Three years ago, a fatal blowout and rig fire at the Pryor Trust gas well in Pittsburg County, Oklahoma, resulted in the death of five workers. The accident occurred during drilling operations, shortly after tripping out of the well. But what have we learned from this disaster?

According to a report published by US Chemical Safety Board (CSB) in 2019, a series of factors contributed to this accident. The cause of the Pryor Trust blowout and 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).

The first technical recommendation of the report read, “establish and convene a group of experts with drilling, engineering, and instrumentation expertise to discuss methods to achieve widespread implementation of automatic safety instrumented systems that could bring a well to a safe state in the event other operational barriers fail”. In other words, the CSB Investigation Team was saying that a form of Automated Well Control system, would help prevent such incidents from occurring.

The CSB report found many failings and there were many occasions where the correct knowledge and procedures could have averted the disaster. The 8 ½” hole was horizontally drilled to 13,435ft MD at which point it was decided to make a bit change. However, from a drilling depth of approx. 13,000 ft MD, gas had started entering the wellbore. The crew decided to continue drilling, whilst simultaneously flaring the gas coming into the wellbore. An RCD (Rotating Control Device) was in place, and the mud returns were routed via the mud gas separator, thereby physically permitting the gas to be flared off and for drilling to continue.  At 13,435ft MD, gas continued to enter the wellbore whilst the well was circulated bottoms up prior to pulling the bit, and gas was similarly flared off at surface. Poor tripping practices and inadequate procedural adherence in a number of areas ensued, and significant quantities of further gas entered the wellbore throughout the trip out. The blowout and subsequent ignition occurred once all the pipe and BHA were out of the hole. The CSB Investigation Team estimated that, prior to the blowout, there had been a net volume of 207 bbls of gas in the wellbore.

How could the Pryor Trust blowout have been avoided?

There were many lessons to be learnt. However, had an Automated Well Control system been used, then the well would have been safely shut in as soon as the flowrate at surface increased due to the gas entering the wellbore, at around the 13000 ft MD depth. At this point the influx could have been circulated out and the mud weight increased to an appropriate level for the remainder of the drilling and for the subsequent tripping operation.

Applying automation in drilling can improve efficiency and eliminate human errors in well operations, thus preventing incidents. By continuously monitoring the well, quickly identifying kicks and reacting accordingly, this technology would have helped prevent the Pryor Trust accident.

Automation has the ability to consistently execute the most reliable solution to ensure safety in upstream operations, supporting management systems in the area of competence assurance. Whether drilling offshore or onshore, the Automated Well Control manages the most significant drilling hazards and is here to stay.  Designed as a tool for the driller, this technology turns every driller into the world’s best performing well control driller and represents a cutting-edge opportunity for those who are willing to embrace it.

Safe Influx has designed over 60 modules using the same Automated Well Control technology to cover all facets of well construction, and beyond. Please contact us at to discuss your requirements.