Collision Risk Analysis of FPSO-Tanker Offloading Operation

Abstract

Collision between FPSO and shuttle tanker in tandem offloading operation has caused a growing concern in the North Sea. Several recent contact incidents between FPSO/FSU and shuttle tanker have clearly demonstrated a high likelihood of contact between vessels in tandem offloading. The large masses involved, i.e. high potential impact energy, make the collision risk large. Traditional ship/platform collision risk model may not be effective for tandem offloading operation. Further more in a broader sense, offshore quantitative risk analyses generally focus more on technical aspects, little on human aspects. This leads to a hardware-centered risk control approach, which may not be effective in the face of risks in complex marine operations.A collision risk modeling approach for FPSO and tanker offloading operation is presented in this paper. The collision frequency is modeled in the initiating stage and the recovery stage. In the initiating stage, this paper is focused on tanker powered forward movement (PFM) scenarios. The initiation of tanker PFM involves a complex man machine interaction. The risk model is set up which integrates technical events, human actions and their interaction in the initiating stage. This model guides us further to identify the two failure prone situations where man machine interaction happened and resulted in most collision incidents. The study to quantitatively analyze these failure prone situations and minimize their occurrence is presented in a companion paper OMAE 28101. In the recovery stage, this paper is focused on the tanker initiated recovery. Based on the proposed probabilistic model for the recovery stage, possible recovery actions are identified and the event development is modeled from initiation of tanker PFM to the final outcome, i.e. collision or near miss. The success of recovery is analyzed from the human action timing perspective. Based on qualitative and preliminary quantitative analyses, recommendations are made to reduce the failure of recovery in design and operation.

Risk analysis of collisions during FPSO offloading operations

“…A separate model is required to evaluate the collision risks when offloading in tandem beside the traditional boat or platform collision model. Chen and Moan (2002, 2004 [9][10][11] discussed the risks existed in the process and emphasize the complexity of human-computer interaction when shuttle tanker move to the end of FPSO, also human factors are taken into account. With the preliminary qualitative and quantitative analysis, Chen and Moan proposed the measures to reduce the failures through design and operation, and the criteria to reduce the failures are recommended, including increasing the operating time and reducing the operator response time.…”

“…However, malfunction of DP software caused an error of flow judgment and result in a signal to the propeller, which set the propeller forward to balance the nonexistent flow, which driven ST forward. 9 As the imaginary signal of five knots velocity detected by DP system, the command signals were sent to main engine and propeller, which result in forward propulsion to compensate the imaginary flow and this driven ST forward. 10 As the main propeller failure caused by servo system error, DP operator reselect the main propeller and input the DP system.…”

Use of fuzzy risk assessment in FMEA of offshore engineering systems

“…According to the literature survey, a technical failure that might cause collisions between the FPSO and a shuttle tanker during tandem offloading operations is a malfunction of the propulsion system. The four major causes to this technical failure are controllable pitch propeller (CPP), thruster (T), position reference system (PRS) and dynamics positioning system (DP) failures [6].…”

Self-tuning of fuzzy belief rule bases for engineering system safety analysis

“…The FURBER framework (Liu et al 2004) has been applied to modelling system safety of an offshore and marine engineering system: a floating production storage offloading (FPSO) system (Chen and Moan 2002;McCaul 2001), with special focuses on collision risk between FPSO and a shuttle tanker due to technical failures during a tandem offloading operation.…”

“…According to the literature survey, the technical failures that might cause collisions between FPSO and a shuttle tanker during tandem offloading operations are malfunction of propulsion systems (Chen and Moan 2002). The four major causes to the technical failures are:…”