A failure of two preventive barriers in place to stop a blowout were the main causes of a blowout and rig fire that killed five workers at the Pryor Trust gas well in Pittsburg County, OK, in January 2018, a new report found.
On January 22, 2018, a blowout and rig fire occurred at Pryor Trust 0718 gas well number 1H-9, located in Pittsburg County, Oklahoma. The fire killed five workers, who were inside the driller’s cabin on the rig floor, according to the report from the Chemical Safety Board (CSB). They died from thermal burn injuries and smoke and soot inhalation. The blowout occurred about three-and-a-half hours after removing drill pipe (“tripping”) out of the well.
Red Mountain Energy, LLC was the lease holder, Red Mountain Operating, LLC (RMO) was the operator of the well, and Patterson-UTI Drilling Company, LLC (Patterson) was the drilling contractor hired by RMO.
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 be in place to prevent a blowout.
Contributing to the loss of barriers were other factors including:
• Underbalanced drilling was performed without needed planning, equipment, skills, or procedures, thus nullifying the planned primary barrier to prevent gas influx.
• Tripping was performed out of the underbalanced well, which allowed a large amount of gas to enter the well.
• The driller was not effectively trained in using a new electronic trip sheet, which is used to help monitor for gas influx.
• Equipment was aligned differently than normal during the tripping operation, leading to confusion in interpreting the well data which caused rig workers to miss indications of the gas influx.
• Surface pressure was not identified two separate times before opening the BOP during operations before the blowout, when there was evidently pressure at the surface of the well. This non-identification of surface pressure contributed to the gas influx not being identified.
• A weighted pill intended to overbalance the well was apparently miscalculated. After pill placement, the well was still underbalanced.
• Both the day and night driller chose to turn off the entire alarm system, contributing to both drillers missing critical indications of the gas influx and imminent blowout. The alarm system also was not effectively designed to alert personnel to hazardous conditions during different operating states (e.g., drilling, tripping, circulating, and surface operations) and would have sounded excessive non-critical alarms during the 14 hours leading to the blowout, which likely led to the drillers choosing to turn off the alarm system.
• Key flow checks to determine if the well was flowing were not performed before the incident. Drilling rig workers performed very few of the company-required flow checks during the drilling of well 1H-9 and the previous well. The drilling contractor did not effectively monitor the implementation rate of its flow check policy.
• The drilling contractor did not test its drillers’ abilities in detecting indications of gas influx through, for example, simulated pit gains. The absence of testing drillers’ influx detection skills — a safety-critical aspect of well control — might have contributed to both drillers not detecting the significant gas influx leading to the blowout.
• The operating company did not specify the barriers required during operations, or how to respond if a barrier was lost. This contributed to the performance of underbalanced operations the drilling rig and its crew were not equipped or trained to perform.
• The safety management system in place was not effective for managing safe rig operations. There is also no drilling-specific regulatory standard governing onshore drilling safety.
The report found 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.
Lack of Safety Practices
“Our investigation found significant lapses in good safety practices at this site,” said CSB Interim Executive Kristen Kulinowski. “For over 14 hours, there was a dangerous condition building at this well. The lack of effective safety management at this well resulted in a needless catastrophe.”
Industry best practices recommend always having two protective barriers in place during drilling operations. CSB investigators found those barriers failed.
The investigation found there are no regulations specifically developed for onshore oil and gas well drilling. Because oil and gas well drilling is exempt from the Occupational Safety and Health Administration’s (OSHA’s) Process Safety Management standard which governs safety for chemical processing facilities, OSHA has been utilizing the general duty clause – which “protects workers from serious and recognized workplace hazards” – but fails to address the unique safety hazards associated with drilling for oil and gas. The CSB urged OSHA to develop effective oversight that addresses the hazards unique to the onshore drilling industry.
As mentioned, the CSB found 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, the CSB said. Ultimately, the lack of critical alarms contributed to workers being unaware that flammable gas was entering the well during operations before the incident.
Alarm System Shut Off
“An effective alarm system is a method to help workers become aware of hazardous conditions, like gas entering the well,” said Investigator Lauren Grim. “With the alarm system off, the safety of the operation solely relied on workers to either visually identify signs of the gas influx or calculate volume differences that could indicate gas influx — and in this case, neither method was effective, and workers were unaware of the very large gas influx into the well before the incident. As a result, the workers had little knowledge of the impending disaster.”
At the time of the blowout, three workers were in the driller’s cabin. Two other workers who were on the rig floor ran into the driller’s cabin during the blowout and fire. All five of these workers died in the incident.
“When the blowout mud and gas ignited, it created a massive fire on the rig floor,” Grim said. “All five of the workers inside the driller’s cabin were effectively trapped because fire blocked the driller’s cabin’s two exit doors. Our investigation found that there is no guidance to ensure that an emergency evacuation option is present onboard these rigs or can protect workers in the driller’s cabin from fire hazards.”
As a result, 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.
“As onshore oil and gas extraction grows, it is imperative that the industry is using proven and reliable safety standards and practices,” Kulinowski said. “If some of these safety practices had been in place, this tragedy could have been averted. Our report lays out a strong case for recognizing the hazards in this industry and ensuring the safety of its workers.”