girassol-VA

A STEPPING STONE FOR THE INDUSTRY

unconsolidated, but hydrocarbon-rich sands.The well was tested at 12,500 barrels per dayof 32° API oil. Subsequent appraisal wells,GIR-2A and GIR-2B, drilled by the semi-submersible drilling rig “Jim Cunningham”,proved very significant reserves of oil in place

3

INTRODUCTION

In December 1992, a consortium of interna-tional oil companies, led by Elf Aquitaine

(now Total) of France, acquired the rights toexplore a large license area of offshore acreage,designated Block 17, in waters off the WestAfrican state of Angola.Even before the first seismic surveys were conducted and before a drilling unit put itsmarine riser in the water to begin the initialexploration well, Elf Aquitaine knew that ifsignificant quantities of hydrocarbons werefound at this location, any development wouldpresent challenges that the offshore oil and gasindustry had not been confronted with before.It has been the meeting of these challenges– technical, environmental and commercial –which make the development of the Girassolfield worthy of note and a project that will bea benchmark for others in the future.

In the early part of 1996, following oneunsuccessful drilling attempt, the explorationwell GIR-1 was spudded by the drillship“Neddrill 3” in 1,300 meters of water. Drilledto a depth of 2,500 meters, the well encoun-tered a classic deepwater shallow reservoir with

LuandaLuanda

NAMIBIA BOTSWANA

ZAMBIA

DEMOCRATIC REPUBLICOF CONGO

CONGO

GABON

Block 17

ANGOLAANGOLA

Cabinda

SaurimoSaurimo

HuamboHuambo

Lubango

Lobito

MalanjeMalanje

Namibe

Cabinda

SoyoSoyo

Saurimo

Huambo

Lubango

Lobito

Malanje

Namibe

Atlantic

Ocean

Congo

250 km

200 miles

AtlanticOcean

IndianOcean

ANGOLA

AFRICAAFRICA

400 m

1 600 m

Girassol

BLOCK 17

LIRIO

CRAVO

ROSA

JASMIM DALIA

VIOLETA

ORQUIDEA

ANTURIO

TULIPA

CAMELIA10 km

6,21 miles

800 m

1 300 m

Girassol is the firstdeposit on Block 17,in offshore Angola,to go into production.Located 200 km north-west of Luanda, at awater depth of 1,400 m, the depositcovers an area 14 km by 10 km.

4 GIRASSOL – A STEPPING STONE FOR THE INDUSTRY

INTRODUCTION

and set in motion what would be the firstmajor deepwater project in West Africa and the biggest development employing a Floating Production Storage and Offloading(FPSO) vessel and subsea wells anywhere inthe world.The challenges confronted by Total, though,in the development of the Girassol field weregreater than simply the technicalproblems presented by a deepwa-ter field with a reservoir with alarge areal extent.Total was facedwith working in an offshore sec-tor with little support infrastruc-ture and with managing fourlarge fabrication and supply con-tracts with suppliers spread around the globe.Yet it is the technical challenges that make this development stand out.The water is deep(1,400 meters) and cold, presenting significantflow assurance problems that had to be over-come with a number of technical innova-tions that were “firsts” in the industry.The un-consolidated reservoir is expected to produceenough sand to make this an issue to be over-come by the completion specialists. Thereservoir chemistry is such that new measureshad to be taken to treat the injection waternecessary to support the production of up to40,000 barrels per day per well.While not the deepest seabed conditions inthe world, the field employed a new genera-tion of subsea production hardware includingthe deepest oil production manifolds in theindustry. And the task of bringing the crudeoil to the surface at a temperature to preventthe formation of hydrates, required the fabri-cation of specially insulated flowlines and thefirst deployment of a type of deepwater risersystem that will be copied again and again inupcoming projects.

The production vessel is one of the largest ofits type in the world and its fabricationrequired the joint shipyard and offshore fabri-cation skills of one of the major shipbuildingcompanies in the world with project manage-ment provided by a consortium of interna-tional contracting companies.

300 meters long, 60 meters across the beam,30 meters draught, the FPSO is one of the largest vessels of its type in the world.

The export system, often a part of an offshoreproduction development that can appearmundane, took on a significance equal to manyof the other innovations in this project. Itincluded another industry first in the form of midwater transfer lines to the largest exportbuoy ever built.From the reservoir to the export system,Girassol

has presented a series of challengesto the development team that hadto be met and overcome in orderto bring the large reserves in thefield to the world energy market.No step along the way was easy.Each one had to be measured andreflected upon.

In December 2001, less than six years fromdiscovery,Total brought the Girassol field intoproduction and within a month it was produ-cing in excess of 100,000 barrels per day. Sixweeks later, plateau production of 200,000 bar-rels per day was reached.This has been a world-class achievement.

Less than 6 yearsfrom discoveryTotal brought

the Girassol field into production.

5

A FEW SUPPLIERS OF THE PROJECT

COUNTRY COMPANY SUPPLYANGOLA Sonamet Riser tower fabricationANGOLA Petromar Bundle fabricationBRAZIL Polyester mooring linesDUBAI Mc Dermott Module support frame fabricationENGLAND Murray Structural beamsFRANCE Techlam Export line flexjointsFRANCE Kvaerner Heurtey Process vesselsFRANCE Alto Mar Girassol Flowlines, risers and umbilicals: design, manufacture and installation

(Joint Venture Stolt Offshore and Bouygues Offshore)

FRANCE Mar Profundo Girassol FPSO: design, build and installation(Joint Venture Stolt Offshore and Bouygues Offshore)

GERMANY Dikema BV Structural platesITALY NuovoPignone TurbogeneratorsITALY NuovoPignone TurbocompressorsKOREA Hyundai Heavy Industries FPSO hullKOREA Hyundai Heavy Industries Topsides constructionNORWAY FMC Kongsberg Subsea Production SystemNORWAY Frank Mohn AS Crude pumpsNORWAY Frank Mohn AS Fire water pumpsSCOTLAND Balmoral Insulation foamSCOTLAND Oceaneering multiflex UmbilicalsSWEDEN Emtunga Electrical and instrumentation building–Passive Fire ProtectionUSA US filters Water injection treatment–Sulfate Removal UnitsUSA Nu – Chem, Inc. Passive Fire Protection

...AND MANY MORE...

7

The Girassol project is a deepwater develop-ment in 1,400 meters (4,600 feet) water

depth, located 150 kilometers (93 miles) offthe coast of Angola in the license area of Block 17.As a result of the technical challengespresented by the environmental conditions atthis location, a number of industry “firsts”havebeen required to achieve the target of produc-ing crude oil here. The reservoir is of a tur-bidite nature with an estimated 1,55 billionbarrels of 32° API crude oil in place. Prior tothe start-up of production, the estimated reco-verable reserves were 725 million barrels.

The development, the first of this scale in WestAfrica, is based on a barge-shaped Floating Pro-duction,Storage and Offloading (FPSO) vesseland a subsea production system.The export ofprocessed crude oil is via two rigid midwaterpipelines, an industry first, to a CAtenary LegMooring (CALM) buoy.

PROJECTDESCRIPTION

Full field development

� FPSO

� Export system

� Risers

� Manifold

� Xmas tree

The Girassolreservoir layout.

The Girassol reservoir is madeup of unconsolidated sands andthe well completions have beenequipped with a number of dif-ferent sand control devices toprevent damage to productiontubing and other equipmentbeyond the wellbore. Sand detection monitorshave been installed on each subsea xmas tree.Due to concerns about other flow assuranceissues, such as hydrate formation and waxdeposition, the production fluids must be keptabove 40°C (104°F) for arrival at the FPSO.As a result, the wellstream is fully insulated fromthe subsea xmas trees on the seabed all the wayto the FPSO’s processing system.

The deepwater location required a number ofinstallation scenarios for the various pieces ofseabed hardware and different connection tech-niques for the range of requirements, such as

�

�

�

��

GIRASSOL – A STEPPING STONE FOR THE INDUSTRY

PROJECT DESCRIPTION

8

well jumpers between the subsea xmas trees andthe production manifolds, the manifolds andflowline bundles, the bundles and the riser tow-ers.The production wells are linked to seabedmanifolds, the deepest oil production mani-folds installed anywhere in the world, whichare arranged in a “daisy chain” configuration.The wellstream is then transported throughflowline bundles to a series of riser towers,another industry “first” to be deployed on thisproject. Flexible jumpers link the top of thetowers to the FPSO.Water injection wells pro-vide pressure support for the production wellswhich are expected to produce at a rate of upto 40,000 barrels per day.The water injectionwells are supplied by a series of flowlines.

The philosophy of Total on Girassol has beento reduce its impact on the environment to aminimum.As a part of this effort, a non-flaringpolicy has been adopted.Associated gas is usedfor gas lift and injected for pressure mainte-nance in the reservoir. In the future, gas maybe exported to shore to provide feedstock fora proposed Liquefied Natural Gas (LNG) plant.

