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									Deepwater Horizon Investigation




                             Deepwater Horizon Accident Investigation   1
Investigation Context

   Terms of Reference


   Investigation Team


   Data and Analysis


   Investigation Limitations




                               Deepwater Horizon Accident Investigation   2
Eight Barriers Were Breached
                              Well integrity was not established or failed
            6             7     − Annulus cement barrier did not isolate hydrocarbons
                                1
                3     5
                                − Shoe track barriers did not isolate hydrocarbons
                                2


                              Hydrocarbons entered the well undetected and
        Riser
                  4             well control was lost
                                − Negative pressure test was accepted although well
                                3
              8
                                  integrity had not been established
            BOP
Sea Floor                       − Influx was not recognized until hydrocarbons were in
                                4
                                  riser
                                − Well control response actions failed to regain control of
                                5
       Casing
                                  well

                              Hydrocarbons ignited on the Deepwater Horizon
                                − Diversion to mud gas separator resulted in gas venting
                                6
                                  onto rig
                                − Fire and gas system did not prevent hydrocarbon
                                7
                                  ignition

                              Blowout preventer did not seal the well
                      1
     Reservoir                  − Blowout preventer (BOP) emergency mode did not
                                8
                                  seal well
                      2                                Deepwater Horizon Accident Investigation   3
     Introduction
Technical Presentation




                    Deepwater Horizon Accident Investigation   4
Well Integrity Was Not Established
              or Failed




                        Deepwater Horizon Accident Investigation   5
Production Casing Installation
                                                                   After drilling to total depth, casing is run to
                                                                   bottom in preparation for the cement job. A
     Choke
                                                                   double valve float collar is used to prevent
                                                    Kill
     Boost                                                          backflow or ingress of fluids through the
                                                                    shoe track until the cement hardens and
                                                                           creates a permanent barrier.
             BOP
                                                                       April 18th 00:30 – April 19th 19:30
Sea Floor                                         17:30 – 19:30      Long string design robust, consistent with
                                                Circulated prior
       Cement      36”                           to cement job       similar wells in the area
       Mud                                                           9 attempts made to establish circulation
                    28”

       Spacer
                                                                     to convert float valves
                     22”

                                                                     Circulate ~6 times open hole volume,
                     18”

                                                                     limited circulation due to concerns over
                          16”
                                                                     creating losses and hole washout
                     13-5/8”

                                                                     No evidence that hydrocarbons entered
                         11-7/8”
                                                                     the wellbore prior to the cementing
                          9-7/8”
                                                                     operation
    14.17 ppg
     SOBM


                                           Primary reservoir
                                                 sands
                                               (12.6 ppg)

                                   Bottoms–up
                                   Marker
                                                                         Deepwater Horizon Accident Investigation    6
Cement Job
                                                                                             Cement is pumped down casing through
                                                                                              the float collar and up the annulus to
                                                                                               isolate the primary reservoir sands.
     Choke                                    Pull out of hole
                                                        Kill                                     April 19th 19:30 – April 20th 07:00
     Boost                                     with running
                                               tool and drill                                 Nitrogen cement slurry chosen
                                                    pipe
                                                                                                 – To achieve light weight slurry due to
             BOP                                  Set and test                                     limited pore pressure / fracture
                                                 casing hanger
                                                 seal assembly
                                                                                                   gradient window
Sea Floor
                                                           00:35 – 02:50
                                                                                              Possible risk
                         36”                    Drill-Quip seal assembly installed               – Stability of foam
     Base Oil                                         and successfully tested.
                                                            Centralizer
                                                 No lock down sleeve installed.                  – Relatively small volume
     Spacer               28”

                                                           02:50 – 07:00                         – Susceptible to contamination
     Cap
                                                   Pull out hole with drill pipe.
     Cement                 22”                                                               Mitigation of risk by
     Foamed                  18”
                                                                                                 – Thorough testing of slurry design
     Cement
                                            Bottoms–up
                                16”         Marker                                               – Precise placement
     Tail Cement
     Mud                    13-5/8”                                                           Centralization
                                                   Primary
     Nitrogen                  11-7/8”
                                                  Reservoir                                      – 6 inline centralizers spaced across
     Breakout                                       Sands                                          the reservoir sands
                         Shoe – 17,168’
                                                  (12.6 ppg)
                                                  Top of
                                9-7/8”       cement 17,260’                                      – Additional centralizers not run
                                                                                                   because incorrectly thought to be
                                                                                                   wrong type
                                                                         Primary reservoir
                   Float Collar – 18,115’   6 centralizers                     sands             – Risk of channeling above reservoir
                                                                             (12.6 ppg)
                                                                                                   sands known and accepted
                         Shoe – 18,304’
                                                                                                 Deepwater Horizon Accident Investigation   7
Key Finding #1
The annulus cement barrier did not isolate the reservoir hydrocarbons
                                                                                             Cement is pumped down the
                                   Cement Slurry Placement                                landing string and casing into the
                                                              Base Oil
                                                               6.7
                                                                   ppg
                                                              16.7ppg
                                                                                           annulus to isolate hydrocarbon
                                                                                                   bearing sands.
                                                               Spacer
                                                              14.3 ppg
Riser                                                         14.3 ppg
                                                                Cap
                     Cement                   Mud
                   Channeling                                 16.74 ppg
                                                                                                 Foam slurry recommended was a
                                           14.17 ppg             Cap
                                                               Cement
                                                                                                 complex design
                                                              16.74 ppg


