Sequence Stratigraphy Study Of N₂³-Q₁₊₂ In Saline Lake Area,Qaidam Basin

Saline Lake structure in Qaidam Basin is a typical synsedimentary anticline,with the construction feature of steep dip angle in the north limb and gentle in the south.consistent with the characteristics of the ground structure.The main trap of the structure shows integrity and closed trap amplitude.The closed area is great and it is conducive to the formation of self-source and self-reservoir lithologic oil-gas reservoirs,high resolution sequence stratigraphy is one of the most effective methods to guide lithologic oil-gas reservoir exploration.This study is on the basis of previous studies,mainly on the existing drilling core,lithology and logging curve data.on the theory of high resolution sequence stratigraphy as a guide,to carry out the sequence stratigraphy study of the Salt Lake area,identify the sequence and system tract interface.establish Qaidam Basin in salt Lake Area III-IV level of regional sequence and sequence stratigraphic framework of N₂³-Q₁₊₂.Take the system tract as the basic unit,compile sedimentary facies map.Analysis the plane distribution features of the favorable reservoir,to predict lithologic trap favorable development area.The Saline Lake area of Quaternary Qigequan and Neogene shizigou formation can be identified 6 sequence interfaces,5 flooding surface.Among them,east Qigequan formation of Salt Lake area general lack of SQ5,caused by the eastern tectonic uplift and erosion in the Saline Lake area.Western Salt Lake buried depth is greater,the sequence shows complete development,and the overall stratigraphy shows high in the East and low in the west of the tectonic framework.Shizigou formation is deeply buried,with complete sequence development,the overall sequence thickness display uniformity.According to the QJ1 core observation,combined with the drilling and well logging data of wells in the Salt Lake area,on the basis of previous studies,in the Salt Lake area of Qigequan formation can recognize hore-lake and shallow-lake sub-facies.and Shizigou formation mainly developed delta plain and delta front sub-facies.In addition,Quaternary can also observe very loose,thickness in 10-50cm silty sand,microscope observation shows very well sorted,speculate as eolian sand deposit.On single well sedimentary facies and previous research foundation,took the system tract as a unit.salt lake sedimentary facies map can be created to predict each time the plane sedimentary facies characteristics of Quaternary Qigequan formation and the upper Tertiary in Shizigou formation in Salt Lake area.During the deposition of the Shizigou SQ1-SQ5,the Salt Lake area developed delta front sub-facies and local delta plain sub-facies.Qigequan SQ1-SQ3 with hore-lake and shallow-lake sub-facies,developed shore shallow lake dam,close to the provenance and develop small scale of delta front facies,during the period of SQ4-SQ5,Salt Lake area mainly for shore-shallow lake sedimentary facies.The favorable area prediction research mainly based on the lake expansion system tract In the development of the delta front sand body and shore-shallow lake beach bar sand body.The sand body of reservoir performance is good,and can be as a good reservoir.At the top of lake expansion system tract,the maximum flooding period of the formation of mudstone can be as important source rock or cap rock.Comprehensive Salt Lake area research of sequence stratigraphy and sedimentary facies,in the Salt Lake area according to the advantageous degree predicted three favorable target areas with ?,?,?.