Publications

The North Sumatera Basin is a tertiary back-arc basin located in the Northern side of Sumatera Island. It is recognized as a mature basin of prolific hydrocarbons in Indonesia. The main recognizable source rock of the petroleum system is the Bampo Formation. However, it is not the only source rock generating hydrocarbon of the system. There are also the Belumai and Lower Baong marine shale with potential TOC content about 1% (Pertamina BPPKA, 1995) and 0,8-3,5% (Bahesti et. al., 2013) respectively. A study based on geochemical and paleogeography data has been conducted to generate kerogen type and its distribution for Lower Baong Formation. Geochemical and biostratigraphy data from eight PT. PERTAMINA Hulu Energi wells (namely IS-1, ES-1, PO-1, IR-1, WL-1, WL-2, WL-3 and PR-1) are used for this study. Geochemical data was earned from “Rock Eval” pyrolysis to know Tmax and hydrogen index (HI). Tmax and HI were plotted in XY-axis to learn kerogen type and maturity. Biostratigraphy data was used to understand paleobathymetry in interpreting paleogeography. A combination of the data was used to create a kerogen type distribution map. The result shows that the Lower Baong Formation consisting of predominantly shale was deposited in outer neritic/shelf until upper bathyal/slope at N9-N14 (Middle Miocene). Kerogen type identified from five wells, they are ES-1 well (outer neritic/shelf) shows type II (oil-prone), WL-1, WL-2, WL-3 and PR-1 well (upper bathyal/slope) show type II/III (mixed oil/gas-prone). Kerogen type II and II/III generally formed in marine setting fit to the paleogeography. Paleogeography can be used to interpret the kerogen type distribution while geochemical data is limited. From the analysis, it can be concluded that shallow marine setting can be interpreted to produce kerogen type II while deep marine setting can produce type II/III, but it depends on the paleogeography of the area itself.