BOP
                                                                                                 Risk of contamination using small
Sea Floor                                                      Foam                              volume of cement
                                                              Cement
                                                               Foam
                                                              14.5 ppg
                                                              Cement                             No fluid loss additives
                                                              14.5 ppg
                                                                                                 Incomplete pre-job cement lab
Casing                                                                    Centralizers
                                             Spacer                                              testing
                                            14.3 ppg
                                                                                                 Foam slurry was likely unstable
                    Float Collar
                                            Top Wiper Plug
                                          Top Wiper Plug                                         and resulted in nitrogen breakout
                                          Bottom Wiper Plug
                                         Bottom Wiper Plug       Shoe

                   Tail Cement                                   Track
                    16.74 ppg                                                12.6 ppg    Shoe
                                                                                         Track




Reservoir          Reamer Shoe                                             Tail Cement


                 Nitrogen Breakout
                                                                                             Deepwater Horizon Accident Investigation   8
                    Cement Slurry Design Issues


                                       An independent lab completed over 500
                                       tests on a representative cement slurry and
                                       reported the following:

                                         50% quality foam at surface conditions
Original Height
                                         was not stable
                                         18.5% quality foam (downhole quality)
                                         was not stable
                                         Yield point of the Halliburton slurry was
                                         too low for the foam cement (2 lb / 100 ft2
 Final Height                            yield point at 135 deg F)
                                         Fluid loss for the base slurry was
                                         excessive compared to industry
                                         recommendations (302 cc versus 50 cc
                                         per 30 min)
 Cement

                                       Note: QUALITY = Nitrogen Volume /
                                         (Nitrogen + Base Slurry Volume)




        Unstable Foam Sample
                                            Deepwater Horizon Accident Investigation   9
Flow Through Shoe Track - Supporting Evidence

                          Casing    Key Observations for Flow Seal
                           Shoe      Through Shoe vs. Seal Assembly
                          Failure          Assembly           Failure

                           Y        Mechanical Barrier
                                    Failure Mode Identified       Y
                           Y
                                    Realistic Net Pay
                                    Assumption                    N
                           Y
                                    1400 psi recorded on
                                    drill pipe during negative    N
                                    test at 18:30

                           Y
                                    Ability to flow from
                                    20:58                         N
                           Y
                                    Pressure Increase from
                                    21:08 to 21:14                N
 16ppg Spacer              Y
                                    Pressure Response from
                                    21:31 to 21:34                N
 14.17ppg SOBM (Mud)
 8.6ppg Seawater
 Influx
                           Y
                                    Timing for Gas Arrival to
                                    Surface                       N
                                                                                                   Seal
                                                                  N
                Casing              Static Kill
                 Shoe
                Failure
                           Y                                                                     Assembly
                                                                                                  Failure




                                                                 Deepwater Horizon Accident Investigation 10
Key Finding #2
The 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,
     Riser
                                                      must close and seal to prevent flow up
                         Hydrocarbon Flow                            the casing.
                               Path
                                                       Shoe track had two types of mechanical
     BOP                 Float Collar
                                                       barriers: cement in the shoe track and the
    Sea Floor
                                                       double check valves in the float collar
                                                       Shoe track cement failed to act as a
                 Check Valves
     Casing                                            barrier due to contamination of the base
                                                       slurry by break out of nitrogen from the
                                                       foam slurry

                 Shoe track cement
                                                       Hydrocarbon influx was able to bypass
                                                       the float collar check valves due to either:
                                                             Valves failed to convert or
                                                             Valves failed to seal
                      Centralizers
                                                       Flow through shoe confirmed by fluid
                                                       modeling and Macondo static kill data

     Reservoir



                                        Flow Ports
                                                          Deepwater Horizon Accident Investigation 11
   Hydrocarbons Entered the Well
Undetected and Well Control Was Lost




                        Deepwater Horizon Accident Investigation 12
Casing (Positive) Pressure Test
                 2700
                  psi




                        Kill
                                                 A positive pressure test verifies the
                                                   integrity of the casing and seal
                                                              assembly.

