By Willem de Ruyter* – Single Buoy Moorings Inc, Project

The Sanha LPG FPSO

By

Willem de Ruyter* – Single Buoy Moorings Inc, Project Manager Sean Pellegrino - ChevronTexaco, Project Manager

Hervé Cariou – Single Buoy Moorings Inc, Engineering Project Manager

* Presenting author

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1. Introduction: Project Information

A new era in the offshore industry will be ushered in with the start-up of the Sanha LPG FPSO. The Sanha LPG FPSO represents the first time that a purpose built LPG processing plant will be installed on a floating structure. The Sanha LPG FPSO is a key part of the Sanha Condensate Project. The Sanha Condensate Project’s objective is to eliminate routine gas flaring while collecting and injecting collected gas to increase oil and LPG production in Areas B and C of Block 0, offshore Cabinda, West Africa. The project will reduce routine flaring in Block 0 by more than 40 percent. The reduction in routine flaring will eliminate 2.2 million tons of carbon dioxide emissions per year.

Figure 1 : West Africa

The Sanha Field is located offshore Cabinda, Angola approximately 30 miles offshore from the onshore Cabinda Gulf Oil Company’s Malongo Terminal in Block 0. The Sanha Condensate Project will have a peak production of over 100,000 barrels of liquid per day (oil, condensate and LPG). ChevronTexaco’s Angolan affiliate, Cabinda Gulf Oil Company (Cabgoc) (39.2%) operates the block on behalf of its partners, including Sonangol (41%), Total (10%), and ENI (9.8%). Cabgoc and Sonasing (a joint venture between Sonangol and SBM) are to share in the operations of the Sanha LPG FPSO.

Figure 2 - Sanha Condensate Project Facilities Overview

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The 260-meter long Sanha LPG FPSO has the ability to process over 37,000 barrels of LPG per day into propane and butane products. The Sanha LPG FPSO receives the majority of the liquid LPG from the nearby Sanha Condensate Complex and a smaller amount of LPG from the F-GIP facility. The vessel refrigerates and stores 135,000 cubic meters of the propane and butane products in six specialty LPG tanks. Offloading of the propane and butane products is performed by side-by-side port or starboard operations or in a tandem arrangement. The Sanha LPG FPSO has accommodations to house a crew compliment of 60 persons. The Sanha LPG FPSO is a permanently single point moored vessel designed to remain anchored in the Sanha Field for more than 20 years without dry-docking. The Sanha LPG FPSO is the World’s largest in terms of LPG storage capacity and first New Build LPG FPSO. The Sanha LPG FPSO has some of the largest and first of its kind equipment and is truly a prototype. 2. Background In early 2000, a small team of Single Buoy Moorings Inc. (SBM) and ChevronTexaco personnel formed a joint team to develop the contractual and technical specifications for a commercial tender package for the engineering, design and fabrication of the Sanha LPG FPSO. The philosophy was that Sonasing (a joint partnership of SBM and Sonangol) would own the FPSO and lease the vessel to Cabgoc for an eight-year period and that the vessel would be jointly operated with personnel from both Cabgoc and Sonasing. In May 2002, a contract was executed between SBM and Cabgoc for the design, procurement, fabrication and transportation of the Sanha LPG FPSO. Concurrently, SBM executed a design, procurement and fabrication contract with IHI Marine United Inc. for the Sanha LPG FPSO hull and topsides. IHI Marine United Inc.’s responsibility included the delivery of the Sanha LPG FPSO with the exception of the single point mooring system and turret. Two major subcontractors of IHI Marine United Inc.’s were JGC for the engineering and construction of the depropanizer module and HKSE for the engineering and construction of the refrigeration and reliquefaction plants. In addition to the above contract, Cabgoc and SBM or one its affiliated companies have executed contracts for the offshore installation, hook-up and commissioning; bareboat charter and the operating service agreement relating to the Sanha LPG FPSO. Cabgoc and SBM formed an integrated ‘Company’ Project team for the monitoring of IHI Marine United Inc.’s and their subcontractor’s design and fabrication of the Sanha LPG FPSO. The first steel cutting for the Sanha LPG FPSO occurred in the IHI Marine United Kure, Japan Shipyard in November 2002 with keel laying in February 2003.

Figure 3 - Keel Laying Ceremony

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Engineering, fabrication and procurement activities were carried out all over the world for the Sanha LPG FPSO. The vessel launching from the Kure Shipyard dry dock occurred in November 2003.

Figure 4 - The World and the various locations

The vessel completed gas trials and sailed from Japan in November 2004. The vessel completed final drydocking in Singapore in December 2004 and has arrived in Angola in late February 2005. First LPG and hand-over to Operations is scheduled for April 2005. 3 Design Features

3.1 FPSO Overview

Figure 5 – The Sanha LPG FPSO

FPSO Main Particulars: Loa 262.8m Lpb 230.0m Bmld 49.0m Dmld 29.3m Tmld 13.2m

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Classification:

A1 Liquefied Petroleum Gas Floating Processing, Storage and Offloading System;

A1 Floating Offshore Installation – Depropanization, Refrigeration and Reliquefaction Facilities;

Ship Type 2G (–50oC, 0.45 kg/cm2 g, 650 kg/m3), DLA, SFA; ACCU, IGS, UWILD, PMS; DNV Notations: HELDK−SH, F-AMC

3.2 Hull Design and Cargo Containment system

The Sanha LPG FPSO features a purpose built, barge-shaped, double hull floater. Ballast tanks are provided in the double bottom and in the sides, thus providing a double protection of the cargo tanks.

