edu.gh 5 Radiation protection considerations arise mainly from the removal of this scale and sludge during maintenance and decommissioning operations resulting in exposure to external gamma radiation and inhalation of dust, and from the subsequent disposal of such materials as waste. Individuals working close to heavily scaled pipes and vessels may also need to be subjected to radiation protection measures (IAEA, 2003; Hamlat et al., 2001). The focus on health concerns related to the enhanced naturally occurring radioactive material (NORM) associated with oil and gas production, primarily involves the generation and release of chemically inert radon ( 222 Rn), produced by the radioactive decay of radium ( 226 Ra), a member of the uranium decay series. The radiation risks associated with the handling, transport and disposal of the NORM wastes contaminated with 226 Ra, are primarily due to the inhalation of 222 Rn, and are dependent on the rate at which 222 Rn is transported to the atmosphere or on the diffusion and subsequent emission from the NORM waste matrix to the staff operators (El Afifi et al.,2004). Therefore, it is necessary to underpin the radiological characteristics of the NORM wastes released from oil and gas production. The NORM extractive industries are not being regulated for NORM in most non-developed countries. In Ghana, there are over 200 registered mining companies operating small, medium and large scale mining, but only radionuclide concentrations assessment resulting from industrial activities such as mining and mineral processing has been carried out in some few mines (Darko et al., 2010; and Faanu et al., 2013). In addition to the mainly gold mining companies, Ghana also recently (in 2010) became an oil producing country, producing oil in commercial quantities. Currently, there are two producing oilfields located in the country, the Jubilee Deepwater offshore field and Saltpond University of Ghana http://ugspace.ug.edu.gh 6 shallow water offshore field, with activities which could lead to contamination of the marine environment, coastal lands and water bodies. In this regard, a national programme to establish baseline radioactivity measurements in the environmental compartments which can be affected by extractive industries that have just started operations as well as for existing ones are vigorously being pursued by the Radiation Protection Institute of Ghana, with the purpose of gathering reference data. In Ghana, some work have been carried out to evaluate the risks associated with NORMs in the mining industry (Darko et al., 2005), and some few workers in the mining industry are quite aware of the potential problems associated with NORMs. However, no work has been carried out to assess the potential hazards associated with NORMs in the oil fields of Ghana. To this end, this research explores the occurrence of NORM and estimates the activity concentration of radionuclides and other parameters such as the radiation hazard indices, the radium equivalent activity, the radon emanation coefficient, the absorbed dose rate and effective dose of crude oil, petroleum wastes and environmental samples from the Ghanaian Oil fields and its coastal environs. In this regard, analytical procedures for alpha and gamma spectrometric techniques which are key analytical tools for the characterization and determination of the isotopic signatures of several environmental and NORM waste samples for different matrices was developed, as alongside, complimentary chemical analytical tools. Additionally, in this study a human health risk assessment model for cancer risk associated with NORM components in produced water may be developed. University of Ghana http://ugspace.ug.edu.gh 7 1.2 Statement of the Problem NORM are everywhere and humans are constantly exposed to it particularly in the Oil and Gas industry. The enhancement of these NORM poses a major challenge to public health and occupational protection concerns. NORM, therefore, requires control for purposes of radiological protection of the worker, the public or the environment when they are present in sufficient concentrations just as is the case in the oil and gas industry, hence, must be monitored regularly. Currently, data on the radioactivity levels in oil and gas at the Jubilee oilfields at the West Cape Three Points in Ghana as well as the Saltpond offshore fileld is unavailable. This is because there have not been any radiological survey of the facilities and the surrounding areas. This situation could be of great concern to occupational protection and public health as well as environmental radiation protection particularly, as the country has started drilling oil in commercial quantities about five years ago. Hence the need to carry out a detail study such as this to ascertain the levels of natural radionuclides and also to assess the risk to workers and members of the public is very necessary. It is significant to note that it is only through a comprehensive study of this nature