鄂尔多斯断块新生构造的继承性发育及对油气勘探的启示

Inheritance Developing of Neogenic Structures in the Ordos Fault-block and Its Inspirations for Oil-gas Exploration

分五大阶段(太古宙—古元古代、中—新元古代、早古生代、晚古生代和中—新生代)重塑了鄂尔多斯断块的构造演化,探讨了各阶段的构造—沉积格局。分析了不同方向的断裂(包括基底中的东西向和北东向断裂)在盆地发育中所起的作用,强调了中元古代出现的南北向新生构造和早奥陶世出现的北西向新生构造在断块演化和油气成藏中的重要性,并以"盆""山"耦合发育为指导探讨了这两者及东西向断裂与邻侧造山带演化间的有机联系。鄂尔多斯断块的构造稳定性在于它在中—新生代没有新生构造出现,而只有南北向构造和北西向构造的继承性活动,前者在白垩纪(—古近纪)的冲断决定了油气的保存或调整。基于这一实例分析了新生构造继承性发育的某些特点,尤其强调北西向构造在控制后期沉积格局和油气成藏中的意义,提出(海相)油气勘探中构造分析的关键是新生构造的继承性发育。

Tectonic evolution of the Ordos fault-block was reconstructed,which could be separated into five main stages,namely,Archean-Paleoproterozoic,Meso-Neoproterozoic,Early Paleozoic,Late Paleozoic and Meso-Cenozoic,and the tectono-sedimentary frameworks of each stage were explored.The roles of controlling basin development of the fractures with varied strikes,including the W-E and NE-striking fractures in the basement,were analysed,which emphasized that the neogenic structures of N-S orientation appearing in Mesoproterozoic and NW-striking forming in Early Ordovician played an important part in the fault-block＇s evolution and oil-gas accumulation.In the light of basin-orogeny coupling theory,an organic relation between the neogenic structures as well as the W-E fracture and the neighbouring orogenic occurring was discussed.The inheritance development of the N-S and NW structures in Meso-Cenozoic,instead of younger neogenic structures appearing in Meso-Cenozoic,resulted in a tectonic stability of the Ordos fault-block.The N-S fracture further developed and became a boundary fault of the block during Cretaceous-Eogene,when the thrusting controlled the oil-gas reservation or adjustment.The NW-striking neogenic structure,which was firstly put forward and systimatically described in this paper,didn＇t reactivate in Late Mesozoic and Cenozoic.Based on the example,the characteristics of neogenic structural inheritance activities were analysed,which underlined the significance of NW structure in constraining later sedimentary framework and oil-gas formation.The Ordos fault-block supported a case that the key of structural analysis for marine oil-gas exploration should be inheritance developing of neogenic structures.