total brings onstream second deepwater hub in angola's prolific block 17

8/7/2019 Total Brings Onstream Second Deepwater Hub in Angola's Prolific Block 17

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GEOGRAPHIC FOCUS: WEST AFRICA

M l b r in g s o n s tp e a m s e c o n d d e e p w a tei A n g o la 's p r a i i i i b lo c l i U240,000 b/d of o i l year-end target

Jeremy BeckmanEditor, Europe

I ate last year, oil started flowing from Total's second productioncenter in Angola's block 17. Dalia, like its forerunn er Girassol,is being developed via one of the world's largest F P^O s linkedlo an extensive network of deepwater subsea wells.There the similarities end, however. Dalia's shallower sub-surface location presented greater difficulties in well design, due tothe need for a steeper drilling radius, and the field's extent wouldrequire twice as many wells to develop. Also, its Miocene crude ismuch heavier than Girassol's Oligocene oil, and cooler on outflow.This would necessitate mo re intensive flow assurance mea sures, bothto saf('.iiii;ird p assag e nf fluids to th e Fl'SO nt the cnrrt'rt trm por nltirr .and lo counter hydrates huikkip during shut-downs.Prior lo its merger w ith Total, Elf discovered Dalia in Septem1 9 9 7 , as part of a prolonged drilling campaign in the previously drilled d eepwa ter block 1 7 , Tlie field. 2 ' M ) sq km (89 sq mi) in areasituated 135 km (84 ini) offshore A ngola's Tiorthern coast, in wadepths varying from 1,200 to 1.5U0m (3,93710 4,921 fl). Recov erareserves are estimated at close to 1 Bbbl of oil.Dalia's four main reservoirs were formed over 25 million yeago following the accumulation of sediments at the mouth ofCongo River. Over time, periodic subsea avalanches shifted thsediments out to Ihe deep offshore, where they were depositedand along the edges of seabed channels.Today the turbiditic, unconsolidated and heterogeneous resvoir sands, lying at a subsurface depth of 8(K) m (2,625 ft), are seral kilometers long, with varying thickn ess. All contain viscou s aacidic crude (21-23 API), witli relatively low outflow temperatuof4.'"vri(l" C,

The 984-ft-long Dalia FPSO is equipped to handle 240,000 b/d of oi l .


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Dalia FPSO on Angola block 17.

According to Dalia's project di-rector. Daniel H eard, Total startedpreliminary an;ilysis of tlie fieldantl its geology in 1998. One of themain p reoccupations was resolvinguncertainties over the sedimentcomposition: Clay deiiosits causecompai^tmeiitalizadon in Dalia'sreservoir sands, in turn constrain-ing connectivity and hampering oilflow.During the project's ooncei>tual stages, ABB in Den Haagl)erformed basic engineering, butTotal's in-house team managedsubsequent engineering studies,before subm itting th e final devel-opment plan to Sonangol in 2002.From the outset, siiys Picard, in-sulation of suhsea equipment v/asthe overriding concern for Elfand its block 17 partn ers Exxon-MobU. BR Statoil. and Hyd ro.

Development optionsAngola's government sanctioned a de-velopment plan in May 2003. The subseaproduction system, aviârded early on toKvaerner Oillield Produc ts, v/ould be one ofthe world's largest for adeepwater project,with abase case of 67 wells, comprising 34producers, 30 water injectors and three gasinjectors (two to beconverted later on forwater injection). There would be an optionto expand the total to71 wells, should thepartners decide to tie in the nearby Mioceneaccumulation Ciimellia.Due to tbe relatively shallow subsurfacedepth, ali would be highly deviated - near-horizontal within the reservoirs - with anavt-rage drain length of 1,100 m (3.609 ft),and drill-through horizontal Christmas trees.These wells would be tied into nine mani-folds connecting 40-kin (25 mi) of 305 mm(12-in.) pipelines in four production loops, tomaximize coverage on the seabed. Producedfluids would head lo the FPSO throug h eigh tflexible production riser bundles; reservoirdrive would be assisted by four 305-mm (12-in.) water injection lines and associated ris-ers, and two 305 mm (12-in.) gas injectionflowlines, with 75 km (47 mi) of steel tube,control/power umbilicals.Technip secured a contract for the um-bilicals, risers, and ilowlines. manufacturebeing split among the company's flexiblepipe production center in northern Franceand its new umbilical plant in Angola. Tech-

