Abstract: This is an experimental study carried out by Daqing Oilfield to meet the requirement of comprehensive treatment of casing damage wells and potential tapping of residual oil in old oilfields in Changyuan area. To ensure the casing to work well above the windowing point and the cementing to be sealed effectively below the windowing point and at the perforated interval, workover operation is conducted on the casing damage wells of high water cut or low fluid production, based on the research results of fine description of target zones in casing damage well blocks. Perfect casing above casing well interval is selected and side tracking is conducted in the target zone. The process includes the selection of wells and zones, the determination of workover requirements and windowing location, the drilling tools and operating parameters, the horizontal well track control and well completion ways. The technique is a comprehensive process combining well workover, side tracking and horizontal well drilling, and the potential tapping result obtained in the field test is satisfying. This provides a new method for the workover of similar casing damage wells and the potential tapping of residual oil at the production tail of old oilfields.