Composite Production Riser - Testing and Qualification
Authors: Drey M.D. , Salama M.M. , Long J.R. , Abdallah M.G. , Wang S.S. 
Published: October 2008

A Tension Leg Platform (TLP) component that lends itself to taking advantage of the unique properties of advanced composite materials is the production riser. A composite production riser (CPR) has the potential of reducing capital expenditure and improving reliability due to its lighter weight, improved corrosion resistance and excellent fatigue performance, compared to steel risers, for development of reservoirs in deepwater. A project was organized by several oil, service and composite manufacturing companies and partially sponsored by funds from the U.S. Department of Commerce National Institute of Standards and Technology (NIST) Advanced Technology Program (ATP) to determine the potential for cost reduction and overcome the technical challenges in design, analysis, fabrication, and qualification of a CPR. A critical element of this project is the specification and implementation of a comprehensive testing program to confirm the advantages, validate the design, and establish long term performance of a CPR as well as to secure the confidence of both operational staff and certifying authorities. The testing program was designed to develop performance data for basic materials, identify performance limitations, establish the failure envelope for the full diameter CPR joint, and verify that the manufactured CPR meets the performance requirements for application on a TLP in the Gulf of Mexico. In addition, the testing program, combined with the analytical effort, is sufficient to establish statistical variations in strength factors and generate data to design CPR's of different sizes and for different operating conditions. This will allow for site-specific qualification of a CPR with minimal testing. This paper will discuss the testing program, review its rationale, and present the preliminary results.

Introduction

Composite materials offer several attractive properties such as reduced weight, improved corrosion resistance, excellent fatigue performance and, potentially, lower system cost when compared to steel by taking advantage of the ability to tailor structure properties to achieve system simplification and improved reliabilitv. Therefore. composites have been receiving a significant amount of attention in the offshore industry as part of the effort to economically exploit deepwater oil and gas reserves. A TLP component that lends itself to taking advantage of these unique properties is the production riser. A CPR has the potential of reducing capital expenditure, due to its lighter weight and reduced requirement for pretension, and improving reliability for the development of reservoirs in deepwater using TLP's. A CPR not only reduces the required pretension, but may allow the rigid connection of the riser system to the platform, eliminating the expensive tensioners.

CPR's are one of the most characterized structural composite applications for offshore platforms because they have been the subject of several major studies within the last few years. The Institut Français du Pétrole (IFP), Aerospatiale, and several major oil companies sponsored a development and evaluation study of a 9 518 inch diameter CPR to prove the concept. The study was conducted between 1985 to 1990 (see References 1, 2, and 3). The CPR was fabricated of a hybrid of carbon and S-glass fibers. The CPR was designed to withstand a combined internal pressure of 105 MPa (15,000 psi) and axial tension of 450 metric tons (1,O 12,500 Ibs).