Session: 04-02-02 Rigid Risers II

Paper Number: 101969

101969 - Design Drivers for Pre-Lay and Recovery Installation of Deep Water Steel Lazy Wave Riser Systems 

Wet storage of risers prior to installing them on the vessel is generally done to make the installation schedule more flexible especially in harsh environments with small weather window. The wet storage of flexible, umbilical or steel with a traditional catenary configuration has become quite common. However more increasingly steel lazy wave riser systems (SLWRs) are also being wet stored  in a few recent projects.

Most recent projects prefer to wet park the SLWRs for a short duration before installing them onto the vessel.   One of the challenges that has emerged in doing so is devising a suitable configuration for SLWRs wet parked with a tight field architecture and extreme currents. The proposed wet park configuration must be installable and robust enough to avoid interference with surrounding wet parked risers, and avoid excess stresses and high VIV damage during the period of wet park.  Even though some international standards like DNV-OS-F201 recommends addressing pre-lay strength and fatigue for compliant riser systems, such standards do not provide a clear methodology .

The aim of this paper is to establish a detailed methodology and discuss feasibility aspects of the wet park design for a generic SLWR example in 7,000 ft of water depth.  The major design drivers and technical challenges involving wet park configuration, laydown, recovery and transfer during installation is discussed. The steel lazy wave riser wet park stability and fatigue, and transient response of wet parked risers during flooding and dewatering are evaluated from an analytical aspect. The riser wet park stability, wet park clashing checks, extreme strength during wet parked period and fatigue due to vortex-induced vibrations (VIV)  during the duration of wet park are investigated for a pre-laid dual loop SLWR system. 

Presenting Author: Abhilash A. Sebastian TechnipFMC

Presenting Author Biography: Senior Principal with twenty four years of experience in management and engineering. Extensive experience in deep water engineering management, Interface management and Project management for deep water projects. Expert level experience in deep-water riser design and analysis, riser installation, EPC costing and naval architectural design and analysis. Detailed engineering experience in Free Standing Hybrid Risers, Lazy Wave Risers, Flexible Risers and Steel Catenary Risers design.

Past positions include Rigid Riser Technical Authority for Subsea Group, Supervisor for Rigid Risers Group, Interface Manager, Engineering Manager, Deputy PM etc...

Organizational experience of managing riser functional team of 20 engineers. Managed their workload, project assignment and utilization for the team. Developed scopes of work and budgetary estimates for the team. Monitoring of employee performance, employee feedback, training and career growth for employee’s part of the duties. In addition to above duties, was also responsible for developing business strategies for group.

Authors:

Abhilash A. Sebastian TechnipFMC
Jaehyeuk Jeon TechnipFMC
Vikas Patel TechnipFMC
Mayank Lal TechnipFMC