HYDROCARBON SOURCE ROCK CHARACTERIZATION AND PYROLYSIS KINETIC MODELING OF TORAJA FORMATION ENREKANG SUBBASIN SOUTH SULAWESI PROVINCE

• Main Author: Ardianto Budiman, Agus
• Format: Dissertations
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/81022
• Institution: Institut Teknologi Bandung

This study was conducted due to oil seeps in Batu Ke'de Village, Masalle District, Enrekang Regency, South Sulawesi Province. According to prior research, the oil seeps are associated with the fine clastic rocks of the Paleogene Toraja Formation. The objective of this research is to assess the potential for hydrocarbon formation by analyzing the characteristics of organic materials and the correlation between biomarkers from the oil seeps and hydrocarbon source rocks. Additionally, it involves modeling the pyrolysis kinetics of source rocks from the Toraja Formation. The scope of this research is petroleum seeps and organic-rich sedimentary rocks of the Toraja Formation which spread from the southern part of Enrekang Regency to the northern part of North Toraja Regency using organic geochemical, organic petrological, palynological, and kinetic analysis methods. The hypothesis to be proven is that the character of petroleum seepage in the study area is related to the character of certain rocks in the Toraja Formation. The novelty of this study is that it comprehensively combines organic geochemical analysis methods, organic petrology, palynology, and kinetic modeling for the study area. It is expected that the combination of those analytical methods can complement each other. The combination of those analytical methods can complement each other. The total organic carbon content of the claystone samples varies from 0.03 to 4.52 wt% and are classified as poor to excellent. The claystones are immature to postmature with a mixture of Type II and III kerogen. Their vitrinite reflectance values range from 0.47 – 4.52% Ro. The samples of Toraja Formation rock and the oil seep source rock might have a similar depositional environment in a deltaic marine depositional setting with high oxidizing conditions. Organic material sources for rock and oil samples are dominated by terrestrial input. The oil is inferred to have originated from Paleogene source rocks, which correlated in age with the Toraja Formation. The recovered palynomorphs from the studied rock samples suggest a late Eocene to Oligocene age with a strong terrestrial influence of shallow marine depositional setting. The biomarker analysis shows that the rock samples have a more substantial contribution from the terrigenous higher plants, while the oil sample indicates a higher degree of marine influence. The maturity levels also differ between the oil (peak mature) and the analyzed rock samples (immature). v The kinetic parameters of the Toraja Formation source rock show an activation energy distribution with dominant values of 100 and 99 kJ/mol with a frequency factor of 7.23 E+9 and 4.04 E+9 /sec. The activation energy distribution model shows the combined characteristics of Type II and Type III kerogen with low heterogeneity of the original material in a transitional depositional environment with dominant marine influence. It is inferred that the oil seep source rock is equivalent to the analyzed rock sample but more mature, having been deposited under more marine conditions. The oil seep source rock is not exposed and is located in the deeper part of the basin. A deeper marine facies (distal delta front and prodelta facies) in front of the delta mouth bar is interpreted as the source rock of the oil seep sample.