Bertrand Lanquetin, Supports and Marine Terminals Expert, TotalFinalElf

Transcription

1 PROGRAMME GASTECH 2OO2 Bertrand Lanquetin, Supports and Marine Terminals Expert, TotalFinalElf B. LANQUETIN joined TOTAL in 1976, specialising in marine techniques for oil and liquefied gases (SPM, FSO, etc.). After 9 years of expatriation in Asia he has been appointed in 1993 Technical Manager of the Gas Shipping Department of the TOTALFINAELF Gas & Electricity Division, accumulating 15 years of experience in liquefied gas, acquired abroad and at head office, and covering shipping and terminalling (design, construction, operations of ships and terminals, ship/shore interfaces and regulations, followup of R&D programmes). In 2001 he has been appointed Floating Supports and Marine Terminals Expert of the TOTALFINAELF Exploration & Production Division. B. LANQUETIN is the author of several articles and papers. He continues to be Member/Chairman of several working groups in the oil & gas industry. He was until May 2002 the Chairman of the SIGTTO s General Purposes Committee. He is graduated from ENSTA (French Maritime High School). Pierre-Luc Lanteri-Minet, R&D Program Manager, Gaz de France Pierre Luc LANTERI-MINET entered Gaz de France in He has an interesting professional experience in the Transmission Division. He has been successively district manager for regional natural gas network, and manager of an underground natural gas storage salt cavities. He joined the Liquefied Gases Department in He was involved in the implementation of Digital Control System for process control and safety at Gaz de France s two LNG receiving terminals located at Fos and Montoir. He was also involved in the revamping of Fos LNG terminal. He drafted safety studies for French local authorities as LNG plants technical audits. He joined the international subsidiary company SOFREGAS in 1998 as project manager for LNG terminal feasibility studies. Since 1999 he is head manager of the Cryogenic Studies Section at Nantes, part of GAZ de FRANCE s Research and Development Division, which is in charge of the LNG R&D program and from 2001 manager of the R&D LNG program. Pierre Luc LANTERI-MINET is graduated from the French Mining School. Bernard Du Pont, Director, Eurodim Bernard DUPONT has been developing design of single point workings within E.M.H. Then headed Technical Management of very large M&E projects including Channel Tunnel for SPIE BATIGNOLLES where he finally headed transportation Department before joining EURODIM in 1998 as an associate and Director. Bernard DUPONT is Graduated Engineer from Ecole Nationale Supérieure des Arts et Métiers.

2 LIQUEFIED GAS TRANSFER AT SEA Bertrand Lanquetin Floating Supports and Marine Terminals Expert TotalFinaElf 24, cours Michelet La Defense Paris La Defense Cedex France Pierre-Luc Lanteri-Minet R&D LNG Program Manager Gaz de France 361 avenue du Président Wilson BP Saint-Denis La Plaine Cedex France Bernard Dupont Director EURODIM s.a. 21 Avenue Edouard Belin Rueil Malmaison Cedex France ABSTRACT Since they exist, the traditional jetties are all based on the same design: a loading platform, several mooring and breasting dolphins and a trestle linking the jetty to the shore and supporting the transfer lines. These jetties consist of huge structures extending over 350 meters overall length with a cost becoming largely prohibitive as soon as the trestle length exceeds one or two kilometres. Due to the fact that these jetties are mono-directional, they require a sheltered area to avoid that the mooring forces become too high. Furthermore, many jetties require a turning basin and, often, a navigation channel. Four tugs are necessary to perform the marine operations. Today the new LNG plants (vaporisation or liquefaction) are much more widely dispersed in the world and are accompanied with siting problems. In some cases the siting constraints, such as congested areas or shallow waters, impose the jetties to be located at some more remote areas and further weather exposed locations. In many cases a breakwater is necessary. Many gas companies have been very active in trying to reduce the cost of the LNG chain including bigger storage tanks, bigger trains, bigger and more efficient ships, etc., but so far nothing substantial was done with respect to the transfer facilities themselves. For this reason TotalFinaElf, Gaz de France, Eurodim and several other French companies, have carried out, since 1999, an extensive programme of studies of new architectures for LNG transfer (and other liquefied gases) together with an ambitious programme of development and test of the main cryogenic components like the subsea lines, the transfer hoses and the connecting and disconnecting systems. These innovative solutions are presently in the pre-industrial stage and the first half of 2003 should see the termination of the studies and tests of components through various associations and Joint Industrial Programs (JIP). These transfer technologies (and more specifically the cryogenic hose with the connector) are also suitable for offshore LNG transfer such as tandem offloading. This paper therefore gives the state of the art of the technology of liquefied gas transfer at sea. Priority in these developments has been given on non-dedicated ships and to safety levels equal to or above those of the traditional jetties.

3 LIQUEFIED GAS TRANSFER AT SEA PART 1: TRADITIONAL DESIGN OF LOADING/UNLOADING JETTIES Traditional design All the loading/unloading jetties for liquefied gases today (mainly LNG Liquefied Natural Gas and LPG Liquefied Petroleum Gas) use very similar designs including: - A fixed orientation. - A trestle between the jetty and the shore, which supports the liquid and vapour lines and very often an access/egress road. - A loading (or unloading) platform often with two or three levels, which supports the loading (unloading) arms and the fire protection. - Two to four breasting dolphins for berthing the ships. - Six to eight mooring dolphins for mooring the ships. These jetties necessitate a very large number of piles and a lot of civil and marine works, the cost of which becomes rapidly prohibitive when the distance to the coast increases. This design presents several drawbacks such as: - Proximity of the coast is necessary. - The site has to be sheltered. - The breasting dolphins have to be sized so that one dolphin only has to absorb all the berthing energy of the ship, which generates a reaction force on the dolphin of 250 to 350 tons for 135,000 m 3 ships. - The mooring dolphins have to be sized to withstand the efforts of wind, waves and current on the moored ship. For indicative purpose the lateral force generated by a lateral wind of 30 m/s (60 knots) is in the range of 500 tons for a 135,000 m 3 ship. Accordingly such forces require typically sixteen to eighteen mooring lines (four spring lines and two groups of three to four breast lines fore and aft). - A limited depth. - Four tugs of approximately 4,000 HP (sometimes three but more powerful) are required for turning, berthing and unberthing manoeuvres of 135,000 m 3 ships. - High capital and operating costs. These constraints make difficult the research of an appropriate site for the loading (unloading) jetty. Very often it is necessary to provide an access channel with navigational aids and a turning circle in front of the jetty (diameter about 700 m for 135,000 m 3 LNG ships), which may have to be dredged. In many instances a breakwater has to be provided as well in order to provide a calm stretch of water in front of the berth. Finally navigational risk is a concern as well as disturbance of the ship at berth due to passing ships. Siting constraints and risk management is such a constraint that SIGTTO Society of International Gas Tanker and Terminal Operators has developed a set of guidance (to be published end of 2002) called LNG Operations in Port Areas. Further information related to siting problems of traditional liquefied gas jetties is given in References [1], [2] and [4]. An artist view of a loading jetty is given on Figure 1. Lanquetin, Lanteri-Minet, Dupont 2

