junhong chen and chris boreham isotopic analysis of compounds in low concentration in australian...
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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
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Isotopic Analysis of Compounds in Low Concentration in Australian Natural Gases Using a CF-GC-IRMS System
Isotope and Organic Geochemistry Team at GA
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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
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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
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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
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Analytical Conditions (δ13C and δD)
GC conditions:• GC columns: Varian, coating: PoraPlot Q; 25m x 0.32mm (ID),
0.25m.• 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
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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
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Analysis for C1, CO2 and C2
Refe
ren
ce
Sta
ndard
C1
CO2
C2
30°C; 200:140l, 3 injections
30°C; 25:1150l, 2 injections
BF C1BF C1
44
45/44
CO2
C2
Compositions (mol%) :C1: 85.67CO2: 2.03C2: 6.47
C1
CO2C2
Isotopic Analysis of Compounds in Low Concentration in Australian Natural Gases Using a CF-GC-IRMS System
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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
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Split ratio 25:1; inject 200μl
BF:170-360s
200 400 600 800 1000Time (s)
45/44
44 C2 C3
i-C4
n-C4
i-C5 n-C5
30°C
20°C/min
230°CGC oven temperature programming
Injection time
Isotopic Analysis of Compounds in Low Concentration in Australian Natural Gases Using a CF-GC-IRMS System
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200 400 600 800 1000
45/44
44 C2 C3
i-C4
n-C4
i-C5 n-C5
Isotopic Analysis of Compounds in Low Concentration in Australian Natural Gases Using a CF-GC-IRMS System
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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.
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neo-C5
i-C4
n-C4
i-C5n-C5
GC-IRMS m/z 44 trace of C4 and C5 hydrocarbons
Split ratio: 25:1Injection volume: 200µl
Isotopic Analysis of Compounds in Low Concentration in Australian Natural Gases Using a CF-GC-IRMS System
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BF BF
GC-IRMS m/z 44 trace of neo-C5
neo-C5
i-C4, n-C4, i-C5 and n-C5 are back flushed (BF)
Split ratio: 25:1Inject volume: 8ml
Isotopic Analysis of Compounds in Low Concentration in Australian Natural Gases Using a CF-GC-IRMS System
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neo-Pentane and biodegradation
n-pentane iso-pentane neo-pentane
Biodegradation Difficulty
Isotopic Analysis of Compounds in Low Concentration in Australian Natural Gases Using a CF-GC-IRMS System
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Neo-C5: application to gas correlation
-50
-40
-30
-20
-10
C1 C2 C3 i-C4 n-C4 neo-C5 i-C5 n-C5
d13
C (
o/ o
o)
Barrow Island Z56M non-biodegraded
Barrow Island F 82M - moderately biodegraded
Tubridgi-18 - severely biodegraded
Isotopic Analysis of Compounds in Low Concentration in Australian Natural Gases Using a CF-GC-IRMS System
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-200
-150
-100
-50
0
50
100
C1 C2 C3 i-C4 n-C4 neo-C5 i-C5 n-C5
d2H
(o/ o
o)
Barrow Island Z56M non-biodegraded
Barrow Island F 82M - moderately biodegraded
Tubridgi-18 - severely biodegraded
Neo-C5: application to gas correlation
Isotopic Analysis of Compounds in Low Concentration in Australian Natural Gases Using a CF-GC-IRMS System
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Australian sedimentary basins with natural gas deposits
Isotopic Analysis of Compounds in Low Concentration in Australian Natural Gases Using a CF-GC-IRMS System
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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
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-55
-50
-45
-40
-35
-30
-25
-20-50 -40 -30 -20 -10 0
i -C4 (delta 13C, per mil)
neo
-C5
(de
lta
13C
, p
er
mil
)
Gippsland
Otway
Bonaparte
Browse
Carnarvon
Perth
Amadeus
13C neo-pentane vs i-butane
13C i-C4 (‰ )
13C
neo
-C5 (‰
)
Marine
Terrestrial
13C kerogen = 13C neo-C5 + 2‰
biodegradation
Isotopic Analysis of Compounds in Low Concentration in Australian Natural Gases Using a CF-GC-IRMS System
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N2: A preliminary study
BOC UHP N2 as reference (15N = -1.5‰)
Oxidisation furnace temperature reduced from 900C to 600C; Reduction furnace still at 630C
The N2 of air (15N = 0 ‰) was used as the standard
GC oven temperature: 30C
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
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GC-IRMS traces of N2
29/28
28, 29
Air N2: 15N = 0.29‰ stdev = 0.09
Gas 1: 15N = 0.45‰ stdev = 0.11
Gas 2: 15N = 0.54‰ stdev = 0.12
Gas 3: 15NAIR = -0.37‰ stdev = 0.10
Isotopic Analysis of Compounds in Low Concentration in Australian Natural Gases Using a CF-GC-IRMS System
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N2 Results:
-40
-35
-30
-25
-20
-15
-10
-7 -6 -5 -4 -3 -2 -1 0 1 2 3Delta N15
De
lta
13
C o
f i-
bu
tan
e
BowenGippslandOtwaySuratBonaparteBrowseCarnarvonPerthAmadeus
15N N2(‰)1
3C
i-
C4 (‰
)
Terrestrial
Marine
biodegradation
Air
Isotopic Analysis of Compounds in Low Concentration in Australian Natural Gases Using a CF-GC-IRMS System
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N2 Results:
0
5
10
15
20
25
30
35
40
45
50
-8 -6 -4 -2 0 2 4
Delta N15
N2
mo
l%BowenGippslandOtwaySuratBonaparteBrowseCarnarvonPerthAmadeus
15N N2(‰)
N2 m
ol
%
Terrestrial Marine
from ‘air’ in meteoric water
Air
Isotopic Analysis of Compounds in Low Concentration in Australian Natural Gases Using a CF-GC-IRMS System
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Isotopic Analysis of Compounds in Low Concentration in Australian Natural Gases Using a CF-GC-IRMS System
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.
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Phone: +61 2 6249 9111
Web: www.ga.gov.au
Email: [email protected]
Address: Cnr Jerrabomberra Avenue and Hindmarsh Drive, Symonston ACT 2609
Postal Address: GPO Box 378, Canberra ACT 2601
Thank you!
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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