This paper describes the method and equipment developed to allow ROV installation of a grout-filled reinforcement sleeve on a damaged 18” subsea gas pipeline at a water depth of 2,300 ft. The Williams Canyon Chief pipeline was damaged by an accidental anchor drag that pulled pipeline 1,500 feet out of its original path, bent the pipeline to an unknown radius, and left a significant dent in the side of the pipe as well. The damage did not result in a leak and the pipeline was allowed to continue to operate at reduced pressure while repair plans were developed.
Extensive research and testing determined that the pipeline could be returned to normal operating pressure if the dent could be restrained from flexing due to changes in pipeline pressure. Laboratory testing confirmed that cement grout inside a steel sleeve installed around the dent would provide the necessary reinforcement. A specially designed, ROV friendly repair clamp was developed to match the pipeline curvature that was estimated by side scan sonar imaging. The clamp was fabricated as a straight cylinder but the ends were angled and positioned off-center to account for the pipeline curvature. The clamp was split horizontally so that all clamping screws were vertical. An articulated spreader bar, ROV operated pull-down winches, and a large syntactic buoyancy module allowed the ROV to control the entire installation after the equipment spread was landed on the seafloor.
A project specific metrology tool that measured the curvature of the pipeline at 24 points was built and landed on the pipeline. A ROV video record of the gauge readings was then used in the shop along with the metrology tool to fabricate a dimensionally correct mock-up of the pipeline. This mock-up was then placed into the repair clamp to confirm that it would fit on the pipeline.
Vagata, A., Bath, B., Alexander, C., Aalders, A., and Seal, D., “Application of a Grouted Sleeve to Remediate a Damaged Subsea Pipeline” 2012 Offshore Technology Conference, April 30 - May 3, 2012, Houston, Texas.