4 Figure 1: Artist view of Bontang 3 rd LNG/LPG jetty (commissioned in 1999) (Source, see Reference [3]) Background of this traditional design Contrarily to the oil industry where the concept of SPM (Single Point Mooring) has been introduced very early and has been progressively refined to adapt to more challenging environments (such as deep water and harsh environment), allowing also to move from coastal to open sea fluids transfer installations, the architecture for transfer of liquefied gases has not changed since the very beginning (one exception was the Brunei Lumut 1 stern loading system developed by Shell, which has been now decommissioned). This is easy to understand if one reminds the two main functions of any loading facility: - Safe mooring of the ship. - Safe transfer of the product (and in case of liquefied gas safe transfer of the vapor return). Any more compliant system, i.e. a system allowing for example: greater depth, greater distance to the coast line, weather exposed environment, not talking about open sea, would require a system if mono directional allowing greater excursion of the moored ship, or a system with weathervaning capabilities. These systems imply in turn: - A submerged cryogenic pipe (in radius of about one nautical mile around the SPM) and a cryogenic swivel (for the weathervaning systems). - Possibly a more compliant transfer path between the platform and the ship manifold allowing greater excursions and ship movements, while allowing the same functions of easy connecting/disconnecting operations in normal operating conditions and ESD/ERS (Emergency Shut-Down/Emergency Release System) functions in emergency situations and similar ship/shore links (ESD, etc.) compared to traditional jetties. - Besides, the question of dedicated versus non-dedicated ship is coming very quickly if one starts to consider those systems. Clearly, the LNG industry was not ready until recently to take any step towards any more compliant transfer system. The consequences are also going beyond the jetty design because the ships themselves are designed to moor at jetties and are allowed with only limited movement at berth to comply with arms Lanquetin, Lanteri-Minet, Dupont 3

5 mechanical envelops. In turn big LNG ships have in general standard sixteen to eighteen steel mooring lines diameter 36 to 42 mm and MBL say 100 to 110 tons in average. The winch break holding capacity is in the range of tons, which in turn explains why the OCIMF (Oil Companies International Marine Forum) mooring guidelines recommend that the maximum tension in the mooring line should not exceed 55% of the MBL of the line. This also probably explains why no wave effect is taken into account in the OCIMF mooring guidelines. Many efforts have been deployed since years in studies and new developments in the field of the LNG chain cost reduction. But they have been generally focusing to the plants and the ships and not to the loading or receiving facilities, contrarily to the oil industry where this field was very early pioneering with the quick development of companies such as Bluewater, EMH, Imodco, SBM, Sofec, etc., and several breakthroughs in new technologies covering hydrodynamics and new components (such as hoses, hawsers, multi-path swivels, etc.). We consider that there is a real possibility of significant cost reduction if we encompass the whole question of marine terminal and LNG plant siting. To remain brief, a good site should combine: - A good site for the plant (soil conditions, topography, neighbouring, etc.). - A good site for marine terminal operations (sheltered, absence of or limited other traffics, etc.). - A minimum distance to the gas fields or to the consumers (to reduce the length of pipelines). Proximity of the field/market is a must. These criteria are generally not compatible and the site selection is usually a compromise between all these constraints while preserving the safety (navigation, cargo operations and plant). It is easy to imagine that if one of the constraints could be softened, then the whole economy of a project could go far beyond the cost saving done on one component like the transfer facility. Accordingly a group of French companies embarked in years in an ambitious R&D programme in the field of LNG transfer at sea, namely TotalFinaElf, Gaz de France and Eurodim. Several systems have been tested against mooring calculations using powerful dynamic computer models. At the same time reputable companies have been working on the development of components. The cryogenic pipe and the cryogenic hose have been fully tested and manufacturing process established. The connecting/disconnecting procedures were further studied in 2001 and the design has been done of a light connecting/disconnecting device for severe environmental conditions, which will be fully tested early 2003 through a JIP on a full-scale prototype. Finally, the design of a 24 cryogenic swivel with a second path allowing the vapor return has been made and a prototype should be built and tested in The target was initially to fill the gap of absence of new technologies in the field of fluid transfer and to propose new attractive and more compliant designs, but it appeared very quickly that these technologies were also able to well deserve other fields of interest such as tandem offloading transfer on a FLNG (Floating Liquefied Natural Gas plant) at sea. PART 2: NEW ARCHITECTURES OF LIQUEFIED GAS TRANSFER AT SEA Foreword All the R&D we have done on the new architectures and components are for LNG and are applicable for both loading and receiving facilities. Although we will only consider LNG in this paper, it is clear that the concepts are valid for other liquefied gases and other fluids. New architectures of liquefied gas transfer The first goal of the R&D program was to propose alternatives solutions to traditional jetties, including studies and tests of critical components. The governing lines for this project developed initially by TotalFinaElf, Gaz de France, Eurodim and ITP InTerPipe were: Lanquetin, Lanteri-Minet, Dupont 4

