history of offshore drilling units
DESCRIPTION
history of offshore drilling unitsTRANSCRIPT
-
Historyofoffshoredrillingunits
Offshoredrillingbeganin1897,just38yearsafterCol.EdwinDrakedrilledthefirstwellin1859.H.L.WilliamsiscreditedwithdrillingawelloffawoodenpierintheSantaBarbaraChannelinCalifornia.Heusedthepiertosupportalandrignexttoanexistingfield.Fiveyearslater,therewere150offshorewellsinthearea.By1921,steelpierswerebeingusedinRinconandElwood(California)tosupportlandtypedrillingrigs.In1932,asteelpierisland(6090ftwitha25ftairgap)wasbuiltmileoffshorebyasmalloilcompany,IndianPetroleumCorp.,tosupportanotheronshoretyperig.Althoughthewellsweredisappointingandtheislandwasdestroyedin1940byastorm,itwastheforerunnerofthesteeljacketedplatformsoftoday.[1]
Contents
1Overview2Thefirstonwaterdrilling3ThefirstMODU
3.1Thefirstoffshoredrillingunittoimplementsubseawellcontrol4Offshoredrillingunitdesignevolution
4.1Thetenderassistdrilling(TAD)unit4.2Thesemisubmersibleunit4.3Growthofoffshoredrillingunits4.4Firstgeneraltionsemiunits4.5Newergenerationsemiunits4.6Thefixedplatformunits4.7Theshipandbargeshapedunits4.8TechnologicaldevelopmentoftheMODU
5Thefutureofoffshoredrilling6References7Seealso8NoteworthypapersinOnePetro9Externallinks
Overview
In1938,afieldwasdiscoveredoffshoreTexas.Subsequently,a9,000ftwellwasdrilledin1941infashionsimilartotheCaliforniawellsbyuseofawoodenpier.WiththestartofWorldWarII,however,alloffshoredrillingactivitieshalted.AftertheendofWorldWarII,thestateofLouisianaheldanoffshorestatewatersleasesalein1945.Thiswasfollowedin1955bythestateofCalifornia(CunninghamShellAct)leasesale,whichallowedexplorationofoilandgassands.[1]Beforethelatteract,coredrillingcouldbedoneonlyuntilashowofoilandgas.Atthattime,alldrillinghadtostopandthecoreholepluggedwithcement.
Thefirstonwaterdrilling
ThefirstonwaterdrillingwasbornintheswampsofLouisianaintheearly1930swiththeuseofshallowdraftbarges.Thesebargeswererectangularwithanarrowslotintheaftendofthebargeforthewellconductor.Canalswere,andstillare,dredgedsothattugscanmobilizethebargestolocations.Later,bargeswerepostedonalatticesteelstructureabovethebarge,allowingthemtoworkindeeperwaterdepthsbysubmergingthebargeonthebaybottoms.Thesebargesusuallyrequiredpilingsaroundthemtokeepthemfrombeingmovedofflocationbywindsandwaves.Thefirstoffshorewell,definedas,outofsightofland,wasstartedon9September,1947byatenderassistdrilling(TAD)unitownedbyKerrMcGeein15ftofwaterintheGulfofMexico(GOM).AnexWorldWarII26048ftbargeservicedthedrillingequipmentset(DES),whichconsistedofthedrawworks,derrick,andhoistingequipmentlocatedonawoodenpileplatform.[2]
TheBretonRig20(Fig.1),designedbyJohnT.Hayward(whowaswithBarnsdallRefiningCo.atthetime),wasalargepostedsubmersiblebargecreditedin1949withdrillingsomeofthefirstwellsintheopenwatersofLouisiana.ItwasdifferentfromtheKerrMcGeebargeinthatallthedrillingequipmentwasononebarge,anditcouldbetowedasacompleteunit.Theunit,whichwasaconversionfromaninlanddrillingbarge,hadtwostabilitypontoons,oneoneachsideofthebarge,thathydraulicallyjackedupanddownasthebargewassubmergedandpumpedout.Thesepontoonsprovidedthenecessarystabilityforthisoperation.TheBretonRig20,laterknownastheTransworldRig40,wasamajorstepforwardbecauseiteliminatedthecostandtimerequiredtobuildawoodenplatformtosupportallorsomeoftheoffshoretyperig.Althoughitdrilledonlyinpredominantlyprotectedbaysinshallowwater(lessthan20ft),theBretonRig20maybeabletolayaqualifiedclaimasbeingthefirstmobileoffshoredrillingunit(MODU).[3][4]
(/File%3ADevol2_1102final_Page_591_Image_0001.png)
Fig.1BretonRig20,aconvertedpostedswampdrillingbargecapableofdrillinginopenLouisianawaterdepthsupto20ftin1949.Retiredin1962.
