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8/4/2019 Federal Government Issues Report on Causes of BP Oil Spill
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THEBUREAUOFOCEANENERGYMANAGEMENT,
REGULATIONANDENFORCEMENT
REPORTREGARDINGTHECAUSESOFTHEAPRIL20,2010
MACONDOWELLBLOWOUT
September14,2011
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i
TABLEOFCONTENTS
ExecutiveSummary................................................................................................1
I. Introduction ..................................................................................................... 10
A. TheInvestigation ......................................................................................... 10
B. BackgroundRegardingDeepwaterDrillingintheGulfofMexico ............ 13
C. CompaniesInvolvedintheMacondoWell .................................................. 16
D. TheDeepwaterHorizon ............................................................................... 18
E. TheMacondoWell ....................................................................................... 19
F. TheBlowout ................................................................................................. 23
II. WellDesign...................................................................................................... 25
A. CostoftheMacondoWell ............................................................................ 25
B. DrillingMargin........................................................................................... 27
C. CasingProgram ........................................................................................... 31
D. MudProgramandType .............................................................................. 32
E. MudLosses .................................................................................................. 33
F. WellBallooning ........................................................................................... 34
G. PlannedandActualTotalDepth ................................................................. 34
H. DesigningtheProductionCasingLongStringversusLiner................... 36
III. Cementing ........................................................................................................ 40
A. CementingProcess....................................................................................... 40
B. CementDesignandModeling ..................................................................... 41
C. GasFlowPotential....................................................................................... 46
D. Centralizers .................................................................................................. 47E. FloatCollar .................................................................................................. 49
F. CementingtheMacondoProductionCasing .............................................. 53
G. IndustryStandardsforCementing.............................................................. 57
IV. PossibleFlowPaths ........................................................................................ 61
V. ConclusionsonWellDesign,Cementing,andFlowPath ........................ 68
A. CauseoftheFailureoftheCementBarrier.................................................. 68
B. ContributingCausesoftheCementBarrierFailure ................................... 68
C. PossibleContributingCausesoftheCementBarrierFailure ..................... 70
D. FlowPathCause .......................................................................................... 73
VI. ChallengesattheMacondoWell .................................................................. 75
A. KicksandStuckDrillPipe .......................................................................... 75
B. SchedulingConflictsandCostOverruns .................................................... 78
C. PersonnelChangesandConflicts ................................................................ 79
D. SafetyStanddown....................................................................................... 83
VII. TemporaryAbandonmentoftheMacondoWell ....................................... 85
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ii
A. InstallingtheLockDownSleeve ................................................................. 85
B. SettingtheCementPlug.............................................................................. 86
C. TheUseofLostCirculationMaterialasSpacer .......................................... 87
D. WellIntegrityTesting ................................................................................. 88
VIII. KickDetectionandRigResponse................................................................. 98
A. KickDetectionMethodsandResponsibilities.............................................. 98
B. MultipleSimultaneousOperationsThatHamperedtheCrewsAbilityto
DetectKicks ................................................................................................. 99
C. RigFloorResponse .................................................................................... 103
D. TheUseoftheMudGasSeparator ............................................................ 104
E. ActivityontheBridge................................................................................ 106
F. EmergencyDisconnectSystem.................................................................. 107
IX. ConclusionsonTemporaryAbandonment,KickDetection,andthe
EmergencyResponse................................................................................... 109
A. KickDetectionandResponseFailureCause ............................................. 109B. KickDetectionFailureContributingCauses ............................................ 109
C. KickDetectionFailurePossibleContributingCauses .............................. 110
D. ResponseFailureContributingCauses ..................................................... 112
E. ResponseFailurePossibleContributingCauses ....................................... 113
X. IgnitionSource(s)andExplosions .............................................................. 115
A. MainEnginesandEngineSwitchGearRooms ........................................ 115
B. MudGasSeparator .................................................................................... 119
C. OtherPossibleIgnitionSources ................................................................ 122
XI. Conclusionson
Ignition
Source
and
Explosion........................................ 125A. IgnitionSources ......................................................................................... 125
B. ContributingCausesoftheExplosion ....................................................... 125
C. PossibleContributingCausesoftheExplosion ......................................... 126
D. OtherPossibleIgnitionSources ................................................................ 127
XII. TheDeepwaterHorizonBOPStack............................................................... 129
A. DesignandConfiguration ......................................................................... 129
B. ControlandPowerSystems....................................................................... 132
C. EmergencyDisconnectSystem.................................................................. 133
D. AutomaticModeFunction(Deadman) ................................................. 134
E. AutoshearFunction ................................................................................... 134
F. ForensicExaminationoftheBOP ............................................................. 135
G. ExaminationMethodsUsedbyDNV........................................................ 137
H. DNVsForensicExaminationFindings .................................................... 138
I. EvaluationofOtherPossibleFailures ....................................................... 142
J. StudiesEvaluatingtheReliabilityofBOPs .............................................. 144
K. MaintenanceoftheDeepwaterHorizonBOP ........................................... 146
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L. BOPSystemLeaks ..................................................................................... 151
M. ROVInterventions .................................................................................... 153
XIII. BOPStackConclusions ................................................................................ 155
A. CauseoftheBOPStackFailure................................................................. 155
B. BOPStackFailureContributingCauses .................................................. 155
C. BOPStackFailurePossibleContributingCauses..................................... 155
XIV. RegulatoryFindings ..................................................................................... 157
A. PermittingProcess..................................................................................... 158
B. WellActivityReports ................................................................................ 161
C. MacondoDeparturesandAlternativeProcedures .................................... 161
D. MMSDrillingInspections ........................................................................ 162
E. PotentialIncidentofNoncomplianceGuidelines ...................................... 162
F. InspectionForms........................................................................................ 164
G. MMSDeepwaterHorizonInspectionsatMC252 ................................... 164
H. SafeDrillingMargin ................................................................................. 165I. WellControl............................................................................................... 165
J. SubseaBOPRegulatoryRequirements ..................................................... 167
K. RegulatoryImprovements ......................................................................... 172
L. IncidentsofNonCompliance .................................................................... 173
XV. PoliciesandPracticesofInvolvedCompanies ......................................... 175
A. BPsPoliciesandPractices ........................................................................ 175
B. TransoceansPracticesandProcedures ..................................................... 185
C. BPandTransoceanBridgingDocument................................................... 189
D. StopWork
Authority ................................................................................. 189
XVI. ConclusionsRegardingInvolvedCompaniesPractices......................... 191
XVII.SummaryofPanelConclusions.................................................................. 194
A. WellDesignandCementing...................................................................... 194
B. FlowPath ................................................................................................... 195
C. TemporaryAbandonment,KickDetection,andEmergencyResponse ..... 195
D. IgnitionSource .......................................................................................... 197
E. BlowoutPreventer ..................................................................................... 198
F. CompanyPractices .................................................................................... 199
XVIII.Conclusion ..................................................................................................... 200
XIX. Recommendations......................................................................................... 202
A. WellRecommendations.............................................................................. 202
B. KickDetectionandResponseRecommendations ...................................... 203
C. IgnitionSourceRecommendations ............................................................ 205
D. BlowoutPreventerRecommendations ....................................................... 206
E. RegulatoryAgencyRecommendations ...................................................... 207
F. OCSCompaniesPracticesRecommendations.......................................... 209
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Dedication .............................................................................................................211
Acknowledgement...............................................................................................212
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ExecutiveSummary
Atapproximately9:50p.m.ontheeveningofApril20,2010,whilethe
crewoftheDeepwaterHorizonrigwasfinishingworkafterdrillingtheMacondo
exploratorywell,
an
undetected
influx
of
hydrocarbons
(commonly
referred
to
as
akick)escalatedtoablowout. Shortlyaftertheblowout,hydrocarbonsthat
hadflowedontotherigfloorthroughamudgasventlineignitedintwo
separateexplosions. Flowinghydrocarbonsfueledafireontherigthat
continuedtoburnuntiltherigsankonApril22. Elevenmendiedonthe
DeepwaterHorizonthatevening. Overthenext87days,almostfivemillion
barrelsofoilweredischargedfromtheMacondowellintotheGulfofMexico.1
AfteranextensiveinvestigationconductedbytheJointInvestigation
TeamoftheBureauofOceanEnergyManagement,RegulationandEnforcement
(BOEMRE)(formerlytheMineralsManagementServiceorMMS)andthe
UnitedStatesCoastGuard,theBOEMREpanelofinvestigators(thePanel)has
identifiedanumberofcausesoftheMacondoblowout.
ThePanelfoundthatacentralcauseoftheblowoutwasfailureofa
cementbarrierintheproductioncasingstring,ahighstrengthsteelpipesetina
welltoensurewellintegrityandtoallowfutureproduction. Thefailureofthe
cementbarrierallowedhydrocarbonstoflowupthewellbore,throughtheriser
andontotherig,resultingintheblowout. Theprecisereasonsforthefailureof
theproductioncasingcementjobarenotknown. ThePanelconcludedthatthefailurewaslikelydueto:(1)swappingofcementanddrillingmud(referredtoas
fluidinversion)intheshoetrack(thesectionofcasingnearthebottomofthe
well);(2)contaminationoftheshoetrackcement;or(3)pumpingthecementpast
thetargetlocationinthewell,leavingtheshoetrackwithlittleornocement
(referredtoasoverdisplacement).
ThelossoflifeattheMacondositeonApril20,2010,andthesubsequent
pollutionoftheGulfofMexicothroughthesummerof2010weretheresultof
poor
risk
management,
last
minute
changes
to
plans,
failure
to
observe
and
respondtocriticalindicators,inadequatewellcontrolresponse,andinsufficient
1Thisestimateisbaseduponpressurereadings,data,andanalysisconductedbyU.S.scientific
teamscommissionedbytheNationalIncidentCommander. See
http://www.doi.gov/news/pressreleases/USScientificTeamsRefineEstimatesofOilFlowfrom
BPWellPriortoCapping.cfm.
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2
emergencybridgeresponsetrainingbycompaniesandindividualsresponsible
fordrillingattheMacondowellandfortheoperationoftheDeepwaterHorizon.
BP,asthedesignatedoperatorunderBOEMREregulations,was
ultimatelyresponsibleforconductingoperationsatMacondoinawaythat
ensuredthesafetyandprotectionofpersonnel,equipment,naturalresources,
andtheenvironment. Transocean,theowneroftheDeepwaterHorizon,was
responsibleforconductingsafeoperationsandforprotectingpersonnelonboard.
Halliburton,asacontractortoBP,wasresponsibleforconductingthecementjob,
and,throughitssubsidiary(SperrySun),hadcertainresponsibilitiesfor
monitoringthewell. CameronwasresponsibleforthedesignoftheDeepwater
Horizonblowoutpreventer(BOP)stack.