The development is in two phases. The firstphase includes eight production wells, twowater injectors and one gas injector.Phase two

is ongoing and will be completed in the mid-dle of 2003.The production system will even-tually consist of 23 subsea completed wellslinked to 11 seabed manifolds.This system, anadvance on the HOST 2500 concept,has beenqualified by its manufacturer,FMC KongsbergSubsea, for applications to 1,500 meters ofwater.This is the first use of this equipment.

I n order to ensure a high reliability and avail-ability, a qualification program was under-taken on 40 different items of hardware.Therewas also extensive verification testing includ-ing integration testing of subsea xmas tree systems and shallow water testing to demon-strate interface compatibility.

Module support frame pending subsea installation.

Production wells are linked to seabed manifolds and arranged in a “daisy chain” configuration.

9

The production system is controlled by anelectro-hydraulic multiplexed control system.Each subsea xmas tree has its own subsea con-trol module which is fully retrievable. The system provides data from a range of sensors – down each well, on each tree and from eachmanifold. It will also be able to communicatewith “intelligent” completion systems whichmay be installed on some wells in Phase two.It can also interface with theSubsea Acoustic Monitoring Sys-tem (SAMS) which is used torecord data from downhole gaugesprior to hookup with the FPSO.The link with the subsea controlmodules is by a network of 54 ki-lometers of seabed umbilicals.Eachproduction umbilical has four hydraulic lines – two high pressure and two low pressure – plussix chemical injection lines to provide a scale and corrosion inhibitor to each well and four electrical cables for power and communications.The umbilicals which link the water injectionwells are simpler, with the same four hydrauliclines and electrical cables plus a single 1-inchservice line.All of the tubes within the umbil-icals are made of super duplex steel.

The well fluids travel through 11 flowlinebundles,of 27 kilometers in total length, to the

base of the riser towers. Each bundle is basedon a 30-inch carrier pipe which has two 8-inchproduction flowlines and one 2-inch serviceline.These lines are encased, inside the carrierpipe, in a syntactic buoyancy foam speciallydeveloped for the flow assurance requirementsof this project.The water injection system is based on four12-inch flowlines with in-line tees. Each tee is

connected to one injection well.The interface between the seabedflowline system and the FPSO isa system of riser towers, the firstof their type ever used in such adevelopment.The system is com-prised of three vertical “bundles”of pipes.At the core of each riser

is a 22-inch pipe around which are four 8-inch production lines with four 3-inch gaslift lines plus two 8-inch injection lines andtwo 2-inch service lines. All of these lines areencased in the same syntactic buoyancy foamas used in the flowline bundles. At the top ofeach riser tower is a complex of flexible jumpers(for production and water injection) and bun-dles of super-duplex pipes for the service andgas lift lines which link up with the FPSO.The FPSO is believed to be the biggest in theworld in which a loading buoy is used to exportthe processed crude oil.The unit is 300 meters

The first risertowers of

their type everused in such

a development.

The system of riser towers is comprised of three vertical “bundles” of pipes (1,250 m high).

(985 feet) long and 60 meters (197 feet) acrossthe beam and 31 meters (101 feet) draught.The hull has the capacity to store two millionbarrels of processed crude.The total displace-ment of the FPSO is 400,000 tons.

S itting on top of this hull is a 25,000-ton topside processing system which can handle300,000 barrels per day of total liquids.The oil processing train can accommodate 200,000 barrels per day of crude. The water

injection system provides390,000 barrels per dayof water for injection at150 bar. Associated withthe water injection sys-

tem is a sulfate removal module – the biggestof its type anywhere in the world – whichtreats the seawater to avoid scaling in the pro-duction tubing.The gas handling system pro-vides 8 million cubic meters per day for rein-jection at 285 bar into two specially drilledwells. The living quarters on the productionvessel provide accommodation for an opera-tional crew of 140.

The processed crude is exported by two 16-inchmidwater flowlines, yet another industry first,to a CAtenary Leg Mooring (CALM) buoy,the largest of its type.The buoy, moored to theseabed by nine anchor legs of a combination


PROJECT DESCRIPTION

The oil processing train canaccommodate 200,000 barrels

per day of crude.

Connection at the top of the riser buoyancy tank.

11

of polyester fiber and chain, is located 1.6 kilo-meters from the FPSO at a water depth of1,320 meters (4,330 feet). The export lineswere installed by a new offshore constructionvessel, “SaiBOS Offshore’s Field DevelopmentShip” (FDS) using its j-lay tower.

This innovative landmark project has beensupported by an international team of con-tractors and suppliers from Europe, North

The FPSO can process more than 200,000 b/d of crude, inject 390,000 b/d of water as well as 8 million cu. m/d of gas and store 2 million b of crude.

America, Africa and Asia. Some were asked to qualify existing equipment for the requi-rements created by Girassol’s deepwater loca-tion. Others were asked to develop new con-cepts, equipment and materials that had tomeet new, even more demanding criteria.The result has been to create a new catalog of concepts and systems for use by the off-shore industry in deepwater developmentsaround the world.

The loading buoy, moored 1.6 kilometers from the FPSO, is used to transfer crude to tankers.

The key design parameter for the flow assur-ance program is the arrival temperature of thefluids at the wellhead: 58°C (136°F).While thehydrate formation temperature is 20°C (68°F),of greater significance is that the Wax Appear-ance Temperature (WAT) is 40°C (104°F).Theseabed temperature is a standard 4°C (39°F) atthe 1,400 meter location.

This meant that the thermal design of the sys-tem required that the arrival temperature ofthe well fluids at the FPSO’s process systemhad to be above 40°C (104°F). In the event ofa production shutdown, the well fluids had toremain above 20°C (68°F) during a 16-hourcool-down period. After this period, hydrateformation is prevented by circulation of deadcrude and methanol injection.To minimize temperature loss in the wells,conventional brine was replaced with gelleddiesel oil in the production annulus. Thisreduces the effect of convection in the annu-lar spaces after well startup. The subsea xmas

13

OVERALL CHALLENGES

FLOW ASSURANCE& OFFSHORE INSTALLATIONFLOW ASSURANCE

Flow assurance is a subject that is never farfrom the lips of any engineer. Even beforeGirassol became a development, Total knewthat dealing with flow assurance issues wouldbe a key to the success of this project.These would eventually be divided into anumber of areas. There would be a need forthermal insulation for temperature mainte-nance to prevent hydrate formation and waxdeposition. Control of sand particles from theunconsolidated reservoir would have to bedealt with.The chemistry of the reservoir wasnot compatible with the use of untreated orconventionally-treated seawater for waterinjection purposes. In addition, there had to bea slug management strategy and a corrosioninhibition program.

An analysis of well fluids gathered during theexploration period revealed that there wouldbe a need for a significant thermal insulationstrategy from the wellhead to the FloatingProduction Storage and Offloading (FPSO)vessel, including the injection of chemicals andmethanol in the wellbore and at the xmas tree.

The pressure vs temperature challenge.

Two key design parameters: 58°C at the wellheadand 40°C at the FPSO’s process system.


FLOW ASSURANCE & OFFSHORE INSTALLATION

trees were identified as potential “cold spots”,or heat-loss locations, within the system,notably on add-on hardware items, such assubsea choke valves. It was thus necessary toinsulate these items and similar ones on thesubsea manifolds.Of greater concern was the design of the insu-lation for the flowlines and risertowers. At the time the projectwas launched, Total believed there was no insulating materialavailable on the market that hadthe correct characteristics thatcould provide both the insulatingproperties of low-density foam andthe pressure resistance for the deepwater loca-tion of high-density material.The requirementswere also to be able to withstand the externaltemperature (90°C / 194°F) of the gas lift risers.

The material finally chosen was a glass syntac-tic foam with a pure amine hardener devel-

oped by the Balmoral Group of Aberdeen.Thedevelopment of the material – with a density of590 kilograms per cubic meter and a thermalconductivity of 0.12 watt per meter kelvin –was only one problem solved. Balmoral had to develop a manufacturing process for thisnew material and to provide 4,000 foam mod-

ules for the three riser towers and7,800 foam modules for the flow-line bundles. In all, Balmoral hadto deliver 10,000 cubic meters offoam modules.The issue of sand control wassolved through the use of twodifferent methods for the produc-

tion wells. For horizontal wells, open holedesigns with sand screens were employed. Inlow angle wells, gravel-packed completionswere used. In addition, acoustic sand detec-tors are installed on each xmas tree to providean operational warning should sand produc-tion commence.

For horizontalwells, open holedesigns with sand screens

were employed.

75 cm in diameter, the bundle lines are insulated with syntactic foam and designed to keep the crude oil at 40°C.

