Authors / CoAuthors
Boreham, C. | Edwards, D. | Poreda, R. | Henson, P.
Abstract
Over 800 natural gases representative of Australia's hydrocarbon-producing sedimentary basins have been analyzed for their helium abundance and around 150 gases for their helium isotopic composition (supplemented by isotopic compositions of the higher noble gases Ne, Ar, Kr and Xe). Helium shows abundance up to over 10% with the highest values in the Amadeus Basin (central Australia), while <sup>3</sup>He/<sup>4</sup>He ratios range from around 0.01 to 4.2 Ra (Figure 1). The Gunnedah Basin of south-east Australia and the Bass and Otway basins in southern Australia show the highest <sup>3</sup>He/<sup>4</sup>He ratios, indicating a significant mantle contribution. Interestingly the adjacent Gippsland Basin has slightly lower <sup>3</sup>He/<sup>4</sup>He ratios. The associated CO<sub>2</sub> has a relatively low abundance in the Gunnedah Basin (highest <sup>3</sup>He/<sup>4</sup>He ratio) compared to some extreme concentrations of CO<sub>2</sub> in the Otway Basin, which are associate with recent volcanism. The onshore Bowen and Cooper basins of eastern Australia, where natural gases are predominately sourced from Permian coals, show intermediate <sup>3</sup>He/<sup>4</sup>He ratios with the former having a higher mantle contribution. At the other end of the spectrum, low <sup>3</sup>He/<sup>4</sup>He ratios characterize natural gases of the Bonaparte, Browse, Carnarvon and Perth basins in northern and south-western Australia where radiogenic helium predominates. The minor mantle contribution that is inferred from the He isotopes in these regions has resulted from the limited volcanic activity and igneous intrusions throughout the basins' evolution. The accompanying high CO<sub>2</sub> contents of some of these gases, together with their carbon isotopic composition, infer an inorganic source most likely from thermal decomposition of carbonates. The geochemical data suggest that the origin of helium in Australian natural gas accumulations is region specific and complex with the component gases originating from multiple sources. The relative low CO<sub>2</sub>/<sup>3</sup>He ratio for many natural gases indicates a systematic loss of CO<sub>2</sub> from most basins. The process by which CO<sub>2</sub> has been lost from the system is most likely associated with precipitation of carbonates (Prinzhofer, 2013). The age of the source (or reservoir) rock has a primary control on the helium content with radiogenic <sup>4</sup>He input increasing with residence time (Figure 1). With the recent acceleration in the exploitation of Australia's enormous reserves of natural gas, the LNG processing plants in western, northern and eastern Australia offer the opportunity to commercialize helium in gases with as low as 0.1% He. However, a key factor to the gases monetary value is its inherent N<sub>2</sub> content. From the <sup>15</sup>N/<sup>14</sup>N ratios, N<sub>2</sub> associated with mineral decomposition severely impacts the economics of helium extraction. Presented at the 2017 International Meeting in Organic Geochemistry (IMOG)
Product Type
document
eCat Id
112901
Contact for the resource
Point of contact
Cnr Jerrabomberra Ave and Hindmarsh Dr GPO Box 378
Canberra
ACT
2601
Australia
Resource provider
Point of contact
- Contact instructions
- MEG
Keywords
- theme.ANZRC Fields of Research.rdf
-
- EARTH SCIENCES
- ( Feature type )
-
- Helium
- ( Feature type )
-
- natural gas
- ( Feature type )
-
- isotopes
-
- Published_External
Publication Date
2025-01-09T00:50:45
Creation Date
2016-12-21T00:00:00
Security Constraints
Legal Constraints
Status
completed
Purpose
Presentation at International Meeting in Organic Geochemistry, Italy 17-22 September 2017
Maintenance Information
asNeeded
Topic Category
geoscientificInformation
Series Information
International Meeting in Organic Geochemistry (IMOG), 17-22 September 2017, Florence, Italy
Lineage
Presented at the 2017 International Meeting in Organic Geochemistry (IMOG)
Parent Information
Extents
[-39.23225314171632, -9.795677582831559, 110.56640625, 155.03906249999997]
Reference System
Spatial Resolution
Service Information
Associations
Source Information