Research On Structural Characteristics Of Cretaceous-Paleogene In Fangzheng Fault Depression

Using previous research results as the basis, guiding with the new geological theory of sequence stratigraphy and strutural geology, combing the new theories such as structural geology, sedimentary petrography and seismic stratigraphy, this paper analyses the stratigraphic sequence and tectonic evolution thoroughly of the research area by the method of seismic, logging , drilling and core analysis comprehensively.Fangzheng fault depression is a North-East double-faulted trough fault which was two deep faults F₁,F₂ to control. The master fault goes the same direct with north-east structure in the area. The faulted structure area which composed of fault depression frame include the south slope, the south depression, the central bulge, the north depression area and north slope.in order to study the construction characters of Fangzheng rift T1-T3 reflecting layer in Yishu graben. We took the syntheical seismic records to demarcate the layer of earthquake in the study area, sum up their reverberation characters and explained the layer and fault in this area. Correlative softwares are used to work out construction pictures of T1-T5 reverberation layer, and analyze their. It has great significance for realizing the construction characters of Fangzheng rift T1-T5 reflecting layer in Yishu graben. It shows that the main faults(F₁,F₂,F₃) all go along with the axis of the fault.They all break from the layer T5 to the layer T1 and control the formation and the development and there are many subsidiary faults in every reflective layer. The main type of fracture are tensional fault,compressional fault and strike slip fault. The bounary major faults controlled the distribution of source rocks; major faults controlled the formation and distribution of traps; the faults which disrupted or near the source rocks provided good passage forpetroleum migration; sealed faults acted as the favorable shelter to petroleum accumulations.Do reserch on the profile of the history of tectonic development which is made on the basis of the sequence of faults' forming, Fangzheng fault depression experienced pre-fault depression, developmental stages of fault depression and late fault depression. The structural and sedimentary evolution experienced 6 phases: Mesozoic fault depression phase,Cenozoic strong fault depression phase, continuing fault depression phase,fault-depression transformation phase, fault depression suppression phase and fault depression subduction phase.Through the systematic research of Fangzheng fault depression, deepening the structural characteristics of the fracture zones, construction and development of understanding, to deepen the Fangzheng fault depression of the Petroleum Geology of understanding,enabling optimization of oil and gas zone,ready to break the conditions for exploration.