� Insulating foam

� Production line

� Service umbilical

�

�

�

15

Of quite significant importance has been scalemanagement. As previously mentioned in theproject description, the water injection capa-bility of the process plant is 390,000 barrels ofwater per day. The typical sulfate content ofthe seawater in Block 17 is 2,800 milligramsper liter while the Girassol formation watercomposition contains sufficient quantities ofbarium, strontium or calcium – 4,000 mil-ligrams per liter, 230 milligrams per liter and225 milligrams per liter, respectively – to sug-gest a sulfate scale deposition potential of 320 grams of barium and calcium sulfate percubic meter of produced water.This presenteda threat of deposition from the productiontubing to the topsides.

The use of downhole chemical injection wouldnot have sufficiently protected the entire sys-tem.The only answer was to remove the sul-fates from the water. There have been other

sulfate removal systems used offshore in theGulf of Mexico and the North Sea, but nei-ther had to deal with such large quantities ofinjection water or meet such a low sulfateobjective (40 parts per million).The result wasthe design and installation on the FPSO of thelargest sulfate removal system ever built.The final aspect of the flow assurance challengeis slug management. Simulation suggested possible adverse effects of slugs on the FPSOtopside. The slug management strategy onGirassol relies on preventing the formation ofslugs, not dealing with them.The use of riserbase gas lift and riser choke attenuation com-bine to form a slug suppression strategy.

INSTALLATION

At a 1,400-meter water depth location, theinstallation of equipment was always going tobe an important element. This included notonly the setting up of equipment on the seabed,but the connection of the various elements ofthe system to one another.During Phase one of the development, forexample, 127 subsea connections had to beexecuted between the various subsea compo-nents – xmas trees to manifolds, manifolds toflowline bundles and flowline bundles to theriser towers.Two different connection systemswere deployed for this work – the MATIS(Modular Advanced Tie-In System), devel-oped by Stolt Offshore, was deployed for thebigger flanged connections, while FMCKongsberg Subsea’s CAT (Connection Actua-tion Tool) was used primarily for the mecha-nical tie-ins associated with the subsea xmas

Sulfate removal unit.

Slug mitigation.

Equipment installation at a 1,400-meter depth location.


FLOW ASSURANCE & OFFSHORE INSTALLATION

trees and the manifolds. Each had to be quali-fied – for shallow water trials and deepwatertests in a fjord in Norway – before being takento offshore Angola.

Other key elements of the system – the flow-line bundles, the riser towers and the exportlines – were either totally new technology orhad never been deployed at such water depths.As a result, new procedures had to be engi-neered and developed to cope with all of theuncertainties associated with each of these ele-ments.These included deepwater bottom towof the flowline bundles, the tow and upendingof the riser towers and the installation of themidwater export lines by the j-lay method.None of these techniques had been attemptedbefore.The full details of these installations aredescribed in separate sections.

One of the organizational challenges con-fronted by the installation contractors – StoltOffshore and Bouygues Offshore – was thelarge number of vessels that were to be usedfor the activities.These included:

�“Seaway Polaris”, lowering of a variety of subsea packages including suctionanchors, manifolds, spools and jumpers...and j-lay of the injection lines;

�“Seaway Eagle”, lowering of subsea packages;

�“Seaway Explorer”, towing of production bundles and riser towers,tie-in of spools and jumpers using MATIS and CAT systems;

�“Seaway Kestrel”, diving activities at top of riser towers, installation of insulation covers on connectors;

�“Seaway Legend”, metrology and support to other vessels;

�“Malila”, tie-in of spools and jumperswith CAT system;

�“SaiBOS FDS”, installation of flexible jumpers between FPSO and riser towers, installation of umbilicals, j-laying of export lines,tie-in of umbilicals with CAT system.

“SaiBOS FDS”, one of the numerous specialized vessels used by the installation contractors.

17

These were only the main vessels. A fleet ofsupply boats, tugs, barges and other surfacediving support vessels were involved and theiroperation had to be organized, coordinatedand deployed.A number of the vessels deployed also had toundergo modifications to ensure their suitabil-ity for these deepwater operations. For exam-ple,“Seaway Polaris” was fitted with a new j-laytower for the installation of the water injectionflowlines and with an active heave compensa-tion system to ensure the correct location andorientation of the seabed equipment.Deepwater handling tests were also carried outin 1,500 meters of water off West Africa with“Seaway Polaris” to confirm dynamic responseof loads hanging from the crane. Each tower isfounded on a 20-meter long suction anchor,

placed to a positional tolerance of 5 meters.To install these, the crane on “Seaway Polaris”was upgraded to handle a load of 450 tons at2,000-meter water depth. Numerical model-ling showed that a heave compensation systemwas not necessary off West Africa.

To support the installation program, an arrayof stands for seabed transponders was installedto allow vessels and drilling units to locatethemselves within a unique referencing posi-tioning system.This would allow each vessel tosimply install its own locating transpondersand be able to begin working with a mini-mum amount of calibration.These stands havebeen left in place for field life for the position-ing of intervention vessels and for future fielddevelopment extensions.

“Seaway Legend”,specialized in metrology and support to other vessels.

exploration specialists believed these to be gas-bearing with low reservoir potential. It wasdecided to focus attention on a more shallowTertiary structure.Elf Aquitaine chose to target this structure in 1995 as part of its four-well commitmentprogram under the license terms. This well,dubbed “Margarita-1”, was not a success interms of hydrocarbon discovery, but revealedmany details about the structure in general.There was excellent porosity and permeabi-lity in the target sands and there were sand-prone sequences that pointed the explorationteam in the direction of where the next welllocation should be. This would be in evendeeper waters, but at shallower depth belowthe mudline where the source rock would be easier to find.In the early part of 1996, the well GIR-1 wasspudded aiming at Tertiary structures in thewestern portion of Block 17.At 1,100 metersbelow the mudline, hydrocarbon-bearingstructures were found. The results from log-ging, including resistivity and pressure data,

19

TECHNICAL ASPECTSRESERVOIR

When Elf Exploration Angola (now Total)began its exploration activities on

Block 17, offshore Angola, in 1993, it believedthat it had some idea of what it was going tofind. Having operated the onshore Block 3,there was a belief amongst its geoscientists thatthey would find similar geological structuresdespite the much deeper waters (1,400 meters).They found something different.The reservoir on the Girassol field is turbiditicin nature with unique characteristics. It is madeup of unconsolidated sands – coring samplesrevealed them to be not dissimilar to whatmight be found on a beach – with a porosityabove 30%, a high gas to oil ratio (GOR) anda reservoir pressure near bubble-point. It is alsoa classic deepwater field with shallow hydro-carbon-bearing structures below the seabed.The submudline location of the structures isbetween 1,100 meters and 1,200 meters.

A two-dimensional (2-D) seismic survey pro-gram which was begun in January 1994 originally revealed what were major Creta-ceous era structures between 3,000 metersand 4,000 meters below the seabed. The

The reservoir is made up of unconsolidated sands with a porosity above 30%.

Two-dimensional seismic survey of Cretaceous era structuresbetween 3,000 meters and 4,000 meters below the seabed.


TECHNICAL ASPECTS: RESERVOIR

The reservoir characteristics were establishedfrom wireline logging and coring acquisitiongathered during the drilling of the initialdevelopment wells.There is, though, a region-al fault pattern across the structure with con-siderable sealing potential which would have asignificant effect on communications betweendevelopment and injection wells and thus theirlocations in the field. In order to determinethe sealing potential, it was decided to under-

suggested good structure, although it was dif-ficult to recover cores due to the unconsoli-dated nature of the sands.These early results convinced the explorationteam to undertake a well test, the first on thisblock. This exercise proved the potential ofthe reservoir as the well tested at 12,500 bar-rels per day of 32° API crude.The success of this well convinced Elf Explo-ration Angola and its partners to undertake an extensive 3-D seismic survey over targetareas in Block 17. The results defined thepotential of the Girassol field, i.e. a minimumof 1,000 millions barrels of crude.

In total, the licensegroup drilled 17 explo-ration wells across Block17 before Girassol cameinto production at the

end of 2001. Only two of those wells wereunsuccessful, providing Total with what will be a string of development opportunities overthe next five years.

Despite the success of the drilling program, thereservoir specialists were confronted by somespecific challenges in developing this reservoir.The Girassol system is comprised of three differ-ent turbiditic structures. Each channel is sub-stantial – several kilometers wide,many kilome-ters long and around 50-100 meters thick – andseparated from each other by regional seals.

GIR-101 (PN1): Oligocene reservoirs

2430

2440

2450

2460

2470

2480

2510

2520

2530

2540

2550

2560

2570

2580

2590

2600

2610

2620

2630

2640

2490

2500

2510

2520

2530

2550

2560

2570

2590

2600

2610

2620

2630

2640

2650

2660

2670

2680

2690

2700

2710

2500

2540

2490

2580

1

2

3

4

5

Top SEQ 4

Bot SEQ 4

Bot SEQ 3U

Bot SEQ 1

S 6

Top Sheet 3

Bot Sheet 3

Top SEQ 3U

Upper Shale

Lower Shale

Sequence 4

WOC= - 2621m/msl

Sequence 3 up

Sequence 1

Sheet S3

GR / CALI RHOB/NPHI RESISTIVITYm/RT

COMMENTSm/msl

Massive sandLaminated sand Mud turbiditeHemipelagic shaleDebris-flows

27202650

8

7

Reservoir description on GIR101.

