ABSTRACT: A Neogene-Recent tectonic model for the Timor Sea Area, Offshore Australia: geomechanical implications for charge, trap and retention
Shuster, Mark W.1, David A. Castillo2, Eaton Simon1 (1) Shell Development (Australia), Perth, Australia (2) GeoMechanics International Inc. (Australasia), Magill, Australia
A tectonic model invoking wrench-related deformation and strike-slip reactivation of
structures in the Greater Timor Sea from the Neogene to the present day associated with
convergence between the Australian and SE Asian plates is consistent with observed
kinematic and present-day stress indicators
, subsidence trends, and recent earthquakes.
Strike-slip faulting in the Australian sector is associated with oblique convergence and
extension related to flexure of the loaded and partially subducted Australian plate, where
present-day deformation is accommodated along pre-existing faults. Assessment of
structural maps, isopachous maps and tectonic subsidence curves indicate that areas such
as the Cartier Trough and Malita Graben formed as pull-apart basins associated with rapid
infill during the Neogene wrench-related deformation. Understanding the structural history
in these basins is extremely important given they are associated with late (Neogene)
hydrocarbon
charge.
Analysis of borehole images data, drilling pressure records, and laboratory rock
strength data have been used to construct a well-constrained stress tensor for the Timor
Sea area in several blocks within ZOCA and AC/P. The regional maximum horizontal stress
direction (SHmax) in the Timor Sea area is approximately N-S and sub-parallel to the
convergence direction between Australia and Indonesia. East of ZOCA, the convergence
direction is consistent with an observed NE-SW SHmax stress direction. In situ
measurements of stress magnitudes indicate a strike-slip stress regime
(SHmax>Sv>Shmin) consistent with recent earthquakes. The tectonic model has direct
implications for
hydrocarbon
exploration in that prospect risks associated with Neogene
fault trap reactivation and charge can be regionally assessed before drilling.
AAPG Search and Discovery Article #90913©2000 AAPG International Conference and Exhibition, Bali, Indonesia