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1、1DrillingCostandHoleProblems1.5-121.5-2TheDrillingCostEquation:Cf=drillingcost,$/ftCb=costofbit,$/bitCr=fixedoperatingcostofrig,$/hrtb=totalrotatingtime,hrstc=totalnon-rotatingtime,hrstt=triptime(roundtrip),hrs=footagedrilledwithbit,ftEq.1.1631.5-3DrillingCosts
2、Tendtoincreaseexponentiallywithdepth.Thus,whencurve-fittingdrillingcostdata,itisoftenconvenienttoassumearelationshipbetweentotalwellcost,C,anddepth,D,givenbyC=aebD…………………..(1.17)4Fig.1-65.Least-squarecurvefitof1978completedwellcostsforwellsbelow7,500ftinthesout
3、hLouisianaarea.1.5-451.5-5DrillingTimecont’dPlottingdepthvs.drillingtimefrompastdrillingoperations:A.AllowsmoreaccuratepredictionoftimeandcostfordrillinganewwellB.Isusedinevaluatingnewdrillingprocedures(designedtoreducedrillingtimetoagivendepth).61.5-6BitWeight
4、andRotarySpeedIncreasingbitweightandrotaryspeedboostsdrillingrateTheseincreasesacceleratebitwearFieldtestsshowthatdrillingrateincreasesmoreorlessindirectproportiontobitweight7Consider10”hole(don’toverdo!!)DrillingRate,ft/hrBitWeightx1,000lb/in40,000lbf1.5-78Dri
5、llingRate,ft/hrRotarySpeed,RPMDon’toverdo!Casingwear,bitlife...1.5-89DrillingRate,ft/hrHydrostaticPressure,1,000’sofpsiEFFECTOFBACKPRESSURE0-5,000psi1.5-910Depth,ftRotatingTime,hoursEFFECTOFDRILLINGFLUIDwatervs.air1.5-1011EFFECTOFSOLIDSINTHEMUD1.5-11121.5-12Hol
6、eProblemsLostCirculationStuckPipeKeyseat-CrookedHoleDifferentialStickingMechanicalStickingJunkinHoleKicksandBlowoutsCrookedHole131.5-13HoleProblems-LostCirculationFlowout7、idCharacteristicsInducedFracturingofFormationFromRapidPipeMovementCauses:HighFormationPermeability(e.g.fractures)LowFormationPorePressure1.5-14HoleProblems-LostCirculation15CostlyMudMakeupLossofProductionFireLossofPermittoDrillResults:1.5-15HoleProblems-LostCir
8、culation16PreventiveMeasures:CrewEducationGoodMudProgramStudyWellsinArea…tobeprepared1.5-16HoleProblems-LostCirculation17UseLostCirculationMaterialasMudAdditive(fibrousorgra