Objective of this paper is to identify possible crucial circumstances during drilling, workover or associated activities at rigs, where each Safety Critical Well Control Equipment may incapacitate at a time in a demanding situation, which may lead to uncontrolled flow of Well with potentially severe consequence. This paper will present some of likely supervisory failures to visualize scenarios, when the most vital Well Control Equipment such as BOP, Stabbing Valve, Drill Pipe (DP) Spacing-out, and Mud Transfer Pump becomes defunct due to either design limitations, operational or other constraints in uncommon situations during a particular stage of activities at rigs.

While running in MDT (Modular Dynamics Tester) inside a newly drilled deviated gas well, logging tool was stuck in open hole even after reducing mud weight from 14.8 to 14.6 ppg. Consequently, Baker Overshoot through 5 ½ in. DP pipe was being run with wireline cable inside DP to guide and catch the fish by "Cut & Thread" mechanism to strip over wireline cable. However while running in to 13,632 Ft., sever back flow was observed, which was controlled through overbalance by pumping 250 Bbl of one string volume mud followed by 25 Bbl slug and RIH (Running in Hole) was resumed.

However, after running three stands, back flow restarted and although there was continuous flow, RIH of 14 stands were continued to 14,955 Ft. (+/- 61 Ft. from fish). Ultimately, Derrick Man latched last stand in Elevator with logging wire inserted inside DP, then there was severe gushing of mud with oil and gas from DP resting on Slip. The DP open end could not be closed by installing Stabbing Valve as logging wire was inside DP with wire connection over C-Plate above DP, preventing valve from making up in DP box. BOP pipe ram was closed but shear ram failed to cut DP as tool joint was falling in shear ram cavity. Consequently well continued flowing uncontrolled and finally caught fire after few hours. The well was killed next day by pumping high-density (19.2 ppg) mud.

This paper will elaborate overlook by supervisory workforce to envisage the incapacitation of vital safety critical equipment and suggest contingency plan to prevent such situation where one by one all immediate well control measures are compromised.

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