Sedimentary features and evolution of deep series in Lishu Fault Depression, Songliao Basin

According to the drilling cores, well logging and seismic facies data of the Lishu Fault Depression, the analyses of sedimentary features and evolution showed that the basement was cut by syngenetic fractures and seve-ral small fault depressions developed during the early stage. As lake plane rose during the early Shahezi period, a half-graben fault depression controlled by the Sangshutai Fault developed gradually. A structural pattern featured by fault in the west and overlap in the east and north controlled wide basin deposition in an unified water system. The sedimentary assemblage was characterized by deep/semi-deep lake, shallow lake, fan delta, delta, submerged fan and turbidite fan. The fault depression developed from shallow lake basin-swamp, to semi-deep/deep lake, and to semi-deep/shallow lake, and finally to shallow lake-river-delta. The exploration and sedimentary facies analyses of the Lishu Fault Depression showed that favorable reservoirs generated in every formation during fault depression evolution, mainly as fan delta front and delta front underwater distributary channel, mouth bar microfacies and gravity channel sand body. The Yangdachengzi area in the north and the Shuanglong-Dayushu-Xiaochengzi area in the east were favorable for exploration.