Geochemical characteristics and hydrocarbon generation potential of Lucaogou Formation source rocks in Fukang Sag, Junggar Basin

As the largest hydrocarbon-rich sag in the Junggar Basin, the limited research on geochemical characteristics, sedimentary environment and bio-precursors of source rocks in the Fukang Sag has seriously restricted the understanding of the poor proven oil and gas resources in the sag. A combined geological and geochemical analysis on the Lucaogou Formation source rocks in the Fukang Sag was conducted based on the experimental analysis results of the newly drilled source rock samples on the Fudong Slope. The results show that the Lucaogou Formation source rocks in the Fukang Sag generally belong to source rocks of medium to very good quality, with organic matter of type Ⅱ to type Ⅲ, and mainly in the thermal maturity of early mature to mature stage. Biomarker characteristics show that the organic matter of Lucaogou Formation source rocks in the Fukang Sag is a mixture of terrestrial higher plants and aquatic algae and bacteria and maybe some Dunaliella-like green algae, which is generally deposited in the anoxic to oxic, fresh to brackish, intermittent stratified water environment, showing obvious mudstone sedimentary characteristics. The geochemical characteristics of the Lucaogou Formation source rocks in the Fukang Sag vary greatly on the plane, among which, the central and northern subsags show great hydrocarbon generation potential.