Event sequence 20/04/2010 (CNN, 2010)
System parts
12:35am - Cement contractor, Halliburton, completes cementing in well
11:00am - Meeting between BP and Transocean executive management regarding changes in drill plan
5:05pm - Unexpected loss of fluid in riser pipe, suggestive of leaks in blowout preventer
5:00-7:00pm - Negative pressure tests run. Results are indicative of leaking and a build up a natural gas.
8:00pm - Testing ends and remaining drill fluids replaced with seawater
9:00pm - Reports indicate more fluid is flowing out of well, then being pumped in
9:10pm - Well pipe shutdown, well continues to flow and drill pipe pressure increases
9:30pm - Increased fluid and abnormal pressure observew. Well pip abruptly shudown
9:50pm - Gas surge and drilling fluid observed to be onto deck. First explosion occurs.
9:52pm - Distress call issued and order given to abandon rig.
People
Workplaces
Management
Workplace factors
Site design
Fixed plant
Geotech design
Access
Equipment design
Work environment
126 people on the rig at the time of the accident, 11 killed (CNN, 2010)
The rig had six large diesel generators powered by onboard electric plant, and a smaller back up diesel generator (National Academies Press, 2012)
Maconda well had a total depth of 18,300ft below sea level and in more than 5,000 ft of seawater (National Academies Press, 2012)
The rig was a self-propelled vessel and stable floating base used for drilling and construction of an undersea well (National Academies Press, 2012).
The rig's design accommodates propulsion power to ensure the stability of the site against wind and ocean currents (National Academies Press, 2012)
Protective electrical and mechanical devices were installed to detect combustible gas and prevent ignition, in areas where explosive mixtures of hydrocarbons and air may accumulate if released (National Academies Press, 2012)
Three overspeed shutdown devices were fitted, however none were designed to shutdown air intake to engines directly (National Academies Press, 2012)
System did not determine that the diesel engine was 13% above rated speed (National Academies Press, 2012)
Warning systems
Integrated Alarm and Control System (IACS) controlled and monitored the rig alarm system (National Academies Press, 2012)
27 Combustible Gas Detectors (CGDs) on the rig. 13 of which were able to secure ventiliation fans and electrical power to an affected area. 14 had just an audible and visual display (National Academies Press, 2012)
The CGD in the engine rom did not have an automated response and required a crew member to validate the alarm and then take manual actions (National Academies Press, 2012)
Accident occurred at night - darkness, no power (CNN, 2010)
Fumes and risk of inhalation of oil and gas after surge and spill onto rig deck (CNN, 2010)
Blowout Preventor (BOP) installed as a means of well control to seal an open well bore, close the annular portion of the well, or cut through the pipe and then seal the well (National Academies Press, 2012)
BP deferred maintenance of the upper and lower annular of the BOP less than a week before the accident (National Academies Press, 2012)
Significant fire on the rig (National Academies Press, 2012)
BOP not designed for dynamic conditions in existence at the time and determined not to be a high-reliability, fail-safe device based on design, test, operation and maintenance (National Academies Press, 2012)
The rig is located 114 miles from Port Fourchon, Louisiana, and 154 iles from the Houma, Louisiana, helicopter base (BP, 2010)
Access via helicopter/boat
Staff were employed by BP, Halliburton, and Transocean (BP, 2010)
Organisational/system factors
Drilling team mistakenly determined the cementing operation had been completed successfully, and conducted a negative pressure test (National Academies Press, 2012)
Drilling team mistakenly determined the negative pressure test had been conducted successfully, and subsequently abandoned the well (National Academies Press, 2012)
Decision made to displace the drilling mud with seawater despite failing to demonstrate integrity of the cement and negative pressure tests (National Academies Press, 2012)
Emergency Disconnect System (EDS) failed to operate as it required manual activation - impacted due to fire on rig floor (National Academies Press, 2012)
Blowout of Macondo well (National Academies Press, 2012)
Gas hydrocarbons released, in conjunction with low wind velocity made ignition inevitable
Lack of strong safety culture (National Academies Press, 2012)
Lack of appropriate policies and procedures that provided an effective system safety approach applicable to the Macondo well (National Academies Press, 2012)
Geologic conditions posed challenges to the drilling team
The training of management and decision makers both in industry and the regulator was inconsistent with the level of complexity and risks associated with deepwater drilling (National Academies Press, 2012)
Schlumberger team responsible for performing full analysis of geological safety of the well was denied ability to perform Cement Bond Log (CBL), and to have kill fluid dumped down well (EDM Digest, 2017)
Transocean and BP staff misinterpreted results of negative pressure tests (EDM Digest, 2017)
No fixed fire-extinguishing system installed on Drill Floor and adjacent areas (EDM Digest, 2017)
Drilling crew failed to use the diverter line for well flow, instead of the MGS - this caused gas to discharge on the main deck (US Coastguard, 2011)
