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

Risk Assessment of Subsea Pipelines by Impacts of Dropped Anchors Based on AIS Data
Jian Zhou1, Zheng Huang1, Feng Yin2, Zhong Li2, Yanbo Liu1*
1College of Shipbuilding Engineering, Harbin Engineering University, Harbin, China
2CNOOC Research Institute, Beijing, China

gives methods to calculate the damage degree of subsea pipelinesimpacted by falling objects, which provides a basis for the risk
assessment of subsea pipelines by impacts of dropped anchors. With
this method, Ariany (2020) performed risk assessment on subsea
pipelines by dropped and dragged anchors.

ABSTRACT
Impact damage from dropped anchors poses a great threat to the safetyof subsea pipelines. Risk assessment by impact of dropped anchors isimport for the protection design of subsea pipelines, which usually
involves the estimation of the impact frequency and the corresponding
damage degree. Although DNV provides recommended practice forcalculation of the impact frequency and impact capacity, there is stilllack of method to take account of ship traffic and anchoring
information in different areas. In this paper, a risk assessment methodon subsea pipelines by dropped anchor is proposed based on
information from AIS data. The impact frequency was calculated andthe corresponding damage degree was classified. The method proposedin this paper could provide assistance in improving the risk assessmentof subsea pipelines.

In recent years, AIS data have been widely used in ship and ocean
related research. Chen (2020) proposed a convolution neural network
method for ship motion classification based on AIS data. Zhou (2019)used AIS data to study ship classification based on ship behavior
clustering. Hu (2021) proposed a model for calculating the impact
probability of subsea pipeline anchoring and trawling based on AIS
data, which can be used to calculate the impact frequency in statisticaltime, but there is no in-depth analysis of the damage caused by impact.
Although the damage degree on subsea pipelines could be calculatedusing the recommended by DNV, however, there is no constant method
to decide the input parameters such as the impact frequency as well as
the weight of anchors in the target sea area. In this paper, a risk
assessment method for subsea pipelines based on AIS data is proposed
to comprehensively analyze the impact frequency and damage degreeof by dropped anchors. The AIS data was obtained in the area locatedin South China Sea and the anchoring points of ships in the target sea
area were identified. The frequency of subsea pipelines anchoring iscalculated and the damage level of subsea pipelines caused by eachanchoring is analyzed. Finally, risk assessment of subsea pipelines byimpacts of dropped anchors was performed based on the calculated
impact frequency and damage degree.

KEY WORDS: Subsea pipelines; anchoring; risk assessment; AIS
data

INTRODUCTION
In the offshore oil and gas production system, subsea pipeline is widelylaid on the seafloor for the transportation of oil and gas. With theincrease of ship traffic and number of subsea pipelines, pipeline
damage caused by third-party interferences is also increasing. It has
been reported that 50%~60% (2014) of the rupture accidents of subsea
oil and gas pipelines in the world are caused by third-party damage,which mainly includes the impact of falling objects at sea, offshore
engineering construction, fishing boat trawling and ship anchoring
operations. In recent years, damage from dropped anchors has become
one of the main risks to the safety of subsea pipelines.

AIS DATA PRE-PROCESSING
The automatic identification system (AIS) is an automatic tracking
system that uses transceivers on ships and is used by vessel traffic
services (VTS), which is usually used in the fields of ship navigation
supervision, ship collision avoidance and auxiliary pilotage. The AIS
data transmitted by this system contains ship navigation informationsuch IMO number, vessel name, position, etc. In this paper, ship
dynamic information such as ship position, navigation speed and shipBrown (1972) studied damage risks of pipelines by impacts of dragging
anchors and fishing boards. Chung (1996) studied the response anddeformation of free-span pipeline under impact load. Al-Warthan (1993)
studied pipeline responses to the impact loading types. Tawekal (2019)studied the maximum equivalent stress and depression depth by impactof anchors using ANSYS software. The DNVGL-RP-F107 (2017)3244