Secondary Well Control

If due to any reason the hydrostatic pressure exerted by drilling fluid column falls below the formation fluid pressure, the formation fluid starts flowing into the wellbore. In such case we say that 'the primary control is lost' and the well has taken a kick. 

What next? 

Once the kick is detected, the Driller should immediately close the well using his company's well control policy. In such cases the well can be closed by closing Blow Our Preventer (BOP).

Thus, 'SECONDARY WELL CONTROL' is defined as the use of BOP and well control procedures to control the kick when the primary well control is lost.

What is Blow-Out?

In the previous blog we discussed about what is kick and its occurrence. Drillers play a major role in detecting and handling the kick. 

As discussed, if the early warning signs of kick is unnoticed by the driller, more and more kick enters the wellbore. As the kick is always lighter than the drilling mud, its presence in wellbore further reduces the bottom hole pressure (BHP) of the wellbore. The further reduction in BHP encourages further flow of kick in the wellbore but now with more strength than before! It rushes into the wellbore with maximum available strength, offloading the mud from the well. The offloading of mud by the kick can be observed on flow line. The volume of mud coming out of well through flow line increases. This increases the percentage of flow out through flow line. The flow-out percent can be read by the driller on his console.