Deepwater accident timeline
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Chronology of the accidentKey events in bold
Start dateEnd dateStart timeEnd timePlace in sequenceDescriptionSource
6-Oct-2006Events Prior to April 19, 2010Spudded Macondo well with Transocean’s Marianas.OpenWells®
8-Nov-200927-Nov-2009Events Prior to April 19, 2011Pulled riser and evacuated Marianas for Hurricane Ida. Marianas subsequently damaged and moved to safe harbor for repairs.OpenWells®
31-Jan-20106-Feb-2010Events Prior to April 19, 2012Transocean’s Deepwater Horizon on location to replace Marianas. Six days of pre-job maintenance and testing of blowout preventer (BOP) followed. Drilling activities recommenced on February 6.OpenWells®
23-Feb-201013-Mar-2010Events Prior to April 19, 2013Pilot valve leak of 1 gpm noticed on yellow pod of BOP; leak reduced after switching to blue pod.OpenWells®
8-Mar-2010Events Prior to April 19, 2014Well control event at 13,305 ft. Pipe stuck; severed pipe at 12,146 ft.OpenWells®
12-Mar-201022-Mar-2010Events Prior to April 19, 2015Contingency liner utilized, a new drilling liner was added and production casing changed to a 9 7/8 in. x 7 in. long string. Minerals Management Service (MMS) approved changes.Macondo well plan MMS applications
5-Apr-20106-Apr-2010Events Prior to April 19, 2016Stripped drill pipe through upper annular preventer from 17,146 ft. to 14,937 ft. while addressing wellbore losses.OpenWells®
9-Apr-201014-Apr-2010Events Prior to April 19, 2017Total depth of 18,360 ft. reached and data collected for five days. Reservoir sands contained hydrocarbons at pressures of approximately 11,850 psi.OpenWells®
14-Apr-2010Events Prior to April 19, 2018Halliburton OptiCem™ cement model review concluded zonal isolation objectives could be met using 9 7/8 in. x 7 in. long string as production casing. Halliburton 9 7/8 in. x 7 in.Production Casing Design Report
15-Apr-2010Events Prior to April 19, 2019OptiCem™ model updated with open hole caliper and survey data. Input included 21 centralizers and 70% standoff above the top centralizer.Company emails
15-Apr-2010Events Prior to April 19, 2020Decision made to order 15 additional centralizers. Order placed.Company emails
16-Apr-201011:51Events Prior to April 19, 2021Fifteen slip-on bow spring centralizers delivered to rig by helicopter.OpenWells®
16-Apr-201012:4812:53Events Prior to April 19, 2022Mechanical integrity concerns regarding the bow spring centralizers. Decision made not to run bow spring centralizers.Company emails Interviews
18-Apr-201020:58Events Prior to April 19, 2023Partial lab test results, a new OptiCem™ model report (using seven inline centralizers) and Halliburton’s cementing recommended procedure for the Macondo well cement job were provided to BP and Halliburton staff. [Complete lab test results on planned slurry design not provided to BP before job was pumped.]Email from Halliburton inhouse cementing engineer to BP and Halliburton staff
19-Apr-201013:30Final Casing Run Completed final (production) casing run to 18,304 ft. (job took 37 hours). The shoe track included a Weatherford float collar installed at the top and a reamer shoe at the bottom.OpenWells®
19-Apr-201014:3016:20Final Casing Run Nine attempts made to establish circulation. Circulation established with 3,142 psi.OpenWells® Real-time data
19-Apr-201016:2019:30Final Casing Run Circulation pressure of 340 psi did not match modeling results of 570 psi.OpenWells®
19-Apr-201020-Apr-201019:300:36Cement Job Cement job pumped as planned with full fluid returns observed. Bottom plug burst disk ruptured at higher-than-planned pressure, 2,900 psi. Cement job completed; bumped top wiper plug at 00:36:00 hours.OpenWells® Real-time data
20-Apr-20100:40Cement Job Bled off 5 bbls of fluid to reduce drill pipe pressure from 1,150 psi to 0 psi. No flow observed after bleeding 5 bbls.Real-time data OpenWells®
20-Apr-20100:407:00Cement Job Dril-Quip seal assembly installed in subsea wellhead. Two pressure tests successfully completed. Drill pipe pulled out of riser.Real-time data OpenWells® Interviews
20-Apr-20107:30Cement Job BP and service providers discussed running cement bond log (CBL) during morning operations call. Decision made, in accordance with pre-established BP Macondo well team decision tree, not to run CBL.Interviews
20-Apr-201010:5512:00Positive-pressure and Negative-pressure Tests Successful positive-pressure test of the production casing.Real-time data Interviews
