OTC 21338

Design of the Worlds Deepest Hybrid Riser System for the Cascade & Chinook Development Ruxin Song, Pascal Streit, TECHNIP USA Inc.

Copyright 2011, Offshore Technology Conference This paper was prepared for presentation at the Offshore Technology Conference held in Houston, Texas, USA, 25 May 2011. This paper was selected for presentation by an OTC program committee following review of information contained in an abstract submitted by the author(s). Contents of the paper have not been reviewed by the Offshore Technology Conference and are subject to correction by the author(s). The material does not necessarily reflect any position of the Offshore Technology Conference, its officers, or members. Electronic reproduction, distribution, or storage of any part of this paper without the written consent of the Offshore Technology Conference is prohibited. Permission to reproduce in print is restricted to an abstract of not more than 300 words; illustrations may not be copied. The abstract must contain conspicuous acknowledgment of OTC copyright.

ABSTRACT With the successful deployment of the five Cascade & Chinook free standing hybrid risers (FSHRs) in the Gulf of Mexico at a water depth of 8,250 ft in year 2010, hybrid riser technology is adopted for deepwater development worldwide. It is basically a combination of steel and flexible risers with utilization of their advantages and hence offers unique features. The Cascade & Chinook FSHRs set a few new world records such as the deepest installed hybrid risers, first disconnectable hybrid risers, first hybrid riser in severe environmental conditions in the GoM, first hybrid riser designed to accommodate two floater concepts. Compared to other installed hybrid risers worldwide, the Cascade & Chinook FSHRs posed more technical challenges and hence required more engineering effort to come up with robust engineering solutions. This paper addresses the engineering challenges and solutions associated with the detail design of the Cascade & Chinook FSHR system including global configuration, material selection and sizing, component design, global and local analysis, and qualification testing. A brief description of the Cascade & Chinook hybrid riser system is given first together with the highlights of the technical challenges. Secondly, factors affecting the global configuration and local component design are identified and evaluated. The logical procedure for design and analysis of deepwater FSHRs is discussed and presented in more detail. Thirdly, focus is given to the global response analysis including strength and fatigue as well as local finite element analysis of components such as the taper stress joint, buoyancy can, riser top, lower assembly and foundation pile. Discussion is also given to the relationship between engineering design, fabrication and installation, which is of particular interest for this type of riser. And in conclusion, some important lessons learnt from the execution of the Cascade & Chinook FSHR engineering are summarized.

1. INTRODUCTION In recent years, exploration and production activities have increased dramatically in deep and ultra-deep water, nearly tripling the water depth of production facilities in the last decade or so. The targeted water depths for oil and gas developments in areas such as the Gulf of Mexico (GoM), West of Africa (WoA), and Brazil are increasing every year. Among the field proven riser concepts shown in Figure 1-1, hybrid risers offer certain unique advantages [Ref. 4] over other concepts such as steel catenary risers (SCRs), top tension risers (TTRs) and flexible risers (FRs) for specific applications.

2 OTC 21338

Figure 1-1: Deepwater Field Proven Riser Concepts

In Oct. 2007, the first Brazilian FSHR was successfully developed and deployed in the Campos Basin for Petrobras as oil export for the P-52 PDET project [Ref. 3]. In Dec. 2009 and early 2010, the first FSHRs in the GoM, the first disconnectable FSHRs and the deepest five FSHRs in the world were deployed successfully for the Cascade & Chinook field development. The FSHR consists of a vertical rigid pipe anchored to the seabed via a foundation (e.g. suction pile) and tensioned by means of a near-surface buoyancy can that provides the required uplift force. For the single line FSHR, one flexible jumper connects the rigid riser via a gooseneck to the FPU. The connection of the riser to seabed is by means of a mechanical connector (e.g. tie-back connector or roto-latch connector). A riser base jumper, either flexible or rigid, connects the riser offtake spool and PLET.

Although there are different versions of the FSHR, and its configuration has been modified through the years, the key technical benefit of this concept remains that the major rigid vertical riser is offset from the floating production unit (FPU) using a top flexible jumper as connection. Hence the rigid riser is decoupled from FPU motion and is thus fatigue insensitive. Since the fatigue design of deepwater risers is a common challenge, the decoupling effect enhances FSHR performance significantly. Compared to other installed hybrid risers worldwide, the following unique engineering challenges are recoginized for the Cascade & Chinook FSHRs, some of which are world records.