                                                      April 20th 07:00 – 12:00
 Sea Floor
                                                 Casing was pressure tested to:

        Cement
                                                      250 psi (low)
        Mud                                           2700 psi (high)
        Spacer                                   Test successful
                                                 Proved integrity of blind shear rams, seal
                                                 assembly, casing and wiper plug
                                                 Test does not test the shoe track due to
                                                 presence of wiper plug




                                   Primary
                               reservoir sands


                                                    Deepwater Horizon Accident Investigation 13
Negative Pressure Test
                                                                  The negative-pressure test checks the
                                                                  integrity of the shoe track, casing and
                                                                 wellhead seal assembly. This simulates
     Choke
     Boost
                          Kill
                              15:04 – 15:56                            conditions during temporary
                         Seawater pumped into                    abandonment when a portion of the well
                       Boost, Choke, and Kill lines
                                                                         is displaced to seawater.
             BOP
                                                                        April 20th 15:04 – 19:55
                     16:54 - Close Annular

Sea Floor
                                                                   Negative test simulates underbalanced
                             15:56 – 16:53
                          424 bbls of 16 ppg
                                                                   condition
                     spacer followed by 30 bbls
       Cement        of freshwater and 352 bbls
                                                                   Spacer used between mud and seawater
                   of seawater pumped into well
       Mud                                                         Leaking annular at start of test moved
       Spacer         16:54 – 16:59                                spacer across kill line inlet
                    50 bbls bled off
       Seawater     drill pipe due to                              Negative test started on drill pipe but
       Influx       leaking annular                                changed to kill line
                                                                   Bleed volumes higher than calculated
                                                                   Drill pipe built pressure to 1400 psi with
                                                                   no flow on the kill line




                                             Primary reservoir
                                                   sands
                                                 (12.6 ppg)



                                                                      Deepwater Horizon Accident Investigation 14
Negative Pressure Test
                                                                                 The negative-pressure test checks the
  17:52 – 18:00                                                                  integrity of the shoe track, casing and
    Open kill
line to conduct                                                                 wellhead seal assembly. This simulates
       Choke
  negative test                         Kill                                          conditions during temporary
      Boost

                                             16:59 – 17:08                      abandonment when a portion of the well
Bled 3 - 15 bbls
  into kill line
                                          Annular seals with                            is displaced to seawater.
                                         increased hydraulic
              BOP
                                           closing pressure
 Flow did not                                                                          April 20th 15:04 – 19:55
   stop and
                                    Fill riser with 50 bbls of mud
  “spurted”                                                                       Negative test simulates underbalanced
 Sea Floor

Kill line closed
                                           17:08 – 17:27                          condition
                                         Monitored that the
        Cement
                                          annular sealed                          Spacer used between mud and seawater
        Mud                              17:27                                    Leaking annular at start of test moved
                                    Bled 15 bbls of                               spacer across kill line inlet
        Spacer
                                seawater from drill pipe
        Seawater                                                                  Negative test started on drill pipe but
                                  Decision made to
        Influx                  change test to kill line                          changed to kill line
                                                                                  Bleed volumes higher than calculated
             Cement
              Tank     Total
                                                                                  Drill pipe built pressure to 1400 psi with
                      Volume
                                                                                  no flow on the kill line

                      15 bbls




                                                            Primary reservoir
                                                                  sands
                                                                (12.6 ppg)



                                                                                     Deepwater Horizon Accident Investigation 15
Negative Pressure Test
                                                                                              The negative-pressure test checks the
                               1400       0                                                   integrity of the shoe track, casing and
                                psi      psi
                                                        18:00 – 18:35                        wellhead seal assembly. This simulates
     Choke                                     Drill pipe pressure gradually
     Boost                                         increased to 1400 psi
                                                                                                   conditions during temporary
                                                                                             abandonment when a portion of the well
                                                          18:42
                                                                                                     is displaced to seawater.
             BOP                                    Pumped into kill
                                                  line to confirm full                              April 20th 15:04 – 19:55
                                                 Kill line opened for
Sea Floor                                      monitoring negative test                        Negative test simulates underbalanced
                                                                                               condition

