Seismic and Sequence Stratigraphy of the Early Cretaceous Echuca Shoals Formation, Northern Caswell Sub-Basin, Browse Basin, Australia
Amir Hidayat, BSc
(University of Pembangunan Nasional)
The Early Cretaceous Echuca Shoals Formation is known as one of the potential source rock
intervals in the northern Caswell Sub-basin. Even though hydrocarbons have been discovered
in this formation in the adjacent Yampi Shelf Sub-basin, no hydrocarbons have been found in
the northern Caswell Sub-basin. Of 12 wells encountered the Echuca Shoals Formation in this
sub-basin, only three penetrated sandstone within this interval. Penetrating sand and finding
traps in the Echuca Shoals Formation has become a challenge in exploring this area.
Facies analysis and sequence stratigraphic methods were used to identify reservoir sand
distributions, to interpret depositional environments, and to predict stratigraphic traps.
Reflection configurations from seismic data, log motifs from electric logs and core data were
used to identify seismic facies. A chronostratigraphic framework was established for the
formation based on spore-pollen biostratigraphy.
The Echuca Shoals Formation in the northern Caswell Sub-basin can be divided into two
stratigraphic sequences. Sequence 1 was deposited as lowstand fans and lowstand wedges in a
deepwater environment and consists of five channels and five lobes. The channels have a
southeast-northwest orientation with an average width to thickness ratio of 1:17. Sequence 2,
which was also deposited as lowstand fans and lowstand wedges in a deepwater environment,
consists of four channels and four lobes. The channels in Sequence 2 also have a southeastnorthwest
orientation with an average width to thickness ratio of 1:21.
Terminal pinchouts of channels and lobes may represent stratigraphic traps in the area. The
results of this work indicate that in the study area there are seven potential candidates for
stratigraphic traps in the Echuca Shoals Formation.