20080302539 | METHOD AND APPARATUS FOR LENGTHENING A PIPE STRING AND INSTALLING A PIPE STRING IN A BOREHOLE - The present invention generally relates to a method and an apparatus for connecting an add-on pipe segment to a pipe string to lengthen the pipe string using friction stir welding. The pipe string is suspended in a borehole using a spider or some other pipe suspending device, and the lower end of the pipe segment is brought into an abutting or nearly abutting relationship with the proximal end of the pipe string positioned above the pipe suspending device and above the rig floor. The friction stir welding machine is brought to well center to weld the abutment or gap between the pipe segment and the pipe string and join the pipe segment to the pipe string to lengthen the pipe string. In one aspect, the method includes friction stir welding an expandable pipe segment to an expandable pipe string to form a lengthened expandable pipe string. The pipe segment may be comprised of two or more pipe segments that have been friction stir welded or conventionally welded to form a pipe stand. After friction stir welding to lengthen the pipe string, the lengthened pipe string is lowered into the borehole and the proximal end of the lengthened pipe string is favorably positioned to abut or nearly abut a new add-on pipe segment for friction stir welding at the resulting abutment or gap. The friction stir welding process provides a highly reliable pipe joint for expansion. | 12-11-2008 |