The Recent Hydrocarbon Discoveries at the Mature East Java Basin, Indonesia

Elan Biantoro and Achmad Luthfi
BPMIGAS, Jakarta, Indonesia

The East Java Basin, is one of the earliest basins in Indonesia which produced oil and gas for 114 years, yet, the basin is still very attractive for exploration. Significant oil and gas accumulation are still discovered today. The basin is developed from an oceanic basin in front of the Late Cretaceous subduction zone to presently a back arc basin behind the volcanic arc which experienced synrift and postrift periods at Paleogene, inversion processes at Neogene and volcanics uplifting influences at Plio-Pleistocene. Compressive east-west trending structural elements resulted from southern subduction dominates the present structural styles mainly in onshore basin.

New geological concepts and geophysical methods give big roles in recent discoveries. The Oligo-Miocene carbonate complex contribute significant oil discoveries such as the Banyu Urip in Onshore East Java, the Bukit Tua in Offshore Madura and the KE in the West Offshore Madura. The young reservoirs of the Pliocene globigerina sandstone and the Plio-Pleistocene volcanoclatics proved that these reservoirs could accommodate the content of commercial biogenic gas.

The case study showed that the hydrocarbon content of young shallow sedimentary rock (Pliocene) of Mundu Formation can be detected easily by high resolution seismic data. The deeper reservoir rock at the Middle Miocene sandstone of Tawun Formation and the Early Miocene limestone of Kujung Formation, some geophysical efforts are needed to detect hydrocarbon content. Seismic attribute and AVO analysis in Middle Miocene clastic reservoir at Muriah structure and Early Miocene carbonate reservoir at Offshore Madura Field resulted good imaging to locate hydrocarbon boundaries.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005