ABSTRACT
The Browse Basin Province 3913, offshore northern Australia,
contains one important petroleum system, Late Jurassic, Early Cretaceous-Mesozoic.
It is comprised of Late Jurassic through Early Cretaceous source rocks
deposited in restricted marine environments and various Mesozoic reservoir
rocks deposited in deep-water fan to fluvial settings. Jurassic age intraformational
shales and claystones and Cretaceous regional claystones seal the reservoirs.
Since 1967, when exploration began in this 105,000 km2 area,
fewer than 40 wells have been drilled and only one recent oil discovery
is considered potentially commercial. Prior to the most recent oil discovery,
on the eastern side of the basin, a giant gas field was discovered in 1971,
under a modern reef on the west side of the basin. Several additional oil
and gas discoveries and shows were made elsewhere. A portion of the Vulcan
sub-basin lies within Province 3913 where a small field, confirmed in 1987,
produced 18.8 million barrels of oil (MMBO) up to 1995 and has since been
shut in.
Numerous untested structures and other prospects, along
with proven oil and gas accumulations, provide for many exploration opportunities
and the potential for this area to be a significant contributor to the
petroleum resources of Australia. Development of infrastructure for this
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remote location will come with the discovery
of additional reserves both here and in the adjacent Bonaparte Gulf and
Timor Sea areas.
INTRODUCTION
One Total Petroleum System(TPS) involving Late Jurassic
through Early Cretaceous source rocks and Mesozoic reservoir rocks has
been identified in the Browse Basin Province 3913, and called the Late
Jurassic, Early Cretaceous-Mesozoic TPS (Fig. 1). Major subsidence in this
Mesozoic basin occurred in the Cretaceous when restricted marine conditions
provided for thick and high quality source rock deposition. Maturation
of this source rock is greatest in the northern portions of the area but
combined vertical fault migration and long-range lateral migration have
sourced discoveries in the northern, southern, central, and far eastern
portions of the basin. The area is sparsely explored. One oil discovery
in 1997 is estimated to double the proven reserves and has increased interest
in the Browse Basin as a potentially significant petroleum province of
offshore Australia. Additional hydrocarbon source rocks of Triassic and
Early Jurassic age are possible. Contributions from these source rocks
are not well documented.
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