Halmahera as a frontier area in Eastern Indonesia is in tectonically complex region where three major crustal plates: the Australian, Eurasian and Philippine Sea are interacting. The eastern part of Halmahera Island, i.e., as North East and South East arms is dominated by ophiollite complex. It is separated from the westerly volcanic terrain in the North West and South West arms by a median suture zone reflecting Pliocene Collision. The microcontinental fragment in southern Halmahera was derived from Irian Jaya as Australian microcontinent moved along the Sorong fault zone system in Paleogene time. The sediments with over 5,000 meters thickness is deposited in Weda Basin that developed until the North of Widi shelf. This basin is separated from the ophiollite province of the North East and South East arms by a major transform fault accommodating West-East movement. Seismic line E891A-05 shows the presence of Pre-Miocene sedimentary sequences. These sedimentary sequences are mature source rock and could generate the hydrocarbon in the basin. Another source rock is likely to be the Pre-Tertiary sediment of continental origin as compared to Irian Jaya. Two the plays identified as the Miocene carbonate reefs on the Widi shelf and a shallow basement high in the South of Weda Basin. Both plays depend on the existence of mature source rock considered as the hydrocarbon prospective in Halmahera.
Authors : Abdullah Sodik, M.G. Rukmiati & Joko Purnomo