Atthetimeoftheblowout,therigcrewwasengagedintemporary
abandonmentactivitiestosecurethewellafterdrillingwascompletedandbeforetheDeepwaterHorizonleftthesite. InthedaysleadinguptoApril20,BP
madeaseriesofdecisionsthatcomplicatedcementingoperations,added
incrementalrisk,andmayhavecontributedtotheultimatefailureofthecement
job. Thesedecisionsincluded:
Theuseofonlyonecementbarrier. BPdidnotsetanyadditionalcementor
mechanicalbarriersinthewell,eventhoughvariouswellconditions
createddifficultiesfortheproductioncasingcementjob.
Thelocationoftheproductioncasing. BPdecidedtosetproductioncasingin
alocationinthewellthatcreatedadditionalriskofhydrocarboninflux.
Thedecisiontoinstallalockdownsleeve. BPsdecisiontoincludethesetting
ofalockdownsleeve(apieceofequipmentthatconnectsandholdsthe
productioncasingtothewellheadduringproduction)aspartofthe
temporaryabandonmentprocedureatMacondoincreasedtherisks
associatedwithsubsequentoperations,includingthedisplacementof
mud,thenegativetestsequenceandthesettingofthesurfaceplug.
Theproductioncasingcementjob. BPfailedtoperformtheproduction
casingcementjobinaccordancewithindustryaccepted
recommendations.
ThePanelconcludedthatBPfailedtocommunicatethesedecisionsand
theincreasingoperationalriskstoTransocean. Asaresult,BPandTransocean
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personnelonboardtheDeepwaterHorizonontheeveningofApril20,2010,did
notfullyidentifyandevaluatetherisksinherentintheoperationsthatwere
beingconductedatMacondo.
OnApril20,BPandTransoceanpersonnelonboardtheDeepwaterHorizon
missedtheopportunitytoremedythecementproblemswhenthey
misinterpretedanomaliesencounteredduringacriticaltestofcementbarriers
calledanegativetest,whichseekstosimulatewhatwilloccuratthewellafterit
istemporarilyabandonedandtoshowwhethercementbarrier(s)willhold
againsthydrocarbonflow.
Therigcrewconductedaninitialnegativetestontheproductioncasing
cementjobthatshowedapressuredifferentialbetweenthedrillpipeandthekill
line,whichisahighpressurepipeleadingfromtheBOPstacktotherigpumps.
Thiswasaseriousanomalythatshouldhavealertedtherigcrewtopotentialproblemswiththecementbarrierorwiththenegativetest. Aftersome
discussionamongmembersofthecrewandasecondnegativetestonthekill
line,therigcrewexplainedthepressuredifferentialawayasabladdereffect,a
theorythatlaterprovedtobeunfounded. Around7:45p.m.,afterobservingfor
30minutesthattherewasnoflowfromthekillline,therigcrewconcludedthat
thenegativetestwassuccessful. Atthispoint,therigcrewmostlikely
concludedthattheproductioncasingcementbarrierwassound.
Thecement
in
the
shoe
track
barrier,
however,
had
in
fact
failed,
and
hydrocarbonsbegantoflowfromtheMacondoreservoirintothewell. Despitea
numberofadditionalanomaliesthatshouldhavesignaledtheexistenceofakick
orwellflow,thecrewfailedtodetectthatthewellwasflowinguntil9:42p.m.
Bythenitwastoolatethewellwasblowingdrillingmudupintothederrick
andontotherigfloor. Ifmembersoftherigcrewhaddetectedthehydrocarbon
influxearlier,theymighthavebeenabletotakeappropriateactionstocontrol
thewell. TherewereseveralpossiblereasonswhytheDeepwaterHorizoncrew
didnotdetectthekick:
Therigcrewhadexperiencedproblemsinpromptlydetectingkicks. TheDeepwaterHorizoncrewhadexperiencedakickonMarch8,2010thatwent
undetectedforapproximately30minutes. BPdidnotconductan
investigationintothereasonsforthedelayeddetectionofthekick.
TransoceanpersonneladmittedtoBPthatindividualsassociatedwiththe
March8kickhadscrewedupbynotcatchingthekick. Tenofthe11
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individualsondutyonMarch8,whohadwellcontrolresponsibilities,
werealsoondutyonApril20.
Simultaneousrigoperationshamperedtherigcrewswellmonitoringabilities.
Therigcrewsdecisiontoconductsimultaneousoperationsduringthe
criticalnegativetests includingdisplacementoffluidstotwoactivemud
pitsandcleaningthepitsinpreparationtomovetherig complicated
wellmonitoringefforts.
Therigcrewbypassedacriticalflowmeter. Atapproximately9:10p.m.,the
rigcrewdirectedfluiddisplacedfromthewelloverboard,which
bypassedtheSperrySunflowmeter,whichisacriticalkickdetectiontool
thatmeasuresoutflowfromthewell. TheDeepwaterHorizonwas
equippedwithotherflowmeters,butthePanelfoundnoevidencethat
thesemeterswerebeingmonitoredpriortotheblowout.
Oncethecrewdiscoveredthehydrocarbonflow,itsenttheflowtoamud
gasseparator,apieceofequipmentnotdesignedtohandlehighflowrates. The
mudgasseparatorcouldnothandlethevolumeofhydrocarbons,andit
dischargedagasplumeabovetherigfloorthatignited.
ThePanelfoundevidencethattheconfigurationoftheDeepwaterHorizon
generalalarmsystemandtheactionsofrigcrewmembersonthebridgeofthe
rigcontributed
to
a
delay
in
notifying
the
entire
crew
of
the
presence
of
very
highgaslevelsontherig. TransoceanhadconfiguredtheDeepwaterHorizons
generalalarmsystemininhibitedmode,whichmeantthatthegeneralalarm
wouldnotautomaticallysoundwhenmultiplegasalarmsweretriggeredin
differentareasontherig. Asaresult,personnelonthebridgewereresponsible
forsoundingofthegeneralalarm. Personnelonthebridgewaited
approximately12minutesafterthesoundingoftheinitialgasalarmstosound
thegeneralalarm,eventhoughtheyhadbeeninformedthatawellcontrol
problemwasoccurring. Duringthisperiod,therewereapproximately20
alarmsindicatingthehighestlevelofgasconcentrationindifferentareasonthe
rig.
TheDeepwaterHorizonsBOPstack,amassive,360tondeviceinstalledat
thetopofthewell,wasdesignedtoallowtherigcrewtohandlenumeroustypes
ofwellcontrolevents. However,onApril20,theBOPstackfailedtosealthe
welltocontaintheflowofhydrocarbons. Theexplosionslikelydamagedthe
DeepwaterHorizonsmultiplexcablesandhydrauliclines,renderingthecrew
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unabletoactivatetheBOPstack. TheBOPstackwasequippedwithan
automaticmodefunction,whichuponactivationwouldtriggertheblindshear
ram(BSR),twometalblockswithbladesontheinsideedgesthataredesignedto
cutthroughthedrillpipeandsealthewellduringawellcontrolevent.
ThePanelconcludedthatthereweretwopossiblewaysinwhichtheBSR
mighthavebeenactivated:(1)onApril20,bytheautomaticmodefunction,
immediatelyfollowinglossofcommunicationwiththerig;or(2)onApril22,
whenaremotelyoperatedvehicletriggeredtheautoshearfunction,whichis
designedtoclosetheBSRifthelowermarineriserpackagedisconnectsfromthe
restoftheBOPstack. RegardlessofhowtheBSRwasactivated,itdidnotseal
thewell.
AforensicexaminationoftheBOPstackrevealedthatelasticbucklingof
thedrillpipehadforcedthedrillpipeupagainstthesideofthewellboreandoutsidethecuttingsurfaceoftheBSRblades. Asaresult,theBSRdidnot
completelyshearthedrillpipeanddidnotsealthewell. Thebucklingofthe
drillpipe,whichlikelyoccurredatornearthetimewhencontrolofthewellwas
lost,wascausedbytheforceofthehydrocarbonsblowingoutofthewell;bythe
weightofthe5,000feetofdrillpipelocatedintheriserabovetheBOPforcingthe
drillpipedownintotheBOPstack;orbyacombinationofboth. Asaresultof
thefailureoftheBSRtocompletelycutthedrillpipeandsealthewell,
hydrocarbonscontinuedtoflowaftertheblowout.
PriortotheeventsofApril20,BPandTransoceanexperiencedanumber
ofproblemswhileconductingdrillingandtemporaryabandonmentoperations
atMacondo. Theseproblemsincluded:
Recurringwellcontroleventsanddelayedkickdetection. Atleastthree
differentwellcontroleventsandmultiplekicksoccurredduring
operationsatMacondo. OnMarch8,ittooktherigcrewatleast30
minutestodetectakickinthewell. ThedelayraisedconcernsamongBP
personnelabouttheDeepwaterHorizoncrewsabilitytopromptlydetect
kicksandtakeappropriatewellcontrolactions. Despitethesepriorproblems,BPdidnottakestepstoensurethattherigcrewwasbetter
equippedtodetectkicksandtohandlewellcontrolevents. AsofApril20,
TransoceanhadnotcompleteditsinvestigationintotheMarch8incident.
Schedulingconflictsandcostoverruns. Atthetimeoftheblowout,
operationsatMacondoweresignificantlybehindschedule. BPhad
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initiallyplannedfortheDeepwaterHorizontomovetoBPsNilewellby
March8,2010. Inlargepartasaresultofthisdelay,asofApril20,BPs
Macondooperationsweremorethan$58millionoverbudget.
Personnelchangesandconflicts. BPexperiencedanumberofproblems
involvingpersonnelwithresponsibilityforoperationsatMacondo. A
reorganizationthattookplaceinMarchandApril2010changedtheroles
andresponsibilitiesofatleastnineindividualswithsomeresponsibility
forMacondooperations. Inaddition,thePanelfoundevidenceofa
conflictbetweentheBPdrillingandcompletionsoperationsmanagerand
theBPwellsteamleaderandevidenceofafailuretoadequatelydelineate
rolesandresponsibilitiesforkeydecisions.
Atthetimeoftheblowout,bothBPandTransoceanhadextensive
proceduresinplaceregardingsafedrillingoperations. BPrequiredthatitsdrillingandcompletionspersonnelfollowadocumentedandauditablerisk
managementprocess. ThePanelfoundnoevidencethattheBPMacondoteam
fullyevaluatedongoingoperationalrisks,nordiditfindevidencethatBP
communicatedwiththeTransoceanrigcrewaboutsuchrisks.
Transoceanhadanumberofdocumentedsafetyprogramsinplaceatthe
timeoftheblowout. Nonetheless,thePanelfoundevidencethatTransocean
personnelquestionedwhethertheDeepwaterHorizoncrewwasadequately
preparedto
independently
identify
hazards
associated
with
drilling
and
other
operations.
