GAS WELL BLOWOUT AND FIRE — ONSHORE DRILLING OPERATIONS
Pryor Trust Fatal Gas Well Blowout and Fire
Red Mountain Operating / Patterson-UTI Drilling
📍 Pittsburg County, OK
Incident: January 22, 2018  •  CSB Report: June 12, 2019
5
Fatalities
Natural Gas (High-Pressure Well Blowout)
Chemical Involved
19
CSB Recommendations
📋 Incident Summary

On January 22, 2018, a gas well blowout and fire at a drilling site in Pittsburg County, Oklahoma, fatally injured five workers. The explosion occurred during tripping operations -- pulling drill pipe from the well -- when a high-pressure gas kick was not detected and controlled in time to prevent a blowout.

The CSB found multiple failures: the drilling rig alarm horn had been disabled, no written tripping procedures specified required equipment configuration or well monitoring requirements, formal flow checks to detect gas influx were not performed, and no Well Construction Interface Document existed between operator Red Mountain Operating and drilling contractor Patterson-UTI. The driller's cabin offered no protection from fire or explosion.

The CSB's June 2019 report issued 19 recommendations -- the most ever for a single drilling-sector incident -- to OSHA, API, Patterson-UTI, Red Mountain Operating, National Oilwell Varco, Pason Systems, the IADC, and the State of Oklahoma. A central recommendation called on OSHA to apply or develop a safety management system standard for onshore oil and gas drilling.

