
TY  - JOUR
A1  - Alexander, Robert 
A1  - Kagi, Robert Ian 
A1  - Woodhouse, Garry Wayne 
A1  - Volkman, John K 
T1  - THE GEOCHEMISTRY OF SOME BIODEGRADED AUSTRALIAN OILS
JF  - The APPEA Journal
JO  - The APPEA Journal
Y1  - 1983
VL  - 23
IS  - 1
SP  - 53
EP  - 63
KW  - 
UR  - https://doi.org/10.1071/AJ82006 
N2  - Degradation of petroleum in reservoirs by microorganisms is a process which has affected the chemical composition of many Australian crude oils. Oils from the Carnarvon and Gippsland Basins are used as examples to illustrate how the various classes of hydrocarbons are depleted in sequential fashion during the biodegradation process. Depletion of normal and branched alkanes, which is evident from gas chromatography, indicates that a crude oil has been mildly biodegraded. More advanced levels of biodegradation can be assessed from biomarker data obtained using gas chromatography-mass spectrometry. As the biodegradation process progresses one observes a sequential loss of n-alkanes, branched alkanes, &#x3b4;C-16 bicyclic alkanes, steranes with biological configurations, and finally, hopanes are converted into 25-norhopanes.The chemical compositions of the Eaglehawk, Rankin, and Windalia crude oils from the Carnarvon Basin suggest that they all result from a complex series of episodes of accumulation and biodegradation in the reservoirs. By assessing the proportions of each of the classes of characteristic marker compounds, and using the established relationship between reservoir temperature (depth) and the stages of hydrocarbon alteration during biodegradation, the approximate burial depths of the reservoirs at the times of biodegradation have been inferred. Thus, where multiple accumulation and degradation episodes can be recognised, the accumulation history of the oil in a reservoir can be reconstructed. 
ER  -

