Jabung Block is a part of Jambi sub-basin, representing the Northern flank of South Sumatra Basin as one of the hydrocarbon prolific in Indonesia back-arc basin. Most of the oil and gas production came from Talang Akar sandstone reservoir and also Air Benakat sandstone and Gumai sandstone as secondary objective. Pre-Tertiary basement has become a necessary potential for future exploration program. The Pre-Tertiary basement of Jabung Block consists of three different lithologies, there are granite, limestone and metasediment. Granite is concentrated in the west of Jabung, the K/Ar radiometric dating confirm the age of granite is Early Jurassic (180.4 + 3.58 ma), suggested the granite is part of the post-Triassic suturing event related to Jurassic-Cretaceous plutonism. The granite can be divided into two types, the weathered granite and fresh granite. The limestone found mostly on the Northwest and Southeast part of the block, this lithology assumed to be part of post-Mutus sediments Kluang limestone, although no radiometric dating have been conducted on this lithology. The limestone consist of wackestone to packstone, other fragments are microcrystalline and rare crystalline bioclast. The metasediment consists of low grade metamorphism lithologies, there are quartzite, schist and phyllite. These lithologies assumed to be part of Malacca Microplate consists predominantly of metasediment rock. No radiometric dating has been conducted on these lithologies. Based on the above basement lithology types, potential basement play in Jabung consist of fractured weathered granite, fractured limetones and fractured metasediment. From existing wells, proven basement play was identified in fractured weathered granite followed by the oil discovery in Betara area. Meanwhile the fractured limestones and fractured metasediment have high uncertainty due to tight lithology from existing wells. This paper will focus on the data used to characterize the basement lithology by integrating seismic data, log data and lithological description from both of cutting and core data. In addition a brief discussion related to Pre-Tertiary basement economic potential is addressed. By knowing their characteristics, would give us a better understanding regarding the Jabung block basement play and their economic potential.
Author : Teguh F, Agus H. P – Jabung Block Basement