Numerical Simulations of Wrinkle Sleeve Repair on Norman Wells: Zama Pipeline

The Norman Wells–Zama pipeline, the first ever buried pipeline built in Canadian north, which is owned and operated by Enbridge Pipelines Inc., traverses challenging terrains along the route. Certain segments of the line have been inspected annually using the GEOPIG ILI tool since 1989. This has provided Enbridge with a database with a large amount of curvature, pipe ID geometry etc. information available. Over the years, through the GEOPIG data it was identified that the pipeline developed a wrinkle along an unstable, monitored slope. Because of the high cost of the cutout and replacement work, it was determined to repair the wrinkle by encasing it using a pressure containing steel sleeve. An additional wrinkle subsequently developed adjacent to the repair, thus multiple sleeves were installed. This paper describes the numerical simulations of the double sleeve repair system (DSRS) carried out in the University of Alberta using finite element (FE) package ABAQUS 6.4. The numerical simulations utilize the data from the yearly GEOPIG measurements and the operational pressure history to try to trace back the loading history that the critical pipe segment might have experienced and to predict the possible behavior of the pipe segment under DSRS. A technique in the FE package ABAQUS, which was initially developed to simulate the assembly process, was successfully used to simulate the wrinkle sleeve repair sequential activities. A summary moment vs. curvature curve was obtained based on the numerical simulations.