Fault Zone Structure And Reservoir Control Of Lower Paleozoic Carbonate Buried Hill In The Jiyang Depression

The buried hill of Lower Paleozoic in the Jiyang depression has developed multi-stage faults,which mainly developed in carbonate stratum.These faults are strongly affected by the later structural and diagenetic transformation,resulting in the complex distribution of structure and physical properties,thus affecting its role in hydrocarbon accumulation.In order to reveal the structural characteristics,physical property distribution,evolution of carbonate fault zone and clarify its role in hydrocarbon accumulation,field outcrop,core observation,well logging identification,physical property analysis,and reservoir dissection has been carried out.in this paper.Through this,the types and controlling factors of fault zone structure in the study area has been clarify,the evolution model of fault zone physical property structure has been established,the influence of fault zone structure on hydrocarb on migration and accumulation has been found out,and the reservoir forming model has been set up.According to the results of outcrop,core observation and logging identification,there are structural units such as breccia zone,fault zone and fault zone in the study area of lower Paleozoic carbonate buried hill fault zone.However,the development integrity and combination of different fault structural units are different.According to these,the buried hill fault zone in the study area can be divided into three structural modes: one element,two element and three element.Through the comparative analysis of fault zone structures under different lithology,it is revealed the controlling factors of fault structural zone: the larger the fault scale is,the greater the fracture degree is and the more complete the structural units are.Breccia belts are more easily developed in compressional and strike-slip fault zones,while breccia belts are often missing in warping fault zones.All three structural units develop in extensional fault zones.Compared with limestone and dolomite strata,breccia belts are more easily developed in mudstone stratum.According to the fault development process,the fault development process can be divided into three stages: development stage,youth stage and mature stage.Due to the influence of fault development stage,lithology,diagenesis and later transformation,the physical property distribution of carbonate fault zone has a strong nonuniformity.The breccia zone has high porosity and permeability,the fracture zone has low porosity and permeability,and the broken zone is between them.The physical properties of fracture zone and fracture zone increase first and then decrease with the process of fault evolution controlled by cementation.The physical properties of breccia belt vary greatly.It is mainly affected by the location of cementation,and the fluid is cemented preferentially on the fracture surface,resulting in significant difference in permeability between longitudinal and transverse directions.The physical property of fault zone structure and evolution control the hydrocarbon migration and accumulation characteristics of buried hill.According to the source-fault relationship and the mode of hydrocarbon migration and accumulation,the hydrocarbon migration and accumulation in the study area can be divided into three models.The first is“transverse migration and accumulation mode”,whose oil and gas across the fault zone,such as Chengbei 244 reservoir.The second is “strike migration and accumulation mode”,whose oil and gas along the fault zone,such as Chengbei 30 reservoir.The third is "composite migration and accumulation model" formed by horizontal and vertical combination,such as Chegu 20 reservoir.