The Research On Sedimentary Microfacies Of Chang6oil-bearing Of Yanchang Formation In Fuxian Area, Ordos Basin

Ordos Basin is a very important petroliferous basin of our country,its Mesozoic stratum has substantial oil and gas exploration prospect.After years of prospecting,the oil-gas seepages are abundant in Yanchang formation in Fuxian area,and find multiple oil-bearing sequence,at present,to varying degrees,there has found industrial oil run in Chang3,Chang6and Chang8oil-bearing.Many scholars have unfolded the study of sedimentary of different areas in Ordos Basin,but there are controversies about stratigraphic classification of Chang6oil-bearing of Triassic Yanchang formation in Fuxian area of Ordos Basin,and the studies on sedimentary microfacies and their combination features of Chang6oil-bearing are not systematic and deep enough,these restrict further oil and gas exploration and exploitation.The target stratum is in Chang6oil-bearing of Triassic Yanchang formation,and this article is guided by sequence stratigraphy,sedimentology,logging geology,lithofacies paleogeography and petroleum geology,on the basis of sufficient previous research achievements,by the use of geological field work,actual measurements of geological section,statistical datas of field palaeocurrent and jointm,with the combination of a comprehensive experimental datas such as core observation and description,X-ray diffract,SEM,slice observation,grain-size analysis and so on,and related to the drilling,well logging and testing datas,Chang6oil-bearing of Triassic Yanchang formation in Fuxian area of Ordos Basin is divided into four sub-oil-bearings,the Chang6~1sub-oil-bearing,Chang6~2sub-oil-bearing,Chang6~3sub-oil-bearing and Chang6~4sub-oil-bearing.Through the detailed lithology and electric property characteristic of the four sub-oil-bearings,on the basis of well logs,the author build the distribution model of Chang6 stratum,which can provide conditions for the late distribution of sand bodies and sedimentary microfacies.This artical studies a comprehensive and systematic research on the sedimentary microfacies of Chang6oil-bearing,through the drawn and analysis of different kinds of geological maps,recognize two main sedimentary microfacies types in the study area,including delta facies and lake facies,indentifies four sedimentary subfacies types,including delta front,prodelta,half-deep lake and seismites,and recognize ten sedimentary microfacies,including underwater distributary channel,subsea interdistributary bay,mouth bar,distal bar,front sheet-like sand,predelta mud,semi-deep to deep lacustrine mud,seismic,sandy clastic current and turbidity current.Through the drawn and analysis of distribution of sand bodies and sedimentary microfacies of four sub-oil-bearings of Chang6 sedimentary period,find the sand body location is controlled by sedimentary microfacies distribution,and extends in NE-WS direction.At last,the author establishes Delta sedimentary pattern and gravity flow sedimentary pattern according to Chang6oil-bearing of Triassic Yanchang formation in Fuxian area of Ordos Basin.