6 - To be able to have the facility at some distance from the coast, i.e. with no more navigational and siting problem (major criteria). - To be able to load (unload) non-dedicated ships (major criteria) at 10,000 m 3 /hour. - To obtain significant cost reduction by replacing a costly trestle by subsea lines (major criteria) and by using cryogenic hoses for the product transfer as an alternative to hard arms. - To have a safety level equal or above the one of traditional jetties. An illustration of these unconventional schemes is given in Figure 2. This figure shows how these various mono-directional and multi-directional systems can be used in mild, medium and severe environments. These systems and their hydrodynamic performances will be described hereafter. Conceptual design of these various systems is being completed for the end of this year. Figure 2: Classification of alternative solutions to traditional jetties In view of the promising results obtained with the cryogenic hose and the light connector, we have envisaged an extension of such systems to ship to ship transfer. A prototype test of a connecting system in severe environmental conditions will be carried out in the first half of 2003 through the JIP Amplitude- LNG (see PART 3) Alternatives to traditional jetties Conventional mooring associated to cryogenic subsea line and hose: Gerris This concept was first studied in order to establish its feasibility (and in particular the connection/disconnection device on a non-dedicated LNG ship) and to make cost comparison analysis Lanquetin, Lanteri-Minet, Dupont 5

7 between this system and a traditional jetty with two trestle lengths 2,500 m and 5,000 m. The governing lines for this project were: - To be able to have the facility at some distance from the coast, i.e. with no more navigational and siting problem (major criteria). - To be able to load (unload) non-dedicated ships (major criteria). - To obtain significant cost reduction, particularly beyond some distance from the coast (say beyond 2,000 m) by replacing a costly trestle by submarine lines (major criteria) and by using cryogenic hoses for the product transfer as an alternative to hard arms. - To take advantage of the transfer cryogenic hoses flexibility (ability to accept a bigger envelop of ship flange connection) in order to derive a more compliant system for the loading/unloading jetty. An illustration of this unconventional scheme is given in Figure 3 and the system is fully described in References [5] and [7]. as a Gerris Figure 3: Artist views of a the Gerris LNG transfer system (Eurodim patent pending) It has to be noted that no study of hydrodynamic behaviour of the ship alongside the berth has been performed on this system because it is assumed that the behaviour and the operating thresholds of the ship at berth are the same as the ones of a traditional jetty. The study of this alternative to traditional jetties has shown its feasibility and its significant economical advantage for the fluid transfer system and its infrastructure. It also has led us to believe that utilisation cryogenic hose technology should allow such amplitude of movements of the LNG carrier that LNG transfer in more exposed locations could be envisaged Research of transfer solutions for exposed locations Envisaging such LNG transfer in exposed locations by more compliant systems, offers to imagination a large number of potentially interesting concepts, which have to be screened with the following approach. Lanquetin, Lanteri-Minet, Dupont 6

8 Basically, the conceptual design of the marine LNG transfer facility is dictated by its two essential functions: - Safely mooring the LNG carriers. - Safely transferring the fluids (LNG and vapor). a) Mooring of the LNG carrier The mooring principle and performance will be determined by the type of environment and, at some degree, by the water depth. Mooring infrastructure will be minimised when the mooring allows the LNG carrier to face the environmental elements. Hence two families of solutions can be envisaged: - Mono-directional environment: it allows direct extrapolation of the sheltered concept to a Conventional Buoy Mooring, solution possible thanks to the flexible hose level of compliance. - Multi-directional environment: it imposes mooring solutions allowing weathervaning of the LNG carrier. In all cases the solutions have to trade off: - Minimisation of ship movements to optimise compliant fluid transfer system. - Minimisation of mooring infrastructure generally calling for reduced mooring stiffness and ship movement increase. For weathervaning solutions design must cope with the following imperative principle constraints: - Ship mooring system must allow 360 rotation around some vertical axis. - Compliant fluid transfer system must link in any position midship manifold (in case of non-dedicated ships) and pipe fixed end. This seems to allow an infinite number of solutions. In practice the solutions in line with those demanding criteria are very limited for LNG with the present foreseeable technology when looking at the possible locations of LNG transfer system axis of rotation: - Solution type A, rotating around a vertical axis ahead of LNG carrier bow, tends to optimise mooring, in particular as this vertical axis is targeted to be in the ship medium plane (Figures 4A and 4B). Fluid path Figures 4A and 4B: Location of system axis of rotation in solution type A Lanquetin, Lanteri-Minet, Dupont 7

9 - Solution type B, rotating around a close to manifold vertical axis, tends to optimise the compliant part of the piping (Figures 5A and 5B). Fluid path Figures 5A and 5B: Location of system axis of rotation in solution type B Amongst all the solutions for the location of the axis of rotation in the horizontal plane, see Figure 6, apart from point B (solution type B), only the longitudinal axis of the ship looks interesting to allow the weathervaning of the ship. On the longitudinal axis, solutions between Sb (bow) and Ss (stern) need a submarine swivel joint or to have it maintained somehow above the ship. Increase ASb (or A'Ss) above optimum mooring distance of hawser or flexyoke, etc. only elongates the compliant fluid transfer system length and is therefore detrimental to its optimisation. y B x A Sb Ss A' x' Figure 6: Location of system axis in the horizontal plane Possible mooring principles for solution type A: - Mooring flexible yokes or arms have not been considered to avoid LNG carriers significant conversion as well as mechanical complexity. - Hawser soft mooring on a fixed tower is a simple and classical solution with good track record in crude oil offshore offloading or even for permanent mooring of FSO (Floating Storage Offloading), like CAYO ARCAS (Figure 7A) or FPSO (Floating Production Storage Offloading), like WEIZHOU (Figure 7B). Lanquetin, Lanteri-Minet, Dupont 8

