Economic Benefits Of Sub-Sea Pipe-Line Rehabilitation Using Spoolable Fiber- Reinforced High Pressure Line-Pipe
Authors: Nolet Stephen , Feechan Michael 
Published: October 2008

Increasingly, spoolable fiber-reinforced line pipe has gained acceptance for use in transport of high-pressure oil field fluids in applications including wellhead production gathering lines, flow lines, and injection lines. The high corrosion resistance and low connector count make these products a very reliable choice for new installations.

Another extremely attractive use of spoolable fiberreinforced line-pipe is in the rehabilitation of conventional jointed steel sub-sea flow lines that have either been decommissioned or derated after years of service. In these applications spoolable composite line-pipe is either "pulledthrough" or "pushed-through" the existing steel line which then acts as a passive conduit for the protection of the fully pressure capable spoolable composite. In most cases the lower flow-friction coefficient of the spoolable composite combined with the enhanced pressure capability results in the full restoration of the flow capacity of the original line.

In the Gulf of Mexico a significant length of steel line-pipe has been rehabilitated for a major operator using spoolable reinforced line-pipe. In this shallow water application steel flow lines, which had been experiencing regular failures were brought back into production using Fiberspar spoolable composite linepipe. Installation of the spoolable composite utilized a wire-line unit in a "pull-through" operation or a modified coiled tubing injector in a "push-through" operation to quickly draw the composite linepipe through each separate line with minimal or no disturbance of the existing steel flow line.

The application of the spoolable composite line pipe resulted in rapid installation, low connector count and minimal sea bed disturbance contributed to a significant project cost savings over options requiring the removing or retrenching of jointed flow-lines. The design requirements, installation technologies and cost benefits of this case study are discussed.

Spoolable Composite Line Pipe

Fiberspar Corporation has been active since 1995, in advanced development of composite technology to provide continuous, fiber-reinforced, spoolable pipe solutions, building on technology initiated at Conoco in the late 1980's. The first commercial applications of spoolable composite line pipe were for flow and injection lines. Since the first installations just over three years ago, almost 2 million feet of spoolable composite line pipe has been installed in dozens of different applications. About one-third of the total installed to date has been onshore in North America in applications to rehabilitate existing flow lines, the balance being used for new installations.

Design and Manufacture

Spoolable composite pipe (Figure 1) consists of a thermoplastic pressure barrier or liner, bonded to a structural reinforced fiber layer or laminate. The thermoplastic pressure barrier uses the same High Density Polyethylene (HDPE) or crosslinked Polyethylene (PEX) materials that are now commonly used by the oil industry. As a result, a great deal of institutional knowledge already exists on compatibility with various oilfield fluids.

The pipe is manufactured in a high quality, fully automated and continuous manufacturing process by wet winding fibers in an epoxy matrix onto the thermoplastic liner, which acts as a manufacturing mandrel but which is left in place to function as a fluid and pressure barrier, while the fiber reinforced epoxy matrix provides structural strength in both hoop and axial directions.