that will ensure accurate data is gathered that will aid in realistic decisions on the controls to be enforced. Any remedial actions can then be justified based on the data from this study. A common problem in oil production is the accumulation of scale on the interior surfaces of oil pipes. The scales are mostly composed of barium sulphate, barium carbonate, and calcium carbonate. The scale material originates from the reservoir underground formations and the bed rocks, and is carried out by the oil to the surface. In some conditions, where University of Ghana http://ugspace.ug.edu.gh 8 water is present, radioactive radium can be washed out of the underground rocks and brought to the surface with oil and production fluids. Depending on the formation and age of the well, removal, storage and disposal of the scale can result in serious health and environmental risks if not handled properly, both for workers and the public. Produced water is the highest volume of waste generated in association with oil and gas production operations. Despite treatment prior to discharge to satisfy regulatory limitations which is mainly on oil content, produced water contains a certain amount of naturally occurring radioactive materials (NORM) such as 226 Ra and 228 Ra. NORMs are difficult to remove from produced water, which makes the assessment of their effects on human health important to the oil and gas producing industries. This work therefore assesses levels of potential radiological hazard associated with NORMS in crude oil and petroleum waste from the Saltpond and Jubilee Oil Fields of Ghana. 1.3 Research Objectives Naturally occurring radionuclides of the uranium-thorium series and potassium-40 are generated from extractive industries such as mining of U-Th and other minerals, oil and gas extraction and processing, etc. The U-Th series and K-40 from terrestrial origin are considered ubiquitous and inexhaustible natural elements of the earth’s crust. The progenies of the U-Th series are known to be carcinogenic when exposed in excess of certain levels, e.g. Rn-222, Po-214, Po-210, etc. The primary objective of this study is therefore to assess the effective doses for the risk associated with exposure to naturally occurring radioactive materials in the oil and gas industries in Ghana from modelling view point, and also to determine the regulatory limitations of produced water and NORM wastes discharged from the oil fields. University of Ghana http://ugspace.ug.edu.gh 9 The specific objectives of this research are to: i. identify the various radionuclides associated with NORMs in crude oil and petroleum waste from the Saltpond and Jubilee Oil Fields of Ghana ii. determine the radioactivity concentration of NORMs in crude oil and petroleum waste from the Saltpond and Jubilee oil fields. iii. provide an estimate of the radiation hazard indices, the radium equivalent activity, the radon emanation coefficient, radon mass exhalation rate and the absorbed dose rate in air for petroleum waste samples. iv. estimation of the occupational exposure of workers due to external radiation and inhalation. v. assess the current state of Radiological protection of workers, the public and the surrounding environment of the Saltpond and Jubilee oil fields. vi. develop Human health risk assessment model for cancer risk associated with NORM components in produced water. vii. analyze and evaluate different safe waste management options in relation to the NORM wastes generated by the Oil industry in Ghana. 1.4 Significance of the study This work is necessary since no studies have been carried out on radioactivity levels associated with NORMs in crude oil and petroleum waste from the Saltpond and Jubilee Oil Fields of Ghana. Records available so far indicate that no occupational radiological information exits associated with this activity in Ghana. University of Ghana http://ugspace.ug.edu.gh 10 This research has particularly been necessitated as Ghana has started drilling oil in commercial quantities from the Saltpond and Jubilee Oil Field. Hence findings from this work will help put in place appropriate control measures with respect to basic radiological protection, environmental control, and waste management systems associated with NORMs to be generated by the oil industry. In this regard, the occurrence of radiological hazards and consequences associated with NORM which may pose serious health implications to workers, the public and the environment, can be assessed and prevention and mitigation measures undertaken where appropriate. It will also provide a basis for further detailed assessment of radiation exposures from NORMs in the Oil and Gas industry in Ghana. The necessary awareness through this study will be created for management of these facilities so that workers are appropriately trained on basic radiation safety at work and the public radiation protective measures This research will also serve as a useful data for Regulatory Bodies, Oil Field Operators, Oil Exploration Companies, Oil Refineries and Service Companies in the Oil and Gas industry in Ghana. This study is also important to minimize, and in some cases eliminate future problems that are associated with NORMs in the oil and gas industry in Ghana. 