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In the brackish water sedimentary environment of the Junggar Basin in Xinjiang, the organic-rich shale and shale oil formation with relatively low maturity, is characterized by relatively high abundance of C 28 regular steranes. However, the biogenic source of organic matter and favorable sedimentary environment for the type of source rock has been thoroughly classified. In this paper, organic geochemical and petrological, analyses of the Lucaogou Formation shale in the Jimusaer Sag, Junggar Basin in the north of Xinjiang Uygur Autonomy Region were carried out. The source rocks in the Lucaogou Formation are mainly composed of two types of maceral including lamalginite (cyanobacteria) and telalginite (green algae), with the former predominantly fueling the high C 28 regular sterane content. Petrological, organic and inorganic geochemical analyses suggest that the lamalginite was developed in low-salinity water while the telalginite was developed in high-salinity water. Based on geochemical and organic petrological characteristics, both the lamalginite and telalginite have good hydrocarbon-generating potential, but in the lower thermal evolution stage of the Lucaogou Formation source rock, telalginite have higher hydrocarbon-generating rate. • Lamalginite (cyanobacteria) is the primary source of C 28 regular steranes. • The lamalginite (cyanobacteria) is more developed when the salinity is low and the telalginite (green algae) is more developed when the salinity is high. • In the lower thermal evolution stage of the Lucaogou Formation source rock, the lamalginite (cyanobacteria) has lower hydrocarbon-generating rate than the telalginite (green algae). [ABSTRACT FROM AUTHOR]

Due to the similarity of the biomarker characteristics of the source rocks of different layers, the progress of the oil source research of the Yanchang Formation in the Ordos Basin is difficult and slow, which highlights the shortcomings of traditional research methods. Given this, this paper uses the gas chromatography-mass spectrometry analysis results of a large volume of samples of the Yanchang Formation in the basin as the dataset, and performs an exploratory application of the factor analysis (FA, a multivariate statistical method) to analyze the molecular geochemical characteristics of organic matter, with an aim to find features that have not been noticed in the past, and give a reasonable explanation for the oil source. The findings are summarized as below: with the help of multivariate (31 molecular geochemical parameters are introduced), FA can quantify many geochemical properties of samples well, which brings convenience to research. Based on the results, it was found that parameters such as C 26 TT/C 25 TT, sterane/hopane, and ΣC 19-26 TT/C 30 αβ can effectively distinguish the samples of different areas and layers, and it is further believed that the Chang 9 source rock has higher contributions to adjacent layers (mainly the Chang 8–Chang 10 oil groups) in areas where it is abundant (mainly the Wuqi-Zhidan area), while in the other areas and layers, oil is mostly attributed to the Chang 7 source rock. •Conventional oil-source research methods are inadequate when facing the Yanchang Fm. of Ordos Basin. •Exploratively combine factor analysis methods to analyze a large amount of GC-MS data. •Factor analysis effectively reveals differences in petroleum geochemistry among different source rocks. • This research has the potential value of promoting the development of petroleum geochemistry technology. [ABSTRACT FROM AUTHOR]