Publications

The Jambi Sub-basin is part of the prolific South Sumatra back arc basin formed by the interaction of the Indo-Australian and the Eurasian plates in Pre-Tertiary and Early Tertiary time. The Jambi Sub-basin has been proven to produce conventional oil and gas in large quantities, most of the oil and gas have come from the Talang Akar formation (TAF) source rocks and the other is estimated to come from the Lemat / Lahat formation (LEF/LAF) source rocks. These source rocks also have potential for future unconventional oil and gas. Based on wells data analysis, the Talang Akar was deposited in littoral-neritic environment during Late Oligocene - Early Miocene time. Meanwhile Lemat / Lahat Formations were deposited in supralittoral-littoral during Late Eocene - Oligocene time. The geochemical analysis results shows the TAF source rocks tends to have Type II / III and III kerogen with the TOC values more than 2 wt%. The S2 values vary widely between 0.1 and 40 mgHC/g and hydrocarbon index (HI) values ranging from 50 to600 mgHC/g. From the two wells, the LEF/LAF source rocks are also dominated by TOC values ≥ 2 wt% with Type II / III and III kerogen, the S2 values vary between 0.5 and 20 mgHC/g and HI values ranging from 100 to 450 mgHC/g. Seismic interpretation has been able to define several sequence boundaries, which the sequence 1 equivalent to the lower LEF/LAF, but sequence 2 is not always correlated with the upper LEF/LAF while sequences 3 and 4 are equivalent to lower and upper of TAF. These sequences are interpreted and could have potential for shale plays. An integrated geology, geochemistry, petrophysics and geophysics analyses have identified sweet spot for potential unconventional oil and gas shale plays.