Publications

The West Java Basin, sometimes called the North West Java Basin, is located in the onshore area of North West Java and its adjacent offshore area to the north. The basin consists of several Paleogene sub basins, such as the Sunda, Asri, Ardjuna and Jatibarang sub-basins in the offshore area, along with several sub-basins in the onshore area such as Ciputat, Kepuh, and the Cipunegara Low. There are four main tectonic episodes that influence the petroleum system of the West Java Basin. These are: Late Cretaceous to Early Eocene (85-50 Ma), related to the growing of Sundaland to the southeast margin and formation of basement that consists mainly of metamorphic and igneous rocks. Early Eocene to Early Miocene (50–20 Ma), extensional tectonics with the formation of rift basins resulting in the deposition of the Jatibarang, Banuwati shale and Talang Akar as the main hydrocarbon source rocks in the basin. Early to Middle Miocene (20 –10 Ma), post rift subsidence resulted in sag basin fills with deposition of the Cibulakan Formation in the low aresa and the Baturaja Formation on basement highs. Middle Miocene to Plio/Pleistocene (10–5/2 Ma) as a compressional tectonic regime that resulted in the present day structural entrapment. Oil and gas exploration in West Java began in 1871, when Jan Reering and van Hoevel drilled Maja -1 near Ciremai Mountain, based on oils seeps and anticlinal structures. However, the well was not considered commercial. The first commercial discovery was in 1897 at Tjiploek # 1, which was drilled to TD of around 300 meters, with cumulative production reported at 120 MBO. Based on the exploration history of around 125 years, the exploration phases in the West Java Basin can be defined into three phases. The first phase was from early exploration in the 1871 to the mid 1960’s. The second exploration phase occurred between 1966 – 1999, and it was considered as the first modern exploration methods both from a technical perspective and the knowledge base. The third exploration phase was between early 2000 – up until the present day, with an indicated decreasing of exploration size per well discovery. Total cumulative resources were 7.7 BBOE from 220 discovery wells, or 35 MMBOE /well. Important recent discoveries, even though the size has a different range of scale from the second phase of exploration, are the discoveries of Pondok Makmur (2008), Bambu Besar (2009), Akasia Besar (2012) and Jatiasri (2013). All those discoveries were onshore within the Sub Basins of the Ciputat, Kepuh and Cipunegara Lows, with OOIP/OGIP of 72, 100, 85 and 110 MMBOE respectively. What next from here? From the Pertamina EP point of view, based on the exploration history of the basin, with more wells, 3 D seismic data and better geological assessment, there are some exploration opportunities remaining within the West Java Basin - both onshore and offshore. Those remaining exploration potential are within stratigraphic plays within the deep Talang Akar and Jatibarang Formations, structural and stratigraphic plays of the Cibulakan Formation, along with volcanic and basement fractured reservoir play. Additionally, the Mesozoic petroleum system has recently given indications that opportunities in the biogenic gas play exist, which is proven in the offshore and less explored in the onshore.