| The structural setting of Yongbei Area is in the eastest of northern steep belt of the Dongying Depression in the Bohaiwan Basin.The degree of prospecting is quite shallow and precision of three-dimensional seismic is high,but wells is of lack.Mainly based on seismic data to control the whole region,supplemented by core datas,log datas and test datas,guided by Vail sequence stratigraphy and sedimentology,the paper aims to systematically study characteristics of sequence,sedimentary facies,distribution of sedimentary facies and non-structural traps.We get several achievements below:(1)Guided by sequence stratigraphy and autocyclicity sedimentary law of sandy conglomerates,the framework of high-precision sequence stratigraphy is built for Es3 member of the Yongbei Area.Four regional boundarys are recognized including T1,T4,T6 and T6 x,which correspond to three three-level sequences(from top to bottom Es3 s,Es3z and Es3x).None four-level boundary is recognized in Es3 s formation,which suggests that only one four-level sequence Es3s-1 developed.Three four-level boundarys are recognized in Es3z(from top to bottom Es3-1,Es3-2 and Es3-3),thus four four-level sequences developed including Es3z-1,Es3z-2,Es3z-3 and Es3z-4.Two four-level boundarys are recognized in Es3x(from top to bottom Es3-4 and Es3-5),which correspond to three four-level sequences including Es3x-1,Es3x-2 and Es3x-3.(2)Guided by sedimentology theory,through the comprehensive analysis to residual geomorphology,makers of geology,logging and seismic,it suggested that two sedimentary facies,containing nearshore subaqueous fans and fan-deltas,exist in the whole region.The nearshore subaqueous fans developed in the period of Es3 x,when the boundary fault acted strongly,terrain difference is huge and lakebasin water is deep.In the early period of Es3 z,nearshore subaqueous fans still developed because the boundary fault acted more strongly,which caused to deeper water,however the scale of fans was smaller.In the later period of Es3 z,prograding fan-deltas developed when the boundary fault didn't act and base level was stable.In the period of Es3 s,the action of boundary fault leaded to the water deeper,retrograding fan-deltas developed.Based on RMS seismic attribute which is marked by cores and logging,the distribution characteristics of sedimentary system are confirmed.The nearshore subaqueous fans developing in the period of Es3 x and the early Es3 z distribute isolately and contact with deep-semideep lake facies,meanwhile,the fan-deltas developing in the period of later Es3 z and Es3 s distribute Contiguously along the Chenjiazhuang bulge and contact with shore-shallow lake facies.(3)Based on the study of sequence and sedimentary facies,combining with structural setting of the Yongbei Area,it is suggested that the formations in the top of Es3 member develop non-structural traps.The plugging mechanism of the traps are that the top is plugginged by the weathered clay layer of unconformity,and the flank is mainly plugginged by the thickened oil,which is strengthed by the physical property of fan-deltas plain.Besides,the sandy conglomerates in the front of fan-deltas could act as favourable reservoirs.The cap rocks,lateral barrier beds and reservoirs collocate organically to form the favourable traps in the research area. |
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