【7A文】Air Drilling(空气钻井）.ppt

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1、AirDrilling(空气钻井）1HoleCleaning2Equipment3DrillingPractices4Problems5GasType6MistDrillingSection2–Page1“DryairislabeledassuchheretorecognizeitsuseasoneofthemostcommontypesofUBfluids.However,mostoftheinfohereappliestoanygasusedastheUBfluidaswellastoair.”GasB

2、ehaviorWhereTisexpressedindegreesR.P1xV1T1=P2xV2T21ft3ofgas@10,000ftTVDBHP=5200psi2ft3whencirculatedto5000ftUnloadcondition!!LengthofFluidColumn=LengthofGasGasRisinginAnOpenWellboreIftheinjectionrateofN2is900scf/minuteat700Fandaninjectionpressureof600psi.W

3、hatisthevolumeflowrateofthisgasdownholeatconditionsof5200psiandatemperatureof2500F.V2=(14.7x900x710)/(5200x520)=3.47ft3/mAstandardcubicfoothasapressureof14.7psiatatemperatureof600FToconvertFahrenheittoRankinadd460Section2-Page2GasLawHoleCleaningHolecleanin

4、gwithairisacomplicatedsubject.Insimpleterms,theupwardairflowexertsadragforceonthecutting.Ifthedragforceisgreaterthanthegravitationalforce,thecuttingwillmoveupwardandoutofthehole.Cuttingsremovedonmostairdrillingoperationstendtobeveryfine.Theterm“dusting”iso

5、ftenusedtodescribetheremovalprocess.Thebitgeneratescuttingscomparableinsizetooverbalancedrilling;however,theytendtoremainintheholeuntilgrounddowntoasmallenoughsizefortheairflowtoliftfromthewell.Thepressureoftheairincreaseswithdepth,causingthedensityofairto

6、increaseaswell.Theincreasedpressurereducestheairvelocity;however,theincreaseindensityassistswiththecuttingstransport.IncreasedAirVelocityatLessAirPressureLessEffectiveHoleCleaningAsDepthIncreasesDragForceDuetoAirVelocityGravitationalSettlingForceCuttingRes

7、ultingCuttingVelocitySection2-Page3Air/GasInjectionRequirementsAirinjectionrequiredforadequateholecleaningisverydifficulttocalculate.Angel(1957)suggestedthateffectivecuttingstransportisrelatedtothekineticenergyoftheair(gas)strikingthecutting.KE=½Dv2D–densi

8、tyofair(gas)v–annularvelocityofair(ft/sec)Throughtestingandexperimentsonshallowblastdrillingitwasdeterminedthat3000ft/minprovedtobeaneffectiveminimumairvelocityforcuttingstransport.Section2-Page4CuttingCarryi