Figure 6 – Typical support Figure 7 – Typical Hull/tank transverse section The Sanha LPG FPSO has six (6) insulated SPB (Self-standing Prismatic IMO Type B) tanks for storage of both propane and butane products, stored separately after fractionation. The six tanks provide a total storage capacity of 135,000 m3 at a design temperature of – 50 C and a design pressure of 0.45 barg. The SPB tanks, a proprietary IHI Marine United design, are made of low temperature carbon steel. The cargo tank supports are made of reinforced plywood.

Figure 8 – Cargo hold space prior to tank erection

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One paramount criterion for the hull design is the sea-keeping behaviour of the FPSO. The depropanizer column imposes very stringent motion limits to ensure the fractionation process delivers “on-spec” propane product. After detailed studies it was decided that the FPSO should not roll more than 5° and not pitch more than 1° up to the 10-year environmental conditions as predicted for the Sanha site. An extensive model test program in a basin confirmed the FPSO motions calculations. The FPSO is designed to stay on-station at the Sanha site for 20 years without drydocking. In order to achieve this goal, onerous design criteria are imposed on the hull and topsides structures:

• The Hull and Topsides has a fatigue life of 20 years, based on North Atlantic environmental conditions;

• The Hull and Topsides has a fatigue life of 30 years, based on the environmental conditions of Sanha site;

• Not only the hull but also the topsides are designed for the North Atlantic 20-year return conditions;

• The use of high tensile steel is restricted; • A high quality coating system is applied in the ballast tanks.

Detailed strength and fatigue analyses were carried out to confirm that those criteria were being met. Furthermore, the SPB technology is proven for its reliability, relying on detailed fatigue analyses and crack propagation analyses.

Figure 9 – Hull/Tank Fine Mesh Model

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3.3 Mooring & Fluid Transfer System

The FPSO is permanently moored to the seabed by an external turret mooring system that was designed and fabricated by SBM. The external turret mooring system is cantilevered from the bow and comprises both a rotating and a fixed part. The two parts are connected via a main ‘slewing’ bearing, which allows the turntable to freely weathervane around the anchoring system so that the FPSO can take up the position of least resistance to the prevailing weather at all times.

Figure 10 – Turret General Arrangement

The anchoring system consists of an array of nine (9) chain legs and nine (9) drag anchors. The drag anchors are off SBM standard “MAG” design and each anchor weighs 28 tonnes and is among the largest ever built by SBM. Two 6” flexible risers lift the two incoming LPG feeds from the Pipeline End Manifold (PLEM) to the turret. A 4” flexible riser is provided to supply Fuel Gas to the FPSO, to be burnt in the steam boilers. Emergency Shutdown valves are provided on the PLEM to isolate the pipeline in case of emergency. The fluid transfer system from the fixed to the rotating part of the turret consists of swivel stack of two identical toroïdal swivels for the LPG feeds and one in-line pipe swivel for the Fuel Gas line. An electric swivel transmits electrical power and control signals to the fixed part of the turret.

Figure 11 – Swivel stack General arrangement Figure 12 – LPG Toroidal Swivels

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3.4 Depropanizer Plant

The Depropanizer Plant is the heart of the FPSO. It is located slightly aft of the FPSO midship.

Figure 13 – Depropanizer Plant outline arrangement

The Depropanizer plant consists of the following main components:

• 1 x Inlet Surge Vessel, • 3 x Surge Vessel Pumps • 2 x 100% H2S Treatment Vessels • 2 x 100% Inlet Filters • 2 x Inlet/ Bottom Heat Exchangers • 1 x Inlet/ Overhead Heat Exchanger • 1 x Depropanizer Column (17barg/ 103°C) - (Mellapack Structured Packings) • 2 x 50% Butane Reboilers (steam heated - thermo-syphoon type) • 16 x Air-fin Condensers • 1 x Propane Accumulator • 2 x 100% Propane Reflux Pumps • 1 x Cold Vent & Blow-down Tower (77m tall, fitted with a Kaldair ® type tip).

Mixed LPG streams consisting of propane and butane arrive at the FPSO via two 6-inch pipelines from the Sanha Processing/Compression Platform in Area C and the Fox-GIP Platform in Area A. On board the FPSO, these streams are metered. The LPG streams are treated to remove trace levels of H2S in the H2S Removal Vessels. The combined streams are then filtered and fractionated in the Depropanizer. The bottoms butane stream coming off the Depropanizer is partially cooled in two Depropanizer Inlet /Bottoms Heat Exchangers. The butane is then cooled to storage temperature in the Butane Refrigeration Plant and then routed to the FPSO cargo tanks for storage. Propane coming off the overhead of the Depropanizer is condensed in the Depropanizer Condensers and then flow to the Depropanizer Accumulator. Part of the propane stream returns to the column as reflux, while the remainder is partially cooled in the Depropanizer Inlet/Overhead Product Heat Exchanger. The propane is then cooled to storage temperature in the Propane Refrigeration Plant and routed to the cargo tanks for storage.