       Cement                                       18:42 – 19:55                              Spacer used between mud and seawater
                                            Monitored kill line for 30 min
       Mud                                 1400 psi on drill pipe described                    Leaking annular at start of test moved
                                               as a “bladder effect”                           spacer across kill line inlet
       Spacer
       Seawater                                         19:55
                                                Negative pressure test
                                                                                               Negative test started on drill pipe but
       Influx                                     was concluded and                            changed to kill line
                                                considered a good test
                                                                                               Bleed volumes higher than calculated
            Cement
             Tank     Total
                                                                                               Drill pipe built pressure to 1400 psi with
                     Volume
                                                                                               no flow on the kill line
                     18 bbls          Additional
                     15 bbls          3 bbl influx



                                                                         Primary reservoir
                                                                               sands
                                                                             (12.6 ppg)



                                                                                                  Deepwater Horizon Accident Investigation 16
Key Finding #3
The negative pressure test was accepted although well integrity had
not been established


                                                     1400    0
                                                      PSI   PSI
     Riser



                      Choke                                        Kill    Bleed volumes not recognized as a
                      Boost

                                                                           problem
     BOP
    Sea Floor

                              BOP
                                                                           Anomalous pressure on drill pipe with no
                 Sea Floor
                                                                           flow from kill line
                                                                  Spacer
     Casing         SOBM                                                   Test incorrectly accepted as successful
                    Spacer
                    Seawater                                               Negative testing not standardized
                    Influx




                                    Shoe – 17,168’


                                    TOC – 17,260’



                                      FC – 18,115’

     Reservoir

                                    Shoe – 18,304’

                                                                                Deepwater Horizon Accident Investigation 17
Well Monitoring – Driller’s Console and Mudlogging unit


                                  Well monitoring is performed to understand if
                                  the well has losses or gains

                                  Driller is responsible for monitoring and
                                  shutting in the well

                                  The mudlogger provides monitoring support to
                                  the driller

                                  Displays and trending capability available in
                                  both Driller’s and Mudlogger’s cabins

                                  Flow, pressure and pit sensors can indicate
                                  flow

                                  Simultaneous activities were taking place on
                                  April 20th to prepare for rig move

                                  Standards for monitoring do not specifically
                                  address end-of-well activities




                                           Deepwater Horizon Accident Investigation 18
Undetected Flowing Conditions
                                                                   Mud in the riser is displaced with
                                                                 seawater in preparation for temporary
                                                                            abandonment.
     Choke                 Kill

     Boost                         21:08
                         Spacer arrived at surface                        April 20th 19:55 – 21:14
                           Shut pumps down
                              for sheen test
             BOP                                                 20:02 Resume displacement of mud with
                                 20:02                           seawater
Sea Floor
                           Annular opened
                            after negative
                                  test
                                                                 20:52 Well becomes underbalanced and
                                                                 starts to flow
     Cement                     20:00 – 21:08
                           Resumed pumping
     Mud              Displaced riser with seawater              After 20:58 gain being taken and pressure
     Spacer              until spacer is at surface
                                                                 begins increasing
     Seawater
                                20:52                               – Flow from well masked by emptying
     Mud + Seawater   Well becomes underbalanced
                                                                      of trip tank
     Mix
     Influx                                                      21:08 Pumping stops for sheen test
                                                                    – Pressure increases with pump off
                         20:58 - 21:08
                          39 bbl gain                            21:14 Sheen test complete, displacement
                                                                 resumes

                                             Primary reservoir
                                                   sands
                                                 (12.6 ppg)



                                                                      Deepwater Horizon Accident Investigation 19
Key Finding #4
The influx was not recognized until hydrocarbons were in the riser
                  2000                                                                                                                              3000
                                                                                   Flow Indications
                                                                                   Based on Real-time Data                                                                       Flow indications:
                                                    Flow Out (calibrated)
                  1800
                                                    Flow In (rig pumps)
                                                    DP Press (rig pumps)
                                                                                                                                                    2500                               #1: Drill pipe pressure
                  1600
                                                                                                                                                                                       increased by 100 psi,
                                                          Decreasing trend should
                  1400                                                                                                                                                                 (expected decreased);




                                                                                                                                                           Pump Pressure (psi)
                                                              have continued                                                                        2000
                                                                                                                                                                                       ~39 bbl gain from 20:58
Flow Rate (gpm)




                  1200
                                                                       Indication #1                                                                                                   to 21:08
                  1000                                                                                                                              1500

                   800
                                                                                                                                                    1000
                   600

                   400
                                    20:52-Flow starts                                                                                               500
                   200

                  Cumulative Gain
                     0
                                                     0                                  39                                            300           0
                                                    bbl                                 bbl                                           bbl
                         20:45



