Fast Riser Installation: A Field Proven, Safe and Efficient Riser Pull-in Technology

Abstract

Abstract A technical study of an innovative steel catenary riser (SCR) installation technology is presented in this paper. This installation technology maneuvers the hull through ballasting to align its riser porch with the riser, which is philosophically different from conventional riser installation that relies on an array of tugging winches to catch and pull riser into positions of the riser porches. The technology has been applied to the installation of eight SCRs on the Delta House production semi-submersible (second end) and, subsequently, five tieback SCRs (first end). We demonstrate that equipment arrangement, riser adaptor fabrication, and ballasting process remain the same for both first end and second end operations, resulting in a robust solution for riser installation. The technology has been proven safe in operations and efficient in saving installation time and cost. This paper focuses on the technical aspects of the riser installation technology, from concept development, technical qualification, to numerical simulations. Vessel positioning and riser-hull clearance during all steps of riser pull-in and installation, as well as planning for ballast water transfer required throughout the process, is prepared with an in-house program based on rigid body rotation. Numerical simulations are performed to identify critical stages of the riser pull-in and to examine the clearance from the pull-in wire or the riser to the hull. The dependence of the minimum clearance on a few parameters related to riser installation is determined and discussed. More numerical simulations are performed to assess the vessel motion response and its dynamic effect on riser-hull clearance and to establish environmental limits for riser installation operation. Discussions are provided for potential challenges of the technology when it is applied to different production and export risers in various water depths.