Properly trained personnel are essential for well control activities. Well control consists of two basic components:
The activities involved in well control are:
Now, let’s take a closer look at these specific activities on the drilling site.
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.
The mud circulatory system consists of the several elements. Let's take a closer look.
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 upon its return to the surface from the hole to the shale shaker, then to the adjacent desander, desilter and degasser back to the mud tank. Mud passes through the suction line, and the mud pump circulates the mud through the discharge line, the stand pipe through the rotary hose and the swivel, 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. A kick is an entry of water, gas, oil, or other formation fluid into the wellbore during drilling. It occurs because the pressure exerted by the column of drilling fluid is not great enough to overcome the pressure exerted by the fluids in the formation drilled. If prompt action is not taken to control the kick, or kill the well, a blowout may occur.
On some rigs there is a mud float level gage which sounds an automatic alarm if the mud exceeds a pre-specified level.
In the well control system installation process, the blowout preventer (BOP), accumulator and choke manifold are installed by the rig crew after the surface casing is set and cemented.
The BOP is one or more valves installed at the wellhead to prevent the escape of pressure either in the annular space between the casing and the drill pipe or in open hole (for example, hole with no drill pipe) during drilling or completion operations.
The accumulator and choke manifold have been set into place during rigging up and now need to be hooked up and tested.
The accumulator is a storage device for nitrogen pressurized hydraulic fluid, which is used in operating the blowout preventers.
The choke manifold is the arrangement of piping and special valves, called chokes, through which drilling mud is circulated when the blowout preventers are closed to control the pressures encountered during a kick.
The BOPs, accumulators, and choke manifold should be regularly tested and properly maintained.
We will discuss the potential hazards and possible solutions in the next tab.
Properly maintain the surface control system.
Here's an interesting Science Channel video on blowout protection and also escape equipment. Learn about outer space, leading scientific exploration, new technology, earth science basics, & more with science videos & news from Science Channel.
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