10 PEMEX CAYO ARCAS fixed tower mooring FSO TOTAL CHINA WEIZHOU fixed tower mooring FPSO Figures 7A and 7B: Examples of existing hawser mooring on a fixed tower b) LNG transfer system For the LNG transfer system, compliant or partly compliant fluid transfer systems linking midship manifold and fixed pipe could be: - Submarine concepts would have the following drawbacks: Submarine LNG hoses: not existing. Submarine LNG swivels: not existing. In such shallow waters wave loads on structural members are significant. Water added mass has to be taken into account in natural oscillation or vibration modes. - Floating concepts present the following difficulties: Floating LNG hoses: under development, not yet available. Pipes and structures are directly subject to wave action. Influence of the water added mass. - Aerial concept present no fundamental difficulty: Aerial LNG hoses and swivels technologies are available. Basic loads are only wind and structural weight. Therefore this basic screening of possible solutions shows that for general purpose LNG transfer facility three new concepts are particularly promising: - The Conventional Buoy Mooring (mono-directional, therefore somehow mild weather conditions). - The rotating quay (solution type B, medium weather conditions). - The Aerial Fluid Path SPM (solution type A, severe weather conditions). These three solutions have been studied and are described hereafter Conventional Buoy Mooring In case of sites with prevailing environmental conditions combinations predominantly orientating the LNG carrier in one direction, in statistical terms mono-directional, the mooring concept generally called Conventional Buoy Mooring (sometimes called Multi Buoy Mooring) appears to be of interest for LNG transfer facilities. This is due to the fact that the mooring forces of the ship, instead of being transmitted to the numerous piles of the mooring dolphins (traction) and breasting dolphins (compression via fenders), are transmitted by the ship mooring lines to the multiple mooring buoys themselves anchored to the seabed by chains in catenary configuration for instance. Lanquetin, Lanteri-Minet, Dupont 9

11 Such system has the advantage to carry the mooring loads in an optimised manner from a structural stand point, as no bending moment is generated in the structural link (contrarily to the conventional dolphins) but only pure traction. Furthermore, this catenary structural link provides the advantage to be a cheap spring enabling to tune, at the engineering stage, the stiffness of the mooring system to trade off, as required, the peak mooring loads and the ship amplitude of movements to match with the capacity of deflection of the fluid transfer system. In the absence today of a reliable technology of submarine compliant piping from seabed to surface, in all cases for this type of mooring, architectures of fluid transfer system comprise necessarily a fixed tower riser (or support) linking sea bed/subsea cryogenic lines for LNG and vapor return line (or trestle with aerial lines) with the aerial cryogenic hoses. These flexible hoses are hanging in a catenary configuration between a cantilever boom supported by the fixed tower and the LNG carrier midship manifold during LNG transfer or below the boom during storage. Depending on the site environmental conditions and in particular of the level of occurrence and/or value of the possible transversal effect of wind and/or current, the pattern of the location of the fixed tower and its boom can be optimised together with the stiffness of the moorings. It ranges from an arrangement (Figure 8) where the boom is perpendicular to the longitudinal axis of the moored LNG carrier with the hoses underneath, to an arrangement (Figure 9) where the boom is quite parallel to the longitudinal axis of the ship and pivoting around a vertical axis with the hoses linking the boom tip to the midship manifold in a similar way as the one developed for the SPM concept Aerial Fluid Path (see ). Figure 8: Artist view of a Conventional Buoy Mooring with the associated LNG transfer system, boom perpendicular to the ship longitudinal axis (Eurodim patent pending) Lanquetin, Lanteri-Minet, Dupont 10

12 Figure 9: Artist view of a Conventional Buoy Mooring with the associated LNG transfer system, boom quite parallel to the ship longitudinal axis (Eurodim patent pending) Clearly the CBM concept is attractive for the LNG transfer in open sea for sites with mild and somewhat mono-directional environment as: - It saves on cost and planning when compared to traditional terminals, notably thanks to drastic marine works and piling reduction. - It is comparatively less sensitive to water depth increase. - It is based on an experienced mooring concept. - It is simple and efficient thanks to the use of flexible hose and connection device developed under the JIP Amplitude-LNG (see PART 3) Rotating quay We have imagined and developed a system, which combines the advantages of: - A traditional jetty: safety, reliability, components using a proven technology, non-dedicated ships. - A SPM: remoteness from the coast, cheaper cost, higher operating thresholds due to the weathervaning capability. This rotating quay has been patented by TotalFinaElf in January This system is fully described in Reference [8], therefore we give hereunder a summary of the system description. In the proposed system, the jetty is replaced by a revolving quay, which is mounted around a vertical axis on a fixed supporting structure. The fixed structure is connected to the shore by subsea cryogenic lines at least for the section near the rotation quay (say one nautical mile). The system allows a tug to position the quay parallel to the ship approaching direction, then to maintain the ship in the direction of less environment efforts once moored on the quay. In case of emergency, quick departure can be achieved with a very high level of safety and reliability. An illustration of the system is given on Figures 10 and 11. Lanquetin, Lanteri-Minet, Dupont 11

13 Transfer system Revolving quay OVERALL VIEW OF THE CONCEPT Subsea cryogenic lines to/from shore (both liquid and vapour lines possible) Fixed supporting structure Mooring lines Figure 10: Artist view of the rotating quay for loading/unloading LNG ships Figure 11: Artist view of the rotating quay for loading/unloading LNG ships showing the tug pulling permanently on the bow of the ship This concept is in line with the objectives we have set for all of the liquefied gas transfer architectures, i.e.: - Serving non-dedicated ships. Lanquetin, Lanteri-Minet, Dupont 12