EveryoneonboardtheDeepwaterHorizonwasobligatedtofollowthe
TransoceanstopworkpolicythatwasinplaceonApril20,whichprovided
that[e]achemployeehastheobligationtointerruptanoperationtopreventan
incidentfromoccurring. DespitethefactthatthePanelidentifiedanumberof
reasonsthattherigcrewcouldhaveinvokedstopworkauthority,noindividual
ontheDeepwaterHorizondidsoonApril20.
ThePanelfoundevidencethatBPand,insomeinstances,itscontractorsviolatedthefollowingfederalregulations:
30CFR250.107BPfailedtoprotecthealth,safety,property,andthe
environmentby(1)performingalloperationsinasafeandworkmanlike
manner;and(2)maintainingallequipmentandworkareasinasafe
condition;
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30CFR250.300BP,Transocean,andHalliburton(SperrySun)failedto
takemeasurestopreventtheunauthorizedreleaseofhydrocarbonsinto
theGulfofMexicoandcreatingconditionsthatposedunreasonablerisk
topublichealth,life,property,aquaticlife,wildlife,recreation,navigation,
commercialfishing,orotherusesoftheocean;
30CFR250.401BP,Transocean,andHalliburton(SperrySun)failedto
takenecessaryprecautionstokeepthewellundercontrolatalltimes;
30CFR250.420(a)(1)and(2)BPandHalliburtonfailedtocementthe
wellinamannerthatwouldproperlycontrolformationpressuresand
fluidsandpreventthereleaseoffluidsfromanystratumthroughthe
wellboreintooffshorewaters;
30CFR250.427(a)BPfailedtousepressureintegritytestandrelated
holebehaviorobservations,suchasporepressuretestresults,gascut
drillingfluid,andwellkickstoadjustthedrillingfluidprogramandthe
settingdepthofthenextcasingstring;
30CFR250.446(a)BPandTransoceanfailedtoconductmajor
inspectionsofallBOPstackcomponents;and
30CFR250.1721(a)BPfailedtoperformthenegativetestprocedures
detailedinanapplicationforapermittomodifyitsplans.
AlthoughthePanelfoundnoevidencethatMMSregulationsineffecton
April20,2010wereacauseoftheblowout,thePanelconcludedthatstronger
andmorecomprehensivefederalregulationsmighthavereducedthelikelihood
oftheMacondoblowout. Inparticular,thePanelfoundthatMMSregulationsin
placeatthetimeoftheblowoutcouldbeenhancedinanumberofareas,
including:cementingproceduresandtesting;BOPconfigurationandtesting;
wellintegrity
testing;
and
other
drilling
operations.
In
addition,
the
Panel
found
thattherewereanumberofwaysinwhichtheMMSdrillinginspections
programcouldbeimproved. Forexample,thePanelconcludedthatdrilling
inspectionsshouldevaluateemergencydisconnectsystemsand/orotherBOP
stacksecondarysystemfunctions. BOEMREhasalreadyimplementedmanyof
theseimprovements.
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ThisReportsetsforthindetailthePanelsinvestigativefindings,
conclusions,andrecommendations. ThePanelsfindingsandconclusionsare
presentedinthefollowingsubjectareas:welldesign;cementing;possibleflow
paths;temporaryabandonmentoftheMacondowell;kickdetectionandrig
response;ignitionsourceandexplosion;thefailureoftheDeepwaterHorizon
blowoutpreventer;regulatoryfindingsandconclusions;andcompanypractices.
ThisReportconcludeswiththePanelsrecommendations,whichseekto
improvethesafetyofoffshoredrillingoperationsinavarietyofdifferentways:
Welldesign. Improvedwelldesigntechniquesforwellswithhighflow
potential,includingincreasingtheuseofmechanicalandcementbarriers,
willdecreasethechancesofablowout.
Wellintegritytesting. Betterwellintegritytestpractices(e.g.,negativetestpractices)willallowrigcrewstoidentifypossiblewellcontrolproblemsin
atimelymanner.
Kickdetectionandresponse. Theuseofmoreaccuratekickdetectiondevices
andothertechnologicalimprovementswillhelptoensurethatrigcrews
candetectkicksearlyandmaintainwellcontrol. Bettertrainingalsowill
allowrigcrewstoidentifysituationswherehydrocarbonsshouldbe
divertedoverboard.
Rigengineconfiguration(airintakelocations). Assessmentandtestingof
safetydevices,particularlyonrigswhereairintakelocationscreate
possibleignitionsources,maydecreasethelikelihoodofexplosionsand
fatalitiesintheeventofablowout.
Blowoutpreventers. ImprovementsinBOPstackconfiguration,operation,
andtestingwillallowrigcrewstobebetterabletohandlewellcontrol
events.
Remotelyoperatedvehicles(ROVs). StandardizationofROVinterventionpanelsandinterventioncapabilitieswillallowforimprovedresponse
duringablowout.
ThePanelbelievesthattheadoptionoftheproposedrecommendations
willimprovethesafetyofoffshoreoperationsandwillhelptoreducethe
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9
likelihoodoftheoccurrenceofanothertragiceventsimilartotheMacondo
blowout.
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10
I. Introduction
A.
TheInvestigation
OnApril
27,
2010,
the
Secretaries
of
the
Department
of
Homeland
Security
andtheDepartmentoftheInteriorconvenedajointinvestigationofthe
explosionandsinkingofthemobileoffshoredrillingunitDeepwaterHorizon2by
theBureauofOceanEnergyManagement,RegulationandEnforcement
(BOEMRE)andtheUnitedStatesCoastGuard(USCG). TheConvening
OrderdirectedtheJointInvestigationTeam(JIT)toissueajointreportwithin
ninemonths. ThisdeadlinewasextendedtoallowtheJITtocompletethe
investigation.
OnApril29,2010,anMMSAssociateDirectorappointedtheMMS(now
BOEMRE)membersoftheJIT.3 ThisReportisbasedontheinvestigativerecord
developedbytheJITandcontainsthePanelsfindingsandconclusions.
BOEMREsInvestigationsandReviewUnit(IRU),inclosecoordinationwith
thePanel,hadasubstantialroleinthedraftingandpreparationoftheReport.4
TheConveningOrderprovidesthatrelevantstatutesandregulations
relatingtoboththeUSCGandBOEMREgoverntheJITandthattheJITspublic
hearingsbeconductedinaccordancewiththeUSCGsrulesandprocedures
relatingtoMarineBoardsofInvestigation. Undertheserules,theJITwas
requiredto
formally
designate
certain
companies
and
individuals
involved
with
theDeepwaterHorizonoperationatthetimeoftheblowoutaspartiesininterest
(PIIs)andalsoretainedtheauthoritytodesignateotherPIIsatitsdiscretion.
TheJITdesignatedthefollowingentitiesandindividualsasPIIs:BP,Transocean,
Halliburton,MISWACO,Weatherford,AnadarkoPetroleum,MOEXUSACorp.,
DrilQuip,JimmyHarrell(Transocean),CurtKuchta(Transocean),Douglas
HaroldBrown(Transocean),SteveBertone(Transocean),MikeWilliams
2Joint
Department
of
the
Interior
and
Department
of
Homeland
Security
Statement
of
Principles
andConveningOrderRegardingInvestigationintotheMarineCasualty,Explosion,Fire,
Pollution,andSinkingofMobileOffshoreDrillingUnitDeepwaterHorizon,withLossofLifein
theGulfofMexico,April2122,2010(theConveningOrder). ByorderoftheSecretaryofthe
Interior,datedJune18,2010,BOEMREreplacedtheformerMineralsManagementService
(MMS)astheUnitedStatesoffshoreresourcemanagerandsafetyauthority.3PanelmembersincludedDavidDykes(cochair),GlynnBreaux,JohnMcCarroll,Kirk
Malstrom,andJasonMathews.4IRUmembersincludedMichaelFarber,LisaScanlon,andKishanNair.
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11
(Transocean),PatrickOBryan(BP),andRobertKaluza(BP).5 UndertheMarine
Boardrulesandothergoverningauthorities,thePIIspossessedcertainrights
relatingtotheinvestigation.6
UndertheConveningOrder,theJITwasgiventhefullinvestigative
authorityofboththeDepartmentoftheInteriorandtheDepartmentof
HomelandSecurity.7 TheJITheldsevenpublichearingsandheardtestimony
frommorethan80witnesses.8 Threewitnesseswhosetestimonywassoughtby
theJITinvokedtheirFifthAmendmentrightsagainstselfincriminationand
refusedtotestifyduringtheJIThearings,andtwootherwitnessesclaimedthey
wereunabletotestifyformedicalreasons.9 Inadditiontothepublichearings,
BOEMREinvestigatorsalsoconductedinterviewsofmorethan25individuals
throughouttheinvestigation.
TheJITcollectedandreviewedlargevolumesofelectronicandwrittenmaterial,includingdata,emailsandotherrecordsrelatedtothePIIsequipment,
managementsystems,supervisionofemployeesandcontractors,
communications,performanceandtrainingofpersonnel,relevantcompany
policiesandpractices,andworkenvironment. TheJITissuedmorethan90
subpoenasfordocumentsandotherinformationandcollectedover400,000
pagesofevidence.
Duringthecourseoftheinvestigation,theJITcommissionedseveral
entitiesand
qualified
individuals
to
conduct
expert
analyses
of
evidence.
Dr.
JohnSmith,apetroleumengineerwithPetroleumConsultingLLC,reviewed
5AttherequestoftheRepublicoftheMarshallIslands,theJITdesignateditasaSubstantially
InterestedState. TheDeepwaterHorizonwasaforeignflaggedvesselthat,atthetimeofthe
blowout,wasflaggedundertheRepublicoftheMarshallIslands.6See46U.S.C.6303;46CFR.4.0310,4.0735,4.0915.7ConveningOrder,at1.8RetiredUnitedStatesDistrictJudgeWayneAndersen,whoservedwithoutcompensation,
joinedtheJITinAugust2010topresideoversubsequenthearings. BOEMREisgratefulforJudge
Andersens
assistance
during
the
hearings
and
in
meetings
with
counsel
for
the
PIIs.
9BrianMorelandRobertKaluzaeachinvokedhisFifthAmendmentRightsandrefusedtotestify
duringJIThearings. Aftertestifyingatonehearing,MarkHafleinvokedhisFifthAmendment
Rightsandrefusedtotestifyasecondtime. Throughhisattorney,DonaldVidrineclaimedthat
hecouldnottestifyduetomedicalreasons. EachofthesefourindividualswasaBPemployeeat
thetimeoftheblowoutandcontinuestobeemployedbyBP. Inaddition,twoTransocean
witnessesdeclinedtocooperatewiththeinvestigation,citingtechnicalreasonsfortheirdecisions
nottotestify. Transoceandeclinedtoencouragethesewitnessestocooperatewiththe
investigation.