                                            20:50



                                                            20:55



                                                                       21:00



                                                                                21:05



                                                                                              21:10



                                                                                                      21:15



                                                                                                              21:20



                                                                                                                      21:25



                                                                                                                              21:30



                                                                                                                                            21:35
                                                                    1,017 psi




                                 SOBM (mud)
                                 Seawater
                                 Influx
                                 SOBM + seawater mix



                                                          21:08



                                                                                                                                               Deepwater Horizon Accident Investigation 20
Key Finding #4
The influx was not recognized until hydrocarbons were in the riser
                  2000                                                                                                                                                                3000
                                                                                   Flow Indications
                                                                                   Based on Real-time Data                                                                                                         Flow indications:
                                                    Flow Out (calibrated)
                  1800
                                                    Flow In (rig pumps)
                                                    DP Press (rig pumps)
                                                                                                                                                                                      2500                               #1: Drill pipe pressure
                  1600
                                                                                                                                                                                                                         increased by 100 psi,
                                                          Decreasing trend should
                  1400                                                                                                                                                                                                   (expected decreased);




                                                                                                                                                                                             Pump Pressure (psi)
                                                              have continued                                                                                                          2000
                                                                                                                                                                                                                         ~39 bbl gain from 20:58
Flow Rate (gpm)




                  1200
                                                                    Indication #1                                                                                                                                        to 21:08
                  1000                                                                                                                                                                1500

                   800                                                                                                                                                                                                   #2: Drill pipe pressure
                                                                                                                              Indication #2                                                                              increased by 246 psi with
                                                                                                                                                                                      1000
                   600
                                                                                                                       Overboard line opened                                                                             pumps off
                   400
                                    20:52-Flow starts                                                                  Flow out available only
                                                                                                                                                                                      500
                                                                                                                         to driller after 21:10                                                                            – Flow out does not
                   200
                                                                                                                                                                                                                             immediately drop
                  Cumulative Gain                    0                                  39                                                                              300
                     0
                                                    bbl                                 bbl                                                                             bbl
                                                                                                                                                                                      0                                      after shutting down
                         20:45



                                            20:50



                                                            20:55



                                                                       21:00



                                                                                21:05



                                                                                              21:10



                                                                                                                          21:15



                                                                                                                                      21:20



                                                                                                                                                    21:25



                                                                                                                                                                21:30



                                                                                                                                                                              21:35
                                                                                                                                                                                                                             pump
                                                                    1,017 psi
                                                                                                   1200                       Normal Flow Back
                                                                                                   1000                                       Flow Out
                                                                                              Flow Rate (gpm)




                                                                                                                                              Flow In
                                                                                                                800
                                 SOBM (mud)
                                 Seawater
                                                                                                                600
                                 Influx
                                 SOBM + seawater mix
                                                                                                                400

                                                                                                                200
                                                          21:08
                                                                                                                  0
                                                                                                                      16:50


                                                                                                                                  16:55


                                                                                                                                                17:00


                                                                                                                                                            17:05




                                                                                                                                                                                 Deepwater Horizon Accident Investigation 21
Key Finding #4
The influx was not recognized until hydrocarbons were in the riser
                  2000                                                                                                                                                      3000
                                                                                   Flow Indications
                                                                                   Based on Real-time Data                                                                                               Flow indications:
                                                    Flow Out (calibrated)
                  1800
                                                    Flow In (rig pumps)
                                                    DP Press (rig pumps)
                                                                                                                                                                            2500                               #1: Drill pipe pressure
                  1600
                                                                                                                                                                                                               increased by 100 psi,
                  1400
                                                                                                                                                  Indication #3                                                (expected decreased);




                                                                                                                                                                                   Pump Pressure (psi)
                                                                                                                                                                            2000
                                                                                                                                                                                                               ~39 bbl gain from 20:58
Flow Rate (gpm)




                  1200
                                                                    Indication #1                                                                                                                              to 21:08
                  1000                                                                                                                                                      1500

                   800                                                                                                                                                                                         #2: Drill pipe pressure
                                                                                                               Indication #2                                                                                   increased by 246 psi with
                                                                                                                                                                            1000
                   600
                                                                                                                                                                                                               pumps off
                   400
                                    20:52-Flow starts                                                                                                                       500
                                                                                                                                                                                                                 – Flow out does not
                   200
                                                                                                                                                                                                                   immediately drop
                  Cumulative Gain                    0                                  39                                                                    300
                     0
                                                    bbl                                 bbl                                                                   bbl
                                                                                                                                                                            0                                      after shutting down
                         20:45



