The Distinguishing Of Fault Age Stage And Its Controling On Hydrocarbon Accumulation In Jiyang Depression

The age and mode of activity of faults are significant factors affecting hydrocarbon accumulation and distribution in sedimentary basins.Based on the theory of Analytical Tectonics,Sedimentology,and Petroleum Geology,considering the previous research results and geological data of drilling,well logging,seismic profiles,the age stage of the fault is distinguished and the fault mode is studied in Jiyang Depression,by using the methods of data analysis and indoor physical simulation,qualitative description and quantitative analysis.We choose the fault structure parameters,such as slip and cutting depth,depth and length,shape of the fault plane,and derivative structure,to establish the criteria of discriminating fault age.Based on the analysis of geometric and kinematic characteristics of Jiyang Depression and its faults,typical faults are selected for age discrimination,and then the relationship between the fault age and activities of faults and basin structure,sedimentary sandstone body and oil and gas distribution is discussed.According to geological characteristics of Jiyang Depression,the horizontal uniform stretch model and extensional model of flexural basement faults were established to simulate the process of fracture development.The life process of faults occurring in plane and profile,from simple to complex is presented.The evolution process of faults was simulated by discrete element model,and it was found that with the growth of fault age,the internal structure of fault zone gradually transited from fracture to local fracture,fracture penetration,sliding fracture with displacement and derived fracture.On the basis of physical and numerical simulation and the balance profile data of Dongying Depression,the relationship between fault zone structure,strata and sedimentation during the evolution of Chennan fault was analyzed..The life cycle of fracture development is divided into six stages: embryo stage,infancy stage,youth stage,maturity stage,old age stage and extinction stage.Embryo stage and infancy stage are recessive stage(the principal section is not formed),and youth stage,maturity stage,old age stage and extinct stage are dominant stage(the principal section is formed and has a displacement).The fracture structure models of different age stages are established.Via the age discrimination criteria established by multi-index comprehensive evaluation method,39 typical faults are studied.Wang Jiagang,Kendong and Gudong fault are three embryonic faults;Bamianhe,Kendong and Chengdong fault are three infancy faults.These faults are recessive faults,which are the early stage of fault development;14 youth faults such as Rossi and Guxi fault;11 maturity faults such as Shicun and Qiguang fault,4 old faults such as Ningnan and Chennan West fault;2 extinction faults such as East Chennan and Gaoqing fault.The boundary faults in the steep slope zone of Dongying sag are in old stage and extinction stage,the boundary faults in the steep slope zone of Huimin sag are in old stage,the boundary faults in the steep slope zone of Chezhen sag are in maturity stage,and the boundary faults in the steep slope zone of Zhanhua sag are in youth stage.Different parts of one fault are located at different stages.For example,the western part of Chennan fault is in old stage,and the eastern part is in extinction stage.There are obvious characteristics of one fault in different stage,such as no fault section and displacement in embryo stage;no displacement in infancy stage,discontinuous section;flat cross section in youth stage with simple fracture zone(mainly induced fracture zone);shovel section in adult stage with complex fracture zone(mainly induced fracture zone and sliding fracture zone),and derivative fracture occurs;shovel and slope flat cross section in old stage,with fault gouge and cementation o in the interior of the fault zone,and multi-level cutting in the derived structures;fault ceases to move in extinction stage,covered by horizontal strata,or reverses.Through the three indexes of fault growth index,activity rate and fault drop,the active mode of faults in Jiyang Depression is analyzed.The main active mode of faults in Jiyang Depression is attenuation,stabilization,first increasing and then declining(growth>decrease),first increasing and then declining(growth=decrease),first increasing and then declining(growth=decrease),continuous bimodal,intermittent bimodal,continuous triple-modal and intermittent.By comparing and analyzing the characteristics of fault age and mode of activity,it is considered that the mode of activity of Tensional-torsional faults affects the duration and intensity of fault age.Stable,continuous and high-intensity mode of fault activity is conducive to the development of faults towards the old age.Based on the study of the stage of fault development and the mode of fault activity in Jiyang Depression,the hydrocarbon-controlling ability,reservoir-controlling ability,sourcereservoir-cap assemblage,hydrocarbon transmission and sealing ability,reservoir-controlling type,trap and reservoir type of faults of different ages are discussed.In general,as the age of faults growing,the types of reservoir control of faults became more complex,and the types of controlled traps became more,and the size of traps became larger.Eight types of reservoir control modes are proposed in the study area.They are,(1)in the early stage of regulating reservoir control mode,the local crushing room to adjust the uneven stress mainly appeared in the adjustment zone,(2)the development of transverse anticline and lateral slope,control the formation and distribution of sedimentary sand body,oil and gas accumulation to form a regulating composite reservoir;(3)young fault-sand matching vertical migration into a reservoir model,controlled by the young fault formation of sedimentation center and sediment gravity unloading area,fault for the vertical migration channel,the formation of lithologic structural oil and gas reservoirs;(4)the young man period fault-sand matching step-type lateral migration and accumulation mode,by fault and sand body together constitute the transmission system,oil and gas first through the fault for vertical migration,and then through the fault through the sand body lateral migration,aggregation into a reservoir;(5)fault-ridge lateral migration and accumulation model in the young adulthood,the transmission system is fault,sand body and unconformity complex transmission,oil and gas migration to the sand body through the source fault,and through the sand body and unconformity along the direction of the ancient structure ridge migration to the slope zone trap;(6)fault slope control sand control reservoir model in the prime of life,in the prime of life on the fault slope developed a rich nearshore deep water turbidite fan,alluvial fan,braided river delta,along the fault slope vertically arranged trap,oil and gas accumulation in the trap;(7)hybrid reservoir control model of derived faults in the prime of life,the rolling anticline derived from the upper plate and the positive and negative faults,can provide a good structural trap,derived fault as a source of oil fault,combined with unconformity and sand body oil and gas vertical and horizontal migration,gathered into a reservoir;(8)the multi-type reservoir control mode in the old age is dominated by large rolling anticline reservoirs,the lower part of which is developed sand and gravel reservoir.There are mainly sandstone body lithologic reservoir,fault block mountain-mantle reservoir and igneous rock reservoir.