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12
wellconditiondatacollectedbySperrySunduringthetemporaryabandonment
procedureandreportspreparedbytheInternationalAssociationofDrilling
Contractors(IADC)tohelpreconstructandidentifykeyissuesduringthe24
hoursimmediatelypriortotheblowout. KeystoneEngineeringconducteda
casingbuoyancyanalysis.10 OilfieldTestingandConsultingconductedacement
blendanalysisonsamplesprovidedbyHalliburton. DetNorskeVeritas
(DNV)conductedtheforensicexaminationoftheDeepwaterHorizonsBOP
stackandsectionsofdrillpipeandprovidedaforensicanalysisreportdetailing
theinformationandconclusionsdevelopedbasedonthisexamination.11 These
expertreportsareattachedasappendicestothisReport.
Thepurposeofthisinvestigationwastoidentifythecausesofthe
Macondoblowoutandissuerecommendationsinordertoreducethelikelihood
ofasimilareventinthefuture. Throughoutthisreport,thePanelclassifiesthe
factorsthatcontributedtotheblowoutinthefollowingcategories:
Causesarethosefactorsthatmostimmediatelyandproximatelycaused
theblowout;thatmostdirectlyledtothecircumstancesunderlyingthe
blowout;orthatallowedtheblowouttohappen. Butforthesefactors,
therewouldnothavebeenablowout. Thesefactorsmaybespecific
eventsorconditionsthatexistedinthewellorontherigatthetimeofthe
blowout.
Contributing
Causesare
those
factors
that
alone
would
not
have
led
to
theblowout,butthatweresignificantincontributingtotheeventsor
conditionsthatgaverisetotheblowout. Forafactortobeclassifiedasa
contributingcauseofanevent,theremustbecompellingevidence
supportingboththeexistenceofthefactorandthatitmaterially
contributedtotheoccurrenceorseverityoftheevent.
PossibleContributingCausesarethosefactorsthateitherwereminor
contributingcausesoftheblowoutorforwhichtheevidencesuggeststhe
factorscontributingroleintheblowoutisweakerorlesscompelling.
10Thecasingbuoyancyanalysisevaluatedwhethertheproductioncasingfloatedupthewellbore
aresultoftheblowout.11
Asdiscussedinmoredetaillaterinthisreport,aBOPstackisalargedevicethatsitsontopofa
wellandisdesignedtoassistrigcrewsinmaintainingcontrolofthewell. VariousBOPstack
componentscanbemanuallyorautomaticallyoperatedtosealthewellandprotectagainsta
blowout. ThecentralissueinvestigatedbytheJITregardingtheDeepwaterHorizonBOPwaswhy
theBOPfailedtostoptheflowofhydrocarbonsfromtheMacondowell.
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13
B. BackgroundRegardingDeepwaterDrillingintheGulfof
Mexico
Thegoalofdeepwaterdrillingoperationsistolocateandextractoiland
gas(collectivelyreferredtoashydrocarbons)fromreservoirslocatedbeneath
theseafloor. Insomereservoirs,thehydrocarbonsbecometrappedbeneath
impermeablerock;whenthishappens,thehydrocarbonsseepintosurrounding
porousrock. Drillingoperationsseektopenetratetheimpermeablerocktogetto
hydrocarbonbearingreservoirsorpayzones.
TheGulfofMexicoishometoalargenumberofhydrocarbonreservoirs.
Since1947,morethan50,000wellshavebeendrilledintheU.S.GulfofMexico.
Approximately97%oftheoilproducedontheU.S.OuterContinentalShelf
(OCS)isproducedintheU.S.GulfofMexico. Therearecurrentlynearly7,000activeleasesintheU.S.GulfofMexico,64%ofwhichareindeepwater.12
Since1995,deepwaterdrillingactivityhasincreasedsignificantlyinthe
Gulf. In2001,U.S.deepwateroffshoreoilproductionsurpassedshallowwater
offshoreoilproductionforthefirsttime. AsofMay2010,operatorsdrilled
approximately700wellsinwaterdepthsequaltoorgreaterthan5,000feet,the
approximatedepthoftheMacondowell.13 Deepwaterreservoirscanyieldahigh
volumeofoilandgas. Productionratesfordeepwaterwellsaretypicallymuch
higherthan
in
shallow
water
wells.
Theinitialwellorwellsdrilledintoaformationarereferredtoas
exploratorywells,whichanoperatordrillstodeterminewhetherareservoir
containssufficientvolumesofhydrocarbonstowarrantinvestmentinthe
12SeeDepartmentofInterior,IncreasedSafetyMeasuresforEnergyDevelopmentontheOuter
ContinentalShelf,(May27,2010). Althoughthereisnosingleaccepteddefinitionof
deepwater,acommonuseofthetermistorefertolocationswherethewaterdepthisatleast
1,000feet.
13Id.Operatorsarethepersonsthelessee(s)designatesashavingcontrolormanagementofoperationsontheleasedareaoraportionthereof. Anoperatormaybealessee,theMMS
approveddesignatedagentofthelessee(s),ortheholderofoperatingrightsunderanMMS
approvedoperatingrightsassignment. Lesseemeansapersonwhohasenteredintoalease
withtheUnitedStatestoexplorefor,develop,andproducetheleasedminerals. Thetermlessee
alsoincludestheMMSapprovedassigneeofthelease,andtheownerortheMMSapproved
assigneeofoperatingrightsforthelease. 30CFR250.105.
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14
installationofequipmentrequiredforproduction. Atthisstage,theoperator
mayhavelimitedinformationaboutthegeologicalcharacteristicsofthereservoir
andsurroundingformations. Suchinformation,includingdataaboutthe
surroundingformations,porepressures,14reservoirconfigurationandreservoir
volumes,isdevelopedduringtheexploratorydrillingoperationandmayleadto
changesinthedrillingplanandwelldesignastheoperationproceeds.
Onceanoperatorfinishesdrillinganexploratorywellandperformingits
initialevaluationofthewell,ittypicallysealsthewellbypumpingcementand
installingmechanicalplugs. Thisprocedureiscommonlyreferredtoas
pluggingandabandoningthewell. Iftheoperatorbelievesthatiteventually
willbeabletoproducehydrocarbonsfromtheexploratorywell,itmaychooseto
performtemporaryabandonmentprocedures,whichareproceduresthatallow
thedrillingrigtomoveoffofthewellsothattheoperatorcanreturnatalater
datetocompletethewellandprepareitforproduction.
Atypicaldeepwaterwellisdrilledusingthefollowingprocess:
Adrillingrigmovesonthelocationofthewell. Manyrigsoperatingin
deepwateraredynamicallypositioned,whichmeansthattheyarenot
mooredtotheseafloorbutinsteadholdtheirpositionoverthewell
throughacombinationofsatellitetechnologyanddirectionalthruster
activity. TheDeepwaterHorizonwasadynamicallypositionedrig.
Theriglowersdrillpipe(alsoknownasadrillstring)withadrillbit
attachedtoitsend. Thedrillbitboresintotheseafloorandthesubsea
formationtomakeahole. Thatholeisreferredtoasthewellbore.
Theriginstalls,orsets,alargediameterpipeknownascasinginto
thewellboretoestablishabarrierbetweenthewellboreandthe
surroundingformationandtoensurethatcontinueddrillingdoesnot
resultinthecollapseofthewellbore. Theinitialcasingthatissetinthe
wellboreiscalledconductorcasing.
Therigthenusesthemarineriserorriser,whichisalargepipethat
surroundsthedrillpipe,tolowerthesubseaBOPstackontothewell.
ThesubseaBOPislatchedtothewellheadontheconductorcasing.
14Porepressureisthepressureoffluidswithintheporesofareservoir.
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Asdrillingprogresses,therigsetsadditionalcasings(sectionsofpipe)
thatareslightlysmallerindiameterthantheholecreatedbythedrillbit.
Thecombinationofcasingsisreferredtoasthecasingstring. The
casingsarebondedintoplaceusingcement. Thecasingstringmaintains
theintegrityofthewellborebyprotectingthesidesofthewellborefrom:
(1)pressureexertedfromthedrillingmud;(2)collapseoftheholealready
drilled;and(3)influxoffluidsfromthesurroundingformation.
Theoutermostcasingnearthetopofthewellcanbeuptofourfeetin
diameter,andtheinnermoststringofcasingnearthebottomofthewell
canbelessthansixinchesindiameter. Thesizeoftheinitialandfinal
casing,thetypesofcasing,andthetypeofcementusedaredetermined
bytheprofileofthewellbeingdrilled,includingfactorssuchaswell
depth,temperatures,andwellpressures. Oncethewellisinproduction,
hydrocarbonsareextractedthroughatubingstringthatisrundownthroughthemiddleoftheproductioncasingstring.
Duringdrilling,therigcrewpumpsafluid,calleddrillingmudor
muddownthedrillpipeandthroughthedrillbitnozzles. Althoughthefluid
isreferredtoasmud,itisactuallyacomplexsystemcomprisedofcomponents
thataredesignedinlightof,andtailoredto,avarietyofwellconditions. The
mudsprimaryfunctionistoassistdrillcrewsinmaintainingwellcontrol.
Drillingmudexertshydrostaticpressureinthedrillpipeandannulus(thespace
betweenthe
drill
pipe
and
the
walls
of
the
casing
strings
or
open
hole)
that
is
equaltoorgreaterthanthepressuresencounteredinthewellbore,thereby
keepingthewellbalancedandundercontrol. Drillingmudalsocoolsthedrill
bitandliftscuttingstothesurfaceasthemudiscirculatedduringdrilling.15 By
closelymonitoringwellpressure,rigcrewsmaintainthewellborefluidpressure
sothatitisequaltoorslightlygreaterthanthepressuresfromtheformation.
Thistypeofpressurebalanceisreferredtoasanoverbalancedcondition. By
contrast,awellisinanunderbalancedconditionwhentheformationpressures
exceedthewellboredrillingfluidpressures. Rigcrewsrelyuponanumberof
indicatorstotrackfluidpressures.16
15Operatorsroutinelyrelyupondrillingmudsupplierstoprovideassistancewithchoosingan
appropriatedrillingmud. Drillingrigcrewsincludemudloggerswhomonitordrillingmud,
wellborepressures,andotherdata.16Thisprocessofmonitoringwellpressuresisreferredtoasmeasurementwhiledrilling.
Operatorsalsoroutinelyrelyupondrillingmudsupplierstoprovideassistancewithchoosingan
appropriatedrillingmudandtoprovidemudloggersontherigtomonitordrillingmud,
wellborepressures,andotherdata.
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16
Cementingisanimportantfactorinwelldesignandtheexecutionofa
safedrillingprogram. Aftereachcasingstringisset,cementispumpeddown
thedrillstring,outthebottomofthecasingandbackupintotheannularspace.