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The FPSO processing capability is 37,370 bpd, at 22 barg / 18°C inlet conditions. In addition, the FPSO receives up to 14MMSCFD of Fuel Gas (methane), used as main fuel for the boilers. The fuel gas stream is conditioned on the topsides in a scrubber and a heater.

3.5 Refrigeration and Reliquefaction Plants

The propane refrigeration consists of a 2-stage cooling plant, using a closed loop of commercial propane as refrigerant. There are 3 cooling units (numbered C1~C3) in total, all using oil-flooded screw compressors. The propane stream is cooled in two units arranged in series (C1 + C2 or C2 +C3). The propane refrigeration plant also supplies refrigerant to a trim cooler, which is used when the depropanizer plant is operating at low turn-down rate.

Figure 14 – Typical Refrigeration Unit Skid

The propane refrigeration plant is installed in an enclosed deckhouse located on the topsides forward of the depropanizer plant, over the pipe racks. The deckhouse is split into a compressor room and a motor room. A gas-tight bulkhead separates the two subdivisions. The butane refrigeration consists of a single stage cooling plant, using also a closed loop of commercial propane as refrigerant. It consists only of 2 cooling units (C4~C5), using also Aerzener oil-flooded screw compressors. The butane stream is cooled in either of the two units. The butane refrigeration plant also supplies refrigerant to the reliquefaction plant. All five refrigeration units C1~C5 are of the same design. Each skid consumes around 2 MW of electrical power. The reliquefaction plant is designed to separately handle the boil-off gas from the propane and butane storage tanks. It is different from the design commonly applied on LPG tankers since it is of the cascade type, using refrigerant from the butane refrigeration plant. The propane reliquefaction plant consists of three units (numbered R1~R3). In normal operation, two units are required to re-liquefy the propane vapors. R3 unit acts as stand-by unit both for the propane and the butane reliquefaction. To achieve that dual function, the R3 compressor is fitted with a two-speed electric motor. The butane reliquefaction plant consists of a small direct type fresh water-cooled unit (R4). All four reliquefaction skids are using oil-free screw compressors.

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Figure 15 – Typical reliquefaction unit skid

The reliquefaction plant is also installed in an elevated deckhouse located aft of the depropanizer plant. It also houses the two butane refrigeration units. The building is of the same design as that of the propane refrigeration plant.

3.6 Marine Systems

The Sanha LPG FPSO includes both a forward and an aft machinery room. The equipment fitted in these two spaces supplies all of the utilities necessary for the accommodations and topsides operations. FPSO utilities that are provided include approximately thirty (30) auxiliary systems such as control air, utility air, inert gas, nitrogen, cooling water, fire water, potable water, sewage treatment, hydraulic oil, fuel oil, etc. In this space alone, there are over 60 pumps, 1,200 valves, and 10,000 spool pieces of piping. The key equipment installed in the forward machinery space includes three (3) dual fuel, “D”-type, 90 ton/hr. The boilers, the largest ever built of that type, provide superheated steam for power generation in three (3) 9MW steam turbines and saturated steam for the topsides process heating demand. Under all normal operating conditions, only two boilers shall be operating with the third boiler on warm standby. In addition to the key equipment above, a number of other auxiliary equipment are installed including items such as purifiers, condensers, distilling plants, sewage treatment plants, incinerators, etc. In the aft machinery space, a 4,000-HP tunnel thruster with variable pitch is installed. The function of this thruster is to increase the fractionation system uptime and throughput by minimizing vessel rolling and the associated negative impact this would have on production. Furthermore, it can also adjust the FPSO heading before and during cargo export operations. The aft machinery space also houses two diesel engine driven emergency fire and deluge pumps. 3.6.1 Power Generation and Distribution The power generation system consists of the following components:

• 3 x 9 MW Steam Turbine Generators – each generator is sized for 50% of the maximum electrical demand of the FPSO;

• 1 x 3 MW Essential Diesel Generator – the essential diesel generator is sized to run the reliquefaction plant in case of steam plant shutdown.

• 1 x 850 kW Emergency Generator. The layout of the power distribution system is as follows:

• Engine Room consumers are fed from switchboards/ MCC located in the Machinery Room Control Center (MRCC), located in the forward machinery space;

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• Deck & Topsides consumers are fed from the main switchboard/ MCC room located at main deck level of the accommodation.

• Critical consumers are fed via the UPS. The UPS and battery rooms are located on the top of the accommodation.

