冀中坳陷东部地区构造格架及其形成与发展

冀中坳陷第三纪以来经历了多期构造括动,对应于沉积期反映为坳陷的扩展并形成右旋构造,对应于不整合期反映为坳陷的收缩并形成左旋扭压构造。在东部断裂发育区,除形成潜山及其披覆构造外,在断裂的下降盘常形成既具有左旋和右旋、又具有垂直升降和水平挤压特征的牵引构造。在沉积凹陷中也发育兼具张性和压性特征的构造。这些构造的叠加,就形成了有利生油区附近不同层系的各种含油构造在投影平面上的叠加连片。

THE STRUCTURAL FRAMEWORK OF EASTERN JIZHONG DEPRESSION AND ITS EVOLUTION

The main oil-generation region of Jizhong depression,including Gu'an,Baxian,Raoyang,Shenxian and Shulu sags,was a unified oil-generation depression during the Eocene and Early-Middle Oliocene.The basement rocks of the depression were cut into a series of rhombic or semi-rhombic fault blocks with uplifts and depressions by fractures due to multi-tectonic movements.These fractures are normal faults in profiles,but have echelon arrangement,shear displacement,branching fractures and dragging structures on the horizantal plane,showing that most of the faults were formed by shearing stress.This is further proved by anticlines,synclines and even the echelon arrangement of higher-order structures.The compressive structurt in the present area are complicated by tensil or tensil-shearing fractures.This kind of geological phenomena suggests that these structures are characterized by both directions of clockwise and anti-clockwise and compresive and shearing mechanical properties.The study on the history of tectonic development indicates that the extention of the depression took place during the deposition period,thus formed mid-small dextal structures;the contraction of the depression occurred in the discordant period,and formed sinistral structures.This kind of sinistral and dextral shearings have happend alternatively for many times ever since the Tertiary,and finally formed a huge structural complex with buried-hill as its main body.The reversal motions led to multi-migration,extenct distribution and the best enrichment of hydrocarbon.