At the time of the accident, the well of the Yamburg gas field where the outburst occurred was at the completion stage following the performed hydraulic fracturing. The depth of the well was 13,800 ft., formation pressure was 8,920 psi, formation temperature was 97.7°С, wellhead backpressure was 7,194 psi, anomaly ratio was 1.6. There were the tubing string with packer and circulation valve in the wellbore. The wellhead was equipped with a dual blowout preventer PPR-2x185x70 and a hydraulic fracturing unit, including an adapter flange 180x70– 65x70, an adapter spool 65x70-BRS-3”, three high-pressure plug valves and a crossmember. The wellhead equipment had been tested at 7,905 psi. The wellbore had been perforated in 12,480–12,520 ft. interval with a shaped charge DW8g TTG Linr St RDx d = 1.654” with the perforating density of 7 spf (with the total of 540 perforations). The testing resulted in oil inflow and the well was characterized with pulsating flow with the average daily flow rate of 30.2 BPD. The wellhead conditions during 0.1575 ft. flowback through the tubing string were the following: the pressure of 87/464 psi, the temperature of 2 °С...