Considerations in Reeling Bundled Pipelines
Authors: Neck Mendel 
Published: October 2008

Reel vessel configurations are reviewed, the requirements of reeling in general are summarized, and then the specific problems associated with simultanous reeled installation of multiple pipelines are set out. Limitations in number and size of flowlines in a bundle are stated.

INTRODUCTION

Deepwater developments currently being constructed generally require more than one pipeline to be laid in parallel. For a single satellite well, this is likely to be a pigable pair of flowlines plus an umbilical. For a multi-well template, a separate flowline may be required from each well to avoid co-mingling, resulting in a large number of parallel lines in the right-of-way. Difficulties in tie-in of these flowlines to the template usually justify bundling for a unified lay installation rather than repeated separate lay of each line.

VESSELS

There are two reel vessels and a number of portable reels currently available, with each of the three working somewhat differently. Their qualitative characteristics are summarized below.

Apache

The Stena Apache utilizes a vertical-plane horizontalaxis reel. Pipe is paid onto the reel from a ramp, with an aligner at its highest point which also serves as a level wind. The pipe is unreeled through the aligner, then through a straightener immediately below it and on down the ramp into the water.

The Apache has been a dynamically positioned vessel from its inception. The DP system has been upgraded in 1994 for a higher level of redundancy and greater environmental stand-off. Sponsons are being added to increase the cargo weight capacity from the previous 2000 s Tons.

Chickasaw

Global Pipelines PLUS' Chickasaw is of earlier vintage, and utilizes a horizontal-plane vertical-axis reel. The system is similar to that of the Apache laid on its side, except that the pipe makes an "S" between the aligner and the pipe touchpoint on the reel instead of coming directly to the reel. The Chickasaw has operated between 1969 and 1993 as a towed vessel, equipped with azimuthing stem thrusters to help stay in corridor. It has been upgraded to a dual redundant dynamic positioning system in 1994.

Portable Reels

The portable reels tend to be vertical-plane horizontal-axis reels with a laterally traversing straightener near the base, but without any aligner. They may payout from near the top of the reel "overshot" for deepwater installations or from near the bottom of the reel "undershot" for routing onto the pipe alley for shallow water installations.

An interesting exception to the normal vertical-plane portable reels are the horizontal-plane reels used for umbilicals including helically laid steel umbilicals. The DCV Seaway Condor is equipped with such a reel; the pipe alley cantilevers over the port side and runs onto a stinger supported alongside the vessel.

REELING INDIVIDUAL LINES

Before examining the bundling issue, the special requirements of reeled pipelaying must be examined.

Mechanics of Reeling

Reeling of individual pipes makes demands not made on stovepipe installed pipelines. The hub diameters of both of the dedicated vessels and on the portable reels have been sized to produce 2% strain in the initial wrap.