The jacket platform has been produced for more than 20 years in the eastern part of the South China Sea. There has been a phenomenon of corrosion leakage of ?508mm casing with some wells. In one of the wells, leakage induce fracture happened on ?508mm casing, which lead to wellhead sink. Temporarily abandon the well with set cement plug, retrieve ?508mm casing from broken point, so that the risk of the oil spill is controlled. Small size casing tie-back technology has been applied widely, but there is no precedent for the application of ? 508mm casing tie-back in China. Through continuous technical verification, introduction of foreign large size casing patch and further improvement, successfully perform casing tie-back operation on the well, resume production after the well shut down 2 years.