Common Sense Requirements (CSRs) for Steel Catenary Risers (SCRs)

Abstract

Abstract This paper deals with some of the issues that were encountered during the design and construction of the steel catenary risers (SCRs) for the Prince Project in Ewing Bank Block 1003 in water depth of approximately 1500 ft in the Gulf of Mexico. The SCRs are two 12 inch oil and gas export SCRs to transport the oil and the gas from the Moses TLP to a connection into pipeline systems on the shelf in shallower water. The Prince SCRs represent a leap in the SCR applications by having many firsts in the industry. They have been designed and installed for less than 1500 ft water depth that represents the shallowest water for SCRs so far, breaking Morpeth SCR's water depth record of 1670 ft. The Prince SCRs had the largest departure angle of 24 degrees and FlexJoint angle variation of +/-20 degrees to accommodate the TLP motion in such relatively shallow water depth. The VIV strakes are the first to be pre-installed on the SCR pipes during an S-lay operation. The main issues that every designer and owner should be aware of during the design, procurement, fabrication and installation are SCR geometry and configuration, material selection, welding and other contracting aspects, particularly the interface requirements and installation methods. The Prince project has provided a great opportunity for uncovering many of the details that require close attention to avoid delays and mishaps during the typical accelerated schedule of nowadays projects and to ensure proper design in accordance with applicable design codes and industry standards. This paper will focus on the lessons learned during the execution of the Prince SCRs activities and help the industry with better understanding for the issues that should be and could be considered as common sense. Introduction Steel Catenary Risers represent one of the most significant challenges ever encountered by project teams designing and constructing deepwater marine pipeline systems. Contracting philosophy and interfacing of disciplines go hand-in-hand to achieve timely completion of pipelines incorporating SCRs. All pipeline facilities share common ‘building blocks’: design and engineering, material specification and procurement, and installation. These building blocks have to be integrated when constructing SCRs. The Prince SCRs project was a model for team integration and cooperation among all parties involved. The Prince SCRs also introduced many firsts in the industry that without the teamwork and close relationship between the management, the design engineers and the suppliers would not have been achieved. These first include the following:The Prince SCRs are the first to be installed in water depth less than 1500 ft.The Prince SCRs are the first to have large departure angle of 24 degrees connected to the TLP hull by flexible joints (FlexJoints) with angle variation of +/- 20 degrees, which is another first.The Prince SCRs are the first to have VIV strakes preinstalled during the S-lay operation of the SCR pipes. The VIV strakes have to go over the S-lay vessel stinger and suffer some deformation before bouncing back after leaving the stinger. This paper presents the highlights of the Prince SCRs project and discusses in more details the relationship factor that played a significant roll in the success of the project. Design and engineering, material specification and procurement, and installation issues are also presented. Design/Engineering Issues Engineering design represents an early project contracting philosophy. Catenary risers are attached to and suspended from a floating hull.