                                            20:50



                                                            20:55



                                                                       21:00



                                                                                21:05



                                                                                              21:10



                                                                                                              21:15



                                                                                                                                  21:20



                                                                                                                                          21:25



                                                                                                                                                      21:30



                                                                                                                                                                    21:35
                                                                                                                                                                                                                   pump
                                                                    1,017 psi                                         1,200 psi
                                                                                                                                                                                                               #3: Drill pipe pressure
                                                                                                                                                                                                               increased by 556 psi with
                                                                                                                                                                                                               pumps off; ~300 bbl gain

                                 SOBM (mud)
                                 Seawater
                                                                                                                                                                                                          No well control actions taken
                                 Influx
                                 SOBM + seawater mix



                                                          21:08                                       21:31



                                                                                                                                                                       Deepwater Horizon Accident Investigation 22
Key Finding #5
Well control response actions failed to regain control of the well

                                                                                                                                         Influx enters riser
 3000           Based on Real-time Data                                                         First indication of well control response:
                                                                                               49 minutes and 1000 bbls after initial influx
                   Drill Pipe Presssure (psi)
 2500                                                                                                                                              BOP
                                                                 Mud shoots up derrick
                          Attempt to bleed                         -Diverter closed
                              pressure                              -BOP activated
 2000




                                                                                                            Explosion at 21:49
                                                  Close Drill Pipe
                                                                                 BOP Sealing
 1500

                                                                             Annular
                  Discussion about                                           leaking
 1000           “Differential Pressure”
                                                                                          - Mud and water raining onto deck
                                 Mud overflowing
                                  onto rig floor                                         - TP calls WSL, getting mud back,
  500                                                                                      diverted to MGS, closed or was
                  Pumps shut down                                                          closing annular

                                              Pressure increase due                      - AD calls Senior TP, Well blowing
    0                                         to annular activation                        out, TP is shutting it in now
        21:30

                  21:32

                             21:34

                                      21:36

                                                21:38

                                                         21:40

                                                                     21:42

                                                                               21:44

                                                                                       21:46

                                                                                                    21:48

                                                                                                                                 21:50


                                                                                                                            Deepwater Horizon Accident Investigation 23
Hydrocarbons Ignited on the
    Deepwater Horizon




                    Deepwater Horizon Accident Investigation 24
Diverting to the Mud Gas Separator at about 21:42
                                                                   12” Vent                    When responding to a well control event
                                                                                                the riser diverter is closed and fluids
                          6” Vacuum
                             Breaker                                                           sent to either the mud gas separator or
                                                            Bursting Disk                          to the overboard diverter lines.


                                                                                               Diversion to the MGS
                                                          MGS             Rated to 60 psi
                                                                          working pressure      Rig crew has the option to divert flow to
                                      Rotary
                                      Hose
     Mud                                                                                        port/starboard overboard lines or the
    System                             IBOP
                                                                                                MGS
                                                                                   Starboard
                                  Diverter                                         Overboard    Diverting to port or starboard will result in
                                                                                   Starboard
                                                                                                fluids venting overboard
     Port
Overboard          14” Diverter Line                        14” Diverter Line      Overboard

                                             Slip Joint         Rated to 100 or 500 psi         Liquid outlet from MGS goes to the Mud
              Overboard
               Caisson    Boost                             Kill
                                                                                                System under the main deck
                          Choke

                           BOP




     Seawater
     Seawater/Mud Mix
     Influx




                                                                                                    Deepwater Horizon Accident Investigation 25
Gas flow to Surface at high rate: 21:46 to 22:00
                                                                   12” Vent                 When responding to a well control event
                                                                                             the riser diverter is closed and fluids
                          6” Vacuum
                             Breaker                                                        sent to either the mud gas separator or
                                                            Bursting Disk                       to the overboard diverter lines.


                                                                                            Hydrocarbon flow from surface
                                                          MGS
                                                                                             equipment
                                      Rotary
                                      Hose
     Mud
                                                                                             Instantaneous gas rates reached
    System                             IBOP
                                                                                             165 mmscfd
                                                                                Starboard
                                  Diverter
                                                                                Overboard    Pressures exceeded operating ratings
                                                                                             (above 100 psi)
     Port                                                                       Starboard
Overboard          14” Diverter Line                        14” Diverter Line   Overboard
                                                                                             Gas would probably have vented from:
                                             Slip Joint
              Overboard
               Caisson    Boost                             Kill                                  Slip joint packer into the moon pool
                          Choke                                                                   12” MGS “gooseneck” vent
                           BOP
                                                                                                  6” MGS vacuum breaker vent
                                                                                                  6” overboard line through burst disk
     Seawater
                                                                                                  10” mud line under the main deck
     Seawater/Mud Mix
     Influx




