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deepwater-horizon-1280x640 (Event sequence 20/04/2010 (CNN, 2010) (12…
Event sequence 20/04/2010 (CNN, 2010)
12:35am - Cement contractor, Halliburton, completes cementing in well
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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.
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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
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People
126 people on the rig at the time of the accident, 11 killed (CNN, 2010)
Staff were employed by BP, Halliburton, and Transocean (BP, 2010)
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)
Bridge crew was not provided training on activation of the Emergency Shutdown (ESD) system (US Coastguard, 2011)
Transocean staff had not had sufficient training to take full responsibility for the safety of the vessel (US Coastguard, 2011)
Workplaces
Workplace factors
Site design
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)
The rig lacked appropriate crew blast protection against explosion (US Coastguard, 2011)
Fixed plant
The rig had six large diesel generators powered by onboard electric plant, and a smaller back up diesel generator (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)
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)
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)
Geotech design
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)
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Access
The rig is located 114 miles from Port Fourchon, Louisiana, and 154 iles from the Houma, Louisiana, helicopter base (BP, 2010)
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Equipment design
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)
Some gas detectors were bypassed or inoperable at the time of the explosions (US Coastguard, 2011)
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)
Emergency Disconnect System (EDS) failed to operate as it required manual activation - impacted due to fire on rig floor (National Academies Press, 2012)
No fixed fire-extinguishing system installed on Drill Floor and adjacent areas (EDM Digest, 2017)
Work environment
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)
Significant fire on the rig (National Academies Press, 2012)
Management
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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)
System Lifecycle
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Construction
Built by Hyundai Heavy Industries - commenced construction 1998, completed in 1991 (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)
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)
A-class fire barriers installed were not effective in preventing spread of fire (US Coastguard, 2011)
Commissioning
Commissioned by R&B Falcon, which became part of Transocean (US Coastguard, 2011)
Operating
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)
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Decommissioning
Project Management (Rigzone, 2019)
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Contracting, often times 2 years in advance
Significant cost - on average $4-10 million (Rigzone, 2019)
Permitting and Regulatory Compliance (Rigzone, 2019)
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Platform preparation (Rigzone, 2019)
Tanks, processing equipment and piping to be flushed
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Well plugging and abandonment (Rigzone, 2019)
Planning
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Submit application for Bureau of Ocean Energy Management, Regulation and Enforcement (BOEMRE) approval
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Well abandonment
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Plugging bottom of well, casing stubs, annular space
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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)
