Design Verification of a Composite Production Riser
Authors: Baldwin D.D. , Lo K.H. , Long J.R. 
Published: October 2008

In 1995, a joint effort was begun, under the auspices of the NIST/ATP, to design, develop and test a composite production riser (CPR) suitable for deep water (3000 to 5000 feet) applications. Functional, operational, and performance requirements have been specified by oil company participants and are representative of current and anticipated projects. The objective of the effort is to arrive at a cost-effective design for a composite production riser that meets reliability performance of current steel systems. Well-established design methodologies for advanced composite structures have resulted in a CPR design meeting the project cost, weight and performance goals. This CPR design is currently undergoing an extensive series of design verification tests. A primary purpose of this testing is to correlate and analyze riser joint performance with analysis predictions, in the interest of verifying static and cyclic performance and manufacturing variability. To satisfy this purpose, a test program has been defined to derive statistically significant data on mechanical properties and to identify failure modes and locations to achieve the required confidence in design, fabrication, and short- and long-term performance of the CPR. A total of 68 prototypes are to be fabricated and tested for ultimate strength determination, static and cyclic fatigue performance, and characterization of damage tolerance. A status report of the testing and analysis is reported in this paper.

Introduction

A joint-industry CPR project, jointly financed by NIST/ATP, is currently underway. The goals of the project are to design, develop, manufacture, test and qualify a TLP production riser 103 made with fiber-reinforced polymeric composites. Lincoln Composites is leading the effort in engineering design and fabrication of the CPR. A concentrated effort was conducted in the first part of the project to design a low-cost, lightweight CPR suitable for deep water (3000–5000 feet). Both single casing and dual casing risers were considered. Figure I shows a typical TLP production riser system. Polymeric composites are attractive alternative materials to steel for the production riser mainly because their light weight will give rise to lower riser top tension (and hence lower loads supported by the platform). In addition, the more compliant CPR could help to reduce or eliminate the need for the top tension system, resulting in further cost benefits to the riser system and platform construction. In the current study, severaljoints of steel riser casing would still be used at the top and bottom of the riser string, in order to avoid the application of significant bending loads to the CPR. Keeping the composite joints below the waterline also avoids exposing the composite material to fire in the case of a calamitous accident. A large variety of tools and equipment may operate in the CPR, including production tubing and possibly an inner casing.

CPR Requirements

The project team has developed a Functional Specification and Performance Criteria document which provides guidance in the production and demonstration of a CPR joint. It is intended that the CPR be fully ready for use by the offshore industry at the completion of the project. Functionally, the CPR must perform the same duties as a steel riser casing.