Research On The Sedimentary Facies Of The Second Member Of Shahejie Formation (E_s2) In Xia 32 Fault Block Of Linnan Oilfield

The Linnan subsag belongs to the secondary tectonic unit of the Huimin sag,located in southwest part of the Jiyang depression in the Bohai Bay Basin.The Xia 32fault block in Linnan Oilfield lies on the double abundant nasal structure of the west part of the Xia-Kou fault area,which is the obtuse-angle-shaped fault-block area between the Xiakou large fault and the Shuangfeng 1#fault.The second member of Shahejie Formation has experienced more than 20 years of oil and gas exploration and development,with the improving of the mining degree and degree of water flooding,the interlayer contradictions increasingly prominent,and the development difficulty is also increasing.Fine division,correlation of the stratigraphic units,the understanding of the type and distribution of reservoir sand bodies is the key to solving the problem,including types and distribution of reservoir sand body is controlled by sedimentary microfacies,and the study of sedimentary microfacies and its distribution regularity is imperative,providing geological basis for hydrocarbon exploration and development.In this paper,with the guidance of the sedimentology,sequence stratigraphy,logging geology,and other geology principle theories,The precise stratigraphic framework was established by using the method of sequence division cycle contrast.On this basis,the micro-phase recognition and division are carried out,and the spatial distribution characteristics and evolution modes of the sand bodies are demonstrated.The conclusions are as follows:?1?E_s2 were divided into 6 medium-term base level cycles and 29 short-term base level cycles,corresponding to 7 sand groups and 45 small layers.?2?Based on detailed core observation description,rock slice identification,combined with electrical survey data,it is considered that the rock type in the two section of the study area is simple,mainly terrigenous clastic rock,the overall grain size is coarse,the middle-fine sandstone is the main,the second is siltstone and mudstone,in which the sandstone particle is medium-poor,and the grinding circle is angular to the second angular point,The cement is mainly by the square solution stone,particles mainly for the point-line contact,the type of cementation mainly pore type,the basis of mud and organic matter,the maturity of the medium,structural maturity-poor,mudstone original color is mostly dark purple,brown,gray or gray green.The original sedimentary structures are horizontal bedding,parallel bedding,small staggered bedding,massive bedding,wave-like bedding,mixing structure and tearing debris.The data of sieve analysis shows that sediments grain size include two-stage curve and multiple three-stage curve.The C-M diagram shows that QR segment is the main development part,which reflects the transportation medium is characterized by tractive current.?3?Through facies markers and the analysis of the sedimentary background,it is concluded that E_s2 of Xia 32 fault block belongs to the delta-lacustrine sedimentary system,the main source from the southern Luxi uplift.The target section layer developed delta plain and delta front sub-facies,among 9 kinds of which the branching channel,swamp and estuary bar are the main sedimentary microfacies types.The sedimentary sequence is superimposed by the multiphase channel,which corresponds to the logging characteristics,and the vertical performance is mostly high-medium box,bell-shaped,with obvious"dual-texture".?4?In the medium-term base level cycle,the sedimentary evolution properties of E_s2 as follows.Midium-term base-level cyclic sedimentations are mostly lake transgression,that is to say,the lake water continues expanding and shrinking delta,such as MSC1,MSC2,MSC4,MSC5 and MSC6.During the period of MSC3,a complete lake was returned to the lake.At the end of the fifth sand group,the lake level reached a high level,and then began to enter the lake retreat process,and the delta was pushed into the lake.?5?Delta sedimentary face model is established,conforming to E_s2 of the study area.