3.6.2 Control and Safeguarding

The FPSO Monitoring & Control System (M&CS) consists of two sub-systems, namely the Process Control System (PCS) and the Safety Shutdown System (SSS). The M&CS is a Distributed Control System. The M&CS processes and displays over 11,000 data points collected throughout the FPSO. Almost all FPSO systems can be controlled remotely from the M&CS. Man-machine interface stations included in the M&CS are installed in the FPSO Control Center (FCC) in the Machinery Room Control Center (MRCC) and in strategic rooms. The FPSO Control & Safeguarding philosophy was carefully established at the early stage of the project to ensure an optimum protection of personnel and of the asset, without hampering the operability of the installation. The FPSO Fire & Gas Detection System is stand-alone and interfaces with the SSS for safety actions and status monitoring. A selected amount of data is archived into a historian server, and can be used to produce cargo export reports. Additionally, the historian server is also connected to the FPSO computer network, thus providing the possibility to view any FPSO data point available within the M&CS.

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3.6.3 Offloading

The Sanha LPG FPSO has a much greater offloading flexibility than any other turret-moored FPSO. This outstanding flexibility includes:

• The capability of exporting cargo to LPG tankers moored either in tandem at the stern of the unit or in side-by-side (SBS), on both sides of the FPSO.

• The capability of accommodating all sizes of export tankers, from small pressurized coastal vessels of 2,000m3 capacity to fully refrigerated Very Large Gas Carriers (VLGC’s) of 85,000m3 capacity. The tandem mooring is even designed for future VLGC’s of 125,000m3 capacity.

• The capability of exporting to side-by-side moored refrigerated propane and butane export tankers; with vapor return from the export tankers (starboard side only) back to the FPSO.

The stern tandem offloading system consists of the following main components:

• A cryogenic floating hose assembly of 12” diameter, approximately 200m long, connected from one of the two the FPSO stern manifolds to the export tanker midship manifold;

• A mooring hawser that will connect the export tankers bow to a chain stopper located at the stern of the FPSO.

For SBS offloading, export tankers will be moored with multiples lines, some of them to quick release hooks (QRH) installed on the deck of the FPSO, the others to mooring winches suitably located on the main deck. Due to the variety of tankers likely to moor alongside, not less than 48 QRHs and 7 winches are provided, offering an infinite number of mooring combinations. For VLGCs, which will be of the same length as the FPSO, up to 16 mooring lines might be deployed at the same time.

The other main features of the SBS offloading system are as follows:

• Five (5) export manifolds on starboard side midship, respectively for refrigerated propane and butane, propane and butane vapour return and pressurized butane.

• Three (3) export manifolds on portside midship, respectively for refrigerated propane, refrigerated butane and pressurized butane.

• Two (2) 12” corrugated stainless hose strings for refrigerated products export.

• Two (2) 8” corrugated stainless hose strings for propane and butane vapour return.

• One (1) 6” rubber hose string for pressurized butane export.

• Two knuckle boom type hose-handling cranes on starboard side, used to hold the export hoses between the FPSO and the export tankers. Up to four hose strings might be deployed at the same time.

• One knuckle boom type hose handling crane on portside, for the same function.

3.7 Safety in Design

Various engineering safety studies were carried out at an early stage of the design to validate the main technical choices. The most important ones included:

• A Fire & Explosion Analysis (FEA), aiming at simulating various Fire an Explosion scenarios and their consequences on the asset. Some modifications of the topsides layout were made as a result of that study, in order to mitigate the consequences of explosions overpressure.

• A Smoke & Gas Dispersion Analysis (SGDA) that confirmed that gas or smoke clouds resulting respectively from accidental gas leaks and fires would disperse into the atmosphere without any risk escalation.

• An Emergency Systems Survivability Analysis (ESSA) that evaluated qualitatively the robustness of all safety systems.

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• An Emergency Escape & Rescue Analysis that studied qualitatively means of egress and rescue.

• Hazard & Operability Studies (HAZOP) and Hazard Identification Studies (HAZID) were conducted during the design phase. All essential FPSO systems were extensively analysed by such HAZID and HAZOP Techniques.

In addition, a pro-active safety behavior was adopted during design both by the designer and the approval parties to detect and correct unsafe design features at the drawing board level. Special attention was paid to avoiding tripping hazards, designing safe ladders, platforms, staircases etc.

4. Construction, Schedule and Present Status

4.1 Contracting.

As explained before, Cabgoc (ChevronTexaco) awarded a contract to SBM. for the engineering, procurement, construction and commissioning of the LPG FPSO, for the offshore hook-up and commissioning (incl. the sea-lines), bare boat charter and shared operation. SBM contracted the design, procurement, construction and commissioning to IHI MU, Kure shipyard in Japan, except for the turret mooring system, which was designed and built directly by SBM Whilst contracting an FPSO can be and has been made in many different ways, the shipyard scope was in this case particularly large. It included design development based on plans prepared by ChevronTexaco and SBM in the pre-contract phase, procurement of FPSO equipment and materials, including the refrigeration and re-liquefaction machinery, which was subcontracted by IHI to Hamworthy KSE and the de-propaniser modules, which were subcontracted by IHI to Japan Gas Corporation (JGC). In addition, IHI covered the interface management related to these items and later the commissioning of the FPSO in Japan.

