Apparatus and method for isolating a section of a pipe riser bore in the course of riser renewal

Abstract

The isolation tool works at depth in the bore of a pipe whose upper end is to be severed and replaced. The tool isolates the lower pipe bore from the upper bore so that flammable downhole fluid is prevented from reaching a welding site along the pipe wall. The tool incorporates: means for establishing a pair of axially spaced apart annular seals engaging the pipe inner surface; means for venting downhole fluid to ground surface; and means for monitoring for seal leakage. The tool is primarily mechanical in nature. It finds use in connection with off-shore platform riser renewal operations.

What is claimed is: 
     
         1 . A method for isolating an open end section of the bore of a pipe from the remainder of the bore, said pipe extending upwardly to ground surface, comprising:
 positioning a pair of axially spaced apart annular seal elements, mounted on a body, at depth in the bore of the pipe, using a string of joints joined to end;   deforming the seal elements from ground surface, using a string of tubular rods, so that they seal against the pipe and combine with the body and the pipe to define a sealed space; and   circulating pressurized liquid through the sealed space from ground surface and back through conduit means to provide an indication of seal competence.