Qualification Testing Of Flexible Pipes For 3000m Water Depth

Abstract

Abstract The paper is relevant to riser technology and specifically, qualification of flexible pipes for water depths up to 3,000m. This paper describes a comprehensive program aimed at the qualification of flexible pipes for ultradeep water applications. The primary design driver for ultradeep water flexible pipe applications is the resistance to hydrostatic pressure, in combination with dynamic curvature cycling. The two associated critical failure modes are hydrostatic collapse and lateral buckling of armour wires. Technip have developed dedicated flexible pipe components to address the severe loading conditions encountered in water depths up to 3,000m. Hydrostatic collapse resistance has been addressed by a thick inner carcass layer and a PSI pressure vault. Armour wire lateral buckling, which is induced by axial compression in the armour wires in combination with dynamic curvature cycling, has been addressed by the design and industrialization of new tensile armour wires. The design qualification process for these improvements was completed on two levels. Initially, a large number of pipes were subjected to dynamic cycling testing under high hydrostatic pressure in a hyperbaric chamber so as to determine design limits in terms of pipe diameter, water depth and component sizing. Then, design combinations were selected for testing in a real deepwater environment in the Gulf of Mexico. This second level of tests referred as Deep Immersion Performance (DIP) tests aimed at validating the results obtained from hyperbaric chamber tests. The DIP tests replicated the actual design conditions to which a flexible pipe would be subjected during installation and operation. The development of new and modified flexible pipe components provided a suite of flexible pipe designs suitable for extended water depth application. The final phase of the qualification program, namely the DIP tests, was completed in 2010. It provided design limitations of the new designs for both 9?? and 11?? internal diameter flexible pipes, in sweet and sour service in water depths up to 3,000m This paper clearly demonstrates the suitability of flexible pipes as a valid solution for ultradeep water applications as long as the mechanical behavior of the pipe components is adequately addressed. 1. Introduction and objectives The objective of this paper is to describe the comprehensive R&D project for the qualification of flexible pipes in water depths up to 3000m. The main and primary purpose of this R&D program was to demonstrate that the validation range of our flexible pipes can be extended from depths of 2000 m (as it was before project) to beyond today's market needs in Brazil and the Gulf of Mexico (Figure 1), i.e.3000 m for flexible pipe risers between 7?? and 9??2400 m for 11?? flexible pipe risers. A secondary objective was to extend to 3000 m, the validity range of our design models and of our testing methodology.