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38 JPT APRIL 2009

In the best tradition of Nordic polarexplorers of the past, StatoilHydro ispushing into frontier territory withits Gja field development in theNorwegian sector of the North Sea.

Gja, named after the fishing vessel

used by Norwegian Roald Amundsento become the first explorer to navigatethe treacherous Northwest Passage, isitself heading into uncharted waters.StatoilHydro hopes the developmentcould open up a whole new area of theNorwegian Continental Shelf for mod-ern day oil and gas pioneers.

The Gja field and the Vega and VegaSouth satellites will be developed at acost of around NOK 38 billion (USD5.7 billion) with a new semisubmers-ible platform, which will sit in 1,210 ft

(370 m) of water 45 km off the south-western coast of Norway.

Recoverable reserves for the field areput at 82 million bbl of oil and conden-sate and roughly 1.4 Tcf (40 Bcm) ofgas. Vega and Vega Souths recoverable

reserves are estimated at 26 million bblof condensate and 636 Bcf (18 Bcm)of gas. Drilling work to tap the fieldsreserves is already under way and apilot well is currently being drilled tofurther delineate the field.

It is full steam ahead on all frontsas Gja Project Director and VicePresident for Field Development, KjetelDigre, explains: Everything is hap-pening right now. We have just startedon the actual drilling and completionprogram on the field.

We are just about half way throughthe build program, which is 58% com-plete. We are close to finishing the hullin South Korea. The major componentswill be brought to Aker Solutions yardin spring for assembly in the autumn.

The 15,650 ton hull is being builtby Samsung in South Korea and it willbe mated with the topsides at AkerSolutions yard in Stord, Norway. Thetopsides includes a 22,000 ton deckand the capacity to accommodate 100offshore workers will be provided by a1,650-ton living quarters module, withhelideck. The living quarters are cur-rently under construction at LeirvikModule Technology in western Norway.

StatoilHydro is operator for Gja inthe development phase, while Gaz de

Gja Development Opens New FrontierJohn Sheehan, Contributing Editor

GJA FIELD DEVELOPMENT

The project could open new areas for drilling. Photo courtesy of StatoilHydro.

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France takes over as operator whenthe field comes on stream. Licensees inthe license are Gaz de France (30%),Petoro (30%), StatoilHydro (20%),Shell (12%), and RWE Dea (8%).

Drilling Under WayStatoilHydro began production welldrilling in February on the first of 13wells that will be used to tap Gja,currently the largest development proj-ect offshore Norway. The TransoceanSearcher rig, which has undergone aUSD 28.5-million upgrade for the Gjaproject, will be kept busy over the com-ing years as it tackles nine oil wells andfour gas wells on the field.

The wells will be drilled through fivetemplates installed on drilling centers

on Gja South, Gja East, and GjaNorth. The first well currently beingdrilled is an appraisal well in the north-ern segment of Gja, which is locatedin the Sogn area of the North Sea inblocks 35/9 and 36/7, a new area for oiland gas production.

The Transocean Searcher is current-ly drilling a pilot well in the northernsegment of the field, said Digre. Thewell will show whether or not the oilcolumn in that segment is capable ofsupporting production in that area. It is

an important pilot well and we will getuseful information on whether or notto create an oil focus there or concen-trate on the gas.

Oil recovery rates are expected tobe just 20% from the field becauseof complexities in the reservoirs. ButDigre expects initial drilling of theproducers to provide vital informationgoing forward.

We will get a lot of information fromdrilling the initial production well. Itwill help us to decide whether or notto drill the wells in a certain sequence.Drilling in the first year will be crucialand quite challenging.

There are technical challenges relatedto the drilling of multilateral oil wells,which is something were focussing on.

We also have shallow water pockets inthe area which are overpressured andmeeting them in the upper part of theoil well could lead to washout on theseabed. We have done a lot to safeguardagainst this possibility, he said.

Satellite Field Tie-inThe overall plan for development alsoincludes the Vega and Vega South satel-lites, which will be developed with sub-sea installations tied back by a 32-km,14-in. pipeline to Gja, which was ini-

tially discovered in 1989. Mono ethyl-ene glycol (MEG) will be supplied fromthe platform and StaotilHydro has beenworking to further develop technologyfor the MEG regeneration system thatwill be used.

The Vega South field comprises thegas/condensate resources of the fieldpreviously known as Fram B and islocated approximately 10 km north-northwest of the Fram field.

Vega (previously called Camilla andBelinda) and Vega South will be devel-oped with three subsea templates, eachfeaturing two production wells, andtied back to the Gja platform.

Provision has also been made forthe tie-ins of further discoveries inthe area, according to Trond Bokn,

StatoilHydros Project Manager for thesemisubmersible platform. We havemade investments on the semisub plat-form to accommodate future tie-ins.We have the weight margin and areamargin to add modules and we haveadded extra riser slots for putting innew risers if necessary. We have madesome preinvestment to make it possiblefor Gja to become a hub in addition

GJA FIELD DEVELOPMENT

Recoverable reserves are estimated to be 82 million bbl of oil and condensate. Photo courtesy of StatoilHydro.

