The Tangguh area of Bintuni Bay, east of the Seram Trough, holds West Papua's biggest gas reserves in its Paleocene and Jurassic sandstones. The effective source rocks for this area are Late Permian and Jurassic successions. Both Bintuni Bay and the Seram Trough were located on the same passive continental margin before Late Neogene deformation, which suggests that these source rocks should have equal potencies across the region. Nevertheless, one well located in the trough showed no significant quantities of gas, and the other three wells, including the Lengkuas-1 deep water well, were declared as dry holes. Basin modeling was used for the investigation of petroleum systems in the Seram Fold-Thrust Belt (SFTB) and Seram Trough foreland basin, by simplifying the SFTB thin skin deformation as an abrupt rock mass. This study is supplemented further by the source rock evaluation that showed the Jurassic interval is the primary source rock. The SFTB defonnations not only acted as an abrupt rock mass that buried down the Jurassic source rock, but also supplied low thermal conductivity sediment into the trough. Nevertheless, the result showed that decreasing heat flow in the trough was unable to keep the oil prone Jurassic source rock below the trough within the oil window. The oil generation and expulsion phases which began in the Oligocene (33 Ma) ceased in the Early Pliocene (5 Ma) as a result of SFTB initiation in the west. This Pliocene-Pleistocene event deformed most existing oil traps, replacing oil accumulations with gas.
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