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US Chemical Safety Board releases report into fatal 2019 hydrogen sulphide release

21 May 2021

On May 21, the US Chemical Safety Board (CSB) released its final report into the fatal October 2019 hydrogen sulphide release at the Aghorn Operating waterflood station in Odessa, Texas. The release fatally injured an Aghorn employee who was working at the facility that evening, as well as his spouse who attempted to locate him at the facility after he did not return home.

The CSB's final report can be found by clicking here.

The Aghorn Operating waterflood station is used as part of a process to extract oil from underground reservoirs in West Texas. During extraction, oil comes out of the ground with some water in it. The water is removed from the oil, but it can contain some residual oil and other contaminants such as hydrogen sulphide, a toxic gas. At the Aghorn waterflood station, pumps, in a building called the “pump house,” are used to pressurise and inject the water back into the oilfield. The injected water adds pressure to the reservoir allowing a larger quantity of oil to be extracted.

CSB Chairman Katherine Lemos said: “Waterflood stations are common throughout Texas. The CSB report determined that additional safeguards are needed to help ensure that a similar event is prevented.”

The CSB reports that on the night of the incident, the waterflood station’s control system activated an oil level alarm on a pump. An Aghorn pumper was notified, drove to the waterflood station, and attempted to isolate the pump from the process by closing two valves. The CSB found, however, that the pumper failed to isolate the pump from energy sources before performing the work. At some point while the pumper was in the vicinity of the pump, the pump automatically turned on, and water containing hydrogen sulphide escaped into the pump house. The pumper was overcome and fatally injured by the toxic gas.

After the incident, the CSB found that a plunger on the pump had shattered, which had allowed the release to occur. Due to the limitations of the available evidence, the CSB was unable to determine whether the pump failure and toxic release happened before the pumper arrived at the facility, or when the pump automatically turned on while the pumper was closing valves.

A couple of hours passed, and when the pumper did not return home, his spouse drove with their two children to the station to check on him. She located him on the floor of the pump house and was also overcome and fatally injured by the toxic hydrogen sulphide gas. The children remained in the car and were not injured.

The CSB’s report details the following safety issues found at Aghorn:

Nonuse of Personal Hydrogen Sulphide Detector: The pumper was not wearing his personal hydrogen sulphide detection device inside the pump house on the night of the incident, and there is no evidence that Aghorn management required the use of these devices.

Nonperformance of Lockout / Tagout: At the time of the incident, Aghorn did not have any written Lockout / Tagout policies or procedures. The pumper did not perform Lockout / Tagout to deenergize the pump before performing work on it.

Confinement of Hydrogen Sulphide Inside Pump House: The pump house could be ventilated by two bay doors, exhaust fans, and natural vents. Due to the limitations of the available evidence, the CSB was unable to confirm whether the exhaust fans were operational at the time of the incident. The two bay doors were approximately 60% open. The building was not adequately ventilated during the incident.  

Lack of Safety Management Program: The CSB found the formal company safety or operational policies and procedures used by Aghorn Operating were incomplete and inadequate.

Nonfunctioning Hydrogen Sulphide Detection and Alarm System: The waterflood station was equipped with a hydrogen sulphide detection and alarm system. However, the system’s control panel did not receive signals from the internal and external detection sensors on the night of the incident, and, therefore, did not trigger either of the two alarms.

Deficient Site Security: As per Aghorn’s informal policy, when an Aghorn employee is working at the facility, the access gates are normally left unlocked. The unlocked gates allowed the pumper’s spouse to drive directly to the waterflood station and enter the pump house, where she was also fatally injured.

As a result of its investigation, the CSB is making several recommendations to Aghorn Operating, Inc. for safety improvements at all waterflood stations where the potential exposure to dangerous levels of toxic hydrogen sulphide gas exists. These include:

- Mandate the use of personal hydrogen sulphide detection devices;

- Develop a site-specific, formalized and comprehensive Lockout / Tagout program for each facility;

- Commission an independent and comprehensive analysis of each facility to examine ventilation and mitigation systems;

- Develop and demonstrate the use of a safety management program that includes a focus on protecting workers and non-employees from hydrogen sulphide;

- Ensure that hydrogen sulphide detection and alarm systems are properly maintained and configured, and develop site-specific detection and alarm programs and associated procedures;

- Ensure that the hydrogen sulphide detection and alarm system designs employ multiple layers of alerts unique to hydrogen sulphide; 

- Develop and implement a formal, written, site-specific security program to prevent unknown and unplanned entrance of those not employed by Aghorn.

In addition to recommendations to the company, the CSB made a recommendation to OSHA to issue a safety information product that addresses the requirements for protecting workers from hazardous air contaminants and from hazardous energy, and a recommendation to the Railroad Commission of Texas to develop and send a Notice to Operators to all oil and gas operators that fall under its jurisdiction that describes the safety issues described in the CSB’s report.


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