                                                                                                 Deepwater Horizon Accident Investigation 26
Gas Dispersion across the Deepwater Horizon 21:46 to 21:50 hrs


                        Animation of Gas Dispersion



                         Upper Explosive Limit




                         Lower Explosive Limit

              3D View                            Cut Section Through Derrick Towards Aft




                                                           Deepwater Horizon Accident Investigation 27
Secondary protective systems did not prevent ignition
                                              Secondary protective systems are
                                               designed to reduce the potential
                                              consequence of an event once the
 3D view                                   primary protective systems have failed.

                           Fwd




Aft

Secondary Protective Systems
 Gas cloud reached the supply air
 intakes for engine rooms 3, 4, 5 & 6
 The Fire and Gas system did not
 automatically trigger a shutdown of the
 HVAC system for the engine rooms
 Limited areas of the rig are designated
 as electrically classified zones


                                               Deepwater Horizon Accident Investigation 28
Key Finding #6
Diversion to the mud gas separator resulted in gas venting onto the
                                                                  12” Vent
rig
                            6” Vacuum
                               Breaker                                                     When responding to a well control event
                                                          Bursting Disk                    the riser diverter is closed and fluids are
                                                                                            sent to either the mud gas separator or
                                                                                                to the overboard diverter lines.
                                                         MGS

                                     Rotary
                                     Hose                                                   Hydrocarbons were routed to the mud gas
       Mud
      System                          IBOP                                                  separator instead of diverting overboard
                                                                               Starboard    Resulted in rapid gas dispersion across
                                 Diverter                                      Overboard
                                                                                            the rig through the MGS vents and mud
                                                                                            system
       Port                                                                    Starboard
  Overboard          14” Diverter Line                     14” Diverter Line   Overboard

                                            Slip Joint
                Overboard
                 Caisson     Boost                         Kill


                            Choke

                             BOP

                                                                     BOP
                                                                   Sealed at
       Seawater                                                     21:47
       Seawater/Mud Mix
       Influx




                                                                                                Deepwater Horizon Accident Investigation 29
Key Finding #7
The fire and gas system did not prevent hydrocarbon ignition
 Gas Dispersion at 4 minutes
                                                Secondary protective systems are
                                                 designed to reduce the potential
       (Upper Explosive Limit)                  consequence of an event once the
                                                 primary protective systems have
                                          Aft                 failed.
                                                Gas dispersion beyond electrically
                                                classified areas
        Section through derrick
      3D view                                   Gas ingress into engine rooms via main
        (Lower Explosive Limit)
                                        Fwd
                                                deck air intakes

                                                The on-line engines were one potential
                                                source of ignition



                                  Fwd
   3D view
        Aft


    Aft

                                                    Deepwater Horizon Accident Investigation 30
Emergency Well Control System
    Did Not Seal the Well




                     Deepwater Horizon Accident Investigation 31
Blowout Preventer (BOP)
 BOP Control Panel


                                                         Surface HPU &
                                                         Accumulators              Flex Joint                              LMRP
                                                                               Upper Annular


                                                                                Lower Annular
                                                                            Stripping Element
                                     Mux Cable
                                     Hydraulic Conduit
                                                               LMRP
                                                            Accumulators

                                                                            Blind Shear Ram
                      Blue             Yellow
                     Control           Control
                                                                           Casing Shear Ram
                      Pod               Pod                                     (Non Sealing)
                                                                                  Upper VBR

                                                            Lower Stack          Middle VBR
                                                            Accumulators    Lower (Test) VBR
                                                                                                                           BOP
                                                                                                                           Stack
  Emergency Methods of BOP Operation Available on DW Horizon                         Wellhead Connector

         Manual                Automatic         ROV Intervention
                                                                                                     Wellhead
                                                   HOT Stab
         EDS
                                 AMF                  AMF                                  Sea Bed
     HP BSR Close
                                                   Auto-shear
                                                                                       Deepwater Horizon Accident Investigation 32
BOP Response (Before the Explosions)
                                                                BOP is designed to seal the wellbore and
                                                   20th
                                               April             shear casing or drill pipe if necessary.
                                         21:38 – Hydrocarbons
                                             enter the riser
                                                                April 20th
                                                                  21:41 annular BOP closed but appears
                                             Activation of
   Upper Annular
                                          Lower Annular BOP       not to have sealed the annulus

    Lower Annular
                                                                  21:47 a VBR likely closed and sealed the
Stripping Element
                                                                  annulus




 Blind Shear Ram

Casing Shear Ram                           Activation of VBR
     (Non Sealing)

       Upper VBR


      Middle VBR

Lower (Test) VBR




                Wellhead Connector




                              Wellhead



               Sea Bed                                                   Deepwater Horizon Accident Investigation 33
 BOP Response (Impact of Explosions)
                                                               MUX cables provide electronic
                                                            communication and electrical power to
                                                                  the BOP control pods.

