Understanding the plumbing of the Gippsland Basin: new results on fluid migration and reservoir quality

Abstract

Understanding the CO2 storage potential and petroleum prospectivity of the Gippsland Basin are critical to managing the resources of this region. Key controls on determining the prospectivity for CO2 storage and petroleum include understanding the fluid migration history and reservoir characteristics in the basin. Gippsland Basin hydrology, reservoir characteristics and petroleum systems are being studied to better understand how CO2 can be safely stored in the subsurface. Hydrocarbon migration pathways have been delineated using petroleum systems modelling. The latest hydrocarbon charge history data has been acquired to test the containment potential of individual structures along these migration pathways. The charge history results indicate the Golden Beach gas field has had a complex hydrocarbon fill history, and that early charge has migrated through the regional seal. The results also indicate that early oil charge was very common in the basin, including large structures that are now filled with gas (e.g. Barracouta). The results allow the regions with good CO2 containment potential to be delineated for further storage investigations. A new evaluation of the reservoir characteristics of the Latrobe Group—through porosity/permeability analysis and automated mineral analysis (AMA)—has provided insights into CO2 injectivity and capacity. The AMA results constrain the mineralogy and diagenetic history of the reservoirs and seals. In addition, the data highlights the presence of carbonates, glauconite and K-feldspar that are potentially reactive with injected CO2.

Out of Gondwana

“…The dominant and most prolific source, however, is the coals and carbonaceous shales within the Latrobe Group (Austral 3). There were several episodes of generation and expulsion, but the first major hydrocarbon charge was probably oil in the Late Miocene, which was partially displaced Brien et al, 2008;Tingate et al, 2011) Field outlines are provided by Encom GPinfo, a Pitney Bowes Software (PBS) Pty Ltd product. While all care is taken in the compilation of the field outlines by PBS, no warranty is provided regarding the accuracy or completeness of the information, and it is the responsibility of the reader to ensure, by independent means, that those parts of the information used by them are correct before any reliance is placed on them.…”

“…(e) Present-day Gippsland Basin, showing the postulated distribution of hydrocarbon accumulations and migration pathways. (Sources: modified from O'Brien et al, 2008;Tingate et al, 2011)…”