Deepwater Horizon Accident Investigation 2
Investigation Context
Terms of Reference
Investigation Team
Data and Analysis
Investigation Limitations
Deepwater Horizon Accident Investigation 3
Well integrity was not established or failed− Annulus cement barrier did not isolate hydrocarbons
− Shoe track barriers did not isolate hydrocarbons
Hydrocarbons entered the well undetected and well control was lost− Negative pressure test was accepted although well
integrity had not been established
− Influx was not recognized until hydrocarbons were in riser
− Well control response actions failed to regain control of well
Hydrocarbons ignited on the Deepwater Horizon− Diversion to mud gas separator resulted in gas venting
onto rig
− Fire and gas system did not prevent hydrocarbon ignition
Blowout preventer did not seal the well− Blowout preventer (BOP) emergency mode did not
seal well
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2
3
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Sea Floor
Casing
Riser
BOP
Reservoir1
3
Eight Barriers Were Breached
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5
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Deepwater Horizon Accident Investigation 44
Sea Floor
Casing
Riser
BOP
Reservoir
12.6 ppg
Bottom Wiper Plug
Mud
14.17 ppg
Cap
16.74 ppg
Foam
Cement
14.5 ppg
Shoe
Track
Spacer
14.3 ppg
6.7 ppg
Spacer
14.3 ppg
Top Wiper Plug
Bottom Wiper PlugBottom Wiper Plug
Mud
14.17 ppg
Spacer
14.3 ppg
Top Wiper PlugTop Wiper Plug
Bottom Wiper Plug
Spacer14.3 ppg
16.74 ppg
CapCement
FoamCement14.5 ppg
CementChanneling
ShoeTrack
Nitrogen Breakout
Cement is pumped down the landing string and casing into the annulus to isolate hydrocarbon
bearing sands.
Foam slurry recommended was a complex design
Risk of contamination using small volume of cement
No fluid loss additives
Incomplete pre-job cement lab testing
Foam slurry was likely unstable and resulted in nitrogen breakout
Base Oil16.7 ppg
Cement Slurry Placement
Float Collar
Tail Cement16.74 ppg
Reamer Shoe Tail Cement
Key Finding #1The annulus cement barrier did not isolate the reservoir hydrocarbons
Centralizers
Deepwater Horizon Accident Investigation 55
Sea Floor
Casing
Riser
BOP
Reservoir
Key Finding #2The shoe track mechanical barriers did not isolate the hydrocarbons
Tail cement is displaced down the casing into the shoe track. The tail cement is
designed to prevent flow from the annulus into the casing. The float collar valves, which provide a second barrier, must close and seal to prevent flow up
the casing.
Shoe track had two types of mechanical barriers: cement in the shoe track and the double check valves in the float collar
Shoe track cement failed to act as a barrier due to contamination of the base slurry by break out of nitrogen from the foam slurry
Hydrocarbon influx was able to bypass the float collar check valves due to either:
Valves failed to convert orValves failed to seal
Flow through shoe confirmed by fluid modeling and Macondo static kill data
Float Collar
Check Valves
Flow Ports
Shoe track cement
Centralizers
Hydrocarbon Flow Path
Deepwater Horizon Accident Investigation 6
16ppg Spacer
14.17ppg SOBM (Mud)
8.6ppg Seawater
Influx
Flow Through Shoe Track - Supporting Evidence
CasingShoe
Failure
SealAssembly
FailureYY
YY
YY
YY
YY
YY
YY
YY
NN1400 psi recorded on drill pipe during negative test at 18:30
NNStatic Kill
NNTiming for Gas Arrival to Surface
NNPressure Response from 21:31 to 21:34
NNPressure Increase from 21:08 to 21:14
NNAbility to flow from 20:58
NNRealistic Net Pay Assumption
YYMechanical Barrier Failure Mode Identified
Key Observations for FlowThrough Shoe vs. Seal
Assembly
CasingShoe
Failure
SealAssembly
Failure
YY
YY
YY
YY
YY
YY
YY
YY
NN1400 psi recorded on drill pipe during negative test at 18:30
NNStatic Kill
NNTiming for Gas Arrival to Surface
NNPressure Response from 21:31 to 21:34
NNPressure Increase from 21:08 to 21:14
NNAbility to flow from 20:58
NNRealistic Net Pay Assumption
YYMechanical Barrier Failure Mode Identified
Key Observations for FlowThrough Shoe vs. Seal
Assembly
CasingShoe
Failure
SealAssembly
Failure
Deepwater Horizon Accident Investigation 77
Sea Floor
Shoe – 18,304’
FC – 18,115’
TOC – 17,260’
Shoe – 17,168’
KillChokeBoost
SOBM
Spacer
Seawater
Influx
SOBM
Spacer
Seawater
Influx
BOP
1400PSI
0PSI
Key Finding #3The negative pressure test was accepted although well integrity had not been established
Spacer
Sea Floor
Casing
Riser
BOP
Reservoir
Bleed volumes not recognized as a problem
Anomalous pressure on drill pipe with no flow from kill line
Test incorrectly accepted as successful
Negative testing not standardized
Deepwater Horizon Accident Investigation 88
Flow Indications
0
200
400
600
800
1000
1200
1400
1600
1800
2000
20:4
5
20:5
0
20:5
5
21:0
0
21:0
5
21:1
0
21:1
5
21:2
0
21:2
5
21:3
0
21:3
5
Flow
Rat
e (g
pm)
0
500
1000
1500
2000
2500
3000
Pum
p Pr
essu
re (p
si)
Flow Out (calibrated)Flow In (rig pumps)DP Press (rig pumps)
Key Finding #4The influx was not recognized until hydrocarbons were in the riser
Flow indications:
#1: Drill pipe pressure increased by 100 psi, (expected decreased); ~39 bbl gain from 20:58 to 21:08
