EVALUATION OF ALTERNATIVES FOR OFFSHORE PETROLEUM PRODUCTION SYSTEM IN DEEP AND ULTRADEEP WATER DEPTH

Proceedings of the of the ASME ASME 211 211 3th 3th International Conference on on Ocean, Offshore and Arctic Engineering OMAE211 June 19-24, 211, Rotterdam, The Netherlands OMAE211-49978 EVALUATION OF ALTERNATIVES FOR OFFSHORE PETROLEUM PRODUCTION SYSTEM IN DEEP AND ULTRADEEP WATER DEPTH Celso K. Morooka Faculty of Mechanical Engineering Department of Petroleum Engineering University of Campinas Campinas-SP, Brazil Maria Deolinda B. M. de Carvalho Graduate Program Petroleum Science and Engineering University of Campinas Campinas-SP, Brazil ABSTRACT Different equipments combined compose an offshore petroleum production system. Several development alternatives are available for a given offshore petroleum field. The selection of the most suitable system for a given scenario depends on field development characteristics and strategies such as its geographical location, water depth, environmental conditions and knowledge about similar systems already selected and in use for oil and gas production and available infrastructure in around. For the purpose of field production system design a database with types of production platforms, mooring systems, subsea equipments, reservoir main characteristics, type of wells and lifting processes is fundamental. Today, offshore petroleum reservoir production is more and more complex due to several variables involved and requirement needed to meet deep and ultra deep water depth, pre-salt petroleum with aggressive fluid characteristics, fields in remote areas and other environmental issues. Large fields in deep and ultra deep water are particularly challenging due to little availability of suitable platform types, among known concepts such as floating, production, storage and offloading unit (FPSO), semisubmersible, spar and tension leg platform (TLP). In the present paper, a database for worldwide offshore petroleum systems in use has been elaborated by searching data available in the literature. The database is organized for more than three hundred platforms distributed on more than four hundred different offshore oil fields. To serve as a basis for the conceptual design of a field production system, this database contains information such as type of the platform, field location, water depth, days for the first production, type of well, completion, mooring system, riser and offloading system. This information is structured for different water depth and environmental condition, for each field. From this database, analysis has been conducted for distribution of each type of platform by worldwide region, distribution of each type of platform by the offshore field by region, among others analysis. Concept of Utility Functions are applied to represent technological trends and to be helpful in the process. Among the results, a preference for FPSOs and semisubmersible was observed in Brazil offshore, semisubmersible, TLPs and Spars in Gulf of Mexico. In Europe, particularly the North Sea, FPSO, semisubmersible, and few TLPs have been found. In West Africa, most of the field production is based on FPSOs, although some semisubmersible and TLP could be observed. Similar analyses were conducted in other regions. Results and discussions show preferences regarding technology selected by each region, region historical data, and growth of water depth in different fields. ABREVIATIONS FPSO Floating Production Storage and Offloading FSO Floating Storage and Offloading SS Semisubmersible TLP Tension Leg Platform SCR Steel Catenary Risers SALM Single Anchor-Leg Mooring CALM Catenary Anchor-Leg Mooring DP Dynamic Positioning System 1 Copyright 211 by ASME

INTRODUCTION Offshore petroleum field development requires a huge amount of investment. Among those, are included reservoir geophysics and geology services, well construction and completion services, manufacture and installation of all petroleum subsea well production equipments, lines and riser system, and surface production facilities. Alternatives must be developed to help the selection of the most economically and technically suitable production system option for a given offshore petroleum field. The amount of investment needed and expected benefit from the selected production system have a direct dependency with system s design concept. For this selection, economical feasibility of the alternative together with system operational capabilities, oil and gas production rate and associated cost, among other features of the alternative systems must be analyzed. Different offshore petroleum field development systems have been extensively studied in literature. A production system to be applied for a given field depends on different factors such as field s water depth, area and depth of the petroleum reservoir to be produced, environmental conditions in the region, and so on. Then, selection of the best fitted design for a field s production system is obtained