Publications

The East Java Basin is one of the most productive oil basins in Indonesia, having been explored and produced for more than one hundred years. However, firm studies on geochemical correlation between oils and their sources have been scarcely conducted. Therefore, we hereby present such a study, with the research area of the Mudi and Sukowati oil fields and some deep wells (Ngimbang-1 and Kujung-1 Wells) penetrating expected sources (Ngimbang, Kujung, Tuban, Wonocolo, Ngrayong formations). Families of the oils are determined through biomarker analysis by pattern matching and finger printing of GC and GC-MS, also carbon-13 isotope characterization. Rock samples of the wells are also geochemically characterized to correlate with the oils, and finally their organic richnesses and maturities are evaluated. Our study shows that oils from Mudi and Sukowati fields came from one family of oil with source facies of deltaic to marginal marine. The oils are positively correlative to the Lower Ngimbang shales, Eocene in age. The oil and rock samples show that the organic materials are mixing between deltaic (vitrinite macerals type III) to marginal marine (liptinite and alganite macerals type II). The source richness is fair to excellent, with top of oil windows (Ro 0.6) variably between 1900 and 2850 meters in depth. Knowing better the source that generated the oils and where the source pods are within the kitchen will improve the knowledge on petroleum generation, migration and charging. This study composes the elements to obtain such knowledge. Geochemistry improves petroleum exploration efficiency.