| The lacustrine fan delta reservoir which developed in the southern slope of Binxian Bulge,Lijin Sag,Dongying Depression,Bohai Bay Basin,is an important exploration target in this area.However,the reservoir properties of these sand bodies vary significantly between different sedimentary stages of fan delta deposition,which inhibits further reservoir exploration and exploitation.There is currently no effective model to guide correlation and division of different stages in the deposits of a lacustrine fan delta like this one.Based on core observation,well log data and 3-D seismic data,we developed a new model for fan delta stage division that emphasizes the importance of lake level fluctuation and sediment source supply.These two factors have been thought as the two controlling factors that have a great influence on fan delta development.Regularity of lake level fluctuation was studied using sequence stratigraphic and sedimentary techniques,and source supply rate was estimated using coarse grain content calculation.According to the variation trends of lake level fluctuation,fan delta deposits in the LST can be divided into three sedimentary stages,and according to source supply rate,the three sedimentary stages can be further subdivided into eight sandbodies stages.The sandbodies developed at the top of each fan delta stage are thought to be the favorable reservoir based on reservoir properties statistics.This paper proposed a new method for sedimentary stage division which emphasizes the significance of lake level change and source supply variation.By using this method,fan delta of different stages in strata were precisely identified and divided,and geological explanation for mechanism of each sedimentary stage was reasonably provided.Thus,sheer geophysical analysis could be avoided and genetic mechanism of coarse-grained fan delta could be emphasized.It made a good contribution to the study of sedimentary stage division of coarse-grained fan systems. |
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