1. Deepest FSHR in the world: ultra-deepwater development in a water depth of 8,250 ft in the GoM. 2. HP/HT: Design pressure is 10,000 psi and design temperature is 236oF. 3. First Disconnectable FSHR in the world. 4. First FPSO in the GoM with FSHR in a very harsh environment subject to high loop currents. 5. First FSHR designed for 30 years to accommodate two different types of floaters covering early production

system (EPS) via FPSO and a permanent installation later. 6. Fast track: 28 months from contract award to completion. 7. Long lead items had to be identified and designed at an early stage in order to place the purchase orders

and meet project milestones. 8. First reel-installed FSHR in the world.

This paper presents the detailed engineering design aspects of the Cascade & Chinook ultra-deepwater FSHR. First of all, a general description of the Cascade & Chinook field is presented with a focus on the FSHR system. Secondly, the procedure for engineering design and analysis, implemented for the Cascade & Chinook FSHRs, is discussed and presented in more detail. Due to the complexity of the FSHR, different applicable design codes have been presented and discussed. Global configuration design with consideration of riser performance and its effect on component design is presented followed by major design considerations for individual components of the system. Thirdly, the analysis requirement and methodology are discussed in detail with a focus on global response analysis, interferenece analysis, vortex induced vibration (VIV) analysis, buoyancy can (BC) VIM fatigue analysis, motion fatigue analysis, interface loads, and component analysis: such as for the buoyancy can, tether chain system, top riser assembly, flexible jumper configuration, and riser foundation pile. The relationship between engineering design, fabrication and installation, which is of particular interest to this type of riser, is discussed.

OTC 21338 3

Some key lessons learnt are summarized at the end of this paper and ways for engineering improvements are also discussed.

2. DESCRIPTION OF THE CASCADE FSHR 2.1 Project Description The Cascade & Chinook fields, operated by Petrobras America Inc. (PAI), are located in the Walker Ridge Area of the US Gulf of Mexico approximately 180miles off the South coast of Louisiana. Water depths in the fields range from 8,153ft to 8,852ft. A phased development is planned with initial production from both fields tied back to a turret-moored Floating, Production, Storage, and Offloading vessel (FPSO). A disconnectable turret-buoy will enable the vessel to sail away to avoid approaching tropical storms. On disconnection, the buoy will freely descend to a predetermined depth, to protect the mooring lines, risers and umbilicals from the surface environment. Production from the Cascade & Chinook wells will be transported to the FPSO through flowlines and FSHRs. The processed export oil will be offloaded to shuttle tankers. The unconsumed produced gas will be exported via an FSHR and pipeline. The field layout for the Early Production System phase of the Cascade & Chinook developments is shown in Figure 2-1.

Figure 2-1: Cascade & Chinook Field Layout

2.2 FSHR Description The Cascade & Chinook FSHR has rigid riser joints as the major part with a gooseneck at the top that connects to a flexible jumper which bridges between the rigid riser and the FPSO internal turret. The Cascade & Chinook FSHR system is composed of the following components and is illustrated in the figure below. Top Flexible Jumper Buoyancy Can Tether Chain Assembly Gooseneck Assembly Top Riser Assembly (TRA) Upper Tapered Stress Joint Riser Joints with Coating Lower Tapered Stress Joint Off-take Spool Riser Base Roto-Latch Connector Suction Pile Foundation Rigid Bottom Jumper

4 OTC 21338

Figure 2-2: Cascade & Chinook FSHR Illustration

3. FSHR ENGINEERING DESIGN 3.1 Design Basis Primary design data and basis are tabuluated below. Table 3-1: Cascade & Chinook FSHR Design Basis Summary

Description Value Unit Water Depth 8,250 ft Design Life 30 years Production Riser OD 9-5/8 inch Gas Export Riser ID 6 Linepipe Material Grade X70 API 5L U-value (ID based) 0.8 BTU/oF/ft2/hr Design Pressure Production Riser 10,000 psi Design Pressure Gas Export Riser 3,000 psi Design Temperature - Production 230 F FPSO Length - Overall 793.24 ft FPSO Turret Location Fore of Midship 296.75 ft FPSO Turret Height 59.71 ft FPSO Turret Depth from MWL during disconnection 164.04 ft Max FPSO Offset Intact/Damaged 6% / 8% WD 3.2 Design Flowchart Considering the unique challenges imposed by the Cascade & Chinook FSHR, complexity of the system and interface with fabrication and installation, there is a logical sequence to be followed for FSHR engineering. The flowchart in Figure 3-1 shows the procedure and major issues to be considered during the engineering design of the Cascade & Chinook FSHR.

