Application of a Grouted Sleeve to Remediate Damaged Subsea Pipeline
Authors: Vagata Alessandro , Bath Bill , Alexander Christopher Richard , Aalders Alexander , Seal Danny 
Published: April 2012

This paper describes the method and equipment developed to allow ROVinstallation of a grout-filled reinforcement sleeve on a damaged 18" subsea gaspipeline at a water depth of 2,300 ft. The Williams Canyon Chief pipeline wasdamaged by an anchor drag that pulled pipeline approximately 1,500 feet out ofits original right-of-way, bent the pipeline to an unknown radius, and left asignificant dent in the side of the pipe as well. The damage did not result ina leak and the pipeline was allowed to continue to operate at not only areduced pressure, but also a minimum pressure, while repair plans weredeveloped.

Extensive research and testing determined that the pipeline could be returnedto normal operating pressure and ultimately maximum design pressure if the dentcould be restrained from flexing due to changes in pipeline pressure. Laboratory testing confirmed that cement grout inside a steel sleeve installedaround the dent would provide the necessary reinforcement.

A specially designed, ROV friendly repair sleeve was developed to match thepipeline curvature that was estimated by side scan sonar imaging andphotogrammetry. The sleeve was fabricated as a straight cylinder but the endswere angled and positioned off-center to account for the pipeline curvature. The sleeve was split horizontally so that all clamping screws were vertical. Anarticulated spreader bar, ROV operated pull-down winches, and a large syntacticbuoyancy module allowed the ROV to control the entire installation after theequipment spread was landed on the seafloor.

A project specific metrology tool that measured the curvature of the pipelineat 24 points was built and landed on the pipeline to confirm earlier calculatedestimations. An ROV video record of the gauge readings was then used in theshop along with the metrology tool to fabricate a dimensionally correct mock-upof the pipeline. This mock-up was then placed into the repair sleeve to confirmthat it would fit on the pipeline.

Introduction

In 2005 the Canyon Chief pipeline was hooked by an anchor. At a depth of 2,300feet, the anchor dented the 18" − 7/8" wall pipe and pulled it approximately1500 ft away from its original path. ROV inspection at the time of the accidentindicated that the pipeline was not leaking. However, in the interest of safetyand to comply with applicable safety guidelines, the pipeline pressure in theANSI 1500 class pipeline was managed to a minimum 900 psi and maximum of 1600psi and allowed to continue in operation while, at first, cut and replace wasplanned, and then after smart-pigging and thorough modeling, a remediationmethod was developed. It was necessary that after remediation, the pipelinecould be returned to the full 3,200 psi design operating pressure.

This remediation project was started with minimum information. Availableinformation included data from a project designed Rosen Inspection Servicesmulti-diameter smart-pig measuring run that showed the location and adent-dimensional profile (Figure 1), a high resolution photogrammetry pictureof the dent, an ROV picture of the dent (Figure 2) that showed that the pipewas clean and the coating was mostly intact, and a sonar image of the bend inthe pipeline. To estimate the curvature, the data from the photogrammetry wasutilized and the sonar image (Figure 3) was overlaid with scale circles thatbetween the two methods gave confidence that the radius of the bend was between35 and 80 feet.