1.5 Scope and Limitation The work is intended to cover measurement of the uranium series and their daughter products as well as radon at the Saltpond and Jubilee oilfields, oil and gas waste management treatment facility (Zeal Environmental Technologies) and coastal communities within Saltpond in the central and western regions of Ghana. Various experimental and University of Ghana http://ugspace.ug.edu.gh 11 theoretical methods and instrumentations have been applied. Previous studies carried out have focused on other areas in Ghana. 1.6 Structure of the Thesis This Thesis discusses the radiation exposure and risk associated with crude oil and petroleum waste from Saltpond and Jubilee oilfields in Ghana. The Thesis is made up of six chapters with introductory note, review of literature, analytical procedures of alpha and gamma spectrometry, materials and methods, discussions of results and concluding remarks with recommendations. Chapter 1 provides a general introduction to the thesis including, research objectives, problem statement, research justification and hypothesis. A brief background of the study under investigation have been presented. Chapter 2 presents a vivid report on the literature survey which reveals information and previous work done by other researchers in other countries. Radiation detection methods and analytical procedures to key analytical tools alpha and gamma spectrometry developed for measurements of radioactivity in this study are presented in chapter three. The approach and methods used in this study to collect data and information as well as mathematical models are presented in Chapter four. Chapter five discusses the results of the study in a clear and concise manner, and summary, conclusions and recommendations are provided in Chapter six. University of Ghana http://ugspace.ug.edu.gh 12 CHAPTER TWO LITERATURE REVIEW Overview This Chapeter reviews work done reported in a number of publications and discussions on some radiological aspects of NORMs with respect to occupational radiation protection, public health and environmental radiation protection and the need for this work. 2.1 NORM in the Oil and Gas Industry The first reports of NORM associated with mineral oil and natural gases appeared in 1904 (Mclennan, 1904). Later reports described the occurrence of 226 Ra in reservoir water from oil and gas fields (Kolb and Wojcik, 1985) and, in the 1970s and 1980s several observations prompted renewed interest (IAEA, 2003). The radiological aspects of these phenomena, the results of monitoring and analyses and the development of guidelines for radiation safety are now reported extensively (IAEA, 2003) and there are quite a number of published data. In Ghana, some significant work has been carried out to evaluate the risks associated with NORMs in the mining industry (Darko et al., 2005) and most workers in the mining industry are aware of the potential problems associated with NORMs. However, historical antecedents have revealed that no work has been carried out to assess the potential hazards associated with NORM in the oil and gas industry in Ghana and hence there is no published data. In the exploration and extraction processes of oil and gas, the natural radionuclides 238 U, 235 U and 232 Th, as well as the radium-radionuclides ( 223 Ra, 224 Ra, 226 Ra and 228 Ra) and University of Ghana http://ugspace.ug.edu.gh 13 210 Pb,.etc., are brought to the slurry surfaces and may contain levels of radioactivity above the surface background (El Afifi and Awwad, 2005). As these materials are handled, their radioactive constituents may be separated, resulting in NORM waste. The petroleum waste (scale or sludge) are produced by two mechanisms: either incorporation or precipitation onto the production equipment such as: pipelines, storage tank, pumps etc. The waste generated in oil and gas equipment is due to the precipitation of alkaline earth metals as sulfate, carbonates and/or silicates. Nuclear spectroscopic analysis showed that the main radionuclides present in NORM waste associated with petroleum industries are 238 U, 235 U and 232 Th series. The mineralogical analysis by X-ray techniques (XRF and XRD) indicate the incorporation and co-precipitation of these radionuclides with the alkaline earth metals (e.g. Mg, Ca, Sr, Ba) and some quantities of lead sulphate, carbonate and/or silicate (Shuller et al., 1995). The volume of NORM waste generated by the petroleum industry is quite impressive. The U.S. Environmental Protection Agency (USEPA) estimates that 25,000t of NORM- contaminated scale and 225,000 t of NORM-contaminated sludge are produced annually by the American petroleum industry (USEPA, 1993). In the European Union, the total production of natural gas and oil is 140 Mt and 0.23×10 12 m 