20-Apr-201012:0015:04Positive-pressure and Negative-pressure Tests Drill pipe run in hole to 8,367 ft. Displacement procedure reviewed in preparation for mud displacement and negative-pressure test. At 13:28 hours, Deepwater Horizon started offloading mud to M/V Damon Bankston. Mudlogger told assistant driller that pit levels could not be monitored during offloading. Assistant driller told mudlogger that notice would be provided when offloading to M/V Damon Bankston ceased.Real-time data M/V Damon Bankston log Interviews
20-Apr-201015:0415:56Positive-pressure and Negative-pressure Tests Seawater pumped into boost, choke and kill lines to displace mud. 1,200 psi left trapped in the kill line (i.e., not bled off).Real-time data
20-Apr-201015:5616:53Positive-pressure and Negative-pressure Tests A total of 424 bbls of 16 ppg spacer followed by 30 bbls of freshwater pumped into well. Displacement completed with 352 bbls of seawater, placing the spacer 12 ft. above the BOP. [From ~16:00 hours–17:50 hours, trip tank was being cleaned. Recorded flow data unreliable during this period.] Real-time data M-I SWACO displacement procedure
20-Apr-201016:54Positive-pressure and Negative-pressure Tests Upon shutting down pumps, drill pipe pressure was at 2,325 psi. Pressure in kill line remained at 1,200 psi. An annular preventer was closed for the negative-pressure test.Real-time data Interviews
20-Apr-201016:5416:56Positive-pressure and Negative-pressure Tests Drill pipe pressure bled from 2,325 psi down to 1,220 psi in order to equalize with the 1,200 psi on the kill line.Real-time data
20-Apr-201016:5716:59Positive-pressure and Negative-pressure Tests Kill line opened and pressure decreased to 645 psi; drill pipe pressure increased to 1,350 psi. Attempt made to bleed system down to 0 psi. Drill pipe pressure decreased to 273 psi. Kill line pressure decreased to 0 psi. Kill line shut in.Real-time data Interviews
20-Apr-201016:5917:08Positive-pressure and Negative-pressure Tests At 16:59:00 hours, drill pipe pressure increased from 273 psi to 1,250 psi in 6 minutes. Annular preventer closing pressure was increased from 1,500 psi to 1,900 psi to create a seal. The riser was topped up with approximately 50 bbls of mud from the trip tank to replace the volume bled off through the drill pipe. [Spacer fluid was then across the BOP.] Real-time data MBI testimony
20-Apr-201017:0817:27Positive-pressure and Negative-pressure Tests Drill pipe pressure decreased from 1,250 psi to 1,205 psi.Real-time data
20-Apr-201017:17Positive-pressure and Negative-pressure Tests Mud offloading from Deepwater Horizon mud pits to M/V Damon Bankston ceased. Mudlogger not notified.M/V Damon Bankston log Interviews
20-Apr-201017:2717:52Positive-pressure and Negative-pressure Tests Drill pipe pressure reduced from 1,205 psi to 0 psi by bleeding off 15 bbls to 23 bbls of fluid to the cement unit. Rig crew and well site leader discussed negative-pressure test procedure. Well site leader stated the negative-pressure test needed to be done on the kill line in accordance with the BP plan submitted to MMS.Real-time data Interviews
20-Apr-201017:5218:00Positive-pressure and Negative-pressure Tests Kill line opened to the cement unit. Cementer bled off 3 bbls to 15 bbls of seawater. A witness reported continuous flow from the kill line that spurted and was still flowing when instructed to shut in the line.Real-time data Interviews
20-Apr-201018:0018:35Positive-pressure and Negative-pressure Tests Drill pipe pressure gradually increased to 1,400 psi over 35 minutes. Build profile showed distinct pressure fluctuations at fairly uniform intervals.Real-time data
20-Apr-201018:3519:55Positive-pressure and Negative-pressure Tests Discussion ensued about pressure anomalies and negative-pressure test procedure. Seawater pumped into the kill line to confirm it was full. Opened kill line and bled 0.2 bbl to mini trip tank; flow stopped. Kill line opened and monitored for 30 minutes with no flow. At19:55:00 hours, the negative-pressure test was concluded and considered a good test.Real-time data Interviews
20-Apr-201020:00Well Monitoring and Simultaneous Operations Internal blowout preventer (IBOP) and annular preventer opened and pumping of seawater commenced down the drill pipe to displace mud and spacer from the riser.Real-time data
20-Apr-201020:50Well Monitoring and Simultaneous Operations Pumps slowed for the spacer arriving at surface.Real-time data
