| In continental rift-subsidence basins,delta sand bodies are major reservoirs of which the braided river delta accounts for a very large proportion.At present,lots of the oil and gas development for these reservoirs has entered high water cut stage in China.The study on reservoir architecture is an effective way of detailed description of flow channels and the distribution of interbeds.There are few researches focused on the reservoir architecture of braided river deltas.Thick sand bodies of Es2 in Yong 8 fault block,Shengli oilfield has been taken as research objects.And we have made full use of datum of cores,well logging,seismic and development data.Refer to Miall's fluvial facies configuration interface classification scheme,under the guidance of high-resolution sequence stratigraphy theory,under control of sedimentary cycle,the main intervals are divided into compound sedimentary bodies with the limitation of fifth surfaces and single sedimentary bodies with the limitation of forth surfaces.we make equal thickness maps of architecture elements and configuration interfaces,and analyze the distribution law of both sandstones and mudstones.Through carefully observation and description of rock core,we find that single sedimentary bodies include architecture elements such as underwater distributary channel,channel margin sediment,main mouth bar,periphery of the mouth bar,and interdistributary bay,corresponding to the well logging curvers,summarizing logging response characteristics of architecture elements,directing the longing identification of architecture elements.Measured and calculated the length,width and bent of the braided river delta distributary channel and valley through Google Earth images,we found that the distributary channel is straight but narrow which is always less than 300 meters.The existing research shows that the the braided river delta bars' size could be thousands off meters.Combined styles of single sedimentary bodies both in plane and profile have been confirmed,as well as the boundary of sandbodies,according to methods of dividing superimposed relationship which based on the comprehensive utilization of well logging curve differences,crosswise changing of sandbodies thickness,argillaceous sediment between sandbodies,and the number of interbeds.This research provides further insight into the basic process of single sedimentary body progradation,and defined the braided river delta in this block has characteristics of the channel being narrow,thin and straight,while the mouth bar being wide,thick and lateral.The statistical results of 30 sandbodies showed that correlation between the distributary channel and the mouth bar in width and thickness was nonsignificant,but the distributary channel and its matching mouth bar had a correlation,width of mouth bar is 2.23-8.95 times of the width of the distributary channel,80% concentrated in 1.25 to 2.5 times,and its thickness is 1.25-2.5 times of the distributary channel,75% concentrated in 3 to 6 times.This is associated with its shallow braided rover delta sedimentary environment.Comprehensive analyzed architecture elements,heterogeneity of reservoirs,preferential seepage and interbeds' influence on fluid percolation and the distribution of the residual oil,and putted forward different development programs aimed at different reservoir... |
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