WESTERN BONAPARTE BASIN
THERMAL HISTORY RECONSTRUCTION IN THIRTEEN WELLS USING
APATITE FISSION TRACK ANALYSIS AND VITRINITE REFLECTANCE
A non-exclusive study by Geotrack International
New thermal history data has been obtained from
a total of 44 AFTA samples and 64 VR samples in 13 wells on the Londonderry
High in the western Bonaparte Basin.
This study reveals key aspects of the evolution of
this platform area, including quantitative estimates of the timing and
magnitude of maximum paleotemperatures, Middle Tertiary paleo-geothermal
gradients and amounts of uplift and erosion.
THR (Thermal History Reconstruction) has been
employed in 13 well sections to enable the direct determination of paleotemperature
versus depth profiles, and thus the assessment of mechanisms of heating
and cooling during paleo-thermal events. Our thermal history approach
has also enabled constrained predictions of the maturation levels of
key source rock units.
These issues are vital to a rigorous evaluation of
the hydrocarbon potential of the Londonderry High, and have been addressed
by direct and quantitative assessment of thermal histories using new
AFTA and VR results. New results have provided a thermal history framework
from which the tectonic and maturation histories of this region have
Introduction and objectives:
This report presents the results of a non-exclusive
regional study, which utilises data from Apatite Fission Track Analysis
(AFTA®) and Vitrinite Reflectance (VR) to identify, characterise and
quantify any major episodes of heating and cooling which have affected
the drilled sections in thirteen wells from the Londonderry High
region of the western Bonaparte Basin. This information is used
to reconstruct a thermal history framework from which the burial and
uplift, and hydrocarbon generation history can be understood.
The main objectives of this regional study were:
1) To determine the timing and magnitude of maximum
paleotemperatures in each sample;
2) To determine the profile of maximum paleotemperatures
in each well;
3) To characterise the mechanisms controlling heating
and cooling in each paleo-thermal episode, where applicable;
4) To estimate, where appropriate, the amount of section
removed by uplift and erosion;
5) To assess the regional variation in mechanisms of
heating and cooling, and styles of thermal and burial histories; and
6) To assess the regional variation in the potential
for hydrocarbon generation.
Two distinct paleo-thermal episodes were identified
in this study. The first of these may reflect deeper burial with cooling
due to uplift and erosion beginning some time between 50 and 25 Ma (Eocene-Oligocene),
as constrained by AFTA. The second event was probably associated with
localised heating in the Late Tertiary (possibly within the last 5 Ma),
and was most likely due to the passage of hot fluids.
Detailed results for each of the study wells are available
in the Final Report, as are discussions on the variations in the styles
of the thermal, burial and maturity histories throughout the Londonderry
High region. The thirteen study wells are: Crane-1, Cygnet-1, Peewit-1,
Whimbrel-1, Ibis-1, Plover-1, Rambler-1, Kite-1, Tamar-1, Garganey-1,
Osprey-1, Ascalon-1A and Torrens-1.
For further information, please contact Ian