20-Apr-201020:52Well Monitoring and Simultaneous Operations [Calculated that the well went underbalanced and started to flow.]OLGA® model
20-Apr-201020:5821:08Well Monitoring and Simultaneous Operations Flow out from the well increased. Trip tank was emptied into the flow-line at this time. [Taking into account the emptying of the trip tank, calculated a gain of approximately 39 bbls over this period.]Real-time data Calculations
20-Apr-201021:0121:08Well Monitoring and Simultaneous Operations Drill pipe pressure increased from 1,250 psi to 1,350 psi at constant pump rate.Real-time data
20-Apr-201021:08Well Monitoring and Simultaneous Operations Spacer observed at surface. Pumps shut down to enable sheen test to be conducted.Real-time data Interviews
20-Apr-201021:08-21:14Well Monitoring and Simultaneous Operations With pumps off, drill pipe pressure increased from 1,017 psi to 1,263 psi in 5 1/2 minutes. Overboard dump line opened during sheen test; Sperry-Sun flow meter bypassed. Successful result from visual sheen test indicated that fluids could be discharged overboard. [OLGA® well flow modeling calculated that in-flow to the well during this period was approximately 9 bbls/min.]Real-time data Interviews Deepwater Horizon P&IDs OLGA® model
20-Apr-201021:14-21:31Well Monitoring and Simultaneous Operations Pumps restarted to continue displacement. Displaced well fluids discharged overboard. Drill pipe pressure on continually increasing trend.Real-time data Interviews
20-Apr-201021:17Well Monitoring and Simultaneous Operations Pump #2 started and pressure spiked to 6,000 psi. [Inferred that the pump likely started against a closed valve and the pressure lifted the relief valve.]Real-time data MBI testimony
20-Apr-201021:18Well Monitoring and Simultaneous Operations Pumps #2, #3 and #4 were shut down. Pump #1 stayed online (boost line).Real-time data
20-Apr-201021:1821:20Well Monitoring and Simultaneous Operations Toolpusher was called to rig floor.Interviews
20-Apr-201021:20Well Monitoring and Simultaneous Operations Assistant driller was called to either the pit room or the pump room.Interviews MBI testimony
20-Apr-201021:20Well Monitoring and Simultaneous Operations Senior toolpusher called toolpusher and asked how the negative-pressure test had gone. Toolpusher responded that the test result was “good,” and the displacement was “going fine.”MBI testimony
20-Apr-201021:20-21:27Well Monitoring and Simultaneous Operations Pumps #3 and #4 restarted. Some pressure started to build on pump #2, reaching 800 psi at 21:27:00 hours.Real-time data
20-Apr-201021:26-21:30Well Monitoring and Simultaneous Operations Drill pipe pressure declined by 400 psi at constant pump rate.Real-time data
20-Apr-201021:30Well Monitoring and Simultaneous Operations [Calculated that the spacer was fully displaced from the riser.]Real-time data OLGA® model
20-Apr-201021:31Well Control Response Pumps shut down; first pumps #3 and #4, then #1 (boost pump).Real-time data
20-Apr-201021:3121:34Well Control Response Drill pipe pressure increased from 1,210 psi to 1,766 psi. ~21:33 hours, chief mate observed toolpusher and driller discussing “differential pressure.” Toolpusher told chief mate that cement job may be delayed.Real-time data MBI testimony
20-Apr-201021:3621:38Well Control Response Over a 90-second period, drill pipe pressure decreased from 1,782 psi to 714 psi and then increased from 714 psi to 1,353 psi. [Inferred to have been caused by opening and closing a 4 in. valve on the standpipe manifold.]Real-time data OLGA® model
20-Apr-201021:38Well Control Response [Calculated that at approximately 21:38, hydrocarbons passed from well into riser.]OLGA® model
20-Apr-201021:3821:42Well Control Response Drill pipe pressure held briefly, then decreased steadily from 1,400 psi to 338 psi.Real-time data
20-Apr-201021:4021:48Well Control Response Chief electrician de-isolated pump #2. Chief electrician observed four personnel (including the assistant driller) completing repair of the pressure relief valve on pump #2 at the time he left the area (~21:48 hours)MBI testimony
20-Apr-201021:40Well Control Response ~21:40 hours—Mud overflowed the flow-line and onto rig floor. ~21:41 hours—Mud shot up through derrick.Real-time data Interviews MBI testimony
