文档介绍：Unit 6 Well Control
Definition
Process and Equipment for kick detection and control
Well control
Well control refers to the control of downhole formation pressures penetrated by the well. There are three distinct well control levels that may occur during drilling operations.
Primary control.
Primary control is given by maintaining the density of the drilling fluid such that hydrostatic pressure at all depths where formations are exposed exceeds formation pore pressures.
Mud hydrostatic pressure>formation pore pressure
Primary control
There are four main reasons, in general, why primary control might be lost during drilling operations:
well penetrates an overpressured zone with a higher formation pressure than mud hydrostatic.
2. A weak downhole formation allows sufficient mud to leave the wellbore so that the level of mud in the annulus drops.
3. Failure to fill the hole properly when pulling out of the hole.
4. Swabbing. If the drillstring is pulled up with sufficient speed, the reduction in pressure at the bottom can be enough to allow formation fluids to enter the well.
Secondary well control
If primary control is lost and formation fluids start to flow in to the well, secondary well control is initiated by closing the BOP to seal off the annulus. As fluid enters the well from the kicking formation, pressure in the well will increase until the total pressure exerted by the mud on the kicking formation equals the formation pore pressure. The pressure exerted by the mud equals mud hydrostatic pressure + surface pressure held by the BOP.
Mud hydrostatic pressure + surface pressure = formation pore pressure.
The objective now is to restore primary control. This is achieved by circulating mud of higher density into the well so that mud hydrostatic pressure again exceeds formation pore pressure without any pressure held on surface by the BOP.
Tertiary control
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