Abstract: The Ordovician reservoirs in the Tahe Oil Field are typical fractured and vuggy carbonate reservoirs. The superimposition of tectonic settings, karstification and diagenetic effects formed pores, caves and fractures, which served as storage spaces and migration pathways for hydrocarbons. With the deepening of water injection development, water injection failure gradually increases, and some wells have recovery rates lower than 10%. The pressure changes, injection scale and cyclic injection amount of water injection were studied to determine the reservoir type and scale for failed wells. This method has been applied in field works, and proved effective.