from a conceptual analysis of the basic design among systems allowable for that field. In the present paper, a database to support the selection process for offshore petroleum production system is presented and analyzed. A selection process based on this field database is introduced and data collected from worldwide developments for offshore petroleum field production are discussed. An extensive search for field development data from different sources from literature was conducted, and discussions are presented. Results show evolution and trends for the use of four types of above mentioned platforms applied for petroleum field development divided by region, water depth and so on. ORGANIZED DATABASE The database for production systems is formed by worldwide offshore petroleum fields obtained from literature. It consists of 33 platforms distributed along 449 different worldwide developed offshore petroleum fields, with focus on Floating Production System and Offloading units (FPSO), Semisubmersible platforms (SS), Spars and Tension Leg Platforms (TLP). The database is structured by type of platforms, well data, completion system, mooring system, riser system, offloading system, environment, among other information for each data. Number of Platforms 12 8 6 4 2 Number of Platforms by Region FPSO Semisubmersible SPAR TLP Total 63 51 53 58 52 57 5 36 27 18 28 22 21 21 1 16 7 3 2 4 5 11 Brasil North America Europe Africa Australia Asia Region Figure 1 Distribution of production platforms and totals of each type of platform by worldwide region. Number of Fields 12 8 6 4 2 Distribution of Offshore Fields FPSO Semisubmersible SPAR TLP Total 117 63 57 33 4 44 3 25 32 94 69 8 2 7 5 4 11 Brasil North America 75 37 37 54 Europe Africa Australia Asia Region Figure 2 Distribution of fields and totals of each type of platform by worldwide region. Number of Platforms Number of Platforms FPSO Semisubmersible SPAR TLP Total 5 4 3 2 194 66 19 24 Platform 33 63 Figure 3 Totals of each type of platform. 2 Copyright 211 by ASME

Number of Fields Number of Offshore Fields and Type of Platform FPSO Semisubmersible SPAR TLP Total 5 449 4 3 2 258 96 41 54 Platform Figure 4 Total number of offshore petroleum fields for each type of floating platform. Figure 1 shows the distribution of different types of floating production platform units and totals for each type by worldwide region applied for offshore petroleum field development. Figure 2 shows the number of fields with each type of floating production platform unit by worldwide regions. Figure 3 shows the total of each type of floating production platform unit worldwide, and Figure 4 presents the number of offshore petroleum fields associated with the total number for each type of floating platform unit. These results include petroleum fields located at water depth ranging from shallow to ultra deep water. In Figures 1 to 4, tendency of use of a given type of platform can be observed on a petroleum field development. Often a given offshore platform is reused to develop more than one petroleum field, which means that a given semisubmersible or FPSO unit is reused or relocated, sometimes after some maintenance or even after conversion. Moreover, Spar or TLP unit is used to develop different fields around the initial one. A tendency to use FPSO can be observed in offshore Brazil, followed by the utilization of semisubmersible production platform. When comparing with other offshore petroleum production regions, offshore Brazil presents a mild environment with calm ocean waves and wind. On the other hand, petroleum fields in offshore Brazil usually present high speed surface current distributed along the water depth, limited availability of derrick barges, limited seafloor pipeline infrastructure, and future field developments are focused on deep and ultra deep water depth and sub-salt reservoirs. In North America, FPSO s were till recently used only in Mexico and Canada area, since the first FPSO in Gulf of Mexico, USA region is commencing operation in 21. Commonly, semisubmersible, TLP and Spar are used in Gulf of Mexico where extreme hurricane environment, additionally to high speed loop sea current, is observed (Sablok and Barras, 29). In this case, platforms are forced to be evacuated and the production shut down in order to keep safety. On the other hand, pipeline system, derrick barge and other infrastructure are available to handle oil and gas production, and platform storage capacity is not usually required. Future field development in this region would be in ultra deep water and sub-salt reservoirs, with high pressure and high temperature reservoir characteristics. European regions have a tendency to use FPSO and semisubmersible platforms using few TLP, particularly in the North Sea. North Sea presents harsh and fatigue environment. In West Africa, FPSOs are the most commonly used platform, although some semisubmersible and TLP can be observed. West Africa presents mild environment with calm ocean