April, 2010

This is a repeating event

201020AprAll DayDeepwater Horizon Blowout & Explosion 2010BP Macondo (US-GM) Origin: CSB Lessons:Asset integrity,Commitment & Culture,Compliance with Standards,Contractor Management,Incident Investigation,Management of Change,Operating Procedures,Operational IntegrityIndustry:OffshoreCountry:United StatesLanguage:ENLoC:Overpressure

Summary

On April 20, 2010, a multiple-fatality incident occurred at the Macondo oil well approximately 50 miles off the coast of Louisiana in the Gulf of Mexico during temporary well-abandonment activities on the Deepwater Horizon (DWH) drilling rig. Control of the well was lost, resulting in a blowout—the uncontrolled release of oil and gas (hydrocarbons) from the well. On the rig, the hydrocarbons found an ignition source and ignited. The resulting explosions and fire led to the deaths of 11 individuals, serious physical injuries to 17 others, the evacuation of 115 individuals from the rig, the sinking of the Deepwater Horizon, and massive marine and coastal damage from a reported 4 million barrels of released hydrocarbons.

BP was the main operator/lease holder responsible for the well design, and Transocean was the drilling contractor that owned and operated the DWH. On the day of the incident, the crew was completing temporary abandonment of the well so that it could be left in a safe condition until a production facility could return later to extract oil and gas from it.

Abandonment activities would essentially plug the well. Earlier, a critical cement barrier intended to keep the hydrocarbons below the seafloor had not been effectively installed at the bottom of the well. BP and Transocean personnel misinterpreted a test to assess cement barrier integrity, leading them to erroneously believe that the hydrocarbon bearing zone at the bottom of the well had been sealed. When the crew removed drilling mud from the well in preparation to install an additional cement barrier, the open blowout preventer (BOP) was the only physical barrier that could have potentially prevented hydrocarbons from reaching the rig and surrounding environment. The ability of the BOP to act as this barrier was contingent primarily upon human detection of the kick and timely activation and closure of the BOP.

Removing drilling mud after the test allowed hydrocarbons to flow past the failed cement barrier toward the DWH. The hydrocarbons continued to flow from the reservoir for almost an hour without human detection or the activation of the automated controls to close the BOP. Eventually, oil and gas passed above the BOP and forcefully released onto the rig. In response, the well operations crew manually closed the BOP. Oil and gas that had already flowed past the BOP continued to gush onto the rig, igniting and exploding. The explosion likely activated an automatic emergency response system designed to shear drillpipe passing through the BOP and seal the well, but it was unsuccessful.

KEY ISSUES:
• BOP TECHNICAL FAILURE ANALYSIS
• BARRIER MANAGEMENT AT MACONDO
• SAFETY CRITICAL ELEMENTS
• HUMAN FACTORS
• ORGANIZATIONAL LEARNING
• SAFETY PERFORMANCE INDICATORS
• RISK MANAGEMENT PRACTICES
• CORPORATE GOVERNANCE
• SAFETY CULTURE

ROOT CAUSES:
1. Technical Factors
2. Human and Organizational Factors
3. Regulatory Factors


Image Credit: CSB

Origin

CSBUS Chemical Safety Board

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