3 , respectively, which generates an annual sludge production of 10,000 m 3 (Vandenhove, 2002). The dominating radionuclides present in scales and other precipitates are 226 Ra and 228 Ra, with typical concentrations ranging from 1 to 1000 kBq kg -1 , although concentrations as high as 15,000 kBq kg - 1 have been reported in literature (USEPA, 1993). Values for 228 Ra in scales and sludge are, in general, not much less than for 226 Ra. Besides, reported radium University of Ghana http://ugspace.ug.edu.gh 14 concentrations in sludge are normally lower than in scales (Vandenhove, 2002; Paschoa, 1998). This notwithstanding, there is quite an appreciable literature on NORMs in the oil and gas industry in many oil producing countries around the world. The following paragraphs is an overview of some works done in various oilfields, being discussed in detail some radiological aspects of NORM with respect to occupational radiation protection, public health and environmental protection. In a work done at Syrian oilfields, 152 scale samples collected from equipment were analyzed for their radioactivity content (Al-Masri and Aba, 2005). The average 226 Ra activity concentration in these samples was found to be 174 kBq kg -1 , while the highest concentration for this isotope was 1520 kBq kg _1 . For 228 Ra, on the other hand, the average and maximum values were 91 and 868 kBq kg _1 , respectively. A gradual increase in 226 Ra specific activity from downhole tubes to the equipment and tubing at the surface installations was also reported. In another study, carried out in New York State, scale and sludge samples collected from the oil industry showed activity concentrations as high as 7.4 kBq kg _1 for 226 Ra, 4.7 kBq kg _1 for 228 Ra and 4.2 kBq kg _1 for 40 K (NYSDEC, 1999). At the same time, values for sludge samples from the Red Sea Region were 18.0 kBq kg _1 for 226 Ra, 13.3 kBq kg _1 for 228 Ra and 1.3 kBq kg _1 for 40 K (Shawky et al., 2001). In Brazil, values of activity concentration for scales removed from an offshore oil producing facility ranged from 19.1 to 323.0 kBq kg _1 and 4.21 to 235 kBq kg _1 for 226 Ra and 228 Ra, respectively. The sludge collected from the same facility presented concentrations ranging University of Ghana http://ugspace.ug.edu.gh 15 from 0.36 to 367 kBq kg _1 for 226 Ra and from 0.25 to 343 kBq kg _1 for 228 Ra, respectively (Godoy and Crux, 2003). A recent study that measured the 222 Rn emanation fraction in NORM scale wastes associated with oil and gas production in Egypt found values ranging from 0.02 to 0.087 (Rood, 2001; El Afifi et at., 2004) . Due to the difference in the particle size, the amounts of 222 Rn emanating from the sludge waste are generally higher than that from the scale waste. The typical 222 Rn emanation fraction for sludge measured by others is 0.2 (Smith et al, 1996a). In the basic case, a 222 Rn emanation fraction of 0.04 was used. When the 222 Rn emanation fraction was doubled (0.08), the resultant equivalent dose rate increased from 74 to about 150µSv.y -1 , while a 222 Rn emanation fraction of 0.02 resulted in a lower equivalent dose rate of 37µSv.y -1 (El Afifi et al., 2004). 2.2 Origin of Petroleum There are currently two plausible scientific theories that explain the process of oil formation. The first step is the biotic or biogenic theory, which states that oil was formed hundreds of millions of years ago, following the extinction of dinosaurs (i.e. terrestrial reptiles of the Mesozoic era) and algae that inhabited the earth some 65-248 million years ago. The remaining organic matter was then buried under many layers of sediment, and was exposed to high levels of litho-spherical heat and pressure, which then transformed this preserved matter into hydrocarbons (black gold or oil). According to geologists, this process is thought to occur amid the earth‘s solid rock layers, at temperatures ranging from 80-350 degrees Celsius and pressures ranging from 0.8-2 kbar (Dyer and Graham, 2002; Dutkiewicz et al., University of Ghana http://ugspace.ug.edu.gh 16 2003). The oil then migrates and remain in porous stones (such as limestone or sandstone, which have a porosity of about 20%) until it is discovered. The second theory is known as the abiotic or abiogenic theory, which states that oil is not a fossil fuel, but that it was formed from inorganic materials deep within the earth’s crust. According to this theory , hydrogen and carbon molecules found in the earth ‘s mantle are subject to extremely high temperatures and pressures , causing them to form hydrocarbon molecules , which then migrate upward into oil reservoirs , through deep fracture networks in the earth crust . Supporters of the abiogenic theory claim that the millions of barrels per day (1 barrel =159L) could not possibly be supplied by the limited number of pre-historic animals (algae and dinosaurs) that existed (Dutkiewicz et al., 2003). 