waves. Platforms are required to have storage capacity for oil, once there is no pipeline infrastructure and derrick barges are not usually available. In Australia, FPSOs are the only used platform. Australia has predominantly gas fields, and export risers should have large diameter, where weak and friable soil at sea floor is observed. Derrick barges are not usually available. In Asia, mild environment is usually found, however, few derrick barges are available, and there are needs to keep production during storms with no pipeline infrastructure. Few semisubmersible, Spar, and TLP platforms are observed and FPSOs are commonly observed. ELEMENTS FOR THE SELECTION Today, four types of floating platform are observed in deep and ultradeep water operation, as previously shown. They are the FPSO, semisubmersible, Spar, and TLP. Among main elements to be considered in an offshore production system selection, there are the floating platform unit, well pattern and number of wells, mooring system, riser system, storage and offloading system. Selection implies to choose an alternative that better meet requirement from the analysis of above mentioned elements, petroleum reservoir characteristics and environmental condition at the site. Floating Platform Unit In the present study, water depth is classified according to the classification range presented in Table 1. Platform unit is very dependent to the water depth of the petroleum field. Floating platform unit usually presents restriction for mooring according to the water depth of the site. Table 1 Classification of water depths Shallow Deep Ultra deep Range (m) < 3 m 3 15 m > 15 m 3 Copyright 211 by ASME

Table 2 Platforms and water depths Platform Type Range (m) FPSO 43 26 Semisubmersible 72 2413 TLP 148 1425 Spars 558 2383 Table 2 summarizes type of platform and corresponding suitable water depth obtained from literature search and analysis. This data shows each type of platform used for different worldwide offshore petroleum fields that lead to the water depth range as indicated. It can be observed that water depths are spread from shallow to ultra deep, in general. Exception for the Spar which presents water depth that ranges from deep to ultra deep water. 3 25 2 15 5 through the - FPSO - West Africa Brazil Australia Asia Brazil -> North Sea Gulf of Mexico Asia, North Sea and Australia -> West Africa -> 197 198 199 2 21 Figure 5 Distribution of FPSO through water depth by worldwide region and year. 3 25 2 15 through the - Semisubmersible - West Africa Brazil Asia North Sea Gulfo of Gulf of Mexico Mexico -> Brazil -> 5 <- North Sea and Asia 197 198 199 2 21 Figure 6 Distribution of Semisubmersible through water depth by worldwide region and year. 3 25 2 15 5 through the - Spar - Asia Gulf of Mexico 197 198 199 2 21 Figure 7 Distribution of Spar through water depth by worldwide region and years. 3 25 2 15 5 through the - TLP - West Africa Asia North Sea Gulf of Mexico North Sea -> Gulf of Mexico -> 197 198 199 2 21 Figure 8 Distribution of TLP through the water depth by worldwide region and year. Figures 5 to 8 show the use of FPSO, semisubmersible, Spar and TLP, respectively, according to the water depth along the year. They are also differentiated by region of application. In Figure 5, it can be observed that FPSO is used since middle seventies in offshore Asia, North Sea and Australia, mainly for shallow water applications. West Africa and Offshore Brazil use FPSOs from early two thousand, for deep and ultra deep water depth applications. The first FPSO was installed in 1976 at the Ardjuna Saki field (Indonesia), in a water depth of 43 m (Ronalds and Lim, 1999). In Brazil, the first FPSO was the Presidente Prudente de (PP) Moraes which began to operate at Campos Basin in 1979 being installed at 12 meters water depth (Mastrangelo, 2). In Gulf of Mexico, the first FPSO will be installed in 21, at water depth of 26 meters, a record in water depth (Wilhoit and Supan, 28; Wilhoit and Supan, 21). 4 Copyright 211 by ASME

Figure 6 illustrates results for Semisubmersible platform applied since middle seventies in the North Sea and Brazil, mainly for shallow water applications. Recently, it has been used for ultra deep water application ranging from 15 to 25 meters, in offshore Gulf of Mexico and Brazil. Today, semisubmersible platforms are widely used in Brazil, Gulf of Mexico, Asia and North Sea. North Sea and Asia operate semisubmersible predominantly in shallow and deep water depths, up to 5 meters. In Brazil, operational water depths range from shallow to ultra deep water, and in Gulf of Mexico from deep to ultra deep water. Semisubmersibles normally use wet Christmas tree solution with direct vertical access to the wellhead. Figure 6 also indicates the first application of semisubmersible for field development was the North Sea Pioneer (UK) in 1975, at water depth of 79 meters. In Brazil, Sedco 135D was installed at water depth of 122 meters, in 1977 (Lim and Ronalds, 2). Figure 7 