Structural and sedimentary features and their bearings on oil and gas accumulation in the Yong’anzhen oil field,Shandong

The Yong'anzhen oil field,located on the northeastern margin of the Dongying depres-sion,Shandong is ascribed to a complicated fault-block oil field in a medium-to high-grade exploitation area.The oil field is dissected by three major faults,and aligned,from the margin to centre of the basin,into four step zones.The overall structural patterns have controlled the differential accumulation and distribution of oil and gas in the Yong'anzhen oil field.The reservoirs in the study area consist of the fluvial-deltaic sandstone bodies in the second member and upper part of the third member of the Shahejie Formation.Three main stages have been distinguished for the delta development.The oil and gas distribution in the oil field is governed by the development and migration of the delta facies belt,and the static and dynamic regimes of oil and gas accumulation are determined by the types of sedimentary microfacies.