2001-2002 OTRC Project : Comparative Risk Analysis of Spar-Based FPSO’s
OBJECTIVE:
Complete the comparison of risks for a spar-based FPSO’s with other deepwater production systems for the Gulf of Mexico, and participate in a Workshop on Marine Risks Associated with Floating Production Systems that will be conducted by the International Association of Oil & Gas Producers (OGP) in the UK in 2002.
APPROACH:
The methodology and data developed for the recently completed Comparative Risk Analysis of Deepwater Production Systems project is being used as a basis for estimating the risks of a Spar-based FPSO in the Gulf of Mexico. The risk measures are again fatalities (human safety) and oil spills (environmental safety). This study is using existing data and involving expert opinion from industry and regulatory agencies (MMS and USCG) to assess hazards and risks. The risks measures are being developed for the various components and operations and will be used to determine the overall system risks. This study was initiated in the Spring 2001 with 2000-2001 funds. Industry experts have been identified, and the issue of handling wet oil in the Spar storage tanks has been identified as an issue that needs to be considered in addition to all other systems, components, and operations studied in the previous CRA study. Information is being gathered, and a workshop process will again be used to mobilize industry expertise to assist in defining risks and to develop and review data, assumptions, and results.
Results from this study, the recently completed Comparative Risk Analysis of Deepwater Production Systems project, and other ongoing OTRC research (e.g., Mooring and Riser System Risks, Suction Caissons and Vertically-Loaded Anchors, deepwater riser studies) will provide the basis for our active participation in the OGP Workshop. This participation will enable the more global sharing of ideas amongst the engineering and regulatory agencies, and provide useful input and insight for future OTRC research.
DEPLOYMENT OF RESULTS:
Results of the CRA for Spar-Based FPSO’s will be documented in a report that will be publicly available. This information should facilitate regulatory and industry discussions and decisions in advance of actual project proposals. The OGP Workshop will be documented in a brief summary report to the MMS on our participation in the Workshop. The report will complement the OGP report, and will highlight learnings from the OGP Workshop and compare the OGP Workshop results with the prior MMS sponsored CRA studies for the Gulf of Mexico. The OGP Workshop results may influence ongoing or future OTRC research projects being sponsored all or in part by the MMS.
ANTICIPATED PROJECT DURATION: 1 year
PROJECT PLAN FOR YEAR 1 (2001-2002):
Scope of Work: The Spar-based FPSO system description will be developed that has similar functional requirements and capacities as the TLP, Spar, and tanker-based FPSO considered in the previous study. Two focused workshops with invited experts will be held to solicit information and opinions to (1) identify hazards; (2) determine frequencies and consequences of adverse events; identify needs and options to mitigate potential risks; and review QRA results. The project report will be offered to workshop participants for review prior to finalizing. Participate in the OGP Workshop, and write a brief report to the MMS summarizing major learnings and conclusions.
Anticipated Results: The final report on the CRA for a Spar-Based FPSO will document the system, component, and operational risks plus the overall risks for a Spar-based FPSO, and compare these risks to those of other deepwater development systems for the Gulf of Mexico. A report on the OGP Workshop will summarize our participation in the Workshop and major learnings and conclusions.
SPONSORSHIP: MMS
PRINCIPAL INVESTIGATOR (S) & OTHERS INVOLVED IN PROJECT:PI(s): Robert B. Gilbert, E.G. Ward
Date: December 2002Project Name: Comparative Risk Analysis of Spar-Based FPSO’s
Project Number: 32558-5888C Task Order: 18047
Principal Investigators: R.M. Gilbert and E.G. Ward
Estimated Completion Date: May, 2003
Project Description:
Compare risks for a spar-based FPSO with other deepwater production systems studied in the Comparative Risk Analysis of Deepwater Production Systems for the Gulf of Mexico. Those systems were a tanker-based FPSO with wet trees; a conventional Spar with dry trees; a TLP with dry trees; and a shallow-water jacket serving as a hub and host for deepwater production.
The spar-based FPSO configuration studied was a spar with wet-oil storage, dry trees, oil export by shuttle tanker, and gas export by pipeline. Wet-oil storage was the major system aspect that was different from the previous studies. In a wet-oil storage system, the oil is stored together with sea water in compartments in the spar’s hull, and the oil/water interface moves up and down during production and offloading. In order to assess the risks associated with this type of oil storage, data were compiled and analyzed from the North Sea where both spars (the Brent spar) and gravity-based structures have used wet-oil storage. Information on oil spills was obtained directly, and information on the volume stored and the number of offloading events was inferred. Oil-spill risks were measured as the average value for the total volume of oil spilled during the operational lifetime for a fleet of systems, as before in the original CRA project.
