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Wellheadgasstorage,EtzelGermany

WellheadFromWikipedia,thefreeencyclopedia

Awellheadisthecomponentatthesurfaceofanoilorgaswellthatprovidesthestructuralandpressurecontaininginterfaceforthedrillingandproductionequipment.

Theprimarypurposeofawellheadistoprovidethesuspensionpointandpressuresealsforthecasingstringsthatrunfromthebottomoftheholesectionstothesurfacepressurecontrolequipment.

Whiledrillingtheoilwell,surfacepressurecontrolisprovidedbyablowoutpreventer(BOP).Ifthepressureisnotcontainedduringdrillingoperationsbythecolumnofdrillingfluid,casings,wellhead,andBOP,awellblowoutcouldoccur.

Oncethewellhasbeendrilled,itiscompletedtoprovideaninterfacewiththereservoirrockandatubularconduitforthewellfluids.ThesurfacepressurecontrolisprovidedbyaChristmastree,whichisinstalledontopofthewellhead,withisolationvalvesandchokeequipmenttocontroltheflowofwellfluidsduringproduction.

Wellheadsaretypicallyweldedontothefirststringofcasing,whichhasbeencementedinplaceduringdrillingoperations,toformanintegralstructureofthewell.Inexplorationwellsthatarelaterabandoned,thewellheadmayberecoveredforrefurbishmentandreuse.

Offshore,whereawellheadislocatedontheproductionplatformitiscalledasurfacewellhead,andiflocatedbeneaththewaterthenitisreferredtoasasubseawellheadormudlinewellhead.

Contents

1Components2Functions3Designspecification4Seealso5Externallinks

Components

Theprimarycomponentsofawellheadsystemare:

casingheadcasingspools

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casinghangerspackoffs(isolation)sealsbowlprotectors/wearbushingstestplugsmudlinesuspensionsystemstubingheadstubinghangerstubingheadadapters

Functions

Awellheadservesnumerousfunctions,someofwhichare:

1. Provideameansofcasingsuspension.(Casingisthepermanentlyinstalledpipeusedtolinethewellholeforpressurecontainmentandcollapsepreventionduringthedrillingphase).

2. Providesameansoftubingsuspension.(Tubingisremovablepipeinstalledinthewellthroughwhichwellfluidspass).

3. Providesameansofpressuresealingandisolationbetweencasingatsurfacewhenmanycasingstringsareused.

4. Providespressuremonitoringandpumpingaccesstoannulibetweenthedifferentcasing/tubingstrings.

5. Providesameansofattachingablowoutpreventerduringdrilling.6. ProvidesameansofattachingaChristmastreeforproductionoperations.7. Providesareliablemeansofwellaccess.8. Providesameansofattachingawellpump,

Designspecification

Theoilindustryspecificationsforwellheadsystems(materials,dimensions,testproceduresandpressureratingsetc.)are:

1. API6ASpecificationforWellheadandChristmasTreeEquipment2. ISO10423WellheadandChristmasTreeEquipment

Ingeneralwellheadsarefivenominalratingsofwellheads:2,3,5,10and15(x1000)psiworkingpressure.Theyhaveanoperatingtemperaturerangeof50to+250degreesFahrenheit.Theyareusedinconjunctionwithringtypesealgaskets.

Ingeneraltheyieldstrengthofthematerialsrangefrom36000to75000psi.

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Seealso

PutealWaterwellheadPumpjackAmericanPetroleumInstituteDrillingrig(petroleum)Christmastree(oilwell)

Externallinks

SchlumbergerOilfieldGlossary:wellhead(http://www.glossary.oilfield.slb.com/Display.cfm?Term=wellhead)

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Categories: Oilwells Oilplatforms Petroleumproduction Oilfieldterminology

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