GEOLOGICAL REVIEW TO IDENTIFY PETROLEUM SYSTEM IN PATI BASIN

摘要

Pati Basin is a part of basinal low of Muria Trough. The Muria Trough separated with a basinal low of TubanCamar trough which belongs to North East Java Basin to the southeast by Bawean Arch. The southeastern part of Pati Basin controlled by a NE-SW oriented of couple fault. The faults are left lateral slip faults with a down-throwing displacement directed to the northwest. These faults are also acted as tectonic contact between the Pati Basin and the Bawean Arch. The basin is classified in a halfgraben structure, with its north-northwest part as hanging wall. Due to this basin has interesting structure therefore its influence the petroleum system. In this basin,Kujung FormationUnit II and the "CD" Formation are potential source rocks to generate hydrocarbon. The Kujung Unit II consists of lagoonalfacies of claystone. The "CD" Formation consists of open lacustrine sediments of claystone and limestone. Based on Dini-1 Well, Kujung Formation Unit II has TOC= of 0.96-2.84 wt% (good to very good organic content), HI: 67-212 (type II&III) and Tmax 416-424 °C. These hydrocarbons are believed to have migrated within the structure such as the fault and halfgraben structure thus been trapped in the Kujung Unit I Formation, Carbonate of Kujung Unit III Formation and fan-deltaic sands of the Intra "CD" Formation of the Awal-1 Well. Regional Seal is claystone of "GL" Formation and intraformational seal is claystone layers within all formations. Next is trapping, stratigraphic traps are Eocene-early Oligocene fault scrap fan of conglomerate and subaqueous fan delta of sandstone, Early Late Miocene shallow marine reefal limestone of Kujung Unit I and Middle Late Miocene deltaic facies of sandstone lenses of the Upper "OK" Formation and structural traps refers to NE-SW trending tilted fault block of the Eocene-Early Oligocene fault system along the basin margin.