Research On Sedimentation Reservior Internal Architecture Of The Yanchang Formation Of Upper Triassic Chang 8 Oil-bearing Layer In Eastern Ordos Basin

In recent years,ChangQing oil field of oil and gas block and some new horizon was carried out by the combination of basic geology and development of geological comprehensive study,including the east margin of Chang 8 oil-bearing layer of East margin,Ordos basin region.So that they can more in-depth understanding and the anatomical study of reservoir lithology,sedimentary microfacies,sequence stratigraphy,reservoir characteristics,accumulation and favorable blocks or facies belt distribution,to further improve the efficiency of the oil and gas development in the study area to provide theoretical and technical support,also has very important academic value.Through the study of the field survey of the study area and on the basis of predecessors' research results,combined with the theory basis of sedimentology,sequence stratigraphy,guided by the law of delta front deposition and depositional model,the reservoir in the studied area is made to the configurations.The study area reservoir sand body development shallow water delta front and front delta two subfacies,constitute a datum plane dropped half a cycle,and divided into six sedimentary microfacies:subaqueous distributary channel,estuary dams,interdistributary channel,distal bar,front sheet and lake mud.Among them,the subaqueous distributary channel sand body is widely developed,which is the main genetic sand body,estuary dams,interdistributary channel,distal bar,front sheet sand can be seen scattered outcrop.Based on the Analytic Hierarchy Process,it is concluded that there are 10 kinds of rock facies and 7 basic elements in the formation of the Chang 8 oil-bearing reservoir.Based on the configuration interface principle division by Miall,the Chang 8 oil-bearing reservoir set delta front sedimentary bodies(subaqueous distributary channel and estuary dams)is divided into 5 level interface,established the configuration pattern of subaqueous distributary channel and estuary dams sand body.Summed up the single subaqueous distributary channel,estuary dams recognition mark;Summed up the subaqueous distributary channel sand body exist five kinds of spatial pattern and subaqueous distributary channel sand body have vertical accretion and progradational interlayer inside the body.The sand body connectivity between the underwater distributary channel is good.It is shown that there are two ways of lateral communication and multi layer connection,among which the multilayer communication is dominantOn the basis of the actual survey and statistics of the outcrops,the study area of the Chang 8 oil-bearing reservoir of the subaqueous distributary channel sand body width between 110 to 175 m,channel sand body deposit thickness between 7 to 12 m,generous than river in 13 to 18,the fitting of the relationship between the two,are suitable for the study of Chang 8 section of the single subaqueous distributary channel sand body width/thickness fitting the empirical formula W=218.4ln(H)-328.95,R=0.839,the subaqueous distributary channel is higher.According to the theory by Miall configuration hierarchy scheme,using cycle constraints and hierarchical analysis method,the Chang 8 oil-bearing of delta front deposition compound sedimentary sand body configuration interface from large to small cent gives three interfaces,namely:the subaqueous distributary channelof 5 architecture interface,the subaqueous distributary channel or single estuary dams of 4 architecture interface,muddy vertical interlayer between subaqueous distributary channels of 3 architecture interface.There are three kinds of combination forms ofthe subaqueous distributary channel and estuary dams sand body in the study area:the combination of SCH-SDB-SCH;the combination of SCH-SDB-MB and the combination of MB-MB.