Organic geochemical characterization of the seeped oils and Paleogene source rocks in the Southwest Java']Java Basin (SWJ), Indonesia; tectonostratigraphic consideration on oil to source rock correlation

This study's main aim is to establish the organic geochemical relationship between the seeped oils as well as between the oils with the exposed Paleogene rocks in the Southwest Java (SWJ) Basin. Based on organic source input, depositional setting, and age diagnostic-related biomarkers, three oil groups of SWJ are proposed. SWJ oil group 1 (Cipari oil) is characterized by a dominant terrestrial organic matter input with low marine influence and is considered to correlate with Bayah and Citatah Formations with probable contribution from the Karangsambung Formation. Maja oils represented the SWJ oil group 2 and were correlated with the Walat Formation, which was sourced from a moderate marine and terrestrial organic matter input. Moreover, SWJ oil group 3 (Kromong, Ciseti, and Bojongmangu oils) is inferred to be generated from a dominant marine organism input with low terrestrial influence. Their correlating rock unit is the Batuasih Formation. The rock lithofacies suggest an environment ranging from shallow marine/deltaic to deep marine setting. Their paleontological analysis yielded the age ranging from Middle Eocene to Early Oligocene. The SWJ Basin is recommended to be formed as a flexural basin initiated from the Middle Eocene, while their neighbouring producing basin (the Northwest Java/NWJ Basin) was formed later in the Early Oligocene as a back-arc extension basin. Besides differences in basin forming type, timing of initiation, and basin filling, the SWJ and NWJ Basins are also distinct in their oil characteristic. The SWJ oil is sourced dominantly by higher terrestrial plants and marine phytoplankton, while the NWJ oil is generated from mixed sources, mainly lacustrine organic input.