--> Abstract: Structural and Stratigraphic History of the Tapung Graben, Central Sumatra Basin, Indonesia: A Review Based on New 2D and 3D Seismic Data, by M. Soeryowibowo and T. L. Heidrick; #90935 (1998).

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Abstract: Structural and Stratigraphic History of the Tapung Graben, Central Sumatra Basin, Indonesia: A Review Based on New 2D and 3D Seismic Data

SOERYOWIBOWO, M., San Diego State University, San Diego, CA;T. L. HEIDRICK, PT. Caltex Pacific Indonesia, Rumbai, Indonesia; and E. G. FROST, San Diego State University, San Diego, CA

The Tapung trough of Central Sumatra has long been recognized based on regional seismic and gravity data. Although it is located among three large oil fields (i.e. Minas, Kotabatak and Libo), the trough has never been considered for its oil potential due to its relatively small size. A preliminary structural review indicated that some potential existed within the graben and resulted in the acquisition of more than 250 km 2D seismic in 1995. Over 300 square km 3D seismic was then acquired 1996 following the 2D evaluation that covered more than half of the graben.

The structural and stratigraphic history of the Tapung graben may represent a typical rift evolution in which rift, inversion and post-rift sequences are clearly depicted. Seismic data evaluation indicates that the trough is a half-graben, bounded by an array of en echelon, NNW-SSE striking border faults. An accommodation zone separates the graben from the South Aman graben to the north. Deposition during the Eocene-Oligocene extensional phase accumulated up to 1500 meters of syn-rift sediments. Rift development ceased during Late Oligocene time as the stress regime changed, partially expelling the syn-rift section and producing north-northwest transpressional structures. Accommodation space was created along the releasing bends of the right-lateral strike slip faults, where the Upper Red Bed Formation was deposited. The transpressional motion was active up to Middle Miocene time. Strong onlap signatures of the Upper Red Bed Formation onto top of the Brown Shale Formation suggest that this unit is not part of the synrift megasequence. Instead, it may represent the transition from synrift to post-rift.

A compressional phase took place from Late Miocene to present, lifting up both the syn-rift and the post-rift sediments. The pre-existing faults were reactivated to produce northwestsoutheast striking reverse and north-south striking strike-slip faults. The last compressional event can be easily recognized as it forms most of the oil and gas fields in Western Indonesia.

AAPG Search and Discovery Article #90935©1998 AAPG Pacific Section Meeting, Ventura, California