Research On The Sedimentary Characteristics Of Two-three Sand In The Fourth Member Of Shahejie Formation In The Broken Order Raised Belt Bonan Depression

This article is researching the sedimentary characteristics of two-three sand in the fourth Member of Shahejie Formation in the broken order raised belt.Therefore,a combination of well logging and seismic data combined with 300 km~2 3D seismic data from 17 wells has been comprehensively analyzed and studied in the stratigraphic framework based on group units in this paper.The results show that the two-three sand in the fourth Member of Shahejie Formation Bonan depression is a continental deposit stratum mainly composed of lacustrine deposit,fluvial deposit and delta deposit..there are mainly shore-shallow lake-semi-deep lake-deep lacustrine sediment in the second sand group.The common sedimentary microfacies include beach dams,beach sands,shore shallow lake muds,and so on.The third sand group mainly develops delta deposit.The common sedimentary microfacies include braided river delta,sheet sand,rar sand dam,underwater distributary channel and underwater shunt bay.The three-two sand group in Bonan depression is a process of water subsidence-water transgression.They Deposit formed under controlled by paleo structure delta-lake basin sedimentary system.North,east steep slope and the south,and west of the ancient land form landscape makes certain sedimentary differentiation.There are sedimentary differentiations in this time.three sand formation sedimentary period in the north east there is a lake basin deposition center,north and south for delta deposit,west and south of the delta plain and delta front deposition.During the sedimentary period of third sand formation,there is a lake basin depositional center in north and south.Delta is deposited in the north and south,and delta plain and delta front deposits in the west and south.The influence of water intake and gradual filling until the second sand group and gradually changed into the shore-shallow lake,the deep-half deep lake subfaces.Through the analysis of electro facies and seismic facies,the whole area of the whole fourth Member of Shahejie Formation in the Bonan depression is north south steep slow.They are controlling the sedimentation of the fan delta and the Delta plain deposits,which ultimately has a certain effect to the reservoir.The he fourth Member of Shahejie Formation on the section through the sedimentary differentiation from bottom to top are verge to accordance.The third sand group in general can be divided into the following three parts:Chengnan fault-Guxi fault steep depositional model,Bohai sea,north and south lake basin center half deep lake depositional model,north gentle slope of Chenjiazhuang heave sedimentation model.This geomorphic feature is basically a dividing line of deltaic plain and delta front sedimentary facies.The sedimentary facies model is obviously controlled by paleo structure and paleo sedimentary environment.When the second sand group deposited,the water was rapidly enter the lake,and during this period the process also made a very large difference in the deposition between second and third sand group.The sedimentary grain size of sanding group is coarse and the ratio of sand land is higher in the third sand group.However,the sand ground value ratio is lower than that of the two sand group.Most of the well drillings have ream rock and dolomitic mudstone.They are indicated that the lake area was enlarged at that time,which is characterized by shallow water Aral lake.