Abstract: There was early hercynian karst development in eastern ordovician reservoirs of block-12 in Tahe oilfield,the surface water and groundwater activities are strong,and the ancient river channel and the distribution of karst reservoir development has a close relationship.Therefore,the precondition of the regional reservoir development status is to identify the ancient river.First of all,based on the extraction of the geophysical methods such as amplitude,coherent,the overall appearance of paleochannel in the study area needs to be found out.Secondly,through the well drilling,logging data analysis,identify the ancient rivers,and adopts the double-peak limestone layer flattening technique,restored the ancient landform in the study area,to identify the surface of the river.Finally,by mapping splicing technology,the developmental characteristics of paleochannel in the study area have been made clear.At the same time,according to the actual drilling and the enrichment of oil and gas reservoir development situation analysis,the ancient river development zone has two advantages of reservoir development mode,and this is of the vital significance to guide the development well placement.