Helium: Exploration Methodology for a Strategic Resource Diveena Danabalan A Thesis presented for the degree of Doctor of Philosophy Department of Earth Sciences Durham University United Kingdom June 2017 Contents List of Figures 5 List of Tables 7 Abstract 9 Declaration 10 Copyright Statement 10 About the author 10 Acknowledgements 11 Chapter One: Introduction 13 1.1. Helium Exploration 14 1.1.1 Helium in the modern world 14 1.1.2. Types of helium reservoir 18 1.1.2.1. CO2-rich fields 19 1.1.2.2. CH4-rich fields 20 1.1.2.3. N2-rich fields 21 1.1.3. Introducing helium as a noble gas 22 1.1.3.1. Sources of helium 23 1.2. The other noble gases 24 1.2.1. Neon 24 1.2.2. Argon 25 1.2.3. Krypton and Xenon 26 1.3. The noble gases as geochemical tracers in natural gas systems 26 1.3.1. Crustal contributions to natural gas systems 28 1.3.2. Mantle contributions to natural gas systems 28 1.3.3. Groundwater contributions to natural gas systems 29 1.4. Literature review of the helium system 30 1.4.1. Generation and accumulation 30 1.4.2. Primary migration 32 1.4.3. Helium and associated carrier gases 33 1.4.4. Secondary migration 34 1.4.5. Entrapment and escape 36 1.5. Objectives and thesis outline 38 Chapter Two: Methods 40 2.1. Introduction 41 2.2. Sampling in the field 41 2.3. Analytical equipment 44 2.3.1. The Oxford Purification Line 44 1 2.4. Mass spectrometers 47 2.4.1. Helix SFT™ 47 2.4.2. Argus VI™ 48 2.5. Blanks 49 2.6. Air standards 50 2.7. Sample loading and preparation 53 2.7.1. Helium measurements 55 2.7.2. Neon measurements 57 2.7.3. Argon, krypton and xenon measurements 57 2.8. Data reduction and error propagation 58 2.8.1. Data reduction 58 2.8.1.1. Concentration calculations 59 2.8.2. Error propagation 62 2.8.2.1. Worked error example for isotopic ratios 63 2.8.2.2. Propagating errors for isotopic abundance 65 Chapter Three: Economic Helium Reservoirs in the Mid-Continent United States 66 3.1. Introduction 67 3.2. The geology of South-West Kansas and the Hugoton-Panhandle system 70 3.3. Sample collection and analytical techniques 83 3.4. Results 85 3.4.1. Noble gases 93 3.4.1.1. Helium 93 3.4.1.2. Neon 94 3.4.1.3. Argon 96 3.4.1.4. Krypton and Xenon 97 3.4.1.5. Crust-derived noble gases 98 3.4.1.6. Groundwater-derived noble gases 99 3.4.1.7. The interaction between 20Ne and crust-derived isotopes 102 3.4.2. Other major gases 104 3.4.2.1. Methane 104 3.4.2.2. Nitrogen 104 3.4.3. Nitrogen and the noble gases 109 3.5. Discussion 113 3.5.1. Helium mass balance 113 3.5.1.1. In situ helium production 115 4 3.5.1.2. External sources of He production 117 3.5.2. Thermal controls on the release of radiogenic isotopes 122 3.5.3. Groundwater, N2, CH4 and the noble gases 129 4 3.5.4. The interaction between He, crustal N2, organic N2 and CH4 143 3.6. Summary 151 4 Chapter Four: The Geochemical Characteristics of the He-N2 source in Helium Systems 154 4.1. Introduction 155 4 4.2. Geological context of the N2- He rich wells 156 2 4.2.1. Harley Dome, Grand Co., Utah, USA 158 4.2.2. Rudyard field, Hill Co., Montana, USA 161 4.2.3. International Helium Wood Mountain, Saskatchewan, Canada 165 4.3. Sample collection and analytical techniques 166 4.4. Results 168 4.4.1. Noble gases 171 4.4.1.1. Helium 171 4.4.1.2. Neon 172 4.4.1.3. Argon 174 4.4.1.4. Krypton and xenon 174 4.4.1.5. Crust-derived noble gases 175 4.4.1.6. Relationships between 20Ne and the crust-derived 177 isotopes 4.4.2. Other major gases 180 4.4.2.1. Methane, ethane, propane and CO2 180 4.4.2.2. Nitrogen 181 4.4.3. Relationships between N2 and the crust-derived noble gases 182 4.5. Discussion 183 4 4.5.1. The N2 isotopic endmember for He 185 20 4 4.5.2. Groundwater ( Ne) relationships with He and N2 189 4.5.3. Characterising the groundwater component of 4He-rich fields 192 4.6. Summary 196 Chapter Five: High Helium Systems in Tanzania 198 5.1. Introduction 199 5.2. The geological history of Tanzania 201 5.3. Prior precedent for 4He release in Tanzania 205 5.3.1. Determining the 4He potential of Tanzania 208 5.4. The geology of the study locations 212 5.4.1. Study area 1: The North Tanzanian Divergence 212 5.4.1.1. Eyasi 