Research On Sedimentary Facies Of The Cretaceous Bashijiqike Formation In Kelasu Structural Belt Of Kuqa Depression

Based on the observation,description and analysis of the core,this thesis applies principles of sedimentology,sequence stratigraphy,well logging geology and other related theories and methods,through comprehensive analysis of well logging,core,oil testing,seismic data and regional geological data,identified the base-level surface,establishing the isochronous stratigraphic framework,delineate sandstone distribution patterns and the type of sedimentary facies,by the use of numerical simulation technology,simulation of sedimentary facies evolution.And predicted by the geostatistical methods,comprehensive structural factors and sedimentary factors for potential favorable exploration areas within Bashjiqike Formation in the Dabei-Kishen area,Kelasu Structural Belt.The results show that Bashjiqike Formation recognized 8 sequence stratigraphic surfaces,including 2 first-level marker surfaces,2 secondary marker surfaces,and 4 tertiary marker surfaces.So we divide the Bashjiqike Formation into 3 oil groups of bs I,bs?,bs?,7 sand groups and further 15 small layers are divided.At the top,the bs I oil group suffered different degrees of denudation,from east to west gradually strengthened,and the bs I oil group in the Dabei area was completely missing.The Bashjiqike Formation mainly develops types such as pebbly sandstone,medium-fine sandstone,siltstone and mudstone.The color is mainly brown,tan,light brown,show a shallow water oxidizing environment.There are sedimentary structures such as block bedding,cross bedding,parallel bedding,horizontal bedding and scour surface.The lithofacies are mainly developed positive-cycling sediments,and in some areas development anti-cycling sedimentation.In the early stage of the Bashjiqike Formation,the bs? oil group is lowstand systems tract,the compositional and textural maturity are relatively low.It shows the sedimentary characteristics of near-source gravity flow and traction flow,and develops the fan delta front subfacies.In the middle and late stages,the bs? oil group and the bs I oil group correspond to transgressive systems tract and highstand system tract,the compositional and textural maturity are relatively high,showing the sedimentary characteristics of the far-distance traction flow,and develops the development of the braided river delta.The characteristics of heavy minerals and rock compositions show that the source supply from the northern Tianshan to the southern lake basin.Bashjiqike Formation sand bodies on the plane are mainly distributed in the form of strips and continuous,the high value areas are lenticular.In the vertical direction,multiple periods sand bodies are interlaced in subaqueous distributary channel,usually the thickness of the single layer is large.And the trend is north to south.Among them,bs? oil group has large thickness and good pore permeability,it is a high-quality reservoir.According to the distribution of sand bodies and the characteristics of sedimentary facies,applied geostatistics method to analyze the effective reservoir characteristics and distribution of the Bashjiqike Formation in the study area.It is believed that the area is mainly for fracture development reservoir and primary porosity protection reservoir.Comprehensive consideration of structural factors and sedimentary factors,delineate the favorable exploration areas for the dominant sand reservoirs.