New Tectonics Evolution and Hydrocarbon Prospect of East Java Basinal Area, Indonesia
Benyamin Sapiie1, Indro Purwaman2, and Agus H. Harsolumakso1
1Geology, Institute of Technology Bandung, Bandung, Indonesia
2Exploration, BPMIGAS, Jakarta, Indonesia
The East Java basinal area is one of the major petroliferous basins in Indonesia. However, understanding of the tectonic development of the area is still subject to ongoing debate. Detailed regional geologic investigation was carried out to study and evaluate tectonic history and basin development in relation to hydrocarbon potential of the area. Recently acquired seismic data at East Java triggered a new interpretation of tectonism and basin development especially during Paleogene time. In addition, re-interpretation of old data (surface and sub-surface), and assessment of hydrocarbon plays using newly developed concepts, may result in a new understanding of the geologic history of the basin and previously unrecognized hydrocarbon systems can be deduced. The result of this study reveals a new target for hydrocarbon exploration in the area.
A proposed new tectonics model of Paleogene system of East Java involves collision between rafted Australian continental crusts (Gondwana) namely the East Java Microplate with Sundaland during late Cretaceous. The result of the collision is reactivated pre-existing E-W faults in the basement becoming strike-slip fault systems which control the development Ngimbang graben along the pull-apart area.
2D seismic interpretation sugest two sets of faults, NE-SW and E-W trend which is controlling the distribution of Paleogene graben system in the southern part of East Java Basin. It is evident that E-W trending faults found trought the area. The lower part of the E-W grabens system filled by syn-rift deposit consist of conglomerate, quartz sandstone and shale as part of Ngimbang Fm. depositing in fluvial environments. Numbers of the field in the East Java produced from this clastic unit.
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