Sequence Stratigraphy And Depositional System Research Of Paleogene In Southern Of Liaoxi Depression

Based on the theory of high resolution sequence stratigraphy and the terrestrial sequence stratigraphy models in rifted lacustrine basin,the paper aims to study the sequence architecture,the temporal and space evolution of the sedimentary systems of Paleogene,by comprehensively analyzing the seismic,drilling/logging data and the cores.And then predicted the favorable reservoir zones,after considering with oilFgas migration and congregation.Nine sequence boundary are recognized with the principles of high resolution sequence stratigraphy,including four unconformity surface and five sedimentation transformation surfaces.Paleogene is divided into 1 first-order sequence,3 second-order sequences,and 8 third-order sequence,while Es4-Kongdian formation is predicted by seimic.After building the sequence framework in the Southern of Liaoxi depression,structural maps,thickness maps and palaeogeomorphic maps are drawn in order to analyse the "source-converge-assemble" system in the Southern of Liaoxi depression,and three sedimentary centres are found located in the northern,centre and southern part,and changing significantly in different periods.In the sequence framework,eight kinds of sedimentary facies are identifyed:the fluvial-flood plain,fluvial delta,fan delta,braided delta,subaqueous fans,beach bar,Carbonate platfornand lacustrine.Combining the palaeogeomorphic characteristic with the controls of slope break on deposition,development of sedimentary facies are found to display a good inheritance by using geophysical methodso After making clear of the sedimentary facies types and the main source direction,we drawn the plane distribution of sedimentary facies in unit of a base-level cycle,and disclosed the sedimentary characteristic and evolutional process.kongdian formationoshahejie forration three-stage,the fault activities in reserch area are intense,Fan deltas mainly develop in gentle slope belt and subaqueous fan near steep slope belt.Lake area expanded in Es1+2,but the water is shallow,Shore shallow lake and braided deltas develop.In Ed3,Fan deltas and braided deltas develop in gentle slope belt and nearshore subaqueous fans develop in steep slope belt.In Ed2,the scale of sandbody mainly from the brachy-axis of the sag is largest too,Braided deltas develop in the western gentle slope belt,fluvial fan develop from long axis source,Sand are widely distributed in the study area.alluvial and floodplain mainly develop in Ed1.Combining the sequence stratigraphic position,structure map,palaeogeomorphology characteristic,with the distribution of sedimentary facies,sandbody thickness,the conditions of forming oil/gas trap,trap types,source-reservoir-cap assemblage features and fault guidance system,the paper evaluates the favorable prospects,the paper proposes that the upper Ed2,the lower,Ed2,Ed3,Es1+2 and Es3 are the main potential layers,and two favorable formation-lithologic traps,the eastern of Lvda 10-1S slope zone,the west slope belt in the Southern of Liaoxi depression.