ABSTRACT: Neogene structural modifications of petroleum systems of the Timor Sea

Clough, Martyn¹, Myra Keep¹, Ian Longley²
(1) University of Western Australia, Perth, Australia 
(2) Woodside Energy Ltd, Perth

A number of identifiable Neogene structural styles in the Timor Sea region result from plate collision of the Indo-Australian and Pacific plates. Most styles show net normal reactivation of older extensional faults, but simple net displacement masks complex reactivation histories. Pulses of deformation at 25, 8 and 3 Ma reflect partitioning of plate-scale stresses into discrete wrench and flexure components, with the magnitude and relative proportion of each component changing significantly along strike from NW to SE.

In the NE, around Sunrise/Troubadour, Neogene reactivation has caused broad, seafloor-penetrating faults zones which reflect a strong control by flexural bending of the Australian plate into the Timor Trough. The flexural component decreases to the SW, with a corresponding increase in the left-lateral wrench component of movement. Around the Laminaria High this transition in plate-scale controls is manifest by smaller discrete faults showing small, net normal offsets, with no significant seafloor displacement. An increasing wrench component further to the SW has resulted in complex net normal, net reverse and strike-slip fault displacements adjacent to the Timor Trough, and left-lateral wrench pull-apart in the Cartier Trough. The latter represents a releasing bend of a left-lateral strike-slip system. The partitioning of strain into discrete zones of tectonic control has direct bearing on the structural risk of petroleum systems in the area. A greater risk of trap breaching has already been identified along the shelf margin. Results of this study indicate that the risk will change significantly along the margin depending on the dominant tectonic control.

AAPG Search and Discovery Article #90913©2000 AAPG International Conference and Exhibition, Bali, Indonesia