Organic Geochemistry and Rock-Eval Pyrolysis of Eocene fine Sediments, East Ketungau Basin, West Kalimantan

Abstract

Indonesia contains many Paleogene and Neogene basins which some of them have been proven to be a very prolific producer of oil and gas. A study on the result of Rock-Eval pyrolysis and biomarker undertaken on the Eocene Mandai Group was able to assess hydrocarbon potential of the Paleogene fine sediments in the frontier basin, especially West Kalimantan area. East Ketungau Basin is located in the western Kalimantan, bounded with Melawi Basin by the Semitau High in the south and West Ketungau Basin in the west. The Mandai Group was deposited in the East Ketungau Basin during Eocene, consisting of sandstone and mudstone facies. Mudstone facies comprises shale, claystone, and coal. Seven samples of Eocene fine sediments collected from East Ketungau Basin were analyzed by Rock-Eval pyrolisis and three samples for biomarker to evaluate their hydrocarbon potential. The Rock-Eval pyrolisis result of Mandai Group shows that TOC value of this facies ranges from 0.34 % to 5.16 %, Potential Yield (PY) between 0.06 and 4.78 mg HC/g rock, and Hydrogen Index (HI) from 12 to 89. Based on that result, the fine sediments of Mandai Group are included into a gas prone source rock potential with poor to fair categories. Moreover T max values vary from 426 o C to 451 o C. The Eocene fine sediments of Mandai Group fall under kerogen type III. Based on T max and biomarker analyses, the maturity of the sediments is situated within immature to mature level. The fine sediments of Mandai Group were deposited in a terrestrial to marine environment under anoxic to sub-oxic condition.

Source Rock Characterization of the Eocene-Miocene, Central Deep, North East Java Basin

“…T h u s , t h e a p p l i c a t i o n o f G C / M S ( G a s Chromatography-Mass Spectrometry) to measure the maturity of bitumen and oil directly from the distribution of sterane and triterpene is expected to replace most of the indicators of kerogen maturity. This method was also carried out by Zajuli & Suyono (2011) and Scheeder et al (2020).…”

“…Comparison diagrams between C27, C28, and C29 sterane (Huang & Meinschein, 1979in Zajuli & Suyono, 2011 are used to provide an overview of the depositional environment of the origin of the organic material (Figure 8).…”

Interpretasi Geologi Cekungan Singkawang, Kalimantan Barat, Berdasarkan Analisis Data Gayaberat dan Seismik

“…Penelitian tim sistem petroleum Mesozoikum Singkawang (Zajuli, 2016) menunjuk-kan bahwa sedimen halus Formasi Sungaibetung dan Banan memiliki potensi yang bagus sebagai batuan induk penghasil gas. Berbeda dengan cekungan di sebelah timur yaitu cekungan Ketungau dan Melawi beberapa penelitian yang sudah dilaksanakan diantaranya yaitu Zajuli & Suyono (2011) melakukan penelitian mengenai geokimia organik dan rock eval pyrolysis batuan sedimen halus berumur Eosen Cekungan Ketungau memperoleh hasil bahwa batuan induk menghasilkan gas dengan kategori jelek sampai sedang dan tingkat kematangan pada level belum matang sampai matang. Lauty (2014) meneliti diagenesis batupasir Eosen di Cekungan Ketungau dan Melawi.…”