ThefirstMODU
ThefirsttrulyoffshoreMODUwastheMr.Charlie,designedandconstructedfromscratchbyOceanDrillingandExplorationCo.(ODECO),headedbyitsinventorandpresident,DocAldenJ.Laborde.TheMr.Charlie(Fig.2)wasapurposebuiltsubmersiblebargebuiltspecificallytofloatonitslowerhulltolocationand,inasequenceoffloodingthesterndown,endeduprestingonthebottomtobegindrillingoperations.WhentheMr.CharliewenttoitsfirstlocationinJune1954,Lifemagazinewroteaboutthe
-
novelnewideatoexploreforoilandgasoffshore.[5]TheMr.Charlie,ratedfor40ftwaterdepth,setthetoneforhowmostMODUswerebuiltintheGulfofMexico(GOM).Usually,aninventorsecuredinvestors,inthiscaseMurphyOil,andthenfoundacustomerwithacontracttodrillfor,inthiscaseShellOil,allowingbankloanstobeobtainedtobuildtheunit.
(/File%3ADevol2_1102final_Page_592_Image_0001.png)
Fig.2Mr.Charlie,thefirstpurposebuilt(June1954)openwaterMODUratedfor40ftwaterdepth.Retiredinlate1986andnowamuseumandtrainingriginMorganCity,Louisiana.
Becausetheshelfdroppedoffquickly,andwaterdepthsincreasedrapidlyofftheshoreofCalifornia,theapproachtherewasentirelydifferentfromthatintheGOM.RigswereinstalledonsurplusWorldWarIIshiphullsmodifiedtodrillinafloatingpositioncomparedwithsittingasubmersiblebargeontheoceanbottom,asdoneintheGOM.Oilcompaniesformedpartnershipsorproceededindependently,butMODUswerenotdesignedandconstructedbycontractdrillingcompaniesinCalifornia.Alldesignandconstructionwasdoneinahighlysecretivemannerwithlittlesharingofknowledge,becausetechnologywasthoughttogiveanedgeinbiddingforstateoilandgasleases.Beforetheleasingofoilandgasrightsin1955,oilcompaniescoredwithsmallrigscantileveredoverthesidemidshipofoldWorldWarIIbarges.Thesebargesdidnothavewellcontrolequipmentortheabilitytorunacasingprogram.Theycouldonlydrilltoadesignatedcoredepthwiththeunderstandingthatiftheydrilledintoanyoiland/orgassands,theywouldstop,setacementplug,andpulloutofthecorehole.Thesecorevesselswerehighlysusceptibletowaveaction,resultinginsignificantroll,heave,andpitch,whichmadethemdifficulttooperate.
Thefirstoffshoredrillingunittoimplementsubseawellcontrol
WithleasingfromthestateofCaliforniatoexploreandproduceoilandgas,wellcontrolandtheabilitytorunmultiplestringsofcasingbecamemandatoryandrequiredatotallynew,unproventechnology.ThefirstfloatingdrillingrigtousesubseawellcontrolwastheWesternExplorer(Fig.3)ownedbyChevron,whichspuddeditsfirstwellin1955intheSantaBarbaraChannel.Othersfollowedquickly,withallofthemconcernedaboutthemarineenvironmentandtechnologytoallowdrillinginroughweather.In1956,theCUSS1wasbuiltfromanotherWorldWarIIbarge.Theunit,builtbytheCUSSgroup(Continental,Union,Shell,andSuperiorOil),was260ftlongandhada48ftbeam.TheCUSSgroupeventuallyevolvedintowhatisnowGlobalSantaFe.