2.3 NORMs in the Petroleum Industry NORMs are present in components of both petroleum production facilities and natural gas production facilities. NORMs can be associated with the presence of crude oil, produced water and natural gas. Petroleum industry NORMs are mainly scale, sludge and sand (IAEA, 2003; APPEA, 2002). In gas plant components, where only natural gas and/or its fractions are present, NORM occur on internal walls in the form of thin films and/or coatings formed by the decay products of radon gas. Considering that some formation water is also present in natural gas, small quantities of NORM sludge can be present in gas plants as well. NORMs occurring in oil installations mainly contain 226 Ra and 228 Ra, the activity of which is usually in equilibrium with the activity of their decay products. Scales in pipes and vessels are the most common NORMs in the petroleum industry. Scales are solid minerals that precipitate from produced water which has high salinity and contains University of Ghana http://ugspace.ug.edu.gh 17 sulphates and/or carbonates plus calcium, barium and strontium. The most common scales consist of barium sulphate (BaSO4), strontium sulphate (SrSO4) or calcium carbonate (CaCO3). Scale-forming material may also precipitate on sand and sludge particles and debris of scale may be mixed with sludge and sand inside vessels. Scale formation is caused by a combination of the following events (IAEA, 2003; APPEA, 2002): Mixing of incompatible waters; pressure changes; temperature changes; impurities; additives; variation of flow rates; changes in water acidity; fluid expansion; gas evaporation; etc. The most important scale formation processes are mixing of incompatible waters and temperature changes. Under high temperature and pressure conditions in an oil reservoir, trace concentrations of barium, strontium, calcium and radium are leached out from reservoir sand and are present in a soluble form in the formation water. This water also contains sulphates, carbonates and other ions (APPEA, 2002). Events that may cause precipitation of scale particles have been mentioned earlier. When scale precipitates from a large volume of formation or produced water, radium is concentrated within a small amount of solid scale such that the radium concentration in scale exceeds the radium concentration in the formation or produced water by several orders of magnitude. As uranium and thorium radionuclides are substantially less soluble in the formation water than radium, NORM scale contains practically no uranium and or thorium. It can be concluded that NORMs in petroleum production facilities contain mainly 226 Ra, 228 Ra and their short- lived decay products (APPEA, 2002; E& P forum, 1987). The half-life of 226 Ra is 1,600 years and that of radium-228 is 5.8 years. Radon decay products are continuously generated in solid NORMs in petroleum production installations by the decay of radium. Therefore, University of Ghana http://ugspace.ug.edu.gh 18 scale, sludge and sand emit approximately the same amount of radiation during normal operation conditions as well as during shutdowns. As the concentration of radium and radium decay products in formation and/or produced water is usually low in comparison with scale and sludge, the water itself is not a source of external radiation exposures (APPEA, 2002; E& P forum, 1987). Nevertheless, radium in discharges of the produced waters (especially from onshore facilities) may need to be considered depending on the levels of radium and on environmental considerations. Both 226 Ra and 228 Ra decay series radionuclides are summarised in Tables 2.1 and 2.2. Radionuclides below 226 Ra and 228 Ra are generated by the radioactive decay of the original radionuclide of radium. The main forms of NORMs in petroleum and natural gas production installations are summarized in Table 2.3 Table 2.1: Properties of Radium-226 decay series (IAEA, 2003) Nuclide Atomic No. Half-life Radiation 𝑅𝑎226 88 1602y 𝛼, 𝛾 𝑅𝑛222 86 3.824d 𝛼 𝑃𝑜218 84 3.05m 𝛼 𝑃𝑏214 82 26.8m 𝛽, 𝛾 𝐵𝑖214 83 19.8m 𝛽, 𝛾 𝑃𝑜214 84 162ms 𝛼 𝑃𝑏210 82 22.3y 𝛽, 𝛾 𝐵𝑖210 83 5.012d 𝛽 𝑃𝑜210 84 138.4d 𝛼 𝑃𝑏206 82 Stable - University of Ghana http://ugspace.ug.edu.gh 19 Table 2.2: Properties of Radium-228 decay series (IAEA, 2003) Nuclide Atomic No. Half-life Radiation 𝑅𝑎228 88 5.75y 𝛽 𝐴𝑐228 89 6.13h 𝛽, 𝛾 𝑇ℎ228 90 1.913y 𝛼, 𝛾 𝑅𝑎224 88 3.64d 𝛼, 𝛾 𝑅𝑛220 86 55.3s 𝛼 𝑃𝑜216 84 0.15s 𝛼 𝑃𝑏212 82 10.64h 𝛽, 𝛾 𝐵𝑖212 83 60.6m 𝛼, 𝛽, 𝛾 𝑃𝑜212 84 0.305ms 𝛼 𝑇𝐼208 81 3.07m 𝛽, 𝛾 𝑃𝑏208 82 Stable - Table 2.3: NORM in Oil and Gas production (IAEA, 2003) Type Radionuclide Characteristics Occurrence Ra scales Ra-226,Ra-228,Ra-224 and their progeny Hard deposits of Ca,Sr,Ba sulphates and carbonates Wet parts of production installations, well completions Ra sludge Ra-226,Ra-228,Ra-224 and their progeny Sand,clay,paraffins, heavy metals Separators, skimmer tanks Pb deposits Po-210 and its progeny Stable lead deposits Wet parts of gas production installations, well completions Pb films Po-210 and its progeny Very thin films Oil and gas treatment and transport Po films Po-210 Very thin films