Geochemical Characteristics and Sedimentary Environment Analysis of Cretaceous Source Rocks in Central and Southwestern Junggar Basin

Recently,from the exploration results in southern Junggar Basin,the partial crude oil is derived from the Cretaceous source rocks,which has extensive generation hydrocarbon potential.Based on the former research,the distribution,hydrocarbon potential and sedimentary environment of Cretaceous source rocks have been investigated.The results indicate that the Cretaceous source rock is characterized by extensive distribution,large thickness with the maximum thickness of 500 m.However,the Cretaceous source rocks have strong heterogeneity and the distribution of hydrocarbon generation area was focused on the east and west sides of the fault belts from western Sikeshu Depression to Shawan Depression.In research area,the hydrocarbon generation potential varied for high heterogeneity,but also there has high quality source rocks with the content of TOC more than 1.0% and the(S1+S2) more than 2 mg/g.The kerogen type is Ⅱ2 and Ⅲ and hydrocarbon components include sporophyte,cutinite and exinite.Actually,the geochemical characteristics of the Cretaceous source rocks between Sikeshu Depression and Changji Depression is similar.During the Cretaceous sedimentation,the climate was dry and the sedimentary centre was in southern Shawan Depression.The sedimentary facies were shore shallow lake and partial area developed semi-deep lacustrine.Therefore,the source rocks were formed in the weak reduction-reduction environment with algae,other lower aquatic organisms and lacustrine high plants.