(/File%3ADevol2_1102final_Page_593_Image_0001.png)
Fig.3WesternExplorer,thefirst(1955)floatingoilandgasdrillingMODUthatusedsubseawellcontrol.Retiredin1972.
Theoriginaldesignershadnoexamplesorexperiencestogoby,sonoveltyandinnovationwerethecourseoftheday:
TorqueconvertersonthedrawworkswereusedasheavemotioncompensatorsRotariesweregimbaledtocompensateforrollandpitchThederrickwasplacedatmidshipoveraholeinthevesselcalledamoonpool.Blowoutpreventers(BOPs)wererunoncasingtotheseafloorReentryintothewellwasthroughafunnelabovearotatinghead(riserlessdrillingisnotnewMudpitswereplacedinthehullwithmudpumpsLivingquarterswereadded
Itwasanexcitingandamazingtime,consideringthateveryonewasstartingwithablanksheetofpaper.
Fig.4showstheHumbleSM1drillingbarge(2043413ft)builtandownedbyHumbleOilandRefiningCo.(nowExxonMobil)in1957.Fig.5showsthesubseaequipmentusedtodrillthewells.Notethatithasnomarineriser.TheHumbleSM1drilled65wellsforatotalcostof$11.74/ft,aboutdoublethecostoflanddrillingatthetime,inanaveragewaterdepthof159ftandwithamaximumwelldepthof5,000ft.Theunitaveraged8.93daysperwellanddrilledanaverageof324ft/D.Unfortunately,theunitsankinastormin1961whileonloantoanotheroperator.[6]Attheinsistenceofinsuranceunderwriters,theAmericanBureauofShipping(ABS)wroteandimplemented,in1968,thefirstindependentcodes,guidelines,andregulationsconcerningthedesign,construction,andinspectionsofMODUhulls.
-
(/File%3ADevol2_1102final_Page_594_Image_0001.png)
Fig.4HumbleSM1,afloatingMODUdesignedandoperatedbyHumbleOil&RefiningCo.(nowExxonMobil)in1957.Oneofanumberoftopsecretdrillingunitsofthemid1950s.CourtesyofExxonMobilDevelopmentCo.
(/File%3ADevol2_1102final_Page_595_Image_0001.png)
Fig.5HumbleOilandRefiningCo.sHumbleSM1subseadrillingsystemusedoffshoreCalifornia.CourtesyExxonMobilDevelopmentCo.
Offshoredrillingunitdesignevolution
WiththeMr.Charlie(bottomfounded)andWesternExplorer(floating)asthefirstMODUs,anotherconceptforaMODUshowedupintheformofajackup(/Jackups).Thistypeofunitfloatedtolocationonahullwithmultiplelegsstickingoutunderthehull.Onceonlocation,thelegswereelectricallyorhydraulicallyjackeddowntotheoceanbottom,andthenthehullwasjackedupoutofthewater.Withthisapproach,astableplatformwasavailablefromwhichtodrill.InWorldWarII,theDeLongspudcanjackswereinstalledonbargesforconstructionand/ordocks.TheDeLongtyperigs(Fig.6)showsanexample,theGusI)werethefirstjackupsbuiltin1954.[7]Althoughjackupsinitiallyweredesignedwith6to8legsandthenafewwith4legs,thevastmajorityofunitstodayhave3legs.TheGusIwasconstructedwithindependentlegs.TheLeTourneauCo.builtforZapataCorp.thefirstlatticelegjackup,theScorpion(Fig.7),whichhadindependentlegswithspudcans.Tothisday,LeTourneaucontinuestospecializeinlatticelegtypejackupMODUs.
(/File%3ADevol2_1102final_Page_596_Image_0001.png)
Fig.6WithaDeLongtypejackingsystem,theGusI,builtin1954andratedfor100ftwaterdepth,wastheforerunnerofthemodernjackup.Initially,twobargesthatwereeventuallyjoinedpermanently,buttheunitwaslostinastorm.
(/File%3ADevol2_1102final_Page_597_Image_0001.png)
Fig.7LeTourneausScorpionbuiltforZapata(nowDiamondOffshoreDrillingInc.)in1956for80ftwaterdepthasanindependentlegjackup.Lostin1969.
