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The Exploration Challenges and Opportunities Left in the Mature of the West Java Basin Area, Indonesia


West Java Basin sometimes called as North West Java Basin is located in the onshore northwest of Java Island and span to offshore area as the northern boundary. The basin consist of several Paleogene sub-basins, such as Sunda, Asri, Ardjuna and Jatibarang sub-basins in the offshore and several sub basins in the onshore such as Ciputat, Kepuh, and Cipunegara depocenters. There are four main tectonic histories that influence the petroleum system in the West Java. Those are: Late Cretaceous to Early Eocene related to the growing of Sundaland to the southeast margin and formation of basement that consist of mainly metamorphic and igneous rocks. Early Eocene to Early Miocene extensional tectonic, rift basin formed with deposition of Jatibarang, Banuwati shale and Talang Akar as main hydrocarbon source rock in the area. Early to Middle Miocene, post rift subsidence resulted sag basin fills with deposition of Cibulakan in the low area and Baturaja in basement high. Middle Miocene to Plio/Pleistocene compressional tectonic resulted in big present day structural entrapment. Based on the exploration history for more than 125 years, the exploration phase in the West Java Basin can be considered as a mature exploration basin. The peak of exploration success based on size and cumulative discoveries was between years 1966 to 1999. Those successes was mainly related to new exploration blocks in the offshore of West Java as ARCO and IIAPCO operated those concession areas under the first PSC term in Indonesia. Since 2000 – until now, the trend of discoveries is getting smaller indicating that the basin is becoming a mature for the exploration. Just for comparison, the average size per well discovery was down from 60 MMBOE in the peak of exploration phase to only 23 MMBOE. However, there were some important discoveries by Pertamina in this basin recently far above that average of 23 MMBOE. Among key exploration successes relate to those discoveries are integration of finding new method and strong data support. There is some other hydrocarbon potential in the West Java Basin that left as still exploration opportunities that Pertamina has been exploring are stratigraphic plays within deep in Talang Akar and Jatibarang, structural and stratigraphic plays in Cibulakan, volcanic and basement fractured reservoirs. In addition there is indication that Mesozoic petroleum system that recently have some promise to be explored is recently be recognized in the exploration program too.