I'm a moron

A friend came into my work today this is their handiwork.

Where to begin.... I asked my friend something I had been asked by a woman I know. This woman is in her 70's and its fair to say her nose often bothers her about the world. She also seems to think I know the answers!!! Her query in this case was what fills the gap where the oil gets pumped out of? Its not something which had ever occured to me to be honest, we discussed it for a while at the time (not sure why I didn't google from my iphone actually!?!) her thinking was that if nothing replaced the oil would there be a large void which could in theory collapse.

I made the mistake of mentioning this to my friend, who explained all about oil in rocks etc and made me feel like a total muppet.

This is his diagram explaining it all (including his mocking of the oil hole :P He would also like it known that the diagram is not to scale