Mesozoic Inversion Structure Analys Is Of The Southern Junggar Basin And Hydrocarbon Accumulation

Mesozoic evolution of the southern margin of Junggar Basin is the key to recognize continental collision in Late Paleozoic and mountain-basin coupling in Late Cenozoic. Mesozoic is important source rocks and reservoir of Petroliferous basins in Xinjiang, so studying the structure and evolution history of the southern margin of Junggar Basin plays an important role in hydrocarbon exploration and development in northwestern China.The dynamic of the first-order fold-thrust belts were modeled by the combination of the numerical modeling and balanced cross-section techniques, with the constraints from the outcrop, well drilling and logging data. Moreover,71 seismic profiles collected from southern margin of Junggar Basin were analyzed with the fault-related fold theory. The results indicate that the Junggar Basin showing extensional tectonics with the development of the Kalazha and Changji normal faults from the Middle Triassic to Middle Jurassic. This tectonic frame was in charge of the sedimentary characteristics; The change of the stress field from the extension to compression occurred in the Late Jurassic. As a result of this change, normal faults developed earlier reversed to reverse fault (North Qigu fault) and controlled the initial development of the first-order anticlines. Meanwhile, the initial form of the Qigu and Changji anticlines developed; The Qigu, Changji and Kalazha anticlines finally shaped with the strong compression in Late Cenozoic.The hydrocarbon-generation of Permian source rocks happened in Early Jurassic, and the peak of oil generation happened in Middle Jurassic, associated with the formation of the Mesozoic extensional tectonics; The hydrocarbon-generation of Lower Jurassic source rocks began in Early Cretaceous, and entered the peak of oil generation in Middle Cretaceous. The positive inversion structure formed in late Jurassic-early Cretaceous, provided a good trap for hydrocarbon generated later. Therefore research in southern Junggar Basin inversion structure has great understanding of hydrocarbon accumulation in this area.