Somewhere I heard/read the price shouldn't drop below $80. The average cost to produce is like $80 nowadays***. In that case the revenue is zero or below zero. Seems not right, but I remember it like that. If the oil-compagnies don't get any revenue, it's alright with me. But there would be consequences of course.
Could the following site give some insight ?
Oil Price History and Analysis
*** I 'm looking to confirm this, but so far didn't find anything