Study On High-resolution Sequence Stratigraphy And Sedimentary Facies Of Chang1-chang 3 Formation In The Huangling Distric Of Ordos Basin

Trough the literature review,and based on theories and techniques of high-resolution sequence stratigraphy with analysis and interpretation of drilling/logging data,we studied on the sequence stratigraphic framework and sedimentary facies of Yanchang formation in the Huangling distric of Ordos Basin.A high-resolution sequence stratigraphic framework in this area is established.The types of sedimentary facies and the distribution characteristics of the favorable oil-bearing formations are identified.Eventually,the lithologic traps are preidicted.In light of the high-resolution sequence stratigraphic method,Chang 1 to Chang3 parts of Yanchang formation is a third-order sequence named LSC5,and this third-order sequedce can be diveded into 3 forth-ordedr sequences named LSC5-1,LSC5-2,LSC5-3 from the bottom to the top.LSC5 is also diveded into 5 sand groups,named Chang32,Chang31,Chang 23,Chang 22 and Chang 21.The framwork of part1 to part 3 of Yanchang formation in Fuxian-Huangling district is estabilished,and the Characterastics of the sequence stratigraph is studied.Through comprhesive analysis of drilling and logging facies,and based on the sedimentary facies study under the sequence stratigraphic framework,3 sedimentary facies a identified in the Chang 1 to Chang 3 part of Yanchang formation: delta front,delta plain and lake.Combining the controlling effect of paleogeomorphology,the distribution and evolution characteristics of sedimentary facies under Chang 1 to Chang 3 part of Yanchang formation sequence framework in Ordos Basin are identifed,which are drawn with the sand groups as the unit.In the period of Chang32,this area was dominated of delta front.In the period of Chang 31,the lake sedimentary area decreased,and the delta moved forwared to the centre of lake.In the period Chang 23,the range of underwater diversion channels of delta front expanded significantly.In the period chang 22,the range of water decreased and the range of delta expanded still,and delta plain begain to develop,sand sedimentary is dominated of diversion channels,and sheet sand is also diveloped.In period Chang 21,lake sedimentary was almost disapeared but only in the southwest part,diversion channels and sheet sand were developed most?The Chang 1 part is delta plain facies of large range,and is the perfect cover of Chang 2 part.After comprehensive consideration of the sequence stratigraphic position structure,paleogeomorphologic features,sedimentary facies,discovered oil and gastraps and trap types factors,the favorable oil-bearing formations are Chang 23,Chang 22,Chang 21 sand groups,and the favorable sendimentary facies are diversion channels,sheet sand and mouth bar.8 lithologic traps are identified in Fuxian-Huangling district,and westnorth part is the most favorable part.