nip was also contracted for pre-installationof the FPSO's mooring system, installationof the subsea manifolds, and all associatedsubsea tie-ins.Total contracted Samsung Heavy Indus-tries (SHD for the 50,802-nietric ton (56.fX)0-ton) FPSO hull, with a turnkey contract forthe 27,216-metric ton (30,000-ton) topsidesawarded to theDalia Mar Profiindo jointventure of Technip, Saipem, and Stolt Off-shore (now Acergy). in partnership withfabricators SHi and Daewoo (DSME).The 300 m (9M ft) long, 63 m (207 ft) wide.32 m (lO.'i ft) high FIÔ would he equippedto handle up to an average of 240,000 b/ d ofoil, with two proce ssing trains to heat incom-ing crude and separate out gas and water. Itwould also have total liquids handling capa-bility of 400,000 b/d, oil storage capacity of 2MMbbl, and gas compression capacity of upto 8 MM cm/d .Subsea networkTotal and Scjnangol had san ctioned Kvaern-er Oilfield Products (KOP) to start pre-engi-neering for the subsea production system latein 2002. Tlie full EPC contract the followingApril covered t he supp ly of 67 Christmas treesand associated wellhead systems, along withnine six-slot subsea manifolds, two workoversystems, and related connection equipment.

Th e 178 mm (7-in.) and 140 mm (5 1'2-in)drill-through, horizontal trees, each measur-

ing5x5x4m (16x 16x1311) weighing around 40 metric t(14 tons), are designed to conand monitor jx'ocluced reserfluids, water, and gas injection.production will be commingal nine manifolds, each with stor up to six wells, before headihrough Dalia's subsea piix'Hsystem to the FIÔ. Water u:as injection trees are being cnected on a standalone basisMil i[ il rdic ated injccti(ni lines .

.\11 tiic manifolds have dinîons of 14 X 8 X 8 m (46 x 26It), weigh around 140 metric (154 Ions), and incoiporate la:ind small bore piping mid v;i\or hydraulic control and cheminjection via umbilicals. Due lonature of Dalia's reservoir Iluthermal insulation of the prodtion equipment must he sguarded at all times to sustainoil temperature above the hydformation ]K)int.KO i''s fxten sivf fiualillcatests for this equipmen t took oa year to com plete. Followingsembly ill Tranby, Norway, tfirst production christmas was sent tothe company's complex inerdeen early in 2004 for controls integratesting, while the lirsl water injection was shipped directly to the company's mafold fabrication yard in Tarragona, northeSpain, for underwater performance tests20 m (66 ft)of water.These shallow water tests - the first econducted at the port of Tarragona - beat the end of 2004, using a poriside cranlower the injection tree onto its wellhead.ROV then connected aproduction tree pre-installed manifold, the tree being linto the sh ore via an umhilical.Tlie main objectives were toprove the primary equipment items could functindividually, connect to each oth er and oate in unison, and could accommodate Rintervention at a future point. To enscompliance with temperature constraihot fluids were placed in som e of the subequipment components to verify flow asance and temperature controls. KOP/Talso conducted a cool-down test to assprocedures for the prevention of hydformation. For the ROV operations, spetools were developed for installation ofbles, turning clamps and valves.During summer 2(K)4, the Schlumbergdesigned completion strings linking

trees with the reservoirs underwent tmonths of system integration tests in Hoton, prior tofinal assembly. Total selec


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seven different completion designs for Da-lia. including two 'smart' confifiuratiotis.Qtialificalion involved individual compo-nent and sub-systetn testing to ensure com-pliance with Dalia's (luids specifications. Thecompletion was then assembled and run intoa horizontal test well to validate runnin g op-erations and functionality for workovers andinterventions.For the initial phase of development drill-ing. Total contracted two deepwater drill-ships towork in parallel, thePride Africaand the Pride Angola, both of which had alsoserved on Girassol and the subs equen t tie-inof Rosa/Urio.