14 - Applicable for both loading and discharging terminals. - Able to handle any type of liquefied gas. - Flexibility with regard to depth. - More compliant than a traditional berth with regard to weather operating thresholds. - Reducing significantly the overall cost compared to traditional jetty design. - Eliminating in the same time the navigational, traffic and neighbouring constraints by allowing the system to be at some distance from the coast. In addition it presents several remarkable advantages: - All components are standard and the same as the ones used on traditional jetties: mooring hooks, fenders, arms, gangway, etc. - The system uses the same rules, standards and guidelines for design as the ones used for traditional jetties: OCIMF guidelines for mooring, PIANC (Permanent International Association of Navigation Congresses) or BSRA (British Ship Research Association) standards for fender selection, OCIMF specification for loading arms, all SIGTTO guidelines, etc. - The rotating quay can support either hard arms or flexible hoses for the product transfer; the shape of the rotating quay can be adapted accordingly. - The supporting structure and the rotating quay have similar lattice structures (jacket and lattice beam) allowing a yard to build both structures at the same time. Transportation to the site can be made on two barges and installation is straightforward. Although this has not been estimated in detail, there is obviously an important reduction of the construction and installation time compared to a traditional jetty, which requires a lot of civil work and piling. It must be noted that the fixed supporting structure can have as well the form of a tower structure. The various components of the system are now described hereunder. Rotating quay: - The lattice beam has a length of m, i.e. 25 to 30% of the length overall of the biggest LNG ship (LOA # 300 m). The width is either in the range of 30 m in case hard arms are used for product transfer or m in case flexible hoses. The height of the beam is in the range of 4-5 m, sufficient for the beam to offer enough horizontal rigidity. - The lattice structure contributes to the rigidity of the beam, to a weight reduction while offering little resistance to the extreme waves and to the wind. - The elevation of the top of the beam is sufficient in order to keep the equipment on deck out of the water as it is done on a traditional jetty design. Supporting structure: - The structure is designed to absorb the horizontal force generated either by the berthing of the ship (reaction force versus berthing energy) or by the forces generated by the moored ship under the effect of the wind, waves and current. The structure is piled to the seabed in order to achieve a good stability. Mechanical part allowing a 360 rotation of the quay around the vertical axis of the supporting structure: - The rotating quay is mounted in the base case in its centre of gravity on the supporting structure. - The mechanical part allowing such free rotation is available on the market in the range of efforts considered. We give now a description on how the three main functions of the loading (unloading) system are achieved. These three functions are: Lanquetin, Lanteri-Minet, Dupont 13

15 - The ship berthing and unberthing (cast off) including unberthing in emergency situation. - The mooring of the ship. - The transfer of liquefied gases and of the vapour (if required). The ship berthing and unberthing (cast off) including unberthing in emergency situation: - On a traditional jetty it is necessary to turn the ship with usually four tugs each having a power in the range 3,800 to 4,500 HP generally prior berthing. This manoeuvre requires a turning circle of about 700 m for big ships, free from every obstacle and with a depth of 14 to 15 m. In several places this requires dredging and in all cases installation of navigational aids. Once the ship is parallel to the berthing line, the tugs are pushing the ship along side the fenders with a berthing speed not exceeding typically 15 to 20 cm/s. The berthing thresholds are limited to waves significant height of 1.2 to 1.5 m and to winds 12 to 15 m/s. - The recommendations for traditional jetties requires that one single breasting dolphin absorbs all the berthing energy while two to four breasting dolphins are usually provided. This is due to the difficulty to achieve a berthing with the ship exactly parallel to the berthing line. The dimensioning case for breasting dolphins is in most cases the reaction force resulting from the ship berthing and not the dolphin solicitations from the ship all fast alongside under the wind, waves and current. As a result the breasting dolphins are very strong and expensive structures. - The rotating quay has a system of fenders similar in principle. Four fenders (possibly two might be enough) are mounted on the berthing side of the beam in order to protect the beam during berthing and absorb the berthing energy, then to support the ship when moored alongside. However the rotating quay presents several advantages compared to a traditional jetty: a) A tug will position the beam parallel to the direction of ship approach. The ship not having to be turned, the manoeuvre is simplified and it is expected that a ship can be able to berth with higher berthing thresholds and with only two tugs for assistance. b) During the berthing manoeuvre, as soon as the shipside is in contact with a fender, the beam will naturally turn under the efforts of the ship and rapidly all the fenders will be in contact with the shipside. In turn it means that the four fenders, and not a single fender as for a traditional jetty, will absorb the energy. The reaction force on the supporting structure of the rotating quay will be in the same order of magnitude as the one on a single breasting dolphin on a traditional jetty, resulting in a similar sizing. The cost saving becomes an evidence in the concept of rotating quay: there is only one fixed structure between the surface and the sea bed compared to two to four structures similar in strength for breasting dolphins and six or more mooring dolphins plus the catwalks. - Once the ship is at berth the system is not stable under the forces generated by the elements; a tug has therefore to be tied up to the bow of the ship in order to control in permanence the orientation of the beam in the direction of less efforts. The ship unberthing manoeuvre in these conditions either in normal circumstances or in emergency is straight forward because: a) The ship is already heading in the right direction. b) The tug is in attendance. The mooring pattern of the ship: - On a traditional jetty LNG ships are moored by generally by fourteen to eighteen wire mooring lines in order to provide a sufficient restraining force. The mooring lines are divided in several groups of lines in order to restrain the ship movement under longitudinal force component: spring lines, and under lateral force component and the moment: several groups of breastlines. Each group of spring lines has two lines and each group of breastlines has two to four lines. - The mooring of big ships on a traditional jetty requires therefore in average six mooring dolphins, each being designed to support an effort of three (in case of three-hook assembly) to four times Lanquetin, Lanteri-Minet, Dupont 14

16 (in case of four-hook assembly) the SWL of the mooring lines, this represents an effort in the range of 300 to 500 tons depending on the jetty design. - In the concept of the rotating quay only eight mooring lines are necessary: two groups of two spring lines connected to hooks on the side of the beam close to the ship and two groups of two other mooring lines connected to hooks on the opposite side of the beam. This simple arrangement results from the fact that a tug is used to keep permanently the ship heading in the direction of the less efforts from the environment. Some allowance around this direction is acceptable and the preliminary calculations have shown that the heading should remain within a +/- 20 sector (moderate to severe weather conditions) or within a +/- 30 sector (mild weather conditions) around the ideal position to be on the safe side. Computer simulations described in chapter 2.2. of this paper show that the tug can easily maintain the ship within such stability cone. Outside these sectors the transversal component of the efforts are beyond the capability of the mooring pattern. - Here again the cost saving is evident compared to a traditional jetty: no mooring dolphins, only four sets of two-hook assemblies are required. - Quick Release Hooks (QRH) are used like on traditional jetties. In case that the tug has a failure, the second tug (two tugs are required for berthing the ship), which is on stand-by during loading (unloading) operation of the ship, will provide the necessary assistance. In the improbable case where the two tugs have a failure or that the ship cannot stay in the required sector for the direction, then the ship will have to be disconnected in emergency using the ERS (Emergency Release System) for the hard arms (or flexible hoses) followed by the activation of the quick release hooks. There is therefore a way to protect the facility even in case of a catastrophic scenario as described above. - Finally it has to be mentioned that it is not necessary to apply a big pre-tension in order to maintain the ship stuck to the fenders. At the contrary the system has to be compliant in order to absorb as much as possible the high frequency movements of the ship in the waves. A view of the mooring arrangement is shown on Figure 12. Figure 12: Artist view showing the mooring pattern (on this figure, traditional arms are used) Lanquetin, Lanteri-Minet, Dupont 15

