VULCAN SUB-BASIN



  • Palaeotemperature constraints in Jabiru-1A derived from AFTA and VR plotted against True Vertical Depth (EKB).

  • Two major thermal episodes are recognised 225-160Ma (Middle Triassic-Middle Jurassic) associated with an elevated palaeogeothermal gradient and 30-15 Ma (Oligocene-Middle Miocene associated with a palaeogeothermal gradient similar to that at the present-day 27.4°C/km.



  • Reconstructed thermal history of units preserved in Jabiru-1A based on thermal history interpretation of AFTA and VR.

  • Two palaeothermal episodes have been recognised, with cooling beginning between 225 and 160 Ma (Middle Triassic to Middle Jurassic) attributed to decline in basal heat flow combined with uplift and erosion.

  • Cooling beginning between 30 and 15 Ma (Oligocene - Middle Miocene) attributed solely to uplift and erosion.

  • Timing limits derived from AFTA samples in this well are shown as the grey shading.

  • Variation of maturity with time for Jabiru-1A derived from the reconstructed thermal history, with the grey columns representing the two major thermal episodes revealed by AFTA.

  • The figure shows cessation of active source rock maturation in the deeper section at 175 Ma (225-160 Ma allowed by AFTA) due to cooling as a response to decline in basal heat flow and minor (600m) uplift and erosion.

  • The Tertiary thermal episode has no effect on the source rock maturation history in the deeper section, as palaeotemperatures during this episode were less than those during the Middle Triassic-Middle Jurassic. However, subsequent burial did result in renewed maturation in the shallower section, with cessation of active maturation occurring between 30 and 15 Ma.

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