In this contracting strategy, one of the drivers has been an effort to reduce a potential costs increase coming from interfaces related to the supply, installation and commissioning of the FPSO machinery and equipment for hull and topsides.

4.2 Design and Construction

The detailed design at IHI, with the support from both ChevronTexaco and SBM Inc resulted in a high-quality, but complex FPSO. The required hull fatigue life needed much analysis and inspection of structural details. In addition, careful selection of the material grades was required in view of stresses and service at low temperatures. Another area of particular interest was the design of the M&CS, which eventually became most complex with the number of I/O’s of the control system growing from 3,500 to 6,500 hard-wired I/O’s (and 4,500 soft I/O’s).

The lightweight of the FPSO is approximately 48,000 tons.

The construction of the hull was not particularly difficult as the hull is basically similar to that of an LPG carrier, although at a larger scale. No major problems were encountered. The refrigeration and re-liquefaction plants were built in Norway shipped in modules to Japan and were installed on to the hull before launching of the hull. The accommodation block was built as one unit of 3,000 tons and lifted onto the hull soon after hull launching.

Topsides modules weight is also approx. 3,000 tons, the main item being the de-propaniser column. Whilst the modules were built at another yard in Kure, the de-propaniser column was built in Korea. The topsides modules were also installed onto the deck of the FPSO hull soon after launching the hull.

Special attention was paid to inspection of highly stressed and fatigue-sensitive details of the hull and topsides structure. Classification of the FPSO was done by American Bureau of Shipping.

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Figure 16 – Launching of Hull

Figure 17 – Lifting the Accommodations block

Figure 18 – Lifting the Surge Vessel into Place

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4.3 Quality

Quality standards for FPSO’s are much higher than generally applied in shipbuilding. The reasons are that FPSO’s are always to stay on location during it’s entire operational life, that repairs offshore are very expensive and difficult to manage and that high uptime is required in view of production continuity and the high investment. The hull and cargo systems were built to marine standards, whereas the de-propaniser modules were built to the offshore standards as is usual in the FPSO industry. The Sanha construction did achieve a high level of quality of workmanship of construction and painting, with much attention to details.

A large amount of inspection was carried out. For example, the SPB-type cargo tanks, probably the largest made in this type, required 100 % X-ray examination of the weldings.

4.4 Commissioning

Commissioning as practiced in the FPSO industry is close to the practices as used in the offshore platform industry. The FPSO practice is very methodical in that commissioning is done in three stages, i.e. Mechanical Completion (A-scope), Pre-commissioning (B-scope) and Commissioning (C-scope) in succession and by system. In addition, each stage is fully documented. This approach, when well used, ensures that accidents or damage to equipment are eliminated and that documented proof is obtained that systems in their entirety operate as required.

Whilst shipyard-commissioning practices are generally different in approach, the shipyard did, with much assistance of the SBM/ChevronTexaco site team, apply the FPSO industry practice successfully.

4.5 Project Management

Japan being an expensive place in the world, it was soon decided to minimize the number of staff to be relocated to the shipyard. An efficient way of doing so was the combination of the SBM and ChevronTexaco staff into a single team, thereby avoiding doubling the functions. The major advantage of this approach, however, appeared to be that the combination of the different skills and experiences of both Companies resulted in a highly competent team, whilst the contract lines of communication could remain in force at the same time.

The team consisted of a total of approx. 30 persons during design and construction. The team also already included certain key staff of the future operators. Towards the commissioning phase, more operators were relocated to the shipyard so that they could participate with the commissioning process and be trained with operation of the systems at the same time.

4.6 Schedule

The overall contract duration was approx. 30 months. The contract was formalised in May, 2002 and was based on achieving Notice of Readiness in January, 2005. A very rough breakdown of this period was as follows: Plan actual

Detailed design, procurement 5 m 5 m Steel delivery, block fabrication 5 m 5 m Hull erection in drydock 5 m 6 m Fitting out alongside 5 m 7 m Shipyard commissioning 4 m 4 m Tow to Angola 3 m ongoing HUC 2 m Total 29 m

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Steel cutting in Kure started in November, 2002, keel laying in April, 2003 and launching of the hull followed in November, 2003. The hull erection took one month longer than planned and was mainly caused by design changes coming from the plan approval process.

After launching of the hull in November, 2003, the installation of the accommodation block, process vent and de-propaniser modules was completed by the end of December, 2003. Then the integration activities, fitting out and mechanical completion followed. This last period took 2 months longer than planned, mainly caused by the complexity of the unit.

Therefore, commissioning could only start in July, 2004 in earnest. Completion was achieved by the early days of November 2004 instead of the planned date of early August 2004. Still a remarkable performance by the shipyard, given the complexity and size of the LPG FPSO.

One other special activity was that a final dry-docking for painting was required at the end of the gas trials and before tow-out of the FPSO to Angola. The reason was to have the paint system in optimum condition before the start of her 20 year operational life without dry-docking since the vessel was launched a year before her completion in Japan. This docking was initially planned to take place in Japan, but was later moved to take place in Singapore.

