Study On Reservior Heterogeneity Of Braided-delta

This paper took the Shawan Formation in Neogene of Chepaizi East Area for example. Using traditional cycles contrast, uniform thickness contrast, deposition model trend contrast, and other methods and theories, the formation was subdivided and correlated finely. Analysing the sign of sedimentary facies, the facies type, distribution character and facies model were studied. Analysing pore structure and diagenesis, micro- heterogeneity model was established. The distribution of porosity, permeability and variation coefficient in each microfacies were researched and the macro-heterogeneity model was established, and the relation between reservior heterogeneity and the distribution of oil was researched too.The following researching results and cognition were acquired mainly.(1) The formation was correlated systematically and subdivided into 7 sand formation, 18 sublayers.(2) The depositional system of Shawan Formation in Neogene of Chepaizi East Area was braided-delta-lacustrine facies. The first and second member of Shawan Formation was braided-delta front subfacies, which composed of underwater distributary channel, subaqueous interchannel and sand sheet. The third member of Shawan Formation was braided-delta plain subfacies, which was divided into braided channel and flood plain. The braided-delta died out downcoast.(3) The pore structure types was generalized and micro- heterogeneity model was established. Underwater distributary channe was the best reservoir in braided-delta.(4) The macro-heterogeneity model was established. Internal and plane heterogeneity of braided channel presented strong degree and interbedded heterogeneity presented middle-strong. Internal and plane heterogeneity of underwater distributary channel presented strong degree and interbedded heterogeneity presented middle-weak. Internal and plane heterogeneity of sand sheet presented middle to strong degree and interbedded heterogeneity presented strong. Steric heterogeneity of braided channel was stronger than underwater distributary channel, which was stronger than it of sand sheet.(5) The relationship between oil distribution and reservoir heterogeneity was clarified. The homogeneous degree was determined by reservoir heterogeneity. The weaker heterogeneity was, the more uniform oil distribution presented. Oil abundance degree was affected by porosity, permeability and reservoir heterogeneity. Oil saturation and poroperm displayed direct ratio. Oil distributed in the area that presented herterogeneity of weaker level.