Geochemical features and geologic significances of source rocks in Nanpu Sag, Bohai Bay Basin

Fine description and comparative study of the geochemical features of source rocks in the Nanpu Sag of the Bohai Bay Basin have been made according to multiple parameters.It has been concluded that effective source rocks in the 3rd member of the Shahejie Formation are regarded as excellent effective hydrocarbon source rocks thanks to big thickness and high organic abundance(2.5%-8%).They are mainly of Ⅱ₁ and Ⅰ organic types,and are in mature and over mature stages.Effective source rocks in the 1st member of the Shahejie Formation are regarded as good ones since the organic abundance ranges from 1.2% to 2.3%,and the organic types are dominated by Ⅱ₂ and Ⅲ.Effective source rocks in the 3rd member of the Dongying Formation are regarded as relatively good ones of mature stage since the organic abundance ranges from 0.2% to 2.6%,and the organic type is dominated by Ⅱ₂.3 regions favorable for exploration in the Nanpu Sag have been pointed out.1)Structures Nanpu1-2 and 3-4 close to hydrocarbon generation sags dominated by types Ⅱ₁ and Ⅰ source rocks.2)Structures Gaoshangpu and Liuzan close to hydrocarbon generation sags dominated by types Ⅱ₂ and Ⅰ source rocks.3)Structures Laoyemiao-Beipu and Nanpu5 close to hydrocarbon generation sags dominated by types Ⅱ₂ and Ⅲ source rocks.