Geochemistry of source rocks in the lower Tertiary Nadu Formation, Eastern Depression of the Baise Basin, Guangxi Province, China

Based on the results of geochemical and organic petrological analyses, generally, the Eocene mudstones from the Upper Na 1 sub-member of Bai 38 Well in the eastern part of the Baise Basin can be classified into three categories such as poor, fair and good source rocks, with type II/III or III kerogen. Na 2 member mudstones recovered from Bai 66 Well in the same area of the Basin can be classified generally as fair to good source rocks, with kerogens of type II/III and subordinately type II and type I. However, optical observation of the samples analyzed reveals that organic matter is mostly composed of algal and amorphous materials. Level of thermal maturation of organic matter from the Upper Na 1 sub-member shows early mature stage of main oil generation zone, and maturity of organic matter in the Eocene Na 2 member mudstones reached the middle stage of oil generation zone. But, the level of maturation for the organic matter of samples from both wells does not reach the peak mature zone with respect to petroleum generation.