ABSTRACT: Structural framework and inversion kinematics of the Bawal Graben , west Natuna Sea: Implications for sediment dispersal and HC migration

Restrepo-Pace, Pedro A.¹ and Mike Unger²
(1) Conoco EPT, Houston, TX 
(2) Rice University, Houston, TX

Thick successions of fluvial sediments were deposited in deep transtensional basins within the Sunda shelf (in west Natuna Sea) in Late Eocene to late Oligocene time. One of such depocenters, the NE-SW trending Bawal Graben, contains some of the best developed and seismically imaged inversion structures anywhere documented. Growth strata indicate that NE-SW trending domino- type faults developed during this extensional phase, probably related to escape tectonics that resulted from the collision of India with Asia. The grabens and half-grabens were largely segmented and hard-linked to each other by NW-SE tear faults. Diachronous and episodic inversion (as evidenced by onlaps and truncations in the syn-inversion stratigraphy) occurred between Late Oligocene to Middle Miocene, generating the Kakap/Bronang-Mamung-Ekan Emas antiformal trends. The inversion structures were later beveled by the Muda Fm. sediments ( dated ~9.5 ma -Present ) yet the basal peneplanation unconformity is locally folded by a later phase of compression. This paper summarizes the kinematics and development of the inversion structures Bawal Graben area, based on 2D seismic/balanced cross-sections and a 3D model built from a tight 2D seismic grid. Additionally, we present paleostructure maps at several sequence-boundary intervals which yield insights regarding the structural controls on sediment dispersal/deposition, kitchen development, HC migration and trap development through time. The latter indicates that there are many plays beside the present day structural culminations which remain largely untested.

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