Manipulating guide tube connecting well-head to ship - without lifting to surface for use of larger equipment

摘要

A guide tube assembly makes it possible to bore in deep water with a smaller dia. tube, without repeated time wasting trips to the surface, when larger dia. boring tools, liner tubes, etc. have to be introduced. The assembly extends from a floating boring vessel to the piping head of a borehole on the seabed, and includes a guide tube standing near enough vertically. The upper end of the tube is held in the vessel and its bottom end is supported by a structure close to the piping head. The supporting structure enables the bottom end of the guide tube to be moved between a first position in which it is axially in line with the piping head, and a second position offset laterally to the centrally located bore of the hole. A stack of blow-out preventer valves is secured to the piping head and there is a frame around this with struts giving support to the guide tube. The invention eliminates the need to lift the guide tube when bore tubes, piping or tools with a larger dia. than the inner dia. of the guide tube must be put down the hole in the seabed, or when blow-out preventers have to be replaced. Instead of lifting the guide tube to the surface it can be displaced sideways so as to free the piping head.