Tertiary inversion tectonics and petroleum systems in West Natuna Sea Basins, Indonesia

摘要

The West Natuna Sea Basins are the Tertiary, inverted, intra-continental rift-basins in the Sunda Shelf, Northern Indonesia. The basins include remarkable oil procucers as well as most other Indonesian Tertiary basins. Inversion-anticlinal traps in the basin have been classic examples of a positive contribution of invewrsion tectonics to formation of petroleum syst ems and plays. The Tertiary mega-sequence of the basin includes a Middle to Upper Eocene lacustrine deposit, and Oligocene fluvial to deltaic deposit, an Early Miocene muddy facies deposit, a Middle Miocene deposit of sand-dominant deposit, and a Late Miocene through Recent alternative mud-sand deposit. The West Natuna Sea Stratigraphy remarkably lacks the thick Early to Middle, Miocene carbonates that are normay well-developedi n he most Indonesian Tertiary basins. The Oligocene and Lower Miocene sandstones are productive reservoirs, and widely deposited Oligocene and Lower Miocene mudstones provide regional and top seals, for petroleum systems in the basins. Four petroleum systems are identifiedi n the southern West Natuna Sea based on the magnitudes of inversion tectonics and resulting thermal "kitchen"that developed. Systems(1)and (2)are based on petroleum-charging kitchens, such as the Malay Basin or the Bawal Graben.These kitchens are distinguished from each othery by carbon stable isotope ratios of alkanes and aromatics of crude oils and by a biomarker. Systems A and B are y tectonic styles related to petroleum accumulations, such as basement highs or inversin anticlines. The four petroleum system are recognized from west to east and north to south in the area; such as System(1)A (Belida oil field), System(1)B (Temang, Buntal and Bintang Laut gas pools), System(2)B(Forel oil pool, Belanak oil and gas field)and System(2)A(Udang oil field). System(1)forms such larger petroleum-accumulations than System(2). Szies of the accumulations are clearly related to the size of kitchens that charged the accumulations.