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Accurately identifying and quantitatively describing abandoned channels in meandering rivers are of great significance for improving hydrocarbon recovery.By using modem deposition analogy,field outcrop analysis,a dense well spacing,core observations and a review of the literature,this paper studied the formation process and space-time amalgamation of abandoned channels in meandering river.The results reveal that formation mechanisms of abandoned channels include chute cutoff patts (shoal-cutting,ditch-scouring and embayment-eroding patts) and neck cutoff patts.The chute cutoff patt forms a gradually abandoned channel,while the neck cutoff patt forms a suddenly abandoned channel.From upstream to downstream,the sedimentary patt of the abandoned channel transforms fiom a chute cutoff patt to a neck cutoff pattem,where the main controlling factors transition from the grain size and gradient to the flow and vegetation.An abandoned channel formed by a chute cutoff patt consists mainly of siltstone,fine sandstone and thin gravel layers,which form a lithological-physical barrier.The abandoned channel formed by a neck cutoff patt consists mainly of mudstone and argillaceous siltstone,forming a lithological barrier.Based on the amalgamation and structure of the reservoir architectural elements,the abandoned channel can be divided into three planar sedimentary patts (crescent,semilune and horseshoe) for a single channel and five vertical sedimentary patts for composite channels.