Condensates treatment facilities Condensates Po-210 Unsupported Gas productions Natural gas Rn-222,Pb-210,Po-210 Noble gas plated on surfaces Consumers domain gas treatment and transport systems Produced water Ra-226,Ra-228,Ra-224 and / or Pb-210 More or less saline, large volumes in oil production Each production facility University of Ghana http://ugspace.ug.edu.gh 20 2.4. Radiological Characteristics of NORM The radionuclides identified in oil and gas streams belong to the decay chains of the naturally occurring primordial radionuclides 238 U and 232 Th. These parent radionuclides have very long half-lives and are ubiquitous in the earth’s crust with activity concentrations that depend on the type of rock. Radioactive decay of 238 U and 232 Th produces several series of daughter radioisotopes of different elements and of different physical characteristics with respect to their half-lives, modes of decay, and types and energies of emitted radiation (Table 2.4 and Figures 2.1 and 2.2) (IAEA, 2003). Analyses of NORM from many different oil and gas fields show that the solids found in the downhole and surface structures of oil and gas production facilities do not include 238 U and 232 Th (Jonkers et al., 1997). These elements are not mobilized from the reservoir rock that contains the oil, gas and formation water (Figures 2.1 and 2.2). The formation water contains Group II (Periodic Table) cations of calcium, strontium, barium and radium dissolved from the reservoir rock. As a consequence, formation water contains the radium isotopes 226 Ra from the 238 U series (Figure 2.1) and 228 Ra and 224 Ra from the 232 Th series (Figure 2.2). All three radium isotopes, but not their parents, thus appear in the water co-produced with the oil or gas. University of Ghana http://ugspace.ug.edu.gh 21 Figure 2.1 Uranium-238 decay series (IAEA, 2003) University of Ghana http://ugspace.ug.edu.gh 22 Figure 2.2 Thorium-232 decay series (IAEA, 2003) University of Ghana http://ugspace.ug.edu.gh 23 Table 2.4: Radioactive decay characteristics of NORMs associated with oil and gas production (IAEA, 2003) They are referred to as ‘unsupported’ because their long lived parents 238 U and 232 Th and also 228 Th remain in the reservoir. The 228 Th radionuclide sometimes detected in aged sludge and scale is likely to be present as a product of the decay of the mobilized 228 Ra. When the ions of the Group II elements, including radium, are present in the produced water, drops in pressure and temperature can lead to the solubility products of their mixed sulphates and carbonates being exceeded. This causes their precipitation as sulphate and carbonate scales on the inner walls of production tubulars (T), wellheads (W), valves (V), pumps (P), separators (S), water treatment vessels (H), gas treatment (G) and oil storage tanks (O) (Figure 2.3). Deposition occurs where turbulent flow, centripetal forces and nucleation sites provide the opportunities. Particles of clay or sand co-produced from the reservoir may also act as surfaces initiating scale deposition or may adsorb the cations. If seawater, used to enhance oil recovery, mixes with the formation water, it will increase the sulphate concentration of the produced water and enhance scale deposition. Mixing may occur in the formation if ‘breakthrough’ occurs, which will result in scale deposits in the well completion, or the waters may be combined from different producing wells and mixed in topside plant and equipment. The mixed stream of oil, gas and water also carries the noble Radionuclide Half-life Mode of decay Main decay product(s) Ra-226 1600a Alpha Rn-222( noble gas) Rn-222 3.8235d Alpha Short live progeny Pb-210 22.30a Beta Po-210( alpha emitter) Po-210 138.40d Alpha Pb-206( stable) Ra-228 5.75a Beta Th-228 Th-228 1.9116a Alpha Ra-224 Ra-224 3.66d Alpha Short live progeny University of Ghana http://ugspace.ug.edu.gh 24 gas 222 Rn that is generated in the reservoir rock through decay of 226 Ra (IAEA, 2003; Jonkers et al., 1997). Figure 2.3 Precipitation of scales in production plant and equipment (IAEA, 2003) This radioactive gas from the production zone travels with the gas–water stream and then follows, preferentially, the dry export gases (IAEA, 2003; Jonkers et al., 1997). Consequently, equipment from gas treatment and transport facilities may accumulate a very thin film of 210 Pb formed by the decay of short lived progeny of 222 Rn adhering to the inner surfaces of gas lines. These 210 Pb deposits are also encountered in liquefied natural gas processing plants. A quite different mechanism results in the mobilization, from the reservoir rock, of stable lead that contains relatively high concentrations of the radionuclide University of Ghana http://ugspace.ug.edu.gh 25 210 Pb. This mechanism, although not well understood (Jonkers et al., 1997) has been observed in a number of gas production fields and results in the deposition of thin, active lead films on the internal surfaces of production equipment and the appearance of stable lead and 210 Pb in sludge. Condensates, extracted as liquids from natural gas, may contain relatively high levels of 222 Rn and unsupported 210 Pb. In addition, 210 Po is observed at levels in excess of its grandparent 210 Pb, indicating direct emanation from the reservoir. 