Abstract: When the seriously damaged casings in old wells and shut - in wells in Zhongyuan oilfield were repaired by u-sing the conventional workover techniques, such as milling and shaping, the utilization periods of the repaired casings were short. In order to solve this problem, 101. 6mm casings were successfully set in the old casings and were cemented and perforated. These old wells and shut - in wells were brought on production again. The flood patterns were successfully improved and production addition and stabilization were realized.