Oklahoma City, OK – The US Chemical Safety Board (CSB) has released its final investigation report into the blowout that fatally injured five workers at the Pryor Trust gas well located in Pittsburgh County, OK.
The CSB’s final report identifies a lack of regulations governing onshore drilling safety as well as shortcomings in safety management systems and industry standards utilized by the industry.
The report calls on regulators, industry groups, the state of Oklahoma and companies to address such gaps.
The CSB’s report determined that the cause of the blowout and rig fire was the failure of two preventive barriers that were intended to be in place to stop a blowout. Those were the primary barrier—hydrostatic pressure in the well, produced by drilling mud—and the secondary barrier—human detection of gas flowing into or expanding in the well and activation of the rig’s blowout preventer.
The report explains that unplanned underbalanced drilling and tripping operations allowed a large quantity of gas to enter the well, and safety-critical operations called “flow checks,” used to determine if gas is in the well, were not performed.
Furthermore, the CSB found that the drilling contractor failed to maintain an effective alarm system. Likely due to excessive “nuisance” or unnecessary alarms, the entire alarm system was disabled by rig personnel.
Ultimately, the lack of critical alarms contributed to workers being unaware that flammable gas was entering the well during operations before the incident.
The CSB is calling on the American Petroleum Institute (API) to address design improvements needed to protect driller’s cabin occupants from blowout and fire hazards.
The report also recommends to API to create guidance on Alarm Management for the drilling industry, to help ensure alarm systems are effective in alerting drilling crews to unsafe conditions.