Amajorevolutionforthejackupdesignwastheintroductionofthecantilevereddrillfloorsubstructure(Fig.8)inthelate1970sandearly1980s.Asfixedplatformsgotbigger,theslotjackupscouldnotswalloworsurroundtheplatformwithitsslotcontainingthedrillingequipmenthowever,thecantileverunitscouldskidthecantileveroutovertheplatformafterjackingupnexttoit.Beforethecantileveredsubstructure,alljackupshadslots,usually50ft.square,locatedintheaftendofthehull.Duringtows,thesubstructurewasskiddedtothemetacenterofthehull,butduringdrillingoperations,thesubstructurewasskiddedaftovertheslot.Thederrickand/orcrowncouldbeskiddedport/starboardtoreachwellsoffcenterjustliketodaysunitsdo.
Thewaterdepthrangeformostoftheearlyslotandcantileverdesignswasfrom150tojustover300ft.Cantileverdrillfloorcentershadareachof40to45ftaftoftheafthulltransom.variabledeckload(VDL)(/MODU_equipment_and_capabilities)ratingswere3,500to5,000kips.
Inthelate1990s,premiumorenhancedjackupsweredesignedandbuilt:
Theycouldcarrymuchlargerdeckloads(7,000kips)Theycoulddrillindeepwaterdepths(400ft)Theyhadmorecapabledrillingmachinery(7,500psihighpressuremudsystemsand750tonhoistingequipment)Theyhadextendedcantileverreach(atleast70ft.)Theyhadlargercantileverloadratingsofdoubleormoretheearlierunits(some>2,500,000lbm)
-
(/File%3ADevol2_1102final_Page_598_Image_0001.png)
Fig.8LeTourneaus116Ccantileveredjackupwithdrillfloorcantileveredoverafixedplatform.Today'sworkhorsedesignofjackups.CourtesyLeTourneau,Inc.
Thetenderassistdrilling(TAD)unit
TheTAD(/Tender_assist_drilling_(TAD)_units)conceptwasusedtodrillthefirstoffshoreoutofsightoflandwellintheworld.Initiallyusedasanexplorationmethod,ithasevolvedintoadevelopmenttool.Thefirsttenderswereshapedlikebarges,butsomearenowshapedlikeshipsforbettermobilizationspeeds.
Basically,theDES(DrillingEquipmentSet)consistsofthederrick,hoistingequipment,BOPs,andsomemudcleaningequipment,reducingtherequiredspaceandweighttobeplacedonthefixedplatform.Therestoftherigislocatedonthetenderhullmoorednexttothefixedplatform,including:
MudpitsMudpumpsPowergeneratorsTubularsandcasingstorageBulkstorageAccommodationsFuelDrillwater
Thisapproachturnedouttobeaverycosteffectivewaytodrillfromsmallfixedplatforms.Unfortunately,inmildandespeciallysevereweather,themooringlinescouldfail,withthehullfloatingaway,asitoftendidinaGOMnorther.Today,mostTADsoperateinbenignorcalmenvironmentsintheFarEastandWestAfrica.
Thesemisubmersibleunit
In1992,thefirstsemisubmersible(semi)(/Semisubmersibles)SeahawkTAD(Fig.9)wasconvertedfromanoldsemiMODU.Thesemihullofferssuperiorstationkeepingandvesselmotionscomparedwithshiporbargeshapedhulls:
Inasemihull,thewavetraincanmovethroughthetransparenthullwithoutexcitingittoheave,roll,andpitch,unlikeamonohullThelowerhullofthesemiisbelowthewateratadeeperdraft.ThecolumnsofferareducedareatoexcitethehullTheworkplatformormaindeckisaboveallwaveaction
TADsareseeingnewuseondeepwaterproductionplatforms,suchasspars,tensionlegplatforms(TLPs)(/Fixed_platform_rigs),anddeepwaterfixedplatforms,whichoperatebeyondjackupwaterdepths.
(/File%3ADevol2_1102final_Page_599_Image_0001.png)
Fig.9Worldsfirstpurposebuilt(conversion)semiTADunitSeahawk.Convertedin1992fromasemiMODU.CourtesyAtwoodOceanics.