OTC 21338 5

Figure 3-1: FSHR Engineering Design Flowchart

3.3 Design Codes Due to the complexity of the FSHR system, different design codes are needed to address individual components based on their functionality, while the system design must satisfy API RP 2RD as a primary design code.

Table 3-1 below lists some of the design codes and applicable local components used for the Cascade & Chinook design.

6 OTC 21338

Table 3-1: FSHR Design Code Summary

Code Title Application

API RP-2RD Design of Risers for Floating Production Systems (FPSs), and Tension Leg Platforms (TLPs)

Primary, General

API RP 2A-LRFD

Recommended Practice for Planning, Designing and Constructing Fixed Offshore Platforms- Load and Resistance Factor Design

Suction Pile Design

API RP 2SK Design and Analysis of Station Keeping Systems for Floating Structures

Suction Pile Design

API Bulletin 2U Stability Design for Cylindrical Shells Suction Pile & BC Design

API Bulletin 2V Design of Flat Plate Structures Suction Pile & BC Design

AISC Steel Construction Manual WSD General

DNV-RP-E303 Geotechnical Design and Installation of Suction Anchors in Clay Suction Pile Design

DNV-RP-B401 Cathodic Protection Design General

DNV RP-C203 Fatigue Design of Offshore Steel Structures Fatigue Analysis

DNV Rules DNV Rules for Planning and Execution of Marine Operations Offshore engineering

ASME Boiler and Pressure Vessel Code (Section VIII, Div. 3) Structural Design

DNV RP-F105 Free Spanning Pipelines Riser Base Jumper

. 3.4 Global Configuration Design As the first step of the FSHR design, its global configuration needs to be engineered considering the following factors: Functional requirements In-place performance Metocean criteria FPSO excursions Subsea field layout Flexible jumper performance Field interference Fabrication specification Installation methodology

The following parameters have been identified governing the global configuration design: Depth from MWL to the top of buoyancy can; Riser foundation offset to riser hang off location at FPSO; Overall flexible jumper length;

OTC 21338 7

Flexible jumper departure angles at FPSO and riser ends; Tether chain between buoyancy can and riser top; Installation methodology

Figure 3-2: FSHR Global Configuration

3.5 Key Design Issues Due to the challenges of the Cascade & Chinook project such as HP/HT, ultra-deepwater, disconnectable requirement, strong loop current, potential field interference, and installation methodology, there are some unique design features of the FSHRs. Key design issues include the following: Global Configuration Riser base offset to FPU Flexible jumper length BC submerged water depth BC Design Interface design Field interference

8 OTC 21338

3.6 Selection and Design of Riser Component A brief description and design selection of the individual riser components of the Cascade & Chinook FSHR system and their functionality is given in this section. Due to the identical application and product standardization, there is no different consideration for production and gas export risers. Hence, the selection below is applicable to risers with different functions.

Flexible Jumper: The overall flexible jumper length is 2400 ft for production and gas export FSHRs connecting the top of the vertical steel riser to the FPSO turrent. Figure 3-3 below shows the fabricated production flexbile jumper ready for shippment.

Figure 3-3: Cascade & Chinook Flexible Jumper

Buoyancy Can: The buoyancy can (BC) on top of the riser provides the required uplift to keep riser in-place as well as to limit large offset and angular deflection at flexible jumper extremities. The Cascade & Chinook buoyancy can is of a closed form design and compartmentized as illustrated in Figure 3-4, all chambers are closed using ROV plugs for the in-place condition and are pressurized with nitrogen. In this case, the internal pressure of all chambers is maintained constant regardless of the potential BC motion. The overall dimension of the production BCs is about 107 ft length x 21 ft in diameter. The net uplift force deliveried by the production BCs is about 670 te for normal in-place condition.

Figure 3-4: Cascade Buoyancy Can

Gooseneck Assembly: The function of the gooseneck assembly is to connect the flexible jumper and the riser. A key part of this assembly is the connector. Handling, transportation and deployment requirements must be accommodated during design. Figure 3-5 shows the Cascade & Chinook gooseneck assembly with a hydraulic connector fabricated.

