The research involves mapping of subsurface at a scale of 1:25,000 the top of three geological formations in the Southern Part of Sumatra – the Airbenakat Formation, the top of the Talangakar Formation, and the top of structural basement in the Jambi Trough. Isopach maps of the formations will be constructed. These maps will form the basis of a basin analysis and hydrocarbon source rock assessment of the Jambi Trough using Basin Mod basin modeling software (Rockworks Software). The studies utilize the L. Bogue Hunt Southeast Asia database housed in the Department of Geological Sciences at Ball State University. Seismic record sections, geophysical logs, cutting descriptions, and paleontological reports will provide basic geological data to enable mapping of the three horizons. Although hydrocarbon accumulations are abundant in Central and Southern Sumatra, the nature of the source rocks is only partially understood. The proposed research will map the Airbenakat and Talangakar Formations while identifying the areas of thermally mature source rock is the main goal of the research. This study will identify characteristics which will enable the identification of thermally mature rocks in other regions of Sumatra. The area of the project is located at the Southeastern part of Asia in Indonesia and mainly the Jambi trough located in Southern Sumatra. Generally, the geology and tectonics of this area (Sumatra) is controlled by the subduction of the Indian plate towards the east and beneath the Eurasia plate. / Department of Geological Sciences

According to the Ade observation (Ade, W., pers. Comm.) “95% of all commercial oil fields in the Sumatra region occur within 17 km of seismically mappable structural grabens in the producing basins”. The Ade observation proposes a link between the subsidence of the source rocks (the Talang Akar Formation) in the grabens and the maturity of the organic material. To test the validity of the Ade observation, subsurface mapping of the region was carried out using geophysical logs. Using the well log information, the basement and the formation tops have been mapped with a special emphasis on Talang Akar and Air Benakat Formations. The isopach maps of these formations show that most of the producing wells on the Sunda shelf are in fact located in and around the major structural basins. Trends in the occurrence of the oil fields have also been observed which are analogous to the orientation of the grabens. Structural mapping of the basins have identified several wrench faults. These are of particular interest as wrench faults provide good structural traps for oil in the Los Angeles and the North Sumatra Basins and may prove to be very important for future exploration in southern Sumatra and northwest Java. In South Sumatra Basin, 77.78% of the potential oil fields are located in the 17 km margin from the grabens. For Sunda/Asri Basins and the Ardjuna Basin, it is 100 and 92 respectively. Identifying the source rocks in this 17 km window will enhance the success rate of oil exploration in the Sundaland Basins. / Department of Geological Sciences