Random line GIR-101 / GIR-103.

A string of development opportunities

over the next five years.

21

take a well interference test between twowells prior to the startup of production byanalyzing data from downhole pressuregauges. The development team deployed aSubsea Acoustic Monitoring System (SAMS),another industry first. The SAMS, whichinterfaces with a subsea xmas tree and its con-trol system, gathers and stores data from thegauges subsea for retrieval at a later time.Thiscould be via acoustic transmission or by directretrieval by a ROV. A key feature of theSAMS design was its ability to be ROV-retrievable for use at various locations.The operation of the SAMS was a success. Inthe initial test between wells GIR-101 andGIR-103, which involved shutting in one well and injecting water into the other, the testwas able to confirm communication betweenthe structures and show that the faults werenon-sealing.This method of well testing avoided the needto burn crude oil, fitting in with Total’s non-flaring philosophy.

Girassol reservoir: a considerable sealing potential. Subsea Acoustic Monitoring System (SAMS).


The drilling and completion of a programof 39 subsea wells at 1,400-meter water

depth would be a challenge for any operator.The fact that the work was to be carried outby a pair of newbuild drillships exaggeratedthe potential for problems.

The drilling and completion (D&C) team hadan impressive set of objectives to meet. It had to drill 8 high-productivity (20 - 40,000 bar-rels per day) wells before first oil to meet theplateau production target.The well design hadto be reliable to minimize workovers. Com-plex subsea completion equipment had to beinstalled at a water depth where the industryhad little experience.And due to the high costof rig operations, non-productive time (NPT)had to be kept to a minimum.

What complicated the NPT issue was that therisk factors involved in drilling offshore Angolaare totally different from industry experience,for example in the North Sea. In the lattersector, the biggest risk is the environment,meaning the weather.Water depth and infra-structure represent low risks, while logisticsare considered medium. At Girassol, a remotedeepwater location in an offshore sector withfew support services, logistics,water depth andinfrastructure all represent high risks, while thebenign weather conditions are at the oppositeend of the spectrum.

There were two other issues of concern to theoperator. One was to limit the complexity ofthe well design, despite having to cope withtwo different types of sand control philoso-phies based on well type. And with a longdrilling program planned, there was a need to maintain personnel continuity to ensurethat improvements gained by experience andlessons learned during operations were incor-porated in general practice.

The amount of capital at risk was substantial.Based on an industry standard of 30% NPT perwell, with 39 wells planned at an average of30 days per completion and US$ 300,000 perday rig rate, the project was exposed to a poten-tial of US$ 105 million of added costs.The basic problem for the project, though,wasrig availability. Early on, it was realized that not only were there a limited number of rigscapable of working in the water depths atGirassol, but many of those which existed were

WELLS

TECHNICAL ASPECTS

Production results in barrels of oil per day (BOPD).

23

already on long-term charter. It was decidedthat it would be necessary to order newbuildunits – dynamically positioned drillships werebelieved to be the best option to avoid interfer-ence with seabed equipment – to execute thedrilling program. A contract was signed withPride International to supply these units.

The main design challenge for the wells was to deal with the unconsolidated sands. Twodifferent types of lower completions wereemployed – open holes with screen-only forthe horizontal wells and gravel-packed (fracpack) completions in the deviated wells.Thiswas complicated by the variation in grain sizein the Oligocene reservoir. Screen-only designwould not do for finer sands nor could it beused throughout the entire horizontal drain.Essentially specific designs had to be chosenfor specific locations.

The issue of NPT proved to be less of a prob-lem than originally thought. Over the first 14 wells, the NPT was just under 19% andimproved from the first seven through the second seven.

Another rig cost-related issue – completiontime – improved during the project. For thefirst 12 wells, the average completion time was192 hours or exactly eight days per comple-tion. The twelfth well in the program wascompleted in just 110 hours and Total hasdecided that this should be the future target,a reduction in time of three days or nearlyUS$ 1 million per well.

Total non-productive time (NPT).

Completion system.


The subsea production system at Girassol isan adaptation of the HOST 2500 equip-

ment developed by FMC Kongsberg Subsea.Although the basic HOST (Hinge-OverSubsea Template) system has been deployed in various locations around the world, thisadaptation of the equipment for operations to2,500 meters (8,200 feet) has received its firstuse on this project.

Each well has a vertical subsea xmas tree – thepressure control device – of a 5 inches by 2 inches design with a design life of 20 yearsand a minimum pressure rating of 5,000 psi.Each sits on a permanent guidebase.The ver-tical tree was chosen as it was field proven atthe time of the development and it requiresonly a single trip with the blowout preventer(BOP) for installation, a process which is verytime consuming and costly in a deepwaterdevelopment. Each tree is fitted with a tree cap which is installable and retrievable by aRemotely Operated Vehicle (ROV).The subsea configuration is two productionwells per manifold, connected by a well jumperand an umbilical jumper. The manifolds arethen “daisy chained” up to four in a row.Thefurthest manifold is 6 kilometers from theGirassol field center, the Floating ProductionStorage and Offloading vessel (FPSO).

Each manifold sits on a manifold supportstructure with levelling capability which itselfis supported on the seabed by a Closed CaissonFoundation (CCF) structure (5.7-meter dia-meter) with a design penetration of 10 meters

in the soft soil conditions at Girassol. Thedesign calculations were validated and theCCF self-penetrated to a depth of 8.5 meters.The installation design was based on an accu-racy of +/-5%,as the original basis of +/-2.5%was originally believed to be too stringent. Itwas subsequently determined that the morestringent accuracy is feasible.There are also six pig loop modules associatedwith the network of production manifolds.

XMAS TREESAND MANIFOLDS

TECHNICAL ASPECTS

Each manifold sits on a manifold support structure,supported on the seabed by a Closed CaissonFoundation (CCF) structure.

These allow for the running of pipeline clean-ing pigs through the flowline network.Water injection wells are located individuallyand linked to the water injection flowline sys-tem by a series of in-line tees and well jumpers.

The subsea control system is based on a top-side control console which monitors 41 sub-sea control modules.Each subsea xmas tree hasan SCM, as does each manifold. The controlsystem interfaces with sensors at the xmas tree(pressure, temperature, valve position, sanddetection) and at the manifolds (pressure, tem-perature, pig signal, multiphase meters).In total, there will be 39 subsea xmas trees – 23 for production, 14 for water injection and two for gas injection.Each production treeis externally insulated to reduce heat loss andprevent hydrate formation. During cooldown,

25

each production tree is inhibited with me-thanol with dead crude circulation. Otherequipment associated with the productionxmas tree includes a retrievable insert chokevalve, a sand detector and a Subsea ControlModule (SCM).

There are stringent technical requirements onequipment for such a deepwater location dueto the cost of replacing equipment and generalconcern about “infantmortality”which is thefailure of equipmentat an early stage in itsoperational life. FMCKongsberg Subsea and Total decided to sub-ject many individual items of equipment– 40 items in all – to a qualification program.Amongst the items which had to be qualifiedwere the 5.1/8-inch deepwater actuator, thesubsea multiphase flowmeter, the riser controlmodule, the workover control umbilical, thecompact monobore and multibore connectors,the thermal insulation and the tie-in tools.In addition, a comprehensive test program was undertaken to verify the elements of the subsea production system before delivery.The test program included factory acceptancetests, sub-system tests, integration tests, shal-low water tests, pre-delivery stack-up testsand a range of other tests, such as deepwater tie-ins, ROV interface, thermal insulation ofxmas tree, etc.Xmas tree pending subsea installation.

3-D view of manifold with connection tool.

Stringent technical requirementson equipment for such a deepwater location.


The production flowlines which transportwell fluids from the manifolds to the three

riser towers were fabricated, like the towers,onshore as complete and insulated structures.

For the first phase of the development, a totalof 18 kilometers of insulated flowline bundleswere fabricated and towed for installation atthe field. That total was built up from eightseparate bundles, varying in length between700 meters to 3 kilometers with all but twoof them exceeding 2 kilometers. In the sec-ond phase of field development another threebundles are to be installed, totalling 4 kilo-meters in length.One by one, from April to July 2001, the firstphase bundles were towed and placed at their

appointed positions in the five productionloops which link the field’s daisy chain of subsea manifolds. Each bundle takes the formof a 30-inch carrier pipe that contains two 8-inch production lines and a 2-inch serviceline, encircled by two semi-cylindrical syntac-tic foam modules.

