Nias basin, NW Sumatra – new insights into forearc structure and hydrocarbon prospectivity from long-offset 2D seismic data



Last week, my colleague from TGS, Ian presented a talk in the 38th Indonesian petroleum Association annual meeting. He talked about the structures and hydrocarbon prospectivity of Nias forearc basin, which is situated in the central part of the offshore Sumatra forearc area. 1868 km of newly acquired long offset 2D seismic, covers the area in between Nias and Sumatra mainland. Compare to the other offshore Sumatra forearc basins, the water depth in Nias basin is much shallower (~500m),  than the other basins (up to ~1500m), reflecting much more carbonate platform growth and forearc sediment fill. The new data set show thick sediments with half-graben/syn-rift character beneath the Neogene sequences that interpreted as Paleogene. By using using the low geothermal gradients observed in wells in the area, the temperature in the bottom half of the Paleogene section is calculated to be sufficient to expel hydrocarbons from lacustrine or coaly sediments.

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New insight on the deformation along the southern Java forearc

This note is taken from an abstract presented at American Geophysical Union, Fall Meeting 2012. The new seismic data set in south Java resolved detailed structures of the southern Java forearc. The plate interface expressed as irregular surface in the western part and rather a continuous smooth boundary in the eastern area. This observation coincides with the higher uplift of the western part of the forearc high. Cluster of shallow earthquakes can be observed near the western part of Java trench. Deformation of the forearc high is more intense in the west compared to that in the east. This coincides with higher uplift of the western part of the forearc high, thus complicated the structures.

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