Petroleum System and Sub Basin Distribution in Tanjung Block, Barito Basin, South Kalimantan



Barito Basin is a potential hydrocarbon basin in Indonesia. Petroleum system which has developed within the basin is still one interesting case for the people who work in the oil industry regarding to the fact that Barito Basin has a large dimension, but it is not suitable with the fields being discovered successfully. Recently, there are only three fields being produced, they are Tanjung, Warukin, and Tapian Timur. Only Tanjung Field produced significantly the oil about 5000 BOPD. Whether the other Fields produced oil for about 600 BOPD. The exploration drilling in the outside of those fields has been done almost in all area of the basin, but none of the result gave the satisfied conclusion, none to be a hydrocarbon discovery well. Therefore there is an assumption that the hydrocarbon in Barito Basin only accumulated in Tanjung Field. The Barito Basin lays along the southern eastward of Sundaland and separated from Asem-asem Basin and Pasir Basin by Meratus Mountain in northwest side. To the north, the Barito Basin is delimited by Paternoster Fault System or the Bario-Kutei cross high. The structural development was began in the Early Tertiary (Paleogene) with the faulting and followed by compression tectonic in the Late Tertiary (Neogene). Rifting phase produced fault system trending SE – NW formed grabens and horsts. Meanwhile the compression regime produced the uplift of Meratus Mountain, Kasale-Sihung High, and Tanjung High. The uplift mechanism also gave effect to the reverse faults trending NNE – SSW and also the wrench faults. Activity to re-interpretate the petroleum system in Barito Basin gives description that Barito Basin which was so far being confidence as a big basin / large dimension, in fact divided into some graben systems which believe separated each other. These graben systems are Hayup, Tanjung, Amuntai, Barabai, and Miyawa Graben. The Barito Basin petroleum system can be devided into two systems, they are Tanjung Petroleum System and Warukin Petroleum System. The Tanjung petroleum system covered by shale lithology from Upper Tanjung Formation which acts as blanket seal in syn rift graben system. The source rocks consists of lacustrine shale, coaly shale, and coal. The reservoir rock consists of fluviatil sandstone and deltaic/nearshore sandstone. The source rock and the reservoir rock are the member in Lower Tanjung Formation. The hydrocarbon generation was took place in Miocene age,
therefore the accumulation was controlled by paleo structures, the later remigration to the recent structures happened as the result of basement fault inversion became thrust fault which had sealing boundary and associated with the folding events along the orogeny Plio-Pleistocene. The Warukin Petroleum System consists of source rock from shale and carbonaceous shale Lower Warukin Formation and reservoir from limestone Berai Formation, especially sandstone from Middle Warukin Member. The hydrocarbon generation was took place at Plio-Pleistocene age, 1.9 until 2.7 mya, limited bound in Warukin Formation deep which are in Bangkau Deep (southern part of Tanjung Block) and Tapian Deep. The downward migration to Berai Formation (Tanta-1 and DHS-3 well) and especially upward to the deltaic sandstone of Middle Warukin Formation. As the result of timing limitation, the hydrocarbon generation also limited, and it was expected that the hydrocarbon will be trapped in the isolated sand bodies within Middle Warukin Formation.


Authors : Gonata Pranajaya, Raden Idris, Maikel Arifin, Moh Imron