One of the carrier pipe’s main functions wasto protect the package during the 220 kilo-meters on-bottom tow from the fabrication siteto the field, while the syntactic material pro-vided buoyancy (a submerged weight of about90 kg/m) and insulation. It also helps resistexternal pressure and contributes to overallthermal performance of the system because itprevents any entry of seawater into the bundle.All voids are filled with inhibited water.At the ends of each bundle is a 15-meter sledwhich serves both for the tow-out operationand as structural support for tie-in spools.Thesesleds weigh 25 tons in air and carry a 20-tonbuoyancy module.

Design criteria for the production system is a pressure of 270 bar and a temperature of70°C (158°F). To minimize paraffin deposits,oil has to arrive at the FPSO at a temperaturenot less than (40°C / 104°F) for a flow rate of10,000 barrels per day.In shutdown conditions, temperature has toremain above 20°C (68°F) for 16 hours at allpoints in the line to prevent hydrate forma-tion.This means that all potentially cold spotssuch as spools and connectors also have to beinsulated, using insulation shells and covers.

INFIELD FLOWLINES

TECHNICAL ASPECTS

Each of the 30-inch carrier pipes of the bundle containstwo 8-inch production lines and a 2-inch service line.

27

For standardization purposes, the foam modules are the same material as used in theriser towers. After the intensive program todevelop a new syntactic foam for the project,the supplier Balmoral had to manufacturesome 7,800 modules to insulate the flowlines.Together with the 4,000 modules provided forthe riser towers, this represents 10,000 cubicmeters of high-density foam in a materialnever fabricated before.The modules are 6 meters long with profilesdesigned to interlock and provide a tight fit. When a 12-meter long full-scale section of flowline bundle was tested to assess ther-mal behavior a convection phenomenon wasnoted here, undermining insulation perfor-mance.Additional seals were fixed to respondto this problem.

In mid-2000, flowline bundle constructionbegan at the Soyo yard,325 kilometers beyondLuanda. As they took shape on the yard’s 5-kilometer production line, the bundles werepulled in 230-meter increments into a lagoonwhere they awaited towout.An earlier test tow had set the parameters forthe bottom-towing operation to move thebundles to the field.To confirm the tow routeand select the best anti-abrasion material, a 12-inch pipe coated with different materialswas bottom-towed from Soyo to the field andback again. As a result, a 7-millimeter thickcoating of polypropylene was selected for thecoating of the carrier pipe.When the time came for towout of the eightflowline bundles, “Seaway Explorer” was able to carry out the work with a maximum bol-lard pull in the order of 200 tons.The bottomtows – including hook-up and final position-ing – averaged eight days each,with the quick-est taking five and a half days.

The concepts developed for this project pro-vide reference points for upcoming deepwaterdevelopments. In addition, Girassol has provi-ded invaluable experience, identifying most ofthe challenges which affect deepwater devel-opments and defining some of the limits oftechnical solutions.

During the first phase of the Girassol devel-opment more than 125 subsea connectionshad to be executed using three different connection systems. All the tie-in operationswere carried out using rigid spool pieces orjumpers, fabricated onshore following the use of subsea metrology.

This project marked the first use of the deep-water version of Stolt Offshore’s MATIS(Modular Advanced Tie-In System).Althoughsophisticated in operation, this system is a low-cost option as it is based on the use of indus-try-standard bolted flanges.The system simplyaligns two pipe ends, installs a gasket betweenthem and then torques a series of bolts to theproper tension.Deep MATIS consists of two units – a FlangedAlignment Frame (FAF) and the ModuleDeployment Frame (MDF).The tool is 6.2 mx 3.6 m x 3.8 m and weighs 23 tons.With itshandling structure, the weight in air is 51 tons.Work is in progress to decrease the size andweight of the tool. The FAF, a frame withclaws at either end, picks up the pipe end orspool and aligns the flanges. The MDF, whichcan slip into the middle of the FAF, handles allof the bolts, the insertion of the gaskets and

View of flanges bolted using MATIS.


TECHNICAL ASPECTS: INFIELD FLOWLINES

conditions with all connections to be per-formed at a minimum of 2 meters above theseabed, avoiding interference with the soil andthus turbidity.The tie-in system is a novel ROV-deployedconnection tool.The connections included:� flowline connection: monobore 8 inchesand multibore 8 inches, 2 inches and four by 1 inch;� umbilical:multibore 10 by 0.5 inch and upto seven electrical quads;� production well jumper:multibore 6 inch-es, 2 inches, eight by 0.5 inch and two electri-cal quads;� and injection tree: multibore 6 inches,2 inches and four by 0.5 inch.The 2-inch andthe 0.5-inch lines are terminated in a Multi-bore Quick Connect (MCQ) plate on the ter-mination head to receive a flying lead.

the torquing. In the configuration for thisdeepwater application, the two units aredeployed together.MATIS is being used for making both hori-zontal and vertical connections, the former onthe top of the sleds at the ends of the flowlinebundles and the latter at the base of the risertowers.A total of 52 flanged connections wereexecuted in the first phase of the project.

The connections associated with the xmas treesand manifolds were carried out using FMCKongsberg Subsea’s Connection ActuationTool (CAT).The CAT,which weighs 2.5 tons,activates a mechanical connector and allowshorizontal connections in line with the pipe.The weight of each connector is around 5 tonsincluding the stabbing system.There were a number of requirements for thistie-in system. It had to be simple and reliable,reducing the number of connections throughthe use of multi-bore connectors.There was apreference for horizontal connections whichallow module retrieval independently of oneanother.The system had to have high flexibil-ity regarding the surface support vessel. Itsdesign had to allow deployment from either adrilling unit, or a pipelay vessel or a small sup-ply boat. It had to be able to adapt to seabed

Reception of a MATIS package.

29

The manifolds and trees contain the hub whilethe termination heads includes a 10-inch colletconnector. The connector is the same for allexcept for the bore configuration.The ROV-deployed CAT lands on the termination headand the hub.The tool first strokes the connec-tor and flowline forward and closes the con-nector. To verify connection, a low-pressureback seat test is performed.

The connection between a bundle head andmanifold or tee and tree is a spool piece basedon a rigid pipe design.The well jumper has a“Z” shape and is installed horizontally. At alater stage in the project, a U-shaped jumperwas developed to eliminate the need for spe-cialist installation vessels.The jumpers, prefabricated in Norway, have a termination head at each end. Based on

metrology of the actual location, the finaljumper layout is established and the prefabri-cated spools are cut to suit and welded togeth-er. Insulation is then applied and testing finalized prior to transportation to quayside.In addition to factory tests, these tie-in systemshave been subject to extensive qualificationtesting in Norway.This included shallow watertests in Bergen and Haugesund and deepwater tests in Sognefjord.

F ifty-two MATIS connections were performed– 13 vertical and 39 horizontal. The averageduration for a tie-in operation is estimated at14 hours, while the time to close each flangeis about nine hours.

Forty-six CAT connections were performed atan average duration of around five hours.

Flowline bundle construction at the Soyo yard.

The 5-km long production line.

30 GIRASSOL - A STEPPING STONE FOR THE INDUSTRY

One of the most challenging aspects of any development in water as deep as at

Girassol (1,400 meters) is the riser system whichtransfers fluids from the seabed to the process-ing facility on the surface and vice versa.

At Girassol, this challenge was made evengreater by the need to provide substantialinsulation to the riser pipes – as well as the restof the flowline system – so that the temperatureof the crude oil is maintained as it makes thelong journey from wellhead to FPSO deck.These needs have been met by the project’sthree unique free-standing riser towers.Girassol’s wellstream comes to the surface via

twelve 8-inch diameter steel riser pipes withanother six of the same diameter provided for water and gas injection. These are gath-ered in three groups of six pipes around acentral structural core pipe of 22 inches indiameter with the whole assembly encased inan insulating syntactic foam material whichalso adds buoyancy.The result is three long thin towers, less than 1.5 meters in diameter and measuring1,280 meters from seabed to their top at apoint 50 meters below the water’s surface.These long strands are more or less weightlessin water due to the buoyancy provided by theencasing foam.

RISERS

TECHNICAL ASPECTS

Each riser tower is 1,250 meters in length and 1.5 meters in diameter.

�Production line

� Structural tubing

� Service umbilical

� Gas-lift line

� Injection line

�

��

��

31

They are held upright in tension by a steelbuoyancy tank at the top that provides 520 tonsof uplift, leading the whole assembly to behavelike an inverse pendulum, hinged at the top ofits suction anchor.This arrangement also yields the great benefitof relieving the FPSO of nearly 2,000 tons of load which would otherwise hang off theproduction vessel if a conventional catenaryriser system had been used.The top buoyancytanks provide a connection point for the fair-ly short shallow water catenaries of flexiblepipe which complete the final links betweenriser tops and the FPSO.While the riser towers are easy to describe, theypresented a pioneering engineering effort todesign, qualify, build and install.There was noprecedent for Total to go by and the contrac-tor Alto Mar Girassol pushed out into thisuncharted territory.

