--> Abstract: Contribution of Paleogene and Neogene Sediments to the Petroleum System in the Banyumas Sub-Basin, Southern Central Java, Indonesia, by Eddy A. Subroto, Anditya Ibrahim, Eddy Hermanto, and Dardji Noeradi; #90082 (2008)

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Contribution of Paleogene and Neogene Sediments to the Petroleum System in the Banyumas Sub-Basin, Southern Central Java, Indonesia

Eddy A. Subroto1, Anditya Ibrahim2, Eddy Hermanto2, and Dardji Noeradi1
1Dept. of Geology, Bandung Institute of Technology (ITB), Bandung, Indonesia
2Study o Lead and Prospects, BPMIGAS, Excecutive Agency for Upstream Oil and Gas Business Activities, Jakarta, Indonesia

The existing of petroleum system in the Banyumas Sub-basin, Central Java Island, Indonesia has been proven. Several oil seepages have been found in the area. However, hydrocarbon source in the sub-basin remains a mystery. The main problem is the lack of exploration wells that penetrated the suspected source rock(s). In 2007, an exploration well, namely Jati-1, has been drilled in the area. A series of cuttings samples from 2,040 ft to 14,740 ft, mostly belong to the Middle to Late Miocene Panosogan Formation, has been studied. Screening geochemistry has been performed to 213 cuttings and a detailed geochemistry analysis that includes gas chromatography (GC), GC with mass spectrometry (GC-MS), and carbon isotope has been performed to some selected samples.

It has been speculated that the suspected source rock(s) within the sub-basin could be from Neogene and/or Paleogene sediments. A series of sediment samples comprising Paleogene and Neogene intervals, therefore, have been collected during this study. Detailed geochemical analyses have also been performed to some selected sediments. The characters of the sediments from both intervals have been defined.

Four oil samples (one from DST and three seepages) are available for this study. Two of the seepages have experienced mild biodegradation. Biomarkers study indicates that the oils display a more fluviodeltaic character rather than marine feature. The biomarker distributions also reveal that, in general, all of the oils can be grouped into one family except for their isotopic data. The results indicate that both Paleogene and Neogene intervals are possible to be the hydrocarbon sources in the sub-basin.

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