🔎 Key Findings
Finding 01
Well Blew Out During Drill Pipe Tripping
A gas kick (formation fluid influx) went undetected during tripping operations, escalated to a blowout, and ignited -- fatally injuring five workers in the resulting fire and explosion.
Finding 02
Rig Alarm System Was Disabled
The drilling rig alarm horn and critical sensors had been turned off during tripping -- removing the primary warning system that could have alerted workers to gas influx before the blowout.
Finding 03
No Written Tripping Procedures or Flow Check Policy
Patterson-UTI had no written procedures specifying equipment lineup required for tripping operations and no policy requiring documentation of flow checks to verify the well was not taking gas influx.
Finding 04
No Well Construction Interface Document
No formal Well Construction Interface Document existed between operator Red Mountain Operating and drilling contractor Patterson-UTI -- safety responsibilities, barrier requirements, and monitoring expectations were undefined.
Finding 05
Driller's Cabin Offered No Fire Protection
The driller's cabin provided no fire rating, no safe evacuation routes from the rig floor during a blowout, and no means to rapidly activate blowout preventer controls from a protected location.
🔍 Root Causes
1
Absence of Safety Management System for Onshore Drilling
Unlike offshore operations, onshore oil and gas drilling is not subject to OSHA PSM or any equivalent safety management system requirement -- leaving well control entirely to voluntary industry practices with no mandatory written procedures, MOC, or hazard analysis requirements.
2
Drilling Contractor Lacked Written Procedures and Alarm Management
Patterson-UTI operated without written tripping procedures, alarm philosophy, or formal flow check documentation -- fundamental safety management elements absent from their onshore drilling operations.
3
No Formal Interface Document for Safety Barriers
Red Mountain Operating and Patterson-UTI had no Well Construction Interface Document defining safety barriers, monitoring requirements, and response obligations -- preventing coordinated well control.
☑ CSB Recommendations
→ OSHA
Apply the PSM standard (29 CFR 1910.119) to drilling of oil and gas wells, or develop a new standard with equivalent safety management system requirements specific to onshore well drilling.
→ API
Establish expert group to develop guidance on automated safety instrumented systems for BOP activation; publish technical bulletin on BOP safety instrumented system implementation strategies.
→ API
Develop recommended practice for safely tripping drill pipe in overbalanced, managed pressure, and underbalanced drilling -- including required equipment, influx control procedures, and monitoring requirements.
→ API
Develop recommended practice on alarm management for the drilling industry based on ANSI/ISA 18.2, addressing state-based alarm systems for different drilling operating modes.
→ API
Develop recommended practice addressing protection of rig workers from blowout fire and explosion hazards, including driller's cabin fire ratings, evacuation routes, and proximity of BOP activation controls.
→ Patterson-UTI
Develop written tripping procedures specifying required equipment configuration; implement formal flow check documentation policy and driller influx detection drill program with monitored response times.
→ Patterson-UTI
Develop alarm philosophy and alarm rationalization for all rig operations; establish alarm set points for drilling, tripping, circulating, and surface activities; prohibit disabling alarm systems.
→ Patterson-UTI
Update performance metrics to track leading and lagging indicators measuring effectiveness of flow check policy, alarm management, MOC program, and trip sheet completion.
→ Red Mountain Operating
Develop policy requiring a well-specific Well Construction Interface Document before drilling begins, specifying barriers, monitoring requirements, personnel qualifications, and MOC for real-time plan changes.
→ State of Oklahoma / OCC
Establish safety regulations requiring operators and drilling contractors to implement safety management system elements including written procedures, MOC, risk assessment, WCCID, and employee participation before drilling.
💡 Lessons Learned
Onshore oil and gas well drilling is among the most hazardous industrial operations in the United States -- yet it is not subject to OSHA PSM or any equivalent safety management system requirement. The absence of mandatory written procedures, alarm management, and MOC creates the conditions for fatal blowouts.
Alarm systems are only effective when they are on. Disabling the rig alarm horn during tripping operations removes the primary safeguard for early detection of a gas kick -- when the alarm is off, there may be no warning before a blowout.
A Well Construction Interface Document is not bureaucratic paperwork -- it is the safety contract between the operator and the drilling contractor. Without it, responsibilities for safety barriers, monitoring, and emergency response are undefined.
Flow checks are the most basic well control verification tool. Failing to perform and document flow checks during tripping means the crew has no formal method to confirm the well is not taking gas influx before proceeding.
The driller's cabin on a drilling rig must provide meaningful protection from fire and explosion during a blowout. A cabin adjacent to the rig floor with no fire rating and no safe evacuation route provides no protection when it is needed most.
SOP: Operating ProceduresMOC: Management of ChangePHA: Process Hazard AnalysisEP: Employee Participation
🔨 Safety Meeting Toolbox Talk
►At your facility, are there alarms or monitoring systems routinely disabled during certain operations? What would happen if a hazardous condition developed while those safeguards were off?
►Do you have written procedures for every critical operating mode -- including non-routine activities like startup, shutdown, maintenance, and equipment isolation?
►If you are working alongside a contractor, who is responsible for which safety barriers? Is that documented in writing before the job begins?
►What early warning indicators does your operation rely on to detect a developing hazard? Are workers trained on recognizing and responding to those signals?
►When someone makes a real-time change to the plan during operations, is there a formal review to evaluate the safety implications of that change before proceeding?
Immediate Action Items
✓Audit your facility's alarm management practices: identify any alarms routinely bypassed or disabled during normal operations and formally assess the risk of doing so.
✓Review written procedures for any critical non-routine operations and verify they specify required equipment configurations, monitoring requirements, and safety hold points.
✓For any operation involving a contractor in your process area, verify a written interface document exists defining safety responsibilities, required barriers, and emergency response roles.
✓Review your MOC program to confirm it captures real-time changes to operating procedures or the work plan, not only pre-planned modifications.
✓Train your team on the Pryor Trust blowout scenario and identify analogous situations at your facility where a critical safeguard could be disabled without formal review.
🔗 PSM Failures Behind This Incident

This incident traced to breakdowns across 4 PSM elements (SOP · MOC · PHA · EP). Each represents a documented gap that process safety documentation and consulting can close before a similar event occurs at your facility.

Operating Procedures (SOPs)
Operators cannot reliably hold safe operating limits without clear, current, enforced procedures. Deviation from acceptable operating conditions — a root cause here — is a direct consequence of SOP failure.
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Management of Change (MOC)
Changes to equipment, chemistry, operating limits, or procedures that bypass formal review create new hazard pathways your PHA never evaluated. MOC failures open the door to incidents like this one.
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Process Hazard Analysis (PHA)
A structured PHA or HAZOP study exists to identify exactly these scenarios before they occur. When PHA is absent, superficial, or overdue for revalidation, hazards operate unseen until they kill someone.
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Employee Participation
OSHA PSM requires workers to be meaningfully involved in hazard analyses and procedure development — not just trained on the finished product. Active participation catches gaps that management alone misses.
Supporting documents in our library →
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