Thecementreinforcesthecasingstringandsealsofftheannularspace,
preventinghydrocarbonsfromflowingthroughthespace. Aproperlycemented
annularspaceissaidtohaveachievedzonalisolation. Operatorsoftenwork
withcontractorsthatpossessspecificcementingexpertisetodeveloptheoptimal
typeofcementforaparticulardrillingoperation. Cementingcompaniesalsocan
helpmodeldifferentanticipatedwellconditionstohelpdrillingengineersto
designasuccessfulcementjob. Thereareanumberofdifferentteststhatcanbe
performedtoassessthequalityofacementjob.
Duringthedrillingprocess,pocketsofoil,naturalgas,orwaterthatare
encounteredinporouslayersoftheformationcanexertpressureintothewellborethatmaysuddenlyforcemudbackupthewellborewithconsiderable
forcethisiscommonlyreferredtoasakick. Tohandlekicksandtomaintain
wellcontrol,drillingcrewsusevariousmechanisms,including,underextreme
circumstances,activationoftheBOPstackanddiverters. Ifakickoverwhelms
thecontrolmechanisms,ablowouttheuncontrolledflowofhydrocarbons
throughthewellborecanoccur.
C.
CompaniesInvolvedintheMacondoWell
BPandTransoceanweretheprimarycompaniesinvolvedindrillingthe
Macondowell. BPwasthemajorityowneranddesignatedoperatorofthelease.
BPidentifiedtheprospectanddesignedandplannedthewell. Transoceanwas
thedrillingcontractorengagedbyBPtodrilltheMacondowellandprovidethe
DeepwaterHorizon,adynamicallypositioned,mobileoffshoredrillingunit(DP
MODU),aswellasthedrillingpersonnel.
BPisaglobaloilandgascompanyheadquarteredinLondon,England.
BPoperatesinmorethan80countriesandisinvolvedinoilandgas
exploration,production,andrefining,aswellastheoperationofservicestationsworldwide. BPholdsmorethan500activeleasesin
theGulfofMexico,morethananyotherlessee. From2005through
2009,BPwastheleadingproducerofoilandgasintheGulfofMexico,
producing559,336,436barrelsofoiland846,352,047MCF(thousand
cubicfeet)ofgasduringthatperiod.
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17
Transoceanistheworldslargestoffshoredrillingcontractor. Basedin
Switzerland,Transoceanownsmorethan140drillingrigsandoperates
inthemajoroffshoreoilandgasfieldsintheworld. Transoceanhas
grownsubstantiallythroughaseriesofcorporateacquisitions,
includingtheacquisitionofReading&BatesFalcon(R&BFalcon)in
2000andGlobalSantaFein2007. TransoceanownedtheDeepwater
Horizonrig,whichwasunderalongtermleasetoBPatthetimeofthe
Macondoblowout. TheleaseagreementrequiredTransoceanto
manageandoperatetheDeepwaterHorizononbehalfofBP.
Offshoredrillingoperationsarecomplexandnormallyinvolvethework
ofmanydifferentspecialists. InadditiontoBP,theleaseholderandthe
designatedoperatoroftheMacondowell,andTransocean,thefollowing
companiesalsohadsignificantrolesintheoperation:
Halliburton,whichprovidesproductsandservicestotheenergy
industryworldwideandisoneoftheworldslargestcementing
contractorstotheoilandgasindustry,providedcementplanning,
products,andservicesatMacondo.
AnadarkoE&PCompanyLP,AnadarkoPetroleumCorporationand
MOEXwereBPspartnersintheMacondowell. AnadarkoE&P
CompanyLPowned22.5%,andAnadarkoPetroleumCorporation
owned2.5%.
17Both
Anadarko
companies
are
U.S.
oil
and
gas
explorationcompanies.18 MOEXOffshore2007,aJapaneseoil
explorationfirm,owneda10%shareofthewell.19 Thecompanies
sharedinBPscoststodrilltheMacondowellandwouldhaveshared
inanyprofitsfromthewell.
Cameron,whichisaTexasbasedmanufacturerofoilandgaspressure
controlequipment,manufacturedtheDeepwaterHorizonsBOPstack.
MISWACO,whichprovidesdrillingsuppliesandservices
worldwide,developedthemudprogramandprovideddrillingmudandpersonneltooperatetheDeepwaterHorizonrigsmudsystem.
17BP-HZN-MBI-00192559.18BPHZNMBI00177777.19Id.
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18
Schlumberger,whichprovidesoilfieldservicesthroughouttheworld,
providedwellloggingservicesfortheMacondowell.
SperryDrilling(SperrySun),asubsidiaryofHalliburtonthat
providesdrillingdatasystemsandpersonneltothedrillingindustry,
equippedtheDeepwaterHorizonwithSperrydatasensorsandSperry
mudloggerstomonitorandevaluatewellconditiondata. The
DeepwaterHorizonwasalsooutfittedwithTransoceanpaddleflow
meterstomonitorflow.
Weatherford,whichprovidesavarietyofdrillingservicesand
components,providedthecasing,casingcentralizers,andfloat
conversionequipmentusedontheDeepwaterHorizon.
D.
TheDeepwater
Horizon
TheDeepwaterHorizonwasadeepwater,columnstabilized,semi
submersibleDPMODU,designedtodrillsubseawellsforoilandgas
explorationanddevelopment. TheDeepwaterHorizonwasbuiltforR&BFalcon
(whichlaterbecamepartofTransocean)byHyundaiHeavyIndustriesinUlsan,
SouthKorea. ConstructionstartedinDecember1998,andtherigwasdelivered
onFebruary23,2001,afterTransoceanacquiredR&BFalcon. Atthetimeofthe
blowout,theDeepwaterHorizonwasregisteredinMajuro,MarshallIslands,and
leasedto
BP.
TheDeepwaterHorizonsdayrateatthetimeoftheblowoutwas$533,495
andtherigstotalestimateddailyoperatingcostswereapproximately$1
million.20 Asiscommonintheindustry,underitscontractwithBP,Transocean
wasallowedaspecificamountoftime(inthiscase,uptotwentyfourhoursper
calendarmonth)formechanicaldowntimetoperformmaintenanceandrepairs
withamaximumaccumulationof12daysofdowntimeperyear.21 Transocean
wasnotpaiditsdayrateiftherigwasnotoperationalduetoequipmentrepairs
fortimeperiodsbeyondthisallotment.22
20TRNUSCG_MMS00040941.21TRNUSCG_MMS00040482.22Id.
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19
E. TheMacondoWell
BPacquiredLeaseOCSG32306inanMMSCentralGulfofMexicolease
saleonMarch19,2008. Thisleasecovers5,760acresandextendsfor10years,
beginningonJune1,2008. BPisthedesignatedleaseoperatorandshares
ownershipoftheleasewithAnadarkoandMOEX.
TheMacondowellislocatedapproximately48milesfromthenearest
shoreline,114milesfromtheshippingsupplypointofPortFourchon,Louisiana,
and154milesfromtheHouma,Louisianahelicopterbase. BPbegandrillingthe
Macondowell(referredtoasspuddingthewell)onOctober7,2009,using
TransoceansMarianasrig. AftertheMarianassustaineddamageduring
HurricaneIdainNovember2009,BPmovedtheDeepwaterHorizontothe
Macondowell. TheDeepwaterHorizoncrewresumeddrillingoperationsat
MacondoinFebruary2010.
BPandTransoceanexperiencedseveralchallengesindrillingthe
Macondowell. InOctober2009,thewellexperiencedakickduringdrilling
operations.23 ThedrillingcrewexperiencedanotherkickonMarch8,2010. Asa
resultoftheMarch8kick,thedrillpipebecamestuckinthewellbore,andtherig
crewcouldnotpullthepipefree.24 Thecrew,therefore,hadtoseverthedrill
pipeanddrillabypassaroundtheportionofthewellwiththestuckpipe.25 The
wellalsoexperiencedseverallostreturnincidentsduringdrilling,when
drillingmud
pumped
down
the
wellbore
did
not
return
to
the
surface
as
expectedbecausesomevolumeofthemudflowedintoandwaslostinthe
formation.26 Lostreturnsarenotuncommonandcanoccurforavarietyof
reasons,suchasafractureintheformationordrillinginoverbalanced
conditions.27 Becauseoftheseandotherchallenges,onApril20,2010,the
Macondowellwasabout38daysbehindscheduleandapproximately$58
millionovertheoriginalbudget.28
23MC252WellActivityReport,10/25/2009.24IADCReports,3/8/10 3/12/10.25Abypassisasecondarywellboredrilledawayfromtheoriginalhole. Itisnotuncommonfor
anoperatortodrillabypasswhileexperiencingproblemsduringthedrillingofawell.26IADCReports,3/8/10 3/12/10.27AsdiscussedthroughouttheReport,thelostreturnsattheMacondowellwereofnotebecause
oftheirfrequencyandbecausetheyoccurredalongwithotheranomalies.28BPHZNMBI00125958;BPHZNMBI0019553;BPMBHZN00192599.
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Despitetheseproblems,byApril14,theDeepwaterHorizoncrew
successfullydrilledtotheM56sand,oneofthehydrocarbonbearingzones
thatBPgeologistsandengineershadtargetedforthewell.29 Althoughthe
originalwellplanwastodrillapproximately1,800additionalfeet,theBPdrilling
teaminHoustonoptedtostopdrillingthewellatatotaldepthof18,360feet
becauseBPbelievedthewellhadreachedthebaseofthetargetreservoirandthat
ithadrunoutofdrillingmargin.30 Inotherwords,BPconcludedthatitcouldno
longersafelydrillintotheformationwithoutcreatinganunderbalancedwell(if
themudwastoolight)orriskingfracturingtheformationandthreateningwell
integrity(ifthemudwastooheavy). BPplannedtorunproductioncasingand
temporarilyabandonMacondobysealingitwithasurfacecementplugsothat
anotherrigcouldreturntothewelllaterandtakethestepsnecessarytocomplete
thewellforproduction.
OnApril19,theDeepwaterHorizoncrewrantheproductioncasingstringintothewell.31 BPsengineeringteamhadengagedinsignificantdebateoverthe
appropriatedesignofthecasingtoruninthefinalwellsection. Therewas
additionaldebateamongBPpersonnelaboutthenumberofcentralizers,which
arepiecesofequipmentusedtokeepthecasingcenteredinthewell,touseon
thefinalcasingstring. Thecrewpumpedcementintotheannulusandintothe
shoetrack,thesectionofthecasingbetweenthebottomofthewellandthefloat
valveinstalledinthewell(alargevalvedesignedtoallowfluidstoflowdown
thewellwhilepreventingfluidsfromflowingbackupthewellboreduring
cementingoperations).
