Well casing guide string and repair method

摘要

Well casing is repaired using a guide string for maintaining contact with a lower casing section disposed in the well, particularly an open hole portion of such well. The guide string is connected to a swivel and milling tool and lowered into the casing section remaining in the open hole portion of the well for machining the upper end of the casing section. The swivel prevents build-up of angular momentum of the guide string which may decouple the guide string from the milling tool when the milling tool rotatably decelerates or snags during the machining or milling operations. The milling tool and swivel may be retrieved and the guide string, with a safety joint or fishing head, reinserted in the well during installation of a new casing section.