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Junhong Chen and Chris Boreham

Isotopic Analysis of Compounds in Low Concentration in Australian Natural Gases Using CF-GC-IRMS Systems. Junhong Chen and Chris Boreham. Isotope and Organic Geochemistry Team at GA. Aim.

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Junhong Chen and Chris Boreham

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  1. Isotopic Analysis of Compounds in Low Concentration in Australian Natural Gases Using CF-GC-IRMS Systems Junhong Chen and Chris Boreham

  2. Isotope and Organic Geochemistry Team at GA Isotopic Analysis of Compounds in Low Concentration in Australian Natural Gases Using a CF-GC-IRMS System

  3. Aim Explore efficient analytical methods of natural gases isotopic composition, especially for those in low concentrations; Provide new isotope data sets (neo-C5, N2) for natural gas evolution assessments Isotopic Analysis of Compounds in Low Concentration in Australian Natural Gases Using a CF-GC-IRMS System

  4. Instruments • 13C/12C, 15N/14N analysis: • Thermo Finnigan-MAT 252 (253) GC-C-IRMS System with ConFlo III (IV) interface Isotopic Analysis of Compounds in Low Concentration in Australian Natural Gases Using a CF-GC-IRMS System

  5. Instruments • D/H: • Thermo Finnigan Delta Plus XL GC-TC-IRMS System (TC – High Temperature Conversion) Isotopic Analysis of Compounds in Low Concentration in Australian Natural Gases Using a CF-GC-IRMS System

  6. Analytical Conditions (δ13C and δD) • GC conditions: • GC columns: • Varian, coating: PoraPlot Q; 25m x 0.32mm (ID), 0.25m. • Oven temperature: • Isothermal at 30oC for methane, CO2 and ethane; Increased at 20°C/min to 230°C for C3-C5. • Injector temperature:150ºC • Split Ratio:200:1 to 25:1. • Furnace temperatures for δ13C: • Oxidation:900ºC • Reduction:630ºC • Furnace temperature for δD: 1400ºC Isotopic Analysis of Compounds in Low Concentration in Australian Natural Gases Using a CF-GC-IRMS System

  7. Injection Requirements (δ13C) • Peak intensity required for reliable results: • Trace m/z 44: Min 0.3 V; Max 7V (MAT 252) • 50V (MAT 253) • Equivalent to: 0.0064 – 0.15µg (MAT 253: 1.05µg) • Split ratio: 200:1 to 25:1 • Injection volume: 30µl – 20 ml • Cryo-trapping: only applied for C1-C3 and CO2 when large volumes (>200µl)are needed Isotopic Analysis of Compounds in Low Concentration in Australian Natural Gases Using a CF-GC-IRMS System

  8. Analysis for C1, CO2 and C2 45/44 Compositions (mol%) : C1: 85.67 CO2: 2.03 C2: 6.47 30°C;25:1 150l, 2 injections 30°C; 200:1 40l, 3 injections 44 Standard C1 C2 C2 C1 BF C1 Reference BF C1 CO2 CO2 C2 CO2 Isotopic Analysis of Compounds in Low Concentration in Australian Natural Gases Using a CF-GC-IRMS System

  9. C2+: manual or programmed? • Manual: Use timer to remind operator to switch between SF and BF and start GC to increase oven temperature after C2 elutes. • Programmed: Inject sample at injection time and ‘walk away’: the program automatically switches between SF and BF and start to increase oven temperature at the right time. Isotopic Analysis of Compounds in Low Concentration in Australian Natural Gases Using a CF-GC-IRMS System

  10. 230°C GC oven temperature programming 45/44 20°C/min 30°C 44 C2 C3 Split ratio 25:1; inject 200μl BF:170-360s n-C4 i-C4 i-C5 n-C5 200 1000 400 600 800 Time (s) Injection time Isotopic Analysis of Compounds in Low Concentration in Australian Natural Gases Using a CF-GC-IRMS System

  11. 45/44 44 C2 C3 n-C4 i-C4 i-C5 n-C5 200 1000 400 600 800 Isotopic Analysis of Compounds in Low Concentration in Australian Natural Gases Using a CF-GC-IRMS System

  12. C4 and C5 • No need of cryo-trapping. • C4 and C5 will ‘focus’ at the front end of GC column until oven temperature increased. • Neo-C5: • Extremely low concentration in natural samples. • Backflushing is needed! • Routinely analysed at GA.