After this final docking and painting, the tow continued to Angola. The anchoring system had already been installed back in 2003, so HUC was started in March 2005 and is currently ongoing. Notice of Readiness is expected to take place by mid-April 2005, which is 3 months later than planned.

Figure 19 – Topsides deck overview

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5 Conclusions In concluding this paper, a few items of interest are worth mentioning: An FPSO has always been and remains a challenge to manage, design and build. Despite many challenges and a certain underestimation of what is involved, the shipyard performed remarkably well, in particular since the Sanha LPG FPSO can be considered a prototype.

The selected policy of creating an integrated site team between SBM and ChevronTexaco worked very well. It is believed that the best possible results were obtained in a most cost-effective manner. High quality levels are essential in the FPSO industry in view of the required up-time, no drydocking during her life and cost for repairs offshore. Such quality requirements are generally higher than is found in the marine industry, in particular when offshore standards apply. Commissioning required significant efforts by the Owner’s site team to effect proper and systematic commissioning. The same was valid for interface management.

The LPG FPSO that was materialised under this contract is one of high standard. Whilst the concept is probably a first, only equipment of proven technology has been used, albeit at a much larger scale than applied before.

Finally, in its execution this project has been both challenging and very pleasant. Cooperation between shipyard and a very international site team has always been excellent and has definitely contributed to the success. It has been very rewarding to see that our approach to managing the project was good.

Figures 20 and 21 – Naming Ceremony

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Figures 22, 23 and 24 – Sanha LPG FPSO Departure on Tow

Sanha LPG FPSO

Presentation to GAS TECH

2005

Sanha Condensate Project Facilities

Drilling/Production

Sanha LPG FPSO Schedule

• Initial Preliminary Engineering Jan. 1997

• Contract Execution May 2002

• Fabrication Start – Shipyard Nov 2002

• Keel Laying (Drydock) Feb 2003

• Launching (from Drydock) Nov 2003

• Gas Trials Nov 2004

• Final Dry Docking (Singapore) Dec 2004

• Compressor Reinstallation (Cape Town) Feb 6-21, 2005

• FPSO Arrival in Cabinda Mar 6, 2005

• Notice of Readiness (first LPG) Apr 12 – 14, 2005

• 72 hr. Run Test Apr 21 – 26, 2005

• Turn over/System Acceptance Apr 24 -25, 2005

DEPROPANIZER. Fractionates

LPG into propane and butane (ratio

approx 65/35). Max rate 37,370

bpd. Top of depropanizer column approx. 60m above the main deck.

HULL.

Double hull, reinforced for side for side-

by-side mooring of LPG tankers up to

85,000 m3. Port side primarily used for smaller pressurized carriers (2000m3+)

CARGO TANKS. (6ea x23,050m3 (135,000 m3

total storage). Two tank halves, common vapor

space. Design temp -50oC, dens 0.65

kg/m3.Type B, self supporting tanks with

polyurethane foam panels. Butane/Propane

cooled in refrigeration plant to enable storing and export at near ambient pressure.

Deep-well cargo pump ( 550 m3/hr) ea tank

half. Emergency/recycle pump (110 m3/hr) also provided.

REFRIGERATION UNIT (PROPANE).

Largest refrigeration package ever built.

Cools down propane from ambient to approx -37oC.

REFRIGERATION (BUTANE) AND RELIQUEFACTION UNIT

Cools Butane cooled down to

approx -7oC to permit storage at atmospheric pressure..

The unit also houses

compressors that reliquify LPG

vapors from cargo tanks and shuttle tank returns.

Manifold Arrangement.

2 x 12" hoses for Propane

2 x 8" for vapor return

1 x 6" hose for Butane

Max discharge rate 34,000 bph for Propane and Butane simultaneously.

Pressurized Butane 3,750 bph.

MOORING EQUIPMENT.

Quick Release Hooks are installed to

enable efficient/ safe mooring and

unmooring operation. Can be remotely released in an emergency.

Mooring Winches with lightweight

synthetic mooring lines strong as steel,

but 1/7th of the weight (same material as in bullet-proof vests).

CRANES (8). Equipped with

knuckle boom, providing low

load movement, high

maneuverability, and ultimate

safety. Layout ensures ease of maintainability.

THRUSTER.

Largest tunnel thruster ever

built installed at stern.

Enables FPSO to maintain

heading during export

operations, if sea condition

unfavourable for ultimate

safety.

VENT TOWER.

Tower height 77m above deck.

Situated on Aft Mooring Deck to allow

vapors, in the event of a release, to be safely dispersed clear of the vessel..

ACCOMMODATION. Designed to

accommodate 60 persons. Complete with

medic area, gym, swimming pool, sauna, a 13th

floor elevator and other facilities.

TURRET. Enables FPSO to weathervane 360o. To

be moored with 9 anchors, each chain approx.

550m long. The anchors used are the largest drag

anchors built. Two 6” flexible risers carry mixed

LPG at ambient temp and one 4” flexible riser Fuel Gas for FPSO’s steam plant.

