OFFSHORE CANNING BASIN
Northwest Shelf, Australia
Thermal history reconstruction, burial/uplift reconstruction
and hydrocarbon generation history assessed using AFTA® and
A new non-exclusive thermal history study using AFTA
and VR data
The timing of peak hydrocarbon generation in relation
to that of trap formation exerts a critical control on regional hydrocarbon
prospectivity. In regions where source rocks reached their maximum maturity
levels at some time in the past, accurate assessment of the timing of
peak hydrocarbon generation is critical in determining those areas most
likely to contain commercial hydrocarbon accumulations.
The onshore Canning Basin is known to be characterised
by a series of paleo-thermal episodes, in which hydrocarbon source rocks
reached maximum maturities at various times in different regions. Thermal
history is therefore likely to exert a critical control on hydrocarbon
prospectivity in the region.
For this study, new AFTA and VR data will be collected
from ~12 wells from the Offshore Canning Basin region, in order to identify,
quantify and characterise the major episodes of heating and cooling
which have controlled the development of maturity in the offshore region.
Integration with regional geological information will
then provide a consistent regional framework within which the history
of hydrocarbon generation in the region can be understood. Specifically,
the results of this study will provide unique knowledge on the time
at which hydrocarbon generation effectively ceased at the sampled well
locations. Coupled with information on timing of trap formation, this
allows definition of those areas where traps of a given age are most
likely to have been charged.
Exploration activity in the onshore Canning Basin has
revealed numerous small hydrocarbon accumulations generated from Paleozoic
source rocks. Previous thermal history studies carried out in this region
in connection with hydrocarbon and mineral (MVT) exploration have revealed
a series of episodes of heating and cooling, particularly in Triassic-Jurassic
and Devonian times. Because of variation in the magnitude of these episodes
across the basin, the time at which source rocks reached maximum maturity
levels, and hence the timing of peak hydrocarbon generation, shows significant
variation across the onshore region.
The relative significance and influence of these events
on hydrocarbon generation and migration in the offshore region are not
well understood, but are sure to exert a critical control on regional
hydrocarbon prospectivity. A rigorous assessment of the thermal history,
with particular emphasis on the timing of maturity development, is therefore
a vital part of prospect evaluation in this region.
Aims and objectives
The project aims to investigate these problems by direct
assessment of the timing and magnitude of paleo-thermal effects in wells
from the offshore region. Rather than relying on theoretical models
of basin evolution, use of AFTA and VR data in selected wells will allow
direct measurement of the various paleo-thermal episodes and their variation
across the Offshore Canning Basin.
Specific objectives of this new Geotrack study include:
identification of the major thermal episodes affecting
the drilled section,
quantification of the timing and magnitude of multiple(?)
characterisation of the processes responsible for each
measurement of paleogeothermal gradients during each recognised
quantitative assessment of timing of maturation of key source
estimation of the timing and amount of uplift and erosion at
each studied location,
recognition of any non-burial related thermal effects, caused
for example by heat flow variation or fluid movement,
provision of a regional thermal history synthesis, including
history of maturity development and regional variation in timing of
peak hydrocarbon generation, together with discussion of implications
for oil and gas generation.
This information will allow unique control on maturation histories
and hydrocarbon potential in the area.
Proposed work program
The project will be based on approximately 50 new AFTA
analyses and ~150 new VR analyses from ~12 wells in the Offshore Canning
Basin and the onshore margin. Sample collection will be undertaken in
May-June 1998 and sample analyses are expected to be completed by August
with the final report complete by October 1998.
The study will be written up in a comprehensive report
of 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
Volume 2. Results 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.
For further information,
please contact us