Awang H. Satyana**, Avicenia Darwis**
** Exploration Dept., Pertamina MPS, Jl. Medan Merdeka Timur 1A, Jakarta 10110
Prospectivity of the Oligo-Miocene carbonates of the East Java Basin have been proven since 1970s when the Cities Service discovered oil and gas within these carbonates at the East Java Sea. However, the significance of the carbonates as oil producer have not obtained full attention until recently when un-interrupted significant discoveries within the carbonates have been reported. This resulted in hydrocarbon reserves in excess of 880 MMB oil and 600 BCF gas. Aggressive exploration is being made by oil companies pursuing the prospectivity of these carbonates both at onshore and offshore parts of the East Java Basin. The carbonates will hold future prosperity of the East Java Basin. The discoveries have also shown that old-worked basin is always open for new exploration Oligo-Miocene carbonates comprising the Kujung-Prupuh-Tuban-Rancak carbonates constitute the carbonate complex growing at the shelf edge areas to the southeast of the Sundaland. The carbonates trend ENE – WSW from the present onshore eastern part of the Central Java to the offshore areas north of East Java and Madura Island. The carbonates developed as platform carbonates, patchreefs, and shelf-edge reefs. Proven kitchens generating hydrocarbons trapped by these carbonates are located nearby within depression areas with mature sources range from the Eocene to the Early Miocene shales or carbonates. The paper will summarize historical and recent exploration of the Oligo-Miocene carbonates of the East Java Basin and integrate aspects of petroleum geology including the regional geology, the carbonate sedimentology and the petroleum systems.
* Proceedings Indonesian Association of Geologists (IAGI) & GEOSEA 2001 30th IAGI Annual Conference – 10th Geosea Regional Congress, Yogyakarta, September 10 – 12, 2001