TORQUAY SUB-BASIN
Otway Basin
1999 Acreage Release (Area V99-1)
A non-exclusive thermal history study using AFTA and VR data

v99-1.jpg (23341 bytes)

  • Large, underexplored shallow water area (Nerita-1, Snail-1 and Wild Dog-1)

  • Gas Fields to the west (Minerva and Port Campbell Gas Fields)

  • Gas shows in the Cretaceous units in Nerita-1

  • Significant source rocks and trapping potential in deeper stratigraphic units

In this study, the thermal, structural and hydrocarbon generation history of the area is assessed using AFTA and VR data to identify, quantify and characterise the paleo-thermal episodes which have affected the region, particularly key episodes of heating during the Mesozoic and Tertiary.

Project background

The Torquay Sub-Basin study area covers the V99-1 Gazettal Block in the eastern part of the offshore Otway Basin. The Early Cretaceous section in the Otway basin contains proven oil and gas source intervals but drilling to date in V99-1 has failed to prove oil and gas in commercial quantities. However, the region is underexplored, and given the close proximity of the gas markets of eastern Australia (and established infra-structure) the acreage warrants further investigation. The principal source rocks are within the Eumeralla, Pretty Hill and Casterton Formations, with gas being the most likely hydrocarbon type.

The complicated tectonic history of the region, and its profound influence on the thermal history of the potential source horizons, has not been fully considered in past exploration programs, and hence the hydrocarbon maturation and generation history is poorly understood.

Application of AFTA and VR data has allowed a complex thermal history to be unravelled, including the identification and quantification of key episodes of heating during the Mesozoic and Tertiary. These data are critical to the understanding of maturation and the timing of episodes of hydrocarbon generation relative to structural development.

The report will be of value to those companies assessing AREA V99-1, companies evaluating the potential of the onshore Otway Basin region and those with wider interests in the hydrocarbon generation history of the adjacent offshore Otway, Sorell and Bass Basins.

Specific objectives of this Geotrack study include:

• timing and amounts of uplift and erosion
• regional assessment of hydrocarbon generation history
• maximum paleotemperatures and their timing
• constraints on paleogeothermal gradients
• dominant thermal episodes relevant to prospectivity

Work program

The project is based on new and open-file AFTA and VR analyses from:

the three offshore wells:    Wild Dog-1, Snail-1 and Nerita-1

and the onshore wells:      Anglesea-1, Olangolah-1 and Hindhaugh Creek-1

Deliverables

The study is a comprehensive report in two volumes. Volume 1 will provide full details of the thermal history interpretation of AFTA and VR data from each well, while all AFTA and VR data plus supporting geological information will be presented in four Appendices in Volume 2. The main conclusions of the study will be presented in an Executive Summary with accompanying summary diagrams and tables. Full details of analytical techniques and information on data quality will also be provided.

Project available July 26th 1999

For further information, please contact us

 

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