On April 20 2010 a blowout occurred on the semi-submersible Deepwater Horizon which had just completed a well for BP in the Gulf of Mexico. 11 of the personnel on board died in the subsequent explosion and the remaining crew members evacuated by lifeboat, liferaft and by jumping into the sea. After a couple of days the still burning rig sank in 5000 feet (1524 metres) of water with the riser still attached and the well continued to belch forth thousands of barrels of crude oil per day into the Gulf.

The time taken to control the well is measured in months, and during this time a number of investigations took place including one by BP, the operator, one by the US Coast Guard and one termed as “The President’s Investigation”. By enrolling with the Coast Guard as a journalist I was able to follow the progress of the event and the investigation, and as a result compiled a commentary on my old website and then a section of my book “A Catalogue of Disasters”. So for the interest of visitors to this website I have uploaded the resulting document, and for convenience divided it into sections.

Section 1. The Vessels Involved: The Preamble: the Sequence of Events.

Section 2. The Progress of the investigations: BP’s attempt to stem the flow of oil. Click Here

Section 3. The Content of the Investigations:  My Comments. Click Here 

Section 4. The Senior Toolpusher’s Testimony. Click Here




The Deepwater Horizon was a well found dynamically positioned (DP) semi-submersible built in 2001 in South Korea. It had originally been owned by Reading and Bates (R&B Falcon) and became part of the Transocean fleet when that company was taken over. It was classed with ABS and was registered in the Marshall Islands. It was 396 feet long (114 metres) and 136 feet (41.5 metres) wide with accommodation for 150 people and when at working draught it displaced about 50,000 tonnes. Its basic structure was of two pontoons on which were positioned four columns which were cranked inwards towards the Main Deck, one assumes to improve the rig’s ability to transition from drilling draught to transit draught and vice-versa. The upper hull contained two decks under the Main Deck with the six Main Generator Rooms aft with their related switchgear rooms and the Mud Pump Room and the Mud Pit Room directly forward of them. The Sack Store extended along the starboard side and forward was the accommodation, office spaces the Mess Room and the Galley. Extending from the upper of the two decks were the forward and aft evacuation stations each with a 72 person lifeboat on each side. On the port side of the forward evacuation station were three liferafts with an associated davit for launching them, and at the after edge of the aft evacuation station were a further three liferafts with their associated davit.

At the forward port corner at Main Deck level, directly beneath the helideck  was the Central Control Room. In order to achieve common nomenclature with the rest of this volume it will be known in this narrative as the Control Room/Pilot House. This space contained everything required to operate the unit, from the navigation systems and the DP computers, to engine and power management and readouts of the drilling systems. The space also contained the ballast control and the fire and gas alarm panels, a secondary BOP control panel and the internal and external communication systems including the GMDSS. Importantly it also contained the Emergency Shutdown (ESD) system and the Emergency Disconnect (EDS) button.


Centrally in the hull was the Moonpool above which at some elevation was the Drill Floor.  At the side of the Drill Floor with a view of the working area was the “Driller’s Workstation” known elsewhere in this document as the Driller’s Doghouse. The Doghouse, unusually, was a pressurised area which allowed non EX equipment to be installed there-in. 

The rig was capable of drilling in 9000 feet (2740 metres) of water to a depth of 35,000 feet (10670 metres), and had already done both. It was powered by six Wartsila engines developing a collective 58,650 bhp which supplied eight azimuthing thrusters as well as the drilling and domestic systems. In accordance with the regulatory requirements it had been possible to designate one of these engines as the emergency generator. In the event of one or all of the operating engines failing one of the standby engines would start up automatically. Also available was a “black start” generator which could be started up in order to initiate the power systems after a complete shutdown. This generator was also connected to emergency lighting and communication systems, but it was not connected to any fire pumps.

The rig was provided with extensive firefighting systems including fire stations with hydrants and hoses, deluges, including one in the Moonpool intended to protect the bulkhead abutting the accommodation, and CO2systems in a number of machinery and control spaces. The fire pumps were located in No 1 and No 6 engine rooms, and of course required one of the main engines to be functioning to operate them. Also it was necessary to have the main salt water supply system operating since this system supplied the hydrants on the lowest deck directly and the rest via the fire pumps. 


The  Damon B Bankston was a VS480 platform ship built in 2002 at the Quality Shipyard in Louisiana. It was owned and operated by Tidewater and at the time of the accident was chartered by BP. It is 79.5 metres (261 feet) long and its four engines provide 9790 bhp, which drove two azimuthing propellers for main propulsion and a couple of thrusters forward. Like almost all offshore supply vessels it had tankage for a variety of fluids used offshore. These had the capacity for 1300 cubic metres of fuel, 600 cubic metres of potable water and 1290 cubic metres of liquid mud. Importantly in relation to this accident it was provided with a small FRC on the port side which could be deployed by one of the ship’s cranes. 


