BIOGENIC AND THERMOGENIC GAS POTENTIAL IN THE EXPLORATION AREA OF SOUTHERN KUTAI BASIN, OFFSHORE EAST KALIMANTAN

• Main Author: Artha, Yudhi
• Format: Theses
• Language: Indonesia
• Subjects: Geologi, hidrologi & meteorologi
• Online Access: https://digilib.itb.ac.id/gdl/view/74281
• Institution: Institut Teknologi Bandung

Kutai Basin is a tertiary origin basin which has formed at least in the middle of Eocene which opened to the east of the present day East Kalimantan coastline. The research was conducted in the southern part of the Kutai Basin which is currently less explored than the Mahakam area and others in the northern part of this Basin. Various exploration methods and techniques are developed to find new hydrocarbon reserves and to optimize existing discoveries. Most exploration activities are oriented towards reservoir evaluation and trapping, whereas the evaluation of source rock and migration is often simplified. Therefore, this research focuses on knowing the potential of active source rock that can produce hydrocarbons and the volume that can be produced and its migration that can encourage exploration activities in this area. The method of this research is to conduct a geochemical evaluation as a screening of source rock which has the potential to generate biogenic and thermogenic hydrocarbons. Rock-Eval Pyrolysis, biomarker analysis in the form of Gas Chromatography-Mass Spectrometry (GCMS) evaluated from eight exploration wells was used to determine the quantity, quality, maturity and environment of organic material deposition. 1D and 3D basin modelling using geochemical and geological evaluations to determine the presence of thermogenic hydrocarbon shows and accumulations around the study area through migration analysis. Isotope analysis, thermal gradient and sedimentation velocity are used to determine the environment and activity of anaerobic microorganisms in generating of biogenic gases as well as geophysical analysis including interpretation and mapping of subsurface structures using 2D and 3D seismic and determining the distribution of potential source rock and its migration history. More than 6 Tcf of gas and 200 Mbbl of oil have been discovered in Upper Miocene sandstones in the deepwater Kutai Basin. Conventional cores and cuttings of deepwater strata show that source rocks facies are sandstones intercalated with shales. Organic material in deep-water sandstones includes laminar coaly fragments, pieces of wood, resinite, and other coaly debris. Geochemical data indicates that biogenic gas have been generated from within Late Miocene until recent, sedimentary section where quantity of organic matter fair to excellent (0.51 – 7.31 %wt TOC) which represent the results of micro-organism activities where sedimentation rates avg 6,2 x 107 ton/year. Thermogenic gas; however, is expected from Late Oligocene to Early Miocene series of post rift sediment throughout the Kutai Basin.