Publications

The occurrence of thermogenic gas in the Ruby Field, oil in Pangkat-1X (Sebuku Block) and the recent non-commercial gas discovery at Sultan-1, Mandar Block (Oil & Gas News, Petromindo.com) proves an active petroleum system exists in the Makassar Basin. Currently, there is only one gas field being developed in this area, however, the existence of a proven petroleum system in the basin provides opportunities to discover additional hydrocarbons in this prospective area. Due the poor quality and limited coverage of existing seismic data and poor well control, this area has attracted interest from only a limited number of companies. Based on geochemical analyses, the hydrocarbons encountered to date are derived from an organic facies comprising a mixture of algal and terrestrially derived kerogens. The source rock lies within the Lower Tanjung Formation. Maturation models in the Makassar half-graben suggest that the source rock entered the oil window (Ro 0.7) in Middle Miocene time, entered to the gas window (Ro 1.3) in the Pliocene time and remains in the gas window at the present day. Potential reservoir rocks are Lower Tanjung Formation sandstones as proven in the Tanjung Field, Barito Basin some 270 kms northwest of the Sebuku Block. These high quality sands also outcrop along the eastern flank of the Meratus Ridge on Laut and Sebuku Islands. Additional reservoirs are provided by Berai carbonates comprising both reefal facies (Berlian-1) and carbonate debris (Ruby Field). Upper Warukin Formation carbonates provide an additional play if sufficiently sealed. Lateral migration via porous carrier beds is expected to have charged Eocene reservoirs pre-Mid Miocene tectonism. Vertical migration via faults would have charged the younger reservoirs post-Mid Miocene tectonism. Prospective area identification will require an indepth understanding of the maturation history and expulsion timing of the source rock coupled with timing of structural development in order to best identify valid migration pathways. Current hydrocarbon occurrences indicate that the Makassar Basin remains attractive for exploration and has potential to provide a new oil and gas province in the southern part of the Makassar Straits.