Publications

Several gas discoveries in South Sumatra areas, i.e. Jabung Block, South Jambi and Corridor Block, proved to have high CO2 content with more than 40% concentration, in fact some wells in Jabung Block have more than 90% CO2 concentration. The origin of this CO2 is uncertain, it could be due to organic process (thermal breakdown of kerogen), inorganic (volcanic or upper mantle process) and/or a combination of both processes. Most of the high CO2 concentrations have been encountered in the lower Talang Akar formation and fractured Basement. A powerful tool for identification of the origin of CO2 gas is a δ13CCO2 isotope analysis (stable carbon isotope compositions of CO2). Results from isotope analysis in Jabung area shows that the origin of CO2 was predominantly from inorganic mantle degassing process with minor contribution from thermal breakdown of kerogen and carbonate. In South Jambi and Corridor Block, the CO2 was primarily a result of the hydrocarbon source type and present day reservoir temperature/depth with conntributions from inorganic and organic processes (Suklis et al., 2004). In general the main CO2 trends in South Sumatra Basin have been controlled by deep-seated faults as main conduits for the CO2, present day temperature and also the thickness of shale as sealing or barrier to CO2 migration. This paper focuses on identification of the origin, distribution and prediction of CO2 in South Sumatra Basin particularly in the Jabung Block and * PetroChina International Jabung ** JOB Pertamina-PetroChina East Java surrounding areas. A brief discussion related to the workflow and the data used in the study are also addressed in this paper. Lastly, knowledge of the CO2 origin and distribution concentration pattern will enable better prediction and minimize exploration failures in South Sumatra Basin.