Casing cutting technology for abandoned deepwater wells

The deepwater subsea wellhead is of large size and high strength. The increasing water depth results in complexity of string stress during the cutting process. Plus immaturity of cutting tools and lack of experience, there is a great technical challenge to earlier self-support deepwater wells in China, when the abandoned wells’ of casing and subsea wellhead is cutting, which may result in complex conditions of varying degrees in the operation. Considering the construction cases of self-support deepwater wells and foreign deepwater abandoned wells, the risks and technical difficulties in casing cutting of deepwater abandoned wells are deeply analyzed, and the causes for failed operations are summarized. Methods to improve the technical solutions, abandoned well tools, and construction parameters are proposed. The risks in the operations of deepwater abandoned wells are fully analyzed and appropriate preventive and control measures are provided, which successfully applied in the second batch of deepwater wells to improve the safety and timeliness of deepwater operations. That confirms the correctness of the previous improvement ideas and solves the technical problems about deepwater abandoned wells.