A Study On Structural Characteristics Of Complicated Buried Hill Of The Eastern Yihezhuang Uplift And Its Formation And Evolution

The Yihezhuang Uplift is a large-scale positive structural unit that separates the Chezhen Sag and the Zhanhua Sag,located in the northwestern part of the Jiyang Depression in the Bohai Bay Basin.Faults in the uplift are well developed and undergo multiple periods of structural movement,which makes the study area exhibit complex structural features and difficult to make a further exploration.This paper aims to analyze the structural characteristics and the evolution,and based on this,concludes the hydrocarbon accumulation regularity.In this study,high-resolution 3D seismic data,drilling and logging data are combined,to elucidate the structrural characteristics,to investigate the tectonic evolution of the Yidong Uplift,and to estimate the regularity of hydrocarbon accumulation.This study classify the buried hills in the Yidong Area according to the structural characteristics and evolution history,and finally construct the hydrocarbon accumulation pattern in the Yidong Area.The Yihezhuang Uplift experienced five strucutral movements,which are Caledonian,Haixi,Indosinian,Yanshan,and Himalayan,and formed present complex structural form.Faults in the study area can be divided into three groups: which trend NW-SE,NE-SW,and N-S,respectively.Five major faults control regional structural features.Based on the fault scale and its control of the structure and deposition,four grades of faults are identified in the Yidong Area.Furthermore,the structured types of buried hill in the Yidong area are devided into three categories and seven subcategories.The Yidong area experienced five stages of evolution: stability,extrusion,reversal,rift and depression.Structural reversal and gravity sliding control the formation of the Yidong Fault Trough.According to the evolutionary his-tory,buried hills are divided into five types,which the “early buried-late finalized-stepped” buried hill isproved to be the best type of hydrocarbon enrichment.Hydrocarbon reservoir could be found in both old and new strata in this area.Several sags near the uplift supply oil to the Yihezhuang Uplift.There are nine types of buried hill reservoirs,seven of them are related to faults,indicating that the faults have dominant control over the reservoirs.The poorly sealed intervals of faults and multi-phase unconformity provide pathway of hydrocarbon migration.Based on this,we establish five models of hydrocarbon accumulation combining with the study of hydrocarbon reservoiring dynamics.