                                                           April 20th
                                                             Damage to MUX cables and hydraulic line
    Upper Annular

                                                                – Opening of annular BOP
     Lower Annular
                                          Annular BOP
 Stripping Element                       gradually opens
                                                             Rig drifted off location
                                                                – Upward movement of the drill pipe in
                                                                  the BOP
 Blind Shear Ram

Casing Shear Ram
     (Non Sealing)

       Upper VBR


      Middle VBR

 Lower (Test) VBR




                Wellhead Connector




                              Wellhead



               Sea Bed                                                  Deepwater Horizon Accident Investigation 34
 BOP Response (After the Explosions)
                                                            There are several emergency methods of
                                                              activating the BSR to seal the well.

                                                            April 20th
                                                              EDS attempts failed to activate BSR
    Upper Annular
                                                              AMF sequence likely failed to activate BSR

     Lower Annular
                                                            April 21st – 22nd
 Stripping Element

                                         BSR activated by     ROV hot stab attempts to close BOP were
                                           Auto-shear
                                                              ineffective
                                                              ROV simulated AMF function likely failed to
 Blind Shear Ram                                              activate BSR
Casing Shear Ram
     (Non Sealing)                                            ROV activated auto-shear appears to have
       Upper VBR
                                                              activated but did not seal the well
      Middle VBR
                                                            April 25th – May 5th
 Lower (Test) VBR
                                                              Further ROV attempts using seabed
                                                              deployed accumulators were unsuccessful
                Wellhead Connector




                              Wellhead



               Sea Bed                                               Deepwater Horizon Accident Investigation 35
Key Finding #8
The BOP emergency mode did not seal the well
Explosions & Fire:                                                   The AMF provides an automatic
Loss of communication                                               means of closing the BSR without
Loss of electrical power                                                   crew intervention.
Loss of hydraulics

                                                                    EDS function was inoperable due to
                                        Damaged Hydraulic Conduit
                                                                    damage to MUX cables

                                      Damaged MUX Cable             AMF could not activate the BSR due to
                                                                    defects in both control pods

                                                                    Auto-shear appears to have activated
                     Blue             Yellow                        the BSR but did not seal the well
                    Control           Control
                     Pod               Pod
                                                                    Potential weaknesses found in the
                                                                    BOP testing regime and maintenance
                                                                    management systems


  Emergency Methods of BOP Operation Available on DW Horizon

        Manual                Automatic         ROV Intervention

                                                  HOT Stab
        EDS
                                AMF                  AMF
    HP BSR Close
                                                  Auto-shear
                                                                        Deepwater Horizon Accident Investigation 36
Summary of Findings and
  Recommendations




                Deepwater Horizon Accident Investigation 37
Recommendations
 25 Recommendations Specific to the 8 Key Findings


 BP Drilling Operating Practice and Management Systems
        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 Assurance
        Cementing Services
        Drilling Contractor Well Control Practices and Proficiency
        Oversight of Rig Safety Critical Equipment
        BOP Configuration and Capability
        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 38
                          Summary of Key Findings
                                 Well integrity was not established or failed
            6             7        − Annulus cement barrier did not isolate hydrocarbons
                                   1
                3     5
                                   − Shoe track barriers did not isolate hydrocarbons
                                   2


                                 Hydrocarbons entered the well undetected and
        Riser
                  4                well control was lost
                                   − Negative pressure test was accepted although well
                                   3
              8
                                     integrity had not been established
            BOP
Sea Floor                          − Influx was not recognized until hydrocarbons were in
                                   4
                                     riser
                                   − Well control response actions failed to regain control of
                                   5
       Casing
                                     well

                                 Hydrocarbons ignited on the Deepwater Horizon
                                   − Diversion to mud gas separator resulted in gas venting
                                   6
                                     onto rig
                                   − Fire and gas system did not prevent hydrocarbon
                                   7
                                     ignition

                                 Blowout preventer did not seal the well
                      1
     Reservoir                     − Blowout preventer (BOP) emergency modes did not
                                   8
                                     seal well
                      2                                   Deepwater Horizon Accident Investigation 39

								
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