Growthofoffshoredrillingunits
Thingswereoffandrunninginthe1950s,withnumerousoperatorsgettingintotherigownershipandoperationbusinessandnewdrillingcontractorsbeingformedeveryyear.Intheearly1960s,ShellOilsawtheneedtohaveamoremotionfreefloatingdrillingplatforminthedeeper,stormierwatersoftheGOM.ShellnoticedthatsubmersiblesliketheMr.Charlie,nownumberingalmost30units,wereverymotionfreeafloatcomparedwithmonohulls.Theideawastoputanchorsonasubmersible,usesomeoftheCaliforniatechnologyforsubseaequipment,andconvertasubmersibletowhatisnowknownasasemisubmersibleorsemi.Thus,in1961,thesubmersibleBluewaterI(Fig.10)wasconvertedtoasemiamidmuchtechnologicalsecrecy.Infact,inthemid1960s,ShellOilofferedtheindustrythetechnologyinaschoolpricedatU.S.$100,000perparticipantandhadlotsoftakers.
-
(/File%3ADevol2_1102final_Page_600_Image_0001.png)
Fig.10WorldsfirstsemiMODU,BluewaterNo.1,convertedin1961/1962byShellOilfromasubmersiblehull.Lostin1964.
ThencametheOceanDriller,thefirstsemibuiltfromthekeelup(Fig.11).TheOceanDriller,designedandownedbyODECO,wenttoworkforTexacoin1963,withthemooringandsubseaequipmentownedbytheoperator,aswascommoninthe1960s.Theunitwasdesignedforapproximately300ft.ofwaterdepth,withthemodeltestsofthehulldoneinDocLabordesswimmingpool.TheOceanDrillercouldalsositonbottomandactasasubmersible,whichitdidwellintothe1980s.
(/File%3ADevol2_1102final_Page_601_Image_0001.png)
Fig.11Worldsfirstpurposebuilt(1963)semiMODU,OceanDriller.Unitcouldoperateasasemiorsubmersible.Retiredin1992andscrapped.CourtesyODECO(nowDiamondOffshoreInc.).
Firstgeneraltionsemiunits
Mostofthefirstgenerationunitscouldsitonbottomordrillfromthefloatingpositionasahedgeagainstunemployment.Theshapeandsizeofthefirstsemisvariedwidelyasdesignersstrivedtooptimizevesselmotioncharacteristics,riglayout,structuralcharacteristics,VDL,andotherconsiderations.Thegenerationdesignationofsemisisaveryloosecombinationofwhentheunitwasbuiltorsignificantlyupgraded,thewaterdepthrating,andthegeneraloveralldrillingcapability.
Newergenerationsemiunits
Intheearly1970s,anew,secondgenerationsemiwasdesignedandbuiltwithnewer,moresophisticatedmooringandsubseaequipment.Thisdesigngenerallywasdesignedfor600ftwaterdepth,withsomeextendingtogreaterthan1,000ft.TheOceanVictoryclass(Fig.12)wastypicaloftheunitsofthisera,whichconcentratedheavilyonreducingmotionsoftheplatformcomparedwithincreasedupperdeckVDLrating.Manywerebuilt,and,inthemiddletolate1980s,anumberofthirdgenerationsemisweredesignedandbuiltthatcouldmoorandoperateingreaterthan3,000ftofwaterdepthandmoresevereenvironments.Manyofthethirdgenerationunitswereupgradedinthe1990stoevendeeperwaterdepthratingswithmorecapabilitiesandbecamefourthgenerationunits.Withafewexceptions,theoperatingdisplacementoftheseunitswentfrom18,000longtonsinthe1970stomorethan40,000longtonsinthe1980s.
(/File%3ADevol2_1102final_Page_602_Image_0001.png)
Fig.12ODECOsmulticolumnsecondgenerationsemiOceanVictoryclassofearly1970s.UnitshownistheOceanVoyager,drillingintheNorthSeaintheearly1970s.Thisdesignprovedstructurallyveryattractiveforupgradetofourthandfifthgenerationunits(seeFig.14.14).