17 Aerial Fluid Path SPM Similarly to what is done since many years in the oil industry and following the logic of our research (see chapter ), the concepts based on SPM appear attractive for LNG transfer. Total, now TotalFinaElf, has been associated in the past (more than twenty years ago) in the CHAGAL program (CHAGAL for chargement de gaz liquéfiés ). The project was based on the development of a cryogenic SPM of CALM type (Catenary Anchor Leg Mooring) for loading LPG, which required subsea flow-lines and PLEM (Pipeline End Manifold), flexible hoses and a cryogenic swivel to be designed and tested. A 8 cryogenic hose was designed and tested by Coflexip, now Technip-Coflexip, while a 16 cryogenic swivel was designed and tested with Forane. The development of this swivel was made by EMH and it was further developed and tested successfully for LNG application before patent and technology were taken over by SBM. As submarine cryogenic hose is still not available and as mooring thresholds can be high, the SPM concept had to face two engineering challenges: - The transfer between the SPM and the ship in case the ship is not dedicated. Because the technology of a floating cryogenic hose is not available, an aerial transfer system has to be considered, which calls for a specific structural design due to the distance of the SPM to the ship manifold located midship. - The operational thresholds of the ship moored on a SPM are the highest of the concepts we have studied and presented above. As a consequence and to take fully advantage of these excellent performances, the connection/disconnection principles in normal operating and in emergency conditions were the key of such a concept and constituted a real technological challenge, which once resolved successfully, appears to be also the solution of connection for all the above architectures. The Aerial Fluid Path (Figure 13A) for non-dedicated LNG carriers is a long horizontal boom, approximately 220 m long, rotating around the vertical axis of the fixed tower type of SPM. The length of the boom allows to reach the midship manifold. The boom is 50 m above sea level to keep free the space necessary for the spherical tank LNG carriers. Figure 13A: Artist view of the Single Point Mooring with the associated LNG transfer system Aerial Fluid Path (Eurodim patent pending) Lanquetin, Lanteri-Minet, Dupont 16

18 Fluid link between hard piping at the tip of the boom and the midship manifold is carried out with flexible hoses. During transfer, when flexible hoses are connected to the ship manifolds, the boom is free to rotate and is driven thanks to the horizontal component of the resulting forces acting on the boom tip ( free wheel mode). A specific patented arrangement (Figures 13B and 13C), consisting, for each flexible hose, of a beam supported at one extremity under the boom thanks to cables and at one other extremity by the flexible hose end-fitting, allows to keep the curvature in the flexible hose below the maximum allowed. The whole system allows to drive the boom during transfer by application of the loads directly on its central axis. Figures 13B and 13C: Views of the hoses arrangement The design of such a self-supporting structure of the Aerial Fluid Path has been the result of a long iterative process. During its development, it appeared that the governing aspect would be the structural dynamic behavior. Due to the significant dimensions of the structure, the use of standard structural shapes such as those of heavy industrial cranes revealed to be unacceptable, leading to very large fundamental periods for natural vibration modes (T > 10 s). In order to ensure a healthy behavior of the structure under natural dynamic modes, we defined a conservative maximum limit of 2 seconds for the fundamental periods of the structure. To achieve that, we progressively redistributed the matter in space in order to obtain a more compact structural form for the whole structure as well as we used techniques relevant for modern bridges with significantly longer freespan. The main developments have been: the doubling of booms to obtain a progressive structure with shorter cables, the use of Y-shaped booms to create a 3D out-of-plane behavior, and the design of a pyramidal kernel federating the whole dynamic behavior of the structure by fastening it on the main pylon (Figures 14 and 15). The result is a naturally balanced and slender structure which is stiff enough to fulfill the hard operational requirements of offshore loading in marine environment. Lanquetin, Lanteri-Minet, Dupont 17

19 It has to be noted that such light structure and architecture is sound and valid as it is fixed and directly bearing on the seabed (either as gravity structure or piled one), and that its extrapolation to floating support is not envisaged. Figure 14: First natural vibration mode of the structure calculated with ISYMOST/STRUDL Figure 15: Second natural vibration mode of the structure Lanquetin, Lanteri-Minet, Dupont 18

20 After study of this concept it appears that: - The ideal ship freedom allowed by the Aerial Fluid Path maximizes safety with regards to shocks and operating thresholds. - It allows infrastructure cost and construction time reduction. - It has a good mooring track record with minimal tug requirement (two tugs maximum). - It needs no underwater mechanical equipment Hydrodynamic behaviour of the ship at berth and limit operating thresholds for these new concepts 3D numerical simulations of the hydrodynamic behaviour of these three mooring architectures, CBM, rotating quay and Aerial Fluid Path SPM, have been carried out by PRINCIPIA using DIODORE software. The main characteristics of these calculations were: - The LNG carrier was a five spherical MOSS type tanks with a total capacity of 137,500 m 3. - Time domain simulations were three hours actual time (extended in 10 hours in some calculation cases on the rotating quay). - Calculation have been made with irregular wave (Jonswap spectrum with a severe γ=3.3) and wind with gust (Harris spectrum, gust peak speed about 1.5 the average speed). As an example, we present the results obtained with the environmental conditions given in the hereafter tables for the rotating quay. The results presented are the evolution of tug pulling and the quay rotation with time (see Figure 17). At the beginning of the simulation, the ship is inside the safe stability cone (see Figure 16). The tug pulling is adjusted to keep the ship inside this area. To our knowledge, no such kind of simulation with active input of the operator has been done before. Eccentric rotation axis MECHANICS Moment on ship Safe stability cone Wind, current and waves Tug pulling requirement Figure 16: Mechanics of the rotating quay Lanquetin, Lanteri-Minet, Dupont 19