Lack of systems to track hazardous electrical equipment - some on board were in bad condition and corroded, and left in hazardous areas. This created a potential cause of the explosions (US Coastguard, 2011)
Bridge crew was not provided training on activation of the Emergency Shutdown (ESD) system (US Coastguard, 2011)
Procedures on emergency shutdown system not provided to responsible staff - this could have prevented or delayed explosions (US Coastguard, 2011)
Some gas detectors were bypassed or inoperable at the time of the explosions (US Coastguard, 2011)
The rig lacked appropriate crew blast protection against explosion (US Coastguard, 2011)
Information Transfer
No transfer of authority occurred after explosions causing confusion at a critical point of the emergency and possibly impacted the activation of the emergency shutdown system (US Coastguard, 2011)
External factors
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Software
Humans
Halliburton
BP
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Transocean staff had not had sufficient training to take full responsibility for the safety of the vessel (US Coastguard, 2011)
Transocean
Crane Operators
Assistant Drillers
Floorhands
Derrick Hands
Chief Mechanic
Roustabouts
Assistant Engineers
Motor Operators
Division Manager
Chief Electronics Technician
Staff responsible for cementing the well
Executives
Mechanics
Ocean currents
Water pressure
Weather
Gas detectors
Fire detection and protection systems
Diesel generators
Drill pump
Emergency shutdown system
Fire main system
Toolpushers
Cranes
Propulsion thrusters
Drilling Team
Executive Management
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Human/machine interface
Emergency shutdown system
Dynamic Postioning console
Navigation System
Power and vessel management system panel
Load and stability computer system
Drilling deck console
Driller's intercom
Blowout preventer control panel
Drilling equipment control system
Uninterruptible power supple and charger/battery system
Drilling drive power systems
Electric power plant
Blowout Preventor
Thruster drive power systems
Visual and audio alarms
Water and weather tight doors
Lifesaving appliances
System Lifecycle
Concept
Construction
Commissioning
Operating
Maintenance
Decommissioning
Drilling deep sea to extract oil for petroleum from beneath the seabed
Risks to human life from drilling proess
Risks to ecological life due to oil and gas related factors
Built by Hyundai Heavy Industries - commenced construction 1998, completed in 1991 (US Coastguard, 2011)
Commissioned by R&B Falcon, which became part of Transocean (US Coastguard, 2011)
Electrical equipment installed may not have been capable of preventing ignition of flammable gas (US Coastguard, 2011)
Fire and gas detection systems installed did not automatically activate emergency shutdown system (US Coastguard, 2011)
Regulatory factors were considered to be insufficient as they did not cover several specific aspects that may have changed the course of the outcome - International Maritime Organisation (IMO) Mobile Offshore Drilling Unit (MODU) Code
Appropriate blast protection not installed (US Coastguard, 2011)
Arrangement of air inlets was not taken into adequate account - flammable gas may have affected all engine rooms due to this (US Coastguard, 2011)
Incorrect labelling of type of vessel determined implementation of type of management structure causing on who is responsible for emergency shut down
Appropriate training and trained crew required for operation of rig (US Coastguard, 2011)
Appropriate organisational structure required (US Coastguard, 2011)
Rig was incorrected listed as a self-propelled MODU which caused incorrect organisational structure to be implemented, resulting in possible lack of appropriate training being provided for emergency shut down (US Coastguard, 2011)
A-class fire barriers installed were not effective in preventing spread of fire (US Coastguard, 2011)
No consideration given to attempting to account for condition and location of crew members prior to abandonment of ship (US Coastguard, 2011)
Schedule maintenance required by appropriately trained mechanical staff
Adhoc related maintenance required as a result of audit findings by appropriately trained staff
Project Management (Rigzone, 2019)
Significant cost - on average $4-10 million (Rigzone, 2019)
Permitting and Regulatory Compliance (Rigzone, 2019)
Review contractual obligations
Engineering analysis
Operational planning
Contracting, often times 2 years in advance
Obtain permit to decommission - can take up to 3 years
Execution plan required for schedule of decommissioning activities
Permits required from Federal, State and local regulatory authorities
Platform preparation (Rigzone, 2019)
Tanks, processing equipment and piping to be flushed
Residual hydrocarbons disposed of
Platform equipment to be removed
Divers to prepare underwater removal
Well plugging and abandonment (Rigzone, 2019)
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Well abandonment
Planning
Preliminary inspections
Determine abandonment method
Submit application for Bureau of Ocean Energy Management, Regulation and Enforcement (BOEMRE) approval
Data collection
Well entry preparations
Slick line unit use
Filling well with fluid
Removal of downhole equipment
Plugging bottom of well, casing stubs, annular space
cleaning out wellbore
Placement of surface plug and fluid between plugs
Conductor removal (Rigzone, 2019)
Mobilisation/demobilisation and platform removal (Rigzone, 2019)
Pipeline and power cable decommissioning (Rigzone, 2019)
Material disposal and site clearance (Rigzone, 2019)