Inthelate1990s,thefifthgenerationunits,suchastheDeepwaterNautilusshowninFig.13,becameevenlarger(>50,000longtondisplacement)andmorecapable.Theseunitscanoperateinextremelyharshenvironmentsandingreaterthan5,000ftwaterdepth.Somesecondandthirdgenerationsemishavebeenconverted,givenlifeextensionstotheirhullsandupgradestotheirdrillingequipmentsoastobeclassedasfourthgenerationunits.Fig.14showsasecondgenerationOceanVictoryclassunit(seeFig.12)
-
thatwascompletelyupgradedtoafifthgenerationunitcapableofmooringandoperatingin7,000ftwaterdepth.NotetheadditionofcolumnblistersforincreasedVDL,50%increaseindeckspace,andtheadditionofriserstorageandhandling.Alimitednumberofthird,fourth,andfifthgenerationsemishavedynamicpositioning(DP)assistorfullDPstationkeepingcomparedwithaspreadmooringsystem.
(/File%3ADevol2_1102final_Page_603_Image_0001.png)
Fig.13DeepwaterNautilus,oneofthenewlybuiltfifthgenerationultradeepwatersemisthathasDPassistforitsspreadmooringsystem.NotespreadcolumnsforincreasedVDLandstability.CourtesyTransoceanInc.
(/File%3ADevol2_1102final_Page_604_Image_0001.png)
Fig.14OceanBaroness,oneoftheOceanVictoryclass(Fig.12)secondgenerationsemisupgradedtoafifthgenerationunit.Noteblisteradditionstocolumn,deckexpansion,andmuchlargerderrick.ThissemialsodidsurfaceBOPworkinMalaysiain2003,alongwithsettingtheworldsrecordselfcontainedspreadmooringwaterdepth(6,152ft).CourtesyDiamondOffshoreDrillingInc.
Thefixedplatformunits
Fiftyyearsago,fixedplatforms(/Fixed_platform_rigs)hadlandrigsplacedonthemtodrillandcompletewells.Todaysplatformrigshavebeenrepackagedsothatthey:
Optimizetherigup/loadouttimeRequirelessspaceArelighterHavemoredrillingcapabilities
Drillingplatformrigsarestillcommon,buttodaysunitslookfardifferentfromthoseof30or40yearsago.Conventionalplatformrigsareusuallyloadedoutwithaderrickbarge.Somelargeplatformsmayhavetwodrillingunitsonthem.
Toeliminatethecostlyderrickbarge,selferectingmodularrigshavebeenbuiltforlightworkoversandfordrillingtomoderatedepths.Largerunitsthathavethecapabilityofa1millionlbmhookloadhavebeenbuiltthatarelightweight,easiertorigup/loadout,andselferecting.TheadventofsparsandTLPsindeepwater,wherespaceanddeckloadarecritical,hasgeneratedevenamoresophisticatedmodulardeepwaterplatformrig,whichishighlyspecializedtothestructureonwhichitsits(Fig.15).Theseplatformrigs:
ArenotselferectingAreuniquetothestructuretheyareplacedonAregenerallyverylightUsuallyhavelimiteddrillingequipmentcapabilities
(/File%3ADevol2_1102final_Page_605_Image_0001.png)
Fig.15Exampleofhighlyspecializedandsitespecificmodularfixedplatformrigsusedonspars,deepwaterfixedplatforms,andTLPs.ThisunitisonaTLPintheGOM.CourtesyHelmerich&PayneIntl.DrillingCo.
Bythemid1960s,thejackupdesignedrigsweredisplacingsubmersiblesinincreasingnumbers.Jackupshadmorewaterdepthcapabilitythaneventhelargestsubmersibles(somecouldoperatein175ftwaterdepth),[7]andtheydidnotslideofflocationinsevereweather.Fromthispointon,jackupandsemidesignswererefinedandmadelargerandmorecapablefromadrillingandenvironmentalstandpoint.
Theshipandbargeshapedunits
ShipandbargeshapedfloatingMODUs(/Conventional_ship_and_bargeshaped_rigs),initiallyattractivebecauseoftheirtransitspeedandeaseinmobilizations,decreasedinnumberassemisandjackupsbecamemorepopular.OneexceptionwastheDPdrillship,whichheldlocationoverthewellborebyuseofthrustersandmainscrewpropulsionratherthanaspreadmooringsystem.
