Structural Characteristics And Its Relationship To Hydrocarbon Enrichment In The South Of Zhanhua Concave

The south Zhanhua Sag is one of the most enriched areas in the Jiyang Depression of the Bohai Bay Basin.However,its geological conditions are complex.In particular,the relationship between structural characteristics and oil-gas accumulation is not clear,which limits the cognition of oil-gas accumulation rules and oil and gas further exploration.This article combined with integrated regional geology,seismic,drilling and other exploration information,using balanced cross section,structural analysis,accumulation analysis and onther research methods and techniques,analyzing the geological structure and structural characteristics of the study area and its relationship with oil and gas accumulation and raising exploration suggests.The tectonic units in the study area can be divided into three types.The structure of the Cenozoic faulted depression basin is mainly composed of the complicated half graben of "faulted in the north part and overlapped in the south part".The multi-phase tectonism of the Mesozoic Era laid the basic framework of the main structures in the area.The Indosinian Movement formed a Guxi reverse fault zone of the northwest trending and Kendong and Gudong a strike-slip and compression fault zone of the north-east-north trending.It is typical of compressional trust movement are developed under Kendong and Gudong faults in the periods of early Yanshan movement.During the later Yanshanian,it developed rift sag,Guxi fault changed from reverse to normal fault because of negative inversion.Kendong and Gudong faults became extentional faults.Meantime,the movement formed NEE Kenxi-Guxi and Kenli normal fault zone.The structure styles of the Cenozoic fault are mainly extensional structure styles,strike-slip tectonic styles,extension-sliding tectonic styles and inversion tectonic styles.Cenozonic tectonic activities of major fault zones in the area are characteristic of higer intensity in the north and inferior intensity in the south,higer intensity in the east and inferior intensity in the west in space,of strongest activity during the fourth-second member of Shahejie formation,lower activity from the first member of Shahejie formation to Dongying formation in Paleogene,weaker activity during Neogene in time.The source rock of Shasan Group intervalin Gunan concave came into Hydrocarbon generation period in late time of Dongying layer and the source rock of Shayi Group came into Hydrocarbon generation period in late time of Guantao layer.From the middle to the Quaternary period of Minghuazhen Formation,the source rock of Shasan and Shayi Group turn into main Hydrocarbon generation period.Tectonic evolution,formation period of traps and main period of hydrocarbon generation and expulsioand has a good time-space matching relation.The study region has two oil and gas accumulation pattern: “accumulation-fault transforming in the outside source” and “accumulation-high pressure filling in the inside of source”.The next exploration in south Gunan sag has two main directions : In the periphery of fault belt of atmospheric area in the outside s2-2ource,these faults communicate directly with oil sources.The trap and area of these fault is beneficial reservoir formation area;High pressure area of inside of source is development area of lithologic concealed oil and gas reservoir and it is the potential area of oil and gas exploration in this place.