THE ORIGIN, DISTRIBUTION AND PREDICTION OF CO2 IN SOUTH SUMATRA, A CASE STUDY: JABUNG BLOCK AND SURROUNDING AREA

摘要

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 δ~(13)CCO2 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.