#2: Drill pipe pressure increased by 246 psi with pumps off
– Flow out does not immediately drop after shutting down pump
#3: Drill pipe pressure increased by 556 psi with pumps off; ~300 bbl gain
No well control actions taken
21:08
1,017 psi
21:31
1,200 psi
SOBM (mud)
Seawater
Influx
SOBM + seawater mix
39 bbl
300bbl
Cumulative Gain
Indication #1
Indication #2
0 bbl
Indication #3
20:52-Flow starts
Based on Real-time Data
Deepwater Horizon Accident Investigation 99
0
500
1000
1500
2000
2500
3000
21:3
0
21:3
2
21:3
4
21:3
6
21:3
8
21:4
0
21:4
2
21:4
4
21:4
6
21:4
8
21:5
0
Drill Pipe Presssure (psi)
Pumps shut down
Discussion about “Differential Pressure”
Attempt to bleed pressure
Close Drill Pipe
Mud overflowing onto rig floor
BOP Sealing
Pressure increase due to annular activation
BOP
Key Finding #5Well control response actions failed to regain control of the well
Exp
losi
on
at
21:4
9
- Mud and water raining onto deck
- TP calls WSL, getting mud back, diverted to MGS, closed or was closing annular
- AD calls Senior TP, Well blowing out, TP is shutting it in now
Mud shoots up derrick-Diverter closed-BOP activated
First indication of well control response:49 minutes and 1000 bbls after initial influx
Influx enters riser
Annular leaking
Based on Real-time Data
Deepwater Horizon Accident Investigation 1010
Hydrocarbons were routed to the mud gas separator instead of diverting overboard
Resulted in rapid gas dispersion across the rig through the MGS vents and mud system
Key Finding #6Diversion to the mud gas separator resulted in gas venting onto the rig
When responding to a well control event the riser diverter is closed and fluids are sent to either the mud gas separator or
to the overboard diverter lines.
KillBoost
Choke
BOP
14” Diverter LinePort
Overboard 14” Diverter Line
MudSystem
Starboard Overboard
6” VacuumBreaker
IBOP
RotaryHose
Diverter
12” Vent
MGS
Bursting Disk
Starboard Overboard
OverboardCaisson
Slip Joint
Seawater
Seawater/Mud Mix
Influx
BOP Sealed at
21:47
Deepwater Horizon Accident Investigation 1111
Key Finding #7The fire and gas system did not prevent hydrocarbon ignition
Gas dispersion beyond electrically classified areas
Gas ingress into engine rooms via main deck air intakes
The on-line engines were one potential source of ignition
Aft
Fwd3D view
Aft
Aft
Gas Dispersion at 4 minutes
Fwd3D view
Section through derrick
(Upper Explosive Limit)
(Lower Explosive Limit)
Secondary protective systems are designed to reduce the potential
consequence of an event once the primary protective systems have
failed.
Deepwater Horizon Accident Investigation 1212
AMF
Key Finding #8The BOP emergency mode did not seal the well
EDS function was inoperable due to damage to MUX cables
AMF could not activate the BSR due to defects in both control pods
Auto-shear appears to have activated the BSR but did not seal the well
Potential weaknesses found in the BOP testing regime and maintenance management systems
The AMF provides an automatic means of closing the BSR without
crew intervention.
Manual Automatic ROV Intervention
EDSHP BSR Close
Emergency Methods of BOP Operation Available on DW Horizon
HOT StabAMF
Auto-shear
Damaged MUX Cable
Blue Control
Pod
Yellow Control
Pod
Damaged Hydraulic Conduit
Explosions & Fire:Loss of communicationLoss of electrical powerLoss of hydraulics
Deepwater Horizon Accident Investigation 13
Recommendations26 Recommendations Specific to the 8 Key Findings
BP Drilling Operating Practice and Management SystemsAugment existing Engineering Technical Practices and Procedures
Further Enhance Deepwater Capability and Proficiency
Strengthen Rig Audit Action Closeout and Verification
Introduce Integrity Performance Management for Drilling and Wells Activities
Contractor and Service Provider Oversight and AssuranceReview Cementing Services
Strengthen Drilling Contractor Well Control Practices and Proficiency
Introduce more rigorous oversight of Rig Safety Critical Equipment
Review minimum requirements for BOP Configuration and Capability
Redefine BOP Minimum Criteria for Testing, Maintenance, System Modifications and Performance Reliability
BP has accepted all the recommendations and is reviewing how best to implement across its world wide operations
Deepwater Horizon Accident Investigation 14
Well integrity was not established or failed− Annulus cement barrier did not isolate hydrocarbons
− Shoe track barriers did not isolate hydrocarbons
Hydrocarbons entered the well undetected and well control was lost− Negative pressure test was accepted although well
integrity had not been established
− Influx was not recognized until hydrocarbons were in riser
− Well control response actions failed to regain control of well
Hydrocarbons ignited on the Deepwater Horizon− Diversion to mud gas separator resulted in gas venting
onto rig
− Fire and gas system did not prevent hydrocarbon ignition
Blowout preventer did not seal the well− Blowout preventer (BOP) emergency mode did not
seal well
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2
3
4
4
5
Sea Floor
Casing
Riser
BOP
Reservoir1
3
Summary & Questions
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