Identification and distribution of marine hydrocarbon source rocks in the Ordovician and Cambrian of the Tarim Basin

A process for identifying marine hydrocarbon source rocks is established based on outcrop measurement, ground-penetrating radar survey, core analysis, logging evaluation, seismic interpretation, etc. It is used to identify the Cambrian and Ordovician marine hydrocarbon source rocks and to predict their spatial distribution in the Tarim Basin. Four suites of marine hydrocarbon source rocks are identified in the Tarim Basin, and they are distributed, respectively, in the Lower-Middle Cambrian of the Awati and Manjiaer sags, the Heituao Formation of the Lower-Middle Ordovician in the Tadong region, the Saergan-Tumuxiuke-Queerqueke formations of the Middle-Upper Ordovician from the Awati Sag to the Manjiaer Sag, and the Yin'gan and Lianglitage formations of the Upper Ordovician from the Awati Sag to the Tazhong area. The development of these source rocks was controlled by the sea level rise and they are characterized by different facies in the same stage, namely, different source rocks are deposited in sedimentary facies zones at the same stage. The formation of the source rocks shifted with the carbonate basin and was interrupted when there are large quantities of siliciclastic influx.