OTC 21338 9

Figure 3-5: Gooseneck Assembly with Connector

Tether Chain System: The design of the BC to riser connection depends upon the connection location. The Cascade project selected a dry connection using a tether chain system as shown in Figure 3-6 below. Tether Chain is R5 quality studless chain with a 171 mm diameter. At the ends of the tether chain system, there are universial joints, which are made of F22 forged material with 80 ksi strength.

Figure 3-6: Buoyancy Can Tether Chain Connection

Top Riser Assembly: To provide a platform of joining gooseneck, vertical riser string and buoyancy can, a top riser assembly (TRA) is introduced as shown in Figure 3-7 below. The production TRA is about 32 ft in height and 86 kips in dry weight. TRA with outfitting of monitoring and connector during SIT is shown in the figure below.

10 OTC 21338

Figure 3-7: Top Riser Assembly at SIT

Riser Joints: Due to HP/HT and ultra-deepwater, the riser joints for the Cascade FSHR were designed with two wall thicknesses. The top 400 ft is heavy wall joints with a thickness of 42 mm, and the wall thickness of the rest of the riser joints is 33.6 mm to mitigate large tensile and hoop stresses and while minimizing the riser weight. Tapered Stress Joint: The TSJ is needed at both ends of the riser pipe to accommodate relatively large localized bending moments. TSJs are made from forging material F22 and welded onshore to a pup-piece of riser pipe. Due to relative low rotational stiffness at the riser bottom, the TSJ is about 40 ft in length and 3.3 inch in wall thickness at the root, which is relatively compact. A section of the TSJ with its pup piece welded is shown in Figure 3-8.

Figure 3-8: Tapered Stress Joint Offtake Spool: The offtake spool is a cylindrical component with support structures. The spool contains a flow path that travels through the top of the spool and exits from the side via an offtake. The offtake, formed as an induction bend that exits from the side of the spool, presents an upward facing mandrel for ROV connection of the riser base jumper. The offtake is connected to the side of the spool via a weld-on compact flange connection. The offtake spool has a flanged bottom for interface with the base connector. Figure 3-9 shows the Cascade & Chinook production riser offtake spool.

Figure 3-9: Production Riser Offtake Spool at Fabrication

Riser-to-Base Connection: The offtake spool is connected to the base suction pile via a roto-latch connection, which is designed with an angular deflection of 20o. The figure below shows the roto-latch connector during FAT.

OTC 21338 11

Figure 3-10: Riser Bottom Roto-Latch Connector at FAT

Riser-Base Jumper: The riser bottom jumper (RBJ) connects the FSHR to a PLET. Figure 3-11 shows the Cascade & Chinook gas export RBJ during FAT. One challenge of the RBJ design is the coupling effect with the FSHR, which imposes additional fatigue damage. The dimension of the production RBJ is 81 ft in span and 25 ft in height.

Figure 3-11: Gas Export FSHR RBJ at FAT

Riser Suction Pile: To anchor the riser to the seabed, a suction pile is designed based on geotechnical data and bottom tension experienced by the pile during its design life. The Cascade & Chinook suction pile with top arrangement during deployment is shown in the figure below. The production suction pile is about 90 ft in length and 16 ft in diameter, which can withstand the riser bottom tension of 485 kips during its normal operating condition.

Figure 3-12: FSHR Suction Pile during Deployment

4. FSHR ANALYSIS METHODOLOGY 4.1 Analysis Objective

The objectives of an FSHR analysis are identified as follows: To obtain the riser global response by applying environmental events and FPSO motion to the FSHR. To demonstrate that the design complies with relevant specifications and industrial codes. To provide interface load inputs for mechanical component design.

12 OTC 21338

4.2 Analysis Software

A primary analysis was conducted using industry-standard analysis software packages. The following tools have been used for the Cascade & Chinook project engineering of the FSHR system: ABAQUS ANSYS FLEXCOM ORCAFLEX SHEAR7

Considering the complexity of the FSHR system and computing convergence, commercialized riser software were used for global response analysis and generic FEA programs were used for local component analysis and design. In addition, there are also some purpose-developed in-house programs to handle particular issues, e.g. interference.

