Petroleum Systems Modelling in the Simeulue Forearc Basin off Sumatra

Rüdiger Lutz, Kai Berglar, Christoph Gaedicke, and Dieter Franke
Federal Institute for Geosciences and Natural Resources (BGR), Stilleweg 2, 30665 Hannover, Germany [email protected]. Tel/Fax: +49-511-643-2450/3663

      The Simeulue forearc basin is situated between the island of Simeulue and northern Sumatra. It is one of several forearc basins which developed along the Sunda arc from Burma to eastern Indonesia. The Simeulue basin was the target of oil and gas exploration from 1968 to 1978, when Union Oil Company held an exploration-sharing contract. During this time several wells were drilled and seismic data were acquired. All the activities focused on the near-shore shallow water (<200 m) environment (Rose, 1983). Three wells encountered gas in carbonate reservoirs but none of these accumulations were commercially successful.
      During two research cruises of BGR with R/V Sonne in January-February and August 2006 about 1500 km of 2D-seismic data as well as multibeam bathymetric, magnetic and gravimetric data were acquired. These data focus mainly on the deep-water area of the basin but one line ties three near-shore wells to the dataset. On the seismic profiles 25 carbonate buildups were identified and the majority of them are situated in current water depth of more than 1000 m. The carbonate buildups show a typical backstepping geometry at the platform margins and some are developed as pinnacles. Above these buildups strong seismic reflections (bright spots) are widespread which we attribute to gas bearing sediments. The interpretation of gas has been confirmed by amplitude variations versus offset (AVO) analysis as well as seismic inversion. The bright spots occur north-west and south-east of a depocenter where sediments of more than 6 km thickness accumulated.
       Source rocks in the study area are not confirmed by drilling but two main types of source rocks occur in SE Asia, namely non-marine lacustrine and coaly paralic source rocks (Todd et al., 1997). The Eocene “Brown shale” is a prolific source rock in the Sumatra backarc basins and Miocene coals and shales can generate liquid hydrocarbons as well as gas, e.g. Kutei Basin, Kalimantan (Peters et al., 2005). These two source rocks can be modelled with the kinetic datasets of Pepper and Corvi (1995). In a 3D-model of the Simeulue forearc basin we reconstruct the burial and temperature history and the migration and accumulation of hydrocarbons.

References
Pepper, A. S., and P. J. Corvi, 1995, Simple kinetic models of petroleum formation. Part I: oil and gas       generation from kerogen: Marine and Petroleum Geology, v. 12, p. 291-319.
Peters, K. E., J. M. Moldowan, and C. C. Walters, 2005, The biomarker guide; II, Biomarkers and isotopes in petroleum systems and Earth history, Cambridge University Press, 475-1155 p.
Rose, R., 1983, Miocene carbonate rocks of Sibolga Basin, northwest Sumatra: 12th Indonesian Petroleum Association Annual Convention, p. 107-125.
Todd, S. P., M. E. Dunn, and A. J. G. Barwise, 1997, Characterizing petroleum charge systems in the Tertiary of SE Asia, in A. J. Fraser, S. J. Matthews, and R. W. Murphy, eds., Petroleum geology of Southeast Asia, v. 126: London, Geological Society of London, p. 25-47.

 

AAPG Search and Discover Article #90066©2007 AAPG Hedberg Conference, The Hague, The Netherlands