Th e twin imperatives of heat conservationand hydrate formation prevention meantthat all fluid-bearing flowiines and lisers hadto be heavily insulated, to guarantee that;1. During normal production periods, oilexiting the reserv oir at 46 C could not arriveat the FPSO at a temp erature below 'M C.2. In tlie event of a shutdown, ihe fluidstemperature would no( fall below 2V C be-fore the line's integrity had been preserved.'ITie solution for the flowlines was acon-figuration of four pipe-in-pipe prod uction lineloops resting on the seabed. Total selectedAerogel, an efficient insulation medium withan OHTC of around 0.65, to [ill the annulus

intervals with good accuracy."Technip's initial analytical programthe Dalia IPBs involved seven tnonthsmaterial (|ualitication tests, m echanical teincluding 'crushing', bending and pulliand subsequent deepwater immersion pformance tests at a location offshore Brato validate the IPB's design integrity.The main puipose of the deepwaler triwas to provide feedback on the behavioiIhe tensile armor layers under buckling cditions. Technip submitted the pipe sectto cyclic curvature variation, as mightinduced by the FPSO's motions, while asubjectitig the pipe to external pressu

NASA had developed this material (Aerogel)for space applications, but Dalia representedthe first use in an offshore setting.

Dalia's light architecture well trajecto-ries, all designed byTotal in-house, wererelatively cotnplex in certain cases. Amongthe main challenges would be the need tosustain an accurate drain trajectory throughproductive reservoir layers varying from 80m (2fi2 ft) thick in the field's main channelsto just a few me ters on th e Hanks.Development drilling started in Febru-ary 2005. and the 67 wells are expected totake 2.500 days, or close to seven rig years.to complete. Pride Angola is due to work onRosa mid-2007, but Pride AJriea will remainon station for the duration of the program."The drill-lhrough design of the treesimproves drilling times and productivity."Picard explains, "as it allows us to install tlietrees earlier in the drilling sequence, and todrill the wells in batches without having tolift and re-install the BOP each time." Fol-lowing setting of the first production and in-jector trees, tbe multi-purpose construction

vessel Bourbon Jade has taken on this role forthe time being . "Although tree installation isusually performed by therig."Picard says."installation bycable from a multi-puiposevessel is quicker, and the day rate is alsolower."Flow managementTotal discounted both steel catenary ris-ers and riser towers, tbe latter first tried onGirassol. asbeing far too heavy for Dalia'sFI'SO. To optimize flow of the heavy crud e,and the associated need for gas injection, thecompany opted instead for a network of 305tnm (12-in.) risers andflowlines.Tliese wereconfigured to maximize production while si-multaneously controlling multi-phase flows.

between the inner 305mm (12-in.) and outer432 mm (17-in.) carrier pipes. NASA haddeveloped this material (Aerogel) for spaceapplications, but Dalia represented the iirsttise in an offshore setting."We are using a silica-based version withan average pore size of around 10 nanome-ters and apore size distribution of typically

2-50 nanometers." says Picard. "Tlie Aero-ge l is combined with reinforcing fibers toproduce sheets that are further processedin 2-m (7-ft) long blankets, comprising fourlayers."Another innovation was the selection ofIntegrated Bundle Production risers (IPBs)- aTechnip concept - to convey producedfluids from the flowlines to the FPSO. Theeight IPB risers, each \.6S0 m (5,413 ft) longand 800 metric tons (882 tons) in weight, areflexible, allowing them to yield in all direc-tions to sea cu rrents.Within all thebundles, 24 gas-lift tubes(each comprising (iO elements) and six elec-trical trace heating cables are wound aroundthe 305 mm (12-in.) flexible pipe core, with10 layers of insulation provided to ensurefluids heat retention. Tbe 3-m (lO-ft) longend-fittings each weigh 15 tnetric tons (17tons).A distributed temperature system , basedon optical fibers, p rovides tetiiperature mon-itoring throughout the length of each riser."The principle." Picard explains, "is basedon the tetnperature along the fiber lengtbbeing a function of a shift in the light spec-trum. The distance from the beginning ofthe liber is calculated throug h "time of flight'measurement- This allows us to obtain atemperature profile of the fiber at 1-m (3-ft)

