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Oklahoma Blowout Investigation

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. The blowout occurred about three-and-a-half hours after removing drill pipe out of the well. 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.1U.S. Chemical Safety and Hazard Investigation Board. (2019, June 12). Gas well blowout and fire at Pryor Trust Well 1H-9.

The U.S. Chemical Safety and Hazard Investigation Board (CSB) investigated the incident and found that underbalanced drilling was performed without needed planning, equipment, skills, or procedures, thus nullifying the planned primary barrier to prevent gas influx.2U.S. Chemical Safety and Hazard Investigation Board. (2019, June 12). Gas well blowout and fire at Pryor Trust Well 1H-9. As you watch the incident video below, you will see the importance of many of the concepts, equipment, and decision points discussed in previous lessons to this point. In the second half of the video, you will hear about recommendations made by the CSB to help prevent incidents like this one and similar loss of life on rigs in the future.

The presence of bubbles in the drilling mud returned at the surface indicated the presence of gas in the mud. The gas was then rerouted through the mud gas separator to a flare where the gas was burned off. What did the size of the flare initially indicate? 

A blowout would occur at any moment.


There was a significant amount of gas in the mud and the well likely became underbalanced.


The pressure of the drilling mud was not enough to keep gas from flowing upwards though the wellbore. 

There was no concern with the size of the flare.


What was the total gas barrel accumulation that the well had gained from the start of the tripping operation? 

157 barrels of gas accumulation


207 barrels of gas accumulation


362 barrels of gas accumulation


True or False: The CSB was not able to fully determine why both the night and day-shift drillers turned the alarm system off. 



Possible reason for turning the alarm system off was that the drillers saw it as a nuisance. Had the alarm system stayed on, the crew would have seen the warning signs. 



Oklahoma Academic Standards
TEKS Standards
College Board Units and Topics
Next Generation Science Standards