Analysis Of Depositional System Characteristic And Favorable Facies Zone In The Second Member Of Shuangyang Formation In Area-C Of Changchun Oilfield

Area-C of Changchun oil field is located in a five-star structural belt of luxiang fault depression,Yitong basin,and this block is controlled by No.2&No17 fault.Its structural feature is monoclinal structure which dips to the southwest.The purpose layer is the second member of Shuangyang Formation of Paleogene,and is 1800-1900 m in buried depth.The reservoir`s depositional system is fan-delta,with high porosity-permeability,high pore-throat ratio features,and the heterogeneity of reservoir is severe.There is three main Contents in this paper:1.types of lithology and microfaciesThe well data reveal the rocks of the second member of Shuangyang Formation in Area-C,are four main types of conglomerate,sandstone,siltstone,and mudstone.Two subfacies of fan-delta front and fan-delta plain were distinguished.Established the identification models of lithologic-microfacies by core data,and then based on bare log data establish the identification models of logging-microfacies,Research on Perfecting lithology and microfacies of Area-C.2.Analysis of depositional system based on single sand bodyThere are more than 40 single sand bodies in the second member of Shuangyang Formation in Area-C in 5 sandy groups.Analysis depositional system of these bodies one by one.Comprehensive analysis problem of their entrance and travel direction of provenance,size fraction and genesis.Results of depositional system distribution of Area-C show that the source comes nearly from the eastern,and the river channels flow from east to west with the characteristics of river diversion and superimposition of channel sand-bodies.3.Analysis of favorable facies beltBy physical property combined with oiliness of this area and data statistical sorting,there reach a conclusion: sandy bodies in this area can be divided into three grades by permeability,and the best layer are distributed both subfacies of fan-delta front and fan-delta plain.The favorable facies belt are channels in fan-delta plain(sandy channel and abandoned channel,gravel channel is a little lower)and mouth-bar in fan-delta front.Some of natural levee and underwater channel also have good oiliness.