The analysis of the petroleum systems and exploration prospects in the West Natuna Basin in the South China Sea

The West Natuna Basin is an important petroliferous basin in the South China Sea. The division, distribution, controlling factors and exploration prospects of the major petroleum systems in the Basin are based on the tectonic-sedimentary evolution guided by the thought " from source to trap" in the study of petroleum systems. Four sets of petroleum systems are recognized, including the Belut-Gabus/Arang/Belut (·), K/J-Arang (·), Arang-Arang (!), and Penyu-Penyu (·) petroleum systems. The Belut-Gabus/Arang/Belut (·) and K/J-Arang (·) petroleum systems as the economically important petroleum systems in the West Natuna Basin make up of 46.1% and 45.0% of extractable oil and gas reserves. Regionally, the discovered oil and gas resources reside dominantly in the Anambas garben and the eastern part of the Penyu subbasin. Stratigraphically, they are largely reserved in the upper Oligocene and the lower Miocene strata, and structurally, generally trapped in the compressional anticlines and trap structures. The oil and gas distribution is largely controlled by effective source rocks, favourable regional cap rocks and migration pathways, compressional inversion and basement uplifting. It follows that the Penyu-Penyu (·) petroleum system has the great exploration potential, and the emphasis will be on the evaluation of the reservoir rocks and identification of favourable oil and gas migration pathways in this petroleum system in the depression.