(Contd. on page 75)

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In case a second fracturing treat-ment is needed, the pad should notbe a crosslinked gel. It is very difficultto pump the pad into the existingfracture because of the high viscosityof crosslinked gel. The pad pushesthe fracturing slurry with proppantalready in the fracture with a piston-like movement, which makes the first

pumped proppant useless. Fluid lossis not a problem because a filter cakewas formed by the first fracturingtreatment. Therefore, linear gel mustbe used to finger into the existing frac-ture tip and propagate the fracture as aresult of its low viscosity.

Forced-Fracture-ClosureTechniqueIn the case of multiple pay zones, itis vital to prop each pay zone appro-priately. However, because of hetero-

geneity of stress and permeability,the propped-fracture profile may beimproper (i.e., different stress or per-meability of the pay zones may obtainthe same fracture concentration).Placing a higher proppant concentra-tion in the higher-permeability payzone with a lower proppant concen-tration in the lower-permeability payzone is the key problem.

A new method was adopted that firstflows back less than 1.0 m3 of fluidto draw back the proppant from thewellbore region; then, the well is shutin for approximately 1 hour to allownatural settling as a result of differentloss coefficients caused by differentpermeabilities (i.e., the proppant willflow from lower-permeability region tohigher-permeability region, as shownin Fig. 4). Finally, apply a forced frac-ture-closure technique.

Field ApplicationSix gas wells were hydraulically frac-tured in the Songliao basin. The basicparameters and the overall fracturing-

treatment parameters are detailed inthe full-length paper. As in the past,the total proppant weight was nor-mally less than 30 000 kg as a resultof premature screenout, and the post-fracturing performance was less than3000 m3/d. Therefore, the study andapplication of the low-damage andmassive hydraulic-fracturing techniqueput forward in the paper had a greatsignificance in this basin. JPT

to processing hydrocarbons from theVega fields.

There are two other finds in the Gjalicense and the nearby Agat, Peon, andAstero finds could all be tied back tothe platform. Bokn stressed there are asyet no concrete plans to develop any ofthe nearby fields but he said Astero was

a possibility.Gas from Gja will be transported

in a 135 km-long, 28-in. pipeline tomeet up with the UK Flags pipelinefor further transport to Scotland. Upto 87,000 BOPD will be shipped viaa 55-km, 15-in. pipeline to the Trollfield in the North Sea and sent onwardthrough the Troll II oil pipeline to theStatoilHydro-operated Mongstad refin-ery north of Bergen.

The oil and gas pipelines are beinglaid this year and a power cable supply-

ing electricity to Gja from the main-land will also be installed in 2009 andtied to the platform in 2010.

Power From Land

One of the most striking things aboutthe Gja development is that the plat-form will be StatoilHydros first floatingplatform to get its electricity from themainland, with a corresponding reduc-tion in emissions of 250,000 tonnesof CO2 per year. The platform will besupplied with electricity via a 100-kmcable running from the new powerplant at Mongstad.

The new high-tension submarinecable is set to be laid later this year bycontractor ABB.

Bokn added: On the semisub all theelectricity will be imported from shorethrough the power cable, which offers40 MW maximum production. Thereis one gas turbine on-board which isused to drive the export compressordirectly producing mechanical powerfor the compressor. We also produceheat from the exhaust of that turbine

for the platform.Hooking up the power cable to the

platform will not be without its ownchallenges, as Bjrn Midttun, ProjectDirector for pipelines and subsea instal-lations, explained. The biggest chal-lenge has been the qualification of thedynamic section of the power cable,he said. It is an industry first to hookup a floating production platform to adynamic power cable.

We also have a very steep slopenear Mongstad which gives us installa-

tion challenges. The last issue with thepower cable is that we are building anew vessel to install it on, which is notyet finished.

Bokn said that using an alternatingcurrent cable has the advantage thatless power-related equipment is need-ed on the semisubmersible than if a

direct current cable had been required.Another added advantage is that theregularity of the power supply is slight-ly better than generating the poweroffshore, he said.

By electrifying the platform witha cable, the energy that Gja needswill be produced with the environ-mental standard of the new Mongstadpower plant, Digre added. This giveshigh energy efficiency and reducedemissions of carbon dioxide, nitro-gen oxides, and volatile organic com-

pounds as compared with the alterna-tive solution.The coming year will see vast

amounts of work being carried out onthe project, with the accompanyinglogistical headaches that this entails.From a subsea and pipelines pointof view the installation schedule ischallenging, Midttun said. We havesome 20 vessels coming into playand in total there will be about 1,000offshore working days with those ves-sels. We have numerous contractorsand all this has to happen in a cer-tain sequence. Obviously complet-ing all the various components intime for the different vessels will bea challenge.

We are starting installation of thepipelines in April with Saipems Castoro6 and we will lay about 200 km of pipe.We then have an important interfaceinto Shells Flags pipeline system.

Following the flowline installationthe umbilicals and risers will be tied in,while the power cable will be installedin July and August. This will be fol-

lowed by all the different tie-ins of thestructures.

The logistical challenges are immenseand Digre hopes the 350 people work-ing on the project will display the sameskill and fortitude as the Nordic polarexplorers of the early 20th century.

We use the name Gja to try tobuild the organizational culture on theattitudes of the polar heroes. It is notjust a nameour ambition is Gja,based on history and building for thefuture, he said.

GJA FIELD DEVELOPMENT(Contd. from page 39)

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