The Discoverer Enterprise was a Transocean drill ship which was built in Ferrol, Spain in 1999. It could be said to have been the first of the modern fleet of drillships which now populate the seas, drilling in water which is generally deeper than can easily be managed by moored semi-submersibles. The design was based on a FPSO hull and as a result there was storage capability for hydrocarbons, or in fact any other liquid they might wish to hold. The vessel was capable of DP operations and was powered by six Wartsila engines giving it an available power of 53,000 bhp. It was designed to operate in 10,000 feet (3048 metres) of water, and could drill to a depth of 35,000 feet (10670 metres). It was 835 feet (254 metres) long and had accommodation for 200 people. 


The semisubmersible Q4000 was a DP “well intervention vessel” which means that its intended task is the maintenance of existing oil wells, rather than the construction of them. In aide of this task it had what is termed a “drilling tower” which takes up less space than a conventional derrick and also a 360 tonne capacity crane. It was built by Keppel AmFELS in Brownsville, Texas and entered service in 2002. It was 95 metres (311 feet) long and 62 metres (203 feet) wide, and had a transit speed of 12 knots.


Many other vessels and two semisubmersibles were involved at various times in this accident, particularly during the period after the Deepwater Horizon sank, while attempts to stem the flow from the well were taking place, but it is not really of benefit to this narrative to include any details about them.



The Macondo well was located in Mississippi Canyon Block 252, 48 miles from the nearest land and 114 miles from Port Fourchon. The well commenced with the Transocean Marianas in October 2009, but soon after the work had started the rig was damaged by hurricane Ida, and it was towed away to port for repair. Therefore in early 2010 the Deepwater Horizon was relocated to continue with the well. The BP report says that during the drilling there were a number of problems relating to the operation. There were losses to the formation which were apparently sorted out by ”Lost Circulation Materials” or as other reports say “a junk shot” and thereafter the drill string became stuck and could not be freed, and so the lower part of the wellbore had to be bypassed. Some redesign of the well was taking place due to the formation pressure. On April 4 2010 there were further losses of circulation which were apparently sorted out with further junk shots and a reduction in mud weight. The report goes on to say that full circulation was recovered on April 7. On April 9 the well reached a final depth of 18360 feet (5596 metres).

On April 16 the Minerals Management Service (MMS) approved the procedure for temporary abandonment of the well and the work to plug and abandon was initiated. By the time the well reached TD it was more than fifty million dollars over budget.

On April 20 2010 there were managers from both Transocean and BP on board the rig for the purpose of presenting a safety award to the unit. 

At the time of the accident the operation was technically under the control of the BP Macondo Well Team who were shore based and directly involved with the operation were the BP “Well Site Leaders” or as we have them the Senior Company Man and the Night Company Man. The Senior Company Man was temporarily assigned to the job since the usual incumbent of the position was on shore undertaking a well control course. The company who were contracted to do the cement job were Halliburton, and the mudloggers were Sperry Sun, and MI Swaco provided the mud engineers, whose task was to ensure that the drilling fluid was properly mixed for the job. This is a fairly typical distribution of services on board drilling units. 



April 16 2010. 

1248-1253. The decision is made not to run the same number of centralisers as required by the original plan, in the final casing run.

April 18 2010.

2058. Halliburton carry out some lab tests on the cement, reported as “partial results”.

April 19 2010.

1330. The final production casing run is completed to 18304 feet (5579 metres).

1620. After a number of attempts, circulation is established with 3142 psi.

1930.Pumping cement commences.

April 20 2010.

0040. Five barrels of fluid are bled off to reduce the pressure from 1150 psi to 0 psi.

0730. Discussion take place regarding the running of a cement bond log (CBL) and BP Macondo well team decide not to do this.

1200. A successful positive pressure test takes place (This from the BP report). Drill pipe is run into the hole to 8367 feet (2550 metres) in preparation for the mud displacement and a negative pressure test.

1231. The Damon B Bankston is in position alongside the Deepwater Horizon using its DP system.

1328. Mud offloading to the Damon B Bankston commences. During this operation the pit levels cannot be monitored. The BP report says “the mudlogger tells the Assistant Driller this”.

1430. The BP Vice-President of Drilling and Completion for GOM, the BP Drilling Operations Manager for Exploration and Appraisal for the GOM, the Transocean Operations Manager (Performance) and the Transocean Operations Manager (Assets) arrive on board to conduct what is termed as a “leadership team visit”. 

1504. Seawater is pumped to assist with mud displacement.

1600. The Transocean and BP managers begin a guided tour of the rig. Cleaning of the Trip Tank commences.

1700. The Senior Toolpusher remains on the Drill Floor as the rest of the tour move on, due to some emerging well control issues.

