The Risk Assessment of FPSOs Tandem Offloading Operation

Abstract

As the offshore oil and gas industry moves into deeper waters, the need for an effective system to offload crude oil from Floating
Production Storage and Offloading Vessels (FPSOs) to tankers is progressively increasing. Traditionally, offloading of crude oil
from FPSOs to tankers is carried out either in tandem offloading arrangement or by remote Single Point Mooring buoy. Tandem
arrangement is carried out through the use of Dynamically Positioned (DP) shuttle tankers or conventional tankers. The
operation is associated with high level of uncertainty, because it usually operates in a dynamic environment in which both human
and technical interactions might cause possible accidents. This paper analyses the risk of collision associated with tandem
offloading of FPSOs and DP shuttle tankers by adopting formal safety assessment methodology. The first part of the analysis
estimates the likelihood of collision between the two vessels using fault tree analysis (FTA) techniques. The analysis revealed that
human error, environmental force, reference system failure and DP software failure are the significant events that lead to the
collision of the vessels.