Systematic Analysis of Operational Safety of FPSOs Reveals Areas of Improvement

Abstract

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractFloating installations in general and FPSO systems in particular, combine traditional process technology with marine technology, and are thus quite dependent on operational safety control. It is essential that scenarios involving potential loss of operational control are assessed at an early stage in the design of new facilities, in order to optimise technical and operational solutions. The paper briefly reviews the safety characteristics and records for FPSOs, focusing on operational safety aspects. This is followed by a discussion of possible approaches to predictive assessment of operational safety.

Risk analysis of collisions during FPSO offloading operations

“…has devoted to the research of the collisions during offloading. In 2003, UK Health Safety Executive (HSE) [16] , presented a public report on effective collision risk management for installations; In 2000, the safe operation of FPSO JIP was presented by Vinnem [17] ; In 2002, UKOOA (United Kingdom Offshore Operators Association) guidelines on the offloading in tandem, has contributed a lot to the risk control of offloading collisions. Also MacDonald, Blom et al have done a lot of research aiming at the collision risks between FPSO and ST.…”

FPSO Environmental-Risk Management

“…The oil and gas industry's joint industry research and development program called Operational Safety of FPSOs conducted between 1997 and 2001, according to a 2000 SPE paper (Vinnem et al 2000), was a systematic analysis of the operational safety aspects employing predictive analysis to reveal areas in need of improvement. Before that study, in 1997, the UK HSE published a report titled Close Proximity Study (UK HSE 1997) that assessed the risk of collision during close proximity operations involving shuttle tankers at offshore locations.…”

“…A joint-industry study conducted by Statoil, ExxonMobil, UK HSE, and others researched and modeled FPSO risk to personnel as well as to the environment (Vinnem et al 2000). The safety aspects modeled included…”

“…The joint-industry study (Vinnem et al 2000) draws important conclusions on types of failure (human, operational, technical, material, and environmental) and failure modes that must be considered in risk assessments early in the design to ensure proper inclusion of risk-reduction measures in design and operational planning. It confirms the absence of major environmental releases associated with more than 20 years of FPSO operation around the world through 2002.…”

“…Hull configuration (double-sided or hulled), with ballast tanks on outside to provide collision protection Turret moored instead of spread-moored Turret equipped with swivel Mooring design to minimize risks from line failures Thrusters for active heading control during tandem offloading and to compensate for anchor line failure Fenders to provide collision protection Corrosion protection of tanks Flexible riser design and integrity; external and internal sheaths Using state of the art ESD valves/systems and configurations for risers (ESD valve on each riser) and offloading hose and protecting them from possible impact (blasts, etc) Connecting risers via I-tubes located in the FPSO ballast wings to reduce the risk related to potential ship collision; lining risers with nylon Large hydrocarbon inventories have spill containment and drainage, foam blanketing and deluge cooling of vessels High velocity cargo tank vent systems able to limit the potential for explosive and toxic gas atmospheres on the process and main deck levels of the FPSO Using solid decking on FPSO to contain liquid releases; grated decking is better for avoiding gas leak confinement FPSO Operation Offloading buoy (located two km or more from the FPSO to reduce risk of ship collision) instead of tandem offloading (stern of FPSO to bow of tanker is usually in the range of 50 to 110 m) Establishing exclusion zone around FPSO, monitored and enforced by means of a long range radar control system onboard the FPSO to detect and monitor ships, fishing boats, and other small crafts in the area Dedicating a multi-purpose marine support vessel (MSV) for service on standby in the project area at all times, to act as collision guard, provide rapid response to an oil spill and to help maneuver disabled vessels (tankers, supply vessels, etc); the exclusion zone would be patrolled by the MSV Using dynamic positioning (DP) powered shuttle tankers (rated DP systems) for station keeping and maintaining safe distance from FPSO Protecting flexible risers, monitoring sheath degradation and mooring line integrity: 95% of the mooring requirement is to protect the riser Ensuring crew competence Limiting size/weight of vessels approaching FSO Imposing weather/sea state limits of operation Installation of waste heat recovery units in lieu of fired heaters to reduce ignition sources (and emissions) (Haughie and Duncan 2006) Shielding of risers and subsea flowlines to protect against dropped objects from cargo handling or other activities; establish cargo handling zones Risk Management Systems Conducting Safety Case (Haughie and Duncan 2006;Browning 2004) or other quantitative risk assessment (QRA) on the proposed FPSO, early during the FEED, including all critical failure modes, i.e., human, technical and environmental (Vinnem et al 2000); base assessments on a comprehensive Hazard Register Maintaining high level of crew competence, through training and drills (Vinnem et al 2000) Maintaining best practice fire and explosion protection and suppression equipment and procedures associated with hydrocarbon handling: storage of crude in the FPSO cargo tanks as well as offloading; this includes emergency shutdown and quick release of the offloading hose (Vinnem et al 2000) Conducting annual assessment using a subsurface remotely operated vehicle of FPSO hull and seabed installations (Sakhalin Energy Investment Company 2005a) Conducting riser and mooring system condition monitoring program (Overfield and Collins 2000;UKOOA 2001…”