The riser towers have their origin in a designcompetition set up by Total in summer 1997and the scope specified stringent insulationrequirements. Criteria included preserving aminimum oil delivery temperature of 40°C(104°F) at the FPSO to avoid wax deposit andduring shutdown a minimum of 20°C (68°F)for 16 hours.In July 1998 the riser tower design was select-ed as the successful proposal from the threesubmitted.This decision was based on a num-ber of criteria including the overal thermalbehavior of the concept. It involved bringingtogether the risers in three insulated groups,each formed by the six 8-inch pipes, plus four3-inch gas-lift risers and two 2-inch serviceline risers.After winning a design competition at the startof the project,AMG and foam module suppli-er Balmoral went through a testing period to achieve the desired thermal performance.In summer 2000, not long before tower cons-truction was due to start, tests on a 12-meterlong full-scale section of prototype towerrevealed that thermal insulation capabilitiescould be undermined by a “plume” effect.This phenomenon involved very small move-ments of warmed seawater rising within the

body of the tower in the annuli around themain riser pipes.The adopted solution was toadd open-cell foam around the riser pipes toprevent this movement of water.This yielded adramatic improvement in performance.Also a bitumen/PVC coating was added tothe whole exterior as a further barrier to theflow of water into or out of the tower. Thisadditional work was completed without affect-ing the project schedule.

The buoyancy tank provides 520 tons of uplift.


TECHNICAL ASPECTS: RISERS

To build the Girassol towers a mechanizedproduction line was set up at the Lobito yardon the Angolan coast, 450 kilometers south of Luanda. Individual pipes were first welded.These then converged onto a main assemblyline where foam modules and final coatingwere added. As 48-meter long sections oftower were completed, the leading end wassteadily fed out into the bay. The first towertook two months to build and the third less than a month, with production averaging96 meters of tower per day by the end of construction.

With the complete 1,280-meter long towersfloating in the bay, the top buoyancy tanks,transported from France, were added. Thesetanks are complicated structures in their own right, weighing 450 tons and measuring40 meters long.They taper from 8 meters indiameter to 5 meters, have 28 internal com-partments and are pressurized internally withnitrogen. Installation of structures such as these riser towers also took large steps intounknown territory. First there was the chal-lenge of towing these vulnerable 1,280-meterstrings for 600 kilometers from constructionyard to offshore location. It was essential that as little as possible fatigue life be used upthrough motions induced by waves and seacurrents on this journey.Once on location, the base of each tower hadto be hauled down to its anchor point,maneuvering the 3,400-ton mass so that it wasfirst swung down from horizontal to vertical,then stabbed into permanent position.All thiscalled for extremely thorough pre-planningby AMG and its team.

At the start of the project,AMG identified theriser tower installation as an operation withsignificant levels of risk as no such installationoperation had ever been carried out before.The consequences of any incident would havea severe impact on the project as a whole.In reality, towing and installation were com-pleted without a hitch. In rapid successionover a 25-day period from mid-June to mid-July, the three towers were towed out from

Umbilical support arch

Riser tower system components.

Rotolatch connector

Suction anchors

33

shore, upended to the vertical and latched totheir pre-installed seabed anchor points at loca-tion. The first tower began its journey fromLobito on June 16th, 2001, latching eight dayslater.The third tower was latched on July 11th

after a five-day operation.

F atigue, rather than structural strength, hadbeen a critical factor in much of the planning.Fatigue considerations dominated the choiceof towout route, which was influenced by thebest combination of current, swell direction,significant wave height and exposure time.With one tug at the front and another at therear exerting 30 tons of back tension, eachtower floated on the surface for the journey tothe field, apart from the top tank at the rearwhich was submerged 50 meters. Speed was3.5-4 knots. In the event, fatigue induced inthe tower was less than expected.Extensive model testing and full-scale trialshad been included at the planning stage.This included a full-scale towtest in Scotland to ensure thatthe external skin of the tower didnot peel off and a surface-towtrial with “Seaway Explorer” and“Seacor Voyager” to validate vesselprocedures and train offshorepersonnel.The upending of eachtower at the field was extremely spectacular,but as a result of careful detailed engineeringit was achieved without any incidents. Theweight of an 80-ton deadman anchor, cou-pled with movement of the tug, was used tomake the riser foot dive in a controlled man-ner with no need for water ballasting. Anadvantage of this operation was that it wasfully reversible.

Docking with the suction anchor was criticalas it was difficult to predict the dynamic res-ponse of the tower under the excitation loadsof the deadman anchor and leading tug.As the tower moved to the vertical andapproached the flex-joint assembly on the pre-installed suction anchor, two syntheticrope pull-down slings were passed to theanchor by an ROV. This allowed the tug to

pull the tower down and stab its base into theRotolatch connector.Once properly secured, deballasting of the top

buoyancy tank could proceed,building up tension in the tower.A further unique operation wasthe placing of large umbilicalsupport arches at hangoff pointson each tower. These weredeployed off “Seaway Polaris” inhorizontal configuration, gently

landed on their supports, then allowed toswing down to the vertical and secured byROV-activated clamps.

The success of the Girassol project and theexperience gained firmly establishes the risertower concept as an important solution fordeep and ultra-deep field development pro-jects. That success is a direct result of theefforts put into engineering preparation.This presented the twin tasks of meeting theindustry’s most challenging thermal insula-tion requirements and ensuring installation of each tower using conventional spreads.The project team now has a clear vision ofhow such a large structure behaves in openseas and the knowledge of how to extend theGirassol experience to other fields in evengreater depths.

The success of theGirassol projectestablishes the

riser tower conceptas a real solution.

Umbilical support arches were deployed off “Seaway Polaris”.


With its vast size and large process capacity, the Floating Production, Stor-

age and Offloading (FPSO) vessel at the centerof the Girassol layout can justifiably be called “le plus grand FPSO du monde”.The vessel’s huge oil storage capacity of twomillion barrels gives it a length of 300 metersand a width of 60 meters. The blunt-nosed,ship-shape unit – with accommodation for140 people – has a maximum operational dis-placement of 400,000 tons.On its deck it supports facilities to process200,000 barrels per day of oil.This is one ofthe highest oil production rates seen on anyfloating platform anywhere in the world, quiteapart from the impressive volumes of waterand gas also handled on the installation (seesub-section on process facilities).

Even though the FPSO (including exportbuoy) has accounted for US$ 920 million outof the US$ 2.8 billion total project cost, thiswas below the final target price.And the unitmet its revised schedule for completion.

An FPSO such as this can best be described asa refinery on a super-tanker.The building ofsuch a vessel brought together two differentcultures – shipbuilding and the oil industry.The clashes between these two cultures haveled to a number of unhappy experiences onprevious large FPSO projects. So Total and itsmain contractor, Mar Profundo Girassol, putconsiderable emphasis on minimizing thepotential for such problems on the project.A central part of the strategy was to seek maxi-mum separation between hull and topsides.By minimizing the number of functions in the hull, the shipbuilders would be able to go forward with hull construction in their tradi-tional way, while “oil industry” functionscould be concentrated in the topsides.

One innovation at Girassol is the 7-meter highcellar deck concept, using a module supportframe to hold all process equipment and mostof the utilities above the ship’s main deck.Thisproved very practical in reducing the amountof interface between hull and topsides – at theheart of so many past problems – and allowedpipework of all kinds to be run in it.In early planning, the complete topsides wereexpected to be assembled on a 140-meter longModule Support Frame (MSF) on the quayside,then skidded onto the hull as a single piece.

FPSO

TECHNICAL ASPECTS

The FPSO is at the center of the Girassol layout.

35

However, the topsides weight increased byabout 30% from the initial estimate because oflate influences such as the need to add substan-tial water treatment. It should be noted that thisgrowth – to 25,000 tons – did not have anyimpact on the hull.This had been designed toaccommodate uncertainties in the topsides.Because of the increased size of the topsides, arebid exercise was undertaken at the end ofbasic engineering. As a result, in June 1999,the work was relocated to Hyundai’s OffshoreDivision yard at Ulsan, Korea.This was closeto the site of hull construction which hadbeen sub-contracted to Hyundai’s ShipyardDivision fourteen months earlier.In Korea, a modified approach was taken toinstallation of the topsides.The MSF was liftedonto the hull in tenpieces and the topsidesthen built on it in amore piecemeal man-ner over a one-yearperiod. Lift weight of outfitted structures var-ied from 350 tons to a maximum of 700 tons.Construction of the 42,000-ton hull wascompleted on schedule in 18 months in Octo-ber 1999.The safety record was excellent, witha Lost Time Incident (LTI) frequency rate of0.65.The hull was then immediately towed tothe nearby Offshore Division yard for assemblyof the topsides above its main deck.The 25,000-ton topsides had the ambitioustarget of completion by March 2001, just 21 months after contract award.This requireda workforce of more than 2,000 personnel at peak construction time.An outstanding safe-ty record was achieved in this work with anLTI frequency rate of 0.41.Sailaway from Korea was at a level of com-pletion and commissioning never beforeachieved for a production unit of such com-plexity. Overall, a new benchmark was set by completing such a project just 33 monthsafter contract award.