HELIDECK. Designed for

a Bell 212 with low

turbulence, wide obstruction-free approach.

FENDERS. 5 ea Yokohama

3.3mx6.5m + 1 ea susp foam filled).

Launched by purpose built davits,

designed to absorb shock loading of fenders bouncing in 3m seas.

TANDEM OPERATION.

Tankers up to 135,000m3 can be moored in

tandem to Smit Bracket at stern. A 60m

hawser (BL 460t) used and 12” floating hose.

LIFEBOAT.

Fully enclosed motor lifeboats

(60P) on each side. Remotely released, air supply provided.

Propane Room. Ref. Compressors.

Butane Room. Ref & Reliq Compressors

Sanha External TurretSanha External Turret

GENERAL1/7Name : SANHA LPG FPSO

Owner : SONASING SANHA LTD

Builder's hull number : 1063

Builder : IHI Marine United Inc. Kure Ship yard

IMO number : 9277462

Nationality : BAHAMA

Port of registry : NASSAU

Date of keel laid : FEB. 25, 2003

Date of launching : NOV. 21, 2003

Date of delivery : NOV. 4, 2004

Classification : AMERICAN BUREAU OF SHIPPING

Notation : + A1 Liquefied Petroleum Gas Floating Processing, Storage and Offloading System+ A1 Floating Offshore Installation –Depropanization, Refrigeration, and ReliquefactionFacilities; Ship Type 2G (-50deg C, 0.45 Kg/cm2, 650 Kg/m3), DLA, SFA+ACCU (minus propulsion plant), UWILD, PMS

GENERAL2/7

Length registered 220.80 M

Length overall (Loa) 262.65 M

Length between perpendicular (Lbp) 230.00 M

Breadth (Mould) 49.00 M

Depth (Mould) 29.30 M

Design draft (Mould) 13.20 M

Scantling draft (Mould) 13.20 M

Assigned summer draft (Ext.) 13.224 M

Deadweight Approx. 93,000 T

Gross tonnage Approx. 113,000 T

Net tonnage

Complement

Approx. 33,900

60 Person

T

GENERAL3/7Production, Max. in total

From SCC, Max

Pressure, Normal

Pressure, Max. operating

Temp., Normal

Temp., Design Max.

From FGIP, Max

Pressure, Normal

Pressure, Max. operating

Temp., Normal

Temp., Design Max.

Propane : Butane

:

:

:

:

:

:

:

:

:

:

:

:

37,370 Barrels/Day (5,941 m3/Day)


320 psig

700 psig

65 deg F

100 deg F


310 psig

700 psig

65 deg F

100 deg F

0.65 : 0.35

Offloading Rate

Side-by-Side (Refrigerated), Total

Pressure, Normal

Propane

Temperature, Minimum

Butane


Side-by-Side (Pressurized)

Pressure, Normal

Butane

Tandem, Total

Pressure, Normal

Propane


Butane


:

:

:

:

:

:

:

:

:

:

:

:

:

:

:

34,000 Barrels/Hour (5,405 m3/Hour)

45 psig


-58 deg F


-5 deg F

3,750 Barrels/Hour ( 596 m3/Hour)

116 psig

3,750 Barrels/Hour ( 596 m3/Hour)


175 psig


-58 deg F


-5 deg F

GENERAL4/7

GENERAL5/7• Cargo Tank

– Type

– Tank #

– 1 atm, -50 Deg. C (98%)

• Ballast Tanks (100%)

• FWT (100%) (fresh water)

• DWT (100%) (drinking water)

• FOT (100%) (fuel oil)

• Manifold

– Starboard

– Port

– Tandem

• SPB, IMO-type B

• 6

• 135,000 m3 (excl. dome top)

• 59,583 m3

• 459 m3 (2887 bbls)

• 413 m3 (2597 bbls)

• 5, 104 m3 (32,104 bbls)

• 1 – Propane, 1 –Butane, 2 –Vapor Return, 1 Pressurized Butane lines

• 1 – Propane, 1 –Butane, 1 Pressurized Butane lines

• 2 – Propane or Butane

GENERAL6/7• Cargo pump

• Emergency Cargo Pump

• Butane Booster Pump

• LPG Recycle Booster Pump

• Inert Gas Generator

• N2 Generator

• Ballast Pump

• Central Cooling Sea Water Pump

• Cooling Fresh Water Pump

• Fire water Pump

• Fire and GS Pump

• Deluge Pump

• Emergency Fire Pump

• Utility Air Compressor

• Control Air Compressor

• Thruster

• 12 – 550 m3/h x 120 m

• 6-110 m3/h x 120 m

• 2 -550 m3/h x 75 m

• 2 – 110 m3/h x 75 m

• 1 – 5400 Nm3/h

• 2 – 100 Nm3/h

• 2 -1800 m3/h x 35 m

• 2- 2100 m3/h x 14 m

• 3 – 1850 m3/h x 27 m

• 1 – 170 m3/h x 105 m

• 1 – 170 m3/h x 105 m

• 2 – 1000 m3/h x 105 m

• 2- 1200 m3/h x 105 m

• 2 –Nm3/h x 1.0 MPa

• 2 – Nm3/h x 1.0 MPa

• 1 – 3000 Kw

MACHINERY

GENERAL 7/71. DEPROPANIZER

2- H2S Removal System (100 %)

2- LPG Inlet Filters (100 %)

1- LPG Surge Vessel (100 %) & 3- Surge Vessel Pumps ( 50 %)

Depropanizer Plant :

1- Depropanizer Column (100 %)

8- Depropanizer Condenser (air‐‐‐‐cooled)

1- Depropanizer Accumulator (100 %) & 2- Reflux Pumps (100 %)

2- Depropanizer Reboilers (50 %)

Total Weight : 2,208 T (dry) / 2,448 T (op.)