shows result for Spar platforms which are relatively new technology for deepwater and ultra deep water applications (Sablok, 29). Their uses since late nineties are concentrated at offshore Gulf of Mexico, in deep and ultra deep water depth. The first spar (Neptune) began to operate in 1997, at water depth of 588 meters. The unique Spar outside Gulf of Mexico is the Kikeh at offshore Malaysia (27), located at the water depth of 133 meters (Wilhoit and Supan, 29). TLPs have been initially experienced in offshore North Sea field developments. Today, most of the TLPs are in deep water Gulf of Mexico. Other recent ones are observed in the North Sea, West Africa and Asia regions as in Figure 8. In this Figure, it is clear that Gulf of Mexico TLPs are in deepwater. In North Sea, they are in shallow water up to around 3 meters, and in West Africa in shallow and deepwater, and finally, in Asia at deep water depth. The first Hutton TLP in Gulf of Mexico was installed in 1984, at water depth of 148 meters. Evolution of by Type of Platform 3 FPSO 25 SS Spar TLP 2 15 5 1975 1985 1995 25 Figure 9 Evolution of water depth for each type of platform. 7 6 5 4 3 2 1 Distribution of the Total Number for Each Type of Platform in Deep and Ultra deep 62 26 Figure 1 Distribution of each type of platforms applied on deep and ultra deep water depth. The evolution of water depth for each type of platform is presented in Figure 9. In this Figure, it can be noticed that there is a substantial growth on developing deepwater offshore petroleum fields since 1995, and in ultra deep water since 2. Figure 1 shows distribution of the number of platforms operating deep and ultra deep water by type of the platform. Again, it is observed that the number of FPSOs in operation is larger than the other types of platform. Currently, the deepest installation for FPSO is the BW Pioneer in Gulf of Mexico at water depth of 26m. As for semisubmersible platform there is the Independence Hub on the Atlas field in Gulf of Mexico, at 2413 meters. Perdido Spar on Block AC 857 in Gulf of Mexico, at 2383 meters water depth is the deepest Spar installation. The deepest TLP installation is the Magnolia on blocks 783 & 784 GB, Gulf Mexico, in 1425 meters water depth. Well Pattern and Number of Wells Petroleum wells in offshore fields may be arranged in two different configurations: clustered around the platform location or spread around the field (Franco, 23). Sometimes, it could be a combination of both. The two types of well arrangements suggest the use of different types of platform. Semisubmersible and FPSO units commonly use wet completion system which allows a distributed well pattern around the petroleum reservoir area as well as satellite wells. This well arrangement allows efficient drainage of the reservoir and gives possibility to use early production schemes. TLP and Spar platforms conventionally use dry completion system which gives clustered well pattern centered around the platform location. However, some satellite wells can be also combined for this solution, and if frequent interventions into the well are needed, clustered wells could facilitate this work. The number of wells needed to develop a reservoir production influences the selection of the type of platform to be used in field development. Each type of platform has design limit for the number of wells allowed to operate. Spread moored FPSO usually allows around 75 wells, and the turret moored FPSO 57 19 16 FPSO SS Spar TLP 5 Copyright 211 by ASME

wells. Semisubmersible platform allows 48 wells, Spar 2, and TLP 46 wells (Wilhoit and Supan, 21). Mooring System Each type of floating platform has the most suitable mooring system to be used, and it should be selected observing platform type, well pattern, number of wells and water depth. Among possible mooring systems for FPSO are the SALM (single anchor-leg mooring), CALM (catenary anchor-leg mooring), Turret Mooring, Spread Mooring and DP (dynamic positioning) assisted ones. Figure 11 shows evolution of the water depth for FPSO mooring systems through the years. Mooring Systems by through Time 3 FPSO 25 Jacket Soft Yoke CALM Turret SALM Spread Mooring DP 2 15 5 197 198 199 2 21 Figure 11 Distribution of FPSO s Mooring Systems by Water Depth through the s Semisubmersible platforms usually apply two types of mooring systems: catenary spread or taut leg mooring system, in deep and ultra deep water applications. Spars are normally moored by taut catenary systems and TLPs by tensioned vertical steel tendons. Riser System Risers are tubular connections between an oil or gas well at the seabed and a processing facility platform at the sea surface. Sometimes, they also have other functionalities such as in an offloading system for the produced oil and gas, or to inject water or gas into a reservoir. Risers can be rigid or flexible pipes. Moreover, they could be also a combination of pipelines and structures such as tower and hybrid types. Each type of riser is used