Print this page ABSTRACT: 
Thermal
history modeling using organic matter maturation data from normal
pressure systems in the Offshore Carnarvon Basin, Northwest Shelf, Australia
He, Sheng, Mike Middleton, and Lindsay Collins , Curtin University of Technology, Perth, Australia
The Offshore Carnarvon Basin consists of a series of the Jurassic-Cretaceous rifting
sub-basins as a result of lithospheric thinning and oceanic crust spreading associated
with the breakup of the Gondwana continent. Two subsidence and thermal periods can be
recognized in the evolution of the Offshore Carnarvon Basin. The period of rifting,
lasting from the late Early Jurassic to Early Cretaceous, resulted in tens of kilometers
of sediments being deposited in the rift grabens, and up to 2000 m of sediments were
eroded on the uplift areas of the eastern and northern rift shoulders. The period of
post-rifting is characterized by thermal subsidence in the Cretaceous.
Vitrinite reflectance and Tmax profiles from several exploration wells in
various tectonic units with normal pressure systems have been selected for this modeling
using a temperature-time basin model. The study indicates that the maturity profiles did
not undergo the retardation by paleo-overpressure systems during their rifting thermal
history. However, some vitrinite reflectance profiles have been corrected for suppression
due to hydrogen-rich vitrinite. The study suggests that normal pressure is not an
important factor in organic matter maturation, and the proposed basin model is capable of
modeling thermal history using maturation data in normal pressure systems. The rift
thermal model can provide a good fit to the vitrinite reflectance and Tmax
profiles and present day geothermal field. The peaks of rift heat flow in the rift garbens
and Exmouth Plateau ranged from 60 to 80 mW/m2, while the rift shoulders
experienced a lesser rifting thermal
increase.
AAPG Search and Discovery Article #90913©2000 AAPG International Conference and Exhibition, Bali, Indonesia