20-Apr-201021:41Well Control Response ~21:41 hours—Diverter closed and flow routed to mud gas separator (MGS); BOP activated (believed to be lower annular preventer). [Drill pipe pressure started increasing in response to BOP activation.] Real-time data Interviews MBI testimony
20-Apr-201021:42Well Control Response ~21:42 hours—Diverter closed and flow routed to mud gas separator (MGS); BOP activated (believed to be lower annular preventer). [Drill pipe pressure started increasing in response to BOP activation.] Real-time data Interviews MBI testimony
20-Apr-201021:42Well Control Response ~21:42 hours—M/V Damon Bankston was advised by Deepwater Horizon bridge to stand off 500 m because of a problem with the well. The ship began to move away.Real-time data Interviews MBI testimony
20-Apr-201021:42Well Control Response ~21:42 hours—Drill pipe pressure increased steadily from 338 psi to 1,200 psi over 5-minute period. Real-time data Interviews MBI testimony
20-Apr-201021:44Well Control Response ~21:44 hours—Mud and water exited MGS vents; mud rained down on rig and M/V Damon Bankston as it pulled away from rig. Real-time data Interviews MBI testimony
20-Apr-201021:44Well Control Response ~21:44 hours—Toolpusher called well site leader and stated they were “getting mud back” and that they had “diverted to the mud gas separator” and had either closed or were closing the annular preventer.Real-time data Interviews MBI testimony
20-Apr-201021:45Well Control Response ~21:45 hours—Assistant driller called the senior toolpusher to report that “The well is blowing out . . . [the toolpusher] is shutting it in now.” Real-time data Interviews MBI testimony
20-Apr-201021:46Well Control Response ~21:46 hours—Gas hissing noise heard and high-pressure gas discharged from MGS vents towards deck. Real-time data Interviews MBI testimony
20-Apr-201021:47Well Control Response ~21:47 hours—First gas alarm sounded. Gas rapidly dispersed, setting off other gas alarms. Real-time data Interviews MBI testimony
20-Apr-201021:47Well Control Response ~21:47 hours—Roaring noise heard and vibration felt.Real-time data Interviews MBI testimony
20-Apr-201021:47Well Control Response ~21:47 hours—Drill pipe pressure started rapidly increasing from 1,200 psi to 5,730 psi. [This is thought to have been the BOP sealing around pipe. Possible activation of variable bore rams [VBRs] at 21:46:00 hours.] Real-time data Interviews MBI testimony
20-Apr-201021:48Well Control Response ~21:48 hours—Main power generation engines started going into overspeed (#3 and #6 were online).Real-time data Interviews MBI testimony
20-Apr-201021:49Explosion and Fire Rig power lost. Sperry-Sun real-time data transmission lost. First explosion occurred an estimated 5 seconds after power loss. Second explosion occurred an estimated 10 seconds after first explosion.Real-time data Interviews MBI testimony
20-Apr-201021:52Explosion and Fire Mayday call made by Deepwater Horizon.M/V Damon Bankston log
20-Apr-201021:5221:57Explosion and Fire Subsea supervisor attempted to activate emergency disconnect sequence (EDS) for the BOP at the panel on the bridge. Lights changed on panel, but no flow was observed on the flow meter. Lower marine riser package did not unlatch. Deepwater Horizon master announced the activation of the EDS at 21:56MBI testimony Interviews
20-Apr-201022:0023:22Explosion and Fire Transfer of 115 personnel, including 17 injured, to M/V Damon Bankston. 11 people were determined to be missing, and search and rescue activities ensued. U.S. Coast Guard arrived on-site at 23:22 hours.MBI testimony
22-Apr-201010:22Explosion and Fire Deepwater Horizon sank.Unified Command
23-Apr-201017:00Explosion and Fire The search for the 11 missing people was suspended.Unified Command
21-Apr-201022-Apr-201018:001:15BOP Emergency Operations Remotely operated vehicle (ROV) operations were initiated. ROV attempted hot stab interventions to close VBRs and blind shear rams (BSRs); ROV attempts were ineffective.IMT reports
22-Apr-20102:45BOP Emergency Operations ROV simulated automatic mode function AMF in an attempt to activate BSR. Well continued to flow.IMT reports
22-Apr-20107:40BOP Emergency Operations On the third attempt, ROV activated autoshear function. (BSR thought to have closed.) Well continued to flow.IMT reports
25-Apr-20105-May-2010BOP Emergency Operations Seventeen further attempts by ROVs using subsea accumulators to close various BOP rams and annular preventers. Well continued to flow.IMT reports
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