Definition - What does Shut Down mean?
Shut Down is the process of closing a well when a wellhead platform experiences one or more warning signs of a blowout. When a well is flowing and there is a sign of a blowout kick, an immediate action is taken to shut down the well. During the shutdown procedure, it should be noted whether the well was flowing small or full flowing as both situations can eventually cause a blowout if not handled properly.
Petropedia explains Shut Down
Well shut down procedure is sometimes referred as shut in process for well control or well shut-off. Blowouts happen more often because of pressure imbalance inside the reservoir such as creation of differential pressure or heaving or sloughing shale, and many times a situation arises that the well starts flowing abnormally. When a producing well is about to experience a well kick, it is always a good and safe wellhead platform practice to shut down the oil well so that the kick influx can be reduced gradually. If this situation is neglected, it may result in loss of human life, infrastructure and fracture in the well casings.