position of the Offshore Technology Conference or its off~cars. Electronic reproduction, distri-but~on, or storage of any part of this paper for commercial purposes without the written consent of the Offshore Technology Conference IS prohibited. Permission to reproduce in print is restricted to an abstract of not more than 300 words; illustrations may not be copied The abstract must contain conspicuous acknowledgment of Were and by uhom the paper was presented Abstract A concentrated effort is underway to design a Composite Production Riser (CPR) and demonstrate its suitability 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. Riser responses to platform motions and environmental loads have been provided based on global analysis of a TLP system.The use of well established advanced composite stuctural design methodologies has resulted in a CPR design with predicted capabilities that exceed the expected loadings. The design of the CPR joint requires three separate efforts: composite tubular design; composite-to-metal interface design; and metal connector design. The composite tubular wall is a hybrid composite structure, with carbon fiber and glass fiber reinforcements in an epoxy matrix. The composite-to-metal interface is a multiple traplock configuration, well-suited for supporting axial and pressure loadings. A premium threaded connection is used for the metal connector design.The performance of the CPR will be verified through testing of subscale and full-scale specimens. Preliminary results of this testing are discussed.The CPR design effort demonstrates the ability of engineering functions from diverse industries, institutions and companies to work together to obtain a common goal.

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. The objective of the effort is to arrive at a costeffective design for a composite production riser that meets reliability performance of current metal systems. An integrated CPR design meeting the project cost, weight and performance goals was developed. A test program was defined to derive statistically sufficient 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 80 prototypes were fabricated and tested for ultimate strength determination, static and cyclic fatigue performance, and characterization of damage tolerance. A primary purpose of this testing was to correlate and analyze riser joint actual performance with predicted values, in the interest of verifying static and cyclic performance and manufacture variability. The final results of this testing and analysis are presented in this paper. Introduction As competition for oil increases, oil companies are drilling in deeper waters. Current deepwater oil completion and production technology utilizes steel riser systems that are heavy, require expensive tensioning and buoyancy systems, and whose designs are often governed by fatigue considerations. Composite risers would provide advantages over conventional steel risers because composite materials are (1) lighter weight, (2) more fatigue resistant, (3) more corrosion resistant, (4) can be designed for improved structural and mechanical response, and (5) are better thermal insulators. Overall, production platform cost reductions are possible as a result of the lower weight and greater compliance of composite risers, along with improvements in system reliability. A CPR has the potential of reducing capital expenditure, 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 tensioning system, resulting in further cost benefits to the riser system and platform construction. Background 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 several years. The Institut Français du Pétrole (IFP), Aerospatiale, and several major oil companies sponsored a development and evaluation study of a 9 5/8-inch diameter CPR to prove the concept. The study was conducted between 1985 and 1990 (see Refs. 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 (1,012,500 lbs). The CPR was also designed for a maximum external pressure (differential) of 10 MPa (1430 psi). The study included several static, fatigue, multi-axial loading and damage assessment tests.

High pressure drilling risers represent the most challenging application for composite materials in the offshore industry. Therefore, their successful field qualification should serve to eliminate the emotional barriers and pave the way for the broad usage of composites in similar but less demanding applications such as production risers, catenary risers, tubings, etc. The primary goal of the project discussed in this paper is to demonstrate the technical feasibility and cost effectiveness of advanced composite materials for high-pressure drilling risers. This is achieved by the design, manufacture, qualification, certification and field testing of a 558 mm ID (22 in.) composite drilling riser joint on Heidrun Tension Leg Platform (TLP) A composite drilling riser (CDR) joint is designed to be interchangeable with the Standard Titanium Drilling Riser Joints (STDRJ's) currently in use on the Heidrun platform. The CDR joint has identical flange configurations as the titanium joints and is designed to satisfy all dimensional constraints to make it suitable for installation on Heidrun. The tube body weight of the CDR joint is 87 lb/ft versus 130 lb/ft for an equivalent Ti joint. The fatigue life of the CDR joint exceeds 150 years (10 times the 15 year service life), and its internal pressure rating exceeds 12,600 psi, which is about 2-¾ times the maximum operating pressure of 4500 psi. In addition, the CDR joint, without the need for any special impact protector, maintains its pressure and structural integrity after being subjected to a dropped object impact of 50kJ.The structural capability of the CDR tube body is provided by a carbon fiber/epoxy composite overwrap, with load transfer between the composite overwrap and Ti flange extensions accomplished through a carefully designed traplock Metal-to-Composite Interface (MCI). Detailed analysis of the CDR joint confirmed that it is capable of safely supporting all of the expected loadings, including internal and external pressures, axial tension, bending moments, and impact loads. The bore of the CDR joint is provided with a 0.125-inch (3.2 mm) Ti liner welded to the flanges for fluid-tightness and damage resistance, and an elastomeric wear liner identical to the one currently in use on Heidrun. The design, analysis and qualification of the CDR joints have benefited from the design and the extensive qualification activities on the 10-¾ inch high pressure composite production riser joints as part of the NIST ATP project.The paper summarizes the performance requirements called for by Heidrun TLP Drilling Riser System, and presents the design and analysis procedures and results to ensure that the composite riser joint satisfies all requirements. The paper reviews the basis for the analysis and the validation of its accuracy, and presents the rationale for the qualification program.

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 perfonnance 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 perfonnance of current steel systems.Well-established design methodologies for advanced composite structures have resulted in a CPR design meeting the project cost, weight and perfonnance 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 perfonnance with analysis predictions, in the interest of verifying static and cyclic perfonnance 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-tenn perfonnance of the CPR. A total of 68 prototypes are to be fabricated and tested for ultimate strength detennination, static and cyclic fatigue perfonnance, and characterization of damage tolerance. A status report of the testing and analysis is reported in this paper.

This paper provides an overview of how design and qualification testing of rigid composite risers can be accomplished using performance-based requirements. The successful qualification of composite pressure vessels for use as energy accumulators on riser tensioning systems is used as a model. Technique discussed applies to design and qualification of composite tubulars used as production risers, workover and intervention risers, drilling risers, auxiliary lines (choke, kill, booster, and hydraulic), drill pipe, casing and production tubulars. Performance-based qualification requires design analysis, manufacturing development and qualification testing. Determination of minimum Factor of Safety for composite structures should be based on standard reliability analysis that considers the stress rupture behavior of the selected reinforcement.