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Drilling >> Well Control

Jun 30, 2017

Properly trained personnel are essential for well control activities. Well control consists of two basic components: an active component consisting of drilling fluid pressure monitoring activities, and a passive component consisting of the Blowout Preventers (BOPs).

The first line of defense in well control is to have sufficient drilling fluid pressure in the well hole. During drilling, underground fluids such as gas, water, or oil under pressure (the formation pressure) opposes the drilling fluid pressure (mud pressure). If the formation pressure is greater than the mud pressure, there is the possibility of a blowout.

Schematic of the circulating system: The drill bit, drill collar, annulus, drill pipe, kelly and swivel are depicted in the upper right. Drilling mud flows through the mud return line (center) upon its return to the surface from the hole to the shale shaker (upper left), then to the adjacent desander, desilter and degasser back to the mud tank (upper left). Mud passes through the suction line, and the mud pump (center) circulates the mud through the discharge line (above), the stand pipe (upper right) through the rotary hose (right) and the swivel (lower right), back to the kelly and into the drill pipe.
Each part of this system must function and be in good repair to maintain well control.
If the mud level increases, it may be a sign that a kick is in progress.On some rigs there is a mud float level gage which sounds an automatic alarm if the mud exceeds a pre-specified level.

Kick illustration: Schematic of mud circulating system, with a close up view of the drill bit hitting the lower vein at unexpected higher pressure. KICK occurring. Mud pit fills. Shut-in well. Above the animation is the illustration of the mud return from the surface to the mud pit through the circulating system.

The blowout preventer (BOP), accumulator and choke manifold are installed by the rig crew after the surface casing is set and cemented. The accumulator and choke manifold have been set into place during rigging up and now need to be hooked up and tested. The choke line valve is used to redirect the mud from the well bore to the choke manifold during a kick. The kill line valve is used to direct drilling fluid to the BOP during a kick.

The BOPs, accumulators, and choke manifold should be tested and properly maintained.Properly maintain the surface control system.