After eacb cyclic test, the team released clipers, which w ere allowed to slide down pipe section. Any stoppages en route wohave indicated diameter variations brouon by buckling.Technip then cut U|) ihe test IPB for ther analysis antl validation, also cimductfull-scale vertical thermal tests over a thr

tnorith period to confirm thermal charteristics and performance. These involvmeasu ring tbe heat exchan ge coefficient, heating jjerformance. and cool-down lime'Hie IPBs were manufactured in two bates of f(ur at Technip's factory in Ix- Trainorthern France; collectively the 10 layrepresented tbe biggest diameter (584 m[23 in.]) the compjuiy had produced for offshore project. I^Trait also supplied tdedicated flexible risers for each of the fwater injection pipelines and the two gas jection lines, and ihe FPSO export line (below).Technip has also engineered the flexirisers to manage dynamic stresses and crosion concerns. "There is a potential prlem of hydro gen suKide in D alia's gas whcould migrate horizontally through the ricarcass," Picard points out. 'To counter thyou need a material that is H2S-resistant -a high er grad e stainless steel - but this am ake s it difficult to maintain the riser's mchanical properties. It was a very compdesign process - our solution involved u s15 different m ateria ls for th e risers."

FPSO constructionFirst steel sections foi" Ihe Fi^SO's hull wcut in January 2(X)4. Work at SHI's drydostarted tliree months later, with the comple


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liull being launched in August that year. InMay 2(H)5, the Dalia Mar Protuu do L-onsortiiiminstalled the topsides on the hull at DSMH'sard in Geoje Island.According to Picard. the deck is not asspacious as Girassol's, where room was leftIroni the outset to accommodate the later-|)hasc tie-in ()f Kosa and Lirio. "When we^larted on this project six years ago withlbe low oil price, we had to be careful nollo over-dt'sign the lacililies. 'Hiere w as som eebate at the time about leaving space forfuture modules, but in the end we decided.(gainst the extra cost of increasing the sizelthe hull."TIK' project team opied for a modular ap-proach, incontrast toCiirassol's 'pancake'deck solution. '"'Iliat gave us more flexibilitylor the construction. At the time, we weren't

ure that all the modules could be built inne place. T he K orean yards had a hugeorkload at the time, so It was not easy toliiul slols for this project. However, SHI hada slot available lo assemble tbe hull and also-;(inir module construction capacity, so In(he end. we split tbe 12 modules betweenIhem and DSMI'^, 'lliis turned out to be aood choice, as the project was not delayed."In our case, some of Ihe modules endedlip wfijj:hiiig over 3,,500 metric tons (3.858

tons), and we had to bring in a crane fromJapan for tbe assembly at DSME. We endedup relatively steady at the basic engineeringfigure for the topsides of 30,000 metric tons(33,0(59 tons), but it took some ingenuityto stay within this weight. For instance, weused more sophisticated and expensive ma-terials or steel grades for the pipes than hadbeen allowed for in the original plan."(")ne of the major issues affecting the top-sides process design was the composition oiDalia's crude, whicb brings the risk of naplvthenate formation during production. Undercertain conditions (temperature, pressure,and acidity), the napbthetiic acids normallydissolved in Dalia's crude are liable to pre-cipitation, leading to formation of deposits inpipework and pressure vessels.T otal had cond ucted various stu dies (fthis phenomenon, at times wilh the part-ners ' assistance. Statoil. for instance, hadexperience countering naphthenate forma-tion offshore N orway. T he solution for Daliacombined anti-naphthenate injection at th eriser base, via the gas-lilt tubes, with a noveltechnique involving lirst-stage oil. water, andgas separation u nder pressure.'T ests have shown that some crude oilsform naphthenates al higher acidic values,"Picard explains. "During the treatment of

