Design Consideration for Composite Drilling Riser
Authors: Salama Mamdouh M. , Murali Jagannathan , Baldwin Donald D. , Jahnsen Ove , Meland Thor 
Published: October 2008

Abstract
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.

Introduction
High pressure composite drilling risers have the potential of reducing capital expenditure and improving reliability for the development of reservoirs in deepwater using TLPs and SPARs. Due to the severity of service performance requirements, the qualification of composite drilling risers paves the way for broader applications such as production risers, tubings etc. whose performance requirements are less severe. In order to confirm the advantages and secure operational staff confidence in composite drilling risers, field testing of a drilling riser joint is necessary. The project described in this paper is intended to design, fabricate and qualify a prototype composite drilling riser joint designed to be compatible in all respects with the 558 mm ID (22 in.), high pressure titanium drilling riser system currently operational on the Heidrun TLP. Upo