Relationship Between Petroleum Accumulation of Mesozoic and Tectonic Movement in Ordos Basin

Key words: 
• Ordos Basin /
• IndoChina movement

Abstract: Ordos Basin is the famous petroliferous basin of Mesozoic in China. Yanchang Formation of Upper Triassic and Yan'an Formation of Jurassic are the main oilbearing strata. The oilbearing strata got through IndoChina movement, Yanshanian movement and Himalayan movement. Based on the analyses of the tectonic stress field of Mesozoic and Cenozoic and the research of the tectonic heat events, combined with fracture property, fracture azimuth and characteristic of inclusion in fracture, the relationship between the petroleum accumulation of Mesozoic and tectonic movement was discussed. It is suggested that EW, NNE and NE striking fractures were developed in the basin. Among them, the NE striking shear fractures with thin filled were developed in the SN compression environment in IndoChina period, or the NE striking fractures induced tensional fracture formed by basement fault. The EW shear striking fractures with thin filled were developed in the NWSE compression environment in Yanshanian period.The NNE tensional striking fractures with strong filled were developed in the NNWSSE extensional environment in Himalayan period. Each tectonic movements occured in Mesozoic and Cenozoic controlled the migration and accumulation of the petroleum.Because of the IndoChina movement, Ordos Basin deposited the important hydrocarbon source rock in Mesozoic. The hydrocarbon source rock reached the peak of hydrocarbon generation and expulsion because of the tectonic heat event which was producted by Yanshanian movement, resulting in the petroleum accumulation during Yanshanian period. The petroleum undergone largescale migration and adjustment because of the Himalayan movement led to the petroleum distribution of upper Mesozoic consistent with the trend of basement fracture belt. These three Mesozoic and Cenozoic tectonic movements have signicantly influenced the development of Ordos Basin and hydrocarbon accumulation within it. 