GEOPHYSICAL ANALYSIS OF THE SUMATRA BASINS: SOURCE ROCKS, STRUCTURAL TRENDS, AND THE DISTRIBUTION OF OIL FIELDS

According to the Ade hypothesis 95% of all commercial oil fields in the Sumatra region occur within 17km of seismically mappable structural grabens in the producing basins. The hypothesis 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 hypothesis, subsurface mapping of the region is being carried out by using geophysical logs and seismic sections. The depths to the formation tops, basement and the information about the type of wells are being used to create isopach maps as well as cross sections of the entire Sunda shelf region.

Using the well log information, 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. Further study of the data will enable us to determine the spatial distribution of the producing oil fields and the frequency of their occurrence in the given distance margin. Identifying the source rocks in this 17km window will enhance the success rate of oil exploration in Sumatra and throughout the Sundaland craton.