Hydrocarbon Potential And Environmental Interpretations Of The Jurassic-Lower Cretaceous Section In Five Wells In The Eromanga Basin.
Mudge, Wayne John
Honours Degree, 1980
University of Adelaide
Five wells along a line of section trending north-south in the southern Eromanga Basin were studied using petrographic techniques to delineate petroleum source rocks and possibly aid in environmental interpretations. The wells studied were Kudrieke #1, Tirrawarra #2, Merrimelia #5, Gidgealpa #15 and Gidgealpa #16.
The dispersed organic matter (d.o.m.) in the Birkhead Formation is dominated by vitrinite and exinite. Examination of the coals in the Birkhead Formation shows the precursors to have been large woody trees relatively free of alteration before burial. The Namur Member consists predominantly of sands deposited in a fluvial environment but shows significant silts in the cuttings of Kudrieke #l to warrant analysis. Exinite is dominant in the lower half, while the Upper Namur Member shows an even spread of all three groups of macerals in the d.o.m. The dispersed organic matter in the Murta Member is exinite rich in Tirrawarra #2, Merrimelia #5 and Gidgealpa #15, while an even spread of all maceral types occurs in Kudrieke #l and Gidgealpa #l6. The Murta Member was possibly deposited in a freshwater lake which experienced periods of anoxic conditions. The Transition Beds show a similar d.o.m. content to that of the Murta Member which, however contains more terrestrial sources. This also exhibits periods of anoxia and may have been deposited in a marine environment.
The Murta Member shows the greatest source rock potential containing abundant Type-I kerogen. The overlying Transition Beds also contain Type-I kerogen but not to the same extent as the Murta Memher. Source rock potential exists in the Birkhead Formation with Type-II kerogen being present in significant amounts. Vitrinite reflectances place the maturity of the sediments in the pre-oil to early-oil generation stage.