Overview
On June 12, 2019, the US Chemical Safety and Hazard Investigation Board (CSB) issued its first investigation report of an onshore drilling accident. The accident, which occurred on January 22, 2018, involved a blowout and rig fire at Pryor Trust 0718 gas well number 1H-9 near Quinton, Oklahoma. Five workers who were inside the driller's cabin on the rig floor died from thermal burn injuries and smoke and soot inhalation. The report is noteworthy because it was the CSB's first foray into onshore oil drilling and presented significant, widespread recommendations to other government agencies and the drilling industry. The CSB does not have any regulatory authority, and therefore must rely on other government agencies and the industry to voluntarily implement its recommendations.
The CSB found that the cause of the blowout and rig fire was the failure of both the primary barrier (hydrostatic pressure produced by drilling mud) and the secondary barrier (human detection of influx and activation of the blowout preventer), which were intended to prevent a blowout. Contributing factors included:
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Underbalanced drilling performed without proper planning, equipment, skills, or procedures
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Tripping performed out of the underbalanced well, allowing a large amount of gas to enter the well
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Lack of effective driller training on new electronic trip sheet, used to monitor for gas influx
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Abnormal equipment alignment during tripping operations, causing missed indications of gas influx
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Surface pressure was not identified two separate times before opening the Blowout Preventer
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A weighted pill intended to overbalance the well was miscalculated
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Both day and night drillers turned off alarm system due to excessive non-critical alarms
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Key flow checks were not performed before the incident
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The drilling contractor did not test its drillers' abilities in detecting indications of gas influx
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Operating company did not specify the barriers required during operations
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No drilling-specific regulatory standard governing onshore drilling safety
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Victims had no safe escape route from the driller’s cabin once the fire started
Based on the findings from this accident, the CSB issued recommendations to the Occupational Safety and Health Administration (OSHA); the American Petroleum Institute (API); Patterson-UTI Drilling Company, LLC; Red Mountain Operating, LLC; the International Association of Drilling Contractors (IADC); Pason Systems Inc.; National Oilwell Varco; and the State of Oklahoma. The recommendations included safety management changes, implementing an automatic safety instrumented system, alarm management, and establishing new state regulations on drilling operations.
The full report can be read here.