| Penulis/Author |
Budianto Toha, Ir., M.Sc. (1) ; Prof. Dr. Ir. Sugeng Sapto Surjono, S.T., M.T., IPU., ASEAN.Eng. (2); Dr. Sarju Winardi, S.T., M.T. (3) |
| Abstrak/Abstract |
The present Eastern Indonesia is largely a result of the Neogene subduction of the NW continental margin of Australian plate and its associated shelf, beneath the oceanic Banda Sea plate. The Tanimbar Islands are interpreted as the most distal parts of the Australian passive margin deformed and uplifted a foldbelt during the arc-continent collision. This collision complex is bounded to the south and east by Timor and Tanimbar Trough, interpreted as bathymetric depression (foredeep) within the Australian margin. The tectonic processes are further influenced by Late Miocene to Recent, strike-slip tectonics generated by the westward moving Pacific Plate. Since Neogene time, the Timor-Tanimbar Trough toward northwest Australian continental is actually foreland basin which developed from passive margin due to tectonic collision. The basin evolution passed through two phases of Palaeozoic extension, followed by Late Triassic compression, and then further extension in the Mesozoic that culminated in the break up of Gondwana in the Middle Jurassic. Convergence of the Australia-India and Eurasia plates in the Miocene to Pliocene resulted in flexural downwarp of the Timor-Tanimbar Trough and widespread fault reactivation in North-Western Australian Margin. This basin located in and near proven oil and gas fields such as Abadi, Bayu-Undan blocks in western area, onshore Bird Head proven area in the north and Warim block in east. To the south, basin covered Goulburn sub-basin with some hydrocarbon indication. The bending foreland basin which enhanced the "burner of the kitchen" due to collision is believed plays an important role for hydrocarbon generation in this case study area.. Nowadays hydrocarbon discoveries within Timor-Tanimbar Trough and its adjacent areas most rely on Mid Jurassic Plover reservoir , as well as Jurassic sequence considered plays important role as petroleum source rocks. The proven source rocks is mostly type III as indicated from Paleozoic-Mesozoic (Wessel, Goulburn, Arafura, Kulshill Group and Plover Fm. of Troughton Group) which charged the North West Shelf of Australian hydrocarbon field such as Petrel Sub-basin of Bonaparte Basin, Flamingo High and Sahul Platfom. The Goulburn Group source rock is the most effective in the region. The Mesozoic sediments have demonstrated source potential for Money Shoal Basin, while Troughton Group equivalent is an important source rock in The Malita/Calder Graben as good as The Flamingo Formation. Other potential source rocks are Bathurst Island Group and Darwin Formation equivalent. Examples on burial history analyses suggest that tectonic collision induced source rock maturation by two mechanisms: (1) thrust sheets are very thick due to imbrications collision, (2) the sediments mollasic eroded from the uplifted collision zone and deposited in the foredeep. Both are, respectively, have performed as thrust loading and burial sediments which forced the source rocks on foredeep of the foreland basin kitchen into oil / gas window. In summary, experiences by doing Joint Studies in others Eastern Indonesia basins suggest that tectonics collision play an important role to source rock maturation process |