according to the type of platform, water depth of operation and environmental conditions at the location of the field. Flexible risers and steel catenary risers (SCR) are frequently used for deepwater FPSO and semisubmersible platform based production systems due to their curved shapes. Rigid risers with vertical arrangement usually do not allow large platform displacements and offsets, and then they are commonly applied for Spar platform and TLP. On the other hand, riser system is very sensitive for vertical platform motions. Then, riser system should fulfill this requirement, particularly in deep and ultradeep water depth. Storage and Offloading In offshore deep water depth, offloading of oil production from a FPSO or FSO to a relief ship tanker is done, and the relief ship tanker will carry the produced oil to the shore or to an onshore pipeline terminal. The relief ship tanker system is very useful when deficiency of pipeline infrastructure is observed, and in this case, storage capacity for the floating processing facility is needed. FPSO can ally both abilities of process and storage. Gulf of Mexico presents a sufficient infrastructure of pipelines, and usually platforms are not required to have storage capacity. If semisubmersible platform, Spar or TLP are used and there is no infrastructure of pipelines, usually floating storage and offloading (FSO) platform are combined in the system. Petroleum Reservoir Characteristics and Environmental Condition Petroleum reservoir characteristics such as area and thickness of the reservoir, permeability and porosity, reservoir fluid petrophysics are important information that determines the selection of production system, for instance, geometry of the reservoir Environment condition such as waves height and periods, wind and sea current speed are important issues that influence the production system scheme to be applied for field development. For remote areas, in deep and ultra deep water with harsh environmental conditions, a careful planning for production surface facility and subsea equipment is required (Galeano and Morooka, 1999). Environmental conditions are usually related to geographic location of the field. As shown in before for offshore Brazil, through the Figures 1 and 2, semisubmersible and FPSO solutions are preferred due to the mild environment found at Brazilian coast. On the other hand, the Gulf of Mexico prefers semisubmersible, TLP and Spar. North Sea uses FPSO, however, few semisubmersibles and TLPs are also observed. In West Africa and Australia, FPSO is mainly used, however, in West Africa few semisubmersible and TLP are also observed. A great use of FPSO and small application of semisubmersibles, and finally, only one unit for Spar and TLP, respectively, are observed in Asia region. TECHNOLOGY ATTRACTIVINESS Technology is improving more and more due to recent necessity to explore and to develop remote areas, and deeper water depths. And, not only to face harsh environment of those offshore sites, techniques have been studied and developed to overcome difficulties, and to produce more complicated petroleum reservoirs with the handle of more aggressive fluids such as that produced from offshore ultra deep water pre-salt fields. 6 Copyright 211 by ASME

Total Number of Platforms Figure 12 Evolution of Accumulated Number of Platforms by of First Oil Production Utility Utility 35 3 25 2 15 5 1..8.6.4.2 FPSO. 2 3 1..8.6.4.2 Evolution of Number of Platforms FP SO SS TLP SP AR TOTAL 1975 198 1985 199 1995 2 25 21 Number of FPSO (a) Semisubmersible. 2 4 6 8 Number of Semisubmersible (b) 1 U(N) = 1 ( 76 e 1 U(N) = 1 ( 6 e.15 N.48 N ) ) Utility Utility 1..8.6.4.2 TLP. 1 2 3 4 5 1..8.6.4.2 1 U(N) = 1 ( 15 e Number of TLP (c) Spar 1 U(N) = 1 ( 5 e. 1 2 3 4 5 Number of Spar (d).31 N Figure 13 Technological Attractiveness through Utility Functions for each type of platform: (a) FPSO; (b) Semisubmersible; (c) TLP, and; (d) Spar. In a petroleum production system design, it is fundamental to have a procedure to catch this technology tendency and to use this knowledge into a new field s system design. In order to address this technological attribute in the process of alternative selection for a field production system, Theory of Utility Function can be used to quantify this issue. Then, desirability for technological preference involved on different types of platform systems can be measured by means of the Utility Function which also expresses the degree of well-being preference provided by designers. As part of the process, factors such as satisfaction of the management, feasibility of the solution, and the rate of use of a selected technological solution are considered key to accurately assessing the utility of a given platform system. This measure is normally presented in as a mathematical expression. According to this approach, technological maturity increases with the time. S shaped curve ).27 N ) 7 Copyright 211 by ASME