acidic oils, the pH increases througho ut theentire process when Ihe pressure decreases.A pressurized system maintains acidity at alevel lower than pH 6.2, where equilibriumexists between the pH and the carbon diox-ide partial pressure, inhibiting Ihe prwipila-tion reaction."GF Oil & Gas supplied the FPSO's powergeneration andcompression equipment,which comprises three 24MW P(iT+25gas turbine generators: twci high pressurelurboconipressors (two PGT+25 turbinesdriving four compressors); and two sets oflow pressure and export/injection electricmotor-driven compressors operating at50Mpa (.500 bars). "We are using a very fancycoupling for the gas injection compressor,"says Picard. Sulzcr provided tbe three injec-tion pumps, two driven by Solar Taurus gasttnbines, the other powered by a 5.25MWelectric motor.T he seven-deck. 2.500-metric ton (2,756-lon) living quarters module, also built bySHI. is located above five levels of machin-ery space in the hull, and can accommodateup to 190 personnel during shutdowns in 70cabins. Hie quarters module also housesthe control room, normally manned by justfour staff, whose duties include monitoringthe subsea control system, lli is is one of the

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world's largest, managing 17.000 underwa-ter control points. It was configured from theoutset to eventually s upe rvise 100 live wells,taking into account production from possiblefuture infill wells and satellite fields.Dalia's oil is exported via two 610-mm(24-in.}, 2-km (1.2-nii) flexible pipelines toan offloading buoy, accommodating tankerberthing. The offloading process normallylasting around 36hours. At Girassol. theSBM-designed buoy's mooring chains be-gan to fail not long after start-up. Althoughthe problem was eventually resolved. Totalopted for APL's turret-moored buoy solutionfor Dalia. foflowing a design competition.This 30 X 19 X 7.5 m (98 x 62 x 25 ft) stru c-ture weighs 650 metric tons (717 tons),Following onshore testing and commis-sioning, the FPSO sailed out of South Korea

on March 8, 2006. arriving in block 17 earlyin September following a brief stopover inCape Town. Fairmount. under sub-contractlo Technip, provided the ocean-going tugsfor the entire voyage.The FPSO was moored at ils offshore lo-cation by the Normand Installer. Accordingto Picard, the anchor pattern was designedio take into account the effects of long swellsin this region.Earlier, Technip's Deep Blue had insUilted all

the IPBs, pipe-in-pipes and injection lines, thecompany's Construetor managing installationof the umbilicals, subsea manifolds, the mooi'-ing foundations, and the production spools.Around 20 other vessels. Including tugs andbarge s, assisted in these various operations.Local manufacturingAs with all recenl deepwater Angolan de-velopments. Dalia has invigorated the localmanufacturing and offshore support sector.The existing Sonamet yard in Lobito, forinstance, built the hull and suction anchorsfor the offloading buoy, and seven of th efoundation bottom structures for tlie ninemanifolds. It also completed assembly of themanifolds.Nearby in I^jbito. Technip 's new umbilicalplant, Angoflex, manufactured most of th estatic and dynamic injection and productionumbilicals, and this base was also used forintegration of the subsea distribution unitsand umbilical termination heads.In Dande. 50 km (31 mi) north of Luanda.Technip found a location for a puniose-buillspool base for the pipe-iji-pipe. injectionpipelines and offloading lines assembly, alsoerecting a 600-m (1,968-ft) long jetty to ac-comm odate spooling onto the two pipe reelsonboard the Deep Blue. In Luanda itself, th e

Sonils Base und erwe nt ex tensions whichcluded a new work shop to house compleand w orkover control system s activities.Picard expects a final capex figure forDalia development of S4 billion. It is a slincrease due to external specific maconditions (price of steel, fuel, drilling vices). Dalia came on stream on Decem13 at 20.000 b/d of oil. "Our priority inearly stages is to gain production expence." However, the development plan cfor aplateau output of 240,000 b/d of oibe reached by the end of this yean "Qtions arebeing asked about how weachieve th is. Tlie answ er is. we will knowthis summ er But once lliere. we should at that level for at leasl four yea rs."

All the associated gas isbeing used tially for power generation and injectSome gas will be exported under Angoproposed multi-block LNd gas-gatherscheme in the future.Water and gas injection should come service by the end ofFebruary orearlyMarch. In time. Total may employ a viscficalion tech niqu e in its water injection wto further boost recovery, llie companalso contemplating acquiring a 4D seissurvey over the reservoirs tomonitor duction performaiict'. O

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total brings onstream second deepwater hub in angola's prolific block 17

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