[CliffordK (OP)]

I was listening to NPR today. 
They said that Iran was in a tight spot that they could not just shut down oil wells if the boycott broadens.

A million unsold barrels a day would mean a huge revenue loss for Iran. If Iran has to shut down some of its wells, the oil will settle back into the ground and it could be harder to get it out again.

Any ideas what this means?

It would seem like they would merely shut down the pumps, and stop pumping.  Are they discussing re-injection oil into the wells?  Why?

[evan_au]

Perhaps:
At present the oil pipes are full of oil, and that will continue as long as they keep pumping. As soon as they stop pumping, the oil will start to sink down the pipes, so it will take longer to start flowing.
They often inject water into older wells to improve the flow. If they stop injecting, it may take longer to get the oil flowing later.
Equipment only works smoothly while it is being maintained. If you leave it unmanned for some time, it will need to be repaired before it can be used again.