Proceedings of the Thirty-second (2022) International Ocean and Polar Engineering Conference
Shanghai, China, June 5–10, 2022
Copyright © 2022 by the International Society of Offshore and Polar Engineers (ISOPE)
ISBN 978-1-880653-81-4; ISSN 1098-6189

www.isope.org

Global Extreme Strength Analysis on Specialized Hang-off Joint System for Deepwater Drilling Riser
Jinlong Wang
Drilling & Production Research Department, CNOOC Research Institute Ltd., Beijing, China

ABSTRACTdevastating consequences.

Offshore drilling activates have been significantly impacted by severe
weather conditions as oil and gas development has moved into deeperwater. Under the situation of imminent arrival of a typhoon, emergency
retrieval of the whole drilling riser string is time consuming and tedious.
A specialized soft hang-off system to improve the adaptability of thedrilling riser system under hang-off operations is developed to solve thelow-efficiency and time limitation for retrieval all drilling riser joints
during in extreme storm environment. By using the hang-off joint andhydraulic compensation systems, the device can perform the dynamic
compensation of the riser during typhoon and improve the moonpool
interference performance, so as to greatly improve the safety of drillingriser during typhoon period, and can be applied in transit during crosswells operation with a relatively higher transit speed. Global extreme
strength analysis on deepwater drilling riser hang-off joint system inhang-off operation during extreme storm environment is conducted toconfirm the proposed design of the hang-off system. The various wave
and current load, hang-off length, hang-off arrangement under different
stroke positions (top, middle and bottom) are considered in the global
strength analysis and results discussion is conducted. The novel
concept and system provide safety guarantee during deepwater drilling
operations and is an important emergency equipment for anti-typhoon.

The drilling riser is hung-off on the platform and then transited to thesafety area. There are two conventional riser hang-off modes: hard
hang-off and soft hang-off whose stack-ups are illustrated in Fig. 1. For
hard hang-off mode, the top of riser joint is directly clamped by thespider to make the riser rigidly connected with the drilling floor and thetensioner is released. The platform motion is directly transferred to thetop of drilling riser. For soft hang-off mode, the riser is suspended at
the tensioner. The platform motion is transferred to the outer barrel ofthe telescopic joint through the tensioner and the dynamic load inducedby the platform motion is compensated passively by tensioner stroke.
The riser is under good stress condition, but there are also operationalrisks when the platform’s heave amplitude exceeds the telescopic joint’
stroke and tensioner’s stroke.

KEY WORDS: Deepwater drilling riser; specialized soft hang-offsystem; hang-off joint; global extreme strength analysis

INTRODUCTION
The frequent typhoon in South China Sea that battered the offshore
facilities (Xu, 2015) have prompted many operators and drilling
contractors to rethink the way their drilling risers are designed for
emergency disconnection and retrieval before the typhoon or hurricane
arrives. When drilling in very deep water depths, retrieval of thedrilling riser is time consuming and tedious; and in emergency
situations like the imminent arrival of a typhoon, the drilling rigs risk
not being able to recover the drilling risers in time before theevacuation of personnel or sailing for shelters, with potentially

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Many researches have been carried out on the safety technology ofdeepwater drilling risers during hang-off and transit operation, such as
the strength and fatigue damage analysis of deepwater drilling risers,riser integrity management, riser monitoring technology (Zhou and Xu,2018), riser hang-off safety analysis technology (Chang et al., 2008;
Sun et al., 2009; Sheng et al., 2015), riser suspension methods anddevices (Sheng et al., 2019), typhoon accident response strategy (Liu etal., 2014), hang-off operation window (Su et al., 2012) and operationparameters (Chen et al., 2012), etc. Dai et al. (2009), Wu et al. (2014),
Qi et al. (2015) and Wang et al. (2021) conducted the global response
analyses of the hard hang-off drilling riser in the extreme seastate
before the arrival of the typhoon by commercial software. Mao et al.
(2019, 2020) conducted dynamic analysis for the drilling riser undernormal drilling and hang-off conditions. Fan et al. (2017) proposed a
dynamic analysis of hang-off drilling riser based on the Euler-Bernoulli
theory considering vessel motion and the combined excitation of ocean
currents, surface waves and ISWs. Song et al. (2019) proposed a newand effective hang-off drilling riser navigation method for improving
drilling efficiency. However, these researches are commonly based on
the existing conventional equipment and there are limitations due to its
natural characteristics. A new concept of soft hang-off is proposed but
the hydraulic system is too complex to manufacture and stay in the