213 5.4.1.2. Balangida 213 5.4.1.3. Gonga 214 5.4.1.4. Mponde 215 5.4.2. Study area 2: The Mbeya Triple Junction 215 5.5. New results from Tanzania 217 5.5.1. Helium 220 5.5.2. Neon 220 5.5.3. Argon 221 5.6. Discussion 222 5.6.1. The uses of the radiogenic noble gases as a means of locating 4He-rich areas 222 5.6.2. Compiling a ‘play fairway’ assessment of Tanzania 226 5.7. Summary 229 3 Chapter Six: The Principles of Helium Exploration 231 6.1. The Helium System 232 6.1.1. Generation 233 6.1.2. Maturation 234 6.1.3. Primary migration 236 6.1.4. Secondary migration 241 6.1.5. Accumulation in reservoirs 243 6.1.6. Trap efficiency, leakage and destruction 243 6.2. Summary 245 Chapter Seven: Conclusions and Further Work 247 7.1. Conclusions 248 7.1.1. Expanding the current helium exploration methodology 252 7.2. Further work 252 References 255 Appendices Appendix A: Background geology of the Mid-Continent fields 281 Appendix B: Full dataset from thesis 286 Final word count: 69,116 (Word count excluding appendices and references = 55,488) 4 List of Figures Chapter One: Introduction Figure 1.1. The uses of helium in the USA as of 2017 15 Figure 1.2. Helium concentrations and reserve volumes for different types of helium-rich field 19 Figure 1.3. The three sources of noble gases in shallow gas reservoirs 27 Chapter Two: Methods Figure 2.1. Field sampling apparatus setup 43 Figure 2.2. Schematic of the Oxford Purification Line 47 Figure 2.3. Variance in signal for the overnight standards 52 Figure 2.4. Raw values for worked example of error propagation 63 Chapter Three: Economic Helium Reservoirs in the Mid-Continent United States Figure 3.1. Map of helium-rich occurrances in the USA 68 Figure 3.2. Sample areas map and cross section 72 Figure 3.3. Structural development of the geological features associated with the study areas over time 75 Figure 3.4. General stratigraphic section of Kansas 77 Figure 3.5. Oil pathways out of the Anadarko and Ouachita Basins 78 Figure 3.6. BTU map of the Kansas study areas 80 Figure 3.7. Three neon isotope graph 96 Figure 3.8. Relationships between 20Ne and the radiogenically produced noble gases 103 15 Figure 3.9. Map and cross section of δ NN2 values for the study areas 106 40 4 40 36 40 Figure 3.10. Plots of N2/ Ar and He/ Ar vs Ar/ Ar 108 4 Figure 3.11. Graph of N2 vs He trends 109 4 15 Figure 3.12. Plot of He/N2 vs. δ NN2 110 Figure 3.13. The relationship between radiogenic 4He and 40Ar* normalised to nucleogenic 21Ne* 125 Figure 3.14. Plots showing groundwater-derived 20Ne vs the radiogenic isotopes (4He, 21Ne* and 40Ar*) where both variables are normalised to N2 131 Figure 3.15. Plots showing groundwater-derived 20Ne vs the radiogenic isotopes (4He, 21Ne* and 40Ar*) where both variables are normalised to CH4 134 4 Chapter Four: The Geochemical Characteristics of the He-N2 source in Helium Systems 4 Figure 4.1. Locations of all N2- He rich wells relative to regional structures 157 Figure 4.2. Location of the Harley Dome well relative to other geological structures 158 5 Figure 4.3. Generalised cross section from the Paradox Basin to the Uncompahgre Plateau 159 Figure 4.4. Locations of the Weil #1 well and International Helium Wood Mtn well relative to local and regional geological structures and cratonic provinces 162 Figure 4.5. Three neon isotope graph 173 Figure 4.6. Plot showing the relationship between radiogenic 4He and 40Ar* normalised to nucleogenic 21Ne* 176 Figure 4.7. Plots showing relationships between radiogenically and nucleogenically derived components and groundwater-derived 20Ne 179 4 Figure 4.8. Plot of N2 concentration vs He concentration 183 4 15 Figure 4.9. Plot of He/N2 vs. δ NN2 187 Figure 4.10. Plot showing groundwater-derived 20Ne vs radiogenic-sourced 4 He where both variables are normalised to N2 191 Figure 4.11. Plots showing groundwater-derived 20Ne vs radiogenic 4 He where both variables are normalised to N2 for thesis dataset and data from Gilfillan (2006) 195 Chapter Five: High Helium Systems in Tanzania Figure 5.1. The position of the study region in relation to the rest of Africa 200 Figure 5.2.