Popeye Project: Hydraulic Umbilical
Authors: Jordan K.G. , Williams V.T. 
Published: October 2008

For the Popeye Project, the longest super duplex hydraulic umbilical in the world was installed in the Gulf of Mexico This paper reports on its selection and project implementation. Material selection addresses corrosion in seawater, water-based hydraulic fluid, and methanol. Five alternatives were considered:carbon-steel with traditional coating and anodes,carbon-steel coated with thermally sprayed aluminum,carbon-steel sheathed in aluminum,super-duplex, andtitanium.

The merits and risks associated with each alternative are discussed. The manufacture and installation of the selected umbilical are also reported.

Introduction

For Popeye, a static umbilical was required to transport water based hydraulic fluid and methanol 24 miles from the platform to the subsea completions. The great distance and high well pressure required a combination of tubing size (O.5' inside diameter) and operating pressure (10,000 psi) that had never before been applied in a subsea production system.

The traditional approach for subsea hydraulic umbilical, utilizing thermoplastic hoses, would have required development effort to achieve the increased size and pressure capabilities for Popeye. Additional concerns were the increased collapse resistance required at the Popeye depth andthe anticipated high cost of a hose umbilical. Shell research had demonstrated that a metal tube umbilical could be simply References and Figures follow paper constructed and reliably installed in sizes and pressure ratings that were more suitable for Popeye, and for other Shell Offshore Inc. (S01) deep water subsea prospects. The work also had suggested that such an umbilical would be more cost-effective than (he traditional hose umbilical. These considerations led to selection of metal tubes for theumbilical1

To meet the project requirements, a seven-tube, helical design was selected. as shown in Fig. 1. The required length was 124,000 ft, Each tube had an inside diameter of 0,50 inch and a 0.064-inch wall thickness. An outer polyethylene sheath was selected to improve the ability to handle the bundled tubes. The umbilical was not armored since metal tubes do not require this expensive protection. The overall diameter of [he finished umbilical was 2.2 inches and the fluid-filled weight was 25 pounds per foot.

Material Selection Criteria

The key requirement is maintaining pressure integrity and internal cleanliness for [he expected life of the project. Mechanical requirements of metal lube umbilical were previously described in Ref. 1. Along with the mechanical requirements, the material must resist corrosion in seawater and mud (on the outside) as well as water-based hydraulic fluids and methanol (on the inside), shown schematically in Fig. 2.

Exterior Environment. The tubes in an operating umbilical arc surrounded by seawater. For the Popeye Project, key properties of seawater such as temperature, oxygen concentration, and PH. were collected in a database2. The temperature declines from a mean of 75 ° F at the surface to 40 ° F at the subsea completion site, The oxygen concentration declines from 3.5 ppm to 2,1 ppm, while the pH decreases from a mean of 8,3 to 8.1.