The vessel arrived off Angola on July 10 aftera voyage from Korea lasting 100 days.Over theensuing weeks it was linked to its 16-pointcatenary spread mooring system. GroupedThe 90-meter high flare tower.

The safety record was excellent,with a Lost Time Incident frequency rate of 0.65.


TECHNICAL ASPECTS: FPSO

four at each corner, these lines maintain theFPSO in a fixed heading and keep its lateralmovements within 70 meters (5% of waterdepth). Each line uses a 1,775-meter length of125-millimeter sheathed spiral strand wire,with short sections of studless chain at top andbottom, and a 17-meter long suction anchor inthe seabed.Anchoring at the field was complet-ed in August, allowing final hook-up and com-missioning to get under way. No major prob-lems were encountered and the first well on theP-10 production loop was opened on Decem-ber 4.This meant that the project achieved thechallenge of coming on-stream three and a halfyears after sanction and award of main con-tracts.After impressive ramp-up of production,the first cargo of one million barrels of oil wasoffloaded at the end of December.

Although the FPSO has a 90-meter high flare tower, this was only used until the gasinjection system became operational in April 2002.After that early stage, gas will notbe flared, but re-injected to await productionat a later stage.

PROCESS FACILITIES

Large volumes of oil, water and gas are dealtwith by the 25,000 tons (dry weight) of topsides equipment on the Girassol FPSO’sdeck. To process the wellstream, the topsides

Lift weight of outfitted structures varied from 350 tons to 700 tons.

are designed for an oil production rate of200,000 barrels per day, and also to treat180,000 barrels per day of produced watercoming up with the oil from the reservoir.The plant includes two very large oil desalters– 30 meters long and 4 meters in diameter.

The gas in the wellstream is dehydrated andcompressed by facilities designed to handle upto 8 million cubic meters per day (equivalentto 50,000 barrels per day in oil terms).Then

37

a portion of that gas is channelled to the production risers to provide gas lift while therest is re-injected at 285 bar to maintain reser-voir pressure.As well as treating produced water, the facilitiesalso have to process a large volume of seawaterto make it suitable for injection into the reser-voir to help maintain drive pressure there.Thenature of the reservoir means that the world’slargest sulfate removal plant – able to treat390,000 barrels per day of seawater – had to be

The FPSO: a huge floating refinery.


added to the process layout after contracts hadbeen awarded (see below).The water injectionplant is sized to provide 390,000 barrels perday of water at a pressure of 150 bar.

To deal with all these tasks, deck space onthe FPSO is shared out equally between sixmain functions: manifolds, oil processing,water processing, gas compres-sion, power generation, offload-ing and metering.The vessel’s power demand is40 MW, rising to 50 MW duringoil offloading. This is provided by three 26.4-MW heavy-dutyturbo generators, along with var-ious secondary and backup generating capac-ity. Gas compression is performed by twounits, each rated at 25 MW.

The sulfate issue was one of the major chal-lenges to emerge during the course of theFPSO project. It arose with the relatively latediscovery that substantial amounts of sulfateswould have to be removed from seawaterbefore it could be injected for reservoir pres-sure maintenance.Studies revealed a high strontium and bariumcontent in samples of water from the reservoir.If seawater with a high sulfate content was

injected into this reservoir, there was a signifi-cant risk that the ensuing chemical reactionscould produce enough barium sulfate to buildup and plug the production tubing.Conventional scale inhibitors would not beeffective enough in Girassol’s long daisy chainedlayout of remote subsea wells.The only reliablesolution was to use a nano-filtration membrane

process on the platform. Not onlyis this process uncommon off-shore, but the need to treat amighty 390,000 barrels per day ofseawater resulted in the world’slargest water sulfate removal plant.The filtration system was pro-vided by US Filters plant, using

480 tubes,each containing six membranes fromDow Chemicals. It reduces the sulfate contentof the water from more than 2.800 grams perliter to less than 40.Seawater is taken aboard the FPSO from aninlet 90 meters below the sea surface, wheretemperature is in the range 13°C-20°C (56°F-68°F). Before reaching the sulfate removalplant, the water passes through several stages offiltration (including 16 multi-media filters)and de-oxygenation. After sulfate removal,the treated seawater is then pressurized up to150 bar by three injection pumps and directedto the injection wells on the seabed.

Topsides general layout.

The world’s largestwater sulfate

removal plant:390,000 b/d ofseawater treated.

TECHNICAL ASPECTS: FPSO

39

There are a number of features of theGirassol development which have estab-

lished new concepts for the offshore industryand the export system is one of them.As off-shore developments have moved into deeperwaters, the industry has studied various newmethods for exporting production.

There were a number of issues for Total toconsider when choosing a method of trans-porting the processed crude oil 1.6 kilometersfrom the Floating Production Storage andOffloading system to the export buoy. Onewas the effect of temperature and its impactwhen moving dead crude from a floating facility down to the seabed at 4°C (39°F) andthen back up to the surface. Another was theinstallation method of the system and theeffect of the installation method on the long-

term life of the system.And the final issue wascost.The system was to be based on the largestCAtenary Leg Mooring (CALM) buoy everbuilt and which had never been installed insuch deep waters.The buoy weighs 650 tons(715 short tons), is 18 meters (59 feet) tall witha buoy body height of 10 meters (33 feet),

an overall diameter of 23.3 meters (76 feet)with the buoy body itself to a diameter of 19 meters (62 feet).

The thermal requirements were such – thetemperature loss of the crude oil had to be lessthan 3°C (38°F) – that it was not possible totake the flowlines to seabed, where the watertemperature is 4°C (39°F), and then back tothe surface at the loading buoy.This mitigatedin favor of a midwater transfer system.

EXPORT SYSTEM

TECHNICAL ASPECTS

Export system: a large “W” whose upper line is 2,400 meters long and varying in water depth from 440 meters to 530 meters below the surface.

TECHNICAL ASPECTS: EXPORT SYSTEM


The design of the export system needed totake into account a number of considerations.It had to accommodate different fluids in thelines which had an impact on the shape of thelines. It had to have the flexibili-ty to deal with variations in dis-tance between the two FPSOand the CALM buoy, includingin the extreme case, with oneline broken. There was also aneed to be able to handle themotions induced by the FPSOand the loading buoy. This is particularly critical at the buoy end of the lines.

Detailed analyses were undertaken to assessthe overall behavior of the three interactingsystems: FPSO, export lines and offloadingbuoy. The export lines, due to their near neutral buoyancy state, are particularly sensi-tive to environmental factors. Thoroughfatigue calculations were required. Parametric

analyses with a set of wave scatter diagramswere performed which resulted in the needto reinforce the export lines at the CALMbuoy. The wall thickness of the pipe was

increased on the last 300 metersof the export lines close to theCALM buoy and studjoints were added.After considering the use of flexible pipe, it was decided thatthis option was too expensive.The decision was taken to install

a system comprised of two 16-inch rigidpipelines configured like steel catenary risersin their midwater locations like a large “W”.The upper line is 2,400 meters and varies inwater depth from 440 meters below the sur-face to 530 meters below the surface. Thelower line is slightly longer at 2,750 meters and is installed somewhat deeper in a range of630 meters below the surface to 740 metersbelow the surface. The main sections of the

Details of export lines leaving the FPSO.

The export linesare particularly

sensitive to environmental

factors.

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line, made of API 5L X65 steel, have a wallthickness of 14.3 millimeters, but the final 300 meters of the pipeline at the CALM buoy increase to 25.6 millimeters.The lines,which have flexjoints at each end, are coatedwith 6 millimeters of polypropylene and eachhas a series of 29 buoyancy floats to create the desired shape of the pipelines.

Once the concept was chosen, the decisionon how the lines were to be installed had tobe made. The initial plan by contractor AltoMar Girassol was a subsurface tow to site.Structural analysis subsequently revealed that a significant amount of the fatigue life – up to one-third – of the pipeline would beconsumed by this method and it was decidedinstead to opt for the j-lay method usingBouygues Offshore’s new installation vessel,the “Field Development Ship”.Detailed calculations had to be performedand static analysis used to determine the

installation program including the angle ofthe j-lay tower, the allowable vessel move-ments and the lay tension. It was also deter-mined that the most critical phases of theinstallation would occur while passing thebuoyancy modules through the lay vessel’sstinger and at the final transfer of the exportlines to the CALM buoy.