Thefirstunitdevelopedinthemid1960s,althoughnotanoilandgasexplorationunit,wastheGlomarChallenger,whichwasdesignedandownedbyGlobalMarine(nowGlobalSantaFe),andcontractedbytheNationalScienceFoundationfordeepseacoringaroundtheworld.ThisvesselconfirmedthetheoryofshiftingcontinentalplatesFollowingtheGlomarChallengerinthelate1960stoearly1970swereanumberoffirstgenerationDPoilandgasdrillships,suchastheSedco445Subsequently,inthemiddletolate1970s,thesecondgenerationDPunitsweredeveloped,suchastheBenOceanLancer.TheBenOceanLancerwasanIHCHolland
-
Dutchdesign,whichalsoincludedtheFrenchrigsPelerinandPelican,whichwereownedbytheFrenchcompanyForamer(nowPride).Theseunitscoulddrillinupto2,000to3,000ftwaterdepth,hadbetterstationkeepingabilityinmoderatemetoceanconditions,andhadbetteroveralldrillingcapabilitiesDPshipsofthelate1990sandearly2000scanoperateingreaterthan10,000ftwaterdepthandaretwotothreetimeslargerthantheearlierDPships,withextremelycomplexstationkeepinganddualactivitydrillingsystems
Dualdrillingconsistsbasicallyofsomedegreeoftwocompletederricksanddrillingsystemsononehull,sothatsimultaneousoperations,suchasrunningcasingwhiledrillingwiththeotherderrick,canbeperformed.Theseunitsareveryexpensivetobuildandoperate,butcanovercometheircostwithsupposedlyhigherefficiency.Theyshouldbereviewedforpossibleuse,undertherightconditions,asanalternativetostandardsingleoperationunits.Examplesofsuchconditionsinclude:
BatchdrillingasubseatemplateLargedevelopmentprojectsoveratemplateDeepwatershortwellsWellsituationsinwhichmorethanoneoperationcanbenefittheoverallplan
TechnologicaldevelopmentoftheMODU
Theoffshoredrillingindustryhashadspurtsofconstructionanddesignimprovementsoverits50yearhistory.ThefirstwastheconceptionoftheMODUsinthemid1950s,followedbyamildbuildingperiodinthemid1960s.Intheearly1970s,thereweresignificantnumbersofjackupsandsemisubmersiblesbuilt.However,themajorboomofthelate1970sandearly1980shasbeenunmatchedinnumbersofrigsbuilt.Startinginthelate1980s,anumberofdrillingcontractorsupgradedrigsbuiltinthe1970sandearly1980stodeepwaterdepths,moresevereenvironmentalratings,andbetterdrillingabilitiesratherthanbuildingnewunits.Theconceptwasthatdeliveryandcostcouldbecutinhalfcomparedwithanewbuild.Somedrillingcontractorshavesuccessfullybuilttheirentirebusinessplanaroundconversioninsteadofnewbuild.
Sincetheoilandgasbustofthemid1980s,therehasonlybeenonespurtofnewbuilding,andthatwasinthelate1990s.Mergersandbuyoutsofdrillingcontractorsandrigsdominatedtheindustryfromthemid1980stothemid1990s.Onedrillingcontractor,GlobalSantaFe,monthlypublishesapercentagenumberrelatedtodayrateandcostofbuildinganewunit.A100%ratingmeansnewunitscanbebuiltprofitablyhowever,thepercentagenumberhaslingeredinthe40to60%rangeoverthelast15yearsorso,withspurtsinto80%.Byitsnature,thedrillingbusinessisbuiltonoptimismforthefuturethatmaynotalwaysshowproperreturnsoninvestmentintermsofnewbuildsorconversions.Highonhopeandthefuture,thecontractdrillingbusinesshashistoricallynotbeenconservativeandhasnotfollowedgenerallyacceptedrulesofinvestment.
Intheearly2000s,theaverageageofthefleetwasmorethan20years,withsomeunitsmorethan30yearsold.Fewarelessthan5yearsold.Somehavebeenupgradedandhavehadlifeextensions,whichmeansthat,withgoodcareandmaintenance,thebasichull,ifitand/ortherigarenotrenderedtechnologicallyobsolete,maylastmorethan40years,asdounitsinthedredgingbusiness.
