Abstract: Some of the offshore oil and gas fields have entered the late stage of development. The number of remaining well slots cannot meet the needs of exploration and development. Building new production platforms to drill new wells does not meet economic benefits. Therefore, it is necessary to abandon old wells and then use old well slots to drill new wells. In the process of disposing old well casing, the casing is seriously attached, the wellbore does not return, and the conditions of casing milling and grinding are not satisfied. Cutters and fishing spears are used to deal with the problems. Aiming at the special situation of difficult insertion of fishing tools and casing blockage, the analysis and treatment are carried out to recover casing smoothly and meet the requirements of sidetracking, which has certain guiding significance for subsequent such operations. It is recommended to use cutters and fishing spears to handle special cases and recover casings when old offshore wells are abandoned.