  13. GC-IRMS m/z 44 trace of C4 and C5 hydrocarbons Split ratio: 25:1 Injection volume: 200µl n-C4 i-C4 neo-C5 n-C5 i-C5 Isotopic Analysis of Compounds in Low Concentration in Australian Natural Gases Using a CF-GC-IRMS System

  14. GC-IRMS m/z 44 trace of neo-C5 Split ratio: 25:1 Inject volume: 8ml neo-C5 BF BF i-C4, n-C4, i-C5 and n-C5 are back flushed (BF) Isotopic Analysis of Compounds in Low Concentration in Australian Natural Gases Using a CF-GC-IRMS System

  15. neo-Pentane and biodegradation n-pentane neo-pentane iso-pentane Biodegradation Difficulty Isotopic Analysis of Compounds in Low Concentration in Australian Natural Gases Using a CF-GC-IRMS System

  16. Neo-C5: application to gas correlation C1 C2 C3 i-C4 n-C4 neo-C5 i-C5 n-C5 -10 -20 d13C (o/oo) -30 Barrow Island Z56M non-biodegraded Barrow Island F 82M - moderately biodegraded -40 Tubridgi-18 - severely biodegraded -50 Isotopic Analysis of Compounds in Low Concentration in Australian Natural Gases Using a CF-GC-IRMS System

  17. Neo-C5: application to gas correlation C1 C2 C3 i-C4 n-C4 neo-C5 i-C5 n-C5 100 50 0 d2H (o/oo) -50 -100 -150 Barrow Island Z56M non-biodegraded Barrow Island F 82M - moderately biodegraded Tubridgi-18 - severely biodegraded -200 Isotopic Analysis of Compounds in Low Concentration in Australian Natural Gases Using a CF-GC-IRMS System

  18. Australian sedimentary basins with natural gas deposits Isotopic Analysis of Compounds in Low Concentration in Australian Natural Gases Using a CF-GC-IRMS System

  19. Use gas carbon isotope to correlate source rocks 13C kerogen = 13C i-butane (Boreham et al. APPEA) Isotopic Analysis of Compounds in Low Concentration in Australian Natural Gases Using a CF-GC-IRMS System

  20. -50 -40 -30 -20 -10 0 -20 -25 -30 C, per mil) -35 13 (delta -40 5 -C Gippsland neo Otway -45 Bonaparte Browse -50 Carnarvon Perth Amadeus -55 13 i -C (delta C, per mil) 4 13C neo-pentane vsi-butane 13C kerogen = 13C neo-C5 + 2‰ Terrestrial biodegradation 13Cneo-C5 (‰) Marine 13Ci-C4 (‰) Isotopic Analysis of Compounds in Low Concentration in Australian Natural Gases Using a CF-GC-IRMS System

  21. N2: A preliminary study BOC UHP N2 as reference (15N = -1.5‰) Oxidisation furnace temperature reduced from 900C to 600C; Reduction furnace still at 630C The N2 of air (15N = 0 ‰) was used as the standard GC oven temperature: 30C Split ratio: 200:1 to 25:1 Injection volumes: variable Isotopic Analysis of Compounds in Low Concentration in Australian Natural Gases Using a CF-GC-IRMS System

  22. GC-IRMS traces of N2 29/28 Gas 3: 15NAIR = -0.37‰ stdev = 0.10 Gas 2: 15N = 0.54‰ stdev = 0.12 Gas 1: 15N = 0.45‰ stdev = 0.11 28, 29 Air N2: 15N = 0.29‰ stdev = 0.09 Isotopic Analysis of Compounds in Low Concentration in Australian Natural Gases Using a CF-GC-IRMS System

  23. N2 Results: 15N N2(‰) Air biodegradation 13C i-C4 (‰) Terrestrial Marine Isotopic Analysis of Compounds in Low Concentration in Australian Natural Gases Using a CF-GC-IRMS System

  24. N2 Results: Air from ‘air’ in meteoric water N2 mol % Terrestrial Marine 15N N2(‰) Isotopic Analysis of Compounds in Low Concentration in Australian Natural Gases Using a CF-GC-IRMS System

  25. Acknowledgements We would like to thank Ziqing Hong, Neel Jinadasa, Prince Palatty, Alex Moisis of GA for analysis of gas compositions, which provide necessary information for isotopic analysis. Isotopic Analysis of Compounds in Low Concentration in Australian Natural Gases Using a CF-GC-IRMS System

  26. Thank you! Phone: +61 2 6249 9111 Web: www.ga.gov.au Email: feedback@ga.gov.au Address: Cnr Jerrabomberra Avenue and Hindmarsh Drive, Symonston ACT 2609 Postal Address: GPO Box 378, Canberra ACT 2601

  27. Presentation Contents • Aim • Methods and Instruments • Results and Applications • Summary Isotopic Analysis of Compounds in Low Concentration in Australian Natural Gases Using a CF-GC-IRMS System

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