Thepurposeofthecementjobwastoestablishanisolationbarrieracross
thehydrocarbonzoneatthebottomofthewellsothathydrocarbonscouldnot
enterthewell. InthelatehoursofApril19andintothemorningofApril20,the
rigcrewandBPscementcontractor,Halliburton,pumpedcementintothe
Macondowelltoisolatethehydrocarbonzones.32 BasedondataprovidedbyBP,
Halliburtondesigned the cement slurry, whichisamixtureofcement,waterand
29BPHZNMBI00126338.30Id. AsdiscussedindetaillaterinthisReport,drillingmarginisthedifferencebetweenthe
weightofthemudusedtodrillrelativetotheporepressuresandthefracturegradientofthe
formation. Commonindustrypracticeistouseadrillingmarginof0.5ppgmudweightunder
thefracturegradient.31IADCReport4/19/10.32HalliburtonPostJobCementReport,BPHZNCEC011406.
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assorteddryandliquidadditives.33 After BP approved the design, Halliburtonbegan pumping the cement.
Inadditiontocementing,theprocessofpreparingawellfortemporary
abandonmentincludesfurtherprocedurestosecurethewellsothattherigsBOP
stackandrisercanberemovedastherigpreparestomoveoffthelocation. BP
engineersinHoustondevelopedtemporaryabandonmentprocedures(different
fromtheMMSapprovedprocedure)fortheMacondowellthatincludedthe
followingsteps:performingapositivepressuretest;34displacingmudinthewell
from8,367feettothewellhead;performinganegativepressuretest;35settinga
300footcementpluginthewellapproximately3,300feetbelowtheseafloorand
settingalockdownsleevetolockthefinalcasingintoplace.36 BPengineers
changedtheorderofthesestepsseveraltimesinthedaysbeforethetemporary
abandonment.
Duringallwellactivities,includingtemporaryabandonment,crew
membersmonitorvarioussensorsontherigthatshowfluidvolumesandwell
pressures.37 Thesesensorsproviderealtimedatatothecrew,whichmonitors
andanalyzesthedataonelectronicdisplaystoidentifypotentialkicks,among
otherthings. Earlykickdetectioniscriticaltomaintainingwellcontrol.
OnApril20,thecrewconductedteststoevaluatetheintegrityofthe
productioncasingcementjob. ThetestswerebasedonMMSapproved
procedures
that
a
BP
drilling
engineer
had
sent
to
the
rig
that
morning.38
The
crewfirstconductedapositivepressuretesttoevaluatewhetherthewellcasing
couldsustainpressureexertedonitfromtheinsideofthewellandreceived
favorableresults.39 Onthesameafternoon,thecrewcirculatedmudupfromthe
33Additivesareusedtotailorthecementtotheneedsofawell. Forexample,aweighting
materialmightbeaddedtoacementslurrywhenahigherdensitycementisneeded.34Apositivepressuretestisconductedbypumpingfluidintothewellaftersealingtheblind
shearrams. Therigcrewmonitorsthewelltodeterminewhetherpressuresinthewellremain
static.35
A
negative
pressure
test
seeks
to
create
conditions
that
simulate
what
will
occur
when
the
well
isabandoned. Therigcrewdisplacesdrillingmudwithotherfluids,resultinginthewellbore
beingunderbalancedagainsttheformationpressures. Therigcrewthenmonitorspressuresand
flowtodeterminetheintegrityofthebarrierbeingtested.36BPHZNMBI00129108. EachofthesestepsisdiscussedindetailinSectionIofthefindings
andconclusionsinthisReport.37Fluidincludesanyfluid(mud,spacer,seawater)comingoutofthewelloracrosstherig.38BPHZNMBI00021237.39BPHZNMBI00136947.
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well,andpumpedtherecoveredmudontotheDamonBankston,avesselworking
alongsidetheDeepwaterHorizonatMacondo. Becauseofthemovementofthe
mud,itwasdifficultforthecrewtotrackfluidvolumesinthewellboreandin
themudpitsontherig.40
Next,crewmembersturnedtoconductingnegativepressuretestsonthe
well,whichwouldgivethecrewinformationaboutwhethertheproduction
casingcementjobwascapableofkeepinghydrocarbonsoutofthewellbore. The
crewrantwoseparatenegativetestsusingdifferentproceduresforeachtest.
Justpriorto8:00p.m.onApril20,theBPwellsiteleaderondutyontherig,
DonaldVidrine,andTransoceancrewmembersconcludedthatthesecond
negativetestshowedthatthefinalcementjobwassuccessful.41 Vidrinealso
calledMarkHafle,aBPengineerinHouston,around8:50p.m.todiscussthe
surfaceplug. Duringthiscall,Vidrinedescribedtheresultsofthenegativetests.
HaflequestionedVidrineabouttheresultsofthenegativetest,buthechosenottoinvestigatefurtherbyaccessingandreviewingtheavailablerealtimedata.
Instead,HaflechosetorelyuponVidrinesassurancethattherigcrewhad
successfullyperformedanegativetest.42
DuringtheeveningofApril20,theDeepwaterHorizoncrewcontinued
withthetemporaryabandonmentprocedurebyopeningtheBOPandpumping
seawaterdownthedrillpipetodisplacemudandaspacerfromtheriser.43
Duringthesewellactivities,thewellexperiencedsignificantchangesinpressure.
Personnelresponsible
for
monitoring
the
condition
of
the
well,
however,
did
not
recognizethesechangesassignsofakick. Thecrewmembersshutdownthe
wellaround9:15p.m.toperformasheentestonthespacerthattheyplannedto
sendoverboardasitwasdisplacedfromthewell.44 Thedecisiontosendthe
displacedspaceroverboardrenderedSperrySunpersonnelunabletomeasure
returnsononeoftherigsflowmeters. Duetotheplacementoftheflowmeters,
40BPHZNMBI00021238.41TestimonyofJimmyHarrell,JointInvestigationHearing,May27,2010,at9091;Testimonyof
MilesEzell,JointInvestigationHearing,May28,2010,at279282.42
BP
HZN
BLY00125470.
43Spacerreferstomaterialthatrigcrewspumpintoawelltoseparatethedrillingmudfrom
seawater. Displacementofmudandspacerarepartofthetemporaryabandonmentprocedures
discussedindetailinSectionIVofthefindingsandconclusions.44SperrySunrigdata,April20,2010. Thecrewperformedasheentesttoconfirmthatallofthe
oilbasedmudhadbeendisplacedfromtheriser. Asheentestisintendedtoindicatethe
presenceoffreeoilwhendrillingfluid,drilledcuttings,deckdrainage,welltreatmentfluids,
completionandworkoverfluids,producedwaterorsandorexcesscementslurryaredischarged
intooffshorewaters.
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theSperrySuncrewcouldonlymeasurereturnssenttothemudpitsandcould
notmeasureflowvolumessentoverboard.45
F.
TheBlowout
OnApril20,2010,ataround9:40p.m.,powerfulpressuresfromthewell
causedmudtoflowupfromthewell. Mudspilledontherigfloorasthewell
begantoblowout. Thecrewrespondedtothesituationbydivertingtheflowto
themudgasseparator,partofthedivertersystemtowhichthecrewcoulddirect
fluidscomingupfromthewell.46 Atthistime,crewmemberslikelyrealizedthat
theyhadlostcontrolofthewellandattemptedtoregaincontrolofthewellby
activatingtheBOPstacksupperannularpreventerandtheuppervariablebore
ram.47
Themudgasseparator,towhichthecrewhaddivertedflowfromthewell,wasquicklyoverwhelmedandfailed,causingagasplumetofilltherig
floor. Thegasquicklyignited,causingthefirstexplosionontherigat9:49p.m.
Approximatelytensecondslater,asecondlargerexplosionoccurredandthefire
onboardtherigspreadrapidly. Shortlyafterthesecondexplosion,theriglost
powerandexperiencedatotalblackout.
Atapproximately9:56p.m.,therigssubseaengineerattemptedto
activatetheBOPstacksemergencydisconnectsystemfromtheBOPpanelonthe
rigsbridge.
The
emergency
disconnect
system
is
designed
to
activate
the
BOP
stacksblindshearramanddisconnecttherigslowermarineriserpackage
(LMRP)fromthewell. TheBOPpanelapparentlyindicatedthatthe
emergencydisconnectsystemwasactivated,buttherigremainedconnectedto
thewellandhydrocarbonscontinuedtoflowuncontrolledfromthewell.48
Aboutfourminutesaftertheattempttoactivatetheemergencydisconnect
system,personnelontheDeepwaterHorizonsbridgemanuallysoundedthe
generalalarmandmadeamustercallforpersonneltogatheratdesignated
45
Testimony
of
Joseph
Keith,
Joint
Investigation
Hearing,
December
7,
2010,
at
135.
46Themudgasseparator,andtherigcrewsdecisiontouseittohandletheinfluxof
hydrocarbonsfromthewell,isdiscussedindetailinSectionVDofthefindingsandconclusions.47DNV,ForensicExaminationofDeepwaterHorizonBlowoutPreventer,March20,2001,(DNV
Report)at4. AsdiscussedinlaterinthisReport,theupperannularpreventerandtheupper
variableboreramaretwoBOPstackcomponentsthatareusedbyrigcrewsinwellcontrol
events. Neithercomponent,however,isdesignedtoshearthedrillpipeandcompletelysealthe
welltheblindshearramontheBOPstackisdesignedtoperformthesefunctions.48TestimonyofChrisPleasant,JointInvestigationHearing,May28,2010,at123.
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lifeboatstations. Personnel,includingcrewmembers,contractorsandvisiting
executivesfromBPandTransocean,evacuatedtherigontwolifeboatsandalife
raft. Atleastsixpeoplejumpedfromtherigintothewater.
At10:00p.m.,theDamonBankston,whichpriortotheexplosionshadbeen
directedbytheDeepwaterHorizontomove500metersawayfromtherig,
receiveddistresscallsfromtheDeepwaterHorizonandprepareditsfastrecovery
craftforlaunchandrescueofthosewhohadabandonedtherig. TheDamon
Bankstonretrievedsixpeoplefromthewaterandrecoveredanother108people
fromthetwolifeboatsandliferaft. Uncontrollablefirescontinuedtoblazeon
theDeepwaterHorizon,andtherigsankonthemorningofApril22.
Elevenmendiedasaresultoftheblowoutandsixteenotherswere
injured. EstimatesarethattheMacondowellspilledclosetofivemillionbarrels
ofoilintotheGulfofMexicoduring87daysbetweentheblowoutandwhenthewellwassuccessfullycappedonJuly15,2010. Aftermonthsofadditional
interventionwork,thewellwaspermanentlysealedonSeptember19,2010.