4.3 Loads and Load Case Matrix

The Cascade FSHRs experience the following load types, which must be taken into account: Environmental loads (wave, current, wind) Vessel motion loading (static, dynamic) Pressure & temperature loading (internal, external) Functional loading (weight, content, buoyancy)

Different load combination criteria are given. In general, five different load categories are checked for FSHR strength response including Operating Extreme Survival Hydrotesting Temporary (installation, transportation)

The FSHRs are analyzed for the design extreme storm load case matrix defined based on API RP 2RD. In addition to the load categories defined above, the following have also been taken into account when setting up the load case matrix, which ends up with more than 400 load cases. Different combinations of metocean data Turret buoy status (intact vs. damaged) Riser operation service (temperature & pressure) Mooring line status (intact vs. damaged) Buoyancy can status (intact vs. damaged) FPSO turret buoy status (connected vs. disconnected) Vessel position with respect to FSHR plane (near, far, transverse, quartering) as shown in Figure 4-1 below.

OTC 21338 13

Figure 4-1: FPSO Position Definition

4.4 Computer Modeling

Computer modeling is consistent regardless of analysis types used, e.g. strength or fatigue. The general computer modeling technique for the Cascade & Chinook FSHR is described here even though it may vary for different analyses, e.g. strength analysis and VIV analysis. Figure 4-2 below is an illustration of the Cascade & Chinook FSHR global modeling using Flexcom. All components of the FSHR are modeled using hybrid-beam elements. The element meshes are suitably graded to ensure that response in critical areas is accurately identified, such as in the tapered stress joint. This is achieved by applying mesh refinement over areas of high loading, high curvature and significant changes in geometric properties. To ensure the mesh is adequately refined, von Mises Stress (VM) envelopes along the riser are reviewed. The mesh is refined and results compared until it is demonstrated as fit for purpose. Finite element (FE) models covering major FSHR components are created for the analysis. Models will include upper-end boundary condition definition, BC, flexible jumper, gooseneck assembly, top riser assembly, riser pipes, VIV suppression devices, seabed properties, and bottom-end boundary condition definition. The FE models need to be sufficiently detailed in critical areas to achieve reasonable stress recovery. Figure 4-3 and 4-4 show global and local FEA modeling of the buoyancy can using ABAQUS with more than 200,000 elements.

14 OTC 21338

Figure 4-2: FSHR Global Computer Modeling

Figure 4-3: Buoyancy Can ABAQUS Global Modeling

Figure 4-4: Buoyancy Can ABAQUS Local Modeling

4.5 Strength Analysis

Extreme storm analyses are conducted for the load cases defined per API RP 2RD. FSHR is analyzed with the vessel RAO accordingly. The FSHRs are analyzed using a regular wave approach to screen for governing load cases. Analyses are conducted to determine the effect upon riser response of variations in wave period from the base cases. Where the responses are significantly worse, the base case analysis is repeated with the more severe wave period.

OTC 21338 15

Where regular wave analysis is used, load cases critical to riser response or design are identified from the regular wave cases and further analyzed using an irregular wave approach to determine if there is any undue conservatism due to the analysis approach. Where irregular waves are used, sufficient care is taken to ensure a realistic representation of the storm based statistics. An important output from the global response analysis are the interface loads at the location of individual components. These loads need to be generated early in engineering design and certain margins must be added to the FEA output. These extreme interface loads are inputs to local component design, such as the TSJ, and the TRA.

4.6 Fatigue Analysis General

FSHR fatigue life is predicted based on cumulative damage calculations including contributions from FPSO motions, VIV responses, BC vortex-induced motion (VIM), and installation procedures. The fatigue damage from each contributing mechanism is factored by the appropriate safety factors prior to combination to determine the combined fatigue life. Typical fatigue loadings are: VIV Motion fatigue BC VIM fatigue Installation Start-up and shut-down

The pie chart below shows the combined fatigue life of riser pipe of production FSHR, from which one can tell that VIV fatigue damage is dominant for an FSHR overall fatigue life.

Figure 4-3: Overall Fatigue Life Combination Production

4.7 VIV Fatigue Analysis

From the figure above, it can be seen that VIV fatigue is the single most important factor contributing to overall fatigue damage. More details can be found in Song, R. et al [Ref. 4].

