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WELLPLANWELLPLAN®TrainingCourse

CriticalSpeed(临界转速)Part#WELLPLANCriticalSpeed

AgendaCriticalSpeed-FundamentalsandMethodologyCriticalSpeed-TheSoftwareApplicationCriticalSpeed-ExercisesWELLPLANAnapplicationtoassistwiththedeterminationofrotatingspeedsthatmayresultindamagingstressesforagivensetofoperatingparameters.(一种应用软件可以确定产生破坏性压力的旋转速度-当一系列的系数被输入时)Atcriticalrotaryspeeds,smallforcedoscillationsatthebit(orotherlocation)resultinlargedisplacementsandstresseselsewhereinthedrillstring.(在临界转速时，钻头(或其他位置)的小力量振幅将会对钻柱产生更大的压力及排量)

CriticalSpeed

Whatisit?WELLPLANDesignBHAtominimizevibrationeffects(设计BHA以减少振动效应)Determineallowableoperatingparameters-WOB,RPM.(确定可运行的系数-WOB，RPM)Couplewithdownholesensorstovalidatemodelandenhancethedatabaseofexcitationfactors.(与井下传感器连合验证模式及改善波动因素)Postanalysistodetermineifvibrationwasacauseoffailure.(分析以确定振动失败的原因之一)CriticalSpeed

PracticalApplicationsWELLPLANDeterminescriticalrotaryspeedofadrillstring (确定钻柱的临界转速)Excitationatbutnotrestrictedtoabit

(不止在钻头上的波动系数)Includeseffectsduetoballooning,contact/friction,finitedisplacement,buoyancy,stressstiffeninganddamping(鼓胀,接触/摩擦力,有限的)(移出，浮力，压力加强和减震)Damping-includeseffectsof(减震-包括以下效应)interactionwiththeformation...(与岩层互相影响)drillingfluideffect,includinginertialeffectsofaccelerationofmudoutsidethedrillstring(钻井液效应，包括加速井环泥浆的流动惯性效应)massdampingproducedbytheBHAstructure(BHA结构所产生的质量减震)CriticalSpeed

FeaturesWELLPLANFirsttheworkstingisdividedinto150elementsasitislyingina3Dwellbore(当钻柱在3D井眼里面时被分为150单元)EachoftheelementsareanalyzedusingFiniteElementAnalysistodeterminetheforcesandmomentsactingontheindividualelements(每个部位都用有限元分析来确定扭矩与其他力量)Next,thestringis“vibrated”usingtheexcitationsspecifiedusingtheExcitationFactor.Excitationfactor(EF)equalsthenumberoftimesperrevolutionthatexcitationoccurs (用波动因素来震动钻柱。EF=多少次数/旋转(当波动发生时))CriticalSpeed

Methodology(方法论)WELLPLANCSAassumesalinearformofmotion

Solvesforarangeofoperatingspeeds

CriticalSpeed

TheoryWELLPLANTriconeBits:(EF)=3,asexpectedfromthethreelobedgeometryPDCBits: (EF)ashighas9-12isused.Lowerfactors areassociatedwithbladepatternsorcutter distribution.Higherfactorsrepresentcomplex behaviorssuchasbackwardwhirl.CriticalSpeed

ExcitationFactorsWELLPLANModelassumescyclicbehaviorofthedrillstring(模式预测钻柱的旋转特性)Transienteffectssuchasimpactforcesarenotmodelled.Theseeffectsmaybesignificanttotheservicelifeofacomponent(并不模拟瞬态反应如冲击力量)Difficulttocharacterizetheprincipalexcitationmechanism(很难去刻画主要的波动结构)Bit(钻头)Stabilizer(稳定器)Massimbalances(质量不平衡)Walk/Whirlmechanism(游动/旋转结构)CriticalSpeed

AnalysisLimitations(分析局限)WELLPLANCriticalSpeedAnalysisInput(输入)BHA,Survey,WellboreandDrillingParametersExcitationloads,RPMrangeandincrementAdditionaluserspecifiedmassanddampingeffects(BHA,测量,井眼，钻井参数，波动负荷,每分钟转数的范围及增加，.使用者输入的质量及减震效果)

Output(输出)CompleteBHAstructuralsolution(完整BHA结构的解决方案)Tabulatedstressanddisplacementresults(压力制表及位移结果)PlotsofstressanddisplacementvsRPMorpositioninBHAataparticularRPM(在策划压力与位移对RPMorBHA的结果)WELLPLANCriticalSpeedAnalysisWELLPLANCriticalSpeedAnalysisWELLPLANCriticalSpeedAnalysisWELLPLANCasestudyPostRunanalysisondrillstringwheresomemechanicaldamagetotheMWDtoolwasexperienced(根据PostRun分析曾经有过MWD工具的损坏。)VerticalBorehole,121/4inPDCbit(DiamantBoartGX2)Claystoneformation165-170RPMat15-30KlbsWOB-producedhighestpeakonvibrationmonitorCSAPredictshighlateralforcespresentat170RPMDown