Unfortunately, given shale wells will continue to produce even...

Unfortunately, given shale wells will continue to produce even when the companies that own them go into adminstration (or get taken over), oil supply is unlikely to fall of a cliff, only ongoing investment. The Saudis might even try to increase supply for a few more months to deliver the killing blow. Last thing they'll want is oil spiking again when creditor renogotiations are happening with banks in the US.
But given the Oct 1 deadline is well known to both private and government players, I don't expect wider market turmoil (I hope) caused by defaults in the shale sector.
Having said that, very happy to be holding DLS for the long-term, just think picking a bottom for oil might be more tricky than the shale crash story - which is very real - might indicate.