INTRODUCTIONTODRILLINGBIT鉆頭英文簡(jiǎn)介

1、DRILL BIT SELECTION Oneofthe moreconfusing aspectsofoilwelldrillingtotheyoungand oldalikeisthenumeroustypesofdrillbits.Thelargestmanufacturerofdrillbitsmakes34typesand33sizes(diameters)and manymoreonrequest.IADC organizationhasasystemofassigning adesignationcodetoeach bittype.ROLLERCONESeriesTypeFea

2、tureFeature (2)ROLLERCONEExampleCode: 522 R5=code forinsert bits“2=code forsofttomediumformation“2=code forroller bearingair cooled“R=code forreinforcedweldsFIXEDCUTTERSCuttertypeandbodymaterial,Cross-section profile,Hydraulicdesign,andCuttersizeanddensityFIXEDCUTTERSFirstcode designationsareD -natu

3、raldiamond/matrixbodyM -polycrystallinediamondcutters/matrixbodyS -polycrystalline diamondcutters/steelbodyT -thermally stablepolycrystallinediamondcutters/matrixbodyO -otherSecondcodedesignationsarelong taper/deepconelong taper/mediumconelong taper/shallowornocone(parabolic)mediumtaper/deepconemedi

4、umtaper/medium conemediumtaper/shallowornocone(rounded)shorttaper/deep cone(inverted)shorttaper/mediumconeshorttaper/shallow or no cone(flat)Thirdcode designationsarebladed/changeablejetsbladed/fixedportsbladed/openthroatribbed/changeablejetsribbed/fixedportsribbed/openthroatopen face/changeablejets

5、open face/fixedportsopen face/openthroatalternativecodesradialflowcrossflowotherFourthcodedesignationsarecuttersize;large, medium,and smallcutterdensity;light, medium,heavyExampleCode:M 582M =codeforpolycrystallinediamond cutters/matrix body“5 =codeformediumtaper/mediumcone“8 =codeforfixed ports/ope

6、nface“2= codefor mediumcutter size/lightcutter densityDrillBitCharacteristicsTeethlengthand sizeNumberofteeth(indexing)Cone offsetCone bearingtypeHeel rowteethconfigurationGaugeconfigurationJournal shaft angle (howflatorroundthebottom holepattern)Theteethlength andsize andcone offsetaffectthe ROPThe

7、nextthreeitemsonthelisthave alargeaffect on thebitlife.Item 7affectshole straightness.Rollerconedrillbitcharacteristics of importanceinregard to selectionare:ROCKFAILURE MODELSTworockfailure modelsarerecognized:the tensionandshearIthasbeenarguedthatthesheartypeactionismoreefficientthanthetensionmode

8、l.DRILLBITSELECTION CRITERIAA popularequationfor costcomparisonsisthe total costper footequation.Ifthebit wereoperatedtoits optimallifeatitsoptimumweightand speed,then thecost would be thelowestcostperfootforthe bit.Isthebit lifeifthe bitisterminated byBearing failure,Totaltoothwear,orThereduction o

9、f itsdrillingrate to an uneconomicalone.p.s. Formationchanges often maskthe latteroptimal lifeand caremustbeexercised.OPTIMAL LIFEExampleFollowingperformancedataisgiven:ITEMSTEELTOOTHINSERTTOOTHBitCost$277.88$1521.32Trip6:18hrs/min6:32 hrs/minRotationTime10:01hrs/min58:42 hrs/minDown TimeNoneNoneBit

10、Footage180 ft880.5ftRigCostRate375 $/hrSameFractionToothWear1/2Not ApplicableFractionBearing Wear6/88/8Average Drilling Rate18ft/hr12.5 ft/hrBitSize7-7/8in.7-7/8in.BitWeight30,000lbs40,000lbsRotarySpeed85 rpm60rpmTheplotshowsthat hadthesteeltoothbit beenpulled at itsoptimal life(6hoursand 34 minutes

11、) it would havehad alowercostperfoot:$34.05/ft versus$35.47/ft.Trip times maybetakenfrom theIADC toursheetormay be taken fromthe Geolographunitorsome other device.A chart versusdepthmust be constructed foreach rigforultimateanalyses.TRIP TIMEExampleA bitisrunatadepthof8,000feet andpulledatadepthof8,

12、500feet.Howmanyhoursisthetriptime forthis bit?Trip T=(5.2+5.7)/2=5.45hrFrom thecharta round trips at 8,000 feetand 8,500 feetrequire5.2hoursand 5.7hours,respectively.OPTIMAL WOB& RPMThepurposeofselectingbit weightandrotary duce thelowestdrillingcostperfoot2.control thedirectionofthe

13、drill hole3.find overpressuredzones4.satisfy equipmentlimitations(solids removal,BHA, etc.)5.develop asatisfactory cuttings description logCONTOUR METHODThemethod consists of constructingthepreviousfigure in atwo dimensional presentation.ExampleSixinsert bitshavebeen runandtheirperformanceand total

14、costper footdataarelisted in thetable.BIT#ROT. TIMEFOOTAGETCFHr:Min$/FT158:4273435.28239:0536051.513101:2185548.99462:0761444.24547:1651741.27656:3365838.14TheoptimalWOBand RPMare40,000 lb and50rpm($35.00/ft)ANALYTICAL METHODThesameprocedurecouldbeusedfordeterminingoptimalWOB, andRPMfor thesteeltoot

15、h,roller bearingbit;however,anGalleandWoods analyticalmethod is availableforthesebits.DEFINITION OF TERMSBS=Bitdiameter; inchW=Actualweight on bit;1000poundsW=Equivalent weightona 7-7/8 inchbit;1000 poundsTT=Trip time; hrsR=Cost rateofthe drilling operation;$/hrsT=Time;hrsG=BitCost+ TripCost;$TC=Tri

16、p cost; R*TT;$D=Fractionoftoothheightwornaway;8thsB=Fractionofbearing lifeconsumed; 8thsDT=Down time; hrsRT=Rotationtime;hrsF=Bitfootage;ftGalleandWoodspublished thefollowingrelationshipsforthe rateoftoothwear.TOOTHWEARA=Correlationcoefficientfortoothwearandiscalled theformationabrasiveness factorIn

17、tegrationofthetoothwearequationgivesbitrotationtimeToothwear EquationRotarySpeed, N=80BEARING WEARS=correlationcoefficientcalledthe drilling fluid factorOtherspublished thefollowingrelationship fortherateofbearing wear.RotarySpeed, N=80RATE OF PENETRATIONC=correlationcoefficientcalledthe formationdr

18、illabilityfactorThevalues ofandaredeterminedfrom drill-offtest andrangebetween.p=1.0ifflat tooth wear(non-sharpening)p=0.5ifself sharpeningBitfootage(F)isequaltoRateofPenetrationxRotationTimeEquationofROPSofar, RT is determinedeither by settingD=1(complete bittoothwear)orB=1(complete bearin

19、gwear)Whichevercomesfirst.DRTFDRTFDRTFDRTFDRTFDRTFDRTFRotarySpeed, N=80ThetotalcostperfootequationisDRTFTCFDRTFTCFDRTFTCFDRTFTCFDRTFTCFDRTFTCFRotarySpeed, N=80TheparametersA,C &Sareusuallycomputedwith datagatheredfromothersimilar drill bitswhichwereruninsimilarformations,atsimilar depths,withsimilar bottomhole assemblies, withsimilarhydraulics,with simil