Analysis Of Sedimentary Architecture In Chang 6 Of Yanchang Formation, Upper Triassic, Ordos Basin

In this paper,guided by the theory of sedime ntology and based on field outcrop data,paleontological data and geochemical data,sedimentary facies types of Chang 6oil reservoir group was identified.And then,sedimentary facies profile and plane distribution characteristics were depicted.According to the research of sedimentary facies,the architecture interfaces of different genesis units were distinguished.And then,architecture combination styles are portrayed,architecture parameters are extracted and delta architecture model in the study area was established.In the last,based on sedimentary facies and architecture analysis,this paper studied the reservoir macroscopic heterogeneity characteristics in the east edge of research area.After comprehensive analysis of various kinds of information,this paper idetfied sedimentary facies,which are meandering river facies,meandering river delta facies,braided river delta facies and lake facies.In the field outcrop section area,meandering river delta and braided river delta are the main sedimentary facies,in which main reservoir sand body are distributed.So the delta is the focus of the study.Based on the architecture interfaces identification and architecture unit discrimination,this paper identified 6 types of genetic units,which are distributary channel,natural levee,abandoned channel in the delta plain subfacies and the underwater distributary channel,mouth bar,between tributary bay in the delta front subfacies.In this paper,treated distributary channel,underwater distributary channel and mouth bar as the key of architecture analysis,four architecture vertical combination modes were put forward,which are distributary channel and distributary channel superimposing,underwater distributary channel and underwater distributary channel superimposing,mouth bar and debouch bar superimposing,underwater distributary channel and mouth bar superimposing.The first three kinds of combination can be divided into discrete type,lateral superposed,vertical superimposed and composite superimposed;The last one can be divided into the upper fold type,the folding type and parallel type.then the two architecture modes were summed up: "gentle slope type mode" and "abrupt slope-type mode".According to the study of sedimentary facies and architecture,the delta plain reservoir macroscopic heterogeneity characteristic of Chang 6 oil reservoir group was carried out.The heterogeneity in the layer is well;the interlayer heterogeneity is medium.