Qualification of Fiber Wrapped Steel Pipe for High Pressure Arctic Pipeline
Authors: Salama Mamdouh M. 
Published: December 2011

The transportation of the major known reserves of natural gas in the remote arctic regions requires the installation of large diameter pipelines operating at high pressures for long distances. Continued technological advances to reduce the development and life cycle cost while maintaining the required high level of safety is critical to the economic feasibility of these pipelines. In order to reduce cost, high strength steels (&gt; X80) are being considered to reduce the wall thickness of the pipeline and thus lower the materials, transportation and construction costs. However, producing large diameter high pressure pipelines of these steels creates significant procurement and technical challenges. This paper introduces an alternative technology that will reduce cost even more than high strength steels while eliminating the technical and procurement restrictions by allowing the use of low grade conventional steel such as X70. This technology involves hoop winding low cost dry synthetic fiber such as fiberglass over a conventional steel pipe (e.g. X70). The combined system will results in a high pressure pipe with high plastic strain capacity that is required for pipeline installed in discontinues permafrost and seismic regions. This new technology is referred to as dry fiber augmented steel technology pipe (FAST-PipeTM). The paper presents the results of a rigorous qualification program that was structured based on the industry technology qualification guidelines (API 17N).

1. INTRODUCTION

The demand for the transportation of natural gas over long distances requires large diameter pipes operating at high pressures. An example of such a pipeline is the proposed 3500 miles Alaska gas pipeline that intends to transport about 4 billion cu ft per day of natural gas from the North Slope of Alaska thru Canada to the market in central USA. The design base case for this pipeline is 48 inch pipe of×80 steel operating at 2500 psi. Considerations have also been given to use higher grade steels such as such as X100 and X120 to allow the use of pipes with smaller wall thickness and thus reducing material, transportation and construction costs. However, high strength steels suffer from several limitations including limited production capacity, and the potential of low reliability due to the low crack arrest resistance, the low bending strain capacity, the low burst safety factor, and the difficulty of ensuring strength overmatching of welds.

When the oil industry faced the challenges of weight, reliability and cost for high pressure deepwater risers, it pursued composite materials as feasible option to reduce both riser weight and system cost. A 22 inch diameter composite drilling riser joint was successfully installed on a Tension Leg Platform (TLP) located on the Heidrun field in the North Sea and was used in drilling more than 18 wells [1–2]. The 22 inch composite drilling riser had a 3-mm titanium liner and was qualified for a burst pressure of 15,800 psi. Also, 10 ¾ inch composite production riser with 4.7 mm steel liner was designed for application on a Gulf of Mexico TLP and was qualified for a burst pressure of 25,500 psi [3]. Building on the successful offshore experience with composite risers, the pipeline industry began considering composite pipelines as alternative to higher strength steels. TransCanada evaluated the use of composite reinforced line pipe CRLP™ and successfully installed several test sections on existing pipelines [4–6]. TransCanada's installations included 2 km of 24?? CRLP™ pipe on Buffalo Creek pipeline and 100 m of 48 inch CRLP™ on Saratoga pipeline. These successful demonstrations were instrumental in incorporating the application of Composite reinforced steel pipeline in the Canadian Standard CSA Z662 on " Oil & Gas Pipeline System??. TransCanada reported that the installed cost of composite reinforced steel pipe is 7 to 8% lower than an equivalent steel pipe.