not that it's likely to ever be an issue again, but how low oil prices go (in the USA) and still be a profitable business, was analyzed. 22.5 dollars a barrel

A handful of shale patches in Texas would be the world’s sixth-largest oil producer, if it were a country, are profitable with crude below $30 a barrel, according to an analysis by Bloomberg Intelligence.

In the Eagle Ford’s DeWitt County, which produced more than 100,000 barrels a day in November, the average well can be profitable with U.S. benchmark crude at $22.52 a barrel