The installation of the first line – the upperone – required 10 days. One lesson learnedwas the time necessary to handle and installthe 12-ton / 6-meter long flex-joints.After aperiod in which the “FDS”was used on otheractivities, it returned and installed the lowerline. Operations were optimized based on theexperience from the first installation and thiswork was even more successful.In order to continue to monitor the mostvulnerable section of the upper line, straingauges have been installed. Data from these gauges and from metocean buoys willprovide validation of the fatigue design ofthese pipelines.

The j-lay tower on “SaiBOS FDS”used to install the 12-ton/6-meterlong flex-joints.

STRENGTHENING THE LOCAL ECONOMY

At the two onshore construction sites, localcompanies were encouraged to participate inthe construction and assembly work as well aslogistics and transport.Preference was given tolocal contractors whenever competitive, result-ing in the creation of hundreds of jobs for peo-ple in surrounding communities.Both the localcompanies and their employees will be able touse participation in this high-tech project asan invaluable reference in future projects.

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INTEGRATING THE PROJECTINTO THE COMMUNITY

To ensure that Girassol plays a longer termrole in the sustainable development of

Angola and its energy resources,Total and itspartners made every effort to foster know-how transfer via training for local personnel as well as integration of Angolan engineersand technicians into project teams. Local con-struction was also a priority for all projectpartners.

TECHNOLOGY TRANSFER

As operator,Total was committed to provid-ing Angolan managers and technical staff with training and hands-on experience andto give professional opportunities to local staffas soon as they were suitably qualified.Duringthe pre-production phase, engineers, cost-controllers and a contracts specialist wereposted to the Pau project HQ in southernFrance, several engineers were part of the HQ operations team in Luanda, and a largenumber of Angolan drilling techniciansworking with Pride Foramer gained invalu-able experience of offshore drilling and com-pletion techniques. Total helped to trainAngolan personnel working on both drillingvessels and has guaranteed them employmentfor the next five years.This policy of Angolanization has continuedwith ongoing recruitment and via trainingprograms for local employees as well as OilMinistry and Sonangol personnel, costing $ 4-5 M each year.By the end of 2000,75% ofproject personnel in the country were Angolannationals, including 44% of managerial staffand foremen-supervisors. So Girassol will notonly generate a significant increase in Angola’scrude production, but will give a considerableboost to the local oil industry’s ability to pur-sue future projects.

Total provides Angolan managers and technical staff with training and hands-on experience and gives professional opportunities to local staff.


INTEGRATING THE PROJECT INTO THE COMMUNITY

The Soyo construction yard, operated byPetromar (an Angolan-registered companywith Sonangol and Bouygues Offshore asshareholders), where the flowline bundles forthe subsea production system were assembled,was set up specially for the Girassol project.

Some 150 workers wererecruited locally andtrained by Petromar inwelding, coating andother assembly tech-

niques, with Total supervising qualification.The existing construction site at Lobito, man-aged by Sonamet (an Angolan-registeredcompany with Sonangol and Stolt as share-holders), was equipped with a mechanizedproduction line for assembly of the complex

riser towers. The loading buoy and suctionanchors were also constructed there by localcontractors and using Angolan labor. Theworkers were given additional metallurgicalskills to meet the stringent specifications andstandards involved in offshore work (i.e.weld-ing techniques required for equipment thatmust withstand high water pressure). Hereagain, the contractor Sonamet handled train-ing with Total monitoring qualification.With 800 people employed at the Lobito siteduring peak activity, Girassol has significantlystimulated the regional economy.

TOWARDS RESPONSIBLE USE OF RESOURCES

With the Girassol project, Total and its part-ners have proved that deep-offshore hydrocar-bons can be produced economically andresponsibly under extreme conditions. Thisresounding success makes Girassol a referencefor future oil development, demonstrating the role that technology can play in optimiz-ing Angola’s resources, in opening up respon-sible development of Block 17 and furtheroffshore discoveries, whether in the Gulf ofGuinea or elsewhere, thus leaving otherresources for future energy consumption. Forthat is what sustainable hydrocarbon develop-ment is all about – using all available technol-ogy (3-D seismic acquisition, reservoir model-ling, multiphase pumping and transport,horizontal and multidrain wells, assisted recov-ery) to explore, assess and produce oil and gas.Making the most of resources available in eachreservoir, each deposit, each oil province, andso leaving further resources to be tapped bycoming generations.

Like extra-heavy oil, deep-offshore hydro-carbons (and a fortiori, very-deep offshoredeposits) were regarded until recently asuneconomic resources that could not beconsidered as reserves. Technology is nowavailable to produce both economically, andthese “frontier” resources are beginning tomake a meaningful contribution to a morediversified world oil supply. Any seriouscommitment to sustainable developmentrequires that these resources be tapped.

Some 150 workers were recruited locally and

trained by Petromar.

At the two onshore construction sites, preference was given to local contractors.

out comprehensive preliminary studies andtaking all necessary measures. Environmentalstudies, carried out in cooperation with anumber of specialist international consultants,included site baseline surveys and environ-mental impact studies, both offshore and atthe onshore sites, as well as an oil-spill con-tingency plan.

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In all its activities wherever it operates,Totalconsiders safety in regard to operations and

human health and respect for the environ-ment as paramount priorities. No develop-ment project is ever undertaken withoutprior assessment of all risks to safety, healthand the environment over the entire life ofthe project, implementation of all necessarypreventive measures and preparation of rele-vant contingency plans. Total complies withall applicable laws and regulations wherever itoperates, as well as applying the Group’s ownstringent Health, Safety, Environment andQuality Charter.

SAFETY: A PARAMOUNT CONCERN

On Girassol, full safety audits were carried outat the Soyo and Lobito construction yardsonshore, at the shipyard building the FPSO in Korea, as well as aboard all vessels operat-ing on the project. Safety was given particu-lar emphasis at Lobito and Soyo, where largenumbers of local staff were working withwhat, for many of them, were new techniquesand equipment. Project team Safety Managerswere appointed for each site to ensure thatcontractors and subcontractors complied withsafety standards regarding prevention, accidentresponse and awareness training for all relevantpersonnel. As operator, Total insisted on fullreporting of accidents and subsequent remedi-al preventive measures.

PROTECTING THE ENVIRONMENT

At each stage of the project, every effort wasmade to protect the environment by carrying

SAFETY& ENVIRONMENT

Protection of the environment was given top priority throughout the project.


SAFETY & ENVIRONMENT

OFFSHORE AND ONSHORE

Environmental measures taken offshoreinclude:� gas re-injection to eliminate flaring

and valorize energy resources;� use of low-toxicity, oil-based drilling

mud;� treatment of drill cuttings discharged;� treatment of all water discharged;� recovery of turbine exhaust heat and

reuse in various FPSO processes.In addition to regular monitoring, a follow-upeco-audit will be carried out after drilling is

completed in 2004, again at field half-life after7-8 years, and another on cessation of activity.Among the measures implemented onshorewere detailed precautions at Soyo to protectthe mangroves and adjacent area – shown bythe baseline study to be a breeding ground fortortoises – when the sealine bundles weretransferred from the lagoon to the sea.Care was also taken to minimize channelwidth and avoid creating a continuous linkbetween the sea and the lagoon while cuttingthe transfer channel, as seawater would havedisturbed the lagoon’s sensitive brackish-water ecosystem.

DEEP-SEA MILIEU STUDY PROGRAM

Given the potential for future development inthe area,Total is carrying out a wide-rangingregional study of the deep-offshore milieu.Deep-sea ecosystems are along the most bio-diverse on Earth, but little is known aboutthem. In conjunction with the Frenchoceanographic institute Ifremer, Total hasundertaken a 3-year oceanographic campaignoffshore from Gabon, Angola and Congo covering water up to 4,000 m deep.The aimsare to categorize (inventory and analysis)marine life at great depth and assess thepotential impact of oil exploration and pro-duction activities.The Girassol project is using specialized sur-face vessels and unmanned submersibles,probesand sensors for marine-life sampling), drift-buoys for particle analysis and quantification,drift modules to study biodegradability ofdrilling mud and cuttings, and sea-bed core-sampling apparatus. It also involves coloniza-tion experiments to study and compare theresponse of benthic organisms to the additionof fish-meal (enriching their milieu withorganic matter without any toxic effects) andto drilling mud (organic matter with a poten-tially toxic effect).On comparison of the quantity, diversity and composition of the benthic fauna follow-ing each phase of enrichment, researchers observed no evidence of toxic effects (partic-ularly concerning direct mortality on themost abundant species).

Picture credit: C. Dumont-Graphix Images & L. Zylberman-Graphix Images (except p.25, p.27, p.28, p.33, p.41); Mapping: Idé p.3; Computer graphics: S. Jungers p.14 & p.30; Cover: DigitalVision/J.Farine; Graphic design & realization: Accroche-com’; Printed in EU by Stipa. © TOTAL – May 2003.

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