21 CAS E4 Yaw lacet 3.5E E E E E E E E E E E+00 Time Temps (s) (s) 6.0E E E E E E+00 Tension au Tug pulling (N) remorqueur (N) Figure 17: Evolution of tug pulling (in purple) and quay rotation (blue) with time This study allowed to evaluate the mooring loads and the relative movements between ship manifold and transfer system for various cases of waves, wind and current combinations. Simulations have shown good performances of the ship at berth for the following environmental conditions: Wave Wind Current Hs Average speed / Peak speed CBM 2 m 25 m/s / 36.5 m/s 1 kt Rotating quay 3.5 m 25 m/s / 36.5 m/s 2 kts Aerial Fluid Path SPM 4.5 m 25 m/s / 36.5 m/s 2 kts For reference, the usual limit thresholds for a ship at berth on a traditional jetty are the following: Wave Wind Current Hs Average speed Traditional jetty About 2 m 20 m/s About 1 kt 2.3. State of the art of tandem offloading systems This is also a difficult case when the environmental conditions are severe: the transfer system of the liquefied gas between a LNG ship and a floating LNG plant. TotalFinaElf is operating a tandem offloading of a LPG FSU (Floating Storage Unit) with a floating hose on Nkossa 2 field in Congo. Several designs are studied and proposed: the Big Sweep from Bluewater, the system based on boom and cryogenic hoses from ExxonMobil and from Statoil, the BTT from FMC (Boom To Tanker), the LNG offloading arm from SBM, the articulated transfer arms with jumper from Kvaerner, etc. Another new system, the Light Reel, currently under study by Eurodim for Bluewater, is briefly described hereafter. Lanquetin, Lanteri-Minet, Dupont 20

22 Generally the question of coupling/uncoupling the device to the ship manifold in routine and emergency operations and of the link between ship and FLNG such as ESD link needs also further studies so that the systems gain the same level of safety and reliability as traditional jetties (see Reference [6]). To this regard telemetry is contemplated, associated with advanced positioning systems for alarms 1 st and 2 nd step detection. The Light Reel (see Figures 18 and 19) offloading system is composed of one reel bearing on the stern of the FLNG around which the cryogenic hose is wounded. The radius of the reel (approx. 16 m) allows to store 100 m of hose in one turn. Rotation of the reel around vertical axis Reel Rotation of the reel around its horizontal axis Guidance system Rotation of the connecting structure around vertical axis FLNG Offloading carrier Figure 18: Light Reel description (Bluewater and Eurodim patents pending) Figure 19: Artist view of the Light Reel LNG transfer system Lanquetin, Lanteri-Minet, Dupont 21

23 In transfer, the hose is connected to a connecting structure on the bow of the LNG carrier, clamped with a built-in angle compatible with the catenary shape of the hose. Both the reel and the connection structure on the LNG carrier are able to rotate around a vertical axis allowing the system to work permanently in a quasi-vertical plane. The length of the catenary is adjusted in transfer by rotating the reel around its horizontal axis. An articulated system allows to guide the hose in the rim. The two vertical axis swivel joints are to cope with possible large relative angles (α and θ) between the two vessels. The principle of the kinematic is shown on Figure 20. θ FLNG α Offloading carrier Figure 20: Kinematic principle of the system catenary with vertical axis swivel joints Thanks to these swivels, angles α and θ are not relevant parameters for the hose configuration. The catenary remains in a quasi-vertical plane in all the envelope of relative motions. Only roll and pitch of the vessels and transversal wind induce low torsion and 3D bending in the hose. To cope with large relative displacements, the reel allows to adjust the length of the catenary during the transfer. The constraints to adjust the length of the catenary are: - To keep the flexible hose above the sea level. - To keep the bending radius of the hose above the minimum allowed in operating conditions. It should be noted that each swivel joint (two on the FLNG and one on the LNG carrier) is subject to very slow motions only and no dynamics at wave frequency for instance. PART 3: KEY COMPONENTS FOR THESE TRANSFER ARCHITECTURES These transfer architectures require four key components: - The subsea cryogenic pipe. - The cryogenic flexible hose. - The light connecting system. - The coaxial swivel joint. Lanquetin, Lanteri-Minet, Dupont 22

24 We give here a short description of these four key components. Patented novel cryogenic submarine pipe developed by ITP InTerPipe The Figure 21 gives the composition of the multi wall cryogenic subsea pipe. Insulation material IZOFLEX Pipe 2: Steel sealing barrier Pipe 3: Steel Pipe 1: INVAR Figure 21: LNG subsea cryogenic pipeline (developed by ITP InTerPipe) A representative spool of internal diameter 800 mm and length 8 m was successfully tested with LNG in April 2001 (see Figure 22) in Gaz de France Cryogenic Studies Section at Nantes (France). Figure 22: Insulation LNG test in the Gaz de France Cryogenic Studies Section at Nantes (France) Lanquetin, Lanteri-Minet, Dupont 23

25 Main features are as follows: - A double wall technology currently used on subsea HP/HT (High Pressure/High Temperature) projects (the double wall type technology has been first developed for Total by ITP InTerPipe on Dunbar in 1992, then used as well on Shell Etap and Elf Tchibeli projects). - An internal pipe in INVAR (nickel alloy with 36% Ni) with no loops or expansion joints (this material has an extremely low dilatation coefficient, which combines with its mechanical strength, a high tenacity and good welding characteristics). Therefore no dilatation loop is required on the line. - The best insulating material IZOFLEX thus reducing the size of external pipe (the IZOFLEX material has been developed and patented by ITP InTerPipe). The thermal performances of this material were confirmed by full-scale thermal tests carried out in Houston by a JIP led by Texaco associated with BP, ExxonMobil and TotalFinaElf. Since, mechanical testing of this material in cryogenic environment has been carried out during the design phase of this project and has confirmed the suitability of the material for LNG transport operations, see Figure The annular is continuous. - The external pipe is made of regular carbon steel to handle massive external aggression for additional protection and pipe stability. - An intermediate sealing barrier made of steel pipe is integrated for safety enhancement. To our knowledge the competition is with Logstor who has tested cryogenic pipes in smaller diameters. Cryogenic flexible transfer hose developed by Technip-Coflexip An 8 cryogenic flexible was designed and tested in the past by Technip-Coflexip. More recently Technip-Coflexip has promoted a JIP for the development of a 16 cryogenic hose (see description Figure 23) to be used for loading/offloading, near-shore and offshore LNG transfer scenarii. Participants in this JIP were BP, BHP, Chevron, Gaz de France and Shell. Corrugated hose Armours layers Spiral layer Insulation foam Intermediate sheath Insulation foam External sheath Figure 23: Composition of the Technip-Coflexip 16 cryogenic flexible hose (developed in , tested in ) Lanquetin, Lanteri-Minet, Dupont 24

