您好,欢迎访问三七文档
RecentadvancesinoffshoregeotechnicsfordeepwateroilandgasdevelopmentsMarkF.Randolphn,ChristopheGaudin,SusanM.Gourvenec,DavidJ.White,NoelBoylan,MarkJ.CassidyCentreforOffshoreFoundationSystems–M053,UniversityofWesternAustralia,35StirlingHighway,Crawley,Perth,WA6009,AustraliaarticleinfoArticlehistory:Received7July2010Accepted24October2010Availableonline18November2010Keywords:GeotechnicalengineeringOffshoreengineeringInsitutestingShallowfoundationsAnchorsPipelinesSubmarineslidesabstractThepaperpresentsanoverviewofrecentdevelopmentsingeotechnicalanalysisanddesignassociatedwithoilandgasdevelopmentsindeepwater.Typicallytheseabedindeepwatercomprisessoft,lightlyoverconsolidated,finegrainedsediments,whichmustsupportavarietyofinfrastructureplacedontheseabedoranchoredtoit.Aparticularchallengeisoftenthemobilityoftheinfrastructureeitherduringinstallationorduringoperation,andtheconsequentdisturbanceandhealingoftheseabedsoil,leadingtochangesinseabedtopographyandstrength.Novelaspectsofgeotechnicalengineeringforoffshorefacilitiesintheseconditionsarereviewed,including:newequipmentandtechniquestocharacterisetheseabed;yieldfunctionapproachestoevaluatethecapacityofshallowskirtedfoundations;novelanchoringsystemsformooredfloatingfacilities;pipelineandsteelcatenaryriserinteractionwiththeseabed;andsubmarineslidesandtheirimpactoninfrastructure.Exampleresultsfromsophisticatedphysicalandnumericalmodellingarepresented.&2010ElsevierLtd.Allrightsreserved.1.IntroductionTheworld’sescalatingdemandsforenergy,combinedwiththecontinueddepletionofoilandgasreservesinshallowwaters,hasresultedinoffshoredevelopmentsmovingbeyondtheimmediatecontinentalshelfintodeeperwatersanduntestedenvironments.IntheGulfofMexico,WestAfrica,offshoreBrazilandmorerecentlyoffAustralia,developmentshaveproceededintowaterdepthsinexcessof1000m.Thesedeepwaterdevelopmentsusuallyconsistofmooredfloatingfacilities,whicharetetheredtotheseabedviaananchoringsystem.Hydrocarbonsaretransportedtoandfromtheseabedthroughverticalorcatenaryrisersconnectedtoaflowlineorpipelinesystem.Thecomplexsubseainfrastructurecomprisesanintegratednetworkofwells,manifoldsandpipelines,allofwhicharesupportedbyfoundations.1.1.ScientificchallengesThenatureofgeotechnicalfoundationdesignhaschangedradicallyfordevelopmentsindeepwater,comparedtoshallowwater.Thisispartlyduetothetypeofoffshorefacility(floating,orsubsea)andpartlybecauseofthenatureoftheseabedsediments.Thereisreducedemphasisontraditionalfoundationsystemssuchaspilesandlargegravity-basefoundations;instead,anchorsystemsmustbedesignedforfloatingfacilities,sotheanchorsfaceasignificantcomponentofupliftloadfortautandsemi-tautmooringconfigurations.Inresponse,newanchoringsystemshaveevolved,suchassuctioncaissons,plateanchors(eithersuctionembeddedordraggedin)anddynamicallyembeddedtorpedoanchors(whicharesimplydroppedintotheseabed).Geotechnicaldesignisalsoincreasinglyfocusedonpipelineandriserinteractionswiththeseabed,andonthedesignofefficientshallowskirtedfoundationsandmatsforwell-headmanifoldsandpipelineterminationstructures.Majorscientificchallengeswithindeepwatergeotechnicalengineeringincludethefollowing:Characterisingsoilinremotelocations:Deepwatersitesconsisttypicallyofsoftfine-grainedsediments(eitherclay,orinsomeregionscarbonatemudsandsilts)thathavebeendepositedrelativelyslowlyandarecharacterisedbyincreasingstrengthwithdepth.Handlingsamplesofthesesoftsoilsisextremelydifficult,soinsitutestingispreferable,increasinglywithfull-flowpenetrom-eters.Characterisationoftheseabedsedimentsisthereforechal-lenging,particularlyfordesignofpipelines,steelcatenaryrisersandmanifoldswhereonlytheupperoneortwometresareofinterestandstrengthsaregenerallyverylow.Siteinvestigationsmustalsoextendoverawidespatialarea.Anchoringlocationsaretypicallykilometresapartandpipelineroutescanextendforhundredsofkilometres.BP’sGreaterPlutoniodevelopmentoffWestAfrica(in1350mofwater)representsatypicalfieldlayout(Fig.1).Mobileinfrastructure:Traditionalsoilmechanicsisfocusedonensuringthestabilityandserviceabilityofstationaryfoundationsunderworkingloads.However,staticdesignisnotalwaysContentslistsavailableatScienceDirectjournalhomepage::10.1016/j.oceaneng.2010.10.021nCorrespondingauthor.Tel.:+61864883075;fax:+61864881044.E-mailaddress:randolph@civil.uwa.edu.au(M.F.Randolph).OceanEngineering38(2011)818–834applicableindeepwaterapplications:thegeotechnicalinfrastruc-turemaybedesignedtoallowmovement.Examplesincludecontrolledlateralbucklingofpipelines(duetooperationaltem-peratureandpressurechanges),trenchdevelopmentofsteelcatenaryrisers(SCRs)andtheinstallationofdragandplateanchors.Allofthesesituationsinvolvequantifyingthechangingsoilresistanceandkinematicsforstructuralcomponentsmovingdistancesexceedingtheirsize.Changingsoilproperties:Theepisodicnatureofoffshorecyclicloadingcancausesignificantchangesinsoilstrengthandstiffnessofmorethananorderofmagnitudeduetodisturbance,remould-ing,reconsolidationandwaterentrainment.Th
本文标题:Recent advances in offshore geotechnics for deep w
链接地址:https://www.777doc.com/doc-3125798 .html