四川盆地新元古代构造属性及其油气地质意义

Neoproterozoic Tectonic Attributes and Their Petroleum Geological Significance in Sichuan Basin

前人利用四川盆地周缘及内部新元古代火成岩地球化学信息分析其构造背景,存在伸展和挤压两种截然不同的认识.地球物理资料显示盆地深部裂陷广布,而至陡山沱组沉积时期盆地中-西部存在明显的隆升剥蚀,两者之间的构造转换过程不清.针对这些问题,通过对四川盆地地震反射剖面构造解释,结合岩石地球化学、钻井数据与盆缘露头沉积层序分析,探索四川盆地新元古代构造演化过程与油气有利区.结果表明罗迪尼亚超大陆裂解至冈瓦纳汇聚阶段洋-陆俯冲是导致川西-川中裂谷向隆升剥蚀转化的原因,而川东新元古代中后期(820~551 Ma)始终处于构造沉降.川西-川中新元古界可能仅存在乌叶组同期的有机质岩,川中隆升区与川东沉降区之间发育碎屑岩储集体.

According to geochemical information analysis of Neoproterozoic igneous rocks in the periphery and interior of Sichuan basin,there are two completely different understandings of extension and extrusion.The geophysical data show that the deep rifting of the basin is widespread,and there are obvious uplift and denudation in the central and western parts of the basin until the deposition period of Doushantuo Formation.The tectonic transformation process between the two is unclear.To solve these problems,in this paper it explores the Neoproterozoic tectonic evolution and favorable oil and gas areas of the Sichuan basin through the interpretation of seismic reflection profiles and the analysis of petrogeochemistry,drilling data and outcrop sedimentary sequences.The results in this study show that the oceanic subduction was the cause of the rift-uplift denudation transformation in the western and central Sichuan during the period from the breakup of the Rodinia supercontinent to the convergence of the Gondwana supercontinent,while the eastern Sichuan area was always in tectonic subsidence in the middle and late Neoproterozoic(820-551 Ma).There may only be organic rocks of Wuye Formation at the same time in the Neoproterozoic of western Sichuan and central Sichuan,and clastic reservoirs are developed between the uplift area of central Sichuan and the subsidence area of eastern Sichuan.