can be fitted to describe this tendency which represents a slow growth of technology with the time in the beginning of process; going to grow fast meaning the learning of technology, and finally; diminishing this grow rate indicating the saturation of this technology. Utility Function for technological attribute can be estimated through the curve obtained from the evolution of accumulated number of platform in operation with the years (Castro and Morooka, 22; Furtado, 2). In the present work, technology for FPSO, Semisubmersible and TLP, for instance, are considered to be very close to reach technological maturity for application in deep and ultra deep water requiring some investment to develop technology with respect to mooring system for ultra deep water case. Then, technological maturity for those platforms in present day was taken equal to 95%, for each one. Finally, Spar is being considered relatively recent technology with less number of platforms in operation than the others, and then the technological maturity was taken as 8%. Technological maturities for each platform are considered to build utility functions of each platform alternative, respectively. Figure 12 shows evolution of accumulated number of platform in operation through the years, for FPSO, Semi-submersible, TLP and Spar, respectively. And, Figure 13 show utility functions for each type of platform. In general, comparative analysis of the obtained result with previous ones (Castro and Morooka, 22) has shown some delay in the tendency to reach technological maturity, exception for semisubmersibles. Perhaps, it happens due to recent technological trends and challenges faced to moor floating production platforms in ultra deep water depth. CONCLUSIONS From the literature data search and analysis for offshore petroleum production systems, it is concluded that four types of platforms, among others, are able to be used in deep and ultra deep water: FPSO, semisubmersible, Spar and TLP. FPSO presents storage capacity and requires wet completion systems. It can be a solution for shallow to ultra deep water field production. They are worldwide most used platform for offshore development, except for the Gulf of Mexico. Semisubmersible is also an available solution for a field production from shallow to ultra deep water, and it also requires wet completion system with direct vertical access solution. It is the second widely used solution for offshore worldwide petroleum field development. Spar is used only for deep and ultra deep water depth with the use of dry completion. It is a relatively new technology, and its use is concentrated at Gulf of Mexico, with only one case of use in Malaysia. And, TLP is available to be used from shallow to deep water depth with dry completion. The database collected from the literature and analyzed allowed gathering an important knowledge to design an offshore petroleum production system. Advanced techniques can be combined with obtained result to facilitate selection and design process of an offshore system to develop a petroleum field. Further advances in this study are expected in near future. ACKNOWLEDGMENTS The authors would like to thanks to Capes and CNPq, Finep/CTPetro and Petrobras for supporting this research. REFERENCES Castro, G.T.; Morooka, C.K., Methodology for the Selection of an Alternative for a Floating Production System, International Conference on Ocean, Offshore and Arctic Engineering, OMAE 28321, Oslo, Norway, 22. Franco, K.P.M., An Intelligent System to Assist the Selection of Offshore Production System, M.Sc. Thesis, University of Campinas, Unicamp, 23. Furtado, R., Sensitivity Analysis on Multi-attribute Decision Models for Petroleum Exploration and Production Systems, M.Sc. Thesis, University of Campinas, Unicamp, 2. Galeano Y.D.; Morooka, C.K., Systematic Design for Offshore Oilfield Development, International Society of Offshore and Polar Engineers, ISOPE, Brest, France, 1999. Lim, E.F.H.; Ronalds, B.F., Evolution of the Production Semisubmersible, SPE Annual Technical Conference and Exhibition, SPE 6336, Dallas, Texas, USA, 2. Mastrangelo, C.F., One Company's Experience on Ship- Based Production System, Offshore Technology Conference, OTC 1253, Houston, Texas, USA, 2. Ronalds, B.F.; Lim, E.F.H., FPSO Trends - FPSO Trends, SPE Annual Technical Conference and Exhibition, SPE 5678, Houston, Texas, USA, 1999. Sablok, A, Barras, S., The Internationalization of the Spar Platform, Offshore Technology Conference, OTC 2234, Houston, Texas, 29. Wilhoit, L.; Supan, C., Worldwide Survey of Semi-FPSOs and FPUs, Offshore Magazine, Sept. 28. Wilhoit, L.; Supan, C., Worldwide Survey of SPAR, DDCV, and MinDOC Vessels, Offshore Magazine, Jan. 29. Wilhoit, L.; Supan, C., Worldwide Survey of Floating Production, Storage and Offloading (FPSO) Units, Offshore Magazine, Aug. 29. Wilhoit, L.; Supan, C., Worldwide Survey of TLPs, TLWPs, Offshore Magazine, Feb. 21. Wilhoit, L.; Supan, C., Solutions & Records for Concept Selection, Offshore Magazine, May 21. 8 Copyright 211 by ASME