2.5 Occurrence of NORMS in Scale, Sludge and Sand The main types of NORMs in oil and gas installations are scale, sludge, sand and thin film deposits of radon decay products. Their occurrence depends on certain reservoir parameters and can be triggered by water flooding a reservoir (APPEA, 2002). 2.5.1 Occurrence of NORM scale Provided the formation water contains barium, strontium or calcium as well as sulphates and carbonates, scale can build up in well tubing where a considerable pressure and temperature drop occurs between the reservoir and the crude oil in the well tubing. Scale formation in well tubing can be predicted on the basis of concentrations of cations and anions in the formation water, reservoir temperature and pressure, temperature and pressure in the well tubing etc. (APPEA, 2002; Odo and Tomson, 1994). It is important to understand that if scale forms, in the majority of cases it contains radium and its radium specific activity depends on levels of radium and thorium in reservoir sands. Generally, the specific radium activity in calcium carbonate scales is lower than the specific activity of barium sulphate scales (APPEA, 2002). The water chemistry of several wells of a reservoir can be University of Ghana http://ugspace.ug.edu.gh 26 substantially different (some wells may contain elevated concentrations of barium and strontium and low concentrations of sulphates whilst the formation water of other wells may be deficient in barium and strontium but contain elevated concentrations of sulphates). This happens when a part of the reservoir is flooded by sea water, which has an elevated concentration of sulphates, to increase the production pressure. Under such circumstances an intensive scale formation occurs when the two types of incompatible water mix in a production header. Provided scale is found in the upstream sections of an oil producing facility (well tubing, production header, etc.), it is likely that NORMs would be present in the remaining parts of the facility as well. Nevertheless, their production rates differ depending on the type of the primary scale formation process and several other factors (APPEA, 2002). Scales are brittle minerals and thus scale build up in pipes and vessels frequently cracks due to temperature contractions of pipes, movement of flexible hoses, etc. Scale debris are removed from pipe surfaces and are carried with crude oil and produced water. Coarse scale debris ends up in separators and sand traps, while fines end up in slops tanks. The most ‘difficult’ type of NORM from a waste management perspective is the practically insoluble barium (radium) sulphate scale that is formed in pipes and vessels. Barium sulphate scales are usually more radioactive than carbonate scales. Scale build-up in pipes and vessels may also cause production complications (clogging pipes and valves and undesirable accumulation of large quantities of NORM solids in vessels and separators) (Kvasnicka, 1998). The specific activity of radium in NORMs from two Australian offshore petroleum production facilities has been summarised in Table 2.5 (Kvasnicka, 1992 and 1997). Because the first facility had only NORMs based on barium sulphate whilst the University of Ghana http://ugspace.ug.edu.gh 27 second one had a NORM mixture of barium sulphate and calcium carbonate (Kvasnicka, 1992 and 1997).The oil industry international exploration and production forum (E&P Forum, 1987) reported a wide range of radium activities in scale: northern part of the North Sea up to 3,700 Bq/g; mid North Sea up to 15,200 Bq/g; northern Europe up to 3,400 Bq/g; and southern Europe 0.37 Bq/g. In the USA, scale was reported to have a specific radium activity in excess of 100 Bq/g (APPEA, 2002). Scale build up in components of gas plants is usually minor. Table 2.5: NORMs in two Australian offshore petroleum production facilities (Kvasnicka, 1998) NORM Type Specific activities(Bq / g) Radium-226 Radium-228 Scale 250* 300* 150** 240** 21** 48** Sludge 25* 30* Sand 8.9* 9.6* Note: * The first facility had only barium sulphate based scale and NORMs. ** The second facility had a mixture of barium sulphate scale and calcium carbonate scale 2.5.2 Occurrence of NORM sand Small quantities of sand are carried in crude oil and coarse sand is trapped in sand traps located upstream from separators and in separators as well. In oil production facilities with scale build up, sand is highly contaminated with scale debris and radium content in this waste stream needs to be taken into account when disposing of such sands. In facilities with high concentrations of calcium and carbonates, a rapid precipitation of coarse calcium University of Ghana http://ugspace.ug.edu.gh 28 carbonate particles may occur in those facility components with a positive temperature gradient. Such crystal precipitate usually accumulates in separators and a fine fraction increases the sludge production rate. There is usually only a minor waste sand stream in natural gas plants (APPEA, 2002; IAEA, 2003). 