Technologicallyobsoletemeansthattheunitneedstohave:
1.Uptodatefeaturessuchas:
Topdrive,Mudsolidscontrol,Pipehandlingequipment,etc
2.Enoughpowertorunallthenewequipment
Thefleetin2003stoodatapproximately390jackups,170semis,30ships,and7submersibles.Fixedplatformrigsnumberabout50,andTADsnumberabout25.
Thefutureofoffshoredrilling
Theconsensusisthattheoffshoredrillingbusinesswillcontinuetogrow,withemphasisontechnicalbreakthroughstoreducedrillingcosts.Theindustryhasdemonstratedthatitcandrillinwaterdepthsuptoandmorethan10,000ft.,andcanoperateinthemostsevereenvironments,butallataveryhighcostthatcanrunintohundredsofthousandsofdollarsperday.Ultradeepwaterwellscostingmorethan$50millionarecommon,andsomewellshavecostmorethan$100million.Itisverydifficulttojustifywellsthatcostthismuchgiventherisksinvolvedindrillingtheunknown.Thechallengetotheoffshoreindustryistodrillsafelyandeconomically,whichmeanstechnologyofeconomics,withsafety,environment,security,andpersonnelhealthallplayingalargerole.
References
1. 1.01.1Silcox,W.H.,etal.1987.OffshoreOperations.InPetroleumEngineeringHandbook,secondedition.Richardson,Texas:SPE,Chapter18.2. Barnes,K.B.,andMcCaslin,L.S.Jr.1948.GulfofMexicoDiscovery.Oil&GasJ47(March18):96.3. MobileRigRegister,eighthedition.2002.Houston,Texas:ODSPetrodata.4. Howe,R.J.1966.TheEvolutionofOffshoreMobileDrillingUnits.DrillingandProductionPractice.API66120(http://www.onepetro.org/mslib/app/Preview.do?
paperNumber=API66120&societyCode=API).5. Laborde,A.J.1997.MyLifeandTimes.NewOrleans,Louisiana:LabordePrintCompany.6. Harris,L.M.1957.HumbleSM1OffshoreExplorationVessel,PetroleumEngineeringProjectReport.LosAngeles,California:HumbleOilandRefiningCo.,
ProductionDepartmentCaliforniaArea.7. 7.07.1Howe,R.J.1986.EvolutionofOffshoreDrillingandProductionTechnology.PresentedattheOffshoreTechnologyConference,Houston,Texas,58May.OTC
5354MS.http://dx.doi.org/10.4043/5354MS(http://dx.doi.org/10.4043/5354MS).
Seealso
PEH:OffshoreDrillingUnits(/PEH%3AOffshore_Drilling_Units)
Tenderassistdrilling(TAD)units(/Tender_assist_drilling_(TAD)_units)
Semisubmersibles(/Semisubmersibles)
NoteworthypapersinOnePetro
T.F.MarucciandD.E.McDaniel1970.SafetyofMobileOffshoreDrillingUnits,OffshoreTechnologyConference,2224April.1321MS.http://dx.doi.org/10.4043/1321MS(http://dx.doi.org/10.4043/1321MS)
Externallinks
AmericanBureauofShipping(ABS)(http://www.eagle.org/)
-
(https://www.onepetro.org/search?q=Historyofoffshoredrillingunits) (http://scholar.google.ca/scholar?q=Historyofoffshoredrillingunits)
(http://www.worldcat.org/search?q=Historyofoffshoredrillingunits) (http://wiki.seg.org/index.php?
title=Special%3ASearch&redirs=1&fulltext=Search&ns0=1&ns4=1&ns500=1&redirs=1&title=Special%3ASearch&advanced=1&fulltext=Advanced+search&search=History
ofoffshoredrillingunits) (http://wiki.aapg.org/index.php?
title=Special%3ASearch&profile=advanced&fulltext=Search&ns0=1&ns4=1&ns102=1&ns104=1&ns106=1&ns108=1&ns420=1&ns828=1&redirs=1&profile=advanced&search=Historyofoffshoredrillingunits)