1717. The offloading of mud from the rig to the Damon B Bankston ceases, approximately 3100 barrels have been transferred. During this time there are observations of various pressures in the annulus and the drill pipe.

1745. The VIP tour of the rig is completed.

1750. Cleaning of the trip tank is completed. 

1955. After a slightly confusing set of statements about negative pressure tests it is concluded that the second test has been successful (according to the BP report). This is despite pressure in the drill pipe which is explained away as an anomaly. 

2000. Pumping of seawater down the drill pipe commences to displace the remaining mud from the riser.

2045. The VIPs arrive in the Control Room/Pilot House, resuming their tour, which is to review the DP operations and see the simulator in operation.

2052?The well becomes underbalanced and starts to flow.

2108.Drill pipe pressure increases. Pumps are shut down to enable a sheen test to be conducted. (A sheen test although it sounds quite technical involves someone looking at the liquid returning from the well to see if there is any oil in it).

2114.Sheen test is successful, indicating that fluids can be discharged overboard. With the pumps off, drill pipe pressure is seen to increase. The pumps are then restarted to discharge well fluids overboard.

2117. As No 2 pump is started a pressure of 6000 psi is seen, possibly indicating a shut valve.

2118. All pumps except No 1 are shut down.

2120. Discussion between Senior Toolpusher, now in his cabin, and the Night Pusher indicates that all is well.

2127. Some unexpected pressure increase are seen. Some pumps restarted. (The BP report is confusing, possibly intentionally).

2130. The Chief Mate of the Deepwater Horizon visits the Drill Floor and hears the Toolpusher and the Driller discussing “differential pressure”. 

2130. Drill pipe pressure decreases to 400 psi.

2134. Drill pipe pressure has increased to 1766 psi from 1210 psi.

2138. Hydrocarbons pass from the well into the riser.

2140. Mud is seen overflowing onto the Drill Floor.

2141. Mud is cascading up into the derrick under pressure. The diverter is apparently closed (This is its normal state) And the well flow is diverted to the mud gas separator (MGS). The lower annular preventer of the BOP is possibly closed.

2142. Drill pipe pressure is reduced from 1400 psi to 338 psi, and then increases to 1200 psi. The Damon B Bankston is advised by the Control Room/Pilot House to move away to the 500 metre boundary.

2144. Mud and water is expelled from the MGS vents at the top of the derrick and is raining down on the rig and the ship, which is probably still making its way to the 500 metre boundary.

2145 approx. The Chief Electrician locks out the electricity to No 2 mud pump, so that four drilling personnel can replace a pressure relief valve (This from the BP report but almost impossible to believe). The Chief Mate of the Damon B Bankston sees the fluid release from the well. 

2146. Noise of gas release probably from the MGS vents is heard.

2147. Drill pipe pressure increases from 1200 psi to 5730 psi (possibly due to the effective sealing of some of the BOP functions).  

2148. Four people are still repairing the pressure relief valve on No 2 mud pump. The main engines start to overspeed.

2150. The Assistant Driller calls the Senior Toolpusher and tells him “the well is blown out” and says that the well is being shut in. The Night Pusher calls the Company man to inform him of the situation. The on-watch DP Operator receives a call from the Drill Floor to tell her that there is a “well control situation”.

There is an explosion followed by gas alarms, and then a further explosion. The second explosion probably occurs in Engine Room No 3, or the associated electrical spaces.

The Chief Mate arrives in the Control Room/Pilot House, and tells the Captain that the fire is not controllable and that the unit should be abandoned.

2152-56. There are a number of exchanges in the Control Room/Pilot House which result in the Subsea Supervisor pressing the button to initiate the Emergency Disconnect System (EDS) but he observes that the gallon count shows “no flow” indicating that the required operation has not taken place. During this time there is much discussion in the Control Room/Pilot House as to who has the authority to press the EDS button, and someone has indicated that only the OIM can give permission. During this time the OIM arrives and gives the permission, but of course the action has already been taken, and has been unsuccessful. 

2156Deepwater Horizon broadcasts a Mayday message by activating the GMDSS distress system. The Damon B Bankston is instructed to move away to the 500 metre boundary (This from the USCG report). They release the mud hose manually and move off.

The Captain of the rig announces activation of the Emergency Disconnect System (EDS).

The OIM goes to the forward lifeboat station to ensure that the lifeboats are undamaged.

After determining that the command of the unit has changed from the OIM to the Captain, the Chief Engineer asks the latter if he can take a team to try to start the standby generator. Permission is given and he and the Chief Electronics Technician and a Motorman depart to attempt this.

2200. The on-watch DP Operator activates the general alarm and the Senior DP Operator makes an emergency announcement using the PA, telling people to go to their secondary emergency stations.

