Most living things are not equipped with a shut-off valves. Such as the human body and the like, and if so, as to my knowledge man can mimic the condition. The sea, the earth and the air we breath have no limits. There is no natural shut off valve in their make up.
With that being said, OIL rigs are designed and operated by man. I was under the impression that any kind of machinery of that nature (Man Made) had to have an On and OFF valve within it's mechanism in order to pass inspection and to test it. I would think that as each unit was put in place it would not have been set at full throttle or whatever it was going to connected was closed off. Can they really connect a new pipeline or rig with the Oil gushing out. I would think not, well maybe...
Where is the ON and OFF valves which should be mandatory and created for emergencies such as
Every man made and installed mechanical device we use has to have an On and OFF switch or it is classified unfit for consumer use.