DesignandInstallationofDeepwaterPetroleumPipelinesJaeyoungLee,P.E.MarinePipelineEngineer,Houston,Texas,USA1.AbstractTheexplorationofoffshoregas/oilhasbeenmovingtodeepwaterfieldsasbigreservoirshavebeenfoundandtechnologieshaveimproved.Presently,themostactiveareasindeepwatergas/oilfielddevelopmentareAfricaandtheGOM(GulfofMexico)inNorthAmerica.Therearemanytechnologicalchallengesindevelopingdeepwatergas/oilfieldssuchas:flowassurance,subseasystems,risersystems,surfaceproductionstructures,transportationsystems,etc.Thispapergivesanoverviewofeachdeepwaterfielddevelopmentconcernlistedabove.Thedesignandinstallationissuesofdeepwaterpipelinesarediscussedindetail.2.HistoryofDeepwaterFieldDevelopmentsSincetheactivepursuitofthedeepwaterfielddevelopmentsinthemid-80’s,theonsetofdeepwaterdepthhasnotbeenclearlydefined.Themanneddivinglimitof400m(1,310ft)hasbeenwidelyusedtodefinedeepwaterdepth.Drillingcontractorsandproducersuse610m(2,000ft),sinceafloatingstructureisconsideredtobeabetterfitinthisordeeperwaterdepths,comparedwiththefixedplatform.ManyindustriesandMMS(MineralsManagementService)ofDOI(DepartmentofInterior)oftheUnitedStatesuse305m(1,000ft)asthelowerlimitofdeepwaterdepth.Inthispaper,deepwaterisdefinedasanywaterdepthgreaterthan305m(1,000ft).Approximately200deepwaterdiscoveriesinGOMhavebeenidentifiedbyMMS(Table1).Totalestimatedworldwidedeepwaterreservesin1999were26.3billionboe(barrelsofoilequivalent)andincreasedto56.8billionboein2001,morethandoubleintwoyears[1].Figure1showsworldwidedeepwaterreservesbyregion.TheGOMhasshownaremarkableincreaseindeepwaterfielddevelopments.Partofthisisduetothedevelopmentofnewtechnologiesreducingoperationalcostsandrisks,aswellasthediscoveryofreservoirswithhighproductionwells.Thedeepestwaterdrilledtodateis2,965m(9,727ft)inUnocal’sTridentprospectintheGOM[2].GlobalMarineDrillingCompany’sGlomarC.R.Luigsdeep-waterdrillshipcandrillin3,658m(12,000ft)ofwater[3].Therearemanysophisticateddynamicallypositionedvesselsthatcanlaypipeingreaterthan3,048m(10,000ft)waterdepth.DSND’sreel-layvessel,SkandiNavica,hastherecordinstallationwaterdepthof2,012m(6,600ft).ROVswereavailablefor2,438m(8,000ft)waterdepthbytheyear2000butnowROVscanreachupto3,048m(10,000ft)ofwater.Therecordforthemaximumdeepwaterexplorationdepthhasbeenrenewedyearbyyearasnewtechnologieshavebeenintroduced.3.FlowAssuranceAsthewaterdepthbecomesdeeperandthereservoirislocateddeeperunderneaththeseafloor,oilandgasproductstendtohavehigherpressuresandtemperaturesthanshallowerreservoirproducts.Thehighpressureandhightemperature(HP/HT)productsrequirehighgradeandheavywallvalvesandpipes.Thecrudeproductusuallycontainslargeamountsofwater,wax,andasphalt.Sandalsocanbefoundintheproductandsandwithhighflowvelocitymayerodethepipe’sinternalwallsurface.Dissolvedcarbondioxideandsulfidemayalsocorrodethepipe’sinnerwallsurface.Flowinginalongpipelineincoldseawater,thewaterandwaxcontainingproductmayformanice-likesubstancecalled“hydrate”andthesolidwaxmayadheretothepipeinnerwallsurface.Thehydrateandwaxformationsreducethepipeinsidediameterandmayeventuallyblockthepipeline.Topreventtemperaturedropduringtransportation,thepipelinemaybeinsulatedbymeansofinsulationcoating,oremployahotwatercirculationsystemorelectricalheatingsystem,ordesignedasapipe-in-pipe(PIP)system.Achemicalinhibitorisinjectedintothewelltotreattheproductbeforeflowingintothep...