Petroleum geochemistry of Indonesian basins is overviewed regionally for their oil and gas characteristics, and their proven sources. Published literatures and recent analyses of oils and gases from various areas in Indonesia are used to update the synthesis.
Regionally, oils of Western Indonesian basins can be grouped into three broad families: (1) lacustrine (Central Sumatra, Sunda-Asri, partly West Natuna, and West Sulawesi Offshore/North Makassar Straits), (2) fluvio-deltaic (South Sumatra, West Java, East Java, Barito, Kutai, and Tarakan), and (3) marginal-shallow marine (North Sumatra and West Sulawesi Onshore). The interpreteted source rocks for most of these basins/areas are Paleogene age shales, coaly shales, and marginal-shallow marine shales and carbonates. The source rocks of the Kutai and Tarakan basins are interpreted to be Neogene age coaly shales and coals. Most of the oils from Eastern Indonesia basins/areas are marginal-shallow marine; sourced by Neogene shales, marls, carbonates (Salawati, Banggai) or Jurassic marine shales (Bintuni), Triassic-Jurassic marine shales (Timor, Buton) or Triassic-Jurassic carbonates (Seram, Timor).
Both thermogenic and biogenic (bacterial) gas types can be recognized in Indonesia. Mixing between the two types is also commonly observed. Thermogenic gases are distributed in the basins of Sumatra, Natuna, Java, Kalimantan, Makassar Straits, Sulawesi, Papua, and Timor-Arafura. Biogenic gases are found mainly in: the fore-arc basins west of Sumatra, East Java Basin, and the foredeep area of the Sorong Fault Zone, northern Papua. High concentrations of nonhydrocarbon CO2 mainly occur in North and South Sumatra, East Natuna, and onshore Java; whereas H2S concentrations are moderate to high in some gas fields in North Sumatra, South Sumatra, East Java, East Sulawesi and Salawati Basins.
Some current petroleum geochemistry issues are observed, they include: Paleogene oil seeps in Java’s volcanic areas, marine Mesozoic oil in East Java Basin, Cenozoic oil and Pre-Cenozoic gas of Banggai-Sula area, Neogene proven source rocks of Buton area, Neogene oil seep of Northern Papua, and the application of molecular biomarkers for regional tectonic studies of Indonesia.
Geochemistry has significant contribution to exploration efficiency, because it shows genetic relationships among crude oils and source rocks. Knowing precisely what the proven source is in a basin, can help building right systematic exploration strategy for the basin.
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Satyana, A.H., 2017. Future petroleum play types of Indonesia: Regional overview, in: Proceedings, Indonesian Petroleum Association 41st Annual Convention & Exhibition, May 2017