CHARACTER AND PETROLEUM GEOLOGICAL SIGNIFICANCE OF SEISMITES IN THE QINGSHANKOU FORMATION OF CRETACEOUS IN SONGLIAO BASIN

By observation of a large number of cores,combined with the study on tectonic setting in Songliao Basin,Cretaceous Qingshankou seismite is identified.On the basis of previous studies,seismite deformation structures are divided into two categories,consolidation stratigraphic seismite deformation structure and non-consolidation stratigraphic seismite deformation structure.Consolidation stratigraphic seismite deformation structures in the study area are mainly cracks,micro-faults,crack-type formation fracture zone,and intraclastic parabreccia,non-consolidation stratigraphic seismites deformation structures are mainly liquified sandstone veins,boudin structure,syn-sedimentary plastic deformation,loop bedding,pillow seismites and associated structures and so on.The sedimentary characteristics of seismites are summarized and petroleum geological significance are discussed:the collapse fluxoturbidite rocks sandbody triggered by earthquake activity from the delta front,shore-shallow lake dam from high-energy wave zone triggered by earthquake activity are both good reservoir;dissolution porosity and micro-cracks is developed in the vicinity of cracks.Development degree of micro-cracks and dissolution porosity will no doubt improve the performance of the reservoir constructively;fault system in consolidation earthquake stratum provides access for oil and gas migration.Strong earthquake activity in the dense consolidation cause the breakdown of mudstone caprock,a large number of cracks lead to rapid loss of oil and gas.