The Fault Characterisation And Sealing Capacity Evalution In The Western Dongying Sag

In this thesis,by integrating well logging and seismic data,we carried on a systematic study on the characteristics and sealing capacity of the faults in the western Dongying sag.Applying the geophysics,the structural geology,the petroleum geology and other related theories and methods.There are a number of faults developed in the western Dongying sag.In plain view,based on primary and secondary faults,it derived a lot of tertiary and four-stage faults.These faults at different scales present different distribution patterns,e.g.,parallel type,oblique type,and echelon type.In section view,these faults present multiple combinations,such as"Y"type,horst.We divided the structure of the fault zone in western Dongying sag based on seismic data interpretation,well logging data analysis and core samples observation.In 3D space,a fault zone can be divided into induced fault core and damage zone.The structural evolution analysis shows that the primary faults began to form in the late Mesozoic,controlling the whole framework of the western Dongying sedimentation,while the secondary and tertiary faults were active in early Cenozoic.Fault zone with different sizes controlled the sedimentation in western Dongying formation.A fault can be either a barrier for oil and gas migration if it seals or a path for oil and gas migration if it does not.Thus,it is very important to investigate the fault sealing capacity on hydrocarbon migration and accumulation.In this research,based on the detailed interpretation of seismic data,we quantitatively evaluated the sealing capacity of fault zone by using multiple parameters,e.g.,Shale Gouge Ratio?SGR?,mud content?Rm?,fault tightness index(I_FT)and the section normal stress.We systematically analyzed the sealing capacity of the primary fault?Shicun fault?,the secondary faults?Shengbei fault,Lijin fault,Boxing fault,Fanjia fault,Jinjia fault?and the tertiary fault?Zhengnan fault?in the western Dongying sag.Every individual fault was evaluated regarding to its relative position respectively.Based on the core observation and microscope observation,the sealing capacity of the damage zone was also analyzed.The study suggested that the western Dongying sag presents various sealing capacity.Generally,the northern steep slope presents better fault sealing capacity than the south gentle slope.The poor fault sealing capacity of the south gentle slope enables the hydrocarbon to migrate from the Boxing sub-sag to Jinjia structure and so on.