Contrast And Research Of Petroleum Geological Characteristics: West And East Natuna Basin

This target area, West and East Natuna Basins, located in the northwest sea of Indonesia the central east region of Southeast Asia where possesses very complicated tectonic characters. Oil generation occurred mainly in Tertiary. This paper, using the basic geology, petroleum geology and hydrocarbon accumulation analysis as the main line, makes some analysis and comparison about basic geologic features of these two basins. The author also researches the characters of petroleum geology, summarizes reservoir-foming rule and hydrocarbon pooling condition, predicts the advantaged areas.Due to the interaction of the bulk of the Indian plate and Eurasian plate, these two basins have experienced the same Rift, Post-Rift, Inversion and Quietnees of the four stages. Compared with the East Natuna Basin, the West Natuna Basin has a stronger tectonic movement, and the faults are well developed, forms numerous grabens and horsts. Thanks to the shelter of Natuna Arch, the East Natuna Basin tectonic activity is weak, fault developed less.Basin structure control the distribution of formation:Onset of rifting in the West Natuna Basin was caused by extensional movements beginning in the Late Eocene, earlier than the rift happened in the East Natuna Basin. In mid Early Miocene a period of regional compression and uplift started in the West Natuna Basin that was to give rise to the pervasive northeast to southwest trending anticlines and uplifts and the basin rised to be eroded leding to the lose of Terumbu. The uplift of East Natuna Basin occurred in mid Miocene. The western part of West Natuna Basin is eroded and the eastern part only shallowed creating the depositon of a thick carbonate platform and reefs. To the late Miocene, the tectonic activity in West and East Natuna Basins weakened overall settlement, in the quiet period of tectonic activity the two basins are deposited thick marine shale.The hydrocarbon accumulation in West Natuna Basin was significantly affected by structural control. The main source rock is lacustrine mudstone of Belut, the main reservoir is sandstone layer of Gabus which is sealed by the Barat shale as a regional seal. Types of traps are mainly structural traps. In East Natuna Basin, Source rock is the coal of late-rift deposition Arang, carbonate rock of the Terumbu as the reservoir, overlying Muda shale as a regional seal, reservoir types are mainly lithologic reservoirs.In West Natuna Basin, favorable exploration area located in the Bawal Graben. In East Natuna Basin, The reef is the most potential exploration area.