Depropanizer column : abt 60 m tall, 450 T (dry) / 560 T (op.)

2. REFRIGERATION UNIT

3- Propane (50%)

2- Butane (100%)

3. RELIUEFACTION UNIT

2- Propane (100%)

1- Propane & Butane (100%)

1- Butane (100%)

DEPROPANIZER PLANT

Sanha LPG FPSO Sanha LPG FPSO

TopsidesTopsides

Process Flow DiagramProcess Flow Diagram

Butane to Refrigeration

H2S Scrubber Vessels

REFRIGERATION/RELIQUEFACTION PLANT

• Butane & Propane Refrigeration Plant (

Aerzener Wet Screw Compressors)

• Butane Re-liquefaction Plant (Howden

Oil-free Screw Compressors)

• Propane Re-liquefaction Plant (Howden

Oil-free Screw Compressors with

Cascade System)

Refrigeration and ReliquefactionPlant

Refrigeration and Refrigeration and ReliquefactionReliquefaction

PlantPlant

Typical Refrigeration Unit – 1 of 5

Typical ReliquefactionUnit – 1 of 4

Refrigeration & Refrigeration & ReliquefactionReliquefaction

PlantsPlants

Propane Refrigeration Plant C1Propane Refrigeration Plant C1

Propane Propane ReliquefactionReliquefaction Plant R1Plant R1

LPG STORAGE (TANKS) & OFFLOADING

The vessel has (6) low temperature

cargo tanks. Each cargo tank is

designed to handle either butane or propane.

The vessel is able to offload to a shuttle

tanker either on the Port or Starboard side. The Starboard side is preferred

for offloading. The vessel has future

capabilities to offload in tandem to accommodate larger shuttle vessels.

Propane and Butane have the property of becoming liquid at atmospheric pressure when refrigerated and reverting to gases when the temperature is increased.

The Sanha LPG FPSO utilizes this property and stores these products in the liquid state. Otherwise, it would take a vessel roughly 250 times as big to store the same volume if in a gas phase.

Thruster

� Side-by-side Offloading to all

sizes of LPG tankers, from 2,000

m3 to 85,000 m3 capacity

• Port Side

– Pressurized Butane.

– Refrigerated Propane &

Butane simultaneously.

• Starboard Side

– Pressurized liquid

Butane.

– Refrigerated Propane &

Butane simultaneously

and vapor recovery.

� Provisions for Tandem Offloading

to tankers from 30,000 m3 to

125,000 m3 capacity (future).

Offloading EquipmentOffloading Equipment

Cargo Containment SystemCargo Containment System

View on cargo tank #2 from FPSO centerlineView on cargo tank #2 from FPSO centerline

Cargo Containment SystemCargo Containment System

Cargo Tank Supports :Cargo Tank Supports :

View of Bottom Supports in Cargo Hold #3

Detail of tank support

IHI SPB

Self-supporting

Prismatic Tank

IMO Type-B

FWD MACHINERY SPACE

3RD MACHINERY DECK

Steam generation: Boilers No. 1,2 and 3.

• Three Boilers made by Mitsubishi. Largest ever built of this type.

• The boilers are built to operate on dual fuel (Gas or MGO)

• Capacity is 90 ton/h each

• Saturated steam 25 t/h, 23 bar

• Superheated steam 65 t/h, 22 bar, 270 deg C (520 deg F)

• Three Boiler Operation

• Under all normal operating only two boilers shall be operating with the third boiler on warm standby

3RD MACHINERY DECK

• Three Steam Turbine Generators made by Shinko/Nishishiba,

• Total power is 3 x 9000 kW = 27 000 kW or 27.0 Mega watt.

4th MACHINERY DECK

• Main Steam Turbine Condensor

• Control Air Compressors No. 1 & 2

• Utility air Compressors No. 1 & 2

Feedback Items of Interest

• Contracting

• Hull Fabrication

• Gas Trials

• Commissioning

• Site Team Organisation

• Safety

• Final Drydocking

• Tow to Angola

Singapore

Nov. 24 – Dec. 23, 2004

Final Dry Docking

Sanha FPSO Tow RouteSanha Field

Cabinda

Cape Town

Feb. 6- 21, 2005

Japan

Nov. 4, 2004

Mar. 3- 5, 2005

By Willem de Ruyter* – Single Buoy Moorings Inc, Project

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