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II. WellDesign
Welldesignisafundamentalandimportantphaseofoffshoredrilling
operations. Operatorsmustconsidersitespecificfactors,includingflows,
pressurizedformation
flows,
reservoir
natural
gas
and
oil
type,
reservoir
lithology(formationcharacteristics),reservoirstructure,andtheanticipated
volumeofhydrocarbonstodeterminethebestwaytodrilltothetargetreservoir
andtoconfigurecasingtoallowproductionfromthewell. Duringthedesign
process,engineersuseallavailabledatatodetermineplannedtotaldepth
(sometimesreferredtoasTD)ofthewell,casingpointselections,required
casingspecifications,casingpressureratings,cementslurrydesign,mudweight,
andriskfactorsparticulartothewell.49
Developmentwellsaretypicallydesignedanddrilledbasedinparton
datafromnearbywells,referredtoasoffsetwelldata. Inthecaseofexploratory
wells,suchasMacondo,operatorshavelimitedoffsetwelldataavailable,
makingitmoredifficulttoanticipatewellconditionspriortothespudofthe
well. Asaresult,designprocessesinexploratorywellsaresubjecttochange.
Operatorstypicallydealwithwelldesignchangesduringdrillingoperations
throughdocumentedmanagementofchangeprocesses,whichareintendedto
aidpersonnelinsystematicallyidentifyingandmitigatingtherisksassociated
withthechanges.
TheBP
well
engineering
team
and
the
BP
subsurface
team
were
involved
indevelopingtheMacondowelldesign. Theteamsreferredtovarious
documentsandmanualswhiledesigningtheMacondowell,includingBPs
internalcasingdesignmanual,drillingwelloperationspolicy(DWOP),
advancedguidelinesfordeepwaterdrillingandotherguidance.50
A.
CostoftheMacondoWell
BPexceededitsoriginalcostestimatesfordrillingtheMacondowell. To
obtainadditionalfundsandcontinuedparticipationfromitspartnersinthe
Macondoproject,BPsubmittedtoAnadarkoE&PCompanyLPandAnadarko
PetroleumCorporation(collectivelyAnadarko)andMOEXseveral
49Casingpointisthedepthatwhichdrillingaparticularwellborediameterwillendsothat
casingofagivensizecanberunandcemented.50BPHZNMBI000010362.
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AuthorizationsforExpenditures(AFEs),whichincludedwrittendescriptions
oftheprojectandcostestimatesforproposedwellactivitiesandoperations.51
UndertheiroperatingagreementwithBP,AnadarkoandMOEXcould
choosetoparticipateintheactivitiesandoperationsdescribedintheAFEand
therebycommittothefundingnecessarytocontinuetheoperation;theycould
proposeanalternativeoperatingplan;ortheycouldendtheirparticipationinthe
Macondoproject.52
BPsubmittedtoAnadarkoandMOEXaninitialAFEfortheMacondo
wellinAugust2009,estimatingthatthetotalcostsofthewellwouldbeabout
$96.1million. BothAnadarkoandMOEXapprovedtheoperationand
expenditures.53 BPsoughtitsfirstsupplementalAFEforapprovalofan
additional$27.9millioninJanuary2010,whichthepartnersacceptedinFebruary
2010.54 InMarch2010,BPsoughtauthorizationforanadditional$27million,explainingthatithadexceededthefirstsupplementalAFEduetounexpected
lostcirculationandwellcontrolevents.55 AnadarkoandMOEXapprovedthe
expenditureandofferednoalternativeoperatingplan.56
OnApril14,afterBPhaddrilledtotheMacondowellsrevisedtarget
depth,itsoughtafinalAFEfor$3.5milliontofundsettingtheproductioncasing
inconnectionwiththetemporaryabandonmentofthewell. Anadarkoand
MOEXapprovedtheAFEanddidnotproposeanyalternativeoperatingplan.57
Intotal,
the
companies
allocated
$154.5
million
to
drilling
the
Macondo
exploratorywell,anamountwellinexcessoftheoriginalestimatedcostof
$96.16millionandthenottoexceedcostof$139.5million.
UndertheiroperatingagreementwithBP,AnadarkoandMOEXhad
accessto,andinfactreviewed,dataandfilesrelatedtotheMacondowellthatBP
madeavailabletothemthroughsharedwebsites. ThePanelfoundnoevidence,
otherthanreviewingthisinformationandapprovingtheAFEs,indicatingthat
51BPHZNMBI000173275.52BPHZNMBI00173275.53BPHZNMBI00192546,BPHZNMBI00192549.54BPHZNMBI00192552,BPHZNMBI00192553.55BPHZNMBI00192557.56BPHZNMBI00192558.57BPHZNMBI00192559,BPHZNMBI00192561.
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AnadarkoorMOEXweredirectlyinvolvedindecisionsrelatedtothedesignor
drillingoftheMacondowell.58
B.
DrillingMargin
Drillingengineersmustdesignawelltomanageporepressureand
fracturegradientsatdifferentwelldepths. Porepressureisthepressureexerted
byfluidsintheporespaceoftheformationbeingdrilled. Fracturepressureis
thepointatwhichpressureexertedbythedrillingfluidinthewellwouldcause
thesurroundingformationtofracture. Thefracturegradientplot,expressedasa
calculatedequivalentmudweight,isacurvethatshowsthewellsestimated
fracturegradientbydepth. Duringwelldesign,engineerstypicallyusea
graphicalrepresentationoftheestimatedporepressure,mudweight,and
fracturegradient,whichtogetherdefinetheappropriatedrillingmargins.
Drillingengineersconductaleakofftesttodeterminethestrengthor
fracturepressureoftheopenformation. Thistestisusuallyconducted
immediatelyafterdrillingpastthecementedcasingshoeinthewell.59 During
thetest,thewellisshutinandfluidispumpedintothewellboretogradually
increasethepressurethattheformationexperiences. Atacertainpressure,fluid
pumpedintothewellwillentertheformation,orleakoff,bymovingthrough
permeablepathsintherockorbycreatingaspacebyfracturingtherock. Ifthe
pressureisincreasedbeyondtheformationfracturepoint,fracturingofthe
formationcan
occur.
The
results
of
the
leak
off
test
dictate
the
maximum
pressureormudweightthatmaybeappliedtothewellduringdrilling
operationsbeforetheformationcanbeexpectedtotakefluid.
BOEMREregulationsrequirethat[w]hiledrilling,youmustmaintainthe
safedrillingmarginidentifiedintheapprovedAPD[ApplicationforPermitto
Drill]. Whenyoucannotmaintainthissafedrillingmargin,youmustsuspend
drillingoperationsandremedythesituation.60 Safedrillingmargincanbe
maintainedbyensuringthatthemudweightremainsbetweenthekick
toleranceorkickmargin,whichistypically0.5poundspergallon(ppg)
58DataobtainedfromHalliburtonshowedthatrepresentativesofAnadarkoandMOEX
periodicallyreviewedinformationrelatedtotheMacondowellduringdrilling.59Thecasingshoeisashortsteelcollarthatistypicallyattachedtothebottomofthecasing
string. Ithelpstoestablishproperpositioningofthecasingstringinthewellbore.6030CFR250.427(b). BOEMREregulationsdonotspecifywhatasafedrillingmarginis.
Theremaybeinstanceswhereasafedrillingmargincanbemaintainedoutsidethekickor
swabmargins.
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belowthefracturegradient,andtheswabmargin,whichistypically0.2ppg
abovetheporepressure. Inshort,themudmustbeheavyenoughtocontrolthe
porepressureandensurethattheformationfluids(includinghydrocarbons)do
notenterthewellbore,whilenotsoheavythatitfracturestheformation.61
BOEMREregulationsrequireoperatorstoprovidevariousdatatothe
Agencydemonstratingthattheoperatorismaintainingasafemargin. For
example,operatorsmustshow,inasinglegraphicplot,porepressures,mud
weightsandfracturegradientsforthefullextentofthewell.62 Theplotteddata
reflectsforecasteddatabasedon3Dseismicandoffsetwelldata.63 When
operatorsencounterunexpectedpressuresthatdifferfromtheirforecasts,
applicableregulationsrequiretheoperatortoreviseitscasingdesignandapply
totheAgencyforapprovalofthemodification.64
ThefinalestimatedMacondowellporepressure,mudweight,andfracturegradientplotsubmittedtoMMSonMarch26isshownatFigure1. The
verticalaxisofFigure1showsthedepthofthewell. Thehorizontalaxisshows
themudweight. TheredlinedepictsBPsplannedmudweight,whichwas
designedtobebetweenthekickmarginandtheswabmarginidentifiedin
Figure1.
61Maintainingmudweightinthisrangeisanindustryacceptedpracticebutisnotspecifically
requiredbyBOEMREregulations.6230CFR250.413and414.63Offsetwelldataaredataobtainedfromwellsthataredrilledinanareaclosetothetarget
well.6430CFR250.427(b).
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Figure1MacondoWellPorePressureFractureGradientPlot65
AsseeninFigure2,theformationintegritytestatthe97/8inchlinershoe
locatedat17,168feetyieldedresultsof15.98ppg(asidentifiedintheIADCdaily
reports,whicharecompletedbytherigcrewtodocumentdailyoperations)and
16.22ppg(identifiedinBPsDailyOperationReport). ThePanelfoundthatthis
integritytestmayhavecreateduncertaintybecause(1)itwas1.0ppghigherthan
anticipatedand(2)therewasapossibilitythatthetestresultsdidnotreflecta
truetestoftheformationbelowthe97/8inchlinershoe. Althoughthisfracture
gradienttestwasquestionable,BPchosenottoretestthefracturegradientatthe
shoeanddecidedtodrillahead. AfterdrillingtheM57Csandinterval,BP
65API608174116901,March26APD(RevisedBypass)fortheMacondoWell.
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conductedaGeotapsurveytodeterminethesandporepressure. Thesandpore
pressurewasdeterminedtobe14.15ppg. BPalsoconvertedthisporepressure
toanestimatedfracturegradientof15.0ppg. Theopenholesectiondrilled
utilizedasurfacemudweightrangeof14.114.5ppg,whichallowedforasafe
drillingmargintobemaintainedbetweenporepressureandfracturegradient.
Throughoutthisinterval,however,BPencounteredmultipleproblems
associatedwithbothlostreturnsandregressingporepressures(1.9ppg
difference)between17,001and18,066feet. BPlostapproximately4,000barrels
(bbls)ofmudintheproductionopenholeinterval. BPutilizedlosscirculation
materialinthisintervaltoattempttocontroltheselosses.