Progress:
Results indicated that oil spill risks for a spar-based FPSO with wet-oil storage are comparable to those for dry-oil storage in a tanker-based FPSO. In both cases, the major contribution to the oil-spill risk is related to shuttle-tanker offloading and transportation.
The oil spill risks for the spar-based FPSO were also compared to the conventional spar with an oil pipeline. The frequency distribution of the total volume spilled was estimated for each system, and the expected values for different lifetime spill volumes indicated:
§ The majority of spars operating for 20 years in the GOM will have a total volume spilled less than 1,000 bbl over their lifetime, regardless of the method of oil transport.
§ A total volume spilled greater than 100,000 bbl is extremely unlikely for either type of spar.
§ For the spar-based FPSO, there is less chance for a spill larger than 1,000 bbl (less than 20 percent), although a small possibility exists (less than one percent over the lifetime) for a spill between 100,000 and 500,000 bbl.
§ For the spar with an oil pipeline, there is a greater chance for a spill larger than 1,000 bbl (about 30 percent), while there is essentially no possibility for a spill greater than 100,000 bbl in size.
The magnitude of uncertainty in the estimated volume spilled is larger for a spar-based FPSO than for the conventional GOM Spar due to the lack of information. However, it is essentially impossible to meaningfully distinguish between the oil-spill risks for a spar-based FPSO versus the conventional spar with an oil pipeline (or the other production systems studied) due to the large magnitude of uncertainty in the estimated volume of oil spilled.A concerted effort was made to better understand the practical consequences of uncertainty in the estimated oil spill volumes and to evaluate how much future information would be required to meaningfully reduce this uncertainty. A plot of the standard deviation in the total volume spilled versus the number of spar-years of data shows that more than 10,000 spar-years of experience (for example, 500 spars operating for 20-years (each) would be required to begin reducing the standard deviation in the average spar performance enough to be able to distinguish between different systems for oil transportation. This result occurs because the average value for the total volume spilled is dominated by the possibility of large but rare spills.
Reports & Publications:
Chemadurov, E. (2002), “Risk Analysis of Oil Storage on Spars in the Gulf of Mexico,” M. S. thesis, Department of Civil Engineering, The University of Texas at Austin.
OTRC PROJECT STATUS REPORTProject Name: Comparative Risk Analysis of Spar-Based FPSO’s
Task Order: 18047 Project Number: 5888C and 5888C1
Principal Investigators: Bob Gilbert and Skip Ward
Estimated Completion Date: August, 2002
Project Description:
Complete the comparison of risks for a spar-based FPSO’s with other deepwater production systems for the Gulf of Mexico, and participate in a Workshop on Marine Risks Associated with Floating Production Systems that will be conducted by the International Association of Oil & Gas Producers (OGP) in the UK in 2002.
Progress:
· Compiled data from North Sea (Norwegian and UK sectors) on performance of wet-oil storage systems with shuttle tanker offloading. Data have been obtained for oil spills. Currently tracking down information on the exposure to spills, including the number of facilities, the number of years of operation, the total barrels of storage, and the number of lifts.
· Developed a model to conduct Monte Carlo simulations of oil spills and fatalities to (1) check the validity of assumptions that were made in developing the analytical approximations used in the original work; (2) to provide material to illustrate what the results mean in terms of actual systems; and (3) to understand how much future information will be required to meaningfully update the results from this study.Reports & Publications:
Chemadurov, E. (2002), “Risk Analysis of Oil Storage on Spars in the Gulf of Mexico,” M. S. thesis, Department of Civil Engineering, The University of Texas at Austin, to be completed in August, 2002.
OTRC Project Status Report
Project Name: Comparative Risk Analysis of Spar-Based FPSO’s
Task Order: 18047 Project Number: 5888C and 5888C1
Principal Investigators: Bob Gilbert and Skip Ward
Estimated Completion Date: August, 2002
Project Description:
Complete the comparison of risks for a spar-based FPSO’s with other deepwater production systems for the Gulf of Mexico, and participate in a Workshop on Marine Risks Associated with Floating Production Systems that will be conducted by the International Association of Oil & Gas Producers (OGP) in the UK in 2002.
Progress:
1. Compiling data from North Sea (Norwegian and UK sectors) on performance of wet-oil storage systems with shuttle tanker offloading. Data have been obtained for oil spills. Currently tracking down information on the exposure to spills, including the number of facilities, the number of years of operation, the total barrels of storage, and the number of lifts.
2. Developing a model to conduct Monte Carlo simulations of oil spills and fatalities to (1) check the validity of assumptions that were made in developing the analytical approximations used in the original work; (2) to provide material to illustrate what the results mean in terms of actual systems; and (3) to understand how much future information will be required to meaningfully update the results from this study.Reports & Publications:
Pending: One project report and one M.S. thesis