Seismic Stratigraphy and Petroleum System in the Simeulue Forearc Basin, Northern Sumatra

Kai Berglar¹, Rüdiger Lutz¹, Christoph Gaedicke¹, Dieter Franke¹, and Yusuf S. Djajadihardja^2
1Federal Institute for Geosciences and Natural Resources (BGR), Hanover, Germany
²Agency for the Assessment & Application of Technology (BPPT), Jakarta, Indonesia

Forearc basins apparently are frontier areas. The hydrocarbon potential is generally assumed to be low due to the overall low heat-flow values of subduction zones. However, exploration is far from being complete and as areas of strong subsidence, forearc basins function as a trap for sediments derived from the arc region and sediment accumulation may eventually reach levels high enough for HC generation.

This study is based on 1500 km of regional 2-D multichannel seismic data (SR 2 ms, 240 channels, streamer length 3 km, recording time 12 sec). The data were acquired during two cruises with the German research vessel SONNE in 2006 in the Simeulue forearc basin off northern Sumatra.

Two seismic sections cross industrial wells of the 70ies in shallow waters which enabled a chronostratigraphic calibration. We identified three major unconformities in the Simeulue basin, namely of base Early Miocene, base Late Miocene and base Pleistocene age. Widespread Miocene carbonate buildups are identified close to the Sumatran shoreline and in the southern part of the basin in deep water areas (~1000 m WD). Distinct bright spots above the carbonates may indicate presence of gas.

Basin modeling was carried out in 1-D and 3-D. The play concept is made up of Miocene carbonates as reservoir, marine silt and shales as seal and possible source rocks of lacustrine or paralic origin. With a maximum basin depth of up to 7000 mbsf the kitchen area is well suited for HC generation even with HF values of only 40 mW/m^2. The petroleum system modeling supports the possibility of oil generation, demonstrated by oil shows in one well on the southern basin’s edge.

AAPG Search and Discovery Article #90078©2008 AAPG Annual Convention, San Antonio, Texas