Risk Assessment of a Tanker Based Floating Production Storage and Offloading (FPSO) System in Deepwater Gulf of Mexico
Authors: Karsan Demir I. , Aggarwal Rajiv K. , Nesje Jon D. , Bhattacharjee Subir , Arney Cyril E. , Haire Bill M. , Ballesio Jorge E. 
Published: October 2008

Floating Production, Storage and Offloading (FPSO) systems are gaining significant consideration for deepwater oilfield development in the Gulf of Mexico (GOM). The risks associated with a FPSO system differ from those for the existing systems such as the conventional steel jacket, compliant tower, TLP, and SPAR.

The first phase of a Joint Industry Project (JIP) focused on the evaluation of risks associated with the production operations from a GOM FPSO. The JIP objectives included demonstration of the acceptability of a FPSO in the GOM; identification of accidental events and FPSO components with high environmental pollution, loss of life, and financial risks; and recommendation of reasonably practicable risk reducing measures. The JIP was sponsored by 10 oil companies, 3 FPSO contractors, 4 certification agencies, and MMS. The risk assessment work was done on a converted tanker FPSO concept developed for the GOM by a major oil company.

This paper focuses on the key safety issues that are important for the development of FPSOs in the GOM. The hazards evaluated and various risk assessment tasks undertaken in the JIP are briefly discussed and important issues are highlighted. Additionally, the potential differences in risks from a system using a new-built vessel are identified.

The JIP has helped to better understand the safety of FPSOs in the GOM by determining the potential improvements to layout, design, operational, and mitigation measures.

Introduction

Currently, there are at least 45 FPSOs installed worldwide but none in the US GOM. These are operating in both benign and extreme environments, and have different configurations and designs. Most are conversions from single hull tankers. Majority in the North Sea is new-built with double hulls [1]. The recent installations indicate that the industry confidence in producing from FPSOs is on the rise, and they are now being installed in harsher environments and deeper waters, as permanent and larger production units.

Figure 1 identifies the areal extent of existing platforms and the pipeline infrastructure in the US GOM and the current deepwater offshore leases. There are over 4,000 offshore platforms and about 20,000 miles of pipelines of various sizes installed in the US GOM. The majority of the GOM production facilities are supported by steel jacket platforms, tripods, or caissons in water depths up to 1,000 ft. There are a few steel jacket platforms in water depths exceeding 1,000ft.

MMS defines the deepwater zone as tracts with water depths exceeding 1,000 ft. Approximately 10 production facilities using novel technology systems such as the guyed/compliant tower, tension leg platform, and SPAR have been installed in water depths up to 4,000 ft. All of the existing platforms utilize pipelines, which transport the produced oil and gas to an existing pipeline network or directly to shore facilities. Existing GOM pipeline and platform infrastructure covers up to a 130-mile wide strip reaching to the 650-ft. water depth contour from North Padre Island to Viosca Knoll. In some areas, this network extends to nearby installations in water depths deeper than 1,000 ft. All current deep water platforms are located reasonably close to an existing pipeline network and do not require offshore storage and/or shuttle tanker transportation of produced oil. MMS have recently awarded a significant number of deep and ultra-deepwater leases that extend to 10,000-ft water depths [Figure 1]. Existing pipeline network is generally far away from most of these recent leases. Seabed topography is also more complex than what is encountered in the currently developed areas. In some western regions of the GOM, the fields in 4,000 ft to 10,00