4.8 Motion Fatigue Analysis

The dynamic load cases are analyzed for the FSHR and then post-processed to determine the fatigue life along the length of the riser. The critical locations are at the top and bottom portions of the riser string. Due to the decoupling effect of the flexible jumper, FPSO motion induced fatigue damage is secondary. More description of the motion fatigue analysis method for an FSHR can be found in Song, R. et al [Ref. 4].

4.9 BC VIM Fatigue Analysis

VIM originates when fluid passing the buoyancy can causes low pressure vortices to form downstream of the can. These vortices are shed periodically at frequencies that are fluid velocity dependent. If the frequency of excitation of the vortices is close to, or the same as, a natural frequency of the BC, resonance will occur. Consequently, large and damaging amplitudes of oscillation may be induced when interaction between the current and BC motion causes lock-in.

VIV WF VIM Installation

16 OTC 21338

The primary motion of a BC under current is transverse to the current direction, while the secondary motion is in-line with the current, together forming a figure of 8. During lock-in, the BC resonates and causes the riser to undergo cyclic ranges of tension and curvatures that initiate fatigue damage.

Transverse VIM occurs when the vortex-shedding period is close to the natural period of the BC. It takes place in the direction perpendicular to the current following approximately a sinusoidal pattern. Transverse motion is normally defined as the ratio of single amplitude to the BC diameter (ie A/D). In-line VIM occurs in the direction of the current and is affected by the transverse VIM. The magnitude of in-line A/D is typically 10% to 25% of the transverse A/D. However, in-line motion is generally at twice the frequency of the cross-flow motion. Thus, in general, the fatigue damage contributed from in-line VIM cannot be neglected. BC VIM Evaluation Procedure: The flowchart for BC VIM analysis is shown in Figure 4-4.

Figure 4-4: BC VIM Fatigue Analysis Flowchart

5. OTHER DESIGN CONSIDERATIONS

Unlike other riser concepts, FSHR engineering design requires clear and extensive interfacing with procurement, fabrication, and installation. Due to the complexity of the system, some local components have been identified as long lead items (e.g. forged components), which require the procurement to be in place as soon as possible in order to maintain overall project schedule. For a specific application, connectors or other components (e.g. the doghouse) may require certain qualification or full scale fatigue testing (e.g. C class fatigue welding, sweet & sour service), which takes time. Meanwhile, installation methodology may have a significant impact on engineering design, which requires early definition to minimize the design and fabrication changes. Installation aids required by the installation method need to be accommodated at an early design phase to avoid potential impact on project schedule, change orders, and cost. 6. CONCLUSION Significant accomplishments have been made through the successful delivery of the five FSHRs for the Cascade & Chinook development. Engineering design of the Cascade & Chinook riser system required sound understanding not only of the performance of the FSHRs but also the relationship between procurement, fabrication and installation. Engineering efforts need to be coordinated in a logical way. Sound design basis and methodology is also a key to success. Interface design and management is of particular importance for FSHRs.

OTC 21338 17

The lessons learnt for sharing with future similar projects are: Engineering efforts need to be coordinated in a logical way; Sound design basis and methodology is a key to success; FSHR system is weight sensitative, proper weight control and management is critical; Installation methodology has significant impact on local design of the FSHR, early alignment between

design engineering and installation is necessary; FSHR interface loads need to be generated early in a conservative way to local component design. Proper

modeling of the FSHR system to contact global analysis is important; Constructability of FSHR local component needs to be accommodated during engineering design, e.g. the

diameter of buoyancy can; Interface design and management is of particular importance for FSHRs.

7. ACKNOWLEDGEMENTS The authors would like to acknowledge Petrobras America Inc. and Technip for permission of publishing this paper. We also wish to acknowledge the enthusiastic and hard working engineering team from Technip for their excellence and support from Petrobras, which is also a key factor for the successful engineering execution. 8. REFERENCES 1. API RP 2RD (1998): Design of Risers For Floating Production Systems (FPSs) and Tension-Leg Platforms

(TLPs) 2. DNV OS F201: Dynamic Risers, 2001 3. Lacour, A, Luppi, A., Espinasse, P., Pattedoie, S., Song, R., et al: Development and Installation of the

Roncador P52 18 Free Standing Hybrid Riser in Campos Basin, 1800m of water depth, MCE Deepwater Development Conference, April 2008, France

4. Song, R, Stanton, P, Zhou, X: Engineering Design of Deepwater Free Standing Hybrid Riser, Proceedings of OMAE 2010, OMAE Paper #20600, Shanghai, China