Oil are now lower than at any time since 2009! That's going to cause serious trouble in America's oil patch (not that things are going to be that great for Saudi or Venezuela for that matter. The shift from a few to many (lower oil prices benefit many while high prices benefit the few, is a massive transfer of wealth.
The Saudi royals have been "buying off" their country men with the windfall of expensive energy. Now they have to liquidate their holdings...that could hurt stock prices. In america, nearly 50% of all junk bonds (High Yield bonds) are issued by oil & gas companies drilling expensive shall gas and oil. So far they've been buying time with massive increase in flows, but that cannot keep up.