Romania's Petroleum Systems

Abstract

In Romania, nine onshore petroleum systems and one offshore petroleum system have recently been identified. Of the onshore systems, three are related to the compressional folded basins: Teleajen-Sita (early Middle Cretaceous marine source rocks), and Puciossa-Fusaru and Alunis-Kliwa (Oligocene-early Miocene marine source rocks). In the same category, we have included the recently discovered Deleni petroleum system with source rocks of not yet identified origin but whose reservoirs certainly belong to a folded basin. In the foreland platform basins, two systems can be distinguished: Rimesti-Fauresti (Middle Jurassic marine source rocks) and Infra-Anhydrite (with presumed Middle Jurassic or middle Miocene marine source rocks). The areas corresponding to the posttectonic basins include three onshore petroleum systems and one offshore system: the Pannonian (Badenian marine and Sarmatian brackish water source rocks), the Valea Caselor-Borsa (oligocene marine source rocks) and the Transylvanian (Badenian marine shales source and Sarmatian brackish water source rocks). Offshore, there is only one petroleum system consisting of Oligocene-Miocene marine source rock and Cretaceous or Eocene reservoirs. The majority of the mentioned petroleum systems reservoirs are Paleozoic to Pliocene clastics, but in the platform areas, carbonate reservoirs are found in the Paleozoic and Mesozoic. In all the petroleum systems, despite the differentmore » ages of the source rocks, most of the hydrocarbons have been expelled relatively recently during the Late Sarmatian-Pliocene interval. This face is substantiated by examples from two petroleum systems: the Rimesti-Fauresti (duration time 173 m.y., preservation 2 m.y.) and the Alunis-Kliwa (duration time 29-30 m.y., preservation 4 m.y.). The hydrocarbons were first expelled and migrated into described systems reservoirs after Late Styrian and Moldavian overthrusting, i.e. not earlier than 12-14 m.y.« less