Figure2 DrillingmargindatafromIADCreportsandBPDailyReports
BPcontinueddrillinguntilitconcludedithadrunoutofdrillingmargin
betweenmudweightandformationporepressure. RobertBodek,BPGeological
Operations
Coordinator,
emailed
Michael
Bierne,
another
BP
employee,
on
April
13,2010,andexplainedthereasonswhyBPconcludedthatithadrunoutof
drillingmarginat18,360feet. Hesaidthattheteamdecidedtostopdrilling
becauseithadbecomeawellintegrityandsafetyissue.66 Theemailalsostates:
Wehadonemajorproblemhowever:thesandthatwetooktheinitial
GeoTappressureinwasmeasuredat14.15ppg. Theabsoluteminimum
surfacemudweightwecouldusetocovertheporepressureinthissand
was14.0ppg. Thiswouldgiveusapproximatelya14.2ppgESDoverthe
aforementionedsand. Ifweweretodrillaheadwitha14.0surfacemud
weight/14.2ESD,ourequivalentcirculatingdensity(ECD)wouldbeapproximately14.414.5ppg. Wehadalreadyexperiencedstaticlosses
witha14.5ppgESD! Itappearedasifwehadminimal,ifany,drilling
margin... Drillingaheadanyfurtherwouldunnecessarilyjeopardizethe
wellbore. Havinga14.15ppgexposedsand,andtakinglossesina12.6
66BPHZNMBI00126338.
Date Depth MW Losses PP Remarks Hydrocarbon Zones
2-Apr 17,007 - 17,321 14.3 17,168 FIT 16.22 PPG 17,684 - 17,693 M-57C 14.1 PPG
3-Apr 17,321 - 17,835 14.5 233 bbls 17,723 - GeoTap 14.15 ppg (PP) 17,786 - 17,791 M-56A 13.1 PPG
3-Apr 17,835 - 17,909 14.34-Apr 17,909 - 18,195 14.3 12.58 @ 18,089 Schematic - 12.6 ppg at 18,066 18,061 - 18,223 M-56E 12.6 PPG
4-Apr 18,215 - 18,250 14.4 639 bbls
Lost full returns
5-Apr 18,260 14.0 1263 - Total
6-Apr 14.0 1586 - Total
7-Apr 14.0
8-Apr 14.0
9-Apr 18,360 14.0 called TD
Open Hole Interval below 9 7/8-in Liner @ 17,168 - FIT 15.98 PP 13.9
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ppgreservoirinthesameholesectionhadforcedourhand. Wehad
simplyrunoutofdrillingmargin.
C.
CasingProgram
Casingprogramsdescribethenumberandsizesofthecasingstringstobe
setinthewellboreandarebaseduponporepressureandfracturegradientplots.
Casingprogramsaredesignedbasedonanumberoffactors,includingburstand
collapsepressures,67tensilestrength,68drillbitsize,anticipatedhydrocarbon
flow,andhydrocarbontype. BPoriginallydesignedtheMacondowellto
includesevencasingstringstoreachthetargetwelldepth. However,basedon
theactualconditionsencounteredduringdrilling,BPusedninecasingstringsto
reachtotaldepth.
Conditionsencounteredduringdrillingcandrivechangesincasingprograms. Forexample,circulationlosseventsoccurredintheopenholesection
oftheMacondowell. Lostcirculationisthelossofdrillingfluids(suchas
drillingmudandspacer)intotheformation. Thislossofdrillingfluidis
observedduringthecirculationofdrillingfluids. Whenlessfluidisreturnedup
thewellannulusthanwaspumpedintothewellthroughthedrillstring,this
meansalossofdrillingfluidlostreturnshasoccurred. Theselostreturns
wereafactorinBPsdecisiontolimitthewelltotaldepthto18,360feet(shortof
the20,200feetoriginallyplanned)andalsoledBPtorevisethewellscasing
designprogram
to
account
for
mud
weight
and
fracture
gradient
drilling
margin
issues. Specifically,BPmodifieditscasingprogramseveraltimesbecauseof:(1)
awellcontroleventinMarch2010thatresultedinthedrillpipebecomingstuck;
(2)changesinporepressureestimates;and(3)wellballooning.69 AfterBP
reviseditscasingprogram,itsubmittedarevisedApplicationforPermittoDrill
toMMSforapproval.70
67Burstpressureisthetheoreticalinternalpressuredifferentialatwhichajointofcasingwillfail.
Collapsepressureisthepressureatwhichatubeorvesselwillcatastrophicallydeformasaresult
of
differential
pressure
between
the
outside
and
the
inside
of
the
tube
or
vessel.
Schlumberger
OilfieldGlossary.68Tensilestrengthistheforceperunitcrosssectionalarearequiredtopullasubstanceapart.
SchlumbergerOilfieldGlossary.69Ballooning,inwhichtheformationabsorbsdrillingmudwhiletherigspumpsareactivated
andthenreleasesthemudbackintothewellwhenthepumpsarenotactive,canbe
misinterpretedasakick.70MMSapproved:BPsApplicationforPermittoBypass,whichaddedanadditionalcasing
string,onMarch15,2010;BPsRevisedApplicationforPermittoBypass,whichaddedaliner,on
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D. MudProgramandType
Drillingmudprovideshydrostaticpressure pressureexertedbyafluid
atequilibriumduetotheforceofgravity topreventformationfluidsfrom
enteringthewellbore.Drillingmudalsokeepsthedrillbitcoolandcleanduring
drilling,carriesdrilledcuttingsoutofthewellandsuspendsthedrillcuttings
wheneverdrillingispaused.
Operatorshavemultipleoptionsforthetypeofmudtouseduringthe
drillingofawell,includingoilbasedmud,syntheticoilbasedmudandwater
basedmud. Dependingonreservoirconditions,operatorsassesswhichmud
typeismostappropriateforthespecificwellbeingdrilled.
FortheMacondowell,BPchoseasyntheticoilbasedinvertmudsystem,asysteminwhichsyntheticoilinthemudremainsinacontinuousfluidphasein
thelowerholesectionsofthewell. BPchosethissystemforseveralreasons:(1)
toenhancetheabilitytomaintainconsistentfluidpropertiesindependentofthe
temperatureandpressureconditionsofthewell;(2)toimproveholecleaning
andminimizebaritesag,controlofpressurespikes,andgaininggelstrengths;71
and(3)todealwithotherproblemsthatresultwhenbalancingequivalent
circulatingdensity(ECD).72 Inselectingthesyntheticoilbasedmud,BPalso
soughttoreducefluidlossinordertominimizeformationdamagewhile
maintaininga
higher
drilling
efficiency.
Syntheticoilbasedmud,suchasthetypeBPusedintheMacondowell,
hasmanypositivefeaturesasdescribedabove. However,thistypeofmudalso
presentsrisksrelatingtoitseffectonthecrewsabilitytoaccuratelydetect
naturalgasinflux(kicks)intothewell. Arecentstudyofdrillingfluidmixtures
andwellcontrolfoundthatdrillersmighthaveahardertimedetectingkicks
March26,2010;andBPsRevisedApplicationforPermittoBypass,whichincludedaproduction
casing,onApril15,2010.71
Society
of
Professional
Engineers,
SPE
116013
PA
Studyof
the
PVT
Properties
of
GasSynthetic
DrillingFluidMixturesAppliedtoWellControl(2009). Baritesagisthesettlingofbariteparticles
(orotherweightingmaterials),whichcanresultinfluctuationsindrillingfluiddensity. When
thisoccursindrillingmud,themudlosesitsintegrityandcanonlybeatemporarybarrierinthe
well. Gaining,orprogressive,gelstrengthstypicallyrequirehigherpumppressurestobreak
circulation.72ECDisthetotaleffectivepressurethatacolumnofdrillingmudexertsonaformationasthe
mudiscirculatedthroughthedrillstringandbackupthewellbore,accountingforfrictional
forcesthroughoutthecirculatorysystem.
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whenusingsyntheticoilbasedmud. Thestudystatedthatanimportantaspect
thatshouldbeaddressedwhendrillingwithasyntheticfluidisthepeculiarities
concernedwithwellcontrol. Becauseofthesolubilityofformationgasinoil
basedfluids,itcouldbecompletelydissolvedinthemudatbottomhole
temperatureandpressureconditions,makingkickdetectionverydifficult.73
ThePanelfoundnoevidencethatBPandMISWACOdiscussedwhether
theuseofsyntheticoilbasedmudwouldaffecttherigcrewsabilitytodetect
kicksduringdrillingoperationsatMacondo. Evenso,thePanelfoundno
evidencethatthespecificmudprogramusedbyBPandMISWACOwasacause
oftheblowout.
E. MudLosses
Throughout
the
drilling
of
the
Macondo
well,
BP
experienced
multiple
incidentswheremudwaslostintotheformation. Whilethelossofmudduring
drillingoperationsisnotuncommon,itisakeyindicatortodrillingengineers
thattheymustmonitorthewellcloselytoensurethatwellandformation
integrityarebeingmaintainedproperly. Abnormalpressurezonesidentifiedas
aresultofmudlosseventsoftenleaddrillingengineerstochangethewelldesign
andcasingsettingpoints.
BPdrilledtheMacondowelltoameasureddepthof18,360feet. Thecrew
seta97/8inchlinerinplaceat17,168feetmeasureddepthpriortodrillingthe
productionsection,whichwasthefinalsectionofthewell. Thelastsectionwasdifficulttodrillduetoadecreaseinthefracturegradientatthebottomofthe
wellbore. ThisconditionrequiredBPtocarefullyselectthecorrectmudweight
necessarytomaintainoverbalancerelativetotheformationwhileavoidingfluid
lossestothewell.
AccordingtoIADCdailyreports,thewellexperiencedmudlossesof
approximately3,000bblsacrossthehydrocarbonzonesofinterestduringthe
drillingoftheproductioncasingopenholesection. Thecrewcontrolledthese
losseswith
the
addition
of
lost
circulation
material
(LCM)
pills
and
a
relatively
smallquantity(lessthan200bbls)ofaspecialblendofdrillingfluid,whichhelp
retardthelossofmudintofracturesandhighlypermeableformations. Fromthe
timetheDeepwaterHorizonmovedontolocationatMacondo,atotalof
73Id.
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approximately15,500bblsofdrillingfluidswerelostduringdrilling,running
casingandcementingoperations.74
F.
WellBallooning
Wellballooningisacommonphenomenoninwhichtheformation
absorbsdrillingmudwhiletherigspumpsareactivatedandthenreleasesthe
mudbackintothewellwhenthepumpsarenotactive. Wellballooningis
significantbecauseitcanmimicakick. Rigcrewscanthereforemisscriticalkick
indicatorsiftheymistakenlybelievethatballooningisoccurringinthewell.
MudloggingdatafortheMacondowelldemonstratedthattheproduction
casingzonestartedballooningbetween17,530feetand17,761feet. Thedaily
IADCreportsalsoshowthatthewellflowedbackduringflowchecksfollowing
mudlossatthosedepths.
G.
PlannedandActualTotalDepth
Indesigningawell,engineerscalculateaplannedtotaldepthofthewell.
BPsFebruary2009ExplorationPlanestimatedthewelldepthatapproximately
20,200feettrueverticaldepth. Duetoanarroweddrillingmargin,BPultimately