Abstract:

Nam Con Son basin located in offshore Vietnam is a rifting basin with a large amount of sediment. The largest thickness reaches over 12,000m in which the Oligocene sediment makes up over 5,000m in the Central Trough. The results of geochemical analyses show that Oligocene sediment has good to very good organic matter richness and generation potential. At the present time, this sediment has been already in wet gas & condensate to dry gas phase. However, the analyzed samples just represented the upper Oligocene sediment, therefore, study on properties of discovered crude oil helps to predict the characteristics as well as potential of source rocks including Lower Oligocene one. The geological complex structures and paleo-depositional environments here led to complicated relationship between oil-source rocks. The advanced geochemical analyses namely gas chromatography (GC) and gas chromatography mass spectrometry (GCMS) provide the biomarkers that are very reliable to demonstrate the oil to sources correlation. The discovered oils have been divided into 2 main families: oil related to source rocks containing terrestrial organic matter (fluvial-deltaic environment) and oil related to lacustrine source rocks. These results help to prove the existence as well as the role of two Oligocene source rock systems in supplying hydrocarbons for prospects in Nam Con Son basin.