2.5.3 Occurrence of NORM sludge Sludge usually contains fine sand particles, corrosion particles, flakes of paint, bacteria growth and fines derived from scale. Sludge is usually accumulated in separator vessels and slops tanks of oil production facilities. The specific activity of radium in NORMs (including sludge) from two Australian offshore petroleum production facilities has been summarised in Table 2.5. In gas plants, sludge containing radium and solids accumulated in separators containing 210 Pb or 210 Po must be periodically removed (APPEA, 2002; IAEA, 2003). 2.5.4 A summary of radionuclide concentrations of NORM A large amount of data has been collected over the years on the radionuclide concentrations in NORM, although relatively few reports have been published (APPEA, 2002; IAEA, 2003). It would appear that the concentrations of 226 Ra, 228 Ra and 224 Ra in scales and sludge range from less than 0.1 Bq/g up to 15 000 Bq/g (APPEA, 2002) (Table 2.6). Generally, the activity concentrations of radium isotopes are lower in sludge than in scales. The opposite applies to 210 Pb, which usually has a relatively low concentration in hard scales but which may reach a concentration of more than 1000 Bq/g in lead deposits and sludge. Although thorium isotopes are not mobilized from the reservoir, the decay product 228 Th starts to grow in from 228 Ra after deposition of the latter. As a result, when scales containing 228 Ra grow University of Ghana http://ugspace.ug.edu.gh 29 older, the concentration of 228 Th increases to about 150% of the concentration of 228 Ra still present (IAEA, 2003). Table 2.6: Concentration of NORM in Oil, Gas and By- Products (Jonkers et al., 1997) Radionuclides Crude oil (Bq / g) Natural gas (Bq / m 3 ) Produced water (Bq / L) Hard scale (Bq / g) Sludge (Bq / g) U-238 0.0000001-0.01 0.0003-0.1 0.001-0.5 0.005-0.01 Ra-226 0.0001-0.04 0.002-1200 0.1-15000 0.05-800 Po-210 0-0.01 0.002-0.08 0.02-1.5 0.004-160 Pb-210 0.005-0.02 0.05-190 0.02-75 0.1-1300 Rn-222 5-200000 Th-232 0.00003-0.002 0.0003-0.001 0.001-0.002 0.002-0.01 Ra-228 0.3-180 0.05-2800 0.5-50 Ra-224 0.5-40 2.6 Radiation Protection Aspects of NORM In the absence of suitable radiation protection measures, NORM in the oil and gas industry could cause external exposure during production owing to accumulations of gamma emitting radionuclides and internal exposures of workers and other persons, particularly during maintenance, the transport of waste and contaminated equipment, the decontamination of equipment, and the processing and disposal of waste (IAEA, 2003). Exposures of a similar nature may also arise during the decommissioning of oil and gas production facilities and their associated waste management facilities. University of Ghana http://ugspace.ug.edu.gh 30 2.6.1 Radiation exposure pathway Radiation exposure from oil and gas NORM can occur from seven environmental pathways: radon inhalation, external gamma exposure , ground water ingestion, surface water ingestion, dust inhalation, food ingestion and skin beta exposure (Smith, 1992). Populations at risk from exposure to NORM radiation include workers at equipment cleaning facilities, oilfield workers, workers at NORM disposal facilities, and the general public. Workers at equipment cleaning facilities are considered to be at the greatest risk of exposure to NORM. Exposure pathways of concern are external gamma exposure, dust inhalation, and skin beta exposure. External exposure occurs when concentration of NORM inside equipment is high enough that gamma rays penetrate the equipment walls, and NORM contaminated scale and sludge are removed from the equipment, thereby eliminating the shielding factor provided by the equipmement walls (Smith, 1992). Dust inhalation is possible when dry cleaning processes are used without adequate controls. Direct contact with contaminated scale and sludge can result in skin beta exposures. Workers at NORM disposal facilities are at risk of exposure via radon inhalation, external gamma exposure, dust inhalation, and skin beta exposure pathways. Risk is increased at facilities where NORM contaminated waste and equipment are buried without control features (i.e., not at licensed NORM or low level waste facilities) and at smelter facilities where NORM detection systems have not been installed. The general population may be at risk to NORM via radon inhalation, groundwater ingestion, surface water ingestion, and food ingestion. Improper disposal of NORM contaminated scale and sludge may lead to soil and water contamination and to higher indoor radon levels in nearby buildings (Smith, 1992; USEPA, 1993). Ingestion of food grown in contaminated soils or seafood harvested in areas University of Ghana