26 This hose has been tested under cryogenic conditions in and Figure 24 shows a photograph of the hose during the test in Le Trait (France). It is expected that the same technique can be extended to 24 internal diameter whilst keeping a similar design of hose composition. Figure 24: View of the Technip-Coflexip 16 cryogenic flexible hose in dynamic tests at Le Trait Technip-Coflexip manufacturing plant The length of the hose required in the various designs described is the range of 45 m (Figure 3) to 100 m (Figure 19), which is well within the capabilities of the Technip-Coflexip manufacturing plant (16 to 24 cryogenic hoses up to 100 m in length can be manufactured). Hoses connecting/disconnecting system developed by Amplitude-LNG During the design process of the various architectures of LNG transfer facility, for exposed area in particular, we have felt the necessity to create a new specific equipment at the interface between the midship manifold of the LNG carrier (as they exist today) and the mobile end of the flexible hose. This system which integrates all the necessary interface functionalities is a key point. It has to be designed harmoniously with the flexible hose end-fitting with also the view to reduce weights and sizes, which is essential for handling and dynamic performances. This is the aim of the association Amplitude-LNG Amri-KSB, Technip-Coflexip and Eurodim to propose to the industry the Amplitude-LNG Loading System ALLS a compliant loading pipe with a connecting system able to serve the widest variety of architectures for LNG transfer marine terminals for dedicated or non-dedicated (i.e. midship manifold) LNG carriers. Lanquetin, Lanteri-Minet, Dupont 25

27 The Amplitude-LNG name has been chosen to reflect the ability of the system to cope with large movements of the LNG carrier as well as it allows an ample choice for the gas Operators to select a site for their LNG transfer facilities. The connecting system has been developed with the following design philosophy: - Safety is priority. - Reliability is priority: avoid complexity and sophistication. - Respect of flexible hose integrity and behaviour predictability under all circumstances. - Blind connection and disconnection in dynamic conditions. - Safe and reliable emergency disconnection with very minimal spillage: no spill. - Minimal weight to maximize dynamic connection performances. - Outboard connection to avoid clashes (see Figure 25A). - Connection handling performed along the main acceleration axis (see Figure 25B) so that the mobile mass is simply hanging on the lifting cable (always clearly in traction even at highest sea states) which in final phase serves also as a guiding cable piloting in any circumstance the pin through the receiving funnel. Receiving funnel Handling /guiding cable Pin Figures 25A and 25B: Design philosophy of the connecting system The generic connecting system, is composed of: - A Quick Connect/Disconnect Coupler (QC/DC), to connect and disconnect it ( blind connection). - A Double Butterfly Valves & Emergency Release Coupler (DBV & ERC): to emergency disconnect it without LNG spillage. - Handling devices, to handle the extremity of the compliant loading pipe to the ship manifold. - Guiding and positioning devices, to guide and position the extremity before connection. DBV & ERC are mounted on the flexible hose side. During connection/disconnection procedures, the flexible hose internal atmosphere is isolated by closing the ERC valves. The valves are based on existing and proven technology cryogenic DANAIS butterfly valves from Amri-KSB. The kinematic allows to avoid any spillage as shown on Figure 26. Lanquetin, Lanteri-Minet, Dupont 26

28 Fully opened Intermediate position Fully closed Figure 26: Kinematic principle of the no spill Double Butterfly Valves & Emergency Release Coupler (Amri-KSB and Eurodim joint patent pending) The connecting system concept is shown on Figure 27 in case of a non-dedicated carrier. This figure shows the common link for all the solutions presented. Rotating quay Aerial Fluid Path SPM Conventional Buoy Mooring Traditional mooring The common link: Connecting system including: - No spill Double Butterfly Valves - Emergency Release Coupler - Quick Connect Disconnect Coupler - Handling devices Flexible pipe in catenary configuration Spool piece Non-dedicated LNG carrier Figure 27: ALLS for non-dedicated LNG carrier The connecting system concept for a dedicated carrier is shown on Figure 28 and can be used in tandem offloading for example. The difference between the two arrangements is that, in case of a dedicated LNG carrier, mechanical equipements requiring power can be installed on the ship side. Lanquetin, Lanteri-Minet, Dupont 27

29 Ship manifold Longitudinal guiding devices Transversal guiding devices Quick Connect Disconnect Coupler Handling cable (winch on the ship) No spill Double Butterfly Valves and Emergency Release Coupler Flexible hose end-fitting Figure 28: 3D view of the ALLS in case of dedicated LNG carrier (Amri-KSB and Eurodim patents pending) A prototype of ALLS, comprising a connecting system, the flexible hose end-fitting and a stiffener, will be designed, manufactured, tested and qualified beginning of year 2003 within a JIP. Participants are BP, ChevronTexaco, Eni Agip division, Gaz de France, Leif Höegh & Co and TotalFinaElf. The base case, which has been chosen by the JIP Participants, is to design the prototype for a tandem offloading and a for dedicated LNG carrier in severe environment. General data calculation results of relative motions between the ships and accelerations at connection point on the LNG carrier have been used to size the equipements, i.e.: - Validation by calculations of the hose configurations. - Mechanical characteristics of the stiffener. - Loads on couplers, handling, guiding and positioning devices. - Capture envelope of the guiding and positioning devices of the connecting system. Cryogenic aerial 24 swivel with capability of vapour return developed by Eurodim Another key element for these architectures is the LNG two-path coaxial swivel joint (internal path for liquid phase and outer path for vapor). Lanquetin, Lanteri-Minet, Dupont 28