A Mud Engineer goes to his secondary emergency station which is the Galley, to find it completely collapsed and then goes out with others to the forward evacuation station where an Assistant Driller is attempting to take a muster.

There is chaos at the evacuation station and in the lifeboats, and no muster or proper control is possible. The Transocean Operations Manager (Performance) arrives and sees that both boats are still in the falls. He sees things falling out of the derrick, and tells the Coxswain of lifeboat No 2 “to go”.

Lifeboat No 1 contains some injured personnel making the remaining space very cramped for the uninjured. One is the BP VP for Drilling and Completions who actually should have been in lifeboat No 2. He said that there was pandemonium in the boat. 

2205.The US Coast Guard D8 Command Centre issue an “Urgent Marine Information Broadcast” about the Deepwater Horizon situation. 

2206. The BP “Performance Coordinator” calls the BP Texas shore base by Satellite phone and advises them of the situation. They in turn call US Coast Guard.

2210. Coast Guard Air Station New Orleans launches helicopter CG-6605.

2212. The Damon B Bankston launch their FRC manned by the Chief Engineer and an AB.  They see people from the rig jumping into the sea.

2230. Helicopter CG-6605 arrives on the location and assumes the role of On Scene Commander.

2230 approx. Lifeboat No 1 is launched under the informal command of the Transocean Operations Manager (Performance), with the off-watch DP Operator as Coxswain. The launch is delayed because they have waited for the Captain, but he has said that he and others still on the rig will go to the liferafts.

2245 approx(my time). The Captain and the group who have been unsuccessful in their attempts to start the standby generator make their way to the liferaft station and prepare to launch. In the increasing heat and smoke the raft is deployed overside on its davit and launch takes place, leaving the Captain, the on-watch Senior DP Operator, the Chief Electronics Technician and a Motorman on the rig. They subsequently jump into the sea. (There is a narrative included in this section telling us what happened afterwards in the liferaft).

2314. The off-watch DP Operator is the last person to transfer from Lifeboat No 1 to the Damon B Bankston.

2330. Headcount taken by the Damon B Bankston and the total is 111. The ship advises those carrying out SAR that there are 15 people missing.

2335. A Transocean manager, now on the Damon B Bankston reports to the Coast Guard D8 Command Centre that 115 of the 126 people on board have made it to the ship. (In the Coast Guard report this is timed at 2235, but it is almost certainly a misprint)

2353. A Coast Guard rescue swimmer boards the Damon B Bankstonfrom a helicopter to carry out triage and take control of “medical evacuation”.

2400. A number of vessels the SeacorLee,the Alice G McCall, C-Enforcer, the Gloria B Callais, the Norbert Bouzigard  and the Monica Ann commence firefighting at the rig using their monitors.

April 21 2010.

0055. The Damon B Bankston log states that there are four vessels engaged in firefighting operations.

0115. The following vessels now carrying out firefighting and SAR activities, all under the informal control of the Damon B Bankston: Alice G McCall, Kobe Chouest, Ocean Intervention III, Reliance, Max Chouest, Pat Tillman, C-Pacer, MSC Familia, Gloria B Callais, Laney Chouest, C-Express.

0130. The Deepwater Horizon begins to list to starboard and to take on a stern trim.

0210. The Coast Guard vessel CGC Pompano arrives and assumes the role of on scene commander for surface vessels.

0318.The rig is listing more heavily.

0500. It seems that there are now 11 vessels engaged in firefighting. The Damon B Bankston log says “too many to list”.

0730. The CGC Zephyr assumes the role of OSC, and thereafter further Coast Guard vessels arrive.

0800 or so. The Transocean Operations Manager (Performance) the one person from the rig who has remained on the scene, and may now be on the Max Chouest, realises that stability might be of some concern. There are instructions from the Transocean Command Centre that firefighting should be directed to the underside of the rig.

1800. BP initiates ROV operations to attempt to hot stab the BOP (No ship identified in the BP report, however the Coast Guard report indicates it is the Max Chouest). 

2140. The Max ChouestROV continues efforts to operate the Deepwater Horizon BOP.

2345.The Smit Salvage America chartered vessel the Seacor Vanguard arrives on scene and takes control of the firefighting operations.

April 22 2010.

0130. The survivors from the rig are delivered to the shore from the Damon B Bankston.

0645. The Max Chouest ROV reported to be back on deck, and it seems that ROV operations continue using other vessels.

0740. An ROV is thought to have activated the Blind Shear Rams on the BOP, but no change in well flow. Thereafter over a number of days ROV interventions continues but there is no change to the well flow.

1026.The rig sinks.

 From this point there are occasional reports of what has been happening